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1.
Removal of Heavy Metals from Soil Components and Soils by Natural Chelating Agents. Part II. Soil Extraction by Sugar Acids 总被引：1，自引：0，他引：1
Aqueous solutions of the natural chelatingagents D-gluconic acid and D-glucaric acid (D[+]-saccharic acid) were tested for their ability to remove heavy metals (Cd, Cr, Cu,Ni, Pb, Zn) from a soil polluted by long-term application of sewage sludge. Batch equilibrium experiments were performed undervariation of fundamental process parameters, i.e. pH value, sugaracid concentration, batch solution volume, solid:liquid ratioand number of treatment cycles.The extractability of heavy metals was low under near-neutral andslightly basic pH conditions. It increased drastically between pH12.0 and 13.0. Pb and Cu were preferentially extracted metals.Compared with the extraction efficiency of pH adequate puresodium hydroxide solutions, the sugar acids enhanced thesolubilisation of Pb and Cr especially. The metal depletion fromsoil was the highest when applying 20 or 50 g L-1 solutionsof the chelating agents. Under strongly basic conditions solid:liquid ratios of 1:10 or 1:20 were proofed to be advantageous.Except Ni, multi-step extraction improved the metal removalstrongly. This effect was the greatest for Cr extraction. Underoptimised conditions the following metal extraction degrees wereachieved with strongly alkaline D-gluconic acid solutions: Ni 43%%, Cr 60%%, Cd 63%%,Zn 70%%, Pb 80%%, and Cu 84%%. 相似文献
2.
Soil/solution partitioning of trace metals (TM: Cd, Co, Cr, Cu, Ni, Sb, Pb and Zn) has been investigated in six French forest sites that have been subjected to TM atmospheric inputs. Soil profiles have been sampled and analysed for major soil properties, and CaCl2‐extractable and total metal content. Metal concentrations (expressed on a molar basis) in soil (total), in CaCl2 extracts and soil solution collected monthly from fresh soil by centrifugation, were in the order: Cr > Zn > Ni > Cu > Pb > Co > Sb > Cd , Zn > Cu > Pb = Ni > Co > Cd > Cr and Zn > Ni > Cu > Pb > Co > Cr > Cd > Sb , respectively. Metal extractability and solubility were predicted by using soil properties. Soil pH was the most significant property in predicting metal partitioning, but TM behaviour differed between acid and non‐acid soils. TM extractability was predicted significantly by soil pH for pH < 6, and by soil pH and Fe content for all soil conditions. Total metal concentration in soil solution was predicted well by soil pH and organic carbon content for Cd, Co, Cr, Ni and Zn, by Fe content for Cu, Cr, Ni, Pb and Sb and total soil metal content for Cu, Cr, Ni, Pb and Sb, with a better prediction for acidic conditions (pH < 6). At more alkaline pH conditions, solute concentrations of Cu, Cr, Sb and Pb were larger than predicted by the pH relationship, as a consequence of association with Fe colloids and complexing with dissolved organic carbon. Metal speciation in soil solutions determined by WHAM‐VI indicated that free metal ion (FMI) concentration was significantly related to soil pH for all pH conditions. The FMI concentrations of Cu and Zn were well predicted by pH alone, Pb by pH and Fe content and Cd, Co and Ni by soil pH and organic carbon content. Differences between soluble total metal and FMI concentrations were particularly large for pH < 6. This should be taken into account for risk and critical load assessment in the case of terrestrial ecosystems. 相似文献
3.
The adsorption characteristics of heavy metals: cadmium(II), chromium(III), copper(II), nickel(II), lead(II), and zinc(II) ions by kaolin (kaolinite) and ballclay (illite) from Thailand were studied. This research was focussed on the pH, adsorption isotherms of single-metal solutions at 30–60 °C by batch experiments, and on ion selectivityin mixed and binary combination solutions. It was found that, except Ni, metal adsorption increased with increased pH of the solutions and their adsorption followed both Langmuir and Freundlich isotherms. Adsorption of metals in the mixture solutions by kaolin was: Cr > Zn > Cu ≈ Cd ≈ Ni > Pb, and for ballclay was: Cr > Zn > Cu > Cd ≈ Pb > Ni. The adsorption of metals was endothermic, with the exception of Cd, Pb and Zn for kaolin, Cu and Zn for ballclay. Kaolin and ballclay exhibited relatively hard Lewis base adsorption site. The presence of other metals may reduce or promote the adsorption of heavy metals. The presence of Cr3+ induced the greatest reduction of metal adsorptiononto kaolin, as did the presence of Cu2+ for ballclay. 相似文献
4.
Freshly deposited stream sediments from six urban centres of the Ganga Plain were collected and analysed for heavy metals to obtain a general scenery of sediment quality. The concentrations of heavy metals varied within a wide range for Cr (115–817), Mn (440–1 750), Fe (28 700–61 100), Co (11.7–29.0), Ni (35–538), Cu (33–1 204), Zn (90–1 974), Pb (14–856) and Cd (0.14–114.8) in mg kg-1. Metal enrichment factors for the stream sediments were <1.5 for Mn, Fe and Co; 1.5–4.1 for Cr, Ni, Cu, Zn and Pb; and 34 for Cd. The anthropogenic source in metals concentrations contributes to 59% Cr, 49% Cu, 52% Zn, 51% Pb and 77% Cd. High positive correlation between concentrations of Cr/Ni, Cr/Cu, Cr/Zn, Ni/Zn, Ni/Cu, Cu/Zn, Cu/Cd, Cu/Pb, Fe/Co, Mn/Co, Zn/Cd, Zn/Pb and Cd/Pb indicate either their common urban origin or their common sink in the stream sediments. The binding capacity of selected metals to sediment carbon and sulphur decreases in order of Zn > Cu > Cr > Ni and Cu > Zn > Cr > Ni, respectively. Stream sediments from Lucknow, Kanpur, Delhi and Agra urban centres have been classified by the proposed Sediment Pollution Index as highly polluted to dangerous sediments. Heavy metal analysis in the <20-μm-fraction of stream sediments appears to be an adequate method for the environmental assessment of urbanisation activities on alluvial rivers. The present study reveals that urban centres act as sources of Cr, Ni, Cu, Zn, Pb and Cd and cause metallic sediment pollution in rivers of the Ganga Plain. 相似文献
5.
长期污灌农田土壤重金属污染及潜在环境风险评价 总被引：1，自引：0，他引：1
以西安市某典型污灌区农田土壤为研究对象,分析长期污水灌溉对表层土壤重金属含量及富集状况的影响,采用内梅罗指数法和Hakanson潜在生态危害指数法对其污染现状及潜在环境风险进行评价。结果表明：长期污灌已导致农田土壤Cd、Cr、Cu、Hg、Ni、Pb和Zn7种重金属相对自然背景有不同程度累积,其富集比例依次为100%、82.69%、100%、100%、80.77%、98.08%和100%,仅有土壤As平均含量低于其背景水平;以国家土壤环境质量标准二级限量值作为污染评价阈值,其中Cd和Hg污染表现突出,按其污染指数平均值排序为Cd〉Hg〉Ni〉Cu〉Zn〉As〉Cr〉Pb;土壤重金属综合潜在环境风险为＂强＂等级,Hg、Cd的环境影响占据主导;随污灌年限增长,离灌渠越近,农田土壤重金属的污染水平和环境风险越高。鉴于该区土壤重金属已呈现较强生态危害性,应及时采取必要防治措施,调整土地利用结构,确保农田环境及农产品安全生产。 相似文献
6.
采集草海湿地周边主要农作物可食部分及对应根系的土壤样品,分析测试了重金属Cd,Cr,Hg,Pb,As和Zn的含量,对比研究了土壤和作物中重金属污染水平及对重金属的富集能力。结果表明:土壤重金属元素Zn,As,Cr平均含量未超过贵州省土壤元素背景值,其他3种重金属Pb,Cd,Hg平均值分别是背景值的1.24,1.44,7.5倍;与中国《食品中污染物限量》标准相比,除Hg平均含量超标外,蔬菜中As,Cr,Zn,Cd和Pb平均含量处在可接受范围内。6种重金属的单因子污染指数的高低依次是Hg > Pb > Cd > As > Cr > Zn,葱和萝卜处于安全水平,其余农作物处于警戒线;不同种类作物中重金属富集特征差异较大,菠菜对As,Cd,Hg,Pb的富集系数比其余作物高,萝卜叶对Cr和Zn的富集能力较强,重金属Cr富集系数最低的是玉米,Zn和Hg富集系数最低的是萝卜根,Cd和Pb富集系数最低为马铃薯,As富集能力最低的为白菜。 相似文献
7.
工业区周边农田重金属污染评价及来源分析 总被引：4，自引：0，他引：4
以新疆北疆某工业区周边农田土壤为研究对象,采集0~20 cm土壤样品254个,测定了Cr、Ni、Cu、Zn、As、Hg、Pb、Cd共8种重金属含量。运用相关性分析和主成分分析探讨工业区周边农田土壤重金属的来源,运用GS+进行数据拟合,选取最佳模型,再进行克里格插值分析重金属的空间分布格局。结果表明,Cr、Ni、Cu、Zn、As、Hg、Pb和Cd的含量分别为45.00、28.53、55.66、73.57、13.39、2.17、15.38和0.50 mg kg~(-1)。测量的金属除Cr之外均超过土壤的背景值,只有Hg处于中度污染,其余元素都处于非污染,而研究区综合潜在生态风险程度为严重型。重金属空间分布表明,Ni、Zn、As、Hg和Pb在东部和南部含量较高。来源分析表明,Hg来源受研究区内工业活动的影响;Cr、Ni、Zn和Cd主要来自于化肥、农药和地膜等农业活动和土壤母质的共同作用;As、Hg和Pb主要来源是受研究区内工业活动的影响。 相似文献
8.
[目的]了解潍坊市土壤重金属污染现状及其在空间上的分布规律,为该区土壤重金属污染防治和农业生产的合理安排提供指导。[方法]在土壤重金属污染调查的基础上,以ArcGIS为操作平台,采用地质积累指数分析潍坊市土壤重金属污染状况,并绘制空间分布图。[结果]潍坊市大部分地区土壤重金属未产生污染,但在某些地区镍的污染等级达到3级;8种重金属污染程度依次为:HgNiZnCrPbCdCuAs;土壤中Cd,Ni,Pb,Hg受土壤质地影响,Cd,Ni,Pb易在砂土中富集,Hg易在黏土中富集;重金属元素浓度与土壤pH值相关性较差;Hg的浓度与土壤有机质有着非常显著的正相关关系(p0.01);Ni污染存在着复合现象;重金属元素中,Cu,Cr,Ni在空间的分布主要集中于青州—临朐—昌乐交界处和安丘—诸城交界处。[结论]土壤重金属污染分布与人类活动有关,应加强地区交界处的环境管理力度。 相似文献
9.
Albert Ebo Duncan Nanne de Vries Kwabena Biritwum Nyarko 《Water, air, and soil pollution》2018,229(8):272
An investigative study was conducted to determine the heavy metal pollution in the sediment in the Pra Basin of Ghana from 27 sampling points during the dry and wet seasons using the geo-accumulation index (Igeo), enrichment factor (EF), and pollution load index (PLI). Sediments were acid digested and analyzed for the following selected metals: arsenic (As), lead (Pb), cadmium (Cd), zinc (Zn), manganese (Mn), total chromium (Cr), nickel (Ni), and iron (Fe) using the dual atomizer and hydride generator atomic absorption spectrophotometer (model ASC-7000 No A309654, Shimadzu, Japan). The metal concentrations (mg kg?1) in the sediments were as follows: As (0.175)?<?Cd (3.206)?<?Ni (79.927)?<?Zn (118.323)?<?Cr (216.708)?<?Mn (234.742)?<?Pb (335.381)?<?Fe (1354.513) in the dry season and As (0.002)?<?Cd (7.279)?<?Ni (72.663)?<?Zn (35.622)?<?Pb (135.863)?<?Cr (167.604)?<?Mn (183.904)?<?Fe (1138.551) for the wet season. The EF which is an indication of whether metal concentrations are due to anthropogenic activities shows enrichment at all site for the metals Cr, Pb, and Cd in the wet seasons. However, only 4 out of the 27 sites showed Ni enrichment in the wet season. Contrary to the wet season, only Pb and Cr recorded enrichment at all sites during the dry season. Fifteen out of the 27 sites recorded Cd enrichment and 24 out of the 27 sites recorded Ni enriched during the dry season. None of the sites were enriched with Fe, As, Zn, and Mn in either the dry or wet seasons. For both dry and wet seasons, the pollution load index for all the sites except one was at the background levels which is a sign of non-deterioration of the sites studied. In the wet season, the calculated Igeo reveals that the study area is not contaminated with respect to As, Zn, Fe, and Mn; uncontaminated to moderately contaminated with Cd; moderately contaminated with Cr; uncontaminated to moderately to heavily contaminated with Ni; and moderately to heavily contaminated with Pb. The dry season Igeo results reveal non-contamination of the study area with respect to As, Fe, and Mn; uncontaminated to moderately contaminated with Zn; moderately contaminated with Cr; uncontaminated to heavily contaminated with Cd; uncontaminated to extremely contaminated with Ni; and moderately to extremely contaminated with Pb. The high levels of Cd, Pb, and Cr in all the sites are due to unregulated illegal mining activities occurring in and around the study area. It is hoped that this study will prompt the basin management board to improve their management strategies in controlling unregulated illegal mining in the basin sediments. 相似文献
10.
Ralf Berghofer Wolfgang Wilcke Vladimír Linke&#x; Otmar Nestroy Wolfgang Zech 《植物养料与土壤学杂志》1997,160(4):469-474
The objective of this study was to investigate changes of total concentrations and various extract-defined Al and heavy metal fractions in Slovak agricultural soils during the last 25 years. We compared 7 stored soil samples collected between 1966 and 1970 with samples collected in 1994 at the same sites. Seven fractions of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined with a sequential extraction procedure in all samples. Total concentrations of Cd, Zn, Mn, Ni, and Cu were lower in the 1994 samples; those of Al, Fe, Pb, and Cr were higher. Based on the initial concentrations, the average total concentration changes were: Cd(-10,3%)<Zn(-7,2%)<Mn(-4,8%)<Ni(-2,3%)<Cu(-1,4%)<Al(+2,1%)<Fe(+2,9%)<Cr(+7,4%)<Pb(+8,3%). This row is consistent with the decrease in metal mobility. The differences in salt-extractable metals showed the same pattern; however, changes were more pronounced than for total concentrations. The results suggest that decreases during the last 25 years are caused by higher leaching than deposition rates and increases vice versa. The highest increase in Cr and Pb concentrations is observed in the EDTA-extractable fraction, which mainly characterizes organically bound metals. 相似文献
11.
酸雨地区蔬菜对重金属的吸收及重金属健康风险基准的估算 总被引：4，自引：0，他引：4
通过盆栽实验,以小白菜(上海青)、大白菜和萝卜为指示作物,研究了酸雨作用下Cu,Zn,Pb,Cd,Cr和Ni复合污染物在土壤-作物系统中的吸收与富集情况。结果表明,酸雨-重金属复合污染处理使Cu,Pb,Cr和Ni在蔬菜中积累量明显高于对照处理;Zn和Cd一般只有在复合污染处理中外源Zn或Cd含量较高时才明显高于对照处理。与对照相比,酸雨-重金属复合污染处理使Pb和Ni的富集系数增大,Cu的富集系数多数情况下增大,Cd的富集系数多数情况下减小,Zn和Cr富集系数的变化在不同蔬菜之间存在较明显的差异;重金属在不同蔬菜中的富集系数一般表现为萝卜>上海青>大白菜,蔬菜中不同重金属富集系数一般表现为Zn>Cd>Ni>Cu>Pb>Cr。酸雨-重金属复合污染条件下蔬菜中重金属积累量与其在土壤中总量之间的相关性均达到显著或极显著水平。以大宗蔬菜上海青、大白菜和萝卜为指示作物对酸雨地区蔬菜地中重金属的健康风险基准进行了估算,这对开展酸雨地区土壤重金属环境容量评价、重金属污染修复目标及地方性土壤环境质量标准的制订提供了参考依据。 相似文献
12.
应用实验生态方法研究了褶牡蛎对8种常见的重金属生物富集动力学特性,得出了褶牡蛎对重金属的生物富集系数、生物半衰期以及生物富集曲线。结果表明,到积累实验结束时褶牡蛎对Pb、Zn、Cd、Cr、Ni和Hg的生物富集系数分别是15．60、26．53、60．06、7．61、5．82和47．88,褶牡蛎对Cu和As的富集规律不明显,生物富集曲线分别为yPI7=0．4046e^0.1168xR^2=0．7378,yZn=0．0408x^2＋0．2909x＋59．969 R^2=0．9307,yGl=2．5263e^0.0867x R^2=0．7089,YCr=0．6832e^0.0942x R^2=0．8544,yNi=0．4178e^0.0714x R^2=0．6856和yHg=0．0015x^2＋0．0444x＋0：0644 R^2=0．8301,以积累实验结束时的生物富集系数为基准,褶牡蛎对这几种重金属的富集能力为Cd〉Hg〉Zn〉Pb〉Cr〉Ni;到释放实验结束时褶牡蛎对Pb、Zn、Cd、Cr和Hg的生物半衰期分别是23．1、13031．7、67,7、32．9和36．1d,褶牡蛎是Zn、Cd和Hg的强的净积累者,以释放实验结束时的生物半衰期为基准,褶牛十蛎对这几种重金属的排毒释放顺序为Pb〉Cr〉Hg〉Cd〉Zn。 相似文献
13.
Laurence Denaix Anne-Laure Thomas-Ch��ry Julie Balet Mohammed Benbrahim Jean-Michel Carnus 《Water, air, and soil pollution》2011,215(1-4):239-249
Granular bentonite has been assessed regarding its capacity to remove Hg(II), Cd(II) and Pb(II) from aqueous solutions. Sorption capacities, kinetics and the dependence of the sorption process on pH were determined. Fractional power, pseudo-first-order, pseudo-second-order and intra-particle diffusion equations were used to model the kinetics of metal adsorption. The pseudo-second-order model showed the best fit to experimental data. Different two-parameter sorption isotherm models (Langmuir, Freundlich, Temkin and Dubinin?CRadushkevich) were used to fit the equilibrium data. Freundlich's isotherm model gave the best fit to experimental data. The selectivity of granular bentonite towards these metals is Pb(II)?>?Cd(II)?>?Hg(II). The adsorption capacities of granular bentonite towards the metals expressed in milligramme metal per gramme granular bentonite are 19.45, 13.05 and 1.7 for Pb(II), Cd(II) and Hg(II), respectively (for an initial concentration of 100 mg metal/L). 相似文献
14.
This paper reports the results of a study focused on the metal (Cd, Co, Cr, Cu, Ni, Pb, Sb, U and Zn) distribution in soils and uptake and accumulation by earthworms Nicodrilus caliginosus (Savigny) from urban, peri-urban, green-urban and non-urban zones of Siena municipality (central Italy). The main goal was to define the influence of soil properties and metal soil contents on the uptake of these contaminants by earthworms. Data indicated that Cd, Cu, Pb, Sb and Zn soil contents increased in the following order: non-urban < green-urban < peri-urban < urban soils, suggesting that vehicular traffic affects the distribution of these metals. Pb and Sb were the main soil contaminants and their highest enrichments were found in urban sites where stop-and-go traffic occurs. Concentrations of these traffic-related metals in earthworms showed a distribution pattern similar to that in soil, suggesting that soil contamination influenced the uptake of Cd, Cu, Pb, Sb and Zn by N. caliginosus. There were significant positive correlations between Cd, Pb and Sb earthworm concentrations and their soil contents. The lack of correlation for Cu and Zn could be due to the physiological regulation of these elements by earthworms. Statistical analysis pointed out that the uptake and accumulation of Cd, Cu, Pb, Sb and Zn by earthworms were affected by some soil physicochemical properties such as the organic carbon and carbonate contents that are able to rule the bioavailability of metals in soils. 相似文献
15.
松嫩平原产油区农田土壤重金属含量及污染风险评价 总被引：1，自引：0，他引：1
16.
福建沿海农田土壤重金属污染与潜在生态风险研究 总被引：10，自引：1，他引：9
分析了取自福建沿海农田185件表层土壤样品的重金属含量与分布特征,采用连续提出的方法研究重金属元素的赋存状态。结果表明福建沿海稻田土壤中的Hg、Cd、As、Cr、Ni、Cu、Zn和Pb的平均含量分别为0.41mgkg-1、0.20mgkg-1、6.62mgkg-1、35.65mgkg-1、12.7mgkg-1、128.39mgkg-1、109.65mgkg-1和63.56mgkg-1。相对于区域土壤背景值与国家土壤环境质量标准,污染较突出的元素是Hg和Cd。有46%样品中的Hg含量高于土壤质量的Ⅱ标准值,有13%的样品的Cd高于土壤质量的Ⅱ标准值。Hg高含量的样品主要分布福州、漳州等城镇等附近,同时它在土壤中主要以有机结合态的形式存在,土壤中Hg含量的升高可能主要来自于后期污染的叠加。Cd高含量的样品的分布则较分散,并不都集中在工业活动区,同时它在土壤中是以残渣态和铁锰氧化物态的形式存在,说明其高含量可能更多是受到成土母质的地球化学背景影响。农田土壤中的Hg和Cd具有较高的生态风险。该区主要是栽种水稻,而水稻对Cd具有强吸收的特性,土壤酸化还会促进Cd的吸收。本区土壤呈酸性,所以Cd污染可能导致大米的食品安全应引起足够重视。 相似文献
17.
龙游硫铁矿区农田土壤重金属污染的空间 变异及在水稻中的积累 总被引：3，自引：0，他引：3
为了解浙江龙游硫铁矿区农田重金属污染状况,采集矿区265件农田土壤样品,分析8种重金属Cu、As、Hg、Zn、Cd、Ni、Pb、Cr元素全量,利用地统计学软件GS+9.0对研究区土壤各元素指标进行半变异函数拟合,并利用普通克里格法进行插值并绘制空间分布图。采集30件水稻籽粒样品,分析重金属在研究区中水稻籽粒的累积特征,并进行了健康风险评价。结果表明:矿区土壤中8种重金属元素的变异系数从0.72到1.76,离散程度较高。8种重金属的土壤空间半变异函数Cu、As、Hg元素符合指数模型,Zn、Cd、Ni、Pb符合球状模型,Cr符合高斯模型。元素Cu、Pb、Zn、Cr、Ni的块金值与基台值的比值C0/C0+C都小于0.25,说明空间变化主要受地质背景等因素影响;元素Cd、Hg和As的块金值与基台值的比值C0/C0+C在0.25~0.75之间,说明除了地质背景因素,人为活动等随机因素也有影响。矿区水稻籽粒中重金属Ni和Cd的变异系数最高,分别为0.95和0.87,说明Ni和Cd元素可能存在异常积累。矿区水稻籽粒对重金属的富集能力由大到小依次为Cd、Zn、Cu、Ni、As、Hg、Cr、Pb。健康风险评价结果表明矿区农田水稻籽粒中元素As、Cd的风险商大于1,存在潜在健康风险;而其他6种重金属Cu、Hg、Zn、Ni、Pb和Cr基本属于安全范围。 相似文献
18.
Yu. N. Vodyanitskii 《Eurasian Soil Science》2012,45(3):321-328
In line with the present-day ecological and toxicological data obtained by Dutch ecologists, heavy metals/metalloids form
the following succession according to their hazard degree in soils: Se > Tl > Sb > Cd > V > Hg > Ni > Cu > Cr > As > Ba. This
sequence substantially differs from the succession of heavy elements presented in the general toxicological GOST (State Norms
and Standards) 17.4.1.02-8, which considers As, Cd, Hg, Se, Pb, and Zn to be strongly hazardous elements, whereas Co, Ni,
Mo, Sb, and Cr to be moderately hazardous. As compared to the general toxicological approach, the hazard of lead, zinc, and
cobalt is lower in soils, and that of vanadium, antimony, and barium is higher. The new sequence also differs from that of
the metal hazard in soils according to the Russian standard on the maximal permissible concentration of mobile metal forms
(MPCmob): Cu > Ni > Co > Cr > Zn. Neither an MPCmob nor an APCmob has been adopted for strongly hazardous thallium, selenium, and vanadium in Russia. The content of heavy metals in contaminated
soils is very unevenly studied: 11 of them, i.e., Cu, Zn, Pb, Ni, Cd, Cr, As, Mn, Co, Hg, and Se, are better known, while
the rest, much worse, although there are dangerous elements (Ba, V, Tl) among them. 相似文献
19.
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
20.
《Communications in Soil Science and Plant Analysis》2012,43(21):2577-2594
The effect of addition of roadside pond sediments on heavy metal contents of flooded rice paddies was studied to investigate the yield of rice and uptake of heavy metal by rice straw and grain. Sequential extraction of heavy metals on sediments shows that the percentage contribution of metals in the labile fraction follows the order lead (Pb, 48%) > copper (Cu, 42%) > zinc (Zn, 31%) > cadmium (Cd, 16%) > chromium (Cr, 9%) > nickel (Ni, 6%). The risk assessment code (RAC) for pond sediment revealed that Cr and Ni were found in the low-risk zone, Zn and Cd in the medium-risk zone, and Cu and Pb in the high-risk zone. However, though the heavy metal concentration in rice grain does not exceed the range acceptable for human consumption, it still represents a significant additional source of heavy metals in the diet. The addition of pond sediment significantly increased the rice yield over control. Therefore, pond sediment would be a valuable resource for agriculture if it is properly used. 相似文献