苏南某冶炼厂周边农田土壤重金属分布及风险评价

选择江苏南部冶炼厂周边污染的水稻田,采集耕层0～15cm的土壤,分析土壤中重金属Cd、Pb、Hg、As、Zn、Cu的污染程度及其空间变异特征。结果表明,土壤Cd、Pb、Cu、Zn、Hg的全量随着距污染源距离的增加而减少,呈现由东北向西南扩散的趋势,As则是由西北向东南扩散。6种重金属中Cd、Hg的污染范围相对较大,Zn的污染范围最小。DTPA浸提的6种重金属有效态含量都是距污染源距离越远而越少。采用内梅罗综合污染指数法对土壤中的重金属进行风险评价,土壤重金属的综合污染指数为39.27,污染程度已超过5级,为重度污染,其中Cd、Hg污染最为严重,含量范围分别为3.98～44.58mg·kg-1、0.36～2.01mg·kg-1,As为中度污染,Pb、Cu、Zn则为轻度污染,说明研究区域农产品安全生产存在很大的风险。     

Investigation of heavy metal concentrations on urban soils,dust and vegetables nearby a former smelter site in Mortagne du Nord,Northern France

Environmental situations near former industrial sites like Mortagne du Nord (Northern France) in which the soil, dust and homegrown vegetables have been contaminated by heavy metals can represent a sanitary risk to the surrounding population. In order to evaluate the contamination level in different exposition media in this site, 26 urban topsoils, 17 dust and 38 vegetable samples were taken near the former zinc smelter site. All the observed levels on urban soil samples (except one) are over regional agricultural reference values for Cd and Pb. 45 % of the vegetable samples are over the European foodstuff limits and one dust sample taken in the school playground outdoor tarmac area exceeds the French limit in dust set up at 1,000 μg m^?2 for Pb. The Cd and Pb levels fluctuate depending on the use of the ground (kitchen garden, lawn, courtyard) and its location. The lack of simple correlations between the distance from the former smelter site and the Pb concentrations on sampled soils let us think that human activities contributed in the local urban contamination. In this context, who is now responsible for the soil contamination and the human exposure?     

Selenium Content and Uptake in Crops as Affected by Soil Selenium Content and Implications on Human Health

The selenium contents of soil and its uptake by a wide variety of crops are analyzed along a transect, with the sampling stations located at Mawkyrwat, Upper Shillong, Pynthormukrah, and Nongpoh. Each site is successively farther away from uranium deposits, with the closest being Mawkyrwat (50 km). Leafy vegetables had greater selenium content than tubers and fruits. The concentrations of selenium in soil ranged from 70 μg g^?1 to 296 μg g^?1 and in vegetables varied from 26 μg g^?1 to 225 μg g^?1. Selenium is known to be a decay product of uranium, and the results indicate that the selenium content of soil and vegetables of Mawkrywat is greater than the other three sampling sites. This can be attributed to the proximity of this site to uranium deposits of Domiasat. The possible implications of selenium on human health are discussed.     

Multiple Metal Resistant Transferable Phenotypes in Bacteria as Indicators of Soil Contamination with Heavy Metals (6 pp)

Background, Aim and Scope   Environmental contamination by heavy metals affects microbial communities. The number of single and multiple heavy metal resistant bacteria may be an indictor of the level of contamination. This paper details the isolation and characterisation of metal resistant microorganisms isolated from rhizosphere/soil samples obtained from an abandoned zinc, lead and copper mine and a local unaffected site. This data was compared to the level of heavy metal in the soils to establish the effect of metals on the microbial community and to determine the relationship between pollutant levels and resistant strains. This paper outlines the diversity of transferable resistance determinants between both sites and details the levels of heavy metal resistant bacteria and those expressing transferable multiple heavy metal tolerance.Methods   The sample sites were located in Co. Galway, Ireland. The first sample site (site A) was a former lead, zinc and copper mine, which was closed in 1961 due to exhaustion of ore. The second site (site B) was located two and a half kilometres from the mining site and was not affected by the mining operations. Composite soil samples were characterised for general soil matrix composition, organic content, pH and general chemical parameters. The soil was also enumerated for the total viable heterotrophic counts and tested on Pseudomonas selective agar (PSA) for total Pseudomonas counts and Sucrose Asparagine (SA), which is semi-selective for fluorescent Pseudomonas.Results and Discussion   Samples from both site A and site B were analysed by atomic absorption spectrophotometry for the presence of heavy metals. In the case of copper, which has a Dutch list recommended minimum permissible level of 190 µg/Kg dry weight, the levels detected at site A were 1270 µg/Kg dry weight while site B was detected at 36 µg/Kg. The arsenic levels detected at site A were eight times the permissible level (416 µg/Kg) while only half the permissible level was found at site B (13 µg/Kg). Zinc concentrations were also high at site A (4460 µg/Kg) while at site B (553 µg/Kg) they were well below the Dutchlist guidelines (720 µg/Kg). A large number of heavy metal tolerant strains were isolated from both sites. 270 isolates (site A (170) and site B (100)) were screened against 8 metals to examine the extent of multiple resistance. 82% of the strains from site A were found to be resistant to 5 metals. A total of 18% showed resistance to all 8 metals and of those examined only 4% were resistant to only one metal. In contrast isolates from site B showed no multiple resistance to more than 5 metals, while 62% showed resistance to individual metals only. Site A had a higher level of multiple heavy metal resistance strains. Stains isolated from site A had 23 (14%) isolates resistant to zinc, copper, nickel, arsenic and cobalt and site B had no bacteria resistant to all five of these selected metals. The transferability of heavy metal resistance was investigated in the case of 60 multiple heavy metal resistant isolates taken from site A and 50 multiple resistance isolates from site B. Transfer was only detected in isolates from site A, 13% showed transfer and expression of copper, zinc and arsenic resistance determinants. In most cases the transconjugants only expressed resistance to copper, zinc and arsenic, which were the metals, used for selection. This co-transfer of all three determinants suggests a genetic link between these resistance determinants.Conclusion   Heavy metal resistant bacteria are present in both sites, however, the number and presence of multiple transferable resistance phenotypes are confined to the isolates from the heavy metal contaminated site. The presence of high levels of heavy metals selects these multiple resistance phenotypes. Within these communities there seems to be little diversity between the microorganisms, which provides a hugely preferable environment for gene transfer of such metal resistant determinants.Recommendation and Perspective   The experiments have shown a microbes ability to mobilize heavy metal determinants and a relationship between heavy metal resistance and metal contamination has been identified These multiple heavy metal resistant bacteria could eventually be used for detection and qualification of the level of heavy metal-polluted soil/water environments.     

珠三角滩涂围垦农田土壤和农作物重金属污染

为了研究珠三角滩涂围垦农田土壤和农作物重金属污染状况,采集了广州南沙、中山一带围垦农田农作物及其根际土壤样品,测定重金属的质量分数。结果表明,围垦农田土壤样品中Cu、Ph、Cd、Ni、Cr和Zn含量均大于广东省相应土壤环境背景值,其中Cu（56．06mg·kg^-1）、Pb（48．30mg·kg^-1）、Cd（0．72mg·kg^-1）、Ni（41．15mg·kg^-1）、Cr（115．1mg·kg^-1）和Zn（200．1mg·kg^-1）分别为背景值的3．30、1．34、12．82、2．26、2．28和4．23倍。与《土壤环境质量标准》（GB15618-1995）中Ⅱ级标准（pH〈6．5）比较,土壤样品中Cu、Cd、Ni和Zn的超标率分别为73．7％、88．6％、59．6％和28．9％。以GB15618-1995中Ⅱ级标准为评价标准,采用Nemerow指数法进行评价,土壤重金属平均综合污染指数为1．86,属3级轻污染。与《食品中污染物限量》（GB2762-2005）等相关标准比较,农作物中Cu、Pb、Cd、Ni、Cr和Zn含量的样品超标率分别为0、28．9％、2．6％、48．3％、12．3％和6．1％。由此可见,珠三角滩涂围垦农田土壤和农作物重金属污染问题已经比较突出,土壤污染以Cd为主,而农作物污染则以Ni、Ph、Cr为主。     

Heavy Metals Affect Yield,Essential Oil Compound,and Rhizosphere Microflora of Vetiver (Vetiveria zizanioides Linn. nash) Grass

The effects of heavy metals [chromoium (Cr), cadmium (Cd), lead (Pb) and nickel (Ni)] on the yield, khusimol content in the essential oil, accumulation of metals, and rhizosphere microflora of vetiver (Vetiveria zizanoides) were studied in a pot experiment. The shoot yield and khusimol content in oil of vetiver were enhanced by the application of moderate amount of metals to soils. The application of Cr, Pb, and Ni had deleterious effects on the root and essential oil yield. The application of high levels of metals to soil had harmful effects on the bacterial and fungal counts in the rhizosphere. The concentrations of metals such as Cr, Cd, Pb, and Ni in shoot and root tissues were significantly enhanced by the application of those metals to soils. It can be concluded that the vetiver could be used as a promising crop for revegetation, soil remediation, and production of better quality essential oil in metal-contaminated soils.     

广东省部分基地蔬菜重金属污染评价

通过对来源于广东省516个蔬菜种植基地18种蔬菜品种1 465个样品中铅、镉含量的检测分析,结果表明:蕹菜品种铅平均含量最高(0.11mg·kg-1),西洋菜镉平均含量最高(0.060mg·kg-1);总样品铅检测合格率97.0%,镉检测合格率98.9%;所检蔬菜品种的铅、镉平均污染指数均小于0.7。表明广东省各生产基地的蔬菜重金属安全状况总体较好,处于优良水平。     

重金属铅镉对玉米生长及土壤微生物的影响

采用温室盆栽土培方法,研究了土壤中不同浓度重金属铅（Pb,0-800 mg.kg^-1）、镉（Cd,0-50 mg.kg^-1）单一及其复合处理对玉米（Zea mays L.）生长及土壤微生物（细菌、放线菌、真菌）数量的影响。结果表明,在重金属Pb、Cd单一及其复合处理下,玉米的株高、干重均低于对照,重金属Pb、Cd处理对玉米的生长存在负面影响。重金属Pb、Cd单一处理抑制细菌、真菌的生长,中低浓度Pb（≤300 mg.kg^-1）、Cd（≤10 mg.kg^-1）单一处理促进放线菌数量的增加,高浓度（Pb≥800 mg.kg^-1、Cd≥50 mg.kg^-1）则呈现抑制效应;Pb、Cd复合在高中低浓度下都抑制土壤微生物生长,减少微生物数量。玉米株高同土壤微生物之间相关性不显著;玉米干重同土壤细菌、真菌显著相关,同土壤放线菌之间相关性不显著。     

Field-Scale Assessment of Phytotreatment of Soil Contaminated with Weathered Hydrocarbons and Heavy Metals (9 pp)

Background, Aim and Scope   Phytoremediation is a remediation method which uses plants to remove, contain or detoxify environmental contaminants. Phytoremediation has successfully been applied for the removal of fresh hydrocarbon contamination, but removal of aged hydrocarbons has proven more difficult. Biodegradation of hydrocarbons in the subsurface can be enhanced by the presence of plant roots, i.e. the rhizosphere effect. Phytostabilization reduces heavy metal availability via immobilization in the rhizosphere. Soils contaminated by both hydrocarbons and heavy metals are abundant and may be difficult to treat. Heavy metal toxicity can inhibit the activity of hydrocarbon-degrading microorganisms and decrease the metabolic diversity of soil bacteria. In this experiment, weathered hydrocarbon- and heavy metal- contaminated soil was treated using phytoremediation in a 39- month field study in attempts to achieve both hydrocarbon removal and heavy metal stabilization. Materials and Methods: A combination of hydrocarbon degradation and heavy metal stabilization was evaluated in a field-scale phytoremediation study of weathered contaminants. Soil had been contaminated over several years with hydrocarbons (11400±4300 mg kg dry soil)-1 and heavy metals from bus maintenance activities and was geologically characterized as till. Concentrations of soil copper, lead and zinc were 170±50 mgkg-1, 1100±1500 mg kg-1 and 390±340 mg kg-1, respectively. The effect of contaminants, plant species and soil amendment (NPK fertilizer or biowaste compost) on metabolic activity of soil microbiota was determined. Phytostabilization performance was investigated by analyses of metal concentrations in plants, soil and site leachate as well as acute toxicity to Vibrio fischeri and Enchtraeus albidus. Results: Over 39 months hydrocarbon concentrations did not decrease significantly (P=0.05) in non-amended soil, although 30% of initial hydrocarbon concentrations were removed by the last four months of study. In soil amended with NPK fertilizer and municipal biowaste compost, 65 % and 60 % of hydrocarbons were removed, respectively. The soil contained metabolically diverse bacteria, measured as carbon source utilization and extracellular enzymatic activities. Compost addition resulted in a slight increase in enzymatic activities. Diesel fuel utilization potential in Biolog MT2 plates inoculated with a soil suspension was enhanced by both compost and NPK compared to non-amended soil. Soil toxicity to V. fischeri and E. albidus was low. The leachate was not toxic to V. fischeri. Pine (Pinus sylvestris), poplar (Populus deltoides x Wettsteinii), grasses and clover (Trifolium repens) survived to varying degrees in the contaminated soil. All plants suffered from phytotoxicity symptoms and some trees died during the study period. Plants formed a dense cover over the compost-amended soil, whereas non-amended soil had areas devoid of vegetation throughout the study. Vegetation coverage in the NPK-amended quarter was about 50 % after the first four months of study, but increased gradually to 100 %. Heavy metals did not accumulate in plant tissue. Discussion: Removal of hydrocarbons from weathered unfertilized hydrocarbon-contaminated soil was not statistically significant despite the presence of a viable hydrocarbon-degrading microbial community. This effect is attributed to soil heterogeneity and low bioavailability of hydrocarbons. Hydrocarbon concentrations were not reduced to the desired level, i.e., 1500 mg hydrocarbons (kg of dry soil)-1, in any treatment. . The presence of clay minerals and organic matter within the compost may have limited heavy metal transfer to leachate and plant tissue. Conclusions: Weathered hydrocarbons were partly decomposed in soil fertilized with NPK fertilizer or biowaste compost, but not from unfertilized soil. The active hydrocarbon-degrading microbiota and low toxicity of soil to V. fischeri and E. albidus indicates low availability of contaminants to microorganisms. Despite high heavy metal concentrations, the soil contained metabolically diverse bacteria, measured as carbon source utilization and extracellular enzymatic activities. Heavy metals did not accumulate in test plants. Pine and poplar suffered from phytotoxicity symptoms in the soil and could not enhance hydrocarbon removal in compost-amended soil. Compost addition combined with a grass and legume crop is suggested for stabilization of combined hydrocarbon- and metal-contaminated soil. Recommendations and Perspectives: Both compost and NPK fertilizers can be used to enhance phytoremediation of soil contaminated with weathered hydrocarbons in the presence of heavy metals; however, compost addition is recommended since it enables greater vegetative coverage. This in turn may decrease heavy metal mobility. Phytoremediation can be used for remediation of soil contaminated with weathered hydrocarbons in the presence of heavy metals. However, phytoremediation of weathered contaminants requires extended periods of time; thus, other remediation methods should be considered in the event of soil contamination posing an immediate public health and/or environmental threat.     

贵州万山汞矿区某农田土壤重金属污染特征及来源解析

研究采集万山汞矿区典型农田土壤样品,分析测试其Hg、As、Cd、Cr、Pb、Cu、Zn、Ni含量,利用综合污染指数法、地累积指数法和潜在生态危害指数法评估农田土壤的污染状况及生态风险,结合相关分析和主成分分析解析农田土壤中重金属的来源。结果表明,该农田土壤Hg、As、Cd、Cr、Pb、Cu、Zn、Ni的平均含量分别为4.29、117.6、0.43、59.06、48.99、43.77、29.13、18.80 mg kg~(-1)。土壤重金属综合污染指数为7.16,表明该农田土壤重金属重度污染,其中100%的位点Hg、As重度污染,66.7%的位点Pb轻度污染,25%的位点Cd轻度污染。土壤重金属的综合潜在生态危害指数为469.0,生态风险强,Hg对综合潜在生态危害指数的贡献率为78.30%,是该农田土壤生态风险的主要来源。该农田中重金属的来源包括:交通运输源、矿业污染源、农业污染源和自然活动源,主要污染物Hg来源于矿业活动,As来源于交通运输和矿业活动,Cd来源于农业活动,Pb来源于交通运输。     

Effect of Clay Minerals on Immobilization of Heavy Metals and Microbial Activity in a Sewage Sludge-Contaminated Soil (8 pp)

