The effect of lindane on terrestrial invertebrates

Electrochemical Reduction and Voltammetric Sensing of Lindane at the Carbon (Glassy and Pencil) Electrodes

In the agricultural field, pesticides are used tremendously to shield our crops from insects, weeds, and diseases. Only a small percentage of pesticides employed reach their intended target, and the remainder passes through the soil, contaminating ground and surface-water supplies, damaging the crop fields, and ultimately harming the crop, including humans and other creatures. Alternative approaches for pesticide measurement have recently received a lot of attention, thanks to the growing interest in the on-site detection of analytes using electrochemical techniques that can replace standard chromatographic procedures. Among all organochlorine pesticides such as gamma-lindane are hazardous, toxic, and omnipresent contaminants in the environment. Here, in this review, we summarize the different ways of the gamma-lindane detection, performing the electrochemical techniques viz cyclic, differential, square wave voltammetry, and amperometry using various bare and surface-modified glassy carbon and pencil carbon electrodes. The analytical performances are reported as the limit of detection 18.8 nM (GCE–AONP–PANI–SWCNT), 37,000 nM (GCE), 38.1 nM (Bare HBPE), 21.3 nM (Nyl-MHBPE); percentage recovery is 103%.

Gentle remediation options for soil with mixed chromium (VI) and lindane pollution: biostimulation, bioaugmentation, phytoremediation and vermiremediation

Gentle Remediation Options (GROs), such as biostimulation, bioaugmentation, phytoremediation and vermiremediation, are cost-effective and environmentally-friendly solutions for soils simultaneously polluted with organic and inorganic compounds. This study assessed the individual and combined effectiveness of GROs in recovering the health of a soil artificially polluted with hexavalent chromium [Cr(VI)] and lindane. A greenhouse experiment was performed using organically-amended vs. non-amended mixed polluted soils. All soils received the following treatments: (i) no treatment; (ii) bioaugmentation with an actinobacteria consortium; (iii) vermiremediation with Eisenia fetida; (iv) phytoremediation with Brassica napus; (v) bioaugmentation + vermiremediation; (vi) bioaugmentation + phytoremediation; and (vii) bioaugmentation + vermiremediation + phytoremediation. Soil health recovery was determined based on Cr(VI) and lindane concentrations, microbial properties and toxicity bioassays with plants and worms. Cr(VI) pollution caused high toxicity, but some GROs were able to partly recover soil health: (i) the organic amendment decreased Cr(VI) concentrations, alleviating toxicity; (ii) the actinobacteria consortium was effective at removing both Cr(VI) and lindane; (iii) B. napus and E. fetida had a positive effect on the removal of pollutants and improved microbial properties. The combination of the organic amendment, B. napus, E. fetida and the actinobacteria consortium was the most effective strategy.

Petroleum hydrocarbon mixture toxicity and a trait-based approach to soil invertebrate species for site-specific risk assessments

Although petroleum hydrocarbons released to the environment typically occur as mixtures, petroleum hydrocarbon remediation guidelines often reflect individual substance toxicity. It is well documented that groups of aliphatic petroleum hydrocarbons act via the same mechanism of action (nonpolar narcosis) and, theoretically, concentration addition mixture toxicity principles apply. To assess this theory, 10 standardized acute and chronic soil invertebrate toxicity tests on a range of organisms (Eisenia fetida, Lumbricus terrestris, Enchytraeus crypticus, Folsomia candida, Oppia nitens, and Hypoaspis aculeifer) were conducted with a refined petroleum hydrocarbon binary mixture. Reference models for concentration addition and independent action were applied to the mixture toxicity data with consideration of synergism, antagonism, and dose level toxicity. Both concentration addition and independent action, without further interactions, provided the best fit with observed response to the mixture. Individual fraction effective concentration values were predicted from optimized, fitted reference models. Concentration addition provided a better estimate than independent action of individual fraction effective concentrations based on comparison with available literature and species trends observed in toxic responses to the mixture. Interspecies differences in standardized laboratory soil invertebrate species responses to petroleum hydrocarbon-contaminated soil was reflected in unique traits. Diets that included soil, large body size, permeable cuticle, low lipid content, lack of ability to molt, and no maternal transfer were traits linked to a sensitive survival response to petroleum hydrocarbon-contaminated soil in laboratory tests. Traits linked to sensitive reproduction response in organisms tested were long life span and small clutch size. By deriving single-fraction toxicity endpoints considerate of mixtures, we can reduce the resources and time required to conduct site-specific risk assessments for the protection of a soil organism's exposure pathway. Environ Toxicol Chem 2018;37:2222-2234. © 2018 SETAC.

