VA菌根对土壤酸度的耐性

The ammonification,nitrifcation and denitrification in maize rhizosphere of alluvial sols were compared with those in the bulk soil after exposure to different kinds of heavy metals.The addition of cadmium at low levels (2 mg kg^-1 and 5 mg kg^-1）could stimulate the ammonification and nitrification in the soils,while inhibition influences were found at high levels of Cd addition (10 mg kg^-1 and 20mg kg^-1），The relationship between microbial activity and cadmium concentration varied with the kind of microorganisms.The nitrifying bacteria were more sensitive to cadmium pollution than the ammonifying bacteria.When Cd( Ⅱ），Cu（Ⅱ）and Cr（Ⅵ）wer compared at the same addition concentration of 20 mg kg^-1 soil,Cd(Ⅱ） was the most effective inhibitor of ammonification and denitrification. among the three investigated heavy metals,and Cr（Ⅵ）had the most strong inhibitory influence on the nitrifying bacteria.The microbial activities in rhizosphere were higher than those in the bulk soil for most of the treatments.Cr(Ⅵ)proved to be the most effective in enhacing the microbial activities in rhizosphere,and this could be caused by the poitive reduction of Cr(Ⅵ）to Cr(Ⅲ）in rhizosphere,and the relatively sufficient existence of organic matter which intensified the adsorption of the metal,It seemed that the rhizosphere had some mitigation effect on heavy metal toxicity.     

施用碱稳定固体的酸性土壤的Cu和Zn的形态分布

Fractionation of metals in a granite-derived acid sandy loam soil amended with alkaline-stabilised sewagesIudge biosolids was conducted in order to assess metal bioavailability and environmental mobility soil solution was extracted by a centrifugation and filtration technique. Metal speciation in the soil solution wasdetermined by a cation exchange resin method. Acetic acid and EDTA extracting solutions were used forextraction of metals in soil solid surfaces. Metal distribution in different fractions of soil solid phase was determined using a three-step sequential extraction scheme. The results show that the metals in the soilsolution existed in different fractions with variable lability and metals in the soil solid phase were also presentin various chemical forms with potentially different bioavail ability and environmental mobility Alkaline-stabilised biosolids could elevate solubility of Cu and proportion of Cu in organically complexed fractionsboth in soil liquid and solid phases, and may therefore increase Cu mobility. In contrast, the biosolids lowered the concentrations of water-soluble Zn (labile fraction) and exchangeable Zn and may hence decrease bioavailability and mobility of Zn. However, Fe and Mn oxides bound and organic matter bound fractions are likely to be Zn pools in the sludge-amended soil. These consequences possibly result from the liming effect and metal speciation of the sludge product and the difference in the chemistry between the metals in soil.     

受土壤类型和金属负荷量影响的重金属形态分布

Two series of soil subsamples, by spiking copper(Cu),lead(Pb),zinc(Zn)and cadmium(Cd)in an orthogonal design,were prepared using red soil and brown soil,respectively.The results indicated that heavy metal fractions in these soil subsamples depended not only on soil types,but also on metal loading quantity as well as on interactions among metals in soil.Lead and Cu in red soil appeared mostly in weakly specifically adsorbed(WSA),Fe and Mn oxides bound(OX),and residual(RES)fractions.Zine cxisted in all fractions except organic bound one,and Cd was major in water soluble plus exchangeable(SE)one.Different from the results of red soil,Pb and Cu was present in brown soil in all fractions except organic one,but over 75% of Zn and 90% of Cd existed only in SE fraction.Meanwhile,SE fraction for any metal in red soil was lower than that in brown soil and WSA and OX fractions were higher.It is in agreernent with low cation exchange capacity and large amounts of metal oxides included in red soil.Metal fractions in soil,especially for water soluble plus exchangeable one ,were obviously influenced by other coexisting metals.The SE fraction of heavy metals increased with increasing loading amounts of metals in red soil but not obviously in brown soil,which suggest that metal availability be easily affected by their total amounts spiked in red soil.In addition,more metals in red soil were extracted with 0.20 mol L^-1 NH4Cl（pH5.40）than that with 1.0 mol L^-1 Mg(NO3)2(pH7.0),but the reverse happened in brown soil,implicating significantly different mechanisms of metal desorption from red soil and brown soil.     

广东大宝山矿区土壤重金属污染

Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels （P ≤ 0.05） of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg^-1, respectively. These metals were continuously dispersed downstream from the tallings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg^-1, respectively, being significantly higher （P ≤ 0.05） as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.     

表面活性剂LAS对土壤Cd形态及Cd在黄豆植株中分配的影响

A pot experiment was conducted to study the effect of an anionic surfactant linear alkylbenzene sulfonate （LAS） application on cadmium （Cd） fractions in soils and Cd distribution in different tissues of soybean （Glycine max） plants as well as soil pH. Soil samples were treated with three levels of Cd （0, 5, and 10 mg kg^-1） and five levels of LAS （0, 5, 15, 50, and 100 mg L^-1）. Results indicated that compared to the control soils （no Cd and no LAS treatment）, soil pH increased and available Cd decreased in the soil treated with external Cd and watered with LAS solutions. Meanwhile, soil exchangeable Cd and Cd bound to carbonates decreased; Cd bound to amorphous iron and manganese oxides and Cd bound to organic matter increased. In addition, LAS application could reduce enrichment of Cd in soybean plants, resulting in decreased Cd in the soybean plants. Thus, suitable LAS application could decrease bioavailability and mobility of soil Cd.     

长期用生活污水处理厂排放的废水浇灌影响了糙米和土壤中重金属的含量

A pot experiment was conducted in a plastic film house to evaluate the translocation and uptake of heavy metals(Pb,Cd,Cu,and Zn) into brown rice(Oryza sativa L.) and the heavy metals residues in soils which had previously been irrigated with domestic wastewater for a long time(3 years).The range of Pb,Cd,Cu,and Zn was 5.10 ± 0.01,0.105 ± 0.017,5.76 ± 0.42,and 23.56 ± 1.40 mg kg-1,respectively in the domestic wastewater-irrigated soil,and 0.370 ± 0.006,0.011 ± 0.001,0.340 ± 0.04,and 2.05 ± 0.18 mg kg-1,respectively,in the domestic wastewater-irrigated brown rice.The results indicated that application of domestic wastewater to arable land slightly increased the levels of Pb,Cd,Cu,and Zn in soil and brown rice(P < 0.01).The concentrations of heavy metals in brown rice were lower than the recommended tolerable levels proposed by the Joint FAO/WHO Expert Committee on Food Additives.However,the continuous monitoring and pollution control of hazardous materials from domestic wastewater are needed in order to prevent excessive build-up of heavy metals in the food chain.     

不同Zn浓度对黑麦草根分泌物、根际Zn形态及植物Zn蓄集的影响

A glasshouse experiment was conducted using a root-bag technique to study the root exudates, rhizosphere Zn fractions, and Zn concentrations and accumulations of two ryegrass cultivars (Lolium perenne L. cvs. Airs and Tede) at different soil Zn levels (0, 2, 4, 8, and 16 mmol kg-1 soil). Results indicated that plant growth of the two cultivars was not adversely affected at soil Zn level≤8 mmol kg-1. Plants accumulated more Zn as soil Zn levels increased, and Zn concentrations of shoots were about 540 /μg g-1 in Aris and 583.9μg g-1 in Tede in response to 16 mmol Zn kg-1 soil. Zn ratios of shoots to roots across the soil Zn levels were higher in Tede than in Airs, corresponding with higher rhizosphere available Zn fractions (exchangeable, bound to manganese oxides, and bound to organic matter) in Airs than in Tede. Low-molecular-weight (LMW) organic acids (oxalic, tartaric, malic, and succinic acids) and amino acids (proline, threonine, glutamic acid, and aspartic acid, etc.) were detected in root exudates, and the concentrations of LMW organic acids and amino acids increased with addition of 4 mmol Zn kg-1 soil compared with zero Zn addition. Higher rhizosphere concentrations of oxalic acid, glutamic acid, alanine, phenylalanine, leucine, and proline in Tede than in Airs likely resulted in increased Zn uptake from the soil by Tede than by Airs. The results suggested that genotypic differences in Zn accumulations were mainly because of different root exudates and rhizosphere Zn fractions.     

