Role of EDTA in arsenic mobilization and its uptake by maize grown on an As-polluted soil

Chemosphere 90 (2013) 588–594

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Role of EDTA in arsenic mobilization and its uptake by maize grown on an As-polluted soil Mohamed H.H. Abbas a, Ahmed A. Abdelhafez b,⇑ a b

Faculty of Agriculture, Moshtohor, Benha University, Qhalubia, Egypt Soils, Water and Environment Research Institute (SWERI), Agricultural Research Center (ARC), Giza 12112, Egypt

h i g h l i g h t s " Treating soil with EDTA increased water soluble and AB-DTPA extractable As significantly. " Shoots As uptake increased significantly by EDTA applications. " Roots As uptake did not increase significantly except at 2.5 and 5.0 mmol kg

1

EDTA.

" Applications of EDTA in the presence of maize plant are unsuitable for As phytoextraction. " Only shoots of maize plants grown on soil without EDTA treatment can be used in animal feeding.

a r t i c l e

i n f o

Article history: Received 28 March 2012 Received in revised form 29 July 2012 Accepted 7 August 2012 Available online 16 September 2012 Keywords: Maize Phytoextraction Arsenic EDTA

a b s t r a c t EDTA amendments are widely used for micronutrient fertilization in arid soils, besides their effectiveness in the remediation process of heavy metal from contaminated soils. However, the persistence of EDTA in arsenic contaminated soil may have further negative effects on the grown plants. To investigate the influences of EDTA on soil As, a pot experiment was conducted using a sandy clay loam As-polluted soil treated with gradual rates of EDTA (0, 1.0, 2.5 and 5 mmol kg 1) and planted with maize for two months. The key findings reveal that EDTA applications increased AB-DTPA extractable and water soluble As significantly. Such increases seemed to be the main reasons behind the increase in As uptake by maize plants as the addition of EDTA at the rates of 1.0, 2.5 and 5.0 mmol kg 1 increased significantly As uptake by shoots 1.5, 2.4 and 3.0 folds, respectively compared to the untreated soil. On the other hand, As uptake by roots did not increase significantly except with the highest application rates of 2.5 and 5.0 mmol kg 1. The results also show that arsenic translocation factor (TF) values were too low to attain successful phytoextraction. In conclusion, the bioavailable fraction of As is important to investigate the phytoextraction and phytotoxicity of As. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction Soil alkalinity, low organic matter content and presence of free CaCO3 in arid regions are considered the main factors for reducing micronutrient availability in soil and thus limiting crop productivity (Rashid and Ryan, 2004). One of the strategies to overcome this problem is the use of chelating agents to protect the added micro-nutrients from precipitations and fixation reactions. In this concern, EDTA nutrient complexes have been widely used as fertilizers in arid soils because of their high solubility (Luo et al., 2005) and stability in soil (Gucht, 1994; Mansilla et al., 2006; Wang et al., 2010) and therefore, improve the micronutrient uptake by plants (Grcˇman et al., 2001; Hovsepyan and Greipsson,

2005). Moreover, this chelating agent is widely used for enhancing the phytoextraction of heavy metals from contaminated soils (Hong et al., 1999; Hovsepyan and Greipsson, 2005; Park et al., 2008). It is worthy to mention that the EDTA-nutrient complexes are mostly broken down near the root surfaces, and the nutrient ions rather than the whole molecules were absorbed by the grown plants (Bell et al., 2003), and thus EDTA is released to the biosphere. It is therefore thought that this chelating agent, EDTA, can persist in soil for long periods of time (Oviedo and Rodríguez, 2003) because of its low biodegradability (Tandy et al., 2004) and therefore, possesses a high potential risk for the groundwater with the active soluble complexes with heavy metals (Wu et al., 2004).

⇑ Corresponding author. Tel.: +2 02 35724269, +2 010 22158270; fax: +20 02 35720608. E-mail address: [email protected] (A.A. Abdelhafez). 0045-6535/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2012.08.042

M.H.H. Abbas, A.A. Abdelhafez / Chemosphere 90 (2013) 588–594

Arsenic (As), which is a metalloid, is thought to be slightly affected by EDTA applications to soil (Vaxevanidou et al., 2008). However, the results obtained by Rahman et al. (2008) revealed that the application of EDTA to the growth media could increase the availability and uptake of As(III) and As(V) by the aquatic floating duckweed plants. Furthermore, high correlation coefficient values were obtained by Gregori et al. (2004) between the As content in alfalfa plants and the EDTA extractable fraction of As. Accordingly, the application of EDTA amendments to As contaminated soil is still a matter of confliction concerning its effect on As availability in soil, its uptake and concurrent toxicities on the grown plants. Total As concentrations in soil is still used in most of the researches as a sole reference for As contamination in soil. The average natural contents of As in the non-polluted soils range from 5.5 to 13.0 mg kg 1 according to Bradl (2005); however, arsenic concentrations can reach 40 mg kg 1 in some soils without harming the exposed organisms (Dudka and Miller, 1999). Therefore, depending on the total soil As in referring to As toxicity may result in more conflict conclusions, consequently, the available forms of As can provide more reliable explanations. Ammonium bicarbonate diethylene triamine pentaacetic acid (AB-DTPA) can be used for extracting the available fraction of As (Soltanpour, 1985). It is worthy to mention that high concentrations of As in soils are related mainly to the anthropogenic activities rather than the natural inputs (Fitz and Wenzel, 2002) e.g. the use of inorganic arsenicals as cotton desiccants and of organic arsenicals as herbicides in riceproducing areas (Murphy and Aucott, 1998), the produced water discharges associated with petroleum hydrocarbon recovery operations (Carbonell et al., 1998; Nriagu et al., 2007), and the continuous leaching of As from the areas of treated wood with chromated copper arsenate (CCA) – chemical preservative (Abdelhafez et al., 2009). In Egypt, the industrial activities in El-Gahrbia Governorate such like Soda, Elmaila and pesticide production factories which produce soda and salt, chemicals and pesticides, respectively possess serious problems concerning As pollution in the surrounded areas (El-Gohary, 1990; El Bouraie et al., 2010). Chronic exposure to As can cause severe health problems (Mazumder et al., 1992; Gonzaga et al., 2006) i.e. skin and lung cancer, skin lesions, peripheral neuropathy and anemia (ATSDR, 2009). Food and water consumption is the main ingestion pathway for As by human (Del Razo et al., 2002) and the concentration of As in the edible parts in complete feeding stuffs for animals should not exceed 2 mg kg 1 (European-Commission). The concentration of As in the edible parts of the plants depends on the availability of As in soil, its uptake by plants and its translocation to the edible parts (Huang et al., 2006). The aim of this research is to investigate the effects of applying EDTA to As-polluted soil on As availability in soil, its uptake by maize plants, and its translocation from the root to shoot. Furthermore, this research evaluates the tolerance of maize plants to the elevated concentrations of bioavailable As in soil, and whether these chelates can enhance phytoextraction of As by maize plants. In our study, we avoided the use of EDTA – micronutrient complexes rather than EDTA–NH4 to avoid the interactions that might take place between the soil As and the added nutrient.

