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From soil to leaves – Aluminum fractionation by single step extraction procedures in polluted and protected areas
Journal of Environmental Management 127 (2013) 1e9
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From soil to leaves e Aluminum fractionation by single step extraction procedures in polluted and protected areas Marcin Frankowski*, Anetta Zio1a-Frankowska, Jerzy Siepak , Umultowska 89b, 61-614 Poznan , Poland Department of Water and Soil Analysis, Faculty of Chemistry, Adam Mickiewicz University in Poznan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 November 2012 Received in revised form 26 March 2013 Accepted 11 April 2013 Available online 4 May 2013
The paper presents the fractionation of aluminum in the samples of soil and plants of different species using a selective single-step extraction method. The study was conducted in the area located near a chemical plant, which for many years served as a post-crystallization leachate disposal site storing chemical waste (sector I), and in the area around the site: in Wielkopolski National Park, Rogalin Landscape Park and toward the infiltration ponds at the “De˛ bina” groundwater well-field for the city of (Poland) (sector II). The results of aluminum fractionation in samples of soil, leaves and plants Poznan showed heavy pollution with aluminum, especially in the water soluble aluminum fraction e Alsw (maximum concentration of aluminum in soil extract was 234.8 4.8 mg kg1, in the leaves of Betula pendula it was 107.4 1.8 mg kg1 and in the plants of Artemisia vulgaris (root) and Medicago sativa (leaves) it amounted to 464.7 10.7 mg kg-1and 146.8 1.2 mg kg1 respectively). In addition, the paper presents the problem of organic aluminum fractionation in biological samples and it shows the relationship between aluminum concentration in soil and the analysed woody and herbaceous species. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Aluminium Fractionation Single-step extraction Soil Plants
1. Introduction A single-step extraction procedure using an appropriate extractant allows for the separation of one fraction characterized by particular properties. Such a procedure enables the qualitative and quantitative determination of soluble metal fractions, as well as easily exchangeable ones, which in consequence become available for plants, animals and people. The single-step extraction procedure has been used to fractionate aluminum in agricultural soils (Takeda et al., 2006), forest soils (Zhu et al., 2004), flood plain soils (Drabek et al., 2005), road sediments, lake sediments (Agemian and Chau, 1976; Sutherland et al., 2001, 2004; Sutherland, 2002), sedimentary rocks, soils from mining areas (Matús et al., 2004, 2005, 2006; Kubova et al., 2005) and soils from areas polluted with aluminum (Frankowski et al., 2010; Frankowski and Zio1aFrankowska, 2010). In the case of aluminum and other elements including heavy metals or metalloids, the most frequently used single-step extraction methods include the deionized water method (water soluble fraction e Alsw). This approach is characteristic of the element fraction which may be dissolved to form a solution in the environment. Despite their low toxicity, the
* Corresponding author. Tel.: þ48 502305156. E-mail address: [email protected] (M. Frankowski). 0301-4797/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvman.2013.04.033
exchangeable aluminum fraction and organic fractions provide substantial information about the condition of the natural environment. It is possible to determine different aluminum fractions in solid samples depending on the extractant used. Aluminum extracted by NH4Cl or KCl is exchangeable (Alex) (Alvarez et al., 2002; Walna et al., 2005). In turn, when extracted by 0.2 M ammonium oxalate, it is an estimate of total non-crystalline Al, which can selectively dissolve aluminum in poorly ordered soil including aluminum bound to organic matter (Alvarez et al., 2002; Fernández-Sanjurjo et al., 1998). Extraction by 0.5 M CuCl2 allows for the determination of aluminum forming low- and mediumstability complexes with organic matter (Alvarez et al., 2002) and it also promotes the depolymerization of OHeAl polymers (Hargrove and Thomas, 1981). Sodium pyrophosphate used as a reagent is considered to determine all forms of organically bound aluminum (total organically bound Al). This fraction, like exchangeable Al, is considered to be potentially highly reactive. It should be stressed that during the extraction of organic forms, some amounts of inorganic Al, especially in the poorly ordered or non-crystalline phase, can also be extracted (Brandtberg and Simonsson, 2003). The next extractant used in the single-step extraction procedure is dithionite-citrate buffer (DCB) which represents all free Al compounds (AlDCB) (Matzner and Prenzel, 1992). Other aluminum forms are determined by calculating the differences in the concentration of certain aluminum fractions.
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It is well known that the acid deposition leads to the substantial increases of the dissolved Al concentrations in the acidified soils and surface waters. Besides the continuing acidification of soils with the low buffering capacity leads to an increase of the aluminum mobilization in the environment and can to release potentially toxic aluminum species into the soil solution and surface water (Fernández-Sanjurjo et al., 1998; Matús et al., 2009; Walna et al., 2005). The toxicity and bioavailability of aluminum is dependent on its distribution among the various forms or species coexisting in the environment. The free Al3þ, AlOH2þ, and AlðOHÞþ 2 species were found to be the most crucial to evaluate its toxicity and to predict the impact of the proton inputs in the soils and surface waters (Matús et al., 2009; Darko et al., 2004). The other complexes with aluminum including soluble organo-Al and fluoride-Al, sulfate-Al complexes are less phytotoxic (Álvarez et al., 2005). The main symptom of toxicity effect of aluminum is the dramatic inhibition of root growth, which occurs within minutes of exposure to Al, even at micromolar concentrations (Ille_ s et al., 2006; Tolrà et al., 2011; Morita et al., 2011). It can be stated, that aluminum toxicity is one of the main factors limiting plant growth in acid soil (about 40% of the world’s arable lands) (Rout et al., 2001; Rezaee et al., 2013; Kovácik et al., 2012). In sum the form of soil of Al is a key factor of its potential risk impact not only to the plants and also to the living organisms. That is why the information about aluminum forms which are more or less readily released into the solution is important and can be achieved by the extraction of fraction of the aluminum by chemical reagents. The main aims of this work were: (1) to determine the environmental pollution in the area of post-crystallization leachate disposal site, (2) to determine the variability and occurrence of aluminum in soil using single step extraction procedures, (3) to apply single step extraction procedures to fractionate aluminum in leaf and plant samples, (4) to compare the concentration of aluminum in soil with the concentration of aluminum in the leaves of various tree species.
2. Materials and methods The “LUVENA” S.A. chemical plant is located in the south , 2.5 km south of the artificial eastern part of the town of Lubon (Poland). The plant takes up recharge well-field “De˛ bina” of Poznan the area of about 59 ha. To the north of the chemical plant, there are industrial grounds and afforested areas spreading across the meanders of the Warta River. To the south, there is an aggregate mine, and in the distance of about 0.7 km runs the border of Wielkopolski National Park. The southern border of the described area is the Warta River, while the western border are the old river beds of the Warta River, separated from the main stream of the river but still filled with water. In the distance of about 200 m to the southewest of the chemical plant there is a post-crystallization leachate disposal site. The post-production disposal facility is a dammed-up underground tank with a built-up superstructure, which does not contain any additional safety devices to reduce the migration of pollutants to the water-bearing layer. It takes up the area of about 2 ha and its removal began in the year 2005. The chemical plant has been producing aluminum fluoride since 1971. Post-crystallization leachate generated in the production process has been collected at the post-crystallization leachate disposal site in the form of semifluid pulp. In the 1980s, such chemicals as superphosphate, hydrofluoric acid, aluminum fluoride, potassium fluoroborate and vanadium catalyst were also produced here. The soil and leaf samples were collected for analysis in June 2010. In order to determine spatial variability, the study area was divided into two zones:
Zone 1 (sector I) e the area situated at the chemical plant in , with the post-crystallization leachate disposal site Lubon (samples 1e5) e point source of pollution. Zone 2 (sector 2) e area of Wielkopolski National Park, Rogalin Landscape Park, outside the area of the point source of pollution (samples 6e15) toward the infiltration ponds of the “Debina” (Poland). groundwater well-field for the city of Poznan At each sampling point, soil and leaf samples of predominant tree species were collected. In sector 1, at points 1e4, the samples of Betula Pendula were collected, while at point 5 the leaves of Robinia pseudoacacia were taken for analysis. Furthermore, within the sector comprising points 1e5 (in the area of point 5), in the revitalized area, the samples of the following plants were collected: Medicago sativa, Melilotus albus, Artemisia vulgaris, Melilotus officinalis, Holcus lanatus. In sector II, leaf samples of the following predominant tree species were collected: Betula pendula (points 8,9,15), Robinia pseduoacacia (points 9, 10, 11, 14), Tilia platyphylos (point 7) and Salix alba (points 6, 10, 12, 13) (Fig. 1).. The soil samples were collected for analysis at the depth of 0e 20 cm, while the leaf samples were taken at the height of 120 cm above ground level. Herbaceous plants were collected up to 60 cm above ground level. The samples were dried at room temperature. Hygroscopic water and substances dissolved in it were treated as an integral component of the sample. After drying, a soil sample was passed through sieves with mesh sizes of 2.0, 1.0, 0.5, 0.25, 0.1, and 0.063 mm, in accordance with the Polish Norms: PN-ISO 565:2000 and PN-ISO 3310-1:2000, using a LAB-11-200/UP sieve shaker (EKO-LAB, Brzesko, Poland). The grain size fraction of 0.1e0.25 mm was predominant and it was used to prepare soil extracts. Leaf samples were ground and stored in PP bags until the extraction and mineralization were performed. The samples were then extracted in order to separate the aluminum fractions: - soil water fraction (Alsw) e extracted by deionized water - exchangeable Al fraction (Alex) e extracted by 1 M NH4Cl - low- and medium-stability complexes of Al with organic matter (Alcu) e extracted by 0.5 M CuCl2 - total organically bound Al (Alp) e extracted by 0.1 M Na2P4O7 - total non-crystalline Al (Alo) e extracted by 0.2 M C2H8N2O4 - weakly bound complexes of Al with organic matter (Alcu-Alex) e calculated - high-stability complexes with organic matter (Alp-Alcu) e calculated - inorganic non-crystalline Al (Alo-Alp) e calculated - pseudo total aluminum occluded on the grain (Alptc) e EPA 3051 (in the case of plants: Altc means total concentration of aluminum e full mineralization. - Concentration ratio: it is the Altc/Alo ratio used as a factor of availability of inorganic and organic fraction of aluminum (calculated based on results for particular fraction presented in Table 1). The extraction was conducted at the temperature of 25 C using a magnetic mixer. The extracts were prepared in proportion 1:10 (v/ v) for the predominant fraction in a 100 g sample with 0.1e 0.25 mm grain size. For the soil water extract fraction of aluminum, the sample pH was determined. Furthermore, the samples were mineralized using the EPA 3051 method (EPA, USA) in order to separate the pseudo total content of aluminum. The pH (H2O) was determined using the Orion 5-star Plus (Thermo, USA) meter with a Single Pore pH electrode (Hamilton, USA). The determination of aluminum was performed in 3 replications, and the % RSD did not exceed 5%. Aluminum was determined using the Shimadzu AA7000