华北矿区残留态铜、铅在土壤剖面中的分布与迁移

Residual heavy metals are commonly considered to be immobile in soils, leading to an underestimation of their environmental risk. This study investigated the distribution and transport of residual heavy metals along soil profiles, using the Xiaoqinling gold mining region in North China as a case study. Soil samples were collected at three depths from three locations near the tailing heap. The speciation of copper (Cu) and lead (Pb) (exchangeable, carbonate-bound, Fe-Mn oxide-bound, organic matter-bound, and residual fractions) was determined using a sequential extraction procedure. The residual fraction’s morphology was observed using scanning electron microscopy (SEM). Results showed that metal fraction distributions along the soil profiles were influenced by each fraction’s mobility. Residual fraction with high chemical stability cannot be transformed from or into other fractions. This led to the conclusion that the high concentration of residual metals in soils mainly resulted from residual fraction transport.The SEM analysis showed that fine particles (submicrons) were mainly attached to large particles and were likely released and transported by water flow. The more sorptive fractions (non-residual fractions) were mainly retained in the top soil, and the more mobile fractions (residual fraction) were mainly leached to the deep soil. Cu and Pb concentrations in the residual fraction decreased slightly and those in the non-residual fractions decreased significantly with soil depth. These suggest a relatively higher residual metal mobility along the soil pro?les. Therefore, residual metals can be transported in soils and their environmental risk can not be ignored in assessing soil contamination.     

Effect of Water Quality on Heavy Metal Redistribution and Mobility in Polluted Agricultural Soils in a Semi-Arid Region

Mornag Plain is a coastal area of the Mediterranean basin, which has undergone an agricultural industrial boom. The aim of this study was to investigate the different water qualities used for irrigation on heavy metal mobility in these polluted agricultural soils. The geo-accumulation indices for heavy metals (Ni, Cr, Pb, Cd, Cu, and Zn) revealed that industrial activities and used treated wastewater (TWW) contributed to soil pollution, and water irrigation always decreased this contamination. After long-term use of different water types, high perturbation of heavy metal redistribution has occurred. Groundwater use altered all heavy metal redistributions in the irrigated soil among various soil-solid and soil-solution fractions, as compared to the unirrigated soil. Slight acid water use transferred some metals from different solid phase components into water-soluble and exchangeable fractions. However, TWW use transformed some Ni, Cr, Cd, Cu, and Zn from water-soluble and exchangeable fractions to less labile fractions, particularly into organically bound fractions. Reuse of conventional water within the same soil decreased the whole soil redistribution index values, indicating tendency to return to the pattern of distribution of groundwater-irrigated soil.     

Chemical extractability and availability of heavy metals after seven years application of organic wastes to a citrus soil

Abstract. The chemical extractability of heavy metals introduced into the soil during 7 years application of sewage sludge, composted municipal solid waste and sheep manure, and their availability to citrus plants were studied. The total content of metals in the soil (0-20 cm)was increased by the use of sludges and compost, but only the Ni content in the saturation extracts of soil was significantly increased. Total Cd, Cr, Cu, Ni, Pb, and Zn were sequentially fractionated into water-soluble plus exchangeable, organically bound, carbonate-associated, and residual fractions. Most of the heavy metals were present in carbonate and residual fractions, although substantial amounts of water-soluble plus exchangeable Cd, and organically bound Cu and Ni were found. No significant increases in the metal contents in leaves and orange fruits were observed, with the exception of Pb in leaves. Several statistically significant correlations between metal content in plants, metal content in soil fractions, and chemical characteristics of soil were also found.     

Feasibility of a counter-current extraction procedure for the removal of heavy metals from contaminated soils

Effective remediation and sanitation technologies for soils contaminated with heavy metals are limited. We investigated the feasibility of a counter-current metal extraction procedure for the removal of selected heavy metals (Cd, Cu, Ph, and Zn) from two contaminated soils. The process involved a decarbonation (removal of carbonates), acid solubilisation, washing, and liming step. Results from batch equilibration experiments simulating the counter-current process showed more than 85% of the Cd present to be removed. Removal efficiencies for Cu and Pb were limited to approximately 15%, this mainly due to resorption of these elements during the decarbonation step. As most Zn was found to be present in a more difficult acid-extractable solid phase, its extractability accounted for only 25%. While reaction (pH) conditions of both decarbonation and solubilisation determined removal efficiencies, washing the extracted soil with deionized water only slightly increased the amount of metals removed. Metal distribution among solid phases — exchangeable, carbonate, reducible, organically bound, and residual — was affected by the different treatments. The amount of metals contained in the exchangeable and residual fractions determined their extractability. Except for Cu, the reducible and organically bound fractions were less important. After solubilisation 13 to 70% of the metals were present in an exchangeable solid phase. This implicates that washing the solubilized soil with a salt may increase the extractability of metals, especially for Zn and Pb. Based on our results the process is critically evaluated and possibilities for optimization formulated.     