2. Materials and methods 2.1. Soil sampling and sites description A sandy clay loam soil sample was collected from the surface layer (0–15 cm) of the soil adjacent to the pesticide factory in ElGharbia Governorate, Egypt. A background soil sample was collected from the nearby control area. The air dried and 2 mm sieved soils were used for analysis of some physical and chemical proper-

589

ties whose results are outlined in Table 1. The concentrations of Cd, Cr, Pb, Ni and Zn of the investigated soil were close to the measured background values and did not exceed the background levels in soil as proposed by Bradl (2005). On the other hand, the concentration of As was 11.2 times higher than the background value of 2.26 mg kg 1 and also exceeded the reference level of As in soil. Therefore, the industrial activities in the area of study could be referred as the main reason for As-pollution in the study location. For the phytoextraction experiment, the As-polluted soil (25.36 mg As kg 1 soil) was thoroughly mixed, air-dried and sieved to pass through a 5 mm diameter sieve and kept for the experimental work. 2.2. The experimental work To initiate a pot experiment, 3.5 kg weight portions of the preprepared soil sample was placed into plastic pots (15 cm diameter and 17.5 cm depth). Three seeds of maize (Zea mays L.) plant were sown in each pot with four replicates for each treatment, and were thinned to two plants after germination. The experiment was carried out between 2nd of May and 27th of June in a greenhouse supported with natural light. Tap water was applied two times per week throughout the two months period of the experiment to maintain the soil moisture content almost constant at 70% of the water holding capacity. The mineral N, P and K fertilizers were applied prior to planting at the recommended rates of the Agricultural Research Center, Egypt. Stock solutions were prepared by dissolving ethylene diamine tetra-acetic acid di-ammonium (EDTA) salt (EDTA–NH4, minimum assay: 99%) in deionized water, and applied to soil at rates of 0.0, 1.0, 2.5 and 5.0 mmol kg 1 four weeks after planting of maize. The selected concentrations of EDTA represent the background levels used in the successful phytoextraction of heavy metals without causing pronounced effects on the biomass of maize shoot or root (Luo et al., 2005; Komárek et al., 2007). 2.3. Analyses 2.3.1. Soil analyses The particle size distribution was determined using the pipette method as described by Akoto et al. (2008). The soil reaction (pH) and electrical conductivity (EC) were determined in 1:1 soil to water suspensions and supernatant, respectively using the method described by Jones (2001). Total organic carbon content was determined using Welkley-Black procedure (Nelson and Sommers, 1996). Extraction of As was conducted twice, the first by distilled water to evaluate the water soluble content of As and the second with ammonium bi-carbonate di-ethylene tri-amine penta-acetic acid (AB-DTPA) to extract the fraction of As that can be considered available. Briefly, 10 g portions of the air dried soil were extracted with 20 mL of AB-DTPA reagent (Soltanpour and Schwab, 1977). To evaluate the total As content, corresponding soil samples were digested in aqua regia (Sabienë et al., 2004), one mL of the soil digest was taken and brought up to 10 mL by a solution containing 10% HCl, 5% ascorbic acid and 10% KI and As determination was carried out using the HG-AAS technique (Perkin Elmer 3300) with a hydride generator system (Perkin Elmer Fias 100), and the detection limit was 0.1 lg L 1. 2.3.2. Plant analyses After eight weeks from sowing (four weeks from EDTA application), the whole plants were removed gently from the soil to avoid root hair damage, washed with tap water then deionized water and separated into shoots and roots. The plant materials were oven dried at 70 °C for approximately 48 h, and the plant dry weights of the shoots and roots of each pot were recorded. Chlorophyll con-

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M.H.H. Abbas, A.A. Abdelhafez / Chemosphere 90 (2013) 588–594

Table 1 Physicochemical properties of the studied soil.

a b

1

Location/natural levels

pH

EC, dS m

Study soil Background soil Average natural contentsb

7.40 ± 0.15 7.70 ± 0.12 –

2.21 ± 0.003 1.85 ± 0.09 –

O.Ma (%)