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
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Table 1 Results of pH and aluminum concentration for all separated fractions of aluminum in soil and leaves samples of different tree and plant species. GPS map point
Sample type
pH (H2O)
Alsw
Alex
Alcu
Alp
Alo
Alcu-Alex
Alp-Alcu
Alo-Alp
Alptc (Altc)
1 1 2 2 3 3 4 4 5 5 5 5 5 5 5 5 5 5 6 6 7 7 8 8 9 9 9 10 10 10 11 11 12 12 13 13 14 14 15 15
Soil Betula pendula Soil Betula pendula Soil Betula pendula Soil Betula pendula Soil Robinia pseudoacacia Medicago sativa (flower) Medicago sativa (leaves) Melilotus albus (leaves) Artemisia vulgaris (leaves) Artemisia vulgaris (root) Melilotus officinalis (leaves) Holcus lanatus (leaves) Holcus lanatus (flower) Soil Salix Alba Soil Tilia platyphyllos Soil Betula pendula Soil Robinia pseudoacacia Betula pendula Soil Robinia pseudoacacia Salix Alba Soil Robinia pseudoacacia Soil Salix Alba Soil Salix Alba Soil Robinia pseudoacacia Soil Betula pendula
5.37 5.52 3.97 5.12 5.04 5.89 3.81 5.65 3.83 6.42 6.44 6.08 6.04 6.37 4.79 5.46 5.37 5.85 4.91 5.64 5.06 5.62 4.89 5.78 6.19 6.41 5.49 6.46 6.35 6.43 7.34 6.13 4.74 5.62 4.73 5.71 4.52 6.23 4.73 5.82
32.79 8.21 331.7 35.1 77.93 31.3 34.83 107.6 234.8 5.4 17.43 146.75 56.73 8.47 464.70 69.23 99.88 39.66 1.99 5.53 2.07 5.77 1.49 6.97 0.41 4.68 6.25 0.99 1.21 0.61 0.99 2.76 6.46 3.01 5.97 0.84 5.17 1.68 6.56 3.37
13.95 8.51 585.7 62.5 6.45 30.5 57.54 107.5 557.6 4.5 27.88 160.2 57.57 30.83 556.1 96.99 128.3 48.56 3.88 6.48 4.39 6.92 45.01 8.95 1.49 6.99 6.69 1.29 1.48 1.11 1.29 3.32 7.96 3.13 2.85 3.24 46.85 6.97 62.39 9.49
387.9 13.51 1158 72.1 382.9 36.21 339.1 169.5 922.7 8.17 28.97 286.78 85.57 276.6 1466 161.3 325.6 90.38 76.08 38.22 70.31 13.11 137.5 22.84 30.89 11.17 12.74 44.59 11.54 12.14 49.52 14.54 60.69 17.91 84.25 13.46 100.4 11.11 200.6 23.68
441.2 17.5 1334 78.6 432.1 53.5 405.1 210.5 984.6 13.22 15.14 106.8 36.92 279.4 1195 32.69 208.2 39.34 248.8 1.69 93.62 6.36 316.3 8.56 35.69 0.062 0.099 51.69 0.794 0.198 53.84 0.595 85.46 4.372 100.1 5.07 147.8 1.99 266.3 6.46
522.6 43.22 1566 156.5 434.4 57.24 427.8 229.5 1375 18.51 58.91 252.6 79.23 284.5 1954 162.4 317.2 99.85 252.9 6.76 111.3 20.88 329.8 25.92 36.53 3.68 5.89 61.35 1.88 3.68 60.85 2.48 87.98 7.56 111.1 12.25 192.2 2.68 268.9 13.76
373.95 5.00 572.3 9.6 376.45 5.71 281.56 62 365.1 3.67 1.09 126.58 28 245.77 909.9 64.31 197.3 41.82 72.2 31.74 65.92 6.19 92.49 13.89 29.4 4.18 6.05 43.3 10.06 11.03 48.23 11.22 52.73 14.78 81.4 10.22 53.55 4.14 138.2 14.19
53.3 4.00 176 6.5 49.2 17.29 66 41 61.9 5.05
81.4 25.72 232 77.9 2.3 3.74 22.7 19 390.4 5.29 43.77 145.8 42.31 5.1 759 129.71 109 60.51 4.1 5.07 17.68 14.52 13.5 17.36 0.84 3.618 5.791 9.66 1.086 3.482 7.01 1.885 2.52 3.188 11 7.18 44.4 0.69 2.6 7.3
1054 56.4 3634 161.1 1237 116.6 1257 407.1 2678 43.32 73.6 404.6 98.84 595.21 2969 181.2 418.8 565.4 1392 43.2 1436 36.81 1082 54.95 835.4 14.96 20.22 1623 19.27 17.41 990.2 18.29 615.1 34.24 1145 49.98 773.6 14.22 1007 37.14
a
a a a
2.8 a a a a
172.72 a
23.31 a
178.8 a
4.8 a a
7.1 a a
4.32 a
24.77 a
15.85 a
47.4 a
65.7 a
Negative subtraction Alp-Alcu, Alptc (pseudo total content for soil samples), Altc (total content for leaves and plant samples), n ¼ 3, RSD<5%.
spectrometer (Shimadzu, Japan). In order to check the reliability of FAAS measurement certified reference materials were used: for soil SRM 2709 and for leaves SRM 1515 (National Institute of Standards and Technology, USA). These reference materials: SRM 2709 and SRM 1515 were analysed in six repetitions. The results obtained for the certified reference materials have been presented in Table 1. Recoveries of both SRM materials were 99.8% for soil and 98.7% for leaves. 3. Results The results of pH value and aluminum concentrations for all separated fractions of aluminum in soil and leaf samples of different tree and plant species were presented in Table 1. 3.1. Soil The concentration of particular aluminum fractions: soil water extract fraction (Alsw), exchangeable Al fraction (Alex), low- and medium-stability complexes of Al with organic matter (Alcu), total organically bound Al (Alp), total non-crystalline Al (Alo), weakly bound complexes of Al with organic matter (Alcu-Alex), highstability complexes with organic matter (Alp-Alcu), inorganic non-crystalline Al (Alo-Alp) and pseudo-total content of aluminum (Alptc) for all the analysed soil samples were determined. In order to determine the variability and potential availability of aluminum,
it was assumed that fraction Alptc would be treated as the pseudototal concentration of aluminum, and namely as the fraction of aluminum which does not impair the structure of aluminosilicates (non-crystalline and partially crystalline aluminum). Based on the above assumption, the water soluble fraction of aluminum (Alsw) constituted 2.8e9.1% of the study area in sector I, which is 9.1% and 8.8%, respectively, for points 2 and 5. Such a large contribution of this fraction was caused by the availability of post-crystallization leachate, as points 2 and 5 were located directly in the area of the former disposal facility. As regards the remaining sampling points in sector I, a significantly smaller contribution of water soluble aluminum fraction was found owing to the lack of direct influence of the post-production disposal facility. For sector II, comprising the remaining sample collection points (samples 6e15), the level of aluminum availability in the water soluble fraction did not exceed 1.1%, and the mean value of this fraction was 0.4%. A similar variability trend was observed for Alex, although the aluminum concentration in this fraction was about twice as high as the concentration of water soluble aluminum fraction for samples 2, 4 and 5. The percentage contribution of Alex in comparison with fraction Alptc in sector I ranged between 0.5% and 20.8%. For samples collected in sector II, the aluminum concentration (Alex) is about twice as high, with the exception of samples 8, 14 and 15, for which the values of 4.1%, 6.1% and 6.2% were determined respectively, which is a significant increase in concentration compared with Alsw. In the case of organic aluminum and its fractions: Alcu,
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Alp, Alcu-Alex and Alp-Alcu, a variability trend similar to that of fractions Alsw and Alex was observed. The total organic aluminum found ranged from 405.1 to 1334 mg kg1 (32.2%e41.9%) in sector I and from 35.69 to 316.3 mg kg1 (3.2%e29.2%) in sector II. Only in sample 8 a much higher concentration of organic aluminum (316.3 mg kg1) was determined. However, with the exception of sample 8, maximum concentration of organic aluminum for sector II was 266.3 mg kg1 (26.4%). Based on the obtained study results, it should be underlined that the fractions of organic aluminum: Alcu, Alp, Alcu-Alex and Alp-Alcu did not fully reflect the conditions necessary to break the bond with organic matter. This particularly related to the calculated aluminum fractions (Alcu-Alex and AlpAlcu), as Alcu-Alex concerned weakly bound Al, and the result of Alp-Alcu calculation was high-stability Al bound to organic matter. Should it therefore be assumed that aluminum bound to organic matter is a fraction of exchangeable aluminum? Similarly, drawing a comparison between fractions Alcu and Alp, it should be stated that these results are often similar, and Alcu (low- and medium-stability fraction) does not fully meet the extraction conditions necessary for breaking the AleOM bond. Therefore, it seems justified to use Na2P4O7 as the only reagent in the extraction of total organic aluminum. It should also be stressed that the extraction conditions of the organic fraction are strong enough to enable the extraction of both fraction Alsw and fraction Alex. Aluminum concentration in the total non-crystalline fraction (Alo) for sector I was 34%e51.3% (405.1e1334 mg kg1), while for sector II it amounted to 3.78e30.5% (35.69e316.3 mg kg1). The variability trend depending on the place of sample collection was similar to that observed for the previously discussed aluminum fractions. 3.2. Plants In sector I, soil and leaf samples of B. pendula (points 1e4) and R. pseudoacacia (point 5) were taken for analysis. In sector II, leaf samples of the following predominant tree species were collected: B. pendula, R. pseduoacacia, T. platyphylos and S. alba (see Table 1). The highest concentration of aluminum for all the analysed fractions was determined in sample 4 (sector I). Aluminum concentration was also highest in samples from sector I (samples 1e5), while in sector II it reached a similar level of concentration for particular tree species. Based on the study results, it was observed that the lowest concentrations were determined for R. pseudoacacia leaf samples (both in sector I and II). No significant differences in the obtained results of aluminum concentration were found for B. pendula, Salix Alba and T. pytophylos. Taking into account aluminum concentration in particular fractions of plant sample extracts, the similarity in the obtained results between fractions Alsw and Alex was observed. No influence of pH reaction on the level of aluminum concentration in the pH range of 5.12e6.43 for the whole set of samples in sectors I and II was found. However, it should be stressed that in comparison with Altc, the aluminum concentration in fraction Alsw was relatively high and it ranged from 12.5 to 46.8% for sector I and from 1.7 to 31.3% for sector II. The presence of such high concentrations in fraction Alsw was connected with the possibility to extract the whole sample, and not only its surface. In the case of organic aluminum forms, no similarity between particular organic aluminum fractions was found. Such similarities, however, were observed for soil samples. For 12 out of 17 analysed samples (and for all the 12 samples from sector II), a negative result of calculation between Alp and Alcu was found (high-stability complexes with organic matter, from 6.75 to 36.53 mg kg1). This might have been caused by another type of aluminum bond with organic matter, which resulted in higher or similar concentrations for fraction Alcu. It might have also been
