Bioassays for the ecotoxicological and genotoxicological assessment of contaminated soils (results of a round robin test)

For the assessment of contaminated or remediated soils, in addition to chemical analyses, ecotoxicological tests are performed which focus on the retention function of soils (determined by tests with aqueous soil extracts) and on the habitat function (determined by tests with soil). While numerous standardized test guidelines exist to investigate effects by chemical substances, respective test procedures for soil assessments are lacking. To close this gap, a round robin test was performed to support standardization. Four contaminated soils were tested using a total of fifteen test systems including ecotoxicological and genotoxicological tests with soil extracts and soil. The results obtained from the tests with soil extracts are presented in this article.     

Proposal of a testing strategy and assessment criteria for the ecotoxicological assessment of soil or soil materials

Background and Scope  Information on a potential contamination of soils or soil materials are derived by chemical analysis which takes place specifically for a given substance. For a comprehensive assessment, information on the bioavailable and mobile contaminant fraction, including all metabolites, is desirable. During the last years several research projects were initiated in Germany, to supplement the chemical analyses and to elaborate a suitable testing strategy. The main goal of this contribution is to elucidate the results of these research projects and to summarize the test strategy, which is recommended based on these results. Results and Conclusion  Ecotoxicological tests, which are standardized for the assessment of chemicals, were regarded as a suitable starting basis for a cost effective, pragmatic approach. Aquatic tests (testing of aqueous soil extracts) focus on the retention function of soils and terrestrial tests (testing of soil) on the habitat function. Suitable reference systems for the terrestrial tests and assessment criteria for both test types (terrestrial and aquatic) were elaborated. On the basis of a round robin test and a laboratory comparison test, a minimal test battery was established. This minimal test battery can be supplemented by further tests if more or specific information is required. Outlook  The recommendations should encourage the discussion regarding the application of biological methods for the assessment of soil quality. Such an assessment is or at least can be required by soil protection laws which have been adopted in some European countries within the last years.     

Validation of Microplate Bioassays for the Assessment of Contaminated and Remediated Sites

Background, Goal and Scope  Bioassays are frequently used to investigate the water extractable ecotoxicological and genotoxicological potential of contaminated soil samples. A laboratory intercomparison study was performed for validation of miniaturised biological test systems for the assessment of contaminated and remediated sites. The successful performance of this study resulted in an optimisation of microplate assays with respect to the testing of chemicals and environmental samples. Methods  For this purpose, miniaturised bioassays were chosen, which, because of their stage of development, are suitable for routine application in the characterisation of the water extractable ecotoxicological and genotoxicological potential of soils. These ecotoxicological and genotoxicological assays were performed with contaminated soil samples by three institutions at the same time. Results and Discussion  The toxicological assessment of the contaminated and remediated soil samples using LID-values, as a rule, was highly uniform. Some minor deviations could, for the most part, be explained by the heterogeneity of the soil samples and, to a lesser extent, by methodical aspects. The difference in sensitivity towards contaminants of the two bacteria Vibrio fischeri and Pseudomonas putida was pointed out. In the algae test with Desmodesmus subspicatus, the influence of the highest sample concentrations on the growth controls became obvious. It was recommended to modify the experimental setup of the microtitration plate, i.e. to place growth controls located next to both the lowest and the highest dilution steps of the sample. The Ames-test did in some cases provide new information on the genotoxicity of the samples, but is not considered useful in a test battery for the evaluation of the genotoxic potential because of its great expense in time and work. Conclusions  The investigations in this laboratory-intercomparison study for the assessment of the water extractable toxic potential of soil samples show that different bioassays are needed, which, in contrast to chemical-analytical methods, can detect the complete effects of all present pollutants in contaminated and remediated soils and solid substrates path-specifically. Recommendations and Outlook  If the recommended modifications for the performance of the bacterial and algae growth inhibition assays on microplates are taken into consideration, these tests can substitute the tests performed on a macro scale. The usefulness of the umu-test and the NM2009-test for the investigation of the genotoxic potential has been proven. Although the tests performed on microplates require much lower sample amounts, it is recommended that sample amounts be eluted in accordance with current guidelines to ensure representativity of the sample. Further work should focus on toxicity identification studies in the future by combining chemical and toxicological analyses.     