1.21 ± 0.2 1.05 ± 0.2 –

Total heavy metal concentrations, mg kg

1

Textural class

Cd

Cr

Pb

Ni

Zn

As

0.13 ± 0.1 0.08 ± 0.1 0.1–0.13

3.54 ± 0.6 2.77 ± 0.6 15–78

12.73 ± 2.5 4.55 ± 2.0 2.6–25.0

11.39 ± 2.2 4.55 ± 0.4 1.8–23

33.58 ± 5.3 47.13 ± 8.0 37–67

25.36 ± 3.1 2.26 ± 2.2 5.5–13

Sandy clay loam Sandy clay loam –

Organic matter. Average natural concentration of heavy metals (Bradl, 2005).

tent of the uppermost leaves was measured using SPAD 502 DL Plus meter. The chlorophyll content was measured as an indicator of the physiological status and the possible damage due to EDTA applications and As availability. Samples of oven-dried plant materials were digested using a mixture of concentrated sulfuric acid (10 mL) and perchloric acid (2 mL) according to the procedure described by Chapman and Pratt (1982). The digests were then filtered through a Whatman No. 41 filter paper, 1 mL of the plant digest was taken and brought up to 10 mL by a solution containing 10% HCl, 5% ascorbic acid and 10% KI and analyzed for the total As contents using HG-AAS. 2.3.3. Accumulation and translocation of As in maize plant tissues (shoots and roots) Bioaccumulation factor of the plant roots (BAFroots), defined as the ratio between heavy metal concentrations in roots and ABDTPA extractable form in soil was calculated according to Uchida et al. (2007). Bioaccumulation factor of the plant shoots (BAFshoots), defined as the ratio of total element concentration in shoots to ABDTPA extractable form in soil, both in mg kg 1 and the translocation factor (TF), defined as the total element concentration in shoots with respect to total element concentration in roots, both in mg kg 1 were calculated according to Fitz and Wenzel (2002). 2.3.4. Statistical analysis All results were statistically analyzed using the SAS package (ver. 9.1). Means of four replicates for all chemical and biological analyses were subjected to one way ANOVA. Tukey’s honestly significant difference (HSD) studentised range test was applied for significant differences among means (P < 0.05). Pearson’s correlation coefficients were also performed among various parameters. The graphs were plotted using Sigma Plot 10 program.

ter. Also, plant height was not affected significantly with the used rates of the applied EDTA except for its highest rate of 5.0 mmol kg 1. The application of 1.0 mmol EDTA kg 1 decreased significantly the chlorophyll content (SPAD values) with no significant effect on the other growth parameters, i.e. both root and shoot dry weights. The application of 2.5 mmol EDTA kg 1 decreased significantly the SPAD value and both root and shoot dry weights where the corresponding reductions were about 23.03%, 25.15% and 13.96%, respectively. The highest EDTA application rate (5.0 mmol kg 1) significantly decreased the plant height, SPAD value, roots dry weight and shoots dry weight and the corresponding reductions calculated as percentages of the corresponding control ones were 7.91%, 29.10%, 37.27% and 23.19%, respectively.

3.2. Effect of applying EDTA on soil chemical properties and As availability Table 3 shows selected chemical properties for the soil at the end of the experimental period (8 weeks). The results show that the highest application rates of EDTA (2.5 and 5.0 mmol EDTA kg 1) reduced soil pH significantly; however, the pH remained statistically unaffected in soils that received 1.0 mmol EDTA kg 1. On the other hand, the 5.0 mmol EDTA kg 1 treatment caused the EC values to increase from 2.20 dS m 1 up to 4.29 dS m 1 compared to the control treatment. The soil organic matter content of the EDTA treated soil increased significantly to higher values than those of the control treatment due to organic carbon in EDTA compound. Likewise, the AB-DTPA extractable As increased significantly with increasing the rate of applied EDTA, yet the values of the soluble As did not follow the same trend as the test of significance revealed that the only rate of applied EDTA, which increased soluble As significantly was 5.0 mmol EDTA kg 1.

2.4. Chemicals The chemicals used in this experiment were of analytical grade and were obtained from Merck Company. 3. Results 3.1. The influences of EDTA application on plant growth parameters The results mentioned in Table 2 demonstrate that the different applied rates of EDTA had no significant effect on the stem diame-

3.3. The influence of applied EDTA on As uptake by maize shoots and roots Fig. 1 shows that values of As uptake (lg pot 1) by shoots increased significantly with the increase in the applied EDTA rate. On the other hand, As uptake by roots did not increase significantly except with the highest application rates of EDTA, i.e. 2.5 and 5.0 mmol kg 1. The results also show relatively higher uptake of As by roots than shoots for plants grown in soil received no EDTA or received only 1.0 mmol EDTA kg 1. On the other hand, As uptake

Table 2 Effect of EDTA application on plant growth parameters. Applied rate of EDTA–NH4, mmol kg

1

Plant height (cm)

Stem diameter (mm)

Chlorophyll, SPAD values

Plant dry weight (g pot Root

0.00 1.00 2.5 0 5.00

138.38 132.25 134.25 127.44

a ba ba b

9.67 9.14 9.24 9.18

a a a a

Means with the same letter within a column are not significantly different at p < 0.05.

34.21 27.83 26.33 24.26

a b cb c

3.30 2.75 2.47 2.07

1

) Shoot

a ba b b

17.77 16.44 15.29 13.65

a ba bc c

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M.H.H. Abbas, A.A. Abdelhafez / Chemosphere 90 (2013) 588–594 Table 3 Changes of soil chemical properties as affected by EDTA application. EDTA treatments (mmol kg 0.00 1.00 2.50 5.00

1

)

pH 7.43 7.41 7.36 7.15

EC (dS m a ba b c

2.20 2.64 3.18 4.29

1

)

d c b a

O.M (%)

Water soluble As (lg kg

1.50 1.72 1.84 1.76

130.60 115.40 146.27 161.43

b a a a

b ba ba a

1

)

AB-DTPA extractable As (lg kg 143.66 258.04 441.43 646.91

1

)

d c b a

Means with the same letter within a column are not significantly different at p < 0.05.

by shoots and roots was almost equal after 2.5 mmol kg treatment.

1

3.4. The mutual effects among applied EDTA, soil and plant variables Data presented in Table 4 reveal that AB-DTPA extractable As concentrations showed positive significant correlations with the applied rates of EDTA (p < 0.01). Likewise, positive and significant effects were found for applied rates of EDTA on concentrations of As in shoots and roots (p < 0.01) as well as their As uptake values by both shoots and roots (p < 0.01). On the other hand, EDTA seemed to be of a significant adverse effect on each of root and shoot dry weight with a significantly negative effect of p < 0.01 and p < 0.05, respectively. A highly significant correlation coefficient was established between the AB-DTPA extractable As and each of shoot (p < 0.001) and root (p < 0.01) content of As as well as its uptake values by each of shoot and root (p < 0.01). Contradictory there was no significant correlation between water soluble As and each of root and shoot As contents and uptake as well. Furthermore, concentration of As in shoot was correlated positively and significantly with of its content in the root (p < 0.01). For the plant dry weight, there was a negative significant correlation between AB-DTPA extractable As and each of shoot and root dry weights (p < 0.05). 3.5. Effect of EDTA applications on bioaccumulation factors (BAFs) and translocation factor (TF) of soil As within the maize plant The data shown in Table 5 reveal that the application of EDTA was associated with increases in As concentrations in both shoot and root. The increases seemed more obvious by increasing rate of the applied EDTA. However, it can be noticed that concentration of As in the root upon application of a certain rate of EDTA was far higher than the corresponding one in shoot. Bioaccumulation factor of root (BAFroot) of maize plant decreased with the increase in the applied rate of EDTA and the corresponding reductions were 33.16%, 53.60% and 61.29% for soil treated with 1.0, 2.5 and 5.0 mmol EDTA kg 1, respectively. Similarly, bioaccumulation factor of maize shoot (BAFshoot) decreased with increasing rate of the applied EDTA; however, the decreases were slight and ranged between 9.85% and 15.30%. On the other hand, root–shoot translocation factor (TF) increased with the increase in applied rate of EDTA to soil and the corresponding increases for the applied EDTA treatments, i.e. 1.0, 2.5 and 5.0 mmol EDTA kg 1 were 1.250, 1.750 and 2.125 folds, respectively greater than the control treatment. 4. Discussions The results illustrate the toxic effect of As after EDTA applications on the maize growth. Increasing the rate of applied EDTA to soil raised slightly As uptake by the maize root while enhanced considerably its uptake by maize shoot (Fig. 1). Root biomass reduction is the consequence of increased As uptake due to the high application doses of EDTA (Tables 2 and 3). The higher con-

Fig. 1. Effect of EDTA addition on As uptake by Zea mays L.

centrations of As in roots than in shoots might account for such a finding. Similar results were obtained by Azizur Rahman et al. (2007) who conducted a greenhouse experiment using six As treatments viz. control, 10, 20, 30, 60 and 90 mg of As kg 1 and found that As toxicity affected the photosynthesis which ultimately resulted in the reduction of rice growth and yield. Also, Gulz et al. (2005) found that elevated levels of As inhibited growth of maize, rape, English ryegrass and sunflower plants. Although the increases in soil salinity have negative effects on plant growth (Munns, 2004) including maize plant, which are moderate sensitive (Katerji et al., 2003), but the cultivar used in this study, Giza 2, is a salt tolerant variety. Consequently, the reductions in the biomass of maize shoot and root could mostly be attributed to the specific toxicity of increasing As concentrations in plant tissue rather than the increases in soil salinity resulted from EDTA applications. The decrease in pH values of the EDTA treated soil after 8 weeks of incubation seemed to be more pronounced by increasing rate of the applied EDTA, which means that EDTA has an acidic physiological effect. Several studies have shown that the addition of EDTA significantly decreased soil pH (Heil et al., 1999; Mühlbachová, 2009). The AB-DTPA extractable As increased significantly with increasing the rate of applied EDTA, yet the values of the soluble As did not follow the same trend and slightly changed with either the application of 1.0 or 2.5 mmol EDTA kg 1 and increased significantly only with the application of 5.0 mmol EDTA kg 1. The increase in the solubility of As could be attributed to the decrease in soil pH associated with EDTA application, and these results agree with Signes-Pastor et al. (2007) who showed that the availability of As was pronounced at low soil pH value. Concerning the significant positive correlation between the AB-DTPA extractable As and the applied EDTA, we suggest the occurrence of some linkage between As ions in soil and the di- or polyvalent cations chelated by the applied EDTA. Some studies highlighted the direct effect of the application of EDTA on increasing the stability of As species in Fe rich waters from precipitation in

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M.H.H. Abbas, A.A. Abdelhafez / Chemosphere 90 (2013) 588–594

Table 4 Correlation coefficient values of biological and chemical soil properties related to EDTA–NH4 addition. EDTA addition EDTA addition Water extracted As AB-DTPA extracted As Shoots As contents Roots As contents Shoots As uptake Roots As uptake Shoots dry weight Roots dry weight Soil pH * ** ***

Water extracted As

AB-DTPA extracted As

Shoots As contents

Roots As contents

Shoots As uptake

Roots As uptake

0.86

0.99** 0.86

0.99** 0.86 0.99***

0.99** 0.83 0.99** 0.99**

0.98** 0.85 0.99** 0.99** 0.99**

0.99** 0.9 0.99** 0.99** 0.98** 0.98*

Shoots dry weight 0.98* 0.77 0.98* 0.98* 0.99** 0.98* 0.97*

Roots dry weight 0.93** 0.71 0.96* 0.95* 0.96* 0.97* 0.91 0.96*

Soil pH 0.96* 0.85 0.93 0.93 0.93 0.90 0.96* 0.93 0.81

P < 0.05. P < 0.01. P < 0.001.

the form of Fe oxides and hydroxides for long periods of time exceeding 14 d (Gallagher et al., 2001), or 75 d (Gallagher et al., 2004), and these results confirm the presence of direct complexation between arsenic species and EDTA. According to Thanabalasingam and Pickering (1986), calcium (Ca) or other polyvalent cations chelated by EDTA might be involved in As retention. Increasing the rate of the applied EDTA to soil led to consequent increases in As uptake by shoots while As uptake by plant roots was relatively lower (Fig. 1). The reductions in the root biomass recorded with the high application doses of EDTA were the main reason for the slight increases in the calculated values of As uptake by plant roots. In general, our results highlight the chemical effects of applying EDTA amendment on increasing the availability of arsenic in As-polluted soils and the consequent physiological reductions in the different parameters of plant growth. These results confirm those obtained by Azizur Rahman et al. (2011) who mentioned that the application of EDTA caused considerable increases in As uptake in rice shoot and that the application of EDTA fertilizers to agricultural soils contaminated with As should be considered carefully. The positive correlations detected between AB-DTPA extractable As and its uptake values by each of shoots and roots assure the pronounced effect of bioavailable As rather than its total content on As uptake by maize plants. Sadiq (1986) and Gulz et al. (2005) found that the values of As uptake by some plants, i.e. maize, rape, English rye grass and sunflower after four months of growth were highly correlated with soluble As. However, the concentrations of water soluble arsenic were small fractions of the total content (Girouard and Zagury, 2009; Rodrigues et al., 2010), which might not account for the physiological reductions in maize growth and uptake. Depending on the AB-DTPA extractable As rather than water soluble As in referring to As uptake and its toxicity for maize plant, the related correlation study (Table 4) revealed highly significant correlation between the uptake of As by plant root/shoot with the AB-DTPA extractable As compared with the soluble As. Therefore, the AB-DTPA extractable As was used in this study to calculate the bioaccumulation factors of maize root (BAFroot) and shoot (BAFshoot) and the translocation factor (TF) as indicates for investigating the tolerance of maize plants

for As and its feasibility for the induced phytoextration of As from soil. Bioaccumulation factors of maize root (BAFroot) and shoot (BAFshoot) decreased with the increase in the applied rates of EDTA, which might be resulted from the concurrent increase in the extractability of AB-DTPA-As in soil accompanied by the increased application rates of EDTA. On the other hand, the calculated values of the root–shoot translocation factor increased with the increased rate of applied EDTA, and such results indicate that the ability of roots to sequester As was low and effective only in the presence of low bioavailable As, while the presence of high concentrations of extractable As resulted in an increase in the amount of As transferred from roots to shoots. Concerning the calculated values of the BAFshoot of maize plants, they decreased with the increase in applied rate of EDTA to soil, and these results agree with those of Gulz et al. (2005) who found that As translocation from the maize root to shoots was insignificant. According to Baker and Walker (1990), As excluders prevent the translocation of As to the areal parts of the plant. In spite of the results which indicate that As is found in high concentrations in maize roots exceeding its concentrations in shoots, the high translocations of As from root-to-shoot, which were detected with increasing the rate of applied EDTA indicate that maize cannot be classified as As excluder. It is also worthy to mention that the shoots of the maize plants that grew in As-polluted soil, which did not receive EDTA could be used in animal feeding as the level of As in shoots did not exceed 2.0 mg As kg 1, which is the safely acceptable limit of arsenic in complete feeding stuffs proposed by the European-Commission (2003). On the other hand, the roots of maize plants should be kept away from composting or animal feeding; otherwise, the removed As will return back to soil or take part in the food chain and consequently, there will be a potential threat for plant and humans. Phytoextraction is considered the best approach to remove the contaminants primarily from soil and isolate them, without destroying it (Ghosh and Singh, 2005). The pollutant-accumulating plants should extract the contaminants and translocate them to the harvestable parts (Fitz and Wenzel, 2002). Common crop plants with high biomass are good candidates for accumulating vast

Table 5 Bioaccumulation factors of maize root (BAFroot) and shoot (BAFshoot) and translocation factor (TF). EDTA treatments, mmol kg

0.00 1.00 2.50 5.00

1

As conc. (lg g

1

)