linked to the presence of aluminum in the form of other complexes, not only the ones with fluorides, which were predominant in this sector (Frankowski et al., 2010; Frankowski and Zio1a-Frankowska, 2010). Therefore, the conclusion can be drawn that aluminum does not form stable complexes with OM in the case of unpolluted soil. This concerns the possible absorption of aluminum by plants through their root system, or the element is transformed as a result of the occurrence of other competitive ligands which can form more stable complexes with aluminum, such as inorganic complexes. In the case of samples from sector I, the predominant aluminum fraction was Alo, while for sector II, the Alcu fraction of organic aluminum extracted by copper chloride (II) prevailed. The Altc-to-Alo concentration ratio ranged between 1.03 for sample 2 and 10.25 for sample 10. It is worth noting that the Altc-to-Alo ratio was lowest for sector I (the mean ratio ¼ 1.8), while for sector II, the mean ratio was 4.8, which suggests an entirely different nature of these samples in terms of aluminum availability in the inorganic and organic non-crystalline form, as well as in aluminum extracted by 0.2 M C2H8N2O4. 3.3. Plant extracts from sector I Within the studies conducted in sector I concerning determinations of aluminum and its fractions in soil and tree leaves, samples of plants used to revitalize the post-crystallization disposal site were collected. In order to define the occurrence variability of a given aluminum fraction depending on the plant species, and in order to define the direct impact of aluminum on the soil where the plants grew, the following plant samples (and their above-ground plant parts) were analysed: A. vulgaris (leaves), A. vulgaris (root), H. lanatus (leaves), H. lanatus (flower), M. sativa (flower), M. sativa (leaves), M. albus (leaves), M. officinalis (leaves). The highest concentration was determined in the root of A. vulgaris, which resulted from the accumulation of aluminum in this morphological part of the plant. The fractionation of aluminum directly in the root sample revealed significant contribution of forms Alsw and Alex amounting to 464.7 and 556.1 mg kg1 of aluminum respectively. This contribution was larger compared to Altc, amounting to 2976 mg kg1, which constituted 15.7 and 18.7% of this fraction contribution respectively. This suggests the aluminum availability at pH ¼ 4.67 in the form of inorganic aluminum complexes, regardless of the fact that the contribution of inorganic noncrystalline aluminum fraction amounted to only 0.9%. In the case of H. lanatus and M. sativa flower samples, the contribution of aluminum in particular fractions was definitely lower compared with the results obtained for A. vulgaris root samples. However, significant differences were observed in the determined aluminum concentrations and in the contribution of particular fractions for the analysed flower samples of both plant species, which might be the effect of using different mechanisms to absorb aluminum from soil. The analysis of total concentration of aluminum (Altc) in the flowers of H. lanatus and M. sativa in relation to particular aluminum fractions with a similar pH of water extract samples (5.85 and 6.44 respectively) revealed that the flowers of H. lanatus might contain aluminum strongly bound in the flower’s structure and not easily extracted using an extractant, regardless of the fact that aluminum concentrations for particular fractions were two times higher than in the case of M. sativa. Individual features determine aluminum accumulation in a plant depending on the species resistance. It should be emphasized that the analysed samples of H. lanatus and M. sativa flowers differ significantly in their structure, but the total aluminum content (Altc) in their leaves is similar and amounts to 418.8 and 404.6 mg kg1 respectively for H. lanatus and M. sativa. In case of the other analysed plant species e M. Albus and M. Officinalis e lower total concentrations of
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
aluminum (Altc) were determined, amounting to 98.84 and 181.2 mg kg1. Alternatively, in the leaves of A. vulgaris, the highest concentration of total aluminum was found, amounting to 595.2 mg kg1. Moreover, for this plant species the lowest concentration of aluminum fractions Alsw and Alex (where the % contribution in relation to total aluminum concentration was 1.4 and 5.2 respectively) and the highest Alp and Alo concentrations (47.0 and 47.8%) were determined, which might be linked to the accumulation of aluminum and blocking its transportation from the root to other parts of the plant (this also results from the different structure of the plant and larger leaf surface). It is interesting that high concentrations and the contribution of the soilewater (57.4% for M. albus and 38.2 for M. officinalis) and exchangeable (58.2% for M. albus and 53.5% for M. officinalis) fractions suggest high availability of aluminum, which might pose a threat to the natural environment in the studied area. 3.4. Influence of pH (aluminum soil water fraction) The relationship of soil and leaf samples depending on the place of sample collection (sector I and sector II) was conducted (Fig. 2). The analysis of Alsw fraction did not reveal the concentration variability of this aluminum form in the function of pH reaction for sector II. This may be caused by a different type of aluminum bond and the contribution of other exchangeable ions in the environment of a well-formed soil structure. For sector I, significant contribution of aluminum at lower reaction values (pH < 4.0) in soil samples was observed, which is the effect of aluminum availability in the form in which it entered soil in sector I (post-crystallization leachate disposal site). For the other soil and leaf samples in sector I, higher concentrations of Alsw at lower pH were observed. 3.5. Soileplants relationship In order to analyse aluminum migration from soil to tree leaves, percentage graphs were made for the following aluminum fractions: Alsw, Alex, and Alptc (Altc), for all soil and tree leaf samples (Fig. 3). Based on the results obtained for the soil water fraction
5
(Alsw) of leaf samples of different tree species and soil samples, a relation between sample collection sites and Alsw concentration was observed in both sectors. The samples collected from sector II are especially noteworthy as the concentration of Alsw in soil was higher for the samples (samples 12e15) taken on the right bank of the River Warta. In turn, the concentration of Alsw was higher in the leaf samples (samples 6e11) collected from the left-bank section of the River Warta. For sector I, the concentration of Alsw determined in soil was significantly higher than the concentration in leaves, which resulted from soil pollution. Only in the case of sample 4, higher concentration of aluminum in fraction Alsw of leaves was determined. This difference was caused by the fact that sample 4 was situated outside the area of direct influence of waste disposed at the disposal site. It is noteworthy that the leaf samples of B. pendula (samples 1e4) reached higher concentration values than the leaf samples of R. pseudoacacia (sample 5). In the case of Alex, a variability trend similar to the case of fraction Alsw can be observed. Significant changes were only found for sample 3 in sector I (higher degree of aluminum extraction from plant samples). On the other hand, for sector II, the soil-to-leaves ratio of Alex was higher for samples 8 and 9 and lower for sample 12 in comparison with the results obtained for fraction Alsw. These results, however, do not suggest significant differences between fractions Alsw and Alex (Fig. 4). In the case of aluminum fraction regarded as pseudo-total concentration, over 80% of aluminum bound in soil was observed for all the samples with the exception of sample 4. However, it should be stressed that the aluminum contribution in this fraction was difficult to obtain for plants and it did not constitute the source of assimilable aluminum in the environment. In the case of soil and leaf samples collected from both sectors, the relationship resulting from the possibility to absorb aluminum by the studied tree leaves was observed. A lower soil-to-leaves concentration ratio was observed for R. pseudoacacia (samples 5, 10, 11, 14) and for S. alba (samples 6, 12, 13) in comparison with the samples of B. pendula, where aluminum concentration in the analysed leaf samples was higher both in sector I and sector II (Fig. 5).
Fig. 1. Location of the sampling points.
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Fig. 2. Relationship of soil and leave samples depending on the place of sample collection and reaction value (sector I vs. sector II).
also the organic fraction where different mechanisms of aluminum extraction from the matrix with high content of organic matter were observed. In the work by Kubova et al. (2005), a number of single-step extractions in the soil and plant samples from the sites affected by mining activities were conducted in order to separate different aluminum forms. It should be underlined that the areas of mining activities were rich in minerals containing aluminum and low pH values. The concentration of aluminum in acidified soil samples after extraction by H2O and NH4Cl was 50e250 mg kg1 and 100e 800 mg kg1 respectively. For the comparison the concentration of Alsw and Alex fractions for soil samples collected in the area of post-
4. Discussion The studies of aluminum fractionation using single-step extraction of soil, leaf and plant samples suggest the necessity to discuss the issue of aluminum availability, the issue which has to date concerned the studies of soil samples most frequently originating from the areas highly acidified as a result of dry and wet deposition processes (Drabek et al., 2005; Álvarez et al., 2002; Walna et al., 2005; Zo1otojakin et al. 2011). That is why, the conducted research were designed to showing the significance and necessity of aluminum fractionation in the plant material, especially the fraction Alsw and Alex which are the most mobile and
leaves soil Ratio Alsw in soil vs. Alsw in leaves samples in %
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sample Fig. 3. Occurrence of aluminum in soil and leave samples in [%] for the soil water extract fraction (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
leaves soil
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Ratio Alex in soil vs. Alex in leaves samples in %
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Fig. 4. Occurrence of aluminum in soil and leave samples in [%] for the exchangeable fraction of aluminum (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
In the case of extraction by C2H8N2O4 (fraction Alo), which can dissolve the free amorphous or crystalline Fe, Al oxides and silicate minerals by reduction and complexation reactions, Kubova et al. (2005) obtained the concentration of aluminum in ranging from 400 to 1160 mg kg1 (0.75e2.2% of total soil Al). In the soils under these study from sector I, the concentration of Alo fraction extracted by the ammonium oxalate was similar (429e 1566 mg kg1), but the contribution of this fraction according to the total soil Al was much higher and amounted to 34e51.3%, which might have resulted from soil samples specification. As can be seen on both type of analysed soil samples (from mining area and
crystallization leachate disposal site (sector I) with also low pH values, amounted to 33e332 mg kg1 and 14e586 mg kg1 properly. It is worth noting that concentration of exchangeable aluminum in soil ranging 90 mg kg1 is considered as a critical value which is associated with visible damage to plants and trees or even their dieback (Walna et al., 2005). In the sample No.2 and No.5 situated in the middle of post-crystallization leachate disposal site (sector I) the high concentrations of exchangeable aluminum (over 550 mg kg1) were associated with low pH values of the soil. The same relationship has been established by Walna et al. (2005) and Zo1otajkin et al. (2011) for samples of forest soils.
