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1.
Trace elements in pedosequences II. Two Pararendzina-Pseudogley-sequences on loess Total amounts and fractions of Cu, Zn, Pb, Cd, Co and Ni extractable in boiling oxalate (replacing dithionite for analytical reasons), oxalate at room temperature and EDTA were determined in two hydro-pedosequences on loess ranging between Pararendzina-Braunerde-Parabraunerde-Pseudogley. The pedogenic influence on the depth functions of these trace elements was much weaker in the loess soils than in those on slates of part I of this study. With a few exceptions external additions seem to be masked by soil cultivation. Clay movement (Alfisols) produced maxima of Fe and Cu in the Bt horizon. Carbonates of the parent loess contain trace elements which are released into the soil during solum formation. As long as they exist in carbonates they are hardly extractable with oxalate but with EDTA. In contrast, after pedogenic decomposition of the carbonates in the B horizon their trace elements are now oxalate but no longer EDTA extractable. In the A horizon, where organic matter is involved the trace elements are again EDTA extractable. As in the soils from slate (part I) Cd behaves more similarly to Pb than to Zn. The total element balance indicates a slight gain of Pb and loss of Zn whereas the total amount of the other elements was essentially unchanged. Generally, the more mobile fractions increased during soil formation. 相似文献
2.
Xiaofang Guo Guixiang Zhang Zebin Wei Liping Zhang Qiusheng He Qitang Wu Tianwei Qian 《Journal of Soils and Sediments》2018,18(3):835-844
Purpose
Soil washing with chelators is a viable treatment alternative for remediating multi-contaminated soils. The aim of this study was to investigate the removal efficiencies of Cd, Zn, Pb, and Cu in alkaline and acid multi-metal-contaminated soils by washing with the mixed chelators (MC).Materials and methods
The batch experiments were carried out to evaluate the removal efficiencies of heavy metals in contaminated soils by the MC with different molar ratios of EDTA, GLDA, and citric acid, and evaluated the washing factors, including contact time, pH, MC concentration, and single and multiple washings at the same MC dose, on the removal efficiencies.Results and discussion
Results showed that the removal efficiencies for Cd, Zn, Pb, and Cu by the MC (the molar ratio of EDTA, GLDA, and citric acid was 1:1:3) were as much as those of the only EDTA washing from both soil at the same application dose of total chelators; moreover, the application dose of EDTA decreased by 80%. For the alkaline-contaminated soil, the removal efficiencies of Cd, Zn, Pb, and Cu decreased with the increasing of the solution pH, which was opposite to acid-contaminated soil. This was attributed to that the metal-ligand complex could be obviously re-adsorbed on the soil surface sites, particularly in low pH values. The removal efficiencies of Cd, Zn, Pb, and Cu depended on MC concentration. A higher MC concentration led to a more effective removal of Cd, Zn, Pb, and Cu in alkaline-contaminated soil; however, their changes were slightly increased in acid-contaminated soil. At the same dose of MC, single washing with higher MC concentration might be favorable to remove heavy metals, moreover, with much less wastewater generation.Conclusions
The MC (the molar ratio of EDTA, GLDA, and citric acid was 1:1:3) may be a useful, environmentally friendly, and cost-effective chelators to remediate heavily multi-metal-contaminated soil.3.
重金属高污染农田土壤EDTA淋洗条件初探 总被引：7，自引：1，他引：6
通过室内振荡淋洗试验研究了乙二胺四乙酸二钠(EDTA)浓度、淋洗时间、液固比、淋洗次数对甘肃省白银市某高污染农田土壤中重金属去除效果的影响,并测定了EDTA淋洗前后土壤中重金属形态的变化。结果表明：淋洗剂浓度和液固比越高、淋洗时间越长、淋洗次数越多,对重金属的去除效果越好。在EDTA浓度为5 mmol/L、液固比为2.5、连续振荡淋洗3次、每次1 h时,对土壤中Cd、Cu、Pb、Zn 4种重金属的总去除率分别为 55.2%、21.9%、19.3% 和20.9%,其中Cd 淋洗效率最高。EDTA对土壤中交换态、碳酸盐结合态和铁锰氧化物结合态重金属的去除效果明显,但不能有效去除有机及硫化物态和残余态土壤重金属。 相似文献
4.
化学萃取修复尾渣土壤的金属形态变化特征 总被引：4，自引：0，他引：4
LIU Yun-Guo WANG Xian-Hai ZENG Guang-Ming LI Xin ZHOU Chun-Hu FAN Ting LI Yong-Li YUAN Xin-Zhong 《土壤圈》2006,16(3):312-318
The efficiency of EDTA, HNO3 and CaCl2 as extractants to remove Pb, Zn and Cu from tailing soils without varying soil pH was investigated with distributions of Pb, Zn and Cu being determined before and after extraction using the sequential extraction procedure of the optimized European Community Bureau of Reference （BCR）. Results indicated that EDTA and HNO3 were both effective extracting agents.The extractability of extractants for Pb and Zn was in the order EDTA 〉 HNO3 〉 CaCl2, while for Cu it was HNO3 〉 EDTA 〉 CaCl2. After EDTA extraction, the proportion of Pb, Zn and Cu in the four fractions varied greatly, which was related to the strong extraction and complexation ability. Before and after extraction with HNO3 and CaCl2, the percentages of Pb, Zn and Cu in the reducible, oxidizable and residual fractions changed little compared to the acid-extractable fraction. The lability of metal in the soil and the kinds of extractants were the factors controlling the effects of metal extraction. 相似文献
5.
Behaviour of heavy metals in soils. 1. Heavy metal mobility 158 soil samples with widely varying composition were analysed for their total, EDTA, DTPA and CaCl2 extractable contents of Cd, Zn, Mn, Cu and Pb. By means of single and multiple regressions the relations between the different heavy metal fractions and the pH, organic carbon and clay content were considered. The correlations between the total, EDTA and DTPA extractable contents are very close, whereas the CaCl2 extractable contents are not or only weakly correlated with these fractions. According to these statistical results the former fractions are considered to be the total quantity (total content) and the reactive quantity (EDTA and DTPA extractable contents) of the heavy metals, whereas the CaCl2 extractable fraction represents the mobile fraction of the heavy metals in soils. The multiple regressions show that the mobile content of heavy metals is closely correlated with each of the quantity fractions and with soil pH. In the same way the proportion of the mobile fraction (in %) of the total, EDTA and DTPA extractable heavy metal content of the soil samples is closely related to the soil pH. Hereby the proportion of the mobile content of the various elements increases in the pH range 6,5 - 3 below element-specific threshold pH values (in brackets) in the order Cd (6,5) > Mn (5,7) > Zn (5,3) > Cu (4,5) > Pb (3,5). In the pH range 6,5 - 7,5 mainly Cu and to a lesser degree also Pb show an increasing mobility due to the influence of soluble organic substances. 相似文献
6.
《Communications in Soil Science and Plant Analysis》2012,43(21):2789-2800
Maintaining the quality of groundwater is a major consideration when developing management practices to effectively use cow dung manure (CDM) as a nutrient source and soil conditioner in agricultural production systems. This study examines the effect of CDM on the solubility of copper (Cu), lead (Pb), and zinc (Zn) in urban garden fields from Kaduna under long-term vegetable production. Soil samples were collected from Kakau, Kakuri, Trikaniya, and Romi in Kaduna metropolis in northern Nigeria. Soil–manure mixtures at the rate of 100 g CDM kg?1 soil were incubated for 2 weeks and analyzed for exchangeable [0.1 M calcium chloride (CaCl2)–extractable], mobile [1 M ammonium nitrate (NH4NO3)–extractable], and potentially labile [0.05 M ethylenediaminetetraacetic acid (EDTA)–extractable] copper (Cu), lead (Pb), and zinc (Zn). Addition of CDM increased exchangeable Cu in Kakuri and Romi and exchangeable Pb in Kakau and Kakuri, but decreased exchangeable Zn across the sites. The addition of CDM increased mobile Cu and Pb in all the sites. Although there was a decrease in mobile Zn in Kakau and Romi after the soil–manure incubation period, mobile Zn increased in Trikaniya and Kakuri. Furthermore, CDM decreased potentially labile Cu, Pb, and Zn in all the sites except for Romi, which increased labile Cu. To sustain the quality of soil and minimize groundwater pollution and food chain contamination, use of CDM in urban garden soils polluted with Cu, Pb, and Zn should be regulated or discouraged entirely to reduce the mobility of these metals. 相似文献
7.
《European Journal of Soil Biology》2006,42(2):89-98
Heavy metals such as arsenic (As), lead (Pb), copper (Cu) and zinc (Zn) can be found in large concentrations in mine spills in Mexico. Interest in contamination by these heavy metals has increased recently as they can change the functioning of soil ecosystems qualitatively and quantitatively. They disturb the activities of soil fauna and contaminate drinking water in large parts of the world, which severely affects human health. Little, however, is known how heavy metals might affect the biological functioning of a soil. Soil was sampled from eight locations along a gradient of heavy-metal contamination with distance from a mine in San Luis Potosí (Mexico) active since about 1800 AD. Microbial biomass was determined with the original chloroform fumigation incubation (CFI) as well as extraction (CFE) techniques and the substrate induced respiration (SIR) technique while C and N mineralization were measured. Total concentrations of As in the top 0–10 cm soil layer ranged from 8 to 22992 mg kg–1, from 31 to 1845 mg kg–1 for Pb, from 27 to 1620 mg kg–1 for Cu and from 81 to 4218 mg kg–1 for Zn. There was a significant negative correlation (P < 0.0001) between microbial biomass, soil organic carbon, total N and C mineralization and the heavy metal content of the soil. The microbial biomass C to organic C ratio, which varied from 0.4 to 1.9%, specific respiratory activity (qCO2), and oxidation of NO2– were not affected by heavy metals. It was found that long-term contamination of soil with heavy metals had an adverse effect on the amount of soil microorganisms as evidenced by a marked decrease in microbial biomass C, but not some of their characteristics. According to principal components analysis (PCA), the correlation matrix showed three distinct factors explaining 71% of the variance. A first factor including heavy metals (As, Pb, Cu and Zn) with a negative loading and total N, organic C, soil microbial biomass with a positive loading characterized the soil organic matter and contamination status. Loam and sand combined for the second factor characterizing the textural classification while the third factor was loaded by CEC and clay content. 相似文献
8.
Total Zn in alluvial and calcareous soils (average 138 and 70 ppm respectively) was significantly related to their contents of CaCO3 (negatively), O.M. and clay (positively). Extracting Zn by Na2EDTA gave the highest values for both soil types. Total Cu contents varied widely from 26 to 111 ppm in alluvial and from 15 to 30 ppm in calcareous soils. They were negatively correlated with the CaCO3 contents. The pot experiments showed that EDTA(NH4)2CO3, Na2EDTA and DTPA are reasonable extractants for available Zn from both soil types. DTPA was efficient for all soils investigated, while Na2 EDTA and EDTA-citrate were specific for extracting Cu from calcareous soils. 相似文献
9.
不同pH值混合螯合剂对土壤重金属淋洗及植物提取的影响 总被引：6，自引：1，他引：5
为了得出混合螯合剂（MC）淋洗去除重金属的最佳pH值以及对后续植物提取重金属的影响,用Ca(OH)2将pH值为2.75的MC提高至pH值5、7和9,对重金属污染土壤进行了盆栽淋洗试验,而后种植东南景天（Sedum Alfredii）,测定淋出液及植物重金属含量。另外,通过浸提试验研究了含有不同阳离子的MC对重金属淋洗效果的影响。结果表明,pH值为5和7的MC显著提高了Cd、Pb和Cu的淋出率。与Na+、K+离子相比,Ca2+的存在能够提高MC对重金属的淋洗去除。pH值7和9的MC淋洗土壤后提高了东南景天的生物量,但是降低东南景天中Cd和Zn的浓度,导致其植物提取率低于无淋洗剂对照。在化学淋洗+植物提取联合技术中,Cd和Zn主要靠植物提取去除,植物提取率分别可达土壤Cd的30%～40%和土壤Zn的6.5%～6.9%;而Pb和Cu主要靠混合螯合剂淋洗去除,去除率分别为2.3%～2.6%和1.6%～2.0%。综合来说,如果需要同时去除Cd、Zn、Pb和Cu,降低土壤重金属有效态含量,用pH值9的MC淋洗土壤联合植物提取较为合适。 相似文献
10.
