- Email: [email protected]
Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil
Journal of Environmental Management xxx (2016) 1e8
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil € rg Rinklebe b Sabry M. Shaheen a, b, *, Jo a b
University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33 516, Kafr El-Sheikh, Egypt University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285, Wuppertal, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 February 2016 Received in revised form 16 July 2016 Accepted 18 July 2016 Available online xxx
The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (EH) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CSþSBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (13 mV) to oxidizing (þ519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CSþSBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CSþSBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CSþSBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CSþSBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Agro-environmental management Liming materials release kinetics Toxic metals Redox processes Wetlands
1. Introduction Soil contamination with toxic metals (TMs) has become a global concern because of its adverse effects on ecosystem health and food security (Antoniadis et al., 2016). The increasing demand for new and costly processes for the immobilization of TMs in contaminated soils has led many researchers to investigate the possibility of using waste materials for metal immobilization (Bolan et al., 2014). Recently, many studies have focused on the development of nonconventional alternative immobilizing agents and amendments produced from low-cost resources which can be used for the
* Corresponding author. University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33 516, Kafr El-Sheikh, Egypt. E-mail addresses: [email protected] (S.M. Shaheen), [email protected] (J. Rinklebe).
remediation of TMs contaminated soils (Ok et al., 2011; Shaheen and Rinklebe, 2015; Soares et al., 2015) and waters (Akunwa et al., 2014; Shaheen et al., 2013). One of the low-cost sorbents is sugar beet factory lime (SBFL). Sugar beet factories have traditionally stockpiled factory lime near them which is produced during the sugar beet juice purification process. This factory lime meets the definition of a liming product and can be used for remediation of metal contaminated soils and waters (Dutton and Huijbregts, 2006). The SBFL is expected to be more efficient in immobilization of TMs compared to other liming materials such as limestone due to its alkalinity and finer texture (Shaheen et al., 2015). Additionally, no attempt has been made to assess the effects of SBFL to immobilize TMs under controlled redox conditions. Recent studies have highlighted the role of SBFL in immobilization of TMs in soils (Shaheen and Rinklebe, 2015; Shaheen et al.,
http://dx.doi.org/10.1016/j.jenvman.2016.07.060 0301-4797/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
2
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
2015). However, these studies investigated the impact of SBFL on the (im)mobilization of TMs in soils under static soil moisture conditions. Floodplain soils are frequently flooded and highly dynamic; thus, soil redox potential (EH), pH, and governing factors such as iron (Fe), manganese (Mn), dissolved organic carbon (DOC), sulphate (SO2 4 ) and others differ significantly compared to field capacity conditions. These highly dynamic conditions have considerable impacts on the release dynamics of TMs in soils (Frohne et al., 2011; Shaheen et al., 2014, 2016a,b). Detailed knowledge about the redox-induced behavior of TMs in contaminated floodplain soils treated with SBFL and compared with non-treated soil is required for a better understanding of the mobilization of TMs and their controlling processes. This knowledge enables a more accurate prediction of metal release into ground- and surface waters in response to changing redox conditions which might contribute to develop an adequate risk assessment and management of contaminated floodplain soils. Thus, we aimed to assess the impact of SBFL on the mobilization and release dynamics of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb), and zinc (Zn) under dynamic redox conditions in a highly contaminated floodplain soil treated with SBFL and non-treated. The obtained results will be an aid to verify the scientific hypotheses that the liming material SBFL is able to immobilize toxic metals in floodplain soils under different redox conditions. In addition the obtained results will help to quantify the impact of pre-definite EH-conditions on the release dynamics and mobilization of TMs in the SBFL treated soils. Moreover, these results could serve as a precondition for the development of innovative technologies for management of wetland soils aimed at avoiding pollutant exposure to plants, water, soil, and riverine ecosystems.
Table 1 Properties and element concentrations (microwave digestion2) of contaminated soil (CS) and sugar beet factory lime (SBFL).
2. Materials and methods
2.2. Experiment under pre-set redox conditions
2.1. Collection, characterization, and treatment of the soil and SBFL
An automated biogeochemical microcosm system was exploited to simulate flooding of the contaminated soil (CS) and contaminated soil þ sugar beet factory lime (CSþSBFL) in laboratory. This system was successfully employed in previous studies (Frohne et al., 2011; Rinklebe et al., 2016a,b; Shaheen et al., 2014, 2016a,b). Technical details are provided in (Yu and Rinklebe, 2011) and specifics in Supplemental 1.
The soil sample was collected from a floodplain at the lower course of the Wupper River, Germany (E 2570359, N 5661521; 5140 0.4800 N, 6 40 0.4800 E). The site is used as grassland and periodically flooded by the Wupper River, usually in spring time. The soil is classified as Eutric Fluvisol according to (IUSS-FAO, 2014). Major properties of the soil and SBFL are presented in Table 1. Soil texture was dominated by silt. The soil was weakly acidic and contained high organic carbon. The soil has elevated total content of the elements. Total concentration of the studied elements in the soil was 6.0, 20.4, 490.3, 2433.4, 6.8, 80.9, 412.0, and 1050.1 mg kg1 for Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn, respectively. The total metal concentrations exceeded the precautionary values of the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV, 1999). Moreover, the values of Cd, Cr, Cu, Pb, and Zn were higher than the upper limit of the trigger action values for TMs in agricultural soils as reported by Kabata-Pendias (2011), implying harmful soil alterations which need remediation. High total content of TMs in the studied soil may be due to the contamination of the water and sediments of Wupper River originate from anthropogenic activities (Frohne et al., 2011). The SBFL was obtained from the Delta sugar beet factory in ElHamoul, Kafr El-Sheikh governorate, Egypt. The SBFL was alkaline (pH ¼ 8.7), contained high amounts of total carbonates (82.5%), total sulfur (S), aluminium (Al), Fe, and contained low concentrations of TMs (Table 1). The SBFL was applied to the soil at a rate of 10 g kg1 soil. Soil and SBFL were mixed thoroughly and thereafter a pot experiment was conducted (Shaheen and Rinklebe, 2015; Shaheen et al., 2015). Thereafter, the soil was dried, crushed, and incubated in the laboratory for ten months. Thus, the total
Unit
CSa 6.4
8.70
Silt Clay Total nitrogen Total carbon Total carbonates Concentrationse Cd Co Cr Cu Mo Ni Pb Zn
[%]
92.0 2.00 0.35 7.10 b.d.l.
n.d.d n.d. n.d. n.d. 82.5
[mg kg1]
6.9 20.4 490.3 2433.4 6.83 80.9 412.0 1050.1
b.d.l.f b.d.l. 9.96 7.43 b.d.l. 3.60 b.d.l. 14.03
Al Fe Mn S
[g kg1]
18.5 43.8 0.87 0.99
1.71 0.85 0.08 2.03
Basic properties pH [H2O]c
a b c d e f
SBFLb
CS: contaminated soil. SBFL: sugar beet factory lime. pH determined according to DIN EN 15933 (2012). n.d. ¼ not determined. According to US EPA 3051a (2007). b.d.l. ¼ below detection limit.
incubation period was about one year before the soil was used for the experiment.
