Assessment of soil contamination by the content of heavy metals in the soil profile

A new soil-ecological definition of the maximal permissible concentration (MPC) of heavy metals in soils is suggested that regulates the sampling in contaminated territories. Instead of the shallow pits usually used for collecting surface samples for soil-hygienic and other investigations, it is proposed to fulfill a detailed analysis along the entire soil profile including not only the determination of the heavy element content in certain horizons but also the soil density in these horizons. For the polyelemental contamination Zc (according to the Saet equation) based on the background (clarke) excess, the established Zc values ranging from 1 to 128, may reach absurd values of 800–900 upon taking into consideration only one surface layer. At the same time, the use of the weighted average content of the metals in the soil profile adjusts the Zc values for the existing natural conditions. Upon aerial impact, the consideration of the heavy metal contents along the soil profile instead of their contents in the surface horizon only leads to a decrease in the indices of the soil contamination degree. Upon the hydrogenic impact, the transition from the heavy metal contents in the surface horizon to their contents in the soil profile gives higher values of the soil contamination.     

矿化垃圾施用林地重金属污染潜在生态风险评价

以矿化垃圾施用林地土壤为研究对象,采用Hakanson潜在生态风险指数评价法对5种重金属元素Cd,Hg,As,Cr,Pb的潜在风险进行评价,同时还对不同深度土壤重金属的迁移及污染程度进行了讨论.不同矿化垃圾添加量下0-90 cm土层的潜在生态风险综合评价结果表明,随着矿化垃圾添加量增加,土壤重金属污染有加重的趋势,25％与50％矿化垃圾添加量的土壤污染程度达到中等程度,1oo％矿化垃圾添加量的土壤达到重度污染程度.矿化垃圾对土壤造成的污染主要集中在0-50 cm土壤层内,对垂直方向50 cm以下土壤影响较小.Hg是矿化垃圾施用中最主要的污染因子.土壤剖面垂直方向重金属含量分析结果表明,Cd,Hg,As,Cr,Pb具有从土壤表层向下层递减的趋势.重金属元素Hg和Cr含量具有土壤表层富集的特征.矿化垃圾大量的施用可能会导致Hg和Cr土壤污染,但不会导致Cd,As,Pb在土层中累积与垂直迁移.     

干旱矿区废弃地重金属生境土壤种子库时空动态

通过不同季节野外调查取样和室外萌发试验,分析了干旱矿区重金属生境土壤种子库的时空动态。研究结果表明,该区域土壤种子库储量随季节变化存在差异。土壤种子库储量10月最高,5月份减小至最低。土壤种子库物种种类随时间的变化与土壤种子库储量相似;土壤中种子主要分布在0-5 m土层中,该层种子比例平均占种子库全部种子数量的76.5%。随着土层深度的增加,种子数量逐渐减少。5-10 cm土层中种子比例平均只占种子库全部种子数量的23.5%。10 cm以下土层几乎没有种子分布。     

岷江干旱河谷-山地森林交错带根层土壤碳活性与储量特征

根层土受植物地下部分生命活动、代谢影响最直接和最强烈,其碳活性与储量特征对土壤质量改变乃至全球气候变化具有极高的灵敏性。以岷江干旱河谷-山地森林交错带及邻近生态系统为研究对象,研究根层土壤易氧化碳、微生物量碳等碳活性以及碳密度、碳储量特征,可为该区的生态系统管理提供重要科学依据。结果表明,不同生态类型根层土的土壤碳密度为(0.14±0.007)～(101.16±0.301)kgC/m2,碳储量为(30.2±1.51)～(21850.6±65.02)kg。相对于干旱河谷,交错带根层土壤易氧化碳、微生物量碳等碳活性更强,为沿交错带逐步向下改善土壤环境抑制干旱河谷区上延提供了较好的碳素环境。尽管交错带天然林植被面积较小,但其土壤碳密度和土壤有机碳丰度指数因物种优势和所在山地垂直带谱中所处的相对有利位置,显著高于干旱河谷。在交错带内部,以高山栎为优势种的根层土具有更强的储碳能力,是包括退耕还林地在内的自然或人工植被调控生态工程建设中重要造林树种和恢复模式。     