leaves soil
Ratio Alptc in soil vs. Altc in leaves samples in %
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sample Fig. 5. Occurrence of aluminum in soil and leave samples in [%] for the pseudototal (Alptc) and total concentration of aluminum (Altc) (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
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M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
chemical plant e sector I) the released amount of Al was relevant and was dependent on the efficiency of the extraction agents. Matús et al. (2006) in the soil samples collected from the open quartize mine area influenced by acid mine solutions, determined various forms of aluminum using single step extraction procedure including the total organically bound aluminum fraction (Alp) by 0.1 M Na2P4O7 reagent. The obtained concentration of Alp fraction ranged from 200 to 3600 mg kg1 which was consist 0.2e4.2% of total soil Al and was the high concentration of Al in soil extracts. In our study in the samples from the polluted area (sector I) the marked concentrations of Alp fraction were lower (405e 1334 mg kg1), but the obtained contribution of these fraction into the total soil Al was much higher (32e42%). In the study by Matús et al. (2006) the high aluminum concentrations which they obtained in extracts using 0.1 M Na2P4O7 (Alp fraction) they associated with the complexation ability of the used agent to impair the structures of clay minerals or weathered secondary minerals. Considering the fact that the samples from a mining area, contained minerals from the aluminosilicate group, it seems highly unlikely that Na2P4O7 reagent was able to impair the aluminosilicate structures. It is well know that, pyrophosphate as a preferred reagent in the extraction of total aluminum formed aluminum complexes from the surface of mineral grains and sometimes from the interlayer spaces of clay minerals to organic matter forms (Walna et al., 2005). According to the other simple salt extractants used by Matús et al. (2006) they found that the efficiencies of the KCl, NH4Cl, BaCl2, CuCl2 and LaCl3 extractants with the concentrations from 0.1 to 1 mol l1 were very similar (0.22e1.4% of total soil Al) for the all soil samples. However the Al amounts extracted by NH4Cl (1 mol l1) and CuCl2 (0.5 mol l1) from soil samples from sector I, were totally different to each other and also the efficiency of these reagent relatively to the total soil Al was 27e37% and 0.5e21% respectively, was much higher. The same procedures described in the section Material and methods were used in order to evaluate the aluminum soil distribution and mobility in the samples from sector 2. Generally the marked concentrations for particular forms of aluminum in analysed soil samples were significantly lower, compared to the values obtained for samples from post-crystallization leachate disposal sites. Álvarez et al. (2002) determined aluminum extracted by: acid oxalate (Alo), sodium pyrophospate (Alp), CuCl2 (Alcu) and NH4Cl (Alex) in soil samples collected in the forest areas. In the case of aluminum in the low- and medium-stability fraction (Alcu) and in the high stability complexes (Alp-Alcu) with organic matter, the concentrations were determined at a similar level for both fractions, that is for Alcu ranging between 0.04 and 0.46% (the mean value of 0.25%) and for Alp-Alcu ranging from 0.08 to 0.38% (the mean value of 0.23%). It is worth mentioning that the forest soils were characterized by high content of organic matter. Comparing the results for these fraction obtained for soil samples also collected from the forest areas in sector II, the much higher concentrations of organic aluminum fractions were determined (for Alcu: 2.8e19% including the mean value of 8.5%, and for Alp-Alcu: 0.44e16.5%, with the mean value of 5.0%). This results are very similar to the results obtained by Walna et al. (2005) in forest soil samples collected in the area of the Wielkopolski National Park (Poland). Walna et al. (2005) used the same type of extractants (CuCl2 and Na4P2O7), determined the concentration of strongly bound organic Al (Alp-Alcu) in ranged between 1.7 and 18.5%. The released of substantial amounts of this aluminum fraction may be due to aluminum from interlayer spaces of clay minerals and this fraction reflects to some extent the lithological variation of the analysed soils in both case. Moreover the form extracted by Na4P2O7 is like
exchangeable Al considered potentially highly reactive (Walna et al., 2005). It is clearly connected with research by Zo1otajkin et al. (2011) where the concentration of aluminum fraction extracted by Na4P2O7 determined in the ranges from 1177 to 4805 mg kg1 in the forest samples. The presented results related to the determination of various forms of aluminum in soil samples. In the case of plants, the research focused mainly on the determination of total aluminum. For example: in plants grown in the laboratory from the seeds of Pinus sylvetris and Picea abies (Shöll et al., 2004), as well as in plants from anthropogenic lakes (Sarmecka-Cymerman and Kempers, 2001), in soybean plant (Dong et al., 1995), in tea (Mehra and Baker, 2007) also in the roots of Arabiodopis plants at the cellular level (Ille_ s et al., 2006). The single-step extraction of aluminum using different extractants in grass samples (Festuca rubra) from the open quartize mine area, was performed by Matús et al. (2006). Matús et al. (2006) determined the concentration of the particular fraction of aluminum in grass stems, for example: Alsw fraction (380e 1100 mg kg1), Alcu (380e830 mg kg1), Alex (100e1100 mg kg1), Alo (380e1200 mg kg1) and Alp fraction (400e800 mg kg1). Comparing these results with those obtained for samples of plants from the area of post-crystallization leachate disposal site (Table 1), the significantly lower concentration of aluminum was observed. It can be connected with pH value of analysed plant samples, because the range of pH for grass stem sample was 2.8e5.0 and for pH for plants from sector I was 4.79e6.44. Probably, that is why, only in sample of A. vulgaris root (pH ¼ 4.79) the determined concentration of all type of aluminum fraction was much higher. 5. Conclusions The fractionation of aluminum by single-step extraction in samples of soils, plants and leaves collected in the areas with varying degrees of pollution allowed for the formulation of the following conclusions: Significant contribution of available aluminum fraction was observed (Alsw and Alex) in soil samples from the area of postcrystallization leachate disposal site, which suggests aluminum migration to the bioavailable fraction. The simple application based on the extractants can be used as an effective and rapid tool for the estimation of risk of aluminum toxicity. High concentrations of organic aluminum fraction, particularly in the case of noncrystalline fraction were determined for all the analysed samples, despite the low pH value, especially for samples collected in the area of the chemical plant (sector I). It should be noted that the high concentration of organic aluminum fractions may be related not only to the presence of aluminum bound to organic matter, but it may also suggest the strength of elution reagents used in the extraction. It should be emphasized that in the conditions of pH for the analysed samples, particularly in sector I, aluminum in the form of organic complexes may occur in low concentrations (at pH < 4 form Al3þ becomes predominant and at pH z 5e7 inorganic aluminum complexes prevail depending on the concentration of particular existing inorganic ligands). According to the plants analysis, the highest concentrations of aluminum in all the fractions were determined in the root of A. vulgaris. Taking into account the toxicity of aluminum, high concentrations of aluminum, especially the water soluble (Alsw) and exchangeable fraction (Alex), in the root may significantly affect the development of this species. This trend was not found in the concentrations of aluminum in different fractions for different morphological parts of plants and leaves, which suggests the individual ways of aluminum accumulation and different degrees of tolerance to this element by a given plant species. A strong relationship between the pH values in soil and leaf
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
samples was found for fraction Alsw in sector I in contrast to sector II, where no variation in the concentration of this form of aluminum as a function of pH was found. Summing, it might be concluded, that proposed under this study procedures consists in performing several single extraction, can be used in order to evaluate the aluminum soil and plant distribution and mobility in the monitoring area with the post-crystallization deposits. Moreover used selectivity single extractants related to plant available aluminum can be a sensitive indicator of the increasing aluminum toxicity in plants not only in the polluted area but also in protected environment. Acknowledgments The research was supported by the Polish Ministry of Science and Higher Education through research project N 304 374 338 (2010e2012). References Agemian, H., Chau, A.S.Y., 1976. Evaluation of extraction techniques for the determination of metals in aquatic sediments. Analyst 101, 761e767. Álvarez, E., Monterosso, M.L., Macros, F., 2002. Aluminium fractionation in Galician (NW Spain) forest soil as related to vegetation and parent material. For. Ecol. Manage. 166, 193e206. Álvarez, E., Fernández- Marcos, M.L., Monterroso, C., Fernández-Sanjurjo, 2005. Application of aluminium toxicity indices to soils under various forest species. For. Ecol. Manage. 211, 227e239. Brandtberg, P.O., Simonsson, M., 2003. Aluminum and iron chemistry in the O horizon changed by a shift in tree species composition. Biogeochem. 63, 207e 228. Darkó, E., Ambrus, H., Stefanovits-Bányai, E., Fodor, J., Bakos, F., Barnabás, B., 2004. Aluminium toxicity, Al tolerance and oxidative stress in an Al-sensitive wheat genotype and in Al-tolerant lines developed by in vitro microspore selection. Plant Sci. 166, 583e591. Dong, D., Ramsey, M.H., Thorton, I., 1995. Effects of soil pH on Al availability in soils and its uptake by the soybean plant. Geochem. Explor. 55, 223e230. Drabek, O., Mladkova, L., Boruvka, L., Syakowa, J., Nikodem, A., Nemecek, K., 2005. Comparison of water-soluble and exchangeable forms of Al in acid forest soils. J. Inorg. Biochem. 99, 1788e1795. Fernández-Sanjurjo, M.J., Álvarez, E., García-Rodeja, E., 1998. Speciation and solubility control of aluminium in soils developed from slates of the river Sor watershed (Galicia, NW Spain). Water Air Soil Pollut. 103, 35e53. Frankowski, M., Zio1a-Frankowska, A., 2010. Speciation analysis of aluminium and aluminium fluoride complexes by HPIC-UVVIS. Talanta 82, 1763e1769. Frankowski, M., Zio1a-Frankowska, A., Siepak, J., 2010. Speciation of aluminum fluoride complexes and Al3þ in soils from the vicini ty of an aluminum smelter plant by hyphenated high performance ion chromatography flame atomic absorption spectrometry technique. Microchem. J. 95, 366e372. Hargrove, W.L., Thomas, G.W., 1981. Extraction of aluminum from aluminumorganic matter complexes. Soil Sci. Soc. Am. J. 45, 151e153. Ille_ s, P., Schlicht, M., Pavlovkin, J., Lichtscheidl, I., Baluska, F., Ove cka, M., 2006. Aluminium toxicity in plants: internalization of aluminium into cells of the transition zone in Arabidopsis root apices related to changes in plasma membrane potential, endosomal behaviour, and nitric oxide production. Exp. Bot. 57, 4201e4213.
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Kovácik, J., Stork, F., Klejdus, B., Jiri Grúz, J., Hedbavny, J., 2012. Effect of metabolic regulators on aluminium uptake and toxicity in Matricaria chamomilla plants. Plant Physiol. Biochem. 54, 140e148. Kubová, J., Matús, P., Bujdos, M., Medved, J., 2005. Influence of acid mining activity on release of aluminium to the environment. Anal. Chim. 547, 119e125. Matús, P., Kubová, J., Bujdos, M., Medved, J., 2005. Determination of operationally defined fractions of aluminium in reference materials and acid attacked environmental samples. Anal. Chim. 540, 33e43. Matús, P., Kubová, J., Bujdos, M., Medved, J., 2006. Free aluminium extraction from various reference materials and acid soils with relation to plant availability. Talanta 70, 996e1005. Matús, P., Kubová, J., Bujdos, M., Medved, J., Stresko, V., 2004. Chemical partitioning of aluminium in rocks, soils, and sediments acidified by mining activity. Anal. Bioanal. Chem. 379, 96e103. Matús, P., Hagarová, I., Bujdos, M., Divis, P., Kubová, J., 2009. Determination of trace amounts of total dissolved cationic aluminium species in environmental samples by solid phase extraction using nanometer-sized titanium dioxide and atomic spectrometry techniques. J. Inorg. Biochem. 103, 1473e1479. Matzner, E., Prenzel, J., 1992. Acid deposition in the German Soiling area: effects on soil solution chemistry and Al mobilization. Water Air Soil Pollut. 61, 221e234. Mehra, A., Baker, C.L., 2007. Leaching and bioavailability of aluminium, copper and manganese from tea. Food Chem. 100, 1456e1463. Morita, A., Yanagisawa, O., Maeda, S., Takatsu, S., Ikka, T., 2011. Tea plant (Camellia sinensis L.) roots secrete oxalic acid and caffeine into medium containing aluminum. Soil Sci. Plant Nutr. 57, 796e802. Rezaee, F., Ghanati, F., Behmanesh, M., 2013. Antioxidant activity and expression of catalase gene of (Eustoma grandiflorum L) in response to boron and aluminium. South Afr. J. Bot. 84, 13e18. Rout, G.R., Samatary, S., Das, P., 2001. Aluminium toxicity in plants: a review. Agronomie 21, 3e21. Sarmecka-Cymerman, A., Kempers, A.J., 2001. Concentrations of heavy metals and plant nutrients in water, sediments and aquatic macrophytes of anthropogenic lakes (former open cut brown coal mines) differing in stage of acidification. Sci. Tot. Environ. 281, 87e98. Shöll, L., Keltjens, W.G., Hoffland, E., Breemen, N., 2004. Aluminium concentration versus the base cation to aluminium ratio as predictors for aluminium toxicity in Pinus sylvestris and Picea abies seedlings. For. Ecol. Manage. 195, 301e309. Sutherland, R.A., Tack, F.M.G., Ziegler, A.D., Bussen, J.O., 2004. Metal extraction from road sediments using nine partial decomposition procedures. Appl. Geochem. 19, 947e952. Sutherland, R.A., 2002. Comparison between non-residual Al, Co, Cu, Fe, Mn, Ni, Pb and Zn released by a three-step sequential extraction procedure and a dilute hydrochloric acid leach for soil and road deposited sediment. Appl. Geochem. 17, 353e365. Sutherland, R.A., Tack, F.M.G., Tolosa, C.A., Verloo, M.G., 2001. Metal extraction from road sediment using different strength reagents: impact on anthropogenic contaminate signals. Environ. Monit. Assess. 71, 221e242. Takeda, A., Tsukada, H., Takaku, Y., Hisamatsu, S., Inaba, J., Nanzyo, M., 2006. Extractability of major and trace elements from agricultural soils using chemical extraction methods: application for phytoavailability assessment. Soil Sci. Plant Nutr. 52, 406e417. Tolrà, R., Vogel-Mikus, K., Hajiboland, R., Kump, P., Pongrac, P., Kaulich, B., Gianoncelli, A., Babin, V., Barceló, J., Regvar, M., Ch, Poschenrieder, 2011. Localization of aluminium in tea (Camellia sinensis) leaves using low energy Xray fluorescence spectro-microscopy. J. Plant Res. 124, 165e172. Walna, B., Spychalski, W., Siepak, J., 2005. Assessment of potentially reactive pools of aluminium in poor forest soils using two methods of fractionation analysis. J. Inorg. Biochem. 99, 1807e1816. Zhu, M., Jiang, X., Ji, G., 2004. Experimental investigation on aluminum release from Haplic Acrisols in southeastern China. Appl. Geochem. 19, 981e990. ski, A., 2011. Mobile aluminium Zo1otajkin, M., Ciba, J., Kluczka, J., Skwira, M., Smolin in the mountain forest soil of Barania Góra range (Silesian Beskids, Poland). Water Air Soil Pollut. 216, 571e580.
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Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
From soil to leaves e Aluminum fractionation by single step extraction procedures in polluted and protected areas Marcin Frankowski*, Anetta Zio1a-Frankowska, Jerzy Siepak , Umultowska 89b, 61-614 Poznan , Poland Department of Water and Soil Analysis, Faculty of Chemistry, Adam Mickiewicz University in Poznan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 6 November 2012 Received in revised form 26 March 2013 Accepted 11 April 2013 Available online 4 May 2013
The paper presents the fractionation of aluminum in the samples of soil and plants of different species using a selective single-step extraction method. The study was conducted in the area located near a chemical plant, which for many years served as a post-crystallization leachate disposal site storing chemical waste (sector I), and in the area around the site: in Wielkopolski National Park, Rogalin Landscape Park and toward the infiltration ponds at the “De˛ bina” groundwater well-field for the city of (Poland) (sector II). The results of aluminum fractionation in samples of soil, leaves and plants Poznan showed heavy pollution with aluminum, especially in the water soluble aluminum fraction e Alsw (maximum concentration of aluminum in soil extract was 234.8 4.8 mg kg1, in the leaves of Betula pendula it was 107.4 1.8 mg kg1 and in the plants of Artemisia vulgaris (root) and Medicago sativa (leaves) it amounted to 464.7 10.7 mg kg-1and 146.8 1.2 mg kg1 respectively). In addition, the paper presents the problem of organic aluminum fractionation in biological samples and it shows the relationship between aluminum concentration in soil and the analysed woody and herbaceous species. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Aluminium Fractionation Single-step extraction Soil Plants
1. Introduction A single-step extraction procedure using an appropriate extractant allows for the separation of one fraction characterized by particular properties. Such a procedure enables the qualitative and quantitative determination of soluble metal fractions, as well as easily exchangeable ones, which in consequence become available for plants, animals and people. The single-step extraction procedure has been used to fractionate aluminum in agricultural soils (Takeda et al., 2006), forest soils (Zhu et al., 2004), flood plain soils (Drabek et al., 2005), road sediments, lake sediments (Agemian and Chau, 1976; Sutherland et al., 2001, 2004; Sutherland, 2002), sedimentary rocks, soils from mining areas (Matús et al., 2004, 2005, 2006; Kubova et al., 2005) and soils from areas polluted with aluminum (Frankowski et al., 2010; Frankowski and Zio1aFrankowska, 2010). In the case of aluminum and other elements including heavy metals or metalloids, the most frequently used single-step extraction methods include the deionized water method (water soluble fraction e Alsw). This approach is characteristic of the element fraction which may be dissolved to form a solution in the environment. Despite their low toxicity, the
* Corresponding author. Tel.: þ48 502305156. E-mail address: [email protected] (M. Frankowski). 0301-4797/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvman.2013.04.033
exchangeable aluminum fraction and organic fractions provide substantial information about the condition of the natural environment. It is possible to determine different aluminum fractions in solid samples depending on the extractant used. Aluminum extracted by NH4Cl or KCl is exchangeable (Alex) (Alvarez et al., 2002; Walna et al., 2005). In turn, when extracted by 0.2 M ammonium oxalate, it is an estimate of total non-crystalline Al, which can selectively dissolve aluminum in poorly ordered soil including aluminum bound to organic matter (Alvarez et al., 2002; Fernández-Sanjurjo et al., 1998). Extraction by 0.5 M CuCl2 allows for the determination of aluminum forming low- and mediumstability complexes with organic matter (Alvarez et al., 2002) and it also promotes the depolymerization of OHeAl polymers (Hargrove and Thomas, 1981). Sodium pyrophosphate used as a reagent is considered to determine all forms of organically bound aluminum (total organically bound Al). This fraction, like exchangeable Al, is considered to be potentially highly reactive. It should be stressed that during the extraction of organic forms, some amounts of inorganic Al, especially in the poorly ordered or non-crystalline phase, can also be extracted (Brandtberg and Simonsson, 2003). The next extractant used in the single-step extraction procedure is dithionite-citrate buffer (DCB) which represents all free Al compounds (AlDCB) (Matzner and Prenzel, 1992). Other aluminum forms are determined by calculating the differences in the concentration of certain aluminum fractions.
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It is well known that the acid deposition leads to the substantial increases of the dissolved Al concentrations in the acidified soils and surface waters. Besides the continuing acidification of soils with the low buffering capacity leads to an increase of the aluminum mobilization in the environment and can to release potentially toxic aluminum species into the soil solution and surface water (Fernández-Sanjurjo et al., 1998; Matús et al., 2009; Walna et al., 2005). The toxicity and bioavailability of aluminum is dependent on its distribution among the various forms or species coexisting in the environment. The free Al3þ, AlOH2þ, and AlðOHÞþ 2 species were found to be the most crucial to evaluate its toxicity and to predict the impact of the proton inputs in the soils and surface waters (Matús et al., 2009; Darko et al., 2004). The other complexes with aluminum including soluble organo-Al and fluoride-Al, sulfate-Al complexes are less phytotoxic (Álvarez et al., 2005). The main symptom of toxicity effect of aluminum is the dramatic inhibition of root growth, which occurs within minutes of exposure to Al, even at micromolar concentrations (Ille_ s et al., 2006; Tolrà et al., 2011; Morita et al., 2011). It can be stated, that aluminum toxicity is one of the main factors limiting plant growth in acid soil (about 40% of the world’s arable lands) (Rout et al., 2001; Rezaee et al., 2013; Kovácik et al., 2012). In sum the form of soil of Al is a key factor of its potential risk impact not only to the plants and also to the living organisms. That is why the information about aluminum forms which are more or less readily released into the solution is important and can be achieved by the extraction of fraction of the aluminum by chemical reagents. The main aims of this work were: (1) to determine the environmental pollution in the area of post-crystallization leachate disposal site, (2) to determine the variability and occurrence of aluminum in soil using single step extraction procedures, (3) to apply single step extraction procedures to fractionate aluminum in leaf and plant samples, (4) to compare the concentration of aluminum in soil with the concentration of aluminum in the leaves of various tree species.
2. Materials and methods The “LUVENA” S.A. chemical plant is located in the south , 2.5 km south of the artificial eastern part of the town of Lubon (Poland). The plant takes up recharge well-field “De˛ bina” of Poznan the area of about 59 ha. To the north of the chemical plant, there are industrial grounds and afforested areas spreading across the meanders of the Warta River. To the south, there is an aggregate mine, and in the distance of about 0.7 km runs the border of Wielkopolski National Park. The southern border of the described area is the Warta River, while the western border are the old river beds of the Warta River, separated from the main stream of the river but still filled with water. In the distance of about 200 m to the southewest of the chemical plant there is a post-crystallization leachate disposal site. The post-production disposal facility is a dammed-up underground tank with a built-up superstructure, which does not contain any additional safety devices to reduce the migration of pollutants to the water-bearing layer. It takes up the area of about 2 ha and its removal began in the year 2005. The chemical plant has been producing aluminum fluoride since 1971. Post-crystallization leachate generated in the production process has been collected at the post-crystallization leachate disposal site in the form of semifluid pulp. In the 1980s, such chemicals as superphosphate, hydrofluoric acid, aluminum fluoride, potassium fluoroborate and vanadium catalyst were also produced here. The soil and leaf samples were collected for analysis in June 2010. In order to determine spatial variability, the study area was divided into two zones:
Zone 1 (sector I) e the area situated at the chemical plant in , with the post-crystallization leachate disposal site Lubon (samples 1e5) e point source of pollution. Zone 2 (sector 2) e area of Wielkopolski National Park, Rogalin Landscape Park, outside the area of the point source of pollution (samples 6e15) toward the infiltration ponds of the “Debina” (Poland). groundwater well-field for the city of Poznan At each sampling point, soil and leaf samples of predominant tree species were collected. In sector 1, at points 1e4, the samples of Betula Pendula were collected, while at point 5 the leaves of Robinia pseudoacacia were taken for analysis. Furthermore, within the sector comprising points 1e5 (in the area of point 5), in the revitalized area, the samples of the following plants were collected: Medicago sativa, Melilotus albus, Artemisia vulgaris, Melilotus officinalis, Holcus lanatus. In sector II, leaf samples of the following predominant tree species were collected: Betula pendula (points 8,9,15), Robinia pseduoacacia (points 9, 10, 11, 14), Tilia platyphylos (point 7) and Salix alba (points 6, 10, 12, 13) (Fig. 1).. The soil samples were collected for analysis at the depth of 0e 20 cm, while the leaf samples were taken at the height of 120 cm above ground level. Herbaceous plants were collected up to 60 cm above ground level. The samples were dried at room temperature. Hygroscopic water and substances dissolved in it were treated as an integral component of the sample. After drying, a soil sample was passed through sieves with mesh sizes of 2.0, 1.0, 0.5, 0.25, 0.1, and 0.063 mm, in accordance with the Polish Norms: PN-ISO 565:2000 and PN-ISO 3310-1:2000, using a LAB-11-200/UP sieve shaker (EKO-LAB, Brzesko, Poland). The grain size fraction of 0.1e0.25 mm was predominant and it was used to prepare soil extracts. Leaf samples were ground and stored in PP bags until the extraction and mineralization were performed. The samples were then extracted in order to separate the aluminum fractions: - soil water fraction (Alsw) e extracted by deionized water - exchangeable Al fraction (Alex) e extracted by 1 M NH4Cl - low- and medium-stability complexes of Al with organic matter (Alcu) e extracted by 0.5 M CuCl2 - total organically bound Al (Alp) e extracted by 0.1 M Na2P4O7 - total non-crystalline Al (Alo) e extracted by 0.2 M C2H8N2O4 - weakly bound complexes of Al with organic matter (Alcu-Alex) e calculated - high-stability complexes with organic matter (Alp-Alcu) e calculated - inorganic non-crystalline Al (Alo-Alp) e calculated - pseudo total aluminum occluded on the grain (Alptc) e EPA 3051 (in the case of plants: Altc means total concentration of aluminum e full mineralization. - Concentration ratio: it is the Altc/Alo ratio used as a factor of availability of inorganic and organic fraction of aluminum (calculated based on results for particular fraction presented in Table 1). The extraction was conducted at the temperature of 25 C using a magnetic mixer. The extracts were prepared in proportion 1:10 (v/ v) for the predominant fraction in a 100 g sample with 0.1e 0.25 mm grain size. For the soil water extract fraction of aluminum, the sample pH was determined. Furthermore, the samples were mineralized using the EPA 3051 method (EPA, USA) in order to separate the pseudo total content of aluminum. The pH (H2O) was determined using the Orion 5-star Plus (Thermo, USA) meter with a Single Pore pH electrode (Hamilton, USA). The determination of aluminum was performed in 3 replications, and the % RSD did not exceed 5%. Aluminum was determined using the Shimadzu AA7000
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Table 1 Results of pH and aluminum concentration for all separated fractions of aluminum in soil and leaves samples of different tree and plant species. GPS map point
Sample type
pH (H2O)
Alsw
Alex
Alcu
Alp
Alo
Alcu-Alex
Alp-Alcu
Alo-Alp
Alptc (Altc)
1 1 2 2 3 3 4 4 5 5 5 5 5 5 5 5 5 5 6 6 7 7 8 8 9 9 9 10 10 10 11 11 12 12 13 13 14 14 15 15
Soil Betula pendula Soil Betula pendula Soil Betula pendula Soil Betula pendula Soil Robinia pseudoacacia Medicago sativa (flower) Medicago sativa (leaves) Melilotus albus (leaves) Artemisia vulgaris (leaves) Artemisia vulgaris (root) Melilotus officinalis (leaves) Holcus lanatus (leaves) Holcus lanatus (flower) Soil Salix Alba Soil Tilia platyphyllos Soil Betula pendula Soil Robinia pseudoacacia Betula pendula Soil Robinia pseudoacacia Salix Alba Soil Robinia pseudoacacia Soil Salix Alba Soil Salix Alba Soil Robinia pseudoacacia Soil Betula pendula
5.37 5.52 3.97 5.12 5.04 5.89 3.81 5.65 3.83 6.42 6.44 6.08 6.04 6.37 4.79 5.46 5.37 5.85 4.91 5.64 5.06 5.62 4.89 5.78 6.19 6.41 5.49 6.46 6.35 6.43 7.34 6.13 4.74 5.62 4.73 5.71 4.52 6.23 4.73 5.82
32.79 8.21 331.7 35.1 77.93 31.3 34.83 107.6 234.8 5.4 17.43 146.75 56.73 8.47 464.70 69.23 99.88 39.66 1.99 5.53 2.07 5.77 1.49 6.97 0.41 4.68 6.25 0.99 1.21 0.61 0.99 2.76 6.46 3.01 5.97 0.84 5.17 1.68 6.56 3.37
13.95 8.51 585.7 62.5 6.45 30.5 57.54 107.5 557.6 4.5 27.88 160.2 57.57 30.83 556.1 96.99 128.3 48.56 3.88 6.48 4.39 6.92 45.01 8.95 1.49 6.99 6.69 1.29 1.48 1.11 1.29 3.32 7.96 3.13 2.85 3.24 46.85 6.97 62.39 9.49
387.9 13.51 1158 72.1 382.9 36.21 339.1 169.5 922.7 8.17 28.97 286.78 85.57 276.6 1466 161.3 325.6 90.38 76.08 38.22 70.31 13.11 137.5 22.84 30.89 11.17 12.74 44.59 11.54 12.14 49.52 14.54 60.69 17.91 84.25 13.46 100.4 11.11 200.6 23.68
441.2 17.5 1334 78.6 432.1 53.5 405.1 210.5 984.6 13.22 15.14 106.8 36.92 279.4 1195 32.69 208.2 39.34 248.8 1.69 93.62 6.36 316.3 8.56 35.69 0.062 0.099 51.69 0.794 0.198 53.84 0.595 85.46 4.372 100.1 5.07 147.8 1.99 266.3 6.46
522.6 43.22 1566 156.5 434.4 57.24 427.8 229.5 1375 18.51 58.91 252.6 79.23 284.5 1954 162.4 317.2 99.85 252.9 6.76 111.3 20.88 329.8 25.92 36.53 3.68 5.89 61.35 1.88 3.68 60.85 2.48 87.98 7.56 111.1 12.25 192.2 2.68 268.9 13.76
373.95 5.00 572.3 9.6 376.45 5.71 281.56 62 365.1 3.67 1.09 126.58 28 245.77 909.9 64.31 197.3 41.82 72.2 31.74 65.92 6.19 92.49 13.89 29.4 4.18 6.05 43.3 10.06 11.03 48.23 11.22 52.73 14.78 81.4 10.22 53.55 4.14 138.2 14.19
53.3 4.00 176 6.5 49.2 17.29 66 41 61.9 5.05
81.4 25.72 232 77.9 2.3 3.74 22.7 19 390.4 5.29 43.77 145.8 42.31 5.1 759 129.71 109 60.51 4.1 5.07 17.68 14.52 13.5 17.36 0.84 3.618 5.791 9.66 1.086 3.482 7.01 1.885 2.52 3.188 11 7.18 44.4 0.69 2.6 7.3
1054 56.4 3634 161.1 1237 116.6 1257 407.1 2678 43.32 73.6 404.6 98.84 595.21 2969 181.2 418.8 565.4 1392 43.2 1436 36.81 1082 54.95 835.4 14.96 20.22 1623 19.27 17.41 990.2 18.29 615.1 34.24 1145 49.98 773.6 14.22 1007 37.14
a
a a a
2.8 a a a a
172.72 a
23.31 a
178.8 a
4.8 a a
7.1 a a
4.32 a
24.77 a
15.85 a
47.4 a
65.7 a
Negative subtraction Alp-Alcu, Alptc (pseudo total content for soil samples), Altc (total content for leaves and plant samples), n ¼ 3, RSD<5%.
spectrometer (Shimadzu, Japan). In order to check the reliability of FAAS measurement certified reference materials were used: for soil SRM 2709 and for leaves SRM 1515 (National Institute of Standards and Technology, USA). These reference materials: SRM 2709 and SRM 1515 were analysed in six repetitions. The results obtained for the certified reference materials have been presented in Table 1. Recoveries of both SRM materials were 99.8% for soil and 98.7% for leaves. 3. Results The results of pH value and aluminum concentrations for all separated fractions of aluminum in soil and leaf samples of different tree and plant species were presented in Table 1. 3.1. Soil The concentration of particular aluminum fractions: soil water extract fraction (Alsw), exchangeable Al fraction (Alex), low- and medium-stability complexes of Al with organic matter (Alcu), total organically bound Al (Alp), total non-crystalline Al (Alo), weakly bound complexes of Al with organic matter (Alcu-Alex), highstability complexes with organic matter (Alp-Alcu), inorganic non-crystalline Al (Alo-Alp) and pseudo-total content of aluminum (Alptc) for all the analysed soil samples were determined. In order to determine the variability and potential availability of aluminum,
it was assumed that fraction Alptc would be treated as the pseudototal concentration of aluminum, and namely as the fraction of aluminum which does not impair the structure of aluminosilicates (non-crystalline and partially crystalline aluminum). Based on the above assumption, the water soluble fraction of aluminum (Alsw) constituted 2.8e9.1% of the study area in sector I, which is 9.1% and 8.8%, respectively, for points 2 and 5. Such a large contribution of this fraction was caused by the availability of post-crystallization leachate, as points 2 and 5 were located directly in the area of the former disposal facility. As regards the remaining sampling points in sector I, a significantly smaller contribution of water soluble aluminum fraction was found owing to the lack of direct influence of the post-production disposal facility. For sector II, comprising the remaining sample collection points (samples 6e15), the level of aluminum availability in the water soluble fraction did not exceed 1.1%, and the mean value of this fraction was 0.4%. A similar variability trend was observed for Alex, although the aluminum concentration in this fraction was about twice as high as the concentration of water soluble aluminum fraction for samples 2, 4 and 5. The percentage contribution of Alex in comparison with fraction Alptc in sector I ranged between 0.5% and 20.8%. For samples collected in sector II, the aluminum concentration (Alex) is about twice as high, with the exception of samples 8, 14 and 15, for which the values of 4.1%, 6.1% and 6.2% were determined respectively, which is a significant increase in concentration compared with Alsw. In the case of organic aluminum and its fractions: Alcu,
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M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
Alp, Alcu-Alex and Alp-Alcu, a variability trend similar to that of fractions Alsw and Alex was observed. The total organic aluminum found ranged from 405.1 to 1334 mg kg1 (32.2%e41.9%) in sector I and from 35.69 to 316.3 mg kg1 (3.2%e29.2%) in sector II. Only in sample 8 a much higher concentration of organic aluminum (316.3 mg kg1) was determined. However, with the exception of sample 8, maximum concentration of organic aluminum for sector II was 266.3 mg kg1 (26.4%). Based on the obtained study results, it should be underlined that the fractions of organic aluminum: Alcu, Alp, Alcu-Alex and Alp-Alcu did not fully reflect the conditions necessary to break the bond with organic matter. This particularly related to the calculated aluminum fractions (Alcu-Alex and AlpAlcu), as Alcu-Alex concerned weakly bound Al, and the result of Alp-Alcu calculation was high-stability Al bound to organic matter. Should it therefore be assumed that aluminum bound to organic matter is a fraction of exchangeable aluminum? Similarly, drawing a comparison between fractions Alcu and Alp, it should be stated that these results are often similar, and Alcu (low- and medium-stability fraction) does not fully meet the extraction conditions necessary for breaking the AleOM bond. Therefore, it seems justified to use Na2P4O7 as the only reagent in the extraction of total organic aluminum. It should also be stressed that the extraction conditions of the organic fraction are strong enough to enable the extraction of both fraction Alsw and fraction Alex. Aluminum concentration in the total non-crystalline fraction (Alo) for sector I was 34%e51.3% (405.1e1334 mg kg1), while for sector II it amounted to 3.78e30.5% (35.69e316.3 mg kg1). The variability trend depending on the place of sample collection was similar to that observed for the previously discussed aluminum fractions. 3.2. Plants In sector I, soil and leaf samples of B. pendula (points 1e4) and R. pseudoacacia (point 5) were taken for analysis. In sector II, leaf samples of the following predominant tree species were collected: B. pendula, R. pseduoacacia, T. platyphylos and S. alba (see Table 1). The highest concentration of aluminum for all the analysed fractions was determined in sample 4 (sector I). Aluminum concentration was also highest in samples from sector I (samples 1e5), while in sector II it reached a similar level of concentration for particular tree species. Based on the study results, it was observed that the lowest concentrations were determined for R. pseudoacacia leaf samples (both in sector I and II). No significant differences in the obtained results of aluminum concentration were found for B. pendula, Salix Alba and T. pytophylos. Taking into account aluminum concentration in particular fractions of plant sample extracts, the similarity in the obtained results between fractions Alsw and Alex was observed. No influence of pH reaction on the level of aluminum concentration in the pH range of 5.12e6.43 for the whole set of samples in sectors I and II was found. However, it should be stressed that in comparison with Altc, the aluminum concentration in fraction Alsw was relatively high and it ranged from 12.5 to 46.8% for sector I and from 1.7 to 31.3% for sector II. The presence of such high concentrations in fraction Alsw was connected with the possibility to extract the whole sample, and not only its surface. In the case of organic aluminum forms, no similarity between particular organic aluminum fractions was found. Such similarities, however, were observed for soil samples. For 12 out of 17 analysed samples (and for all the 12 samples from sector II), a negative result of calculation between Alp and Alcu was found (high-stability complexes with organic matter, from 6.75 to 36.53 mg kg1). This might have been caused by another type of aluminum bond with organic matter, which resulted in higher or similar concentrations for fraction Alcu. It might have also been
linked to the presence of aluminum in the form of other complexes, not only the ones with fluorides, which were predominant in this sector (Frankowski et al., 2010; Frankowski and Zio1a-Frankowska, 2010). Therefore, the conclusion can be drawn that aluminum does not form stable complexes with OM in the case of unpolluted soil. This concerns the possible absorption of aluminum by plants through their root system, or the element is transformed as a result of the occurrence of other competitive ligands which can form more stable complexes with aluminum, such as inorganic complexes. In the case of samples from sector I, the predominant aluminum fraction was Alo, while for sector II, the Alcu fraction of organic aluminum extracted by copper chloride (II) prevailed. The Altc-to-Alo concentration ratio ranged between 1.03 for sample 2 and 10.25 for sample 10. It is worth noting that the Altc-to-Alo ratio was lowest for sector I (the mean ratio ¼ 1.8), while for sector II, the mean ratio was 4.8, which suggests an entirely different nature of these samples in terms of aluminum availability in the inorganic and organic non-crystalline form, as well as in aluminum extracted by 0.2 M C2H8N2O4. 3.3. Plant extracts from sector I Within the studies conducted in sector I concerning determinations of aluminum and its fractions in soil and tree leaves, samples of plants used to revitalize the post-crystallization disposal site were collected. In order to define the occurrence variability of a given aluminum fraction depending on the plant species, and in order to define the direct impact of aluminum on the soil where the plants grew, the following plant samples (and their above-ground plant parts) were analysed: A. vulgaris (leaves), A. vulgaris (root), H. lanatus (leaves), H. lanatus (flower), M. sativa (flower), M. sativa (leaves), M. albus (leaves), M. officinalis (leaves). The highest concentration was determined in the root of A. vulgaris, which resulted from the accumulation of aluminum in this morphological part of the plant. The fractionation of aluminum directly in the root sample revealed significant contribution of forms Alsw and Alex amounting to 464.7 and 556.1 mg kg1 of aluminum respectively. This contribution was larger compared to Altc, amounting to 2976 mg kg1, which constituted 15.7 and 18.7% of this fraction contribution respectively. This suggests the aluminum availability at pH ¼ 4.67 in the form of inorganic aluminum complexes, regardless of the fact that the contribution of inorganic noncrystalline aluminum fraction amounted to only 0.9%. In the case of H. lanatus and M. sativa flower samples, the contribution of aluminum in particular fractions was definitely lower compared with the results obtained for A. vulgaris root samples. However, significant differences were observed in the determined aluminum concentrations and in the contribution of particular fractions for the analysed flower samples of both plant species, which might be the effect of using different mechanisms to absorb aluminum from soil. The analysis of total concentration of aluminum (Altc) in the flowers of H. lanatus and M. sativa in relation to particular aluminum fractions with a similar pH of water extract samples (5.85 and 6.44 respectively) revealed that the flowers of H. lanatus might contain aluminum strongly bound in the flower’s structure and not easily extracted using an extractant, regardless of the fact that aluminum concentrations for particular fractions were two times higher than in the case of M. sativa. Individual features determine aluminum accumulation in a plant depending on the species resistance. It should be emphasized that the analysed samples of H. lanatus and M. sativa flowers differ significantly in their structure, but the total aluminum content (Altc) in their leaves is similar and amounts to 418.8 and 404.6 mg kg1 respectively for H. lanatus and M. sativa. In case of the other analysed plant species e M. Albus and M. Officinalis e lower total concentrations of
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
aluminum (Altc) were determined, amounting to 98.84 and 181.2 mg kg1. Alternatively, in the leaves of A. vulgaris, the highest concentration of total aluminum was found, amounting to 595.2 mg kg1. Moreover, for this plant species the lowest concentration of aluminum fractions Alsw and Alex (where the % contribution in relation to total aluminum concentration was 1.4 and 5.2 respectively) and the highest Alp and Alo concentrations (47.0 and 47.8%) were determined, which might be linked to the accumulation of aluminum and blocking its transportation from the root to other parts of the plant (this also results from the different structure of the plant and larger leaf surface). It is interesting that high concentrations and the contribution of the soilewater (57.4% for M. albus and 38.2 for M. officinalis) and exchangeable (58.2% for M. albus and 53.5% for M. officinalis) fractions suggest high availability of aluminum, which might pose a threat to the natural environment in the studied area. 3.4. Influence of pH (aluminum soil water fraction) The relationship of soil and leaf samples depending on the place of sample collection (sector I and sector II) was conducted (Fig. 2). The analysis of Alsw fraction did not reveal the concentration variability of this aluminum form in the function of pH reaction for sector II. This may be caused by a different type of aluminum bond and the contribution of other exchangeable ions in the environment of a well-formed soil structure. For sector I, significant contribution of aluminum at lower reaction values (pH < 4.0) in soil samples was observed, which is the effect of aluminum availability in the form in which it entered soil in sector I (post-crystallization leachate disposal site). For the other soil and leaf samples in sector I, higher concentrations of Alsw at lower pH were observed. 3.5. Soileplants relationship In order to analyse aluminum migration from soil to tree leaves, percentage graphs were made for the following aluminum fractions: Alsw, Alex, and Alptc (Altc), for all soil and tree leaf samples (Fig. 3). Based on the results obtained for the soil water fraction
5
(Alsw) of leaf samples of different tree species and soil samples, a relation between sample collection sites and Alsw concentration was observed in both sectors. The samples collected from sector II are especially noteworthy as the concentration of Alsw in soil was higher for the samples (samples 12e15) taken on the right bank of the River Warta. In turn, the concentration of Alsw was higher in the leaf samples (samples 6e11) collected from the left-bank section of the River Warta. For sector I, the concentration of Alsw determined in soil was significantly higher than the concentration in leaves, which resulted from soil pollution. Only in the case of sample 4, higher concentration of aluminum in fraction Alsw of leaves was determined. This difference was caused by the fact that sample 4 was situated outside the area of direct influence of waste disposed at the disposal site. It is noteworthy that the leaf samples of B. pendula (samples 1e4) reached higher concentration values than the leaf samples of R. pseudoacacia (sample 5). In the case of Alex, a variability trend similar to the case of fraction Alsw can be observed. Significant changes were only found for sample 3 in sector I (higher degree of aluminum extraction from plant samples). On the other hand, for sector II, the soil-to-leaves ratio of Alex was higher for samples 8 and 9 and lower for sample 12 in comparison with the results obtained for fraction Alsw. These results, however, do not suggest significant differences between fractions Alsw and Alex (Fig. 4). In the case of aluminum fraction regarded as pseudo-total concentration, over 80% of aluminum bound in soil was observed for all the samples with the exception of sample 4. However, it should be stressed that the aluminum contribution in this fraction was difficult to obtain for plants and it did not constitute the source of assimilable aluminum in the environment. In the case of soil and leaf samples collected from both sectors, the relationship resulting from the possibility to absorb aluminum by the studied tree leaves was observed. A lower soil-to-leaves concentration ratio was observed for R. pseudoacacia (samples 5, 10, 11, 14) and for S. alba (samples 6, 12, 13) in comparison with the samples of B. pendula, where aluminum concentration in the analysed leaf samples was higher both in sector I and sector II (Fig. 5).
