Lead,Zn, and Cd in slags,stream sediments,and soils in an abandoned Zn smelting region,southwest of China,and Pb and S isotopes as source tracers

Purpose  

Smelting activity produced tons of slags with large quantities of highly toxic metals, resulting in contamination in adjacent soils and sediments as well. This study investigated the fractionation and sources of metals Pb, Zn, and Cd in polluted soils and sediments in a region with once prosperous Zn smelting activities in southwestern China. Soils with varying land uses were of a special concern due to their connection to the food chain. Obtained data would offer a valuable reference to the development of land-use management strategy in this region.     

长春市城区土壤中Pb、Cu、Zn、Cd及Cr化学形态特征

为弄清长春市城市土壤中Pb、Cu、Zn、Cr及Cd的化学形态分布特征,系统采集了26件城市表层(0~20 cm)土壤样品,采用连续提取法对重金属各化学形态含量进行了测定。结果表明:Pb、Zn、Cu及Cr主要以残渣态存在,其次是铁锰氧化物结合态、腐殖酸结合态和强有机结合态占有次要地位,离子交换态和水溶态所占比例均较低;Cd则主要以碳酸盐结合态存在,同时,水溶态和离子交换态所占比例较高。残渣态Pb和Zn在城区表层土壤中所占比例较近郊土壤中略有下降,但幅度不大,除Cu外,其余各元素易迁移、高生物有效性的水溶态在城区表层土壤中所占比例略有上升。Pearson相关分析结果表明,各元素残渣态与全量均呈极显著正相关,其它各活性态与全量间的相关程度与重金属种类有关。土壤pH值和Fe、Mn含量对重金属的化学形态的影响也与重金属种类有关,而且,同一重金属的不同存在形态受土壤pH值和Fe、Mn含量的影响程度也不同。     

Modelling of Cd, Cu, Ni, Pb and Zn uptake, by winter wheat and forage maize, from a sewage disposal farm

Abstract. A predictive model of metal concentrations in crops was developed to optimize soil liming and sludge application strategies at a dedicated sewage sludge disposal site. Predictions of metal concentrations in plant tissue were derived from measured values of soil metal concentration, humus content and soil pH. The plant and soil data used to parameterize the model were collected on site using quadrat sampling of mature crop and underlying topsoil. The uptake model was used to map predicted metal concentrations in wheat grain and forage maize based upon a database of soil characteristics (metal content, % humus and pH) measured as part of a routine geochemical survey of the site. The effect of a management strategy to modify uptake of Cd by wheat by changing soil pH was investigated. The effect of soil dust adhering to maize plants at harvest was also simulated to investigate the importance of this pathway for Cd transfer to animal feed such as silage.
The model gave satisfactory predictions for uptake of Cd and Zn but less useful simulations for Pb, Cu and Ni. The results for Cd uptake showed a greater dependence on soil pH in the case of wheat in comparison to maize. It is suggested that, for the study site, liming to pH 7.0 will reduce Cd concentrations in wheat grain to within EC legal standards. However the Cd content of maize may still exceed these guidelines, with a relatively minor contribution from contamination with soil dust.     

重金属单一污染对龙须草叶绿素含量和抗氧化酶系统的影响

盆栽试验的结果表明:Cd、Pb、Cu、Zn和As单一污染处理时龙须草叶绿素含量随着重金属处理浓度的增加呈现先升后降的趋势,但其总叶绿素含量和叶绿素a/b比值均低于对照;龙须草SOD的活性随着Zn、As单一污染处理浓度增加呈现先升后降的趋势,而随着其它三种重金属处理浓度的增加呈现下降趋势;龙须草CAT和POD的活性随着As处理浓度的增加呈现出上升趋势,而随着其它四种重金属处理浓度的增加呈现先升后降趋势。     

Phytoavailability of Some Micronutrients (Zn and Cu), Heavy Metals (Pb,Cd), and Yield of Rice Affected by Sewage Sludge Perennial Application

A study was conducted as a split-plot arrangement based on a randomized complete block design with three replications to test sewage sludge (SS) influence on yield and phytoavailability of lead (Pb), cadmium (Cd), zinc (Zn), and copper (Cu) by rice. The results indicated that fertilizer (main factor) and application periods (subfactor) affected studied traits. Three years of application of 40 ton ha^?1 SS + 50% chemical fertilizer (CF) gave the greatest paddy yield. The greatest Cu uptake by grain (10.38 ppm) occurred with 3 years application of 20 ton ha^?1 SS. With application of 40 ton ha^?1 SS + 50% CF, the greatest contents of Cd in root and Pb in shoots were recorded. The greatest accumulations of Cd in shoot and Zn in grain (30.56 and 25.81 ppm, respectively) were determined with the 20 ton ha^?1 SS treatment, as well. The greatest concentrations of Pb and Cd in grain (102.2 and 14.78 ppm, respectively) and Pb in root (552.2 ppm) were obtained with 3 years of application of 40 ton ha^?1 SS + 50% CF.     

热带土壤上连续9年施入污水污泥后重金属Zn, Cd和Pb的分离研究

A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University, Brazil, to evaluate the phytoavailability of Zn, Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years, using the sequential extraction and organic matter fractionation methods. During 2005-2006, maize (Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates. The treatments consisted of four sewage sludge rates (in a dry basis) : 0.0 (control, with mineral fertilization), 45.0, 90.0 and 127.5 t ha^-1, annually for nine years. Before maize sowing, the sewage sludge was manually applied to the soil and incorporated at 10 cm depth. Soil samples (0-20 cm layer) for Zn, Cd and Pb analysis were collected 60 days after sowing. The successive applications of sewage sludge to the soil did not affect heavy metal (Cd and Pb) fractions in the soil, with exception of Zn fractions. The Zn, Cd and Pb distributions in the soil were strongly associated with humin and residual fractions, which are characterized by stable chemical bonds. Zinc, Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.     

蚯蚓对印度芥菜修复Zn、Pb污染土壤的影响

以褐土为供试土壤,分别加入不同浓度梯度Zn2+(0,100,200,400 mg kg^-1)或Pb2+(0,200,400,800 mg kg^-1)模拟土壤污染,设置添加蚯蚓与不添加蚯蚓处理,通过盆栽实验,研究蚯蚓对印度芥菜生长量和重金属吸收量的影响,旨在探讨蚯蚓在植物-土壤系统中影响重金属迁移转化的作用机理,为蚯蚓在植物修复技术的实践与完善提供理论参考。结果表明:(1)在Zn、Pb污染土壤中,蚯蚓生长率分别降低3%～24%、6%～29%;(2)蚯蚓活动可以降低土壤的pH,显著增加土壤中Zn的有效态含量;(3)蚯蚓活动显著增加了印度芥菜地上部生物量(22.6%～88.6%鲜重,31.3%～122%干重)和印度芥菜地上部Zn的浓度及Zn和Pb的吸收量。印度芥菜地上部重金属浓度和吸收量与土壤中DTPA提取态含量呈极显著正相关(P <0.01),与土壤pH呈负相关。(4)蚯蚓对重金属的活化和对植物生长的促进是解决植物修复瓶颈问题的有效手段。     

田块尺度污染农田土壤铅、镉和砷含量的空间变异及其对土地利用的启示

为了探明铅冶炼污染区田块尺度下农田土壤重金属含量的空间变异及其对污染农田土壤安全利用的意义,在某冶炼厂附近一面积为4800 m2的农田用网格法采集120个0~20 cm土样,测定样品镉、铅和砷含量。研究表明,研究区土壤中存在砷、镉和铅的积累。从平均污染指数来看,以镉的积累程度最大,铅次之、砷最小。土壤全镉含量的变化范围为1.10~3.84 mg kg^-1,镉含量处于1.10~2.27 mg kg^-1之间的样品占97.50%。从重金属空间分布上看,镉和铅含量的空间分布有较高的一致性,均是研究区北部和南部含量较高,中间区域含量较低。相关分析表明,土壤镉和铅含量之间存在显著正相关(P <0.01)。根据土壤铅含量计算稳定铅时所用普通过磷酸钙的用量范围为0.312~0.419 kg m^-2,平均值为0.367 kg m^-2。根据其他研究者得到的土壤全镉含量与小麦籽粒镉含量的相关方程计算,不同方程得到的小麦籽粒镉含量结果有很大差异,较可信的小麦籽粒镉含量变化范围为0.095~0.814 mg kg^-1。采样区中部为小麦籽粒镉含量较低且铅稳定剂需要量较低区域。以上结果表明,研究区田块尺度下土壤镉含量存在较大的空间变异,且土壤镉含量的空间变异导致小麦籽粒镉含量可能存在较大的空间变异。     

商品大米中Cd、Pb、Cr的污染状况及健康风险评价

为了解本地商品大米中重金属的污染情况,采用微波消解法和电感耦合等离子体原子发射光谱（ICP-AES）法,对144个大米样品进行Cd、Pb和Cr含量的检测,采用单项污染指数和内梅罗综合指数法对其污染状况和健康风险进行分析评价.结果表明,样品中Cd、Pb和Cr的超标率分别为0.69%、27.78%和34.03%.无等级大米中3种重金属的超标率高于有等级大米,但差异不显著.本土商品大米样品中Cd的含量显著高于外省样品,Pb含量差异不显著,Cr的含量显著低于外省样品.144个样品中处于安全级别的样品仅占63.89%.健康风险评价结果显示,当地居民通过食用大米实际摄入Cd和Pb的量都低于FAO/WHO推荐的每人每日的允许摄入量,不存在严重的健康风险,但却存在Cr的健康风险问题.     

地质统计学评估伊朗伊斯法罕城市采矿过渡区近地表土壤上铅锌镉的污染

Due to the lack of regulation and environmental education and awareness, Sepahanshahr located in vicinity of Isfahan City, central Iran, is now a rapid growing residential area suffering from the considerable consequences of poorly regulated mining activities operating in its vicinity. A survey was carried out on soil Pb, Zn and Cd concentrations around Sepahanshahr Town to explore the spatial structure of Pb, Zn and Cd distribution and to map their concentrations using geostatistical techniques. 100 near-surface soil samples were collected and analyzed for Pb, Zn and Cd and some related soil physical and chemical variables such as pH, organic matter content, electrical conductivity, and clay, silt and sand contents. The variography results showed a strong spatial dependency in heavy metals concentration due to the dilution effects of natural factors including atmospheric dispersion and precipitation. The almost same range values calculated for both ln-transformed Pb and sand data suggested presence of spatial co-regionalization. However, ln-transformed Zn data showed a shorter spatial dependency among the three tested heavy metals. Kriged maps of all three heavy metals showed a strong gradient of contamination around the three mining sites activating in the area. The results of this study provide insight into identification of the extent and spatial variability of Pb, Zn and Cd pollution in the mining sites and surrounding urban areas.     

用突变点检测方法预测木生境下污染土壤中的可提性镉、铅和锌

Accumulation of heavy metals in soils poses a potential risk to plant production, which is related to availability of the metals in soil. The phytoavailability of metals is usually evaluated using extracting solutions such as salts, acids or chelates. The purpose of this study was to identify the most significant soil parameters that can be used to predict the concentrations of acetic and citric acid-extractable cadmium (Cd), lead (Pb) and zinc (Zn) in contaminated woody habitat topsoils. Multiple linear regression models were established using two analysis strategies and three sets of variables based on a dataset of 260 soil samples. The performance of these models was evaluated using statistical parameters. Cation exchange capacity, CaCO3, organic matter, assimilated P, free Al oxide, sand and the total metal concentrations appeared to be the main soil parameters governing the solubility of Cd, Pb and Zn in acetic and citric acid solutions. The results strongly suggest that the metal solubility in extracting solutions is extractable concentration-dependent since models were overall improved by incorporating a change point. This change point detection method was a powerful tool for predicting extractable Cd, Pb and Zn. Suitable predictions of extractable Cd, Pb and Zn concentrations were obtained, with correlation coefficient (adjusted r) ranging from 0.80 to 0.99, given the high complexity of the woody habitat soils studied. Therefore, the predictive models can constitute a decision-making support tool for managing phytoremediation of contaminated soils, making recommendations to control the potential bioavailability of metals. The relationships between acetic and/or citric acid-extractable concentrations and the concentrations of metals into the aboveground parts of plants need to be predicted, in order to make their temporal monitoring easier.     

Cd、Pb、Cu、Zn、As复合污染对杂交水稻苗的联合生理毒性效应及临界值

通过室内土培试验,研究了不同浓度的Cd、Pb、Cu、Zn、As等5种重金属复合污染对水稻苗的联合生理毒性效应,并对其临界值进行了探讨。结果表明:5种重金属污染对水稻苗的联合生理毒性效应随其污染浓度的增加而显著增强,剂量—效应关系明显。除处理(1)外,其余各处理对水稻苗体的诸项生长指标的抑制均达到了极显著的程度(P<0.01),且对根长的抑制明显大于苗长。随着复合重金属污染浓度的增大,水稻苗叶片中叶绿素含量急剧减少;丙二醛(MDA)含量迅速增加;POD和SOD酶活性呈先升后降的变化趋势。铅锌尾矿和矿毒水污染对水稻苗生长和各项生理生化指标的影响也均达到了极显著程度,但在二者污染下,POD和SOD酶活性均高于对照,铅锌尾矿的毒性效应大于矿毒水。以酶活性为参考指标,可以将土壤环境质量二级标准上限值设定为土壤中Cd、Pb、Cu、Zn、As等5种重金属对该水稻品种的临界毒性效应值。     

不同畜禽粪便好氧堆肥过程中重金属Pb Cd Cu Zn的变化特征及其影响因素分析

畜禽粪便中的重金属含量及其生物有效性是限制其农业利用的重要因素。采用好气模拟培养方法对6种畜禽粪便好氧堆肥过程中Pb、Cd、Cu、Zn的总量以及生物有效性动态变化进行研究探讨,并分析了影响重金属生物有效性的因素。结果表明,根据现有的国际以及我国农用污泥农用标准,某些粪便中存在着Cd、Cu、Zn含量超标,由于饲料受重金属污染的不同,造成不同畜禽粪便中不同的重金属含量差异性较大。堆肥过程中,由于挥发性物质的挥发作用,4种重金属含量均呈现增加现象,尤其是在0～14 d的堆肥中增加量最高;而生物有效性重金属占其全量重金属的比例呈现先增加而后下降的趋势,除仔猪粪外,堆肥均能降低重金属生物有效性部分的比例,这将有利于降低其农业利用的风险。温度和水溶性碳对堆肥过程中4种重金属的生物有效性部分重金属相对含量的变化有着显著的影响。     

Determination of Thallium and Other Elements (As,Cd, Cu,Mn, Pb,Se, Sb,and Zn) in Water and Sediment Samples from the Vicinity of the Zinc-Lead Smelter in Poland (3 pp)

Background, Goal and Scope   The aim of this study was to check the concentration of some elements in water samples collected near Pb-Zn mining and smelting works and comparison of the obtained data with results achieved for sediment samples originated from the same reservoirs. Objective   Here, 8 water samples and 3 bottom sediments collected from water reservoirs in the vicinity of 3 big Polish Pb-Zn smelters were analysed.Methods   Water analysis was performed after filtration through a 0.45 &#181;m filter and pH adjustment to 2. For decomposition of dried sediment samples, microwave assisted digestion with total dissolution of silicate matrix was applied. The elements studied were determined using ICP-MS and ICP-OES methods. Results and Discussion   The concentrations of most studied elements in water samples were on the 0.X &#181;g/L level, while only the contents of Tl, As, Mn, Cd, Pb and Sb in two water reservoirs were above the limits established for drinking water. The content of studied metals in sediments was in a wide range from X mg/kg (Se and Sb) to X000 mg/kg (Pb and Zn).Conclusions  and Recommendation. The study indicates that the impact of Tl, As, Cd, Cu, Mn, Pb, Zn, Se and Sb on bottom sediments is much more extensive than on the water in ponds located in the vicinity of a post-flotation waste heap. Monitoring of surface and underground waters, if limited only to the dissolved elements, can lead to faulty conclusions about environmental pollution. The bottom sediments mainly contain easily mobilised phases, and water-sediment equilibrium could be changed easily.     

Speciation of Zn,Cu, and Pb in the soil depending on soil texture and fertilization with sewage sludge compost

Background, aim, and scope  Heavy metal (HM) mobility in soil depends on the HM species in it. Therefore, knowledge of the HM speciation in soil allows the prediction of HM impact on the environment. HM speciation in soil depends on the metal chemical origin, soil texture, and other factors such as the origin and level of soil contamination. Recently, the problem of organic waste utilization is of great importance as the amount of this recyclable material is continually increasing. One of the possible ways of recycling is the use of processed organic wastes for agricultural needs. In this research, aerobically composted sewage sludge was used, the utilization of which is of essential importance. But one of the most serious restrictions is HM transfer from such material to the soil. Therefore, a prediction of HM mobility in soil and its migration in the environment is an important issue when using sewage sludge compost (SSC) in agriculture. Zn, Cu, and Pb speciation was performed according to the modified methodology of Tessier et al. (Anal Chem 51:844–851, 1979) in two different (sandy and clay) soils with background HM amounts and in soil samples amended with aerobically digested SSC to find out the predominant species of the investigated HM and to predict their potential availability. Materials and methods  The modified method of sequential extraction initially proposed by Tessier et al. (Anal Chem 51:844–851, 1979) is designed for HM speciation into five species where HM mobility decreases in the order: F1—exchangeable HM (extracted with 1 M MgCl₂ at an initial pH of 7 and room temperature), F2—carbonate-bound HM (extracted with 1 M CH₃COONa buffered to pH 5 at room temperature), F3—Fe/Mn oxide-bound HM (extracted with 0.04 M NH₂OH·HCl at an initial pH of 2 at 96°C), F4—organic matter-complexed or sulfide-bound HM (extracted with 0.02 M HNO₃ and 30% (v/v) H₂O₂ at a ratio of 1:1 and an initial pH of 2 at 85°C), and F5—the residual HM (digested with HNO₃, HF, and HCl mixture). After digestion, HM amounts in solution were determined by atomic absorption spectrometry (AAS ‘Hitachi’). Mixtures of uncontaminated soils of different textures (clay and sandy) with SSC in ratios 20:1, 10:1, and 5:1 were used to simulate the land application with SSC. During a period of 7 weeks, changes in Zn, Cu, and Pb content within species were investigated and compared weekly in soil–SSC mixtures with their speciation in pure soil and in the SSC. Results  Results in the SSC showed that more HM were found as mobile species compared to the soils, and in sandy soil, more were found in the mobile species than in clay soil. But the HM speciation strongly depended on the metal chemical origin. According to the potential availability, HM ranked in the following order: Zn>Pb>Cu. Zinc generally occurred in the mobile species (F1 and F3), especially in sandy soils amended with SSC, and changes of the Zn speciation were insignificant at the end of the experiment. Pb transfer to insoluble compounds (F5) was evident in the SSC–soil mixtures. This confirms that Pb is extremely immobile in the soil. However, the observed increase of Pb amounts in the mobile species (F1 and F2) during the course of experiment shows a critical trend of Pb mobilization under anthropogenic influence. Copper in the soil–SSC mixtures had a trend to form compounds of low mobility, such as organic complexes and sulfides (F4) and nonsoluble compounds (residual fraction F5). Initially, the amounts of mobile Cu species (F1 and F2) increased in the soils amended with SSC, probably due to the influence of SSC of anthropogenic origin with lower pH and high organic matter content, but Cu mobility decreased nearly to the initial level again after 3–4 weeks. Hence, the soil has a great specific adsorption capacity to immobilize Cu of anthropogenic origin. Discussion  Zn mobility and environmental impact was greater than that seen for Cu and Pb, while mobility of both Cu and Pb was similar, but variable depending on soil texture and contamination level. The effect on the shift of HM mobility and potential availability was greater in sandy SSC-amended soils than in clay soils and increased with an increasing amount of SSC. Conclusions  Usage of SSC for land fertilization should be strictly regulated, especially regarding Pb amounts. Recommendations and perspectives  The influence of SSC on Cu and Zn mobility and potential availability was more significant only in the case of sandy soil with a higher SSC ratio. Nevertheless, this waste product of anthropogenic origin increased Pb mobility in all cases in spite of only moderate Pb mobility in SSC itself. Therefore, aerobic processing of sewage sludge must be strictly regulated, especially regarding Pb amounts, and SSC ratios must be in control regarding HM amounts when using it for on-land application.     

湘北某镇农田土壤―水稻系统重金属累积和稻米食用安全研究

为研究采矿炼矿活动对农田和稻谷重金属累积的影响,评估其对人体健康的潜在风险,对湖南北部某镇一硫铁矿附近典型污染稻田土壤—水稻系统8种重金属(锰(Mn)、铜(Cu)、锌(Zn)、钴(Co)、镍(Ni)、铬(Cr)、镉(Cd)和铅(Pb))含量进行监测。结果表明:该冶炼厂附近稻田土壤Cd污染最严重,单因素污染指数达12.85,为重度污染;Cu、Zn、Co和Ni为轻度污染。土壤重金属综合污染指数达重度污染。重金属生物富集因子的研究表明:Cd和Mn极易从土壤中被水稻根系吸收,尤其Cd被水稻根系吸收的能力远超其他重金属元素;而Cu、Pb、Co、Cr、Zn和Ni相对不易被水稻根系吸收。重金属在植株组织的分配也表现出差异:Pb、Co、Cu、Cd和Cr被水稻根吸收后,主要蓄积于根部,在根部的浓度百分比分别为82.5%、70.6%、64.8%、59.4%和57.5%;Mn、Zn和Ni被根系吸收后,会迅速向地上部组织迁移。研究区稻田出产的糙米Cd污染严重,Cd的超标率达100%,"镉米"的产出率达53.3%。糙米Cu和Ni的超标率也分别达到了40%和86.7%。若居民食用研究区稻米,每人每日摄入Cd量高于FAO/WHO推荐的标准限值5.9倍,表明研究区稻米存在很大安全风险。     

中国农田土壤重金属富集状况及其空间分布研究

梳理国内外农田土壤重金属污染修复的研究热点及最新进展,总结有效的修复治理技术及实际效果,为我国重金属污染农田的安全利用提供依据。利用COOC和VOSviewer文献计量工具,以中国知网（CNKI）全文数据库和Web of Science核心合集数据库（WOS）为数据检索源,对2010 ~ 2021年农田土壤重金属污染修复与治理领域的相关文献进行知识图谱的可视化分析。在2010 ~ 2021年间,国内外对农田土壤重金属修复研究文献数量呈快速增长态势,且英文文献的增长率明显高于中文文献。我国在农田土壤重金属污染修复领域的研究占有绝对领先地位（发文量占比率最高,达26.8%）,对全球重金属污染治理工作的贡献最大。国内外在该领域发文期刊（TOP 3）有：《农业环境科学学报》《安徽农业科学》《环境工程学报》《Environmental Science and Pollution Research》《Chemosphere》《Journal of Hazardous Materials》。关注的重金属种类主要是镉、铅、砷等。国内外的研究学者呈“小聚体、大分散”的特点,合作关系有待进一步加强。通过关键词分析表明,固化/稳定化技术和植物修复技术在中英文献中的研究比重均较高（约80%）,是目前研究的重点和热点。从田间试验的修复效果来看（以镉污染为例）,低积累作物品种种植（籽粒降镉率达67.9%）、无机－有机组配（42.7%）以及叶面阻控技术（39.9%）在降镉方面表现出较好的效果,未来还需将其与农艺措施（如间套作、水分调控）、微生物菌剂等联合配施,以实现更好的田间修复和治理效果。     

Use of the BCR three-step sequential extraction procedure for the study of the partitioning of Cd, Pb and Zn in various soil samples

A slightly modified three-step sequential extraction procedure proposed by the Community Bureau of Reference (BCR) for analysis of sediments was successfully applied to soil samples. Contaminated soil samples from the lead and zinc mining area in the Mezica valley (Slovenia) and natural soils from a non-industrial area were analysed. The total concentrations of Cd, Pb and Zn and their concentrations in fractions after extraction were determined by flame or electrothermal atomic absorption spectrometry (FAAS, ETAAS). Total metal concentrations in natural soils ranged from 0.3 to 2.6 mg kg^-1 for Cd, from 20 to 45 mg kg^-1 for Pb and from 70 to 140 mg kg^-1 for Zn, while these concentrations ranged from 0.5 to 35 mg kg^-1 for Cd, from 200 to 10000 mg kg^-1 for Pb and from 140 to 1500 mg kg^-1 for Zn in soils from contaminated areas. The results of the partitioning study applying the slightly modified BCR three-step extraction procedure indicate that Cd, Pb and Zn in natural soils prevails mostly in sparingly soluble fractions. Cd in natural soils is bound mainly to Fe and Mn oxides and hydroxides, Pb to organic matter, sulphides and silicates, while Zn is predominantly bound to silicates. In contaminated soils, Cd, Pb and Zn are distributed between the easily and sparingly soluble fractions. Due to the high total Cd, Pb and Zn concentrations in contaminated soil close to the smelter, ! and their high proportions in the easily soluble fraction (80% of Cd, 50% of Pb and 70% of Zn), the soil around smelters represents an environmental hazard.     

Monitoring of soil erosion and assessment for contribution of sediments to rivers in a typical watershed of the Upper Yangtze River Basin

An assessment of the effectiveness of soil conservation practices is very important for watershed management, but the measurement over a small area does not necessarily represent the truth over a large area. Monitoring of soil erosion and analysis of sediment delivery were carried out in the Lizixi watershed (which is typical of the Upper Yangtze Basin, China), using remote sensing and a geographic information system (GIS). Land‐use and land‐cover maps were prepared by an interpretation of 1986 and 1999 images from SPOT and Landsat TM. Slope‐gradient maps were created from digital elevation model (DEM), while merged images of SPOT and Landsat TM were used to obtain land‐use information. The area of soil erosion was classified by an integration of slope gradients, land‐use types and vegetation cover rates, and soil erosion rates and their changes were calculated in a grid‐based analysis using an Erdas GIS. The change in sediment delivery ratio was estimated based on the changes in soil erosion rates from both monitoring and the truth survey. There was a reduction in soil erosion rate of 4·22 per cent during a 13‐year period after soil conservation practices were adopted in the Lizixi watershed. The amount of sediments transported into rivers has decreased by 51·08 per cent during the same period due to an integrated application of biological and engineering measures. The comparison of soil erosion severity between pre‐conservation and post‐conservation revealed that soil loss has been obviously diminished and the measures were quite effective. Copyright © 2004 John Wiley & Sons, Ltd.     

Suitability of inorganic and organic amendments for in situ immobilization of Cd,Cu, and Zn in a strongly contaminated Kastanozem of the Mashavera valley,SE Georgia. I. Effect of amendments on metal mobility and microbial activity in soil

The aim was to find an adequate, cost‐efficient in situ remediation technique for the Mashavera valley, a mining area in SE Georgia heavily contaminated with Cd, Cu, and Zn. A 12‐month experiment was conducted to test: iron grit, natural zeolite, biochar, and Divergan® (a scavenger) for soil melioration. The amendments were added in different concentrations to the topsoil of a Kastanozem. Mobile metal concentrations decreased with increasing concentrations of amendments in the sequence Divergan® >> iron grit ≈ natural zeolite > biochar. In the same order amendments enhanced activities of soil microbial respiration, alkaline phosphatase, and dehydrogenase; microbial C also followed this trend. A sequential extraction confirmed a shift from easily mobilized to heavily bound fractions. The addition of 2% (w/w) of Divergan® was sufficient to lower mobile trace metal concentrations below German thresholds by chemisorption, and soil microbial activity was significantly increased. The effects of all other treatments were at a much lower level and not found suitable due to needed application rates.