污灌对潮土重金属含量及分布的影响——以开封市化肥河污灌区为例

以开封市化肥河污灌区为例,研究了污水灌溉对潮土中重金属(Cd、Pb、Cr、Cu、Zn、Ni和 As)含量及分布的影响。结果表明,污水灌溉已经导致了该区潮土较明显的重金属累积,其中Cd和As平均含量分别达1．70 mg/kg和26．28 mg/kg,远远超出了土壤环境二级标准值。进入潮土的重金属主要累积在潮土的耕作层,随着土壤深度的增加,重金属含量逐渐减少;相对其他重金属而言,As更易于在潮土表层滞留。污灌区潮土 Cu、As与Cd含量与距污染源距离呈线性相关。相关分析表明,污灌区土壤Cu、Zn、Pb、Ni和As含量与土壤理化性质及其他重金属含量有关,而土壤Cd和Cr含量则与其他重金属含量及土壤性质的相关性不明显。     

华北地区有机种植与常规种植土壤质量比较研究

为探讨有机种植与常规种植两种不同种植方式对土壤质量的影响,本文在华北地区选取典型的有机种植基地与附近相似条件的常规种植地块,比较了不同种植方式下土壤体积质量、土壤中水稳性团聚体及土壤中各养分含量和土壤中7种重金属含量。结果表明:相比常规种植,有机种植降低了土壤体积质量,提高土壤中水稳性大团聚体数量,提高了土壤中水稳性团聚体的MWD值和GMD值,降低了分形维数D,提升了土壤水稳性团聚体稳定性,提高了土壤抗侵蚀的能力。有机种植方式下土壤中有机质含量相比常规种植提高了20%~80%,土壤中速效磷、速效钾、碱解氮和全氮、全磷等养分含量也显著提高,说明有机种植有利于土壤培肥,提高土壤肥力。与土壤背景值相比,土壤中重金属含量有不同程度的增加和积累,曹县有机基地As含量超过土壤环境质量国家一级标准,肃宁有机基地土壤中Cu、Zn含量接近国家一级标准。在调查地区,有机种植降低了土壤中Cr、Cd、Hg污染的威胁,但由于施入有机肥的质量差异,存在重金属Cu、Zn、As富集的风险。相比常规种植,有机种植有利于改善土壤结构,提高土壤综合肥力,土壤中重金属污染的风险主要与施入的有机肥质量有关,有机种植应加强对有机肥源的监控,合理施肥。     

Use of regulatory documents for assessing the contamination of soils with heavy metals

The chronological review and analysis of the existing regulatory documents relevant to the assessment of soil contamination with heavy metals have been presented. Attention has been given to the incorrect use of the term “total heavy metal content” and the method of its determination in a 5 M nitric acid solution recommended by some regulatory documents. The maximum permissible concentrations (MPCs) and tentatively permissible concentrations (TPCTPCs) for the total heavy metal contents are based on the above method; therefore, the conventional methods of determining the true total contents of heavy metals overestimate the degree of contamination. To avoid confusion, it has been proposed to call the content of a heavy metal in a 5 M nitric acid solution the “pseudototal” content and to compare the experimental results with the MPC or TPCTPC values only if the methods recommended by the regulatory documents were used.     

Features of technogenic metal pollution of roadside soil according to x-ray fluorescence monitoring data

X-ray fluorescence monitoring of technogenic metal pollution of Moscow soil near two highways with heavy traffic was fulfilled. As a result of vehicles running, the macro and microelement composition of Moscow roadside soil was seen to substantially differ from the composition of both soddy podzolic soil (typical for Moscow region) and any other soil of the temperate climatic region of Russia. The average Fe, Mn and Ti contents in soil were found to exceed the usual background level by 2–5-fold, maximum Pb content — by 10–15-fold. The lateral and depth distribution of enumerated metal contents in soil near the highways was studied. It was shown that the behavior of lateral pollutant distribution in soil has no specific exponential shape. It has local extremuma and depends on the metal nature and the roadside terrain topography. For Pb — one of the most dangerous pollutants — the mechanism of chemical transformations and the interrelation of the pollutant chemical form, its molecular weight, the dwelling time in atmosphere and the distance to the highway were discussed.     