Fig. 1. Location of the sampling points.
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M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
Fig. 2. Relationship of soil and leave samples depending on the place of sample collection and reaction value (sector I vs. sector II).
also the organic fraction where different mechanisms of aluminum extraction from the matrix with high content of organic matter were observed. In the work by Kubova et al. (2005), a number of single-step extractions in the soil and plant samples from the sites affected by mining activities were conducted in order to separate different aluminum forms. It should be underlined that the areas of mining activities were rich in minerals containing aluminum and low pH values. The concentration of aluminum in acidified soil samples after extraction by H2O and NH4Cl was 50e250 mg kg1 and 100e 800 mg kg1 respectively. For the comparison the concentration of Alsw and Alex fractions for soil samples collected in the area of post-
4. Discussion The studies of aluminum fractionation using single-step extraction of soil, leaf and plant samples suggest the necessity to discuss the issue of aluminum availability, the issue which has to date concerned the studies of soil samples most frequently originating from the areas highly acidified as a result of dry and wet deposition processes (Drabek et al., 2005; Álvarez et al., 2002; Walna et al., 2005; Zo1otojakin et al. 2011). That is why, the conducted research were designed to showing the significance and necessity of aluminum fractionation in the plant material, especially the fraction Alsw and Alex which are the most mobile and
leaves soil Ratio Alsw in soil vs. Alsw in leaves samples in %
100
80
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
sample Fig. 3. Occurrence of aluminum in soil and leave samples in [%] for the soil water extract fraction (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
leaves soil
100
Ratio Alex in soil vs. Alex in leaves samples in %
7
80
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Fig. 4. Occurrence of aluminum in soil and leave samples in [%] for the exchangeable fraction of aluminum (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
In the case of extraction by C2H8N2O4 (fraction Alo), which can dissolve the free amorphous or crystalline Fe, Al oxides and silicate minerals by reduction and complexation reactions, Kubova et al. (2005) obtained the concentration of aluminum in ranging from 400 to 1160 mg kg1 (0.75e2.2% of total soil Al). In the soils under these study from sector I, the concentration of Alo fraction extracted by the ammonium oxalate was similar (429e 1566 mg kg1), but the contribution of this fraction according to the total soil Al was much higher and amounted to 34e51.3%, which might have resulted from soil samples specification. As can be seen on both type of analysed soil samples (from mining area and
crystallization leachate disposal site (sector I) with also low pH values, amounted to 33e332 mg kg1 and 14e586 mg kg1 properly. It is worth noting that concentration of exchangeable aluminum in soil ranging 90 mg kg1 is considered as a critical value which is associated with visible damage to plants and trees or even their dieback (Walna et al., 2005). In the sample No.2 and No.5 situated in the middle of post-crystallization leachate disposal site (sector I) the high concentrations of exchangeable aluminum (over 550 mg kg1) were associated with low pH values of the soil. The same relationship has been established by Walna et al. (2005) and Zo1otajkin et al. (2011) for samples of forest soils.
leaves soil
Ratio Alptc in soil vs. Altc in leaves samples in %
100
80
60
40
20
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
sample Fig. 5. Occurrence of aluminum in soil and leave samples in [%] for the pseudototal (Alptc) and total concentration of aluminum (Altc) (for sample no 9 and 10 ratios were calculated for Robinia pseudoacacia).
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M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
chemical plant e sector I) the released amount of Al was relevant and was dependent on the efficiency of the extraction agents. Matús et al. (2006) in the soil samples collected from the open quartize mine area influenced by acid mine solutions, determined various forms of aluminum using single step extraction procedure including the total organically bound aluminum fraction (Alp) by 0.1 M Na2P4O7 reagent. The obtained concentration of Alp fraction ranged from 200 to 3600 mg kg1 which was consist 0.2e4.2% of total soil Al and was the high concentration of Al in soil extracts. In our study in the samples from the polluted area (sector I) the marked concentrations of Alp fraction were lower (405e 1334 mg kg1), but the obtained contribution of these fraction into the total soil Al was much higher (32e42%). In the study by Matús et al. (2006) the high aluminum concentrations which they obtained in extracts using 0.1 M Na2P4O7 (Alp fraction) they associated with the complexation ability of the used agent to impair the structures of clay minerals or weathered secondary minerals. Considering the fact that the samples from a mining area, contained minerals from the aluminosilicate group, it seems highly unlikely that Na2P4O7 reagent was able to impair the aluminosilicate structures. It is well know that, pyrophosphate as a preferred reagent in the extraction of total aluminum formed aluminum complexes from the surface of mineral grains and sometimes from the interlayer spaces of clay minerals to organic matter forms (Walna et al., 2005). According to the other simple salt extractants used by Matús et al. (2006) they found that the efficiencies of the KCl, NH4Cl, BaCl2, CuCl2 and LaCl3 extractants with the concentrations from 0.1 to 1 mol l1 were very similar (0.22e1.4% of total soil Al) for the all soil samples. However the Al amounts extracted by NH4Cl (1 mol l1) and CuCl2 (0.5 mol l1) from soil samples from sector I, were totally different to each other and also the efficiency of these reagent relatively to the total soil Al was 27e37% and 0.5e21% respectively, was much higher. The same procedures described in the section Material and methods were used in order to evaluate the aluminum soil distribution and mobility in the samples from sector 2. Generally the marked concentrations for particular forms of aluminum in analysed soil samples were significantly lower, compared to the values obtained for samples from post-crystallization leachate disposal sites. Álvarez et al. (2002) determined aluminum extracted by: acid oxalate (Alo), sodium pyrophospate (Alp), CuCl2 (Alcu) and NH4Cl (Alex) in soil samples collected in the forest areas. In the case of aluminum in the low- and medium-stability fraction (Alcu) and in the high stability complexes (Alp-Alcu) with organic matter, the concentrations were determined at a similar level for both fractions, that is for Alcu ranging between 0.04 and 0.46% (the mean value of 0.25%) and for Alp-Alcu ranging from 0.08 to 0.38% (the mean value of 0.23%). It is worth mentioning that the forest soils were characterized by high content of organic matter. Comparing the results for these fraction obtained for soil samples also collected from the forest areas in sector II, the much higher concentrations of organic aluminum fractions were determined (for Alcu: 2.8e19% including the mean value of 8.5%, and for Alp-Alcu: 0.44e16.5%, with the mean value of 5.0%). This results are very similar to the results obtained by Walna et al. (2005) in forest soil samples collected in the area of the Wielkopolski National Park (Poland). Walna et al. (2005) used the same type of extractants (CuCl2 and Na4P2O7), determined the concentration of strongly bound organic Al (Alp-Alcu) in ranged between 1.7 and 18.5%. The released of substantial amounts of this aluminum fraction may be due to aluminum from interlayer spaces of clay minerals and this fraction reflects to some extent the lithological variation of the analysed soils in both case. Moreover the form extracted by Na4P2O7 is like
exchangeable Al considered potentially highly reactive (Walna et al., 2005). It is clearly connected with research by Zo1otajkin et al. (2011) where the concentration of aluminum fraction extracted by Na4P2O7 determined in the ranges from 1177 to 4805 mg kg1 in the forest samples. The presented results related to the determination of various forms of aluminum in soil samples. In the case of plants, the research focused mainly on the determination of total aluminum. For example: in plants grown in the laboratory from the seeds of Pinus sylvetris and Picea abies (Shöll et al., 2004), as well as in plants from anthropogenic lakes (Sarmecka-Cymerman and Kempers, 2001), in soybean plant (Dong et al., 1995), in tea (Mehra and Baker, 2007) also in the roots of Arabiodopis plants at the cellular level (Ille_ s et al., 2006). The single-step extraction of aluminum using different extractants in grass samples (Festuca rubra) from the open quartize mine area, was performed by Matús et al. (2006). Matús et al. (2006) determined the concentration of the particular fraction of aluminum in grass stems, for example: Alsw fraction (380e 1100 mg kg1), Alcu (380e830 mg kg1), Alex (100e1100 mg kg1), Alo (380e1200 mg kg1) and Alp fraction (400e800 mg kg1). Comparing these results with those obtained for samples of plants from the area of post-crystallization leachate disposal site (Table 1), the significantly lower concentration of aluminum was observed. It can be connected with pH value of analysed plant samples, because the range of pH for grass stem sample was 2.8e5.0 and for pH for plants from sector I was 4.79e6.44. Probably, that is why, only in sample of A. vulgaris root (pH ¼ 4.79) the determined concentration of all type of aluminum fraction was much higher. 5. Conclusions The fractionation of aluminum by single-step extraction in samples of soils, plants and leaves collected in the areas with varying degrees of pollution allowed for the formulation of the following conclusions: Significant contribution of available aluminum fraction was observed (Alsw and Alex) in soil samples from the area of postcrystallization leachate disposal site, which suggests aluminum migration to the bioavailable fraction. The simple application based on the extractants can be used as an effective and rapid tool for the estimation of risk of aluminum toxicity. High concentrations of organic aluminum fraction, particularly in the case of noncrystalline fraction were determined for all the analysed samples, despite the low pH value, especially for samples collected in the area of the chemical plant (sector I). It should be noted that the high concentration of organic aluminum fractions may be related not only to the presence of aluminum bound to organic matter, but it may also suggest the strength of elution reagents used in the extraction. It should be emphasized that in the conditions of pH for the analysed samples, particularly in sector I, aluminum in the form of organic complexes may occur in low concentrations (at pH < 4 form Al3þ becomes predominant and at pH z 5e7 inorganic aluminum complexes prevail depending on the concentration of particular existing inorganic ligands). According to the plants analysis, the highest concentrations of aluminum in all the fractions were determined in the root of A. vulgaris. Taking into account the toxicity of aluminum, high concentrations of aluminum, especially the water soluble (Alsw) and exchangeable fraction (Alex), in the root may significantly affect the development of this species. This trend was not found in the concentrations of aluminum in different fractions for different morphological parts of plants and leaves, which suggests the individual ways of aluminum accumulation and different degrees of tolerance to this element by a given plant species. A strong relationship between the pH values in soil and leaf
M. Frankowski et al. / Journal of Environmental Management 127 (2013) 1e9
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