Biochar alleviates the toxicity of imidacloprid and silver nanoparticles (AgNPs) to Enchytraeus albidus (Oligochaeta)

The present study investigated the use of biochar for the alleviation of the toxic effects of a nanosilver colloidal dispersion and a chloronicotinyl insecticide. The survival and reproduction of the potworm Enchytraeus albidus were assessed after exposure to imidacloprid and silver nanoparticles (AgNPs). E. albidus was exposed to 0, 25, 50, 100, 200, and 400 mg imidacloprid/kg and 0, 5, 25, 125, and 625 mg Ag/kg for 21 days in 10% biochar amended and non-biochar amended OECD artificial soil. In both exposure substrates, the effects of imidacloprid on survival were significant in the two highest treatments (p < 0.01). No biochar effect was observed as survival was statistically similar in both soils after exposure to imidacloprid. In the case of AgNPs, significant mortality was only observed in the highest AgNP treatments in both the amended and non-amended soils (p < 0.05). Nevertheless, statistically greater survival occurred in the biochar-amended treatment (p < 0.05). Reproduction results showed a more pronounced biochar effect with an EC₅₀ = 22.27 mg imidacloprid/kg in the non-amended soil and a higher EC₅₀ = 46.23 mg imidacloprid/kg in the biochar-amended soil. This indicated a 2-fold decrease in imidacloprid toxicity due to biochar amendment. A similar observation was made in the case of AgNPs where a reproduction EC₅₀ = 166.70 mg Ag/kg soil in the non-amended soil increased to an EC₅₀ > 625 mg Ag/kg soil (the highest AgNP treatment) in the amended soil. This indicated at least a 3.7-fold decrease in AgNPs toxicity due to biochar amendment. Although more studies may be needed to optimize the easing effects of biochar on the toxicity of these chemicals, the present results show that biochar could be useful for the alleviation of the toxic effects of imidacloprid and silver nanoparticles in the soil.

Ecotoxicological assessment of soils polluted with chemical waste from lindane production: Use of bacterial communities and earthworms as bioremediation tools

An ecotoxicological survey of soils that were polluted with wastes from lindane (γ-HCH) production assessed the effects of organochlorine compounds on the metabolism of microbial communities and the toxicity of these compounds to a native earthworm (Allolobophora chlorotica). Furthermore, the bioremediation role of earthworms as facilitators of soil washing and the microbial degradation of these organic pollutants were also studied. Soil samples that presented the highest concentrations of ε-HCH, 2,4,6-trichlorophenol, pentachlorobenzene and γ-HCH were extremely toxic to earthworms in the short term, causing the death of almost half of the population. In addition, these soils inhibited the heterotrophic metabolic activity of the microbial community. These highly polluted samples also presented substances that were able to activate cellular detoxification mechanisms (measured as EROD and BFCOD activities), as well as compounds that were able to cause endocrine disruption. A few days of earthworm activity increased the extractability of HCH isomers (e.g., γ-HCH), facilitating the biodegradation of organochlorine compounds and reducing the intensity of endocrine disruption in soils that had low or medium contamination levels.

Effects of metals on earthworm life cycles: a review

Earthworms are abundant and ecologically very important organisms in the soil ecosystem. Impacts by pollutants on earthworm communities greatly influence the fertility of the terrestrial environment. In ecotoxicology, earthworms are good indicators of metal pollution. The observed median lethal concentrations (LC50) and the effective concentrations that cause 50% reduction of earthworm growth and reproduction (EC50) are referred to as toxicity concentrations or endpoints. In addition, the 'no observed effective concentration' (NOEC) is the estimation of the toxicity of metals on earthworms expressed as the highest concentration tested that does not show effects on growth and reproduction compared to controls. This article reviews the ecotoxicological parameters of LC50, EC50 and NOEC of a set of worms exposed to a number of metals in various tested media. In addition, this article reviews metal accumulation and the influences of soil characteristics on metal accumulation in earthworms. Morphological and behavioural responses are often used in earthworm toxicity studies. Therefore, earthworm responses due to metal toxicity are also discussed in this article.

Antioxidant and neurotoxicity markers in the model organism Enchytraeus albidus (Oligochaeta): mechanisms of response to atrazine, dimethoate and carbendazim

The present study aimed to investigate the effects of dimethoate, atrazine and carbendazim on the antioxidant defences and neuronal function of the soil organism Enchytraeus albidus. Effects were studied at concentrations known to affect their reproduction (EC20, EC50 and EC90) and along time (2, 4, 8, 14 and 21 days). In general, responses were more pronounced at periods of exposure longer than 8 days and at the highest concentrations. Multivariate statistics (RDA-PRC) clearly displayed that exposure duration had an effect itself, biomarkers' responses showed interaction for all pesticides and catalase scored consistently high, indicating its relevancy in the group of measured markers. Univariate analysis indicated oxidative stress for all pesticides and atrazine induced oxidative damage in lipids. Atrazine seems to be effectively metabolized by GST of the biotransformation system, as its activity significantly increased after exposure to this pesticide. Dimethoate caused ChE inhibition, indicating an impairment of the neuronal function. Carbendazim impaired the antioxidant system, but no oxidative damage was observed, along with any effects on the ChE activity. The integrated biomarker response analysis was performed but we suggest modifications due to limiting artefacts.

