Human health risk assessment associated with Co,Cr, Mn,Ni and V contents in agricultural soils from a Mediterranean site

Potentially toxic element contents in agricultural soils were assessed by comparison with levels recorded in the literature and evaluated using Index of Geoaccumulation (I_geo). The model recommended by United States Environment Protection Agency is applied for the health risk assessment from different exposure pathways. The median values of cobalt (Co), chromium (Cr) and nickel (Ni) exceeds about 2, 3 and 14 times, respectively, the corresponding values given by the Geochemical Atlas of Europe project, however, they present low potential ecological risk. The median values of manganese (Mn) and vanadium (V) are slightly lower than the corresponding values given by the Geochemical Atlas of Europe project. Risk assessment results present negligible health risk to children and adults due to manganese (Mn), nickel (Ni) and vanadium (V) exposure through ingestion of contaminated soil. Only the cobalt (Co) hazard quotient (HQ) and hazard index (HI) for children around two sampling sites exceed the acceptable safe risk level.     

滇东农田土壤铅污染健康风险评价及基准研究

农田土壤重金属污染造成农产品中重金属含量超标进而通过食物链对人体健康的风险和隐患不容忽视,滇东农田土壤同时受到高地质背景与矿业活动叠加的双重影响,铅污染的问题开始受到广泛关注。为了掌握滇东地区土壤-作物系统铅累积规律及其健康风险以及农田土壤铅健康风险基准,通过对滇东6个市（州）农田土壤和农产品点位协同采样,探讨滇东土壤及其种植农作物中铅的累积特征及健康风险状况,并基于物种敏感分布模型（Log-logistic）反推滇东农田土壤铅安全基准值。结果表明：1）滇东不同市（州）农田土壤中铅含量平均值从大到小依次为红河州、曲靖市、昭通市、文山州、玉溪市、昆明市,其中,昭通市、曲靖市、文山州和红河州农田土壤均存在轻微程度的铅超标问题;2）滇东6个市（州）农产品总的点位超标率为11.9%;不同类别作物吸收富集铅的能力不同,豆类的豌豆和花生对铅具有较高的富集能力,其次是根茎类的莴笋、叶菜类的油菜和谷物类的小麦。3）健康风险评价结果表明,滇东各区域农田土壤重金属铅对居民不存在明显的非致癌风险和致癌风险,铅在不同区域对儿童产生的非致癌风险大于成人,不同暴露途径非致癌健康风险指数从大到小依次为手-口摄入、皮肤接触、呼吸吸入;4）基于物种敏感性分布模型反推滇东农田土壤铅健康风险基准值,种植根茎类、茄果类、叶菜类、豆类、谷物类物时,其临界值分别为13.0、19.7、35.1、11.3、18.1 mg/kg;其警戒值分别为269.5、481.3、500.7、367.5、560.3 mg/kg。研究结果可为滇东以及类似区域铅高背景区农田土壤制定更为精准的地方标准、实现铅污染土壤安全利用提供科学依据。     

三峡库区典型农业区土壤重金属污染特征及风险评价

为了解三峡库区农业区土壤重金属污染现状及环境风险水平,该文以重庆市8个典型农业区县(铜梁、云阳、万州、丰都、城口、垫江、南川和江津)土壤为研究对象,共采集表层(0~20 cm)土壤样品160个,依照《土壤环境监测技术规范(HJ/T 166-2004)》和《土壤环境质量标准GB 15618-1995》分析了土壤样品中8种重金属(As、Cd、Cr、Cu、Hg、Ni、Pb和Zn)的含量,比较了不同区县8种重金属污染现状及差异,应用地积累指数法和潜在生态风险指数法探讨了研究区土壤重金属的累积特征及潜在生态风险等级。结果表明:该研究区农业土壤8种重金属含量平均值均未超过《土壤环境质量标准GB 15618-1995》二级标准,与土壤背景值相比,Cd、Cr、Cu、Hg和Zn均具有极显著差异(P0.01),As、Ni和Pb差异不显著,8个区县Cr均表现出极显著差异(P0.01),城口区多种重金属均表现出极显著差异(P0.01),8种重金属地累积指数平均值均小于0,研究区土壤受重金属污染水平为未污染等级,单个重金属潜在生态风险顺序为HgCdAsHgCuNiCrZn,Hg元素潜在生态风险指数平均值为43.840,属中等生态风险等级,其余元素生态风险指数值均小于40,属于低生态风险等级,8种重金属综合潜在生态风险指数平均值为108135,为低生态风险等级。综合研究结果表明:三峡库区典型农业区土壤Cd、Cr、Cu、Hg和Zn具有一定程度的累积,且表现为多种重金属复合累积现象,Cr累积具有普遍性,Hg是影响三峡库区农业土壤综合潜在生态风险的主要元素,但研究区土壤重金属总体处于低生态风险水平。     

Contents and bioavailability of rare earth elements in agricultural soils in Hesse (Germany)

With increasing agricultural and industrial use of rare earth elements (REEs), input of REEs into the pedosphere has risen in parallel. Since total REE budgets for soils in Germany are mainly unknown, this pilot study investigates the concentrations of REEs in three loess soil profiles under agricultural land use in the Wetterau region, Germany. There were no significant REE applications in the past, so the presented data can be considered as background concentrations of REEs in soils. In addition to the total REE contents (aqua regia digestion), potentially plant‐available (EDTA) and at actual conditions available, mobile (NH₄NO₃) REEs have been determined for each horizon. Interactions between REE availability and properties of soils are explained after assessing several chemical and physical properties. The results reveal a wide range of total REE contents, ranging from 222 to 423 mg kg^–1. With 10.1% of total REE amounts, the potentially plant‐available proportions of REEs are generally low. In contrast, yttrium, which showed high available proportion of 24.8%, was found to be comparable with Cd. Cerium is the most abundant REE in aqua regia digests, whereas only small amounts in the potentially plant‐available fraction were found. Thus negative cerium anomalies could be concluded concerning its potential availability. Generally, bioavailability of REE had significant correlations between clay contents and Fe and Mn oxides for the majority of REEs. Due to moderately high pH (CaCl₂) in soils (average 6.6) the mobile fraction for most of the elements was not detectible.     

A critical state soil mechanics model for agricultural soils

Abstract. The paper presents the experimentally derived state boundary surfaces of critical state theory for a sand, a loam and a clay soil. Orderly changes to these surfaces with moisture content and two soil micro-structural states have been identified. These findings are used as the basis for the formulation of a fairly simple universal model of the geometry of critical state space for unsaturated soils. Examples are given of how this model can be used to explain known soil behaviour in many practical situations. The indications are that this model can provide the theoretical framework for a fundamental comprehension of the many complex processes involved in soil loosening and compaction. There is, as yet, no simple experimental technique for measuring the critical state boundaries of field soils and this is a major impedement to the development of the model as a practical soil management tool.     

Heavy metal pollution of agricultural soils and sediments in Liaoning Province,China

Heavy metal pollution of soils and sediments in Liaoning Province, Northeast China, was investigated. Fifty seven samples of agricultural soils and 8 samples of sediments were collected in 1996 from paddy or upland fields and irrigation channels, respectively, in Shenyang, Fushun, Liaoyang, Anshan, and Tieling regions, and concentrations of total and 0.1 mol L^-1 HCI-extractable Cd, Cu, Pb, and Zn were analyzed using ICP spectrometry. Seventeen samples of unpolished rice were also collected from selected paddy fields and total concentrations of the four elements were determined.–

Both paddy and upland soils were polluted with Cd: average total concentration was 0.70, 0.57, and 0.53 mg kg^-1 in the western and southern parts of Shenyang, and Anshan, respectively, and significantly higher than the background level of 0.32 mg kg^-1. Cd concentrations of four samples exceeded even 1 mg kg^-1, which corresponds to the critical level of Cd contamination in China. About 65% of the total Cd was extracted with 0.1 mol L^-1 HCI, suggesting that Cd was relatively mobile compared with other metals. The level of Cd pollution was, however, lower than that previously reported and serious polIution was not observed for Cu, Pb, and Zn. Accordingly, Cd concentration in upland rice was within the range of the unpolluted level in this study. Nevertheless, Cd concentration in a sediment of irrigation channels in the western part of Shenyang exceeded 16 mg kg^-1, indicating the possibility of further contamination of agricultural soils. In conclusion, soils and sediments were still polluted with Cd in the southern part of Shenyang, Anshan, and especially in the western part of Shenyang, and further countermeasures are urgently required to ensure safe food production in these regions.     

A decision support system for compaction assessment in agricultural soils

Research was conducted to develop a knowledge-based decision support system to assess the degree of compaction in agricultural soils. The experiments were conducted in a laboratory soil bin at the Asian Institute of Technology in three soils, namely, clay, silty clay loam, and silty loam. The research was likewise aimed to quantify the effect of tire variables (section width, diameter, inflation pressure); soil variables (soil moisture content, initial cone index, initial bulk density); and external variables (travel speed, axle load, number of tire passes) on soil compaction and to develop compaction models for soil compaction assessment. Dimensional analysis technique was used in the development of the compaction models.

The soil compaction models were found to provide good predictions of the bulk density and cone index. Using the compaction models and other secondary data, the decision support system was developed to assess the compaction status of the soil in relation to crop yield. The predictions by the decision support system were validated with actual field data from earlier studies and high correlation was observed. Thus, the output of the decision support system may be able to provide useful recommendations for appropriate soil management practices and solutions to site-specific soil compaction problems.     

Biotesting for Cd pollution in soils

The potential of biotesting to detect and analyze Cd pollution in soils was studied. This paper identifies a number of approaches, such as PICT and discriminant analysis, which may open new perspectives for ecotoxicology.     

Extractability of major and trace elements from agricultural soils using chemical extraction methods: Application for phytoavailability assessment

Abstract

To assess soil-to-plant transfer of various elements more precisely, the concentrations of the elements extracted from soil samples using eight chemical solutions were compared with the results of a pot cultivation experiment of komatsuna (Brassica rapa L. var. perviridis) or buckwheat (Fagopyrum esculentum M.) using the soils. From agricultural fields in Aomori, Japan, 16 soil samples were collected. Elements in the samples were extracted using acids (1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃, 0.01 mol L^?1 HNO₃), chelating agents (0.05 mol L^?1 EDTA), neutral salt solutions (1 mol L^?1 NH₄OAc, 1 mol L^?1 NH₄NO₃, 0.01 mol L^?1 CaCl₂) and pure water. The 28 elements in the extracted solutions and plant samples were determined. The extractability of many metals was higher in 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ and the 0.05 mol L^?1 EDTA solutions than in the other extractants. Higher extractability using the NH₄OAc solution than the NH₄NO₃ solution was observed for some elements, in particular U. Extractability by pure water was not always lowest among these methods, probably because of dispersion of colloidal substances in the extracted solution. The pot cultivation experiment showed that the concentrations in soil and in the extracted fraction using 1 mol L^?1 HNO₃, 0.1 mol L^?1 HNO₃ or the EDTA solution did not correlate with the concentration in plant samples for most elements. Plant uptake of Zn, Y and La by komatsuna correlated well with their concentrations in extracts with neutral salt solutions or 0.01 mol L^?1 HNO₃. Concentrations of Al, Cu and Cd in buckwheat were also correlated with the concentrations in the extracts.     

Effects of pH and polycyclic aromatic hydrocarbon pollution on thaumarchaeotal community in agricultural soils

Purpose

Thaumarchaeota is an ecologically relevant archaeal phylum which may significantly contribute to global nitrogen cycling. Thaumarchaeotal abundance, composition, and activity can be changed by soil pH and pollutants such as toxic metals. This study aims to examine the responses of thaumarchaeotal community to soil pH variation and polycyclic aromatic hydrocarbon (PAH) pollution which may co-occur in agricultural soils.