2.3. Calculations and statistical analysis Mean values of EH and pH levels for 3, 6, 12, and 24 h prior to sampling were calculated. The original values measured every 10 min served as the underlying dataset. Correlation analyses were conducted between EH/pH and concentrations of DOC, SO2 4 , Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn. The results 6 h before sampling generally resulted in closest correlations and were therefore used for statistics. The program IBM SPSS Statistics, Version 22 was used for conducting correlations and descriptive analysis. 3. Results and discussion 3.1. Soil EH, pH, DOC, Fe, Mn, and SO2 4 The minimum, maximum, and mean values of soil EH and pH in CS and in CSþSBFL are presented in Table 2. The relationships between EH and pH with DOC, Fe, Mn, and SO2 4 are presented in Figs. 1 and 2, respectively. The EH values ranged between þ74 and þ503 mV in CS and between 13 and þ519 mV in CSþSBFL. The pH values ranged between 4.0 and 6.9 in CS and between 4.4 and 7.5 in CSþSBFL. Soil pH shows an opposite behavior to EH (Fig. 1). Therefore, the relation between soil EH and pH was negative
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
3
Table 2 Variations of concentrations of elements, compounds, as well as redox potential (EH) and pH in the slurry of the contaminated soil (CS) and of the contaminated soil plus sugar beet factory lime (CSþSBFL) during the experiment. Parameter
EH
a
Unit
[mV]
pHa
Contaminated soil þ sugar beet factory lime
Contaminated soil N
Minimum
Maximum
Mean
N
Minimum
Maximum
Mean
21
74
503
303
21
13
519
298
21
4.0
6.9
5.7
21
4.4
7.5
5.8
DOCb SO24 Fe Mn
[mg l1]
21 19 21 21
1197.5 7.2 2.1 6.8
5509.2 20.3 104.7 64.0
2994.3 14.1 29.3 26.6
21 21 21 21
1023 10.2 0.59 3.7
3566 43.9 47.6 53.0
2031.95 20.9 18.5 28.3
Cd Co Cr Cu Mo Ni Pb Zn
[mg l1]
18 21 21 21 21 21 20 21
0.34 34.1 22.2 2040.1 13.7 38.6 5.3 213.1
185.8 788.2 3203.8 85313.5 95.4 1502.8 744.4 34135.9
64.2 275.8 817.9 23809.4 40.3 444.5 218.3 9783.6
21 21 21 21 21 21 21 21
2.8 26.1 1.7 774.5 25.5 42.8 29.3 67.7
133.5 569.2 1314.4 35831.1 78.3 674.7 178.1 16263.9
63.6 259.8 347.3 11621.2 47.3 266.5 84.9 5360.5
a b
Means of data 6 h before sampling. DOC: dissolved organic carbon.
(R2 ¼ 0.62 in CS and R2 ¼ 0.59 in CSþSBFL; Fig. 1). An increase of pH with a decline in EH might be due to the consumption of protons 4þ 3þ required for the reduction of NO (Frohne et al., 3 , Mn , and Fe 2011; Yu et al., 2007). The results indicate that application of SBFL to the soil increased pH in soil slurry (pH maximum) from 6.9 in CS to 7.5 in CSþSBFL which is considered to be a significant reason for the decreased solubility and release of the TMs in CSþSBFL compared to CS. Concentrations of DOC decreased with rising EH in CS; therefore, the relation between DOC with EH was negative in CS (R2 ¼ 0.65; Fig. 1). However, the relation between DOC with pH was positive in CS (R2 ¼ 0.56; Fig. 2). On other hand, in CSþSBFL, the DOC showed an inconsistent trend with EH and pH (non-significant relation; Figs. 1 and 2). The increase of DOC under reducing conditions in CS might be due to the release of organic matter bound to reductively dissolved Fe oxyhydroxides (Shaheen et al., 2014) and/or production of soluble organic metabolites by reducing bacteria (Rinklebe et al., 2016a). Under reducing conditions, complex organic matter is degraded to DOC by reductive fermentation and hydrolysis (Shaheen et al., 2016a). A decrease in DOC with increasing EH occurs due to enhanced microbial carbon consumption at higher EH (Shaheen et al., 2014), which might also have happened in our experiment. The concentrations of Fe and Mn in CS and CSþSBFL were significantly higher under oxic and acidic than under reducing conditions with higher pH (Figs. 1 and 2). Therefore, the relations between Fe and Mn on one hand and EH on the other hand were positive (Fig. 1), while relations between both elements with pH were negative in CS and in CSþSBFL (Fig. 2). An increase of soluble Fe and Mn concentrations due to reductive dissolution under low EH is commonly observed in soils (e.g., Frohne et al., 2011; Shaheen et al., 2014). However, in our experiment, the concentrations of dissolved Fe and Mn increased under high EH very likely due to the associate decrease of pH (Figs. 1 and 2). Thus, Fe seems to be dominant in dissolved form under pH values ranged from 4 to 6 in our prevailing experiment (Fig. 2). A pH of 6 is dominant at the beginning of our experiment, this would require an EH of approximately 200 mV for significant Fe oxidation (and linked formation of Fe oxides/hydroxides) (Takeno, 2005). However, we measured an EH of about 100 mV at the first sampling. Thus, it is likely that a certain amount of Fe occur as Fe2þ here. Similar behavior can be observed for Mn; this phenomenon was already reported by Frohne et al. (2011). When rising the EH the linked decrease of pH (4.0e4.4)
favors the mobilization and release of Fe and Mn even under oxic conditions in both systems, CS and CSþSBFL. The results indicate that application of SBFL to the soil decreased Fe and Mn in soil slurry (maximum) from 104.7 in CS to 47.6 mg L1 in CSþSBFL for Fe and from 64.0 in CS to 53.0 mg L1 in CSþSBFL for Mn, which is considered to be a significant reason for the increased pH in CSþSBFL as compared to CS (Fig. 1; Table 2). The mean concentrations of SO2 4 in CSþSBFL were higher than in CS (Table 2), which might be due to the high concentrations of total sulfur (2.03 g kg1) in SBFL (Table 1), what leads to the assumption that SBFL increased the release of SO2 4 to soil solution. Concentrations of SO2 4 decreased with rising EH in CS; however, the SO2 4 showed an inconsistent trend with EH in the CSþSBFL (Fig. 1), and with pH in CS and in CSþSBFL (Fig. 2). Therefore, the 2 relation between SO2 4 with EH was negative in CS (R ¼ 0.34; Fig. 1), but this relation was non-significant in CSþSBFL (Fig. 1). 3.2. Impact of EH/pH changes on mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn showed wide ranges during the experiment (Table 2 and Fig. 3), which might be in response to changes of EH/pH. Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn were significantly higher under oxic and acidic than under reducing conditions with higher pH in CS and in CSþSBFL (Fig. 4). Therefore, the relations between Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn and EH were positive in CS and in CSþSBFL (Fig. 3), while the relations between the same elements (except Mo in the CSþSBFL) and pH were negative in CS and in CSþSBFL (Fig. 4). The low mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under reducing conditions as compared to oxidizing conditions might be explained by changes of controlling factors such as pH, DOC, Fe, Mn, and SO2 4 . The combined effects of pH and EH on the mobilization of metals are complex and highly metal-specific. The decrease of pH from 6.9 to 7.5 under reducing conditions to 4.0e4.4 under oxidizing conditions seem to lead to the increased mobilization and release of Cd, Co, Cr, Cu, Ni, Pb, and Zn under oxic conditions in both, CS and CSþSBFL (Figs. 3 and 4). Soil pH affects oxidationereduction of metals and solubility of metal compounds in soils, since Hþ is a reactant in redox reactions. The increasing of TMs solubility under acidic conditions is well documented (Hooda, 2010). This is because a low pH in soil-water systems tends to
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
4
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
Fig. 1. Relationship between EH in the soil suspension vs. pH, concentrations of DOC, Fe, Mn, and SO2 4 in CS and in CSþSBFL (n ¼ 21).
favor the formation of soluble species of many elements; whereas in nonacidic systems, slightly soluble or insoluble forms tend to be predominant (Kabata-Pendias, 2011). The relationships between dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn in one side and DOC, Fe, Mn, and SO2 4 in other side are presented in Supplemental 2. The dissolved concentrations of all elements correlated negatively with DOC in CS; however, these relations were nonsignificant in CSþSBFL. The negative correlations between the elements and DOC in CS indicate that the DOC followed an opposite behavior compared to the elements (Figs. 1 and 3) and might affect the solubility and release of these elements to soil solution in CS higher than in CSþSBFL. On the other hand, dissolved concentrations of all elements correlated positively with Fe and Mn both in CS and in CSþSBFL (Supplemental 2). The positive relations between Fe and Mn in one hand and Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn in other hand in both systems, CS and CSþBC show that release of these elements under dynamic redox conditions are relatively similar.
The systematic increase of EH along with decrease of pH might be responsible for the mobilization of Fe, Mn and the elements in CS and in CSþSBFL. 3.3. Impact of SBFL on mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn The impact of SBFL on the mobilization of the studied elements differed based on the element, EH, and pH values. Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in soil solution differed widely between CS and CSþSBFL (Table 2; Fig. 3). In general, concentrations of mean values of dissolved Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn in CSþSBFL were lower than in CS (Table 2 and Fig. 3). The mean values of the elements in soil solution of CSþSBFL were considerably decreased by 61.1% for Pb, 57.5% for Cr, 51.2% for Cu, 45.2% for Zn, 40.0% for Ni, 36.9% for Fe, 5.8% for Co, and by 0.95% for Cd as compared to CS. Mean concentrations of Mn and Mo showed an
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
5
Fig. 2. Relationship between pH in the soil suspension vs. concentrations of DOC, Fe, Mn, and SO2 4 in CS and in CSþSBFL (n ¼ 21).
opposite trend and were higher in CSþSBFL than in CS by 6.4% and 17.4%, respectively (Table 2). Specifically, the minimal concentrations of dissolved Cd, Mo, Ni, and Zn were higher in CSþSBFL than in CS; however, the maximum values showed an opposite behavior and were higher in CS than in CSþSBFL (Table 2; Fig. 3). Fig. 3 showed that the EH values were lower in CSþSBFL (13 mV) than in CS (þ119 mV) at the first sampling; therefore, concentrations of these elements were high in CSþSBFL at the first sampling under low EH and neutral pH (6.7e7.1) (Figs. 3 and 4). However, at the last sampling, the pH decreased significantly to 4.0e4.2 in CS and to 4.4e5.1 in CSþSBFL. Therefore, the mobilization of these elements increased at the end of the experiment (last two samplings) under high oxic and acidic conditions both in CS and in CSþSBFL (Figs. 3 and 4). However, the maximal concentrations of these elements were higher in CS than in CSþSBFL because the pH values were relatively lower in CS (4.0) than in CSþSBFL (5.1) at the end of the experiment (Fig. 4). A higher mobilization of Cd, Co, Mn, Mo, Ni, and Zn in the CSþSBFL as compared to the CS especially at the first samplings (Fig. 3) might be explained by the precipitation of these elements (especially Cd) as carbonates (total carbonates in SBFL ¼ 82.5%; Table 1) under the neutral conditions. Then, dissolving the carbonates and release the precipitate metal again in soluble form under the acidic conditions during the experiment might be happened (Shaheen and Rinklebe, 2015). Higher mean concentrations of dissolved Mo under CSþSBFL as compared to CS (Table 2; Fig. 3) might be explained by the relatively increase of pH in CSþSBFL as compared to CS. Molybdenum differs from the other elements in occurring as an oxyanion or hydroxyanion, that is as negatively charged species, in soil solution except for very acidic conditions (pH < 5), where it occurs as molybdic acid. As a consequence, sorption decreases and mobility increases with increasing pH in contrast to trace elements that occur as
cations (Evans and Barabash, 2010). Molybdenum is retained by soils under acidic conditions, principally on the surfaces of variablecharge minerals, such as the Fe oxides. The sorption of molybdate anions to soils occurs under acidic conditions, decreasing rapidly after pH 5, and is essentially complete at pH 8 (Akiyoshi and Hisashi, 2004). Copper, Zn, Pb, Cr, and Ni which were highly enriched in our soil (Table 1) showed the highest decreasing rate in CSþSBFL (40e61%) compared to CS. These results highlight that SBFL is able to act as an immobilizing agent to reduce the concentrations of dissolved Cr, Cu, Ni, Pb, and Zn in this highly contaminated soil under dynamic redox conditions. Immobilizing mechanisms have mainly been attributed to the increase in pH, carbonates and phosphates content, and therefore, sorption/stabilization of metals (Shaheen et al., 2015; Shaheen and Rinklebe, 2015). Firstly, the higher pH in CSþSBFL compared to CS induces element immobilization because it favors precipitation of Cr, Cu, Ni, Pb, and Zn, decreases its solubility and promotes sorption and precipitation of these elements (Hooda, 2010; McBride, 1994). The higher pH in CSþSBFL compared to CS might have enhanced the hydrolysis of metals or even precipitation of metals as hydroxides (Sparks, 2003). Secondly, CSþSBFL have received substantial input of carbonates (82.5%; Table 1) via SBFL; in consequence precipitation and sorption of element increase (Shaheen et al., 2015; Shaheen and Rinklebe, 2015). Thirdly, the high immobilization rate of the metals by SBFL especially Pb (61.1%) in CSþSBFL as compared to CS could be explained by its high concentrations of phosphates (Sims et al., 2010). Reducing the mobilization of Pb in (Pb)-contaminated soils via phosphate amendments to sequester the Pb as pyromorphite [Pb5(PO4)3X, where X ¼ Cl, OH, or F] has been extensively studied (Bolan et al., 2014; Du et al., 2014; Hettiarachchi et al., 2001; Ryan et al., 2001). Selective sequential extraction procedures have determined speciation of Pb in phosphate-amended
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
6
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
Fig. 3. Relationships between EH in the soil suspension vs. concentrations of dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in CS and in CSþSBFL (n ¼ 21).
soils and reported that a substantial portion of the soil-Pb was transformed to pyromorphite [Pb5(PO4)3X, where X ¼ Cl, OH, or F] in phosphate-amended soils as evident by an increase of Pb
concentration in the residual fraction relative to a control (Cao et al., 2004; Scheckel et al., 2005). Thus, those results suggested that SBFL amendment could significantly reduce the mobilization
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
7
Fig. 4. Relationships between pH in the soil suspension vs. concentrations of dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in CS and in CSþSBFL (n ¼ 21).
and increase the geochemical stability of Pb in a contaminated floodplain soil. Our results demonstrate that mobilization of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn was lower under low EH and neutral/ weakly acidic conditions at the binging of the experiment than under high oxic and acidic conditions at the end of the experiment
in CS and in CSþSBFL. However, the mean concentrations of these elements (except for Mo and Mn) were higher in CS than in CSþSBFL because the pH values were relatively lower in CS than in CSþSBFL at the end of the experiment, which indicate that the pH is a crucial factor to control the mobilization of the elements in our soil.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
8
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
4. Conclusion Our results conclude that under prevailing acid conditions the systematic increase of EH along with reverse decrease of pH favors the mobilization of the studied elements in both systems, CS and CSþ SBFL. The application of SBFL to the floodplain soil might lead to a decreased release of Cu, Cr, Pb, and Fe under changing redox conditions in highly dynamic floodplain ecosystems. Thus, SBFL is able to decrease mobilization of Cu, Cr, Pb, and Fe in comparison to non-treated CS and might be used as an effective immobilizing agent for these elements even under dynamic redox conditions. The SBFL is an effective immobilizing agent for Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, SBFL mobilized these elements under reducing neutral conditions. This might be worth proving under field conditions with view to an adequate remediation option aiming to minimize the potential risk to humans and environment. For a better understanding of mobilization processes of metals, similar studies should be conducted with a variety of wetland soils around the world. In future, it will be challenging to determine different metal species in the dissolved and colloidal fraction as well as in soil-sediments of the amended floodplain soil under dynamic redox conditions which is important for an appropriate risk assessment. Acknowledgments We thank the German Academic Exchange Foundation (Deutscher Akademischer Austauschdienst, DAAD) (GERSS Fellowship; Code number A1291166 and WAP program; Code number A/14/05113); the Egyptian Science and Technology Development Fund (STDF-STF; Project ID: 5333), and the German Alexander von Humboldt Foundation (Ref 3.4 e EGY e 1185373 e GF-E) for financial support of the postdoctoral scholarships of Prof. Shaheen at the University of Wuppertal, Germany. The authors thank Dr. T. Frohne, Mr. F. Beckers, Mrs. M. Ehlert, Mrs. J. Mihajlovic, and Mr. C. Vandenhirtz (University of Wuppertal, Germany) for technical assistance. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jenvman.2016.07.060. References Akiyoshi, S., Hisashi, S., 2004. Adsorption characteristics of molybdenum on various soils and incorporation into soil organic matter. Jap. J. Soil Sci. Pl. Nutr. 75, 179e184. Akunwa, N.K., Muhammad, M.N., Akunna, J.C., 2014. Treatment of metalcontaminated wastewater: a comparison of low-cost biosorbents. J. Environ. Manag. 146, 517e523. Antoniadis, V., Shaheen, S.M., Boersch, J., Frohne, T., Du Laing, G., Rinklebe, J., 2016. Bioavailability and risk assessment of potentially toxic elements in garden edible vegetables and soils around a highly contaminated former mining area in Germany. J. Environ. Manag. http://dx.doi.org/10.1016/j.jenvman.2016.04.036. BBodSchV, 1999. Bundes-Bodenschutz- und Altlastenverordnung (BBodSchV) vom 12. Juli 1999. Bundesgesetzblatt I 1999, 1554. Federal Soil Protection and Contaminated Sites Ordinance dated 12 July 1999. Bolan, N., Kunhikrishnan, A., Thangarajan, R., Kumpiene, J., Park, J., Makino, T., Kirkham, M.B., Scheckel, K., 2014. Remediation of heavy metal(loid)s contaminated soils - to mobilize or to immobilize? (Review). J. Hazard. Mater. 266, 141e166. Cao, X.D., Ma, L.Q., Rhue, D.R., Appel, C.S., 2004. Mechanisms of lead, copper and zinc retention by phosphate rock. Environ. Pollut. 131, 435e444.
DIN EN 15933, 2012. Schlamm, behandelter Bioabfall und Boden e Bestimmung des pH-Werts. In: Deutsches Institut für Normung. Du, Y.-J., Wei, M.L., Reddy, K.R., Jin, F., Wu, H.-L., Liu, Z.-B., 2014. New phosphatebased binder for stabilization of soils contaminated with heavy metals: leaching, strength and microstructure characterization. J. Environ. Manag. 146, 179e188. Dutton, J., Huijbregts, T., 2006. Root quality and processing. In: Draycott, A.P. (Ed.), Sugar Beet. Blackwell Publishing LTD, Oxford. UK, pp. 409e442. Evans, L.J., Barabash, S.J., 2010. Molybdenum and vanadium. In: Hooda, P.S. (Ed.), Trace Elements in Soils. John Wiley & Sons Ltd, United Kingdom, pp. 347e381. Frohne, T., Rinklebe, J., Diaz-Bone, R.A., Du Laing, G., 2011. Controlled variation of redox conditions in a floodplain soil: impact on metal mobilization and biomethylation of arsenic and antimony. Geoderma 160, 414e424. Hettiarachchi, G.M., Pierzynski, G.M., Ransom, M.D., 2001. In situ stabilization of soil lead using phosphorus. J. Environ. Qual. 30, 1214e1221. Hooda, P.S., 2010. Trace Elements in Soils, first ed. John Wiley & Sons Ltd, PO19 8SQ, United Kingdom. IUSS-FAO, 2014. World Reference Base for Soil Resources. FAO, Rome. Kabata-Pendias, A., 2011. Trace Elements in Soils and Plants. CRC Press, Boca Raton. McBride, M.B., 1994. Environmental Chemistry of Soils. Oxford Univ. Press, New York. Ok, Y.S., Lim, J.E., Moon, D.H., 2011. Stabilization of Pb and Cd contaminated soils and soil quality improvements using waste oyster shells. Environ. Geochem. Health 33, 83e91. € ter, F., Rennert, T., 2016b. Exploiting biogeoRinklebe, J., Shaheen, S.M., Schro chemical and spectroscopic techniques to assess the geochemical distribution and release dynamics of chromium and lead in a contaminated floodplain soil. Chemosphere 150, 390e397. Rinklebe, J., Shaheen, S.M., Yu, K., 2016a. Release of As, Ba, Cd, Cu, Pb, and Sr under pre-definite redox conditions in different rice paddy soils originating from the U.S.A. and Asia. Geoderma 270, 21e32. Ryan, J.A., Zhang, P.C., Hesterberg, D., Chou, J., Sayers, D.E., 2001. Formation of chloropyromorphite in a lead-contaminated soil amended with hydroxyapatite. Environ. Sci. Technol. 35, 3798e3803. Scheckel, K.G., Ryan, J.A., Allen, D., Lescano, N.V., 2005. Determining speciation of Pb in phosphate-amended soils: method limitations. Sci. Total Environ. 350, 261e272. Shaheen, S.M., Frohne, T., White, J., DeLaune, R., Rinklebe, J., 2016b. Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: a better understanding of biogeochemical processes for safe environmental management. J. Environ. Manag. http://dx.doi.org/10.1016/j.jenvman.2016.05.032. Shaheen, S.M., Rinklebe, J., Frohne, T., White, J., DeLaune, R., 2016a. Redox effects on release kinetics of arsenic, cadmium, cobalt, and vanadium in Wax Lake Deltaic soils. Chemosphere 150, 740e748. Shaheen, S.M., Eissa, F., Ghanem, K.M., Gamal El-Din, H., Al-Anany, F., 2013. Heavy metals removal from aqueous solutions and wastewaters by using various byproducts. J. Environ. Manag. 128, 514e521. Shaheen, S.M., Rinklebe, J., 2015. Impact of emerging and low cost alternative amendments on the (im)mobilization and phytoavailability of Cd and Pb in a contaminated floodplain soil. Ecol. Eng. 74, 319e326. Shaheen, S.M., Rinklebe, J., Rupp, H., Meissner, R., 2014. Temporal dynamics of pore water concentrations of Cd, Co, Cu, Ni, and Zn and their controlling factors in a contaminated floodplain soil assessed by undisturbed groundwater lysimeters. Environ. Pollut. 191, 223e231. Shaheen, S.M., Rinklebe, J., Selim, H.M., 2015. Impact of various amendments on the bioavailability and immobilization of Ni and Zn in a contaminated floodplain soil. Int. J. Environ. Sci. Technol. 12, 2765e2776. Sims, A.L., Windels, C.E., Bradley, C.A., 2010. Content and potential availability of selected nutrients in field applied sugar beet factory lime. Commun. Soil Sci. Plan. 41, 438e453. Soares, M.A.R., Quina, M.J., Quinta-Ferreira, R.M., 2015. Immobilisation of lead and zinc in contaminated soil using compost derived from industrial eggshell. J. Environ. Manag. 164, 137e145. Sparks, D.L., 2003. Environmental Soil Chemistry, second ed. Academic Press, New York, NY, USA. Takeno, N., 2005. National Institute of Advanced Industrial Science and Technology (Atlas of Eh-pH diagrams. Geological Survey of Japan Open File Report. Takeno, Naoto). U.S. Environmental Protection Agency, 2007. Microwave Assisted Acid Digestion of Sediments, Sludges, Soils, and Oils, vol. 3051A. Yu, K.W., Bohme, F., Rinklebe, J., Neue, H.U., DeLaune, R.D., 2007. Major biogeochemical processes in soils e a microcosm incubation from reducing to oxidizing conditions. Soil Sci. Soc. Am. J. 71, 1406e1417. Yu, K.W., Rinklebe, J., 2011. Advancement in soil microcosm apparatus for biogeochemical research. Ecol. Eng. 37, 2071e2075.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Research article
Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil € rg Rinklebe b Sabry M. Shaheen a, b, *, Jo a b
University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33 516, Kafr El-Sheikh, Egypt University of Wuppertal, Soil- and Groundwater-Management, Pauluskirchstraße 7, 42285, Wuppertal, Germany
a r t i c l e i n f o
a b s t r a c t
Article history: Received 18 February 2016 Received in revised form 16 July 2016 Accepted 18 July 2016 Available online xxx
The impact of sugar beet factory lime (SBFL) on the release dynamics and mobilization of toxic metals (TMs) under dynamic redox conditions in floodplain soils has not been studied up to date. Therefore, the aim of this study was to verify the scientific hypothesis that SBFL is able to immobilize Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn under different redox potentials (EH) in a contaminated floodplain soil. For this purpose, the non-treated contaminated soil (CS) and the same soil treated with SBFL (CSþSBFL) were flooded in the laboratory using a highly sophisticated automated biogeochemical microcosm apparatus. The experiment was conducted stepwise from reducing (13 mV) to oxidizing (þ519 mV) soil conditions. Soil pH decreased under oxic conditions in CS (from 6.9 to 4.0) and in CSþSBFL (from 7.5 to 4.4). The mobilization of Cu, Cr, Pb, and Fe were lower in CSþSBFL than in CS under both reducing/neutral and oxic/acidic conditions. Those results demonstrate that SBFL is able to decrease concentrations of these elements under a wide range of redox and pH conditions. The mobilization of Cd, Co, Mn, Mo, Ni, and Zn were higher in CSþSBFL than in CS under reducing/neutral conditions; however, these concentrations showed an opposite behavior under oxic/acidic conditions and were lower in CSþSBFL than in CS. We conclude that SBFL immobilized Cu, Cr, Pb, and Fe under dynamic redox conditions and immobilized Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, the latter elements were mobilized under reducing neutral conditions in the studied soil. Therefore, the addition of SBFL to acid floodplain soils contaminated with TMs might be an important alternative for ameliorating these soils with view to a sustainable management of these soils. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Agro-environmental management Liming materials release kinetics Toxic metals Redox processes Wetlands
1. Introduction Soil contamination with toxic metals (TMs) has become a global concern because of its adverse effects on ecosystem health and food security (Antoniadis et al., 2016). The increasing demand for new and costly processes for the immobilization of TMs in contaminated soils has led many researchers to investigate the possibility of using waste materials for metal immobilization (Bolan et al., 2014). Recently, many studies have focused on the development of nonconventional alternative immobilizing agents and amendments produced from low-cost resources which can be used for the
* Corresponding author. University of Kafrelsheikh, Faculty of Agriculture, Department of Soil and Water Sciences, 33 516, Kafr El-Sheikh, Egypt. E-mail addresses: [email protected] (S.M. Shaheen), [email protected] (J. Rinklebe).
remediation of TMs contaminated soils (Ok et al., 2011; Shaheen and Rinklebe, 2015; Soares et al., 2015) and waters (Akunwa et al., 2014; Shaheen et al., 2013). One of the low-cost sorbents is sugar beet factory lime (SBFL). Sugar beet factories have traditionally stockpiled factory lime near them which is produced during the sugar beet juice purification process. This factory lime meets the definition of a liming product and can be used for remediation of metal contaminated soils and waters (Dutton and Huijbregts, 2006). The SBFL is expected to be more efficient in immobilization of TMs compared to other liming materials such as limestone due to its alkalinity and finer texture (Shaheen et al., 2015). Additionally, no attempt has been made to assess the effects of SBFL to immobilize TMs under controlled redox conditions. Recent studies have highlighted the role of SBFL in immobilization of TMs in soils (Shaheen and Rinklebe, 2015; Shaheen et al.,
http://dx.doi.org/10.1016/j.jenvman.2016.07.060 0301-4797/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
2
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
2015). However, these studies investigated the impact of SBFL on the (im)mobilization of TMs in soils under static soil moisture conditions. Floodplain soils are frequently flooded and highly dynamic; thus, soil redox potential (EH), pH, and governing factors such as iron (Fe), manganese (Mn), dissolved organic carbon (DOC), sulphate (SO2 4 ) and others differ significantly compared to field capacity conditions. These highly dynamic conditions have considerable impacts on the release dynamics of TMs in soils (Frohne et al., 2011; Shaheen et al., 2014, 2016a,b). Detailed knowledge about the redox-induced behavior of TMs in contaminated floodplain soils treated with SBFL and compared with non-treated soil is required for a better understanding of the mobilization of TMs and their controlling processes. This knowledge enables a more accurate prediction of metal release into ground- and surface waters in response to changing redox conditions which might contribute to develop an adequate risk assessment and management of contaminated floodplain soils. Thus, we aimed to assess the impact of SBFL on the mobilization and release dynamics of cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb), and zinc (Zn) under dynamic redox conditions in a highly contaminated floodplain soil treated with SBFL and non-treated. The obtained results will be an aid to verify the scientific hypotheses that the liming material SBFL is able to immobilize toxic metals in floodplain soils under different redox conditions. In addition the obtained results will help to quantify the impact of pre-definite EH-conditions on the release dynamics and mobilization of TMs in the SBFL treated soils. Moreover, these results could serve as a precondition for the development of innovative technologies for management of wetland soils aimed at avoiding pollutant exposure to plants, water, soil, and riverine ecosystems.
Table 1 Properties and element concentrations (microwave digestion2) of contaminated soil (CS) and sugar beet factory lime (SBFL).
2. Materials and methods
2.2. Experiment under pre-set redox conditions
2.1. Collection, characterization, and treatment of the soil and SBFL
An automated biogeochemical microcosm system was exploited to simulate flooding of the contaminated soil (CS) and contaminated soil þ sugar beet factory lime (CSþSBFL) in laboratory. This system was successfully employed in previous studies (Frohne et al., 2011; Rinklebe et al., 2016a,b; Shaheen et al., 2014, 2016a,b). Technical details are provided in (Yu and Rinklebe, 2011) and specifics in Supplemental 1.
The soil sample was collected from a floodplain at the lower course of the Wupper River, Germany (E 2570359, N 5661521; 5140 0.4800 N, 6 40 0.4800 E). The site is used as grassland and periodically flooded by the Wupper River, usually in spring time. The soil is classified as Eutric Fluvisol according to (IUSS-FAO, 2014). Major properties of the soil and SBFL are presented in Table 1. Soil texture was dominated by silt. The soil was weakly acidic and contained high organic carbon. The soil has elevated total content of the elements. Total concentration of the studied elements in the soil was 6.0, 20.4, 490.3, 2433.4, 6.8, 80.9, 412.0, and 1050.1 mg kg1 for Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn, respectively. The total metal concentrations exceeded the precautionary values of the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV, 1999). Moreover, the values of Cd, Cr, Cu, Pb, and Zn were higher than the upper limit of the trigger action values for TMs in agricultural soils as reported by Kabata-Pendias (2011), implying harmful soil alterations which need remediation. High total content of TMs in the studied soil may be due to the contamination of the water and sediments of Wupper River originate from anthropogenic activities (Frohne et al., 2011). The SBFL was obtained from the Delta sugar beet factory in ElHamoul, Kafr El-Sheikh governorate, Egypt. The SBFL was alkaline (pH ¼ 8.7), contained high amounts of total carbonates (82.5%), total sulfur (S), aluminium (Al), Fe, and contained low concentrations of TMs (Table 1). The SBFL was applied to the soil at a rate of 10 g kg1 soil. Soil and SBFL were mixed thoroughly and thereafter a pot experiment was conducted (Shaheen and Rinklebe, 2015; Shaheen et al., 2015). Thereafter, the soil was dried, crushed, and incubated in the laboratory for ten months. Thus, the total
Unit
CSa 6.4
8.70
Silt Clay Total nitrogen Total carbon Total carbonates Concentrationse Cd Co Cr Cu Mo Ni Pb Zn
[%]
92.0 2.00 0.35 7.10 b.d.l.
n.d.d n.d. n.d. n.d. 82.5
[mg kg1]
6.9 20.4 490.3 2433.4 6.83 80.9 412.0 1050.1
b.d.l.f b.d.l. 9.96 7.43 b.d.l. 3.60 b.d.l. 14.03
Al Fe Mn S
[g kg1]
18.5 43.8 0.87 0.99
1.71 0.85 0.08 2.03
Basic properties pH [H2O]c
a b c d e f
SBFLb
CS: contaminated soil. SBFL: sugar beet factory lime. pH determined according to DIN EN 15933 (2012). n.d. ¼ not determined. According to US EPA 3051a (2007). b.d.l. ¼ below detection limit.
incubation period was about one year before the soil was used for the experiment.
2.3. Calculations and statistical analysis Mean values of EH and pH levels for 3, 6, 12, and 24 h prior to sampling were calculated. The original values measured every 10 min served as the underlying dataset. Correlation analyses were conducted between EH/pH and concentrations of DOC, SO2 4 , Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn. The results 6 h before sampling generally resulted in closest correlations and were therefore used for statistics. The program IBM SPSS Statistics, Version 22 was used for conducting correlations and descriptive analysis. 3. Results and discussion 3.1. Soil EH, pH, DOC, Fe, Mn, and SO2 4 The minimum, maximum, and mean values of soil EH and pH in CS and in CSþSBFL are presented in Table 2. The relationships between EH and pH with DOC, Fe, Mn, and SO2 4 are presented in Figs. 1 and 2, respectively. The EH values ranged between þ74 and þ503 mV in CS and between 13 and þ519 mV in CSþSBFL. The pH values ranged between 4.0 and 6.9 in CS and between 4.4 and 7.5 in CSþSBFL. Soil pH shows an opposite behavior to EH (Fig. 1). Therefore, the relation between soil EH and pH was negative
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
3
Table 2 Variations of concentrations of elements, compounds, as well as redox potential (EH) and pH in the slurry of the contaminated soil (CS) and of the contaminated soil plus sugar beet factory lime (CSþSBFL) during the experiment. Parameter
EH
a
Unit
[mV]
pHa
Contaminated soil þ sugar beet factory lime
Contaminated soil N
Minimum
Maximum
Mean
N
Minimum
Maximum
Mean
21
74
503
303
21
13
519
298
21
4.0
6.9
5.7
21
4.4
7.5
5.8
DOCb SO24 Fe Mn
[mg l1]
21 19 21 21
1197.5 7.2 2.1 6.8
5509.2 20.3 104.7 64.0
2994.3 14.1 29.3 26.6
21 21 21 21
1023 10.2 0.59 3.7
3566 43.9 47.6 53.0
2031.95 20.9 18.5 28.3
Cd Co Cr Cu Mo Ni Pb Zn
[mg l1]
18 21 21 21 21 21 20 21
0.34 34.1 22.2 2040.1 13.7 38.6 5.3 213.1
185.8 788.2 3203.8 85313.5 95.4 1502.8 744.4 34135.9
64.2 275.8 817.9 23809.4 40.3 444.5 218.3 9783.6
21 21 21 21 21 21 21 21
2.8 26.1 1.7 774.5 25.5 42.8 29.3 67.7
133.5 569.2 1314.4 35831.1 78.3 674.7 178.1 16263.9
63.6 259.8 347.3 11621.2 47.3 266.5 84.9 5360.5
a b
Means of data 6 h before sampling. DOC: dissolved organic carbon.
(R2 ¼ 0.62 in CS and R2 ¼ 0.59 in CSþSBFL; Fig. 1). An increase of pH with a decline in EH might be due to the consumption of protons 4þ 3þ required for the reduction of NO (Frohne et al., 3 , Mn , and Fe 2011; Yu et al., 2007). The results indicate that application of SBFL to the soil increased pH in soil slurry (pH maximum) from 6.9 in CS to 7.5 in CSþSBFL which is considered to be a significant reason for the decreased solubility and release of the TMs in CSþSBFL compared to CS. Concentrations of DOC decreased with rising EH in CS; therefore, the relation between DOC with EH was negative in CS (R2 ¼ 0.65; Fig. 1). However, the relation between DOC with pH was positive in CS (R2 ¼ 0.56; Fig. 2). On other hand, in CSþSBFL, the DOC showed an inconsistent trend with EH and pH (non-significant relation; Figs. 1 and 2). The increase of DOC under reducing conditions in CS might be due to the release of organic matter bound to reductively dissolved Fe oxyhydroxides (Shaheen et al., 2014) and/or production of soluble organic metabolites by reducing bacteria (Rinklebe et al., 2016a). Under reducing conditions, complex organic matter is degraded to DOC by reductive fermentation and hydrolysis (Shaheen et al., 2016a). A decrease in DOC with increasing EH occurs due to enhanced microbial carbon consumption at higher EH (Shaheen et al., 2014), which might also have happened in our experiment. The concentrations of Fe and Mn in CS and CSþSBFL were significantly higher under oxic and acidic than under reducing conditions with higher pH (Figs. 1 and 2). Therefore, the relations between Fe and Mn on one hand and EH on the other hand were positive (Fig. 1), while relations between both elements with pH were negative in CS and in CSþSBFL (Fig. 2). An increase of soluble Fe and Mn concentrations due to reductive dissolution under low EH is commonly observed in soils (e.g., Frohne et al., 2011; Shaheen et al., 2014). However, in our experiment, the concentrations of dissolved Fe and Mn increased under high EH very likely due to the associate decrease of pH (Figs. 1 and 2). Thus, Fe seems to be dominant in dissolved form under pH values ranged from 4 to 6 in our prevailing experiment (Fig. 2). A pH of 6 is dominant at the beginning of our experiment, this would require an EH of approximately 200 mV for significant Fe oxidation (and linked formation of Fe oxides/hydroxides) (Takeno, 2005). However, we measured an EH of about 100 mV at the first sampling. Thus, it is likely that a certain amount of Fe occur as Fe2þ here. Similar behavior can be observed for Mn; this phenomenon was already reported by Frohne et al. (2011). When rising the EH the linked decrease of pH (4.0e4.4)
favors the mobilization and release of Fe and Mn even under oxic conditions in both systems, CS and CSþSBFL. The results indicate that application of SBFL to the soil decreased Fe and Mn in soil slurry (maximum) from 104.7 in CS to 47.6 mg L1 in CSþSBFL for Fe and from 64.0 in CS to 53.0 mg L1 in CSþSBFL for Mn, which is considered to be a significant reason for the increased pH in CSþSBFL as compared to CS (Fig. 1; Table 2). The mean concentrations of SO2 4 in CSþSBFL were higher than in CS (Table 2), which might be due to the high concentrations of total sulfur (2.03 g kg1) in SBFL (Table 1), what leads to the assumption that SBFL increased the release of SO2 4 to soil solution. Concentrations of SO2 4 decreased with rising EH in CS; however, the SO2 4 showed an inconsistent trend with EH in the CSþSBFL (Fig. 1), and with pH in CS and in CSþSBFL (Fig. 2). Therefore, the 2 relation between SO2 4 with EH was negative in CS (R ¼ 0.34; Fig. 1), but this relation was non-significant in CSþSBFL (Fig. 1). 3.2. Impact of EH/pH changes on mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn showed wide ranges during the experiment (Table 2 and Fig. 3), which might be in response to changes of EH/pH. Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn were significantly higher under oxic and acidic than under reducing conditions with higher pH in CS and in CSþSBFL (Fig. 4). Therefore, the relations between Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn and EH were positive in CS and in CSþSBFL (Fig. 3), while the relations between the same elements (except Mo in the CSþSBFL) and pH were negative in CS and in CSþSBFL (Fig. 4). The low mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under reducing conditions as compared to oxidizing conditions might be explained by changes of controlling factors such as pH, DOC, Fe, Mn, and SO2 4 . The combined effects of pH and EH on the mobilization of metals are complex and highly metal-specific. The decrease of pH from 6.9 to 7.5 under reducing conditions to 4.0e4.4 under oxidizing conditions seem to lead to the increased mobilization and release of Cd, Co, Cr, Cu, Ni, Pb, and Zn under oxic conditions in both, CS and CSþSBFL (Figs. 3 and 4). Soil pH affects oxidationereduction of metals and solubility of metal compounds in soils, since Hþ is a reactant in redox reactions. The increasing of TMs solubility under acidic conditions is well documented (Hooda, 2010). This is because a low pH in soil-water systems tends to
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
4
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
Fig. 1. Relationship between EH in the soil suspension vs. pH, concentrations of DOC, Fe, Mn, and SO2 4 in CS and in CSþSBFL (n ¼ 21).
favor the formation of soluble species of many elements; whereas in nonacidic systems, slightly soluble or insoluble forms tend to be predominant (Kabata-Pendias, 2011). The relationships between dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn in one side and DOC, Fe, Mn, and SO2 4 in other side are presented in Supplemental 2. The dissolved concentrations of all elements correlated negatively with DOC in CS; however, these relations were nonsignificant in CSþSBFL. The negative correlations between the elements and DOC in CS indicate that the DOC followed an opposite behavior compared to the elements (Figs. 1 and 3) and might affect the solubility and release of these elements to soil solution in CS higher than in CSþSBFL. On the other hand, dissolved concentrations of all elements correlated positively with Fe and Mn both in CS and in CSþSBFL (Supplemental 2). The positive relations between Fe and Mn in one hand and Cd, Co, Cr, Cu, Mo, Ni, Pb, Zn in other hand in both systems, CS and CSþBC show that release of these elements under dynamic redox conditions are relatively similar.
The systematic increase of EH along with decrease of pH might be responsible for the mobilization of Fe, Mn and the elements in CS and in CSþSBFL. 3.3. Impact of SBFL on mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn The impact of SBFL on the mobilization of the studied elements differed based on the element, EH, and pH values. Concentrations of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in soil solution differed widely between CS and CSþSBFL (Table 2; Fig. 3). In general, concentrations of mean values of dissolved Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn in CSþSBFL were lower than in CS (Table 2 and Fig. 3). The mean values of the elements in soil solution of CSþSBFL were considerably decreased by 61.1% for Pb, 57.5% for Cr, 51.2% for Cu, 45.2% for Zn, 40.0% for Ni, 36.9% for Fe, 5.8% for Co, and by 0.95% for Cd as compared to CS. Mean concentrations of Mn and Mo showed an
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
5
Fig. 2. Relationship between pH in the soil suspension vs. concentrations of DOC, Fe, Mn, and SO2 4 in CS and in CSþSBFL (n ¼ 21).
opposite trend and were higher in CSþSBFL than in CS by 6.4% and 17.4%, respectively (Table 2). Specifically, the minimal concentrations of dissolved Cd, Mo, Ni, and Zn were higher in CSþSBFL than in CS; however, the maximum values showed an opposite behavior and were higher in CS than in CSþSBFL (Table 2; Fig. 3). Fig. 3 showed that the EH values were lower in CSþSBFL (13 mV) than in CS (þ119 mV) at the first sampling; therefore, concentrations of these elements were high in CSþSBFL at the first sampling under low EH and neutral pH (6.7e7.1) (Figs. 3 and 4). However, at the last sampling, the pH decreased significantly to 4.0e4.2 in CS and to 4.4e5.1 in CSþSBFL. Therefore, the mobilization of these elements increased at the end of the experiment (last two samplings) under high oxic and acidic conditions both in CS and in CSþSBFL (Figs. 3 and 4). However, the maximal concentrations of these elements were higher in CS than in CSþSBFL because the pH values were relatively lower in CS (4.0) than in CSþSBFL (5.1) at the end of the experiment (Fig. 4). A higher mobilization of Cd, Co, Mn, Mo, Ni, and Zn in the CSþSBFL as compared to the CS especially at the first samplings (Fig. 3) might be explained by the precipitation of these elements (especially Cd) as carbonates (total carbonates in SBFL ¼ 82.5%; Table 1) under the neutral conditions. Then, dissolving the carbonates and release the precipitate metal again in soluble form under the acidic conditions during the experiment might be happened (Shaheen and Rinklebe, 2015). Higher mean concentrations of dissolved Mo under CSþSBFL as compared to CS (Table 2; Fig. 3) might be explained by the relatively increase of pH in CSþSBFL as compared to CS. Molybdenum differs from the other elements in occurring as an oxyanion or hydroxyanion, that is as negatively charged species, in soil solution except for very acidic conditions (pH < 5), where it occurs as molybdic acid. As a consequence, sorption decreases and mobility increases with increasing pH in contrast to trace elements that occur as
cations (Evans and Barabash, 2010). Molybdenum is retained by soils under acidic conditions, principally on the surfaces of variablecharge minerals, such as the Fe oxides. The sorption of molybdate anions to soils occurs under acidic conditions, decreasing rapidly after pH 5, and is essentially complete at pH 8 (Akiyoshi and Hisashi, 2004). Copper, Zn, Pb, Cr, and Ni which were highly enriched in our soil (Table 1) showed the highest decreasing rate in CSþSBFL (40e61%) compared to CS. These results highlight that SBFL is able to act as an immobilizing agent to reduce the concentrations of dissolved Cr, Cu, Ni, Pb, and Zn in this highly contaminated soil under dynamic redox conditions. Immobilizing mechanisms have mainly been attributed to the increase in pH, carbonates and phosphates content, and therefore, sorption/stabilization of metals (Shaheen et al., 2015; Shaheen and Rinklebe, 2015). Firstly, the higher pH in CSþSBFL compared to CS induces element immobilization because it favors precipitation of Cr, Cu, Ni, Pb, and Zn, decreases its solubility and promotes sorption and precipitation of these elements (Hooda, 2010; McBride, 1994). The higher pH in CSþSBFL compared to CS might have enhanced the hydrolysis of metals or even precipitation of metals as hydroxides (Sparks, 2003). Secondly, CSþSBFL have received substantial input of carbonates (82.5%; Table 1) via SBFL; in consequence precipitation and sorption of element increase (Shaheen et al., 2015; Shaheen and Rinklebe, 2015). Thirdly, the high immobilization rate of the metals by SBFL especially Pb (61.1%) in CSþSBFL as compared to CS could be explained by its high concentrations of phosphates (Sims et al., 2010). Reducing the mobilization of Pb in (Pb)-contaminated soils via phosphate amendments to sequester the Pb as pyromorphite [Pb5(PO4)3X, where X ¼ Cl, OH, or F] has been extensively studied (Bolan et al., 2014; Du et al., 2014; Hettiarachchi et al., 2001; Ryan et al., 2001). Selective sequential extraction procedures have determined speciation of Pb in phosphate-amended
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
6
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
Fig. 3. Relationships between EH in the soil suspension vs. concentrations of dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in CS and in CSþSBFL (n ¼ 21).
soils and reported that a substantial portion of the soil-Pb was transformed to pyromorphite [Pb5(PO4)3X, where X ¼ Cl, OH, or F] in phosphate-amended soils as evident by an increase of Pb
concentration in the residual fraction relative to a control (Cao et al., 2004; Scheckel et al., 2005). Thus, those results suggested that SBFL amendment could significantly reduce the mobilization
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
7
Fig. 4. Relationships between pH in the soil suspension vs. concentrations of dissolved Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn in CS and in CSþSBFL (n ¼ 21).
and increase the geochemical stability of Pb in a contaminated floodplain soil. Our results demonstrate that mobilization of Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn was lower under low EH and neutral/ weakly acidic conditions at the binging of the experiment than under high oxic and acidic conditions at the end of the experiment
in CS and in CSþSBFL. However, the mean concentrations of these elements (except for Mo and Mn) were higher in CS than in CSþSBFL because the pH values were relatively lower in CS than in CSþSBFL at the end of the experiment, which indicate that the pH is a crucial factor to control the mobilization of the elements in our soil.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060
8
S.M. Shaheen, J. Rinklebe / Journal of Environmental Management xxx (2016) 1e8
4. Conclusion Our results conclude that under prevailing acid conditions the systematic increase of EH along with reverse decrease of pH favors the mobilization of the studied elements in both systems, CS and CSþ SBFL. The application of SBFL to the floodplain soil might lead to a decreased release of Cu, Cr, Pb, and Fe under changing redox conditions in highly dynamic floodplain ecosystems. Thus, SBFL is able to decrease mobilization of Cu, Cr, Pb, and Fe in comparison to non-treated CS and might be used as an effective immobilizing agent for these elements even under dynamic redox conditions. The SBFL is an effective immobilizing agent for Cd, Co, Mn, Mo, Ni, and Zn under oxic acidic conditions; however, SBFL mobilized these elements under reducing neutral conditions. This might be worth proving under field conditions with view to an adequate remediation option aiming to minimize the potential risk to humans and environment. For a better understanding of mobilization processes of metals, similar studies should be conducted with a variety of wetland soils around the world. In future, it will be challenging to determine different metal species in the dissolved and colloidal fraction as well as in soil-sediments of the amended floodplain soil under dynamic redox conditions which is important for an appropriate risk assessment. Acknowledgments We thank the German Academic Exchange Foundation (Deutscher Akademischer Austauschdienst, DAAD) (GERSS Fellowship; Code number A1291166 and WAP program; Code number A/14/05113); the Egyptian Science and Technology Development Fund (STDF-STF; Project ID: 5333), and the German Alexander von Humboldt Foundation (Ref 3.4 e EGY e 1185373 e GF-E) for financial support of the postdoctoral scholarships of Prof. Shaheen at the University of Wuppertal, Germany. The authors thank Dr. T. Frohne, Mr. F. Beckers, Mrs. M. Ehlert, Mrs. J. Mihajlovic, and Mr. C. Vandenhirtz (University of Wuppertal, Germany) for technical assistance. Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.jenvman.2016.07.060. References Akiyoshi, S., Hisashi, S., 2004. Adsorption characteristics of molybdenum on various soils and incorporation into soil organic matter. Jap. J. Soil Sci. Pl. Nutr. 75, 179e184. Akunwa, N.K., Muhammad, M.N., Akunna, J.C., 2014. Treatment of metalcontaminated wastewater: a comparison of low-cost biosorbents. J. Environ. Manag. 146, 517e523. Antoniadis, V., Shaheen, S.M., Boersch, J., Frohne, T., Du Laing, G., Rinklebe, J., 2016. Bioavailability and risk assessment of potentially toxic elements in garden edible vegetables and soils around a highly contaminated former mining area in Germany. J. Environ. Manag. http://dx.doi.org/10.1016/j.jenvman.2016.04.036. BBodSchV, 1999. Bundes-Bodenschutz- und Altlastenverordnung (BBodSchV) vom 12. Juli 1999. Bundesgesetzblatt I 1999, 1554. Federal Soil Protection and Contaminated Sites Ordinance dated 12 July 1999. Bolan, N., Kunhikrishnan, A., Thangarajan, R., Kumpiene, J., Park, J., Makino, T., Kirkham, M.B., Scheckel, K., 2014. Remediation of heavy metal(loid)s contaminated soils - to mobilize or to immobilize? (Review). J. Hazard. Mater. 266, 141e166. Cao, X.D., Ma, L.Q., Rhue, D.R., Appel, C.S., 2004. Mechanisms of lead, copper and zinc retention by phosphate rock. Environ. Pollut. 131, 435e444.
DIN EN 15933, 2012. Schlamm, behandelter Bioabfall und Boden e Bestimmung des pH-Werts. In: Deutsches Institut für Normung. Du, Y.-J., Wei, M.L., Reddy, K.R., Jin, F., Wu, H.-L., Liu, Z.-B., 2014. New phosphatebased binder for stabilization of soils contaminated with heavy metals: leaching, strength and microstructure characterization. J. Environ. Manag. 146, 179e188. Dutton, J., Huijbregts, T., 2006. Root quality and processing. In: Draycott, A.P. (Ed.), Sugar Beet. Blackwell Publishing LTD, Oxford. UK, pp. 409e442. Evans, L.J., Barabash, S.J., 2010. Molybdenum and vanadium. In: Hooda, P.S. (Ed.), Trace Elements in Soils. John Wiley & Sons Ltd, United Kingdom, pp. 347e381. Frohne, T., Rinklebe, J., Diaz-Bone, R.A., Du Laing, G., 2011. Controlled variation of redox conditions in a floodplain soil: impact on metal mobilization and biomethylation of arsenic and antimony. Geoderma 160, 414e424. Hettiarachchi, G.M., Pierzynski, G.M., Ransom, M.D., 2001. In situ stabilization of soil lead using phosphorus. J. Environ. Qual. 30, 1214e1221. Hooda, P.S., 2010. Trace Elements in Soils, first ed. John Wiley & Sons Ltd, PO19 8SQ, United Kingdom. IUSS-FAO, 2014. World Reference Base for Soil Resources. FAO, Rome. Kabata-Pendias, A., 2011. Trace Elements in Soils and Plants. CRC Press, Boca Raton. McBride, M.B., 1994. Environmental Chemistry of Soils. Oxford Univ. Press, New York. Ok, Y.S., Lim, J.E., Moon, D.H., 2011. Stabilization of Pb and Cd contaminated soils and soil quality improvements using waste oyster shells. Environ. Geochem. Health 33, 83e91. € ter, F., Rennert, T., 2016b. Exploiting biogeoRinklebe, J., Shaheen, S.M., Schro chemical and spectroscopic techniques to assess the geochemical distribution and release dynamics of chromium and lead in a contaminated floodplain soil. Chemosphere 150, 390e397. Rinklebe, J., Shaheen, S.M., Yu, K., 2016a. Release of As, Ba, Cd, Cu, Pb, and Sr under pre-definite redox conditions in different rice paddy soils originating from the U.S.A. and Asia. Geoderma 270, 21e32. Ryan, J.A., Zhang, P.C., Hesterberg, D., Chou, J., Sayers, D.E., 2001. Formation of chloropyromorphite in a lead-contaminated soil amended with hydroxyapatite. Environ. Sci. Technol. 35, 3798e3803. Scheckel, K.G., Ryan, J.A., Allen, D., Lescano, N.V., 2005. Determining speciation of Pb in phosphate-amended soils: method limitations. Sci. Total Environ. 350, 261e272. Shaheen, S.M., Frohne, T., White, J., DeLaune, R., Rinklebe, J., 2016b. Redox-induced mobilization of copper, selenium, and zinc in deltaic soils originating from Mississippi (U.S.A.) and Nile (Egypt) River Deltas: a better understanding of biogeochemical processes for safe environmental management. J. Environ. Manag. http://dx.doi.org/10.1016/j.jenvman.2016.05.032. Shaheen, S.M., Rinklebe, J., Frohne, T., White, J., DeLaune, R., 2016a. Redox effects on release kinetics of arsenic, cadmium, cobalt, and vanadium in Wax Lake Deltaic soils. Chemosphere 150, 740e748. Shaheen, S.M., Eissa, F., Ghanem, K.M., Gamal El-Din, H., Al-Anany, F., 2013. Heavy metals removal from aqueous solutions and wastewaters by using various byproducts. J. Environ. Manag. 128, 514e521. Shaheen, S.M., Rinklebe, J., 2015. Impact of emerging and low cost alternative amendments on the (im)mobilization and phytoavailability of Cd and Pb in a contaminated floodplain soil. Ecol. Eng. 74, 319e326. Shaheen, S.M., Rinklebe, J., Rupp, H., Meissner, R., 2014. Temporal dynamics of pore water concentrations of Cd, Co, Cu, Ni, and Zn and their controlling factors in a contaminated floodplain soil assessed by undisturbed groundwater lysimeters. Environ. Pollut. 191, 223e231. Shaheen, S.M., Rinklebe, J., Selim, H.M., 2015. Impact of various amendments on the bioavailability and immobilization of Ni and Zn in a contaminated floodplain soil. Int. J. Environ. Sci. Technol. 12, 2765e2776. Sims, A.L., Windels, C.E., Bradley, C.A., 2010. Content and potential availability of selected nutrients in field applied sugar beet factory lime. Commun. Soil Sci. Plan. 41, 438e453. Soares, M.A.R., Quina, M.J., Quinta-Ferreira, R.M., 2015. Immobilisation of lead and zinc in contaminated soil using compost derived from industrial eggshell. J. Environ. Manag. 164, 137e145. Sparks, D.L., 2003. Environmental Soil Chemistry, second ed. Academic Press, New York, NY, USA. Takeno, N., 2005. National Institute of Advanced Industrial Science and Technology (Atlas of Eh-pH diagrams. Geological Survey of Japan Open File Report. Takeno, Naoto). U.S. Environmental Protection Agency, 2007. Microwave Assisted Acid Digestion of Sediments, Sludges, Soils, and Oils, vol. 3051A. Yu, K.W., Bohme, F., Rinklebe, J., Neue, H.U., DeLaune, R.D., 2007. Major biogeochemical processes in soils e a microcosm incubation from reducing to oxidizing conditions. Soil Sci. Soc. Am. J. 71, 1406e1417. Yu, K.W., Rinklebe, J., 2011. Advancement in soil microcosm apparatus for biogeochemical research. Ecol. Eng. 37, 2071e2075.
Please cite this article in press as: Shaheen, S.M., Rinklebe, J., Sugar beet factory lime affects the mobilization of Cd, Co, Cr, Cu, Mo, Ni, Pb, and Zn under dynamic redox conditions in a contaminated floodplain soil, Journal of Environmental Management (2016), http://dx.doi.org/10.1016/ j.jenvman.2016.07.060