The response of soil organism communities to the application of the insecticide lindane in terrestrial model ecosystems

The EU plant protection regulation 1107/2009/EC defines the requirements for active ingredients to be approved, specifically including the assessment of effects on biodiversity and ecosystems. According to that, semi-field methods are expected to be more important in the near future. Therefore, a higher-tier experiment suitable to assess the risk for soil organisms was conducted to further develop the TME (terrestrial model ecosystems) methodology in a dose-response design with the persistent insecticidal model compound lindane (gamma-HCH). The effects of lindane on soil communities such as collembolans, oribatid mites, nematodes, soil fungi and plant biomass were determined in 42 TME. Intact TME-soil cores (diameter 300 mm, height 400 mm) from undisturbed grassland were stored outdoor under natural climatic conditions. Lindane was applied in five concentrations between 0.032 mg active ingredients (ai)/kg dry soil and 3.2 mg ai/kg dry weight soil, six-fold replicated each. Twelve TME served as untreated controls. Abundance and community structures of oribatids, collembolans, enchytraeids, nematodes and fungi were recorded. Oribatid mites' community responded 3 months after treatment, although they were not significantly affected by the overall treatment regimen. Collembolans in total and species-specific abundance as well as the community endpoints (principal response curves, diversity measures) were adversely affected by moderate dosages of lindane. Effects were transient between 3 and 5 months after treatment with a recovery within 1 year. No significant effects could be detected for enchytraeids, nematodes and fungi. The study design and the obtained results allow for calculations of no observed effect concentrations below the highest treatment level for populations and for soil communities as defined entities, as well as effective concentrations. The paper discusses the limits of effect detection in the light of achievable coefficients of variation and by means of minimum detectable differences. Outdoor TME are useful to analyze and assess functional and structural endpoints in soil organisms' communities and their possible recovery after pesticide treatment within 1 year.

Fate and bioavailability of ¹⁴C-pyrene and ¹⁴C-lindane in sterile natural and artificial soils and the influence of aging

Soil organic matter is used to extrapolate the toxicity and bioavailability of organic pollutants between different soils. However, it has been shown that other factors such as microbial activity are crucial. The aim of this study was to investigate if sterilization can reduce differences in the fate and bioavailability of organic pollutants between different soils. Three natural soils with increasing total organic carbon (TOC) content were collected and three artificial soils were prepared to obtain similar TOCs. Soils were sterilized and spiked with (14)C-pyrene and (14)C-lindane. Total (14)C radioactivity, HPCD extractability, and bioaccumulation in Eisenia fetida were measured over 56 days. When compared to non-sterile soils, differences between the natural and artificial soils and the influence of soil-contaminant contact time were generally reduced in the sterile soils (especially with middle TOC). The results indicate the possibility of using sterile soils as "the worst case scenario" in soil ecotoxicity studies.

Assessing single and joint effects of chemicals on the survival and reproduction of Folsomia candida (Collembola) in soil

Chemicals are often found in the environment as complex mixtures. There has been a large effort in the last decade to assess the combined effect of chemicals, using the conceptual models of Concentration Addition and Independent Action, but also including synergistic, antagonistic, dose-level and dose-ratio dependent deviations from these models. In the present study, single and mixture toxicity of atrazine, dimethoate, lindane, zinc and cadmium were studied in Folsomia candida, assessing survival and reproduction. Different response patterns were observed for the different endpoints and synergistic patterns were observed when pesticides were present. Compared with the previously tested Enchytraeus albidus and Porcellionides pruinosus, the mixture toxicity pattern for F. candida was species specific. The present study highlights the importance of studying toxicity of chemicals mixtures due to the observed potentiation of effects and confirms that for an adequate ecologically relevant risk assessment different organisms and endpoints should be included.

A comparison of POPs bioaccumulation in Eisenia fetida in natural and artificial soils and the effects of aging

The close relationship between soil organic matter and the bioavailability of POPs in soils suggests the possibility of using it for the extrapolation between different soils. The aim of this study was to prove that TOC content is not a single factor affecting the bioavailability of POPs and that TOC based extrapolation might be incorrect, especially when comparing natural and artificial soils. Three natural soils with increasing TOC and three artificial soils with TOC comparable to these natural soils were spiked with phenanthrene, pyrene, lindane, p,p'-DDT, and PCB 153 and studied after 0, 14, 28, and 56 days. At each sampling point, total soil concentration and bioaccumulation in earthworms Eisenia fetida were measured. The results showed different behavