Cleaning heavy metal contaminated soil with soluble humic substances instead of synthetic polycarboxylic acids

Abstract

Soils contaminated with heavy metals constitute a serious and widespread ecological problem but to clean such soils requires strong chemicals such as polycarboxylates; frequently ethylenediaminetetraacetic acid and nitrilotriacetic acid are used. However, these compounds are synthetic and toxic and their replacement by natural products such as soluble humic substances as washing agents for cleaning heavy metal polluted soils would be environmentally very attractive. In fact, such a replacement seems possible at least on cadmium and copper contaminated soil inasmuch as humic substances, depending on the concentration, were found to extract up to 45% and 54% of total cadmium and copper from a highly contaminated calcareous soil. Even though higher amounts of the two metals were extracted by ethylenediaminetetraacetic acid and nitrilotriacetic acid, the humic substances undoubtedly extracted the most reactive fractions. However, the humic substances extracted only 4% of total lead and 17% of total nickel, whereas the percentages for the synthetic polycarboxylates were about 30% for nickel and lead. Ethylenediaminetetraacetic acid and nitrilotriacetic acid may therefore be replaced by humic substances as washing agents for cadmium, copper and maybe nickel contaminated soils, whereas they seem unsuited for cleaning lead contaminated soils, at least if the soils are as calcareous as the soil tested.     

Extraction methods for studying the fractional composition of heavy metals in soils and their comparative assessment

The data on the fractional composition of the heavy metal (HM) compounds in the plow horizon of a loamy-sandy soddy-podzolic soil investigated by different methods of fractionation are presented. The use of the BCR (Community Reference Bureau) scheme did not fully allow revealing some regularities governing the state of the copper, zinc, nickel, and lead in the soil. This system does not reflect the existing ideas concerning the interaction between the HMs and soil components. The chemical properties of the elements are manifested more distinctly when the scheme of the HM fractionation elaborated in our country is used. Despite some disadvantages, the method of chemical fractionation of metal compounds permits one to obtain adequate and useful information on the state of the microelements and HMs in soils.     

Forms and distribution of heavy metals in soils of the Axios delta of northern Greece

Abstract

Distribution and availability of heavy metals to plants is important when assessing the environmental quality of an area. The objectives of this study, conducted in 1992–1993, were: a) to determine the levels of the heavy metals, cadmium (Cd), chromium (Cr), copper(Cu), lead (Pb), manganese (Mn), nickel (Ni), and zinc (Zn), in the soils of the Axios Delta (a Ramsar wetland site in Northern Greece) so that the degree of pollution could be ascertained, b) to identify the various heavy metal forms present in soils using a fractionation scheme based on sequential extraction, and c) to find possible dependence on soil physicochemical properties. Total heavy metal content of the soils studied was generally higher than the levels reported in the literature for similar soils, suggesting some degree of pollution with heavy metals. The exchangeable forms of the heavy metals, however, were very low indicating that under present conditions, the availability of the heavy metals to plants is at a minimum. Most of the heavy metals occurred in forms that are considered immobile constituents of inorganic minerals or carbonate compounds. Only Cu and Zn were present in appreciable quantities as organically‐based forms that can become potentially available under certain conditions. Spatial distribution of Zn and Cu was related to the organic matter distribution, and there were indications suggesting that the immobile fraction of the heavy metals was adsorbed on to Mn‐oxides.     

Examining the Effects of the Destroying Ammunition,Mines, and Explosive Devices on the Presence of Heavy Metals in Soil of Open Detonation Pit: Part 1—Pseudo-total Concentration

This paper presents the results of determining the pseudo-total concentration of five heavy metals in the soil on which the destruction of ammunition, mines, and explosive devices is carried out by the method of open detonation. In the analyzed area, the concentrations of cadmium, lead, nickel, copper, and zinc were determined, while from the physical properties of the soil were determined the granulometric composition and the pH. The aim of the study is to determine the origin and total load on heavy metals and, based on that, to assess the dangers and impact of the site in terms of the soil pollution by heavy metals. In accordance with the regulations of Bosnia and Herzegovina, the results of the soil testing showed a significant load of copper (up to seven times) and cadmium (up to six times), and exceeding the allowed values for nickel and zinc in some places. Lead was the only metal whose concentration was within the maximum allowed and according to that the soil was classified as unpolluted. A sample of soil from the edge of the pit is the only sample in which all heavy metals, except Ni, were within the maximum allowable concentration. In regard to the concentration of the examined metals, the soil of the pit is classified as medium polluted from the aspect of copper, cadmium, and nickel and highly contaminated with zinc. The concentrations of copper and zinc in the examination area correspond to contaminated soil that represents ecological risk, which requires soil remediation.     

Tea Plantation–Induced Activation of Soil Heavy Metals

Abstract

The accumulation of heavy metals in tea leaves is of concern because of its impact on tea quality. This study characterized long‐term changes of soil properties and heavy‐metal fractions in tea gardens and their effect on the uptake of metals from soils by the plants. Soil and tea leaf samples were collected from five plantations with a history of 2–70 years in Jinghua, Zhejiang Province, southeast China. The six chemical fractions (water‐soluble, exchangeable, carbonate‐bound, organic‐matterbound, oxide‐bound, and residual forms) of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), nickel (Ni), manganese (Mn), lead (Pb), and zinc (Zn) in the soils were characterized. Dissolved organic‐matter accumulation in the soils and effects of low‐molecular‐weight organic acids on solubility of soil heavy metals were also tested. Long‐term tea plantation use resulted in accumulation of dissolved organic matter, decrease of soil pH, and elevation of water‐soluble and exchangeable metal fractions, thereby increasing metal contents in leaves. The influence was more significant when soil pH was less than 4.4. The results indicated that both acidification and accumulation of dissolved organic matter induced by tea plantations were also important causes of increased accumulation of the metals in the tea leaves. This was particularly true for the soils polluted with low concentration of heavy metals, because availability of the metals in these soils was mainly controlled by pH and dissolved organic matter.     

粤西黄铁矿区铊-铅污染土壤的环境质量研究

以云浮硫铁矿开采场和尾渣堆放区为研究对象,采用HNO3-H2O2-HClO4-HF混酸-微波消解处理土壤样品,运用电感耦合等离子体质谱（ICP-MS）测定土壤样品中重金属的含量,研究了开采场附近土壤表层、尾渣堆放区土壤剖面的铊、铅、镍、铜、锌、镉等毒害重金属的含量。结果表明,云浮硫铁矿开采活动给矿区土壤环境带来了严重的危害。与中国土壤环境背景值相比,土壤中重金属含量最高可为背景值的35倍。运用Muller地积指数对土壤重金属污染现状进行了系统的环境风险评估,证实目前云浮矿区土壤中存在不同程度的铊、铅、铜、锌、镉等毒害重金属污染,其中,铊、铅的污染最为严重,镉、锌等达到中度污染至强污染,且污染已经渗透至土壤深层,特别是毒害性极强的重金属铊,生态环境受到严重危害。     

The effect of sewage‐sludge on the heavy metal content of soils and plant tissue

Abstract

Domestic sewage sludge applied to farm fields at a rate of 44.9 kg/ha in a mixture with lime and sawdust was found to increase the soil levels of cadmium, chromium, copper, lead, mercury, nickel and zinc. The average levels in sludge treated soil were: 0.11, 0.56, 3.59, 2.72, 0.068, 1.49 and 2.57 ppm, respectively. The increases were small and the overall loading factors were well below recommended maximums. The uptake of these heavy metals by grass and legume plants was variable with cadmium, copper and zinc levels being higher in those plants growing in the sludge treated soils but only copper was significantly higher. The heavy metal contents found were all within the levels normally found in grass and legume plants. The higher mean concentration in plants growing on the sludge treated soils were cadmium 0.495; chromium 1.22; copper 12.3; lead 1.54; mercury 0.022; nickel 4.08 and zinc 28.4 ppm.     

Einflußgrößen der Schwermetallöslichkeit und -bindung in Böden

Solubility and retention of heavy metals in soils Model experiments were carried out under oxidizing conditions with soil samples from surface and subsurface horizons of different composition in order to investigate the solubility and retention of Cu, Zn, Cd, and Pb in soils. The solubility of heavy metals is mainly determined by ad- and desorption processes and complexation reactions of organic and inorganic ligands. Precipitation and dissolution of definite heavy metal compounds do not seem to govern the solution concentration in soils. An exception may probably be the formation of lead phosphate and zinc silicate under specific reaction conditions. The main factors which determine solubility and retention of heavy metals are total amount (except the proportion incorporated in the silicate structure) of the different metals, soil reaction, content of mobilizing and immobilizing organic substances, content of pedogenic oxides and clay minerals, and kind and concentration of salts and inorganic ligands. The results of the model experiments are used together with the results of other authors and general physico-chemical data to give an interpretation of the solubility behaviour of heavy metals in soils. The relations between heavy metal solubility, availability and mobility and possible procedures for melioration of soils contaminated with heavy metals are discussed.     

Heavy metals (copper,lead, nickel,and cadmium) in the organic part of gray forest soils in the Buryat Republic

The levels of the accumulation of copper, lead, nickel, and cadmium in the parent material-soil-plants-soil organic matter system are given for gray forest soils in the Buryat Republic. The concentrations of copper, lead, and nickel in the parent materials do not exceed the corresponding clarkes, and cadmium is present in trace amounts. The concentrations of copper and nickel in the humus horizon are lower than those in the parent material; an opposite situation is observed for lead. The concentrations of copper, lead, and nickel in the soil organic matter and in the herbaceous plants correspond to their contents in the soil and do not exceed the background (clarke) values. Cadmium was not detected in the aboveground part of the plants, though it was found in the root mass and in the organic soil horizon. In the humus of gray forest soils, these heavy metals are mainly present in the acid filtrate remaining after the precipitation of humic acids.     

Leaching of soil‐derived major and trace elements in an arable topsoil after the addition of biochar

The addition of biochar to soils appears to be attractive for sequestering carbon and improving soil fertility. Biochar has been shown to alter carbon, nutrient and element cycling, but there is little information on the cycling of trace elements, which will be introduced increasingly into soils because of their use in modern technologies (e.g. rare earth elements) and significant concentrations in phosphate fertilizers. This study investigated, using column experiments, the effect of biochar addition on the leaching of soil‐derived trace metals from a soil contaminated with heavy metals. The biochar used in this study showed a clear potential to reduce soil‐derived trace metals, including transition metals, rare earth elements and heavy metals such as cadmium (Cd) and lead (Pb), while increasing the amounts of essential nutrients such as potassium (K) and molybdenum (Mo). Uranium was mobilized in the presence of biochar, indicating a risk of increased leaching in biochar‐amended soils. During elution under anoxic conditions manganese (Mn) and iron (Fe) oxides were reduced and a release of metals typically bound to these oxides such as Pb, cobalt (Co), zirconium (Zr) and niobium (Nb) was observed. The retention of dissolved organic matter (DOM) in the amended soil led to a retention of DOM‐associated elements such as copper (Cu), zinc (Zn) and nickel (Ni). Analysis by liquid chromatography followed by ICP‐MS indicated an association with UV‐active DOM. In previous studies conducted with inorganic metal species added to soil, an increased retention of metals has often been interpreted as being caused by cation exchange with the biochar. Our results indicate that the decreased mobility of trace elements is at least partly caused by an enhanced retention of metal‐binding DOM after biochar application.     

外源铜和镍在土壤中的化学形态及其老化研究

采用连续提取法测定了外源铜和镍进入田间土壤后的化学形态分布,比较研究了这2种重金属在3种不同类型土壤(红壤,水稻土和潮土)中随老化时间的形态转化和分布.结果表明,外源铜以残留态(40%～60%)和EDTA可提取态(40%)为主;随老化时间,EDTA可提取态、易还原锰结合态及铁铝氧化态向残留态转化;外源镍在酸性红壤中以可交换态(40%)和残留态(30%～50%)为主,在中性水稻土中以EDTA可提取态(30%)和残留态(30%～50%)为主,在碱性潮土中以铁铝氧化态(20%)和残留态(40%)为主.随老化时间,水溶态、可交换态、EDTA可提取态等向残留态转化.土壤pH较低时水溶态和可交换态含量较高,但是同时随老化时间的降低量也明显;pH较高时有利于易还原锰结合态和有机质结合态的转化.     

Kinetics of speciation of copper,lead, and zinc loaded to soils that differ in cation exchanger composition at low moisture content

Abstract

A better understanding of the fates of heavy metals in wide range of soils is important in improving efficiency of remediation technologies of heavy metals polluted soils. To contribute to this field we studied the kinetics of speciation of copper (Cu), leaf (Pb), and zinc (Zn) in six soils differed in major cation exchanger composition. Soluble salts of Cu, Pb, and Zn were loaded to the soils, incubated at field moisture contents, and the change in chemical forms of the metals was traced by sequential extraction. In Inceptisols predominated by 2:1 layer silicates and poorly crystalline iron oxides, the added Cu and Pb were found mostly in exchangeable and oxide bound fractions, with decreasing and increasing proportion of the former and the latter during 50 days after addition, respectively. In allophanic and humic Andisols, about 50 to 70% of the total Cu and Pb was found in oxide bound fraction with a significant amount in organically complexed fraction in the latter. The amounts of Cu and Pb in each fraction varied only slightly with time in these soils. The proportion of oxide bound Cu arid Pb was relatively low in a kaolinitic Ultisol irrespective of its higher iron oxide content. Zinc was found mostly in exchangeable and soluble fractions except in Andisols. Low crystallinity of oxide minerals as well as their amount is important factors determining heavy metal retaining capacity of soils. The exchangeable and oxide bound heavy metals should be treated separately in models simulating removal of heavy metal cations by washing and electrokinetic methods.     

Heavy Metal Pollution by Atmospheric Transport in Natural Soils from the Northern Part of Eastern Carpathians

The present paper is a study of the heavy metal contamination ofnatural soils due to atmospheric transport in the northern partof Eastern Carpathians. The study area is located north of BaiaMare, the main Romanian centre for processing complex sulphideores. Ten undisturbed soil profiles of andosols and andic soilswere investigated. The distribution of heavy metals (Pb, Cu, Zn,Mn, Ni, Co, Cr and Cd) was studied along the soil profile and atspecific distances from the pollution sources. In addition tothe total nitric acid soluble fraction of the metals, amounts oflead, copper, zinc and manganese extractable with 0.05 Mhydrochloric acid were determined to evaluate the fraction ofeach metal potentially available to plants. Surface soils in theIgnis Mountains (10 km from Baia Mare) were more polluted withlead (200–800 ppm), with the concentration decreasing withdistance from the processing plants. Lower lead concentrationswere observed in the deeper soil horizons. The fraction of leadextractable in 0.05 M hydrochloric acid was generally higher athigh total concentrations of lead. From its geographical andsoil profile distributions it is also evident that cadmium wasalso supplied in appreciable amounts to the topsoil from thesame polution sources, whereas the trend was weaker for zincand chromium and not evident for copper, manganese, nickel, orcobalt. The fraction extractable with 0.05 M hydrochloric acidgenerally followed the order Pb > Cu > Zn > Mn.     

Short- and long-term effects of heavy metals on urease activity in soils

Summary The inhibitory effects of cadmium, chromium, copper, lead, nickel and zinc on urease activity of five different soils during two different periods were investigated, in order to obtain information on the change in heavy metal toxicity with time. The results are presented graphically as logistic dose-response curves. When the ecological dose range was used as a measure of toxicity this value decreased significantly only for copper in the sandy soil. Considering toxicity as the ecological dose-50% (ED50) value, toxicity tended to increase over 1 1/2 years for cadmium, copper and zinc. For nickel and lead, however, the toxicity stabilized in all soils, except in sand and clay. The average ED 50 value of zinc varied between 100 and 300 mg kg^–1 and its toxicity was highest. It is emphasized that these data may help to set limits for the heavy-metal pollution of soils.     

Characteristics of soil profiles affected by smelting of nickel and copper at Coniston,Ontario, Canada

Soil profiles were examined, described and sampled by horizons in various geomorphic positions along a transect originating at the Coniston smelter and extending in a southeasterly direction for approximately 12 km. The samples were then analyzed to determine particle-size distribution, pH, organic carbon and five heavy metals.Within the study area, elevated levels of nickel, copper and iron were found with maximum total concentrations of 1.2, 0.97 and 20.0%, respectively. Manganese and zinc did not occur in above-normal concentrations. The pH values of the soils were depressed with levels as low as 2.4.Near the smelter, erosion from soils on slopes has transferred materials into lower lying areas, thereby rearranging the areal distribution of nickel, copper and iron. Although the surface soil horizons along the entire transect have above-normal concentrations of these elements, only within the eroded area is there marked variability in their vertical distribution.     

Schwermetalle in Oberböden des Warthetals unter städtischem Einfluß

Heavy metals in surface soils of the Warta river valley in an urban area In the urban area of the city of Poznan the contamination with heavy metals was investigated. From the top soil layers of five cross-sections of the valley of the Warta river 87 samples were collected. Beside common soil characteristics the contents of arsenic, barium, cadmium, chromium, copper, iron, lead, manganese, phosphorus and zinc were analyzed. Predominantly the level of contamination with heavy metals is low in the valley soils. A higher level was found in the area of the old city centre. Especially the contents of lead, copper and zinc were raised. Downstream of the sewage plant discharge into the river Warta increased contents of lead and cadmium were found. The distribution of heavy metals in the river Warta sediments indicates that the reason of the local increase of heavy metal contents is the sewage water discharge, Correlations between the content of different heavy metals and other soil properties (pH, clay and P-content, C/N-ratio) were calculated.     