Materials and methods

Field soil samples were collected from agricultural land impacted by both acidification and PAH contamination. Thaumarchaeotal abundance and composition were assessed using molecular approaches targeting 16S rRNA or amoA genes and were linked to environmental factors by correlation and canonical correspondence analysis (CCA). To evaluate the short-term responses of Thaumarchaeota to PAHs, additional soil microcosms amended with either three selected PAHs were established. Changes in thaumarchaeotal communities during the incubation were monitored.

Results and discussion

A significant correlation between thaumarchaeotal gene abundance and soil pH was observed within field samples, with the I.1a-associated group enriched when pH <5.0. CCA suggests that the community variation was primarily related to soil pH. In contrast, the effects of PAHs were minimal. In soil microcosms, high concentrations of PAHs persisted after the 4-week incubation. Independent of the PAHs added, thaumarchaeotal amoA abundance slightly increased and the compositions were stable at the end of the incubation. This might be associated with the pollutants bioavailability and potential microbe-PAH interactions in the soil.

Conclusions

Soil pH variation strongly shapes the agricultural soil thaumarchaeotal community, whereas PAH effects appear to be marginal even in the presence of high concentrations of pollutants. The complicated interaction between soil matrix, pollutants, and Thaumarchaeota requires further study.

     

伊朗东北部的农业和牧场土壤孔隙大小分布作为土壤物理质量指标

Assessment of soil quality is important for optimum production and natural resources conservation. Agricultural and pasture soil qualities of Deh-Sorkh region located at south of Mashhad, northeastern Iran were assessed using the integrated quality index (IQI) and Nemero quality index (NQI) models in combination with two datasets, i.e., total data set (TDS) and minimum data set (MDS). In this study 6 soil properties considered as MDS were selected out of 18 properties as TDS using principle component analysis. Soil samples were divided into 3 groups based on optimum ranges of 8 soil physical quality indicators. Soil samples with the most indicators at optimum range were selected as group 1 and the samples having fewer indicators at optimum range were located in groups 2 and 3. Optimum ranges of soil pore size distribution functions were also determined as soil physical quality indices based on 8 soil physical quality indicators. Pore size distribution curves of group 1 were considered as the optimum pore size functions. The results showed that relatively high organic carbon contents could improve pore size distribution. Mean comparisons of soil physical quality indicators demonstrated that mean weight diameter of wet aggregates, structural stability index, the slope of moisture retention curve at inflection point, and plant available water content in agricultural land use decreased significantly in relation to pasture land use. In addition, the results demonstrated that the studied MDS could be a suitable representative of TDS. 78% of pasture soils had the optimum pore size distribution functions, while this parameter for agricultural soils was only 13%. In general, the soils of the studied region showed high limitations for plant growth according to the studied indicators.     

Arginine ammonification assay as a rapid index of gross N mineralization in agricultural soils

Seasonal dynamics of in situ gross nitrogen (N) mineralization rates were measured using the ¹⁵N-NH₄⁺ isotope dilution method in a Danish soil subjected to four different agricultural practices (set aside, barley, winter wheat and clover). Results were compared to arginine ammonification in the soil samples measured as NH₄⁺ production following addition of excess (1 mM) arginine. In the set aside, barley, winter wheat and clover soils the average annual rates of gross N mineralization (0.29, 0.60, 1.34 and 1.75 µg NH₄⁺-N g^-1 day^-1, respectively) and arginine ammonification activity (0.21, 0.55, 0.88, and 1.33 µg NH₄⁺-N g^-1 h^-1, respectively) were well correlated. Furthermore, the seasonal variations of gross N mineralization and arginine ammonification activities were very similar, showing rapid responses to rainfall and generally higher activities in wetted soils. As tested in the laboratory, the arginine ammonification activity correlated well with heterotrophic microbial respiration activity (CO₂ production) in soil samples and further displayed a simple, one-component Michaelis-Menten kinetics with a high affinity for arginine (K_m value of 48 µM LJ µM) as determined from non-linear parameter estimation. This indicated that arginine ammonification activity was primarily due to microorganisms, and the activity was also shown to be at a minimum in sterile soil samples. All evidence thus supported that our standard assay of arginine ammonification activity provides a good index of gross N mineralization rates by the microorganisms in soil under in situ conditions.     

贵阳市城区土壤重金属分布特征及污染评价

调查了贵阳市不同功能区表层土壤中重金属含量及其分布特征,以基线为参比值,采用Hakanson潜在生态危害指数法对重金属的潜在生态风险进行了评价。结果表明,贵阳市城区土壤重金属(Hg、Cd、As、Pb、Cr、Cu、Ni、Zn)主要来源于工业、交通以及燃煤等活动,其平均含量分别为0.108、0.320、20.53、22.17、35.71、64.87、48.65、217.90mg/kg,除Cr外,均显著高于相应基线。工矿区土壤中Pb、Zn含量显著高于其他功能区(p0.05)。Hg和Cd是主要的生态危害因子,其污染已达强生态危害水平,其余均显示为轻微生态危害水平;不同功能区土壤重金属污染均已达强生态危害水平,且污染程度依次是:商务区工矿区文教区居民区城市绿地交通区。     

A contemporary overview of silicon availability in agricultural soils

Our current understanding of silicon (Si) availability in agricultural soils is reviewed and knowledge gaps are highlighted. Silicon is a beneficial rather than essential plant nutrient and yield responses to its application have been frequently demonstrated in Si‐accumulator crops such as rice and sugarcane. These crops are typically grown on highly weathered (desilicated) soils where soil solution Si concentrations are low. Increased yields are the result of simultaneous increases in plant tolerance to a wide range of biotic (plant pathogens, insect pests) and abiotic (water shortage, excess salts, metal toxicities) stresses. Traditionally, soil solution Si is viewed as being supplied by dissolution of primary and secondary minerals and buffered by adsorption/desorption of silicate onto Al and Fe hydrous oxide surfaces. In recent years it has become recognized that phytogenic cycling of Si [uptake of Si by plants, formation of phytogenic silica (SiO₂ · nH₂O) mainly in leaves and subsequent return of this silica to soils in plant litter] is the main determinant of soil solution Si concentrations in natural forests and grasslands. Considerable diminution of the phytogenic Si pool in agricultural soils is likely due to regular removal of Si in harvested products. A range of extractants (unbuffered salts, acetate‐based solutions, and acids) can provide valuable information on the Si status of soils and the likelihood of a yield response in rice and sugarcane. The most common Si fertilizers used are industrial byproducts (e.g., blast furnace slag, steel slag, ferromanganous slag, Ca slag). Since agriculture promotes soil desilication and Si is presently being promoted as a broad spectrum plant prophylactic, the future use of Si in agriculture is likely to increase. Aspects that require future research include the role of specific adsorption of silicate onto hydrous oxides, the significance of phytogenic Si in agricultural soils, the extent of loss of phytogenic Si due to crop harvest, the role of hydroxyaluminosilicate formation in fertilized soils, and the effect of soil pH on Si availability.     

斯洛伐克农田土壤环境学指标的研究

The soil environmental index(SEI),which is a four digit code system,represents relatively homogenous spatial unit with specific soil capacity to provide ecological or non-production functions.This work aimed to present information on rating and economic evaluation of SEI,which is a spatial identifier used for expressing heterogeneity of Slovak agricultural soil to support analysis of soil ecological functions.In this study,SEI index expressed the capacity of soil to accumulate water,immobilise the risk elements and substances and transform risk substances(organic pollutants).Partial evaluations of soil capacity to provide above mentioned functions were used to derive final SEI values.Within the agricultural soils of Slovakia there were 493 combinations of soil environmental index.Each index was expressed through rating(point)value and economic value.Average value of Slovak agricultural land to provide selected ecological soil functions was 55.3 points,which corresponded to 35.946 billionper agricultural land or approximately 1.42per square meter.Spatial identification of SEI codes and relevant database were developed in vector form via geographical information systems of Soil Science and Conservation Research Institute,Bratislava.In addition to using the national soil database system,a strategy was presented for evaluating and pricing of soil ecological function,and the development of an soil environmental index.Assessment and evaluation of vitally important soil functions expressed by SEI can significantly contribute to planning and protection of the soil,and can regulate indiscriminate anthropic interventions in land use decisions.     