水稻子实对不同形态重金属的累积差异及其影响因素分析

在分析成都平原核心区土壤重金属(Cd、Cr、Pb、Cu、Zn)全量、各形态含量及相应点位种植的水稻子实重金属含量的基础上,通过统计分析、空间插值及线性回归方程的模拟,研究了土壤Cd、Cr、Pb、Cu、Zn全量的空间分布状况、各形态重金属含量统计特征,以及水稻子实对重金属各形态的累积差异及其影响因素。结果表明,成都平原水稻土重金属污染较轻,除Cd外,均低于国家土壤环境质量二级标准。土壤中重金属的可交换态含量均较低,Cd主要以铁锰氧化态存在,Cr、Cu、Zn、Pb主要以残渣态存在。水稻子实对5种重金属的累积效应顺序为:Cd>Zn>Cu>Pb>Cr。与水稻重金属累积关系密切的重金属活性形态(可交换态、碳酸盐结合态、铁锰氧化物结合态和有机物结合态)主要有:Cd的碳酸盐结合态、Cr的可交换态、Pb的有机物结合态和Cu的碳酸盐结合态含量;Zn各活性形态对水稻子实含量的影响不明显。土壤理化性质对不同活性形态重金属元素的影响效应各不相同。活性态Cd主要受有机质、pH和容重的影响;活性态Cr与pH、有机质、CEC和容重密切相关;活性态Pb与有机质、容重、中细粉粒、砂粒等均有密切的关系;Cu的活性主要受粘粒、有机质含量的影响;Zn的有效性主要受pH、有机质、砂粒、容重的影响。总的看来,对土壤Cd、Cr、Pb、Cu、Zn各活性形态含量影响效应较强的是有机质、pH、容重,而与土壤吸附性能密切相关的颗粒组成、CEC的影响不甚明显。     

污染水稻土中重金属的形态分布及其影响因素

通过BCR3步提取法研究了江西省贵溪铜冶炼厂污染区水稻土中重金属的形态分布。研究表明,废渣场渗滤液污染区域(渣场区)的污染较污水灌溉污染区(污灌区)严重,渣场区土壤中Cu、Pb、Cd的含量高于污灌区,而污灌区土壤Ni含量较高。在表层(0～20cm)水稻土中,Cu以可氧化态为主,Pb以可还原态和可氧化态为主,Cd以酸溶态为主,Ni以残渣态为主,不同重金属元素的有效态所占总量百分比大小顺序是Cd>Cu>Pb>Ni。土壤重金属不同形态之间也呈现一定的相关性,说明Cu与Pb、Cd、Ni之间具有同源性。土壤pH主要影响了污灌区中Cu的形态分布,以及渣场区土壤酸溶态Ni的分布。土壤有机质含量对各重金属形态分布的影响不明显。     

Chemical Speciation of Heavy Metals in the Fractionated Rhizosphere Soils of Sunflower Cultivated in a Humic Andosol

Chemical speciation and bioaccumulation factor of iron (Fe), manganese (Mn), and zinc (Zn) were investigated in the fractionated rhizosphere soils and tissues of sunflower plants grown in a humic Andosol. The experiment was conducted for a period of 35 days in the greenhouse, and at harvest the soil system was differentiated into bulk, rhizosphere, and rhizoplane soils based on the collection of root-attaching soil aggregates. The chemical speciations of heavy metals in the soil samples were determined after extraction sequentially into fractions classified as exchangeable, carbonate bound, metal–organic complex bound, easily reducible metal oxide bound, hydrogen peroxide (H₂O₂)–extractable organically bound, amorphous mineral colloid bound, and crystalline Fe oxide bound. Iron and Zn were predominantly crystalline Fe oxide bound in the initial bulk soils whereas Mn was mainly organically bound. Heavy metals in the exchangeable form accumulated in the rhizosphere and rhizoplane soils, comprising <4% of the total content, suggesting their relatively low availability in humic Andosol. Concentrations of organically bound Fe and Mn in soils decreased with the proximity to roots, suggesting that organic fraction is the main source for plant uptake. Concentrations of Mn and Zn in the metal–organic complex also decreased, indicating a greater ability of sunflower to access Mn from more soil pools. Sunflower showed bioaccumulation factors for Zn, Fe, and Mn as large as 0.39, 0.05, and 0.04 respectively, defining the plant as a metal excluder species. This result suggests that access to multiple metal pools in soil is not necessarily a major factor that governs metal accumulation in the plant.     