Fractionation of residual cadmium,copper, nickel,lead, and zinc in previously sludge‐amended soil

Abstract

The fractionation of heavy metals in previously sludge‐amended soil is important to evaluate their behavior in the environment in terms of mobility and availability to crop plants. A surface soil that received two types of sludges at two different rates, plus fertilizer only and no treatment (control), having been fallow for nine years, was used in this study. The contents of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) fractions in previously sludge‐amended soils were governed by the total content of these metals in the sludges applied and by the rate of sludge application. The contents of these metals were higher for soils that received the Chicago sludge as compared to that receiving the Huntsville sludge. Furthermore, soils that received 20 Mg/ha/yr of sludge for five years generally had higher levels of these metals than those receiving a single dose at the 100 Mg/ha application rate. The percentage of the total content in the water soluble and exchangeable forms was very low (≤1%) regardless of sludge application. The application of sludges tended to reduce the residual fraction and to increase the organic and carbonate fractions. Overall, the predominant forms of the metals in the sludges were as the Cd‐, Ni‐, Pb‐, and Zn‐carbonate and Cu‐organic fractions.     

重金属复合污染下红壤微生物活性及其群落结构的变化

在室内培养条件下,应用4因素5水平二次正交回归旋转组合设计方案,对重金属复合污染红壤的微生物活性及群落功能多样性进行了研究。结果表明,在Cu、Zn、Pb、Cd复合污染生境中重金属的微生物毒性效应发挥主要由Cd、Cu两元素决定,其生物毒性顺序表现为:Cd>Cu>Zn>Ph,红砂泥中表现较为突出。与单一镉、单一铅污染处理相比,重金属复合污染对供试红壤微生物生物活性及其群落功能多样性的影响并非仅仅表现出简单的加和作用,同时还存在协同作用和拮抗作用。典型相关分析显示,红壤微生物活性与重金属含量之间关系密切,第一对典型变量的相关系数r达0.885 8、0.932 8,均达极显著水平(p<0.001), 说明重金属复合污染与红壤微生物间存在较为稳定的数量反馈机制,红壤总体微生物活性指标能较好地反映供试红壤重金属复合污染状况,可作为重金属污染红壤环境质量评价及量化分类的有效指标。     

Efficiency of remediation of technogenic barrens around the Pechenganikel works in the Kola Subarctic

Remediation of the technogenic barrens around the Pechenganikel works on the Kola Peninsula resulted in the improvement of the soil properties, namely, in a decrease in acidity and enrichment with nutrients, which continued for several years. However, the reaction of most of the treated soils remained strongly acid, and the concentrations of available calcium, magnesium, potassium, and phosphorus were much lower than their background levels and the demands of the plants for nutrients (especially, for magnesium and potassium). The soils were depleted in available manganese and zinc. Most of the treated soils contained the same (or higher) amounts of available nickel and copper compounds in comparison with their untreated analogues. The willow plantations on the remediated plots were in a satisfactory state, but they experienced a deficit of magnesium, manganese, and zinc; they consumed elevated amounts of nickel and copper. Recommendations on the nutrient regime of the soils aimed at decreasing the mobility and biological availability of heavy metals were made.     

Zum Einfluß von pH und organischem Kohlenstoffgehalt auf die Löslichkeit von Eisen,Blei, Mangan und Zink in Waldböden

Influence of pH and organic carbon content on the solubility of iron, lead, manganese and zinc in forest soils Several soil factors determine the solubility of heavy metals in soils. The contents of exchangeable and in consequence potentially plant available heavy metals are mainly influenced by the pH and the content of organic carbon. Samples of the A_h-horizon from the stemflow area and from soil not influenced by stemflow water were investigated in beech forests. The solubility or iron, lead, manganese and zinc is described in relation to the pH and the content of organic carbon. Exchangeable iron and lead appear in significant amounts at pH below 3.5 and 4.5, respectively, regardless to the content of organic carbon. Manganese and zinc are exchangeable at pH below 5.0 and are leached for about 90% from the A_h-horizon at pH values below 3.0. The effects of higher soluble iron and lead contents on the distribution of herbaceous plants are discussed.