Earthworm avoidance test for soil assessments

For ecotoxicological assessments of contaminated or remediated soils pointing to the habitat function of soils for biocenoses, standardized tests with earthworms (acute test, reproduction test) are available among others. Tests used for routine applications should be sensitive and indicate impacts on test organisms after short test periods. The usually applied earthworm tests do not satisfactorily fulfil these criteria. Therefore, in the present work, a behavioural test with earthworms (test criterion: avoidance) was investigated in detail using uncontaminated, artificially contaminated and originally contaminated soils. It was demonstrated that the avoidance behaviour is primarily determined by pollutants, and not by chemical-physical soil properties. The sensitivity of the presented test reaches the sensitivity of established tests. For waste sites, a considerably higher sensitivity was determined. An avoidance behaviour of at least 80% of the worms leaving the soil to be assessed is proposed as a criterion for toxicity.     

Experiences with Novel Approaches in Earthworm Testing Alternatives (7 pp)

Goal, Scope and Background   The earthworm avoidance test is a sensitive screening test. Currently, two test designs, a two-chamber system and a six-chamber system, are under standardization. In the scope of the present study, the two test systems are compared. To assess the results, two procedures are applied, which are based on a threshold value and a statistical method. Moreover, the sensitivity of the avoidance test is compared with the sensitivity of the reproduction test. Methods   The avoidance behaviour of E. fetida towards five chemicals (Cd, Cu, PCP, TBT, TNT) was tested in a sandy and a loamy soil. The ecotoxicological test was performed according to the draft guideline ISO/DIS 17512-1. The results were compared with the number of offspring determined in the reproduction test carried out according to ISO 11268-2. Results and Discussion   The results demonstrate that the avoidance behaviour towards organic chemicals and heavy metals is a suitable screening method showing first tendencies of a chemical's effects on the habitat function of soils. Effects caused by chemical substances become visible at low concentrations and within short test periods. The sensitivity of the reproduction test and the avoidance test is principally comparable; in some cases, the avoidance test showed more sensitive reactions. The dose-response-relationships were more pronounced in the two-chamber test than in the six-chamber-system. Recommendation and Outlook   The two-chamber-system proved to be more feasible than the six-chamber-system. As the sensitivity of the avoidance test and the reproduction test is comparable, the avoidance test can be considered as a suitable screening test as well. A possible field of application may be the selection of soil samples for which the reproduction assay seems necessary. To assess contaminated or remediated soils, the earthworm reproduction test is recommended as an indicator for the habitat function of the soils. To reduce costs, the labour intensive reproduction test could be largely replaced by the avoidance test in performing the earth-worm reproduction test only for relevant samples. Before the Draft International Standard of the guideline will be adopted as an ISO Guideline, there will be sufficient time left to gain further international experience required to finalize the method.     

Biological tools for the assessment of contaminated land: applied soil ecotoxicology

Abstract. Chemical analysis alone is inadequate for comprehensively assessing the impact of soil pollution on biota. The term bioavailability can only be applied in a context specific to a target biological receptor or a proven chemical surrogate. Integration of biological and chemical data can often yield significant advances in hazard assessment and act as a suitable baseline for making site-specific risk assessments. Here, the value of biological techniques is discussed and their application described. The relative merit of test selection is considered and the new direction being developed in sublethal assessments. Currently, however, one of the major limitations is the seeming lack of flexibility of many assays in that they are either applicable to agricultural systems or industrial scenarios, but rarely to both. As a consequence, few assays have internationally adopted protocols. The introduction of new methods and the continued improvement and refinement of assays make this area of soil science dynamic and responsive.     

表面活性剂对植物修复有机污染土壤的增效作用及原理

Phytoremediation is becoming a cost-effective technology for the in-situ clean up of sites polluted with hydrophobic organic contaminants （HOCs）. The major factors limiting phytoremediation are the mass transfer, rate of plant uptake, and microbial biodegradation of HOCs. This article discusses the potential of surfactants to enhance desorption, plant uptake, and biodegradation of HOCs in the contaminated sites. Positive effects of surfactants on phytoremediation have been recently observed in greenhouse studies. The presence of some nonionic surfactants including polyoxyethylene sorbltan monooleate （Tween 80） and polyoxyethylene（23）dodecanol （Brij35） at relatively low concentrations resulted in significant positive effects on phytoremediation for pyrene-contaminated soil. However, the anionic surfactant （sodium dodecyl sulfate, SDS） and the cationic surfactant （cetyltrimethylammonium bromide, CTMAB） were not useful because of their phytotoxicity or low efficiency for surfactant-enhanced phytoremediation （SEPR）. The mechanisms of SEPR for HOC-contaminated sites were evaluated by considering experimental observations. In view of concerns about the cost effectiveness and toxicity of surfactants to plants, more research is needed to enhance the use of SEPR technology.     

Critical body residues (CBRs) for ecotoxicological soil quality assessment: copper in earthworms

The term ‘critical body residue’ (CBR) was defined as the lowest observed total body concentration of a contaminant in an organism, which is associated with the occurrence of adverse toxic effects in either individuals or populations of a defined age or stage of development. In this study, internal toxicity thresholds were determined for copper in the clitellated adult stage of earthworms (Lumbricus rubellus and Aporrectodea caliginosa). The objective was to assess the applicability of CBRs as a practical tool in soil quality assessment of contaminated sites and as a means of a sustainable protection of earthworm fauna. Laboratory studies showed that body concentrations of Cu were generally in agreement with the chemically available CaCl₂-extractable fraction in soil, but that there was also some evidence of internal pH-related homeostatic regulation. Toxicological correlates of body Cu concentrations with adverse effects on cocoon production (fecundity) suggested an approximate sublethal internal threshold of about 40 mg kg⁻¹, with mortality occurring at about 60 mg kg⁻¹. Adult L. rubellus sampled from areas with a wide range of metal pollution showed body Cu concentrations with a minimum of 8 mg kg⁻¹ and a maximum of 60 mg kg⁻¹. Beyond this apparent physiological tolerance range, environmental management directed at optimal earthworm population survival may not be sustainable in contaminated fields. Studies of L. rubellus colonizing a metal-contaminated experimental sludge-treated field showed that a reduced rate of colonization can already be associated with an average body Cu concentration of 25 mg kg⁻¹. However, in this particular field situation mixture effects of other metals that were also present in the soil and the occurrence of avoidance behaviour during colonization may have contributed to this low internal toxicity threshold. It is concluded that the CBR approach seems to be a feasible option for use as a tool in a bioavailability-based soil quality assessment, even for essential trace metals like copper, but that further insight may be needed to establish the uncertainty and reliability of the application in environmental quality assessment and decision making.     

Phytoremediation of selenium‐contaminated soils: the efficiency of different cropping systems

Field experiments were conducted at two locations in the seleniferous region of northwestern India from 2001 to 2006 to evaluate the efficiency of four cropping systems in removing Se from contaminated soil containing 2843–4345 μg Se per kg in the surface layer (0–15 cm). Rapeseed (Brassica napus) followed by arhar (Cajanus cajan), sunn hemp (Crotalaria juncea) or cotton (Gossypium arboretum) and wheat (Triticum aestivum) followed by rice (Oryza sativa) were the four cropping systems. The total biomass generated by Brassica‐based systems ranged from 16 to 21 t/ha when harvested at maturity. Corresponding values for a wheat–rice sequence were 22–26 t/ha. Among the different crops at both the experimental sites, the highest Se content was recorded in leaves (157–209 mg/kg), grains (64–201 mg/kg) and stems (42–93 mg/kg) of Brassica and the lowest in the shoots (10–27 mg/kg), grains (5–13 mg/kg) and straw (13–20 mg/kg) of the rice crop. Except for S and P, concentrations of other nutrients (Zn, Cu, Mn and Fe) were not significantly affected by variations in the Se content of plants. Significant correlation coefficients were observed between Se and S (r = 0.838, P ≤ 0.001), Se and P (r = 0.817, P ≤ 0.001) at the peak flowering stage (n = 16), and r = 0.743, P ≤ 0.001 and r = 0.498, P ≤ 0.05, respectively, at the maturity stage (n = 16). Total Se removal through harvested biomass of rapeseed‐based cropping sequences varied from 716 to 1374 g/ha/yr at peak flowering and 736–949 g/ha/yr at the maturity stage. Corresponding values for a wheat–rice system were 435–492 and 370–517 g/ha/yr, respectively. The amount of Se recycled through leaf senescence ranged from 255 to 500 g/ha/yr for Brassica‐based cropping systems. In the wheat–rice system, Se addition through irrigation varied from 170 to 243 g/ha/yr and was three to four times more than that added in Brassica‐based systems. On completion of the phytoremediation experiments at site I, Se removal through harvested biomass at maturity was 1.7–5.1% of total Se in the soil down to a depth of 120 cm and 4.8–13.2% at site II. Analysis showed that Se losses under different crop rotations were 18.5–24.5% at site I and 21–33% at site II of total soil Se. Thus, at both sites 16–20% of total Se lost from the soil was unexplained. Results show that Brassica‐based cropping systems lead to significant reductions in Se capital of contaminated soil over 2–3 years. Although a long‐term commitment is required, adoption of Brassica‐based systems as a regular agricultural practice must lead to sustainable management of seleniferous soils.     

四种不同方法在土壤重金属污染评价中的应用比较

Four assessment methods （two pollution indexes and two fuzzy mathematical models） were employed to investigate the environmental quality of four soils around a ferroalloy plant in Nanjing City. Environmental quality was assessed as class Ⅳ （moderately polluted） for each soil with single-factor index method, and was identified to be classes Ⅳ, Ⅲ （slightly polluted）, Ⅲ, and Ⅲ for soils A, B, C, and D, respectively, with the comprehensive index model. In comparison with the single-factor index method, the comprehensive index model concerned both dominant parameter and average contribution of all factors to the integrated environmental quality. Using the two fuzzy mathematical methods （single-factor deciding and weighted average models）, the environmental risks were determined to be classes Ⅳ, Ⅲ, Ⅱ （clean）, and Ⅱ for soils A, B, C, and D, respectively. However, divergence of the membership degree to each pollution class still occurred between the two methods. In fuzzy mathematical methods, membership functions were used to describe the limits between different pollution degrees, and different weights were allocated for the factors according to pollution contribution. Introduction of membership degree and weight of each factor to fuzzy mathematical models made the methods more reasonable in the field of environmental risk assessment.     

典型滴滴涕废弃生产场地污染土壤的人体健康风险评估研究

对我国典型滴滴涕(DDT)废弃生产场地的疑似重污染区进行环境调查、污染土壤人体健康风险评估和土壤修复建议目标值计算。结果表明,该场地污水处理池周边的关注污染物主要为p,p’-DDT、p,p’-DDD、p,p’-DDE、1,4-二氯苯、氯仿和氯苯,临近污水处理池北侧和东侧的区域土壤中污染物垂向迁移明显,其他区域土壤污染物主要分布于0～50 cm土层。前5种关注污染物的致癌风险均超过10-6,部分点位p,p’-DDT和氯苯的非致癌危害指数大于1。不确定性分析表明,半挥发性有机物p,p’-DDT、p,p’-DDD和p,p’-DDE经口腔摄入土壤和皮肤接触土壤暴露途径对总风险的贡献率超过98%,挥发性有机物氯苯、1,4-二氯苯和氯仿经吸入室内空气暴露途径对总风险的贡献率高达99%以上。土壤颗粒密度、土壤容重和土壤含水率是敏感参数。p,p’-DDT、p,p’-DDD、p,p’-DDE、氯苯、1,4-二氯苯和氯仿的土壤修复建议目标值分别为5.84、6.19、4.36、36.2、0.55和0.02 mg kg-1。     

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。     

Diffuse reflectance spectroscopy (DRS) for rapid soil testing and soil quality assessment in smallholder farms

Rapid soil testing and soil quality assessment are essential to address soil degradation and low farm incomes in smallholder farms. With the objective of testing diffuse reflectance spectroscopy (DRS) to rapidly assess soil chemical properties, nutrient content and a soil quality index (SQI), samples of surface soil were collected from 1113 smallholder farms in seven districts in Bundelkhand region of Uttar Pradesh, India. A minimum dataset (MDS) approach was followed to estimate SQI using the three chemical parameters of soil pH, electrical conductivity (EC) and soil organic carbon (SOC), and 11 different soil nutrients. Principal component and correlation analyses showed that soil pH, SOC content and three available nutrients − copper (Cu), iron (Fe) and sulphur (S) − may constitute the MDS. Estimated SQI values showed strong positive correlation with crop yields. Results of chemometric modelling showed that the DRS approach could yield the coefficient of determination (R²) values in the validation datasets ranging from 0.79 to 0.94 for exchangeable calcium (Ca) followed by 0.67–0.88 for exchangeable potassium (K), 0.52–0.86 for SOC and 0.53–0.81 for available boron (B) content. Except in one district, the DRS approach could be used to estimate SQI values with R² values in the range of 0.63–0.81; an R² value of 0.71 was obtained in the pooled dataset. We also estimated the three-tier soil test crop response (STCR) ratings to compare DRS and wet chemistry soil testing approaches. Similar STCR ratings were obtained for both these approaches in more than 86% of the samples. Parameters for which both the methods yielded similar ratings in more than 80% of the samples were EC (>98%), pH and exchangeable Ca (>81%) and available B (>89%). With similar ratings, these results suggest that the DRS approach may safely be used for farmers' fields, replacing the traditional wet analysis approach of soil testing.     