Profile Distributions of Lead,Zinc, and Copper in Dystric Cambisols Developed from Granite and Gneiss of the Sudetes Mountains,Poland

Total contents of Pb, Zn and Cu were examined in twenty-five soilprofiles of forested Dystric Cambisols developed from granite andgneiss in the area of the Sudetes Mountains (SW Poland). Sequential extraction of heavy metals was also carried out to study relations between metal content and soil compounds. Profile distribution differed among the metals examined: Pb concentrations decreased gradually from surface with depth, whereas those of Zn increased with depth of soil profile, obtaining their maximum in the bedrock horizon. Cu was found to accumulate in topsoil and decrease with depth, but showed secondary increase of the concentration in bedrock. Organic matter was found to be a crucial factor of Pb binding and distribution, while iron oxides played the most important rolein Zn binding. Both organic matter and oxides were important factors of Cu distribution. The results of sequential extractionshow that all studied elements are mobile under strong acidicconditions in investigated Cambisols. Thus, total contents of Zn and Cu in bedrock cannot be used as geochemical background or as reference levels for assessing the contamination of soilsurface with these metals.     

The effect of tree roots on the redistribution of <Superscript>137</Superscript>Cs in the soils of pine and birch forests of the radioactive contamination zone

Accumulation and distribution of ¹³⁷Cs by the root systems of forests in the radioactive contamination zone of Bryansk oblast have been discussed. It has been found that the phytomass and distribution of roots of pine and birch trees along the soil profile in the studied BGCs differ considerably. The specific activity of ¹³⁷Cs in the roots changes depending on their diameter: the lowest specific activity is observed in small fractions of the roots, and the highest one in large fractions. It has been shown that the contribution of roots in the total reserves of ¹³⁷Cs in the soil layer of 0–50 cm of various biogeocenoses is different: the largest contribution is characteristic for birch forests (1.66%) with variation of this parameter in separate soil layers from 1.12 to 3.53%, while the contribution for pine forests is lower (0.97%) with the variation from 0.82 to 7.5%. The contribution of roots to the overall contamination of soils in the studied plant communities increases with depth.     

Judging Fitness for Purpose of a X-ray Fluorescence Based Method Investigating the Vertical Distribution of Metals and Metalloids in Soil Profiles

A column of soil, excavated from a contaminated landscape was evaluated by means of X-ray fluorescence analysis. The measurements were intended to assess the vertical distribution of heavy metals and toxic elements in the depth profile. To judge fitness for purpose of the analytical method used the element specific power functions were derived yielding the minimum detectable variations of analyte concentrations refer to the investigated soil profile. The required measurement uncertainty components caused by both the sampling procedure and chemical analysis were empirically estimated using a nested sampling design (duplicate method). For this purpose the full length of the soil core was divided into horizontal layers. From each selected layer (sampling target) two composite samples were taken by simple random sampling to represent the typical composition of the sampling target. The pool of measurement results, obtained for the nested sampling design finally was subjected to variance analysis. The evaluation of the estimated variance components in terms of the percentage of total variance confirmed fitness for purpose for the method used.     

Distributions of Heavy Metals and Benzo[<Emphasis Type="Italic">a</Emphasis>]pyrene in Oligotrophic Peat Soils and Peat Gleyzems of Northeastern Sakhalin

The contents and profile distributions of Cr, Ni, Cu, Zn, Cd, Hg, Pb, and benzo[a]pyrene in oligotrophic peat soils, oligotrophic peat gley soils (Dystric Fibric Histosols), humus-impregnated peat gleyzems (Dystric Histic Gleysols), and mucky gleyzems (Dystric Gleysols) have been analyzed with consideration for their degree of oligotrophicity and anthropogenic loads. Horizons with the accumulation (O, Tpyr, TT) and removal (Ghi,e) of heavy metals have been revealed. The increase in the content of heavy metals and benzo[a]pyrene in the upper layer of oligotrophic peat soils under technogenic fallouts in the impact zone of flare and motor transport has been considered. Statistical parameters of the spatial variation of parameters in organic and gley horizons have been calculated. The variation coefficients of pollutant elements (Pb and Zn) in the surface horizons of soils increase to 100–125%. Positive correlations revealed between the content of some heavy metals in litter indicate their bioaccumulation and possible joint input with aerotechnogenic fallouts. No correlations are found between the contents of benzo[a]pyrene and heavy metals, but a reliable negative correlation with the ash content is noted in the peat horizon.     