Background   Aims, and Scope. Reducing heavy metal solubility and bioavailability in contaminated area without removing them from the soil is one of the common practices in decreasing the negative impacts on the environment and improving the soil quality. Therefore, our aim was to study the effect of clay minerals: Na-bentonite, Ca-bentonite, and zeolite applied to a contaminated soil on immobilization of heavy metals, as well as on some soil parameters related with microbial activity. Methods   A soil derived from sewage sludge was incubated with clay minerals of either Na-bentonite, Ca-bentonite, or zeolite for 111 days (d). During the incubation experiment, concentrations of water soluble Zn, Cd, Cu, and Ni were measured after extraction of 2 g air-dry soil with 50 ml of H2O for 2 h. After the water extraction, the soil sediment was extracted with 50 ml of 1 M NH4NO3 for 2 h to estimate the exchangeable amounts of heavy metals. Furthermore, soil microbial respiration, microbial biomass C, Corg mineralization, metabolic quotient (qCO2), and inorganic N were also investigated. Results and Discussion   Water extractable and exchangeable forms of heavy metals were changed by incubation and addition of clay minerals. Incubation of soil without addition of clay minerals (control) increased water extractable Cu by 12, 24 and 3.8% of initial content after 21, 62, and 111 d of incubation, respectively. The water extractable Zn decreased by 9% during 62 d of incubation and it tended to increase by 14% at the end of the incubation, as compared with the initial soil. Water extractable Cd decreased by 71, 66 and 33% of initial content, and Ni decreased by 54, 70, and 58%, after 21, 62, and 111 d of incubation, respectively. During the incubation experiment, the exchangeable form of all tested metals was decreased by incubation. The addition of clay minerals led to a significant decrease in water soluble and exchangeable forms of heavy metals during the incubation experiment, resulting in low metal extractability. The reduction in metal extractability was greater due to the addition of Na-bentonite or Ca-bentonite than that due to the addition of zeolite. During the first 3 weeks after addition of clay minerals, the studied biological parameters were not affected. However, as incubation progressed, the addition of Na- or Ca- bentonite led to a significant increase in soil respiration, microbial biomass C, Corg mineralization, and inorganic N; and a significant decrease in qCO2. This result is explained by sorption of heavy metals on Na-bentonite and Ca-bentonite and strong reduction of their toxicity. Conclusions   Our results clearly show that the addition of clay minerals, especially of Na-bentonite and Ca-bentonite, decreased the extractability of four metals during incubation. The decreased metal extractability was accompanied by an increase of soil respiration, Corg mineralization, microbial biomass C, and inorganic N and a decrease of metabolic quotient (qCO2), showing positive effect of clay mineral addition on soil biological parameters. Recommendations and Outlook   The use of Na-bentonite and Ca-bentonite is promising tool for reduction the extractability and possible toxicity of heavy metals in sewage sludge-contaminated soil. Therefore, the soils polluted with heavy metals may be ameliorated by addition of clay minerals, especially Na-bentonite and Ca-bentonite.     

重金属在猪饲料-粪便-土壤-蔬菜中的分布特征研究

本文调查分析了江西省余江县39个大型养猪场的饲料、猪粪、以及长期施用这些猪粪的菜地土壤及蔬菜的Cu、Zn、Pb、Cd含量,并对饲料、猪粪、土壤和蔬菜重金属含量进行了相关分析。结果表明,大猪和小猪饲料Cu含量超标率分别达81.6%和30.8%,Zn含量超标率分别达89.5%和94.9%,而Pb、Cd未超标。猪粪Cu、Zn含量亦严重超标,且饲料和猪粪中Cu、Zn、Pb、Cd含量呈显著正相关关系。土壤总Zn和总Cd含量分别有7.8%和5.2%的样品超过三级标准,污染较为严重。所有蔬菜样品Cu、Zn、Pb含量均未超过我国食品卫生质量标准,空心菜和芋头Cd含量超标。土壤总Cu、Zn、Cd含量与提取态呈显著正相关。     

采煤沉陷复垦区重金属污染与土壤酶活性的关系

以淮南新庄孜矿采煤沉陷复垦区为研究区域,对脲酶、磷酸酶、蔗糖酶、蛋白酶、纤维素酶、过氧化氢酶、多酚氧化酶7种土壤酶进行了测试分析。结果发现,该区域土壤酶活性受到不同程度的抑制,且7种土壤酶对重金属的敏感性不一致。采用因子分析技术提取主成分,建立了复合污染土壤总体酶活性评价指标,评价了该地区土壤重金属污染程度,并与通过灰色聚类法分析得到的土壤重金属污染等级进行了比对分析,研究了采煤沉陷区土壤酶活性与重金属污染之间的赋存关系,进一步证明在采煤沉陷复垦区这一特殊土地利用条件下,采用土壤酶活性综合指标评价土壤重金属污染是可行的。研究表明,土壤酶总体活性评价指标作为一种简单易行的评价手段,为新庄孜采煤沉陷复垦区及相似矿区复垦地的重金属污染修复提供参考和理论依据。     

Soil Extraction of Readily Soluble Heavy Metals and As with 1 M NH4NO3-Solution - Evaluation of DIN 19730 (6 pp)

Background, Aims and Scope   The German DIN 19730 (1997) describes a method for the extraction of readily available trace elements from soil by shaking the soil with 1 M NH4NO3-solution. Based on this method trigger and action values for the transfer of heavy metals and arsenic from soils to plants have been published in the German Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV 1999). The chemical mechanisms involved in this soil extraction procedure were evaluated in some detail to create requirements to improve environmental risk assessment for soil contaminations.Methods   The chemical mechanisms involved when soil is extracted with 1 M NH4NO3-solution were evaluated. This was followed by a laboratory experiment to quantify the formation of soluble metal ammine complexes during the extraction. Cd, Zn, Ni, Cu, Co and Hg were extracted from 16 soils by 1 M NH4NO3, 1 M KNO3 and water. pH was adjusted in 5 steps between 5.0 to 7.5. The potassium cation (K+) and the ammonium cation (NH4+) behave similarly when cations from soil surfaces are desorbed, because they have almost identical ion radii (e.g. 0.133 and 0.143 nm). K+ does not form ammine complexes with other ions, whereas, due to the increasing formation of NH3 from NH4 by dissociation with rising pH, metal ammine complex formation is an important process in soil extraction when using ammonium salt solutions. A difference in the extraction efficiency of 1 M NH4NO3- and 1 M KNO3-solution for a given soil can therefore be attributed to the formation of soluble metal ammine complexes. Conclusion   Our experiments resulted in considerably higher extraction rates of Cu, Cd and Hg by 1 M NH4NO3-solution as compared to 1 M KNO3-solution. This effect, caused by the formation of soluble metal ammine complexes, was only evident in soils with higher readily soluble heavy metal contents and a soil pH above 6 – 6.5 for Cu and 7 – 7.5 for Cd. Further chemical mechanisms involved when soils are extracted with 1 M NH4NO3 are a moderate decrease in pH and an increase in ionic strength. Most of the colloids and parts of soluble metal-organic complexes are precipitated due to the high ionic strength. High ionic strength also decreases the activity of metal-OH+ species and the electrostatic potential of the particle surfaces, which in turn, increases the desorption of heavy metal cations from negatively charged soil surfaces. In contrast, the adsorption of anions like arsenate is favoured by the decreasing electrostatic potential. The prediction of heavy metal uptake by plants from the results of the 1 M NH4NO3-solution extraction fits well for elements, which are mainly bound by low strength electrostatic forces to the soils. Such conditions are found in acidic soils for Cd and Tl, which have a low tendency for hydrolysis compared to other heavy metals. The correlation between 1 M NH4NO3 soil extraction and plant uptake is less significant for Ni and Zn. Only low positive correlation coefficients have been found for Pb, As, Hg and for the Cu-uptake by wheat. Imprecise prediction of plant uptake of heavy metals by the extraction with 1 M NH4NO3-solution is mainly caused by conditions leading to an overestimation of plant availability such as elements are strongly bound to soils, or low soluble trace element contents in soils. Neutral to alkaline soil pH can also lead to imprecise prediction due to increasing formation of soluble metal-organic (Cu, Pb, Hg) and metal ammine (Hg, Cu, Cd) complexes and less importantly due to the formation of colloids. Therefore, at low 1 M NH4NO3-extractable soil contents usually no high plant contents are to be expected. Recommendation and Outlook   Extraction of soil with 1 M NH4NO3-solution is a suitable method for the determination of readily soluble and plant available trace element contents. The chemical soil extraction process may cause misleading predictions of the transfer of trace elements to plants for some soil properties. This knowledge should be used to improve risk assessment of soil contaminations. It has to be considered, that the processes involved in plant uptake of trace elements are too complex to expect that just one soil extraction method can always guarantee a correct prognosis of toxicological significant element contents in plants. Soil analyses may be used for the preliminary examination of suspicious areas and the demarcation of contaminated areas. The results of soil analyses should be checked additionally by plant analyses especially under conditions with a high probability for misleading results by the 1 M NH4NO3-extraction. Alternatively, extraction with 1 M KNO3-solution can be performed to exclude the effect of metal ammine complex formation.     