Roots

Shoot

17.89 21.48 25.51 31.18

1.37 2.22 3.67 5.23

BAFroots

BAFshoots

TF

124.53 83.24 57.79 48.20

9.54 8.60 8.31 8.08

0.08 0.10 0.14 0.17

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amounts of metals when their availability in soils was enhanced by chemical chelating agents (Chiu et al., 2005), and this remediation is needed to clean polluted soils, and to ensure the safe soil use. Our results indicate that maize plants cannot be considered hyperaccumulators for As according to Fitz and Wenzel (2002), who mentioned that the plants exhibit root–shoot translocation factor <1 cannot be considered as candidates for phytoextraction. Even if we harvested the whole plants from the soil, the maximum total amount of As that might be extracted from 3.5 kg soil by maize plants would be 0.136 mg recorded for the highest application rate of EDTA (5.0 mmol kg 1). Such amount of As removed from soil does not exceed 0.04 mg kg 1, which means that this soil needs a very long time for the induced phytoextraction to reduce the concentrations of As in soil to more acceptable limits. 5. Conclusions Application of EDTA to soil increased As availability and its uptake by the roots and shoots of maize plant. In the presence of relatively lower concentrations of available As in soil, sequestering of As in roots took place to minimize its translocation from roots to shoots. Also, the long pathway of As translocation from roots to shoots plus sequestering As in stem tissues might also serve in As detoxification in shoots. Therefore, maize shoots were expected to respond slightly to As toxicity in the presence of low available As in soil. However, the increase in the availability of As in soil resulted in a consequent increase in the amount of As transferred from roots to shoots and consequently, the chlorophyll content was affected significantly with As toxicity. The values of root– shoot translocation factor of maize plants indicate that the induced phytoextraction of As by maize plants needs long time-periods to reach more acceptable levels of total As in soil. However, maize shoots grown in As-polluted soils received no EDTA treatments could be used in animal feeding. For As fractions, the obtained results showed that bioavailable fraction of As is important to investigate the uptake and accumulations of As in the plant tissues. Acknowledgements The authors would like to express their thanks to Soils, Water and Environment Research Institute (SWERI) members, and to Prof. H.H. Ramadan, Soils Department, Benha University, Egypt for their profitable helps with this study. References Abdelhafez, A.A., Awad, Y.M., Kim, M.S., Ham, K.J., Lim, K.J., Joo, J.H., Yang, J.E., Ok, Y.S., 2009. Environmental monitoring of heavy metals and arsenic in soils adjacent to CCA-treated wood structures in Gangwon Province South Korea. Korean J. Environ. Agric. 28, 340–346. Akoto, O.J., Ephraim, J.H., Darko, J., 2008. Heavy metals pollution in surface soils in the vicinity of abundant railway servicing workshop in Kumasi Ghana. Int. J. Environ. Res. 2, 359–364. ATSDR. 2009. Case Studies in Environmental Medicine –Arsenic Toxicity. Resource Document. US Department of Health and Human, Environmental Medicine and Educational Services Branch. (accessed 1.10.2009). Azizur Rahman, M., Hasegawa, H., MahfuzurRahman, M., NazrulIslam, M., MajidMiah, M.A., Tasmen, A., 2007. Effect of arsenic on photosynthesis, growth and yield of five widely cultivated rice (Oryza sativa L.) varieties in Bangladesh. Chemosphere 67, 1072–1079. http://dx.doi.org/10.1016/ j.chemosphere.2006.11.061. Azizur Rahman, M., MamunurRahman, M., Kadohashi, K., Maki, T., Hasegawa, H., 2011. Effect of external iron and arsenic species on chelant-enhanced iron bioavailability and arsenic uptake in rice (Oryza sativa L.). Chemosphere 84, 439–445. http://dx.doi.org/10.1016/j.chemosphere.2011.03.046. Baker, A.J.M., Walker, P.L., 1990. Ecophysiology of metal uptake by tolerant plants. In: Shaw, A.J. (Ed.), Heavy Metal Tolerance in Plants: Evolutionary Aspects. CRC Press, Boca Raton, pp. 155–177. Bell, P.F., McLaughlin, M.J., Cozens, G., Stevens, D.P., Owens, G., South, H., 2003. Plant uptake of 14C-EDTA, 14C-Citrate, and 14C-Histidine from chelator-buffered and

593

conventional hydroponic solutions. Plant Soil 253, 311–319. http://dx.doi.org/ 10.1023/A:1024836032584. Bradl, H.B., 2005. Heavy Metals in the Environment: Origin, Interaction and Remediation, first ed. Elsevier Academic Press, London. Carbonell, A.A., Aarabi, M.A., DeLaune, R.D., Gambrell, R.P., Patrick Jr, W.H., 1998. Arsenic in wetland vegetation: availability, phytotoxicity, uptake and effects on plant growth and nutrition. Sci. Total Environ. 217, 189–199. http://dx.doi.org/ 10.1016/S0048-9697(98)00195-8. Chapman, H.D., Pratt, F.P., 1982. Methods of Analysis for Soils, Plants and Water, second ed. Agriculture Division, California University, Oakland, CA. Chiu, K.K., Ye, Z.H., Wong, M.H., 2005. Enhanced uptake of As, Zn, and Cu by Vetiveria zizanioides Zea mays using chelating agents. Chemosphere 60, 1365–1375. http://dx.doi.org/10.1016/j.chemosphere.2005.02.035. Del Razo, L.M., Garcia-Vargas, G.G., Garcia-Salcedo, J., Sanmiguel, M.F., Rivera, M., Hernandez, M.C., Cebrian, M.E., 2002. Arsenic levels in cooked food and assessment of adult dietary intake of arsenic in the Region Lagunera, Mexico. Food Chem. Toxicol. 40, 1423–1431. http://dx.doi.org/10.1016/S02786915(02)00074-1. Dudka, S., Miller, W.P., 1999. Permissible concentrations of arsenic and lead in soils based on risk assessment. Water, Air, Soil Pollut 113, 127–132. http:// dx.doi.org/10.1023/A:1005028905396. El Bouraie, M.M., El Barbary, A.A., Yehia, M.M., Motawea, E.A., 2010. Heavy metal concentrations in surface river water and bed sediments at nile delta in Egypt – research notes. Suo 61, 1–12. El-Gohary, F.A., 1990. Waste water management in Shubra El-Kheima. Second Egyptian Seminar on Industrial Waste Water Management, Cairo, Egypt, 1–21 (April 4–6). European-Commission. 2003. Opinion of the scientific committee on animal nutrition on undesirable substances in feed. Resource document. Health & Consumer Protection Directorate-General. (accessed 28.03.2003). Fitz, W.J., Wenzel, W.W., 2002. Arsenic transformations in the soil-rhizosphereplant system: fundamentals and potential application to phytoremediation. J. Biotechnol. 99, 259–278. http://dx.doi.org/10.1016/S0168-1656(02)00218-3. Gallagher, P.A., Schwegel, C.A., Wei, X., Creed, J.T., 2001. Speciation and preservation of inorganic arsenic in drinking water sources using EDTA with IC separation and ICP-MS detection. J. Environ. Monit. 3, 371–376. http://dx.doi.org/10.1039/ B101658J. Gallagher, P.A., Schwegel, C.A., Parks, A., Gamble, B.M., Wymer, L., Creed, J.T., 2004. Preservation of As(III) and As(V) in drinking water supply samples from across the United States using EDTA and acetic acid as a means of minimizing iron arsenic coprecipitation. Environ. Sci. Technol. 38, 2919–2927. http:// dx.doi.org/10.1021/es035071n. Ghosh, M., Singh, S.P., 2005. A review on phytoremediation of heavy metals and utilization of its byproducts. Appl. Ecol. Environ. Res. 3, 1–18. Girouard, E., Zagury, G.J., 2009. Arsenic bioaccessibility in CCA-contaminated soils: influence of soil properties, arsenic fractionation, and particle-size fraction. Sci. Total Environ. 407, 2576–2585. http://dx.doi.org/10.1016/j.scitotenv.2008.12. 019. Gonzaga, M.I.S., Santos, J.A.G., Ma, L.Q., 2006. Arsenic phytoextraction and hyperaccumulation by fern species. Sci. Agric. 63, 90–101. http://dx.doi.org/ 10.1590/S0103-90162006000100015. Grcˇman, H., Velikonja-Bolta, Š., Vodnik, D., Kos, B., Leštan, D., 2001. EDTA enhanced heavy metal phytoextraction: metal, accumulation leaching and toxicity. Plant Soil 235, 105–114. http://dx.doi.org/10.1023/A:1011857303823. Gregori, I.D., Fuentes, E., Olivares, D., Pinochet, H., 2004. Extractable copper, arsenic and antimony by EDTA solution from agricultural Chilean soils and its transfer to alfalfa plants (Medicago sativa L.). J. Environ. Monit. 6, 38–47. http:// dx.doi.org/10.1039/B304840C. Gucht, I.V., 1994. Determination of chelating agents in fertilizers by ion chromatography. J. Chromatogr. A. 671, 359–365. http://dx.doi.org/10.1016/ 0021-9673(94)80261-0. Gulz, P.A., Gupta, S.K., Schulin, R., 2005. Arsenic accumulation of common plants from contaminated soils. Plant Soil 272, 337–347. http://dx.doi.org/10.1007/ s11104-004-5960-z. Heil, D.M., Samani, Z., Hanson, A.T., Rudd, B., 1999. Remediation of lead contaminated soil by EDTA. I. Batch and column studies. Water, Air, Soil Pollut. 113, 77–95. http://dx.doi.org/10.1023/A:1005032504487. Hong, P.K.A., Li, C., Banerji, S.K., Regmi, T., 1999. Extraction, recovery, and biostability of EDTA for remediation of heavy metal-contaminated soil. Soil Sediment Contam. 8, 81–103. http://dx.doi.org/10.1080/10588339991339243. Hovsepyan, A., Greipsson, S., 2005. EDTA-enhanced phytoremediation of leadcontaminated soil by corn. J. Plant Nutr. 28, 2037–2048. http://dx.doi.org/ 10.1080/01904160500311151. Huang, R.Q., Gao, S.F., Wang, W.L., Staunton, S., Wang, G., 2006. Soil arsenic availability and the transfer of soil arsenic to crops in suburban areas in fujian province, southeast China. Sci. Total Environ. 368, 531–541. http://dx.doi.org/ 10.1016/j.scitotenv.2006.03.013. Jones, J.B., 2001. Laboratory Guide for Conducting Soils Tests and Plant Analysis. CRC Press, New York. Katerji, N., van Hoorn, J.W., Hamdy, A., Mastrorilli, M., 2003. Salinity effect on crop development and yield, analysis of salt tolerance according to several classification methods. Agric. Water Manage. 62, 37–66. http://dx.doi.org/ 10.1016/S0378-3774(03)00005-2. Komárek, M., Tlustoš, P., Száková, J., Chrastny´, V., Ettler, V., 2007. The use of maize and poplar in chelant-enhanced phytoextraction of lead from contaminated

594

M.H.H. Abbas, A.A. Abdelhafez / Chemosphere 90 (2013) 588–594

agricultural soils. Chemosphere 67, 640–651. http://dx.doi.org/10.1016/ j.chemosphere.2006.11.010. Luo, C., Shen, Z., Li, X., 2005. Enhanced phytoextraction of Cu, Pb, Zn and Cd with EDTA and EDDS. Chemosphere 59, 1–11. http://dx.doi.org/10.1016/j. chemosphere.2004.09.100. Mansilla, H.D., Bravoa, C., Ferreyra, R., Litter, M.I., Jardim, W.F., Lizama, C., Freer, J., Fern´andez, J., 2006. Photocatalytic EDTA degradation on suspended and immobilized TiO2. J. Photochem. Photobiol. A 181, 188–194. http://dx.doi.org/ 10.1016/j.jphotochem.2005.11.023. Mazumder, D., Das Gupta, J., Chakraborty, A., Chakraborti, D., 1992. Environmental pollution and chronic arsenicosis in south Calcutta. Bull World Health Org. 70, 481–485. Mühlbachová, G., 2009. Microbial biomass C dynamics and heavy metal mobility in long-term contaminated soils after amendment with chelates. In: 6th International Symposium on Ecosystem Behaviour. Biogeomon, Helsinki, Finland (29June–3July). Munns, R., 2004. Salinity, Growth and Phytohormones. In: Läuchli, A., Lüttge, U. (Eds.), Salinity: Environment – Plants – Molecules, Springer Netherlands, pp. 271–290. Murphy, E.A., Aucott, M., 1998. An assessment of the amounts of arsenical pesticides used historically in a geographical area. Sci. Total Environ. 218, 89– 101. http://dx.doi.org/10.1016/S0048-9697(98)00180-6. Nelson, D.W., Sommers, L.E., 1996. Total carbon, organic carbon, and organic matter. In: Page, A.L. (Ed.), Methods of Soil Analysis Part 3, second ed. American Society of Agronomy, Madison, WI, pp. 961–1010. Nriagu, J.O., Bhattacharya, P., Mukherjee, A.B., Bundschuh, J., Zevenhoven, R., Loeppert, R.H., 2007. Arsenic in soil and groundwater: an overview. In: Nriagu, J.O. (Ed.), Trace Metals and other Contaminants in the Environment, Elsevier, pp. 3–60. Oviedo, C., Rodríguez, J., 2003. EDTA: the chelating agent under environmental scrutiny. Química Nova. 26, 901–905. http://dx.doi.org/10.1590/S010040422003000600020. Park, J.Y., Kim, K.W., Kim, J.Y., Lee, B.T., Lee, J.S., Bae, B.H., 2008. Enhanced phytoremediation by echinochloafrumentacea Using PSM and EDTA in an arsenic contaminated soil. In: Pisutha-Arnond, V. (Ed.), The International Symposia on Geoscience Resources and Environments of Asian Terranes, 4th IGCP 516, and 5th APSEG. Bangkok, Thailand, pp. 487–488 (November 24–26). Rahman, M.A., Hasegawa, H., Ueda, K., Maki, T., Rahman, M.M., 2008. Influence of EDTA and chemical species on arsenic accumulation in Spirodelapolyrhiza L. (duckweed). Ecotoxicol. Environ. Safe. 70, 311–318. http://dx.doi.org/10.1016/ j.ecoenv.2007.07.009.

Rashid, A., Ryan, J., 2004. Micronutrient constraints to crop production in soils with mediterranean-type characteristics: a review. J. Plant Nutr. 27, 959–975. http:// dx.doi.org/10.1081/PLN-120037530. Rodrigues, S.M., Heniriques, B., Coimbra, J., Ferreira da Silva, E., Pereira, M.E., Duarte, A.C., 2010. Water-soluble fraction of mercury, arsenic and other potentially toxic elements in highly contaminated sediments and soils. Chemosphere 78, 1301–1312. http://dx.doi.org/10.1016/j.chemosphere.2010.01.012. Sabienë, N., Brazauskienë, D.M., Rimmer, D., 2004. Determination of heavy metals mobile forms by different extraction methods. Ekologija 163, 51–59. Sadiq, M., 1986. Solubility relationships of arsenic in calcareous soils and its uptake by corn. Plant Soil 91, 241–248. http://dx.doi.org/10.1007/BF02181791. Signes-Pastor, A., Burló, F., Mitra, K., Carbonell-Barrachina, A.A., 2007. Arsenic biogeochemistry as affected by phosphorus fertilizer addition, redox potential and pH in a west Bengal (India) soil. Geoderma 137, 504–510. http://dx.doi.org/ 10.1016/j.geoderma.2006.10.012. Soltanpour, P.N., 1985. Use of ammonium bicarbonate DTPA soil test to evaluate elemental availability and toxicity. Commun. Soil Sci. Plant Anal. 16, 323–338. http://dx.doi.org/10.1080/00103628509367607. Soltanpour, P.N., Schwab, A.P., 1977. A new soil test for simultaneous extraction of macro- and micro-nutrients in alkaline soils. Commun. Soil Sci. Plant Anal. 8, 195–207. http://dx.doi.org/10.1080/00103627709366714. Tandy, S., Bossart, K., Mueller, R., Ritschek, J., Hauser, L., Chulian, R., Nowack, B., 2004. Extraction of heavy metals from soils using biodegradable chelating agents. Environ. Sci. Technol. 38, 937–944. http://dx.doi.org/10.1021/ es0348750. Thanabalasingam, P., Pickering, W.F., 1986. Arsenic sorption by humic acids. Environ. Pollut. B 12, 233–246. http://dx.doi.org/10.1016/0143-148X(86)90012-1. Uchida, S., Tagami, K., Hirai, I., 2007. Soil-to-plant transfer factors of stable elements and naturally occurring radionuclides: (2) rice collected in Japan. J. Nucl. Sci. Technol. 44, 779–790. http://dx.doi.org/10.1080/18811248.2007.9711867. Vaxevanidou, K., Papassiopi, N., Paspaliaris, I., 2008. Removal of heavy metals and arsenic from contaminated soils using bioremediation and chelant extraction techniques. Chemosphere 70, 1329–1337. http://dx.doi.org/10.1016/j. chemosphere.2007.10.025. Wang, J., Wang, X., Li, G., Guo, P., Luo, Z., 2010. Degradation of EDTA in aqueous solution by using ozonolysis and ozonolysis combined with sonolysis. J. Hazard. Mater. 176, 333–338. http://dx.doi.org/10.1016/j.jhazmat.2009.11.032. Wu, L.H., Luo, Y.M., Xing, X.R., Christie, P., 2004. EDTA-enhanced phytoremediation of heavy metal contaminated soil with Indian mustard and associated potential leaching risk. Agric. Ecosyst. Environ. 102, 307–318. http://dx.doi.org/10.1016/ j.agee.2003.09.002.