有机溶剂对有机氯农药污染场地土壤淋洗修复效用研究

Problems associated with organochlorine pesticide (OCP)-contaminated sites in China have received wide attention. To solve such problems, innovative ex-situ methods of site remediation are urgently needed. We investigated the feasibility of the extraction method with different organic solvents, ethanol, 1-propanol, and three fractions of petroleum ether, using a soil collected from Wujiang (WJ), China, a region with long-term contamination of dichlorodiphenyltrichloroethanes (DDTs). We evaluated different influential factors, including organic solvent concentration, washing time, mixing speed, solution-to-soil ratio, and washing temperature, on the removal of DDTs from the WJ soil. A set of relatively better parameters were selected for extraction with 100 mL L 1 petroleum ether (60-90℃): washing time of 180 min, mixing speed of 100 r min 1 , solution-to-soil ratio of 10:1, and washing temperature of 50℃. These selected parameters were also applied on three other seriously OCP-polluted soils. Results demonstrated their broad-spectrum effectiveness and excellent OCP extraction performance on the contaminated soils with different characteristics.     

Terrestrial Ecotoxicity of Eight Chemicals in a Systematic Approach (7 pp)

Background and Objective   Terrestrial ecotoxicity data are required for many research purposes. The data are derived either from the literature or elaborated by own investigations. As the terrestrial toxicity tests are usually time-consuming and labour intensive, the experiments are performed with a limited number of test organisms and soils. In the context of a project sponsored by CEFIC-LRI (European Chemical Industry Council – Long-Range Research Initiative), EC50-values were systematically elaborated for eight chemicals with a wide range of logKow-values (CdCl2, Trinitrotoluene, 3,4-dichloroaniline, 2,4-dichlorophenol, Tributyltinchloride, Pentachlorophenol, Benzo(a)pyrene, p,p-dichloro-2,2-diphenyl-1,1,1-trichloroethane). The substances were selected covering a broad range of physico-chemical and ecotoxicological properties. As toxicity endpoints, microbial activities, plant germination and growth as well as reproduction of earthworms and collembola were determined. As such systematic investigations are rarely performed and for some substances no data existed, the data pool is made available to the scientific community.Methods   All toxicity tests were conducted on three different soil types (sandy soil, silty soil, loamy soil), according to ISO and OECD guidelines Results, Discussion, Conclusion and Outlook   The different toxicities of the chemicals, the influence of soil properties on bioavailability as well as different sensitivities of test organisms and test parameters are reflected by the EC50-values. The results showed that the EC50-values calculated on the basis of nominal concentrations can significantly vary from EC50-values derived from analytical concentrations for some substances. To avoid false conclusions, this has to be considered especially when concentrations determined in the field are compared with toxicity data obtained from the literature or calculated on the basis of nominal concentrations. Moreover, the results indicate that terrestrial ecotoxicological tests should be accompanied by chemical analyses, to be sure to derive sound EC50-values. As the tests were performed according to international guidelines, the comprehensive data pool relevant for the terrestrial ecotoxicity of eight chemicals is considered to be of great value for further research and discussions dealing with the habitat function of soils.     

A Chronic Plant Test for the Assessment of Contaminated Soils. Part 2: Testing of contaminated soils (10 pp)

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PREAMBLE According to the German Federal Soil Protection Act (BBodSchG 1998), the habitat function of soils must be protected. Despite the fact that in the Federal Soil Protection Ordinance (BBodSchV 1999) it has not been established how this goal can be reached reliably, it is clear that such a biological function can only adequately be assessed using biological test methods. This is especially true when a soil is contaminated by a mixture of often unknown chemicals. In such a case the use of chemical analysis aiming at a small range of known substances is not sufficient and must therefore be supplemented by biological methods. For this reason, several standardised test methods are available (e.g. using earthworms, collembolans or plants; Römbke and Knacker 2003; ISO 2003). Since acute tests are usually not sensitive enough for the assessment of potentially contaminated soils (e.g. Hund-Rinke et al. 2002), chronic tests like the earthworm reproduction tests (ISO 1998) are recommended for this purpose.