Alternative technologies for remediation of technogenic barrens in the Kola Subarctic

The efficiency of remediation of technogenic barrens under the reduction of air pollutant emissions from the Severonikel smelter in the Kola Subarctic is determined largely by the soil state and the technology applied. The covering of the contaminated soils with artificially made material based on organomineral substrates and the following liming and fertilization promoted a sharp and long-term reduction of acidity, decrease in the biological availability of heavy metals, increase in the supply with nutrients, and improvement of the life state of willow and birch plantations. The effect of economically more profitable chemo–phytostabilization is short-term; it requires constant maintenance. Under the current production and a high level of soil contamination, repeated measures are required to optimize the soil reaction, supply with nutrients, and to correct the availability of heavy metals in the soils based on the results of continuous monitoring     

Temporal and Spatial Monitoring of the pH and Heavy Metals in a Soil Polluted by Mine Spill. Post Cleaning Effects

The bursting of the mining dam of Aznalcollar (Seville, Spain) triggered an increase in the concentration of heavy metals in the soils of the river Guadiamar valley as a result of the leaching of the pyritic sludge deposited on them. After the cleaning operations which included, as well as mechanical clearing, the addition of different amendments, some areas with residual sludge remained, from which some heavy metals are being mobilized by the cyclical recharge and discharge processes of water in the profiles. This paper analyzes the effect of the soil recovery operations and the climatology on the concentration of metals and their distribution in the soil profile in an area affected by the toxic spill. Fourteen points have been selected in a plot in which acidity persists, there is no vegetation, and residual sludge stains can be seen at a glance. The temporal and spatial evolution of the extractable metals: Fe, Cu, Mn and Zn, the pH and the oxidable fraction has been measured in-depth. The results obtained up to now indicate a leaching of the pollutant towards deeper horizons, finding, at a depth of 757 cm, pH values of 3.5 and very high Fe and Mn concentrations available, especially in the profiles with large sized pores, with a big fraction of sand. On the surface, seasonally, there are low pH values of around 2.5 and extractable Fe contents of over 4000 ppm, which might have an influence on the quality of surface runoff or underground water.     

Anthropogenic Soils on the Territory of the New Jerusalem Monastery,Moscow Region

The soil cover inside the walls of the New Jerusalem Monastery (in the city of Istra, Moscow region) has been completely transformed during the long history of anthropogenic loads on the local landscape. Specific anthropogenic soils have been formed from the technogenic deposits on the top and slopes of the monastery hill. These soils contain numerous artifacts; in their upper part, horizons with characteristic features of the modern humus-accumulative process have been developed. The major types of anthropogenic soils on the territory of the monastery—urbiagrostratozems, soddy urbistratozems, and soddy-calcareous urbistratified soils—have been described. The composition of technogenic deposits determines the shift of pH values towards the alkaline reaction, the high content of available phosphorus compounds, and the soil contamination with heavy metals. The post-alluvial gray-humus soils close in their morphology and chemical properties to the natural soils of the floodplain predominate in the soil cover of the park zone adjacent to the walls of the monastery in the Istra River valley.     

Soil contamination in the zone affected by waste products of Tin Ore Processing in the Khabarovsk region

The degree of soil contamination in the impact zone of the Solnechnyi Tin Ore Processing Plant in the Solnechnyi district of the Khabarovsk region was evaluated. It was shown that the air contamination by the waste products of the ore-processing plant is extremely high with respect to the concentrations of toxic dust and heavy metals. The maximum concentrations of these contaminants exceed the background values by 16–80 times. The bulk contents of Pb, Zn, Cu, As, and Hg in the upper soil horizons within the impact zone exceeded the maximum permissible concentrations and the background values by 2–90 times. Abnormally high concentrations of Zn, As, and Pb were observed not only in the surface 10–cm-thick soil layer but also in the underlying (10–20 cm) horizon. The soil contamination transformed the geochemical sequence of heavy metals typical of the background soils (Zn > Pb > As > Cu > Hg) into a new sequence (As > Pb > Cu > Zn > Hg). The statistical data proved that the intensity of the migration of the heavy metals in the soils decreases with a rise in the soil humus content and a drop in the soil acidity. This should be taken into account in the elaboration of soil-protective measures in the investigated region.     