Heavy metal pollution of the world largest antimony mine-affected agricultural soils in Hunan province (China)

Purpose  

The present work concerns the distribution of ten heavy metals (Sb, As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) in the surrounding agricultural soils of the world largest antimony (Sb) mine in China. The objective is to explore the degree and spatial distribution of heavy metal pollution of the Sb mine-affected agricultural soils. The presented data were compared with metal concentrations in soils from mining and smelting sites in China and other countries.     

酞酸酯在土壤中的环境行为与健康风险研究进展

酞酸酯(PAEs)又称邻苯二甲酸酯,是环境激素类有机化合物,作为增塑剂在塑料、树脂和橡胶制品中的添加量一般为20%~60%。土壤中PAEs的主要来源有农用化学品、污水灌溉和大气沉降。PAEs在土壤中有较强的富集作用,并能通过一系列的环境地球化学过程进入不同的环境介质,引起环境污染和人类健康风险。本文结合国内外土壤PAEs的相关研究成果,综述了我国土壤PAEs的污染现状,分析了PAEs在土壤-大气界面(挥发、沉降)、土壤-植物系统(植物吸收、植物修复)、土壤-水界面下的环境行为(吸附-解吸)及土壤PAEs污染的环境健康风险,并指出国内土壤PAEs研究中存在的不足。研究结果显示,我国土壤环境总体上已遭受不同程度的PAEs污染;同时,土壤PAEs通过不同界面之间的迁移转化过程,也面临较高的生态环境健康风险。提出今后土壤PAEs研究应以区域土壤污染与环境行为为重点,深入研究土壤PAEs的时空传输与演变规律、多介质迁移转化机制和风险削减与修复措施,为保障土壤生态环境与健康提供理论依据。     

农业固体废物分类及其污染风险识别和处理路径

防治农业固体废物污染,对保障农民身体健康,维护农业生态安全,促进农村经济社会可持续发展具有重要意义。在总结农业固体废物内涵和外延的基础上,探讨农业固体废物的主要来源、分类方法和基本特征,按照来源、毒性、组分和形态对农业固体废物进行了分类,剖析来源单一与类型多样的双重性、潜在污染与重要资源的两面性、周年持续与季节波动的复杂性等农业固体废物的基本特征。识别农业种植固体废物、畜禽水产养殖固体废物、废旧农业投入品和农产品初加工固体废物的潜在污染风险。梳理农业固体废物污染防治、处理利用代表性法规政策,分析农业固体废物全链条运营和监管体系,提出\     

生物炭在农业土壤中应用的回顾与展望

Soil degradation, characterized by declines in nutrient status and simultaneous accumulation of pesticide residues, is a major problem affecting agricultural ecosystems. Previous studies indicate that biochar application to soil has promise as a practical method to alleviate these pressures: increasing crop yield and enhancing pesticide degradation. Here, we review the roles of biochar in both chemical and biological promotion of pesticide degradation and the potential benefits of biochar relating to the efficiency of fertilizer use, availability of nutrients, and nutrient exchange. Biochar typically has a high surface area featuring many functional groups, a high cation exchange capacity, and high stability. Major factors that impact on the nutrient retention characteristics of biochar (e.g., feedstock, pyrolysis temperature, and application rate) are also discussed herein. Nonetheless, more studies of the long-term impacts on soil properties from biochar addition are still required before it can be possible to accurately quantify the sustainability of this approach to sequester carbon and restore soil function.