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A chronic plant test for the determination of phytotoxicity was missing until quite recently. The term phytotoxicity is understood here as the capacity of a compound or a contaminated soil to cause temporary or long-lasting damage to plants (EPPO 1997). Therefore, the German Ministry for Education and Research sponsored a project (1997 – 1999) in which – based on existing standardised methods – such a chronic plant laboratory test was developed and partly validated (Kalsch and Römbke 2000). The new test can be used for the evaluation of single chemicals (see Part 1 of this mini-series) as well as for the assessment of contaminated or remediated soils (see Part 2 of this mini-series).

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ABSTRACT Background and Scope. A new chronic plant test system which is based on experiences with various acute plant tests (e.g. published by OECD or ISO) and existing North American Plant-Life-Cycle Bioassays was standardised in a project sponsored by the German government. Characteristic properties of the test system, which can be performed either with Brassica rapa (turnip rape) or Avena sativa (oat), are described in Part I of this mini-series.

Methods

This new test was used to assess the effects of natural soil samples contaminated with TNT (2,4,6-Trinitrotoluene) or PAHs (poly-aromatic hydrocarbons). The soils were tested after taken from the field as well as after being remediated. Different control and reference soils were used to evaluate the test results. In addition, they were compared with the results of tests in which either TNT or Pyrene was spiked to field and standard soils (see Part I of this mini-series).

Results

All contaminated soils showed clear effects in the Chronic Plant Test (usually B. rapa was more sensitive than A. sativa). LUFA 2.2 standard soil and OECD artificial soil are well-suited as control and mixture substrates, while reference soils collected at uncontaminated sites were several times phytotoxic. In most of the latter cases, soil properties could be identified as the main cause of these effects (e.g. the pH value). While in general the sensitivity of the reproduction and biomass endpoints did not differ much, it is recommended to measure different endpoints (i.e. biomass and reproduction) due to the different mode-of-action of contaminants. In the case of TNT a good agreement between the results of single chemical tests and tests with TNT-contaminated soils was found (due to the minimal effects of Pyrene the same statement is not possible for PAHs).

Outlook

The results of this work have been used to prepare a draft test guideline, which has recently been standardised by the International Organisation for Standardisation (ISO). Based on these experiences, recommendations are given how this chronic test system could be used as part of a test battery for the assessment of contaminated soils.     

Effect of cellulose and glucose on the proliferation of PCP (pentachlorophenol)-degrading microorganisms in soil suspension

The pesticide pentachlorophenol (PCP) of which application to rice fields was prohibited in Japan after the 1970s is still used as a fungicide for upland crops or timber. In many cases the pesticide dropped into soil is microbially degraded, and microbial degradation of PCP in soil was studied by many authors (Watanabe and Hayashi 1972; Kuwatsuka and Igarashi 1975; Watanabe 1977). The PCP-degrading microorganisms so far isolated are common ones which are not nutritionally fastidious (Watanabe 1973; Suzuki 1983a, b). It is, therefore, plausible that PCP-degradability of the microorganisms is influenced by the presence of some nutrients because, in general, the microorganisms may preferentially use nutrients to pesticides which are biostatic or biocidal to the microorganisms.     

A critical assessment of soil amendments (slaked lime/acidic fertilizer) for the phytomanagement of moderately contaminated shooting range soils

Purpose  

The effects of the addition of an acidic fertilizer solution and/or slaked lime (5.5 g Ca(OH)₂ kg⁻¹) on a slightly acidic shooting range soil (pH 6.1, % organic carbon 5.4) with moderate metal (e.g., 620 mg kg⁻¹ Pb) and metalloid (17 mg kg⁻¹ Sb) concentrations on metal and Sb solubility and plant accumulation were investigated.     

Soil quality and fertility in sustainable agriculture,with a contribution to the biological classification of agricultural soils

Soils and crops are particularly vulnerable to climate change and environmental stresses. In many agrosystems, soil biodiversity and ecosystem services provided by soils are under threat from a range of natural and human drivers. Agricultural soils are often subject to agronomic practices that disrupt soil trophic networks and make soils less productive in the long term. In this scenario, sustainable soil use aimed at improving plant/root status, growth and development plays a crucial role for enhancing the biological capacity of agricultural soils. This commentary paper is divided into the following four main sections: (i) the contentious nature of soil organic matter; (ii) soil biological quality/fertility; (iii) soil classification; and, (iv) which agricultural practices can be defined as sustainable? The published literature was analyzed within a holistic framework, with agrosystems considered as living systems where soil, vegetation, fauna and microorganisms co-evolve and are reciprocally influenced. Ultimately, this article will suggest a better stewardship of agricultural soils as a natural capital.