上海市某大型再开发场地土壤重金属污染特征、评价及来源分析

[目的]研究土壤中重金属污染与生态风险状况,为保障城市更新改造过程中土地的合理利用提供科学依据。[方法]以上海市某大型再开发利用场地为研究对象,采集了102个点位的表层(0-0.5 m)和下层(1.5-2.0 m)土壤样品,测定10种重金属(As,Be,Cu,Pb,Ni,TI,Zn,Cd,Cr和Hg)浓度,采用地累积指数、内梅罗指数和潜在生态风险指数进行土壤重金属污染和生态风险评价,并进一步利用多元统计分析方法揭示土壤中重金属的来源情况。[结果]①测试土壤中重金属均未超过《土壤环境质量建设用地土壤污染风险管控标准(试行)》(GB36600-2018)第二类用地风险筛选值,但6.9%,24.5%,25.5%,37.3%和63.7%的采样点土壤中As,Cu,Pb,Zn和Hg浓度超过土壤元素背景值,存在不同程度的累积现象。内梅罗指数评价结果表明研究区域土壤整体处于尚清洁到轻度污染状态,分别有11.8%和3.84%的表层区域与2.64%和0.63%的下层区域土壤呈中度污染和重度污染状态。②表层土壤综合潜在生态风险指数均值为89.91,处于中等风险水平,Hg为研究区域主要的生态风险因子。③土壤中Ni,Cr,Be和TI浓度主要受成土母质风化作用的自然源控制,Pb,Zn,Cu,As和Hg主要受交通运输源和历史农业活动源的影响,其中自然源对表层土壤中的As和下层土壤中Cu也有相当比例的贡献,而表层土壤中Hg更多受到除交通运输源以外的其他人类活动源影响。[结论]后续土地利用过程应注重Hg的生态风险管控,并提高对外来交通源引起的重金属累积效应的关注。     

大冶矿区周边农田土壤和油菜重金属污染特征研究

以大冶典型铜矿区为中心,辐射周边农田,探索农田土壤重金属污染特征及重金属在油菜中的积累变化规律。结果表明,以湖北省土壤背景值进行评价,土壤受到重金属不同程度的污染,其中Cd严重超标,Cu次之;采用国家二级标准进行评价,Zn、Cr和Pb未对土壤造成污染。进行内梅罗综合污染指数法评价发现,以土壤背景值为评价标准,各采样点均达到重金属严重污染水平;以国家二级标准评价时,只有2号采样点土壤属于中度污染水平,其他样点土壤都受到了较为严重的重金属污染。矿区农田油菜各部位重金属含量变化幅度较大,包括Cu、Pb、Zn、Cd和Co在内的5种重金属含量分布规律都是茎叶〉籽粒≈根,Mn则是籽粒〉茎叶〉根。油菜地上部植株中Cu、Pb、Zn、Cd含量均超出食品卫生标准最高限值,且Cd、Pb超标倍数远大于Cu、Zn。富集系数变化规律为Mn〉Zn〉Cd〉Ni〉Cu〉Pb垌Co。     

高羊茅和黑麦草对污染土壤Cd,Pb,Zn的富集特征

以潮褐土为供试土壤,通过模拟试验研究了高羊茅(Festuca arundinacea)和黑麦草(Lolium multif lorum)对复合污染土壤Cd,Pb,Zn的富集特点。结果表明,在土壤Cd,Pb,Zn复合污染处理条件下,高羊茅Cd,Pb,Zn的平均富集量,地上部分别为5.76,19.77,418.18 mg/kg,地下部分别为129.82,256.66,354.66 mg/kg;黑麦草Cd,Pb,Zn的平均富集量,地上部分别为5.57,26.13,467.18 mg/kg,地下部分别为114.53,155.98,513 48 mg/kg。通过方差分析,这两种草坪草的重金属富集量没有显著差异,并且富集规律呈现较为一致的特点。地上部的富集量和土壤重金属含量的离子冲量呈显著的线性相关。这两种草坪草对其重金属的富集能力顺序为:Zn>Cd>Pb,其中对Zn的吸收呈现富集植物的特性规律,当土壤Zn含量>400 mg/kg时,其转运系数>1,地上部对Zn的富集能力很强,可作为Zn污染土壤的修复植物。通过偏相关和多元回归分析表明,这两种草坪草在土壤Cd,Pb,Zn复合污染条件下均未产生复合效应。     

黄土高原水土流失区退耕还林(草)的基本思路

朱总理针对1998年我国水土流失加剧而致使洪灾造成2251亿元人民币巨大损失的现实,于1999年8月提出了“退耕还林（草）、封山绿化、个体承包、以粮代赈”的措施,为根治黄土高原的水土流失和良化我国的生态环境指明了方向。文章在上述背景下分析了我国黄土高原地区坡耕地引起水土流失、肥力低下、水源缺乏、灾害频繁的四大问题,根据黄土高原的生态环境脆弱的具体情况,提出了以下几条对策:1 提高思想认识;④解决好退耕后脱贫;（四）推进东西部合作政策;1/4保证人均一定的农田;1/2实现农林牧业最佳结合;3/4提出合理的措施;⑧健全保障机制;（七）正确处理各种关系。研究的基本思路可供同类地区的干部和群众为退耕还林（草）,搞好植树造林,治理水土流失,脱贫致富,建设秀美山川作出贡献。     

采煤沉陷区裂缝边缘带土壤、作物、微生物响应

[目的]研究采煤沉陷区裂缝边缘带土壤、作物、微生物变化特征,为开展沉陷区生态减损与自修复提供理论依据。[方法]以神东矿采煤沉陷区作为研究对象,采用野外监测结合室内分析从裂缝产生初始阶段(LFC)至裂缝发育相对稳定阶段(LFW)15 d内,裂缝边缘带土壤、作物、微生物响应特征。[结果]裂缝边缘带表层10 cm深度范围内土壤含水率在裂缝产生3 d后损失殆尽且后期无法恢复,20 cm以下深度的土壤含水率虽受影响,但并不显著。沉陷区裂缝对土壤理化指标及酶活性产生了扰动影响,但并不显著。沉陷区裂缝发育对边缘带土壤微生物造成了扰动影响,使得土壤微生物群落均匀度、相对丰度降低,细菌相对丰度大于1%的优势菌门少了装甲菌门(Armatimonadetes)、和厚壁菌门(Firmicutes); 真菌相对丰度大于1%的优势菌门少了芽枝霉门(Blastocladiomycota)。RDA分析表明,土壤T,OM,AK,AP,pH,AN是驱动土壤微生物群落结构变化的核心因子。Pearson相关性分析表明裂缝边缘带作物遭受土壤水分和温度胁迫显著,体内可溶性糖SS、超氧化物歧化酶SOD、可溶性蛋白SP、丙二醛MAD含量上升,且受胁迫程度为:玉米>卷心菜>土豆。[结论]沉陷区裂缝发育是推动裂缝边缘带土壤环境因子、微生物群落及作物产生联动响应的源动力。     

三峡库区耕地重金属分布特征初步研究

通过对三峡重庆库区16个市、县(区)旱地和水田土样分析、统计、评价,研究了库区耕地土壤主要重金属元素分布特征。结果表明,库区耕地土壤有不同程度污染,重金属As、Cd、Cu、Ni的含量均有超标,Cd有最大超标;旱地土壤重金属含量略高于水田,紫色土略高于黄壤,各采样点重金属含量差异大;重金属元素Cd、Pb、Cu、As、Zn间存在极显著正相关,土壤污染有复合污染趋势;主要淹水区县土壤环境质量评价结果显示,仅巫山县污染综合指数评价为中污染,主城区、开县为轻微污染,涪陵区、长寿区、奉节县为警戒级,其余为安全级;耕地土壤中重金属元素均未超过土壤环境基本容量,能够保证作物品质和农业持续发展。同时对三峡库区耕地重金属淹水和非点源污染进行风险分析,指出库区开展淹水重金属形态与非点源污染输出研究意义.