长三角和珠三角农业土壤中铅、铜、镉的化学形态与转化

研究了重金属Pb、Cu、Cd在长江三角洲和珠江三角洲土壤中的转化及不同Pb、Cu、Cd负荷水平对土壤重金属形态的影响。结果表明:未明显污染土壤中重金属主要以残余态为主,可提取态组分的比例Cd>Cu>Pb,但不同土壤之间有较大变化;随着土壤重金属负荷的提高,土壤中交换态重金属的比例增大,残余态比例下降,有效性提高,对环境威胁增大;当重金属加入量较低时,重金属优先向氧化物结合态、有机质结合态转化,而当加入量较高时,向交换态和碳酸盐结合态转化的比例明显增加;pH和土壤组分对重金属在土壤中的转化有显著影响,土壤pH下降可使交换态Cd、Cu、Pb的比例递增。     

DISTRIBUTION AND SEQUENTIAL EXTRACTION OF SOME HEAVY METALS FROM SOILS IRRIGATED WITH WASTEWATER FROM MEXICO CITY

A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg^-1 Cd, 0.86 to 5.07 mg kg^-1 Pb, 18.1 to 131.7 mg kg^-1 and Zn, 101 to 235.5 mg kg^-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO₃ contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils.     

Immobilization and species of heavy metals in soils in the absence and presence of rhizobia

Abstract

The effect of bacterial inoculation of Rhizobium fredii HN01 on the immobilization and speciation of Cu, Zn, and Cd was studied in Red and Cinnamon soil which are typical Chinese soils. The soil was mixed with bacterial suspension for one week followed by an immobilization of each heavy metal for another week. The total binding and fractionation of heavy metals in soils were analyzed. As compared with the control, the retention of total Cu, Zn, and Cd in Red soil increased by 28, 16, and 28%, respectively, in the presence of rhizobia. The amount of exchangeable, NH₄OAc-extractable, Mn oxides-bound and organic matter-bound Cu increased by 23–123%. There were significant decrease of exchangeable Cu and marked increases of NH₄OAc-extractable and Mn oxide-bound Cu in Cinnamon soil with the presence of rhizobial cells, although no changes for the total retention of Cu were observed. The amount of exchangeable Zn in Red soil-rhizobia composite was 20% greater than that of the no-rhizobia soil. Addition of rhizobia also increased exchangeable Cd and specifically-adsorbed Cd by 25 and 93%, respectively, in Red soil. No considerable differences were found for the total immobilization of Zn and Cd as well as their distribution in various solid fractions of Cinnamon soil in the absence and presence of rhizobial cells. In terms of soil components, it is assumed that bacterial biomass had a relatively less impact on the species of heavy metals bound with Fe oxides. Results suggested that the retention and speciation of heavy metals in soil are governed largely by the interactions of bacteria with various inorganic and organic soil constituents. The data are useful in understanding the impact of microorganisms on the behavior, mobility and transformation of heavy metals in soil environments.     

新疆奎屯垦区土壤重金属风险评价

采用网格法采样,对新疆奎屯垦区3个团场土壤中As、Pb、Cu、Cd、Cr和Ni含量进行了测定,系统分析了该地区土壤重金属的含量水平、潜在生态风险程度、主要污染因子和污染来源。结果表明:奎屯垦区土壤重金属As、Pb、Cd、Cu、Cr、Ni的平均值分别为20.21 mg kg-1、35.91 mg kg-1、0.40 mg kg-1、27.18 mg kg-1、77.02 mg kg-1、39.31 mg kg-1,均没有超过国家土壤环境质量二级标准,但As、Cd有个别样点超标。各元素平均含量值均超过新疆土壤背景值,其中Cd、As、Pb最为显著,呈现出累积趋势。各重金属潜在生态风险由高至低顺序为Cd>As>Pb>Ni>Cu>Cr,其中Cd为主要潜在生态风险因子。进一步相关分析和因子分析结果显示,各元素的来源可分为两类,Cd、Pb和As为一类,来源主要受各种人为活动影响,Cu、Cr、Ni为一类,来源主要与成土母质有关。