Effect of sewage sludge on some chemical properties of calcareous sandy soils

Abstract

City sewage sludge was applied to the surface layer (0–10 cm) of two sandy soils, slightly calcareous with 8.9% CaCO₃ and moderately calcareous with 26.7% CaCO₃, at the rates of 0, 25, 50, 75, and 100 Mg ha^‐1. The effects of sewage sludge and its rates on total soluble salts, pH of soils and concentration and movement of some heavy metals within soils were investigated. Soil samples were packed at bulk density of 1.5 g cm^‐3 in PVC columns and incubated for 19 weeks. The results indicated that total soluble salts (EC) of the treated layer increased with increasing sewage sludge rates. Soluble salts also increased with an increase in soil depth for both soils. The pH values of treated layers in two soils decreased with increasing sewage sludge rates. With increasing sewage sludge rates, concentrations of heavy metals [cobalt (Co), nickel (Ni), cadmium (Cd), and leaf (Pb)] increased in the treated layers compared to the untreated layers and their mobility was restricted mostly to the upper 30‐cm depth. Movement of Co and Pb in both the soils was predominately limited up to a depth of 40 cm for Co and 5 cm for Pb below the treated soil layer. Nickel and Cd movement was mostly limited to a depth of 10 cm in slightly calcareous soil and 5 cm in moderately calcareous soil. Metal movement in the respective soils is ranked as Co>Ni=Cd>Pb and Co>Ni=Cd>Pb. The low concentrations of heavy metals and the restricted mobility with soil depth, suggest that this material may be used for agricultural crop production without any toxic effect on plants.     

Priority organic pollutants in soils of the arboretum in the Botanical Garden of Moscow State University

The distribution of different homological groups of polychlorinated biphenyls (PCBs) in the urbanozem profile of the arboretum in the Botanical Garden of Moscow State University has been considered. The levels of their content, the composition of a congener spectrum, potential sources, and the ecotoxicological impact of soil pollution are assessed. The maximal concentrations of di-, tri-, and tetrachlorbiphenyls are observed in the technogenic layer of soil at a depth of 20–40 cm (0.30, 0.44, and 24.25 μg/kg, respectively), and penta- and hexachlorbiphenyls in the surface humus layer (42.33 and 17.89 μg/kg, respectively). The content of hepta- and oñtachlorbiphenyls varies insignificantly with increasing the depth (0.67–1.25 and 0.15–0.41 μg/kg, respectively). Penta- and hexachlorbiphenyls contribute most to the spectrum of PCBs in urbanozem.     

Preliminary Assessment of Oil Contamination Levels in Soils Contaminated with Oil Lakes in the Greater Burgan Oil Fields,Kuwait

Measurements taken for total petroleum hydrocarbons (TPHs), total organic carbon (TOC) and trace metals [vanadium (V), nickel (Ni), cadmium (Cd) and lead (Pb)] in 40 soil samples are used to delineate oil contamination levels and state of oil penetration in soils heavily contaminated with oil lakes in Al-Ahmadi and Burgan oil fields. All soil horizons in Al-Ahmadi profile contain very high concentrations of TPHs down to the depth interval 80–95 cm. In contrast, TPH contaminations are restricted to the upper 50 cm layer in the Burgan profiles, then drop sharply to natural background levels in subsequent soil horizons. A strong and positive relationship exists between the high TOC and TPH contents of the two profiles. The two soil profiles contain contaminations of V and Ni as well as high concentrations of Cd and Pb. Possible sources of these metals are oil contaminants from the lakes and/or deposited airborne oil fallouts. V/Ni ratios of the surface tar sludge and the soil horizons in the two profiles cannot be used in identifying terrestrial oil spills or as indicators of oil contamination in Kuwaiti soils.