11.
《Communications in Soil Science and Plant Analysis》2012,43(5-6):697-716
Abstract The effect of sewage sludge applications on extractability and uptake by chard and lettuce of soil cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), leaf (Pb), and zinc (Zn) was investigated. Ten different treatments (0, 150, 300, and 500 kg N ha‐1) as mineral fertilizer, and 400, 800, and 1,200 kg N ha‐1 of aerobically and anaerobically‐digested sewage sludges were applied annually to a sandy‐loam soil since 1984. Seven years after the start of the treatments, higher levels of heavy metals were detected in the soil, depending on the type of metal, depth of sampling, type of sludge used, and, especially, rate of application. Following a sequential extraction procedure incorporating 0.1M CaCl2, 0.5M NaOH, and 0.05M Na2EDTA, most of the heavy metals in soil were detected in the Na2EDTA solution and the residual fractions. Large amounts of Cd appeared to be extracted by CaCl2, whereas substantial amounts of Cu and Ni were isolated by NaOH. The effect of treatments on the percentages of the metals found in each fraction depended on the type of metal, sampling depth, sludge used, and application rate. No significant increases were found in the heavy metal contents of chard and lettuce leaves, but some of the treatments resulted in a significant decrease of Cd and Cr levels in lettuce leaves. 相似文献
12.
Xinyu Mao Fengxiang X. Han Xiaohou Shao Zikri Arslan Jacqueline McComb Tingting Chang Kai Guo Ahmet Celik 《Journal of Soils and Sediments》2016,16(10):2344-2353
Purpose
Extensive deposition of Pb, As, and Cs in soils may damage ecosystems and human’s health. Soil washing is the most conventional remediation method, and its efficiency depends on metal solubility in soil. This study aims to optimize operating variables of electro-kinetic field (EKF)-enhanced soil washing procedures.Materials and methods
Soil samples from a Mississippi River Delta rice field were homogeneously spiked with Pb, As, and Cs, and contaminated soil was aged for 3 months. The remediation involved a first stage electro-kinetic process, followed by a soil washing procedure. Soil pH changes under EKF were studied. Effects of citric acid and reversed EKF were investigated for alleviating possible alkaline precipitation. In the washing procedure, soil washing time and cycles with different extractants were examined. The overall EKF-enhanced soil washing efficiencies were discussed as well.Results and discussion
The implement of EKF offered an acidic soil environment around the anode areas for solubilizing metal(loid)s. Combined with EKF, citric acid was more conductive to desorb metal(loid)s. In addition, the reversed EKF effectively alleviated metal(loid) precipitation caused by alkalization in the first stage cathode areas. The EKF significantly enhanced metal(loid) extractions in the anode area of soils using Na2EDTA, CaCl2, and citric acid at pH of 2. The most preferable removal of Pb (80–98 %), As (48–63 %), and Cs (10–13 %) was achieved with three extractants. CaCl2 and citric acid were proved to be suitable alternatives to Na2EDTA for Pb extraction. A washing process of 2 h extraction with double washing cycles was optimized.Conclusions
Soil washing time and cycles were major factors governing the metal(loid) removal from soil. Washing process of 2 h extraction with double cycles was optimized for further extraction based on higher washing efficiency. The EKF effectively improved washing efficiency while some electrical parameters need further studies for cost performance consideration.13.
Background Regional soil environmental quality is a hotspot and difficulty in the environmental sciences for the spatial variability
of pollutants and the relationship between them. Beijing, the capital of China, has been undergoing a rapid economical development
during the past three decades, and thus might encounter the same issues as the developed countries. However, there is little
information about the soil environmental quality of Beijing, especially at the regional scale. The real soil environmental
situation of heavy metals remains unknown, even less the sources of possible pollutants.
Objectives The main objectives were to identify the spatial variability and main sources of heavy metals in Beijing soils by conducting
multivariate statistical analyses, including geostatistical analysis assisted with GIS tools. These results will contribute
to the establishment of the soil quality baseline and the management of regional environment.
Materials and Methods Seven hundred and seventy-three samples of topsoils (0–20 cm) were collected from all over Beijing, China. The samples were
digested with HNO3 and H2O2. The concentrations of Cr, Cu, Ni, Pb and Zn were analyzed with a FL-AAS and those of Cd with a GF-AAS. The concentrations
of As were determined with AFS-2202. Principal component analysis (PCA) and partial correlation analysis (CA) were used and
geostatistics was conducted for the data processing.
Results Concentrations of topsoil As, Cd, Cr, Cu, Ni, Pb and Zn in the Beijing area were measured and contour maps were constructed
to describe the metals’ spatial distribution. Except for the background effect of the soils, anthropogenic factors made the
soil heavy metal concentrations increase, especially in the center of the city. Combined with the PCA results, it was found
that vehicle exhaust and smelters were the main sources of soil heavy metals. Pedogenic factors were also controlling the
spatial features of metals.
Discussion Combined with the results of PCA, 7 heavy metals could be divided into 4 factors. F1 was the metals, i.e., Cu, Pb, Zn, mainly
controlled by the human activities. Cr and Ni was in F2, Cd in F3 and As in F4. These 3 factors might be controlled by the
soil parent materials. Concentrations of 7 heavy metals were comparable with the first level of environmental quality standard
for soils of China and much lower than the second level of national standard for soils.
Conclusion The heavy metal concentrations in the topsoil of Beijing are mostly comparable with the background values, especially for
As, Cr and Ni. In the city center of Beijing, Cu, Pb and Zn had a high concentration of distribution. The spatial features
of As, Cr and Ni are mainly controlled by pedogenic factors, whereas Cd, Cu, Pb and Zn are controlled by anthropogenic and
parent factors. Traffic and smelting contribute greatly to the increase of Pb, Zn and Cu in the soil, especially in the center
of the city. Landfill may have also affected the soil quality around it.
Recommendation Different factors were controlled by parent materials, which might be related to the different soil minerals. Further research
should be conducted in Beijing to elucidate the relationship between heavy metals and soil minerals.
ESS-Submission Editor: Chengron Chen, PhD (c.chen@griffith.edu.au) 相似文献
14.
The performance of EDTA for the treatment of calcareous soils contaminated with heavy metals from mining and smelting activities was evaluated in this study. Soil samples containing variable levels of contamination, from 500 to 35 000 mg kg-1 Pb and 700 to 20 000 mg kg-1 Zn, were subjected to EDTA treatment and the extraction of heavy metals was found to vary, ranging between 50 and 98% for Pb and 50 to 100% for Zn. Total residual concentrations were above the limits set by regulatory authorities; leachable metals, however, were efficiently removed and treated soils were all acceptable in terms of toxicity. The effect of EDTA concentration and pulp density was studied on a soil sample containing 12 000 mg kg-1 Pb and 10 000 mg kg-1 Zn. Heavy metals removal was improved at low pulp densities and when EDTA concentration was increased from 0.025 to 0.25 M. The tetrasodium salt Na4-EDTA was found to be less effective for metals removal compared to the disodium salt Na2-EDTA, though applied at higher concentrations. This experimental work has also demonstrated the great importance of soil matrix for the overall evaluation of the EDTA leaching as a cost effective remedial option. The simultaneous dissolution of calcite was found to consume approximately 90% of the available EDTA. It was thus concluded that for the treatment of calcareous soils the design criteria and cost estimations should be based on the calcite content of the soil. 相似文献
15.
The association of Al, Mn, Fe, Ba, Zn, Cr, Ni, Co and Pb withsoil organic matter (SOM) was investigated in three Japanesesoils. Organically bound metals were assayed by elementalanalysis of a fraction extracted with acidified hydrogenperoxide (H2O2) and the humic acid extracted withalkaline reagent, from soil sampled at various depths of solums.A Dystric Cambisol showed higher extractability with acidifiedH2O2 for most of the metals than a Humic Andosol and an Orthic Acrisol. A Humic Andosol had more metals associated with humicacid than the other two soils.Cu showed high extractability with acidified H2O2 andalso significant association with humic acid, while Pb showedhigh extractability with acidified H2O2 but itsassociation with humic acid was relatively low among the metalsinvestigated. As humic acid is highly resistant to weathering,retention of Cu with SOM may last longer than that of Pb.The binding of metals with SOM probably has contributed to theaccumulation of some metals in organic-rich shallow horizons of soil. Such metals were Zn, Cu, Ni and Pb in a Dystric Cambisol,Cu in a Humic Andosol, and Pb and Cu in an Orthic Arisol. 相似文献
16.
工业废弃地多金属污染土壤组合淋洗修复技术研究 总被引：12，自引：0，他引：12
采用批量淋洗实验方法,对比了采用人工螯合剂乙二胺四乙酸二钠盐(EDTA-Na2)和天然有机酸草酸(oxalic acid,OX)对工业废弃地污染土壤中重金属的去除效果,并采用不同浓度草酸和EDTA组合的两步淋洗法研究多金属污染土壤的最佳淋洗方式。结果表明,EDTA淋洗剂对土壤中Zn、Pb、Cu、Ni去除效果较好,而对Cr去除效果较差,实验条件下,EDTA对金属的去除率并未随着浓度增加而增加;相反,草酸对Cr去除效果较好,且去除率随着淋洗剂浓度的增加而增加,而对Zn、Cu、Ni的去除效果随着淋洗剂浓度增加而降低,对Pb的去除率非常低;采用先以0.20 mol L-1草酸提取2 h,再以0.01 mol L-1EDTA提取2 h的两步淋洗法可以达到对多金属同时去除,且对Zn、Cu、Cr、Ni的去除率明显高于单用草酸和EDTA,总去除率分别为Zn 75.21%、Pb 21.30%、Cu 59.81%、Cr 60.72%和Ni 62.10%,更为有意义的是两步淋洗法对非残渣态金属去除效果分别高达Zn 91.93%、Pb 57.75%、Cu 75.33%、Cr 73.94%、Ni 77.99%。利用不同化学淋洗剂对金属去除能力的差异进行组合的多步淋洗法是一种较为高效的去除工业废弃地污染土壤中重金属的化学淋洗修复方法。 相似文献
17.
Trace elements in pedosequences I. Two Braunerde-Podsol-sequences on slate Total amounts and fractions of Fe, Cu, Zn, Pb, Cd, Co and Ni extractable in boiling oxalate (replacing dithionite for analytical reasons), oxalate at room temperature and EDTA were determined in two pedosequences on slates ranging between Braunerde (Ochrept) and Podsol (Spodosol). The total amounts lay within the normal range of these elements in slates except a few samples much higher in Zn and Cd due to sulphides in the rock. In surface soil horizons rich in organic carbon the trace elements are accumulated in the order Cu < Zn < Cd < Pb. This accumulation increased with increasing degree of podsolization but is also partly due to atmospheric input. The relative accumulation of the various fractions in the surface soil increased in the order: boiling oxalate < room temperature oxalate < EDTA. Along the same order the depth function is determined to increasing extent by pedogenic processes rather than by lithogenic differences. In contrast to Fe, no minima in the podsol A2 nor definite maxima in the B were noticed for Cu, Zn, Pb and Cd. With regard to the affinity towards organic matter Cd appears to behave more similarly to Pb than to Zn. Co and, even more so, Ni were lost during podsolization. The significance of the fractionation procedure which was very useful with Fe was not satisfying with the trace elements. Relationships between single element fractions and various soil components were generally poor except for that between the EDTA fraction and organic matter content. The total element balance is complicated by the heterogenity of the parent rock, but an increase in the mobile fractions in the solum during podsolization is generally indicated. There was a loss in the total amount of Fe, Cu, Zn, Co and Ni due to podsolization whereas a gain for Pb and Cd was noticed most probably through atmospheric intake. 相似文献
18.
Verónica González María Díez-Ortiz Mariano Simón Cornelis A. M. van Gestel 《Journal of Soils and Sediments》2011,11(7):1199-1208
Purpose
A contaminated soil was amended to reduce bioavailability of metals (As, Cd, Cu, Pb, and Zn) and to modify its potential environmental impacts. Reproduction toxicity tests using two different soil invertebrates, Enchytraeus crypticus and Folsomia candida, were used to evaluate efficiency of soil amendments to reduce metal availability. 相似文献19.
Organic Acids for the In Situ Remediation of Soils Polluted by Heavy Metals: Soil Flushing in Columns 总被引：3，自引：0，他引：3
To compare the soil remediation effectiveness of saltsof weak organic acids with strongchelating agents, three soils of different textures,all polluted by heavy metals, were washed in a column,at optimum pH, with salts of weak organic acids,namely, citrate, tartarate or oxalate + citrate orchelating agents (EDTA or DTPA). For the clay loam,Cr, Mn, Hg and Pb were removed by citrate andtartarate at levels of 43 to 45, 37 to 41, 91 to 92and 75%, respectively. EDTA and DTPA effectivelyleached only Pb after 20 pore volumes. For the loam,citrate leached 98 and 89% of Cd and Pb after 20 porevolumes, respectively, while tartarate leached out 91and 87% of Cd and Pb. EDTA and DTPA removed 93 to97% of these metals after 20 pore volumes. For thesandy clay loam, 84 to 91, 73 to 84, 56 to 70 and 72to 81% of Cd, Cu, Pb and Zn were removedrespectively, by citrate and tartarate. EDTA and DTPAremoved 93 to 97% of these metals after 20 porevolumes. An in situ soil remediation simulation wasalso tested using the sandy clay loam in a tub. After12 hr of retention, the citrate solution washed 81, 82,73 and 90%, of Cd, Cu, Pb and Zn, respectively, aftersix pore volumes. EDTA and DTPA effectively removedall heavy metals, except for Hg, but also extractedlarge quantities of soil nutrients and pollute thesoil by being adsorbed on the soil particles. Thesalts of citrate and tartarate effectively removed theheavy metals from the three polluted soils whileleaching little macro-nutrients and improving soilstructure. Each soil reached C and B levels ofsoil-clean-up criteria after 10 to 20 pore volumes andwithin 10 to 15 hr of flushing. 相似文献
20.
Characterization of soil heavy metal pools in paddy fields in Taiwan: chemical extraction and solid-solution partitioning 总被引：1，自引：1，他引：0
Paul F. Römkens Horng-Yuh Guo Chien-Liang Chu Tsang-Sen Liu Chih-Feng Chiang Gerwin F. Koopmans 《Journal of Soils and Sediments》2009,9(3):216-228
Background, aim, and scope Ongoing industrialization has resulted in an accumulation of metals like Cd, Cu, Cr, Ni, Zn, and Pb in paddy fields across
Southeast Asia. Risks of metals in soils depend on soil properties and the availability of metals in soil. At present, however,
limited information is available on how to measure or predict the directly available fraction of metals in paddy soils. Here,
the distribution of Cd, Cu, Cr, Ni, Zn, and Pb in 19 paddy fields among the total, reactive, and directly available pools
was measured using recently developed concepts for aerated soils. Solid-solution partitioning models have been derived to
predict the directly available metal pool. Such models are proven to be useful for risk assessment and to derive soil quality
standards for aerated soils.
Material and methods Soil samples (0–25 cm) were taken from 19 paddy fields from five different communities in Taiwan in 2005 and 2006. Each field
was subdivided into 60 to 108 plots resulting in a database of approximately 3,200 individual soil samples. Total (Aqua Regia
(AR)), reactive (0.43 M HNO3, 0.1 M HCl, and 0.05 M EDTA), and directly available metal pools (0.01 M CaCl2) were determined. Solid-solution partitioning models were derived by multiple linear regressions using an extended Freundlich
equation using the reactive metal pool, pH, and the cation exchange capacity (CEC). The influence of Zn on metal partitioning
and differences between both sampling events (May/November) were evaluated.
Results Total metals contents range from background levels to levels in excess of current soil quality standards for arable land.
Between 3% (Cr) and 30% (Cd) of all samples exceed present soil quality standards based on extraction with AR. Total metal
levels decreased with an increasing distance from the irrigation water inlet. The reactive metal pool relative to the total
metal content is increased in the order Cr << Ni = Zn < Pb < Cu < Cd and ranged from less than 10% for Cr to more than 70%
for Cd. Despite frequent redox cycles, Cd, Pb, and Cu appear to remain rather reactive. The methods to determine the reactive
metal pool in soils yield comparable results, although the 0.43 M HNO3 extraction is slightly stronger than HCl and EDTA. The close correlation between these methods suggests that they release
similar fractions from soils, probably those reversibly sorbed to soil organic matter (SOM) and clay. The average directly
available pool ranged from less than 1% for Cu, Pb, and Cr to 10% for Ni, Zn, and Cd when compared to the reactive metal pool.
For Cd, Ni, Zn, and to a lesser extent for Cu and Pb, solid-solution partitioning models were able to explain up to 93% (Cd)
of the observed variation in the directly available metal pool. CaCl2 extractable Zn increased the directly available pool for Ni, Cd, and Cu but not that of Pb and Cr. In the polluted soils,
the directly available pool was higher in November compared to that in May. Differences in temperature, rainfall, and changes
in soil properties such as pH are likely to contribute to the differences observed within the year. The solid-solution partitioning
model failed to explain the variation in the directly available Cr pool, probably because Cr is present in precipitates rather
than being adsorbed onto SOM and clay. Despite obvious differences in parent material, source of pollution, climate, and land
use, solid-solution partitioning of Cd in paddy fields studied here was similar to that in soils from Belgium and the Netherlands.
Discussion To assess risks of metals in soils, both analytical procedures as well as models are needed. The three methods tested here
to determine the reactive metal pool are highly correlated and either of these can be used. The directly available pool was
predicted most accurately by the 0.43 M HNO3 method. The similarity of metal partitioning in paddy soils compared to well-drained soils suggests that changing redox conditions
in paddy fields have a limited effect on the geochemical behavior of metals like Cd, Ni, and Zn. Small but significant differences
in the directly available metal pool during the year suggest that redox cycles as well as differences in rainfall and temperature
affect the size of the directly available metal pool. The large observed spatial heterogeneity of contaminant levels requires
ample attention in the setup of soil monitoring programs.
Conclusions The directly available pool (0.01 M CaCl2) of Cd, Zn, and Ni in paddy fields can be described well by an extended Freundlich model. For Cu and Pb, more information
on dissolved organic carbon is needed to obtain a more accurate estimate of the directly available pool.
Recommendations and perspectives Soil testing protocols and models used in risk assessment consider the availability of pollutants rather than the total metal
content. Results from extensive testing indicate that approaches developed for nontropical regions can be applied in paddy
fields as well for metals like Cd, Ni, and Zn. This study shows that the chemical behavior under drained conditions in paddy
fields is comparable to that observed in soils across the European Union, which allows regions with large scale soil pollution
including Taiwan to apply such concepts to derive meaningful experimental protocols and models to assess risks of metals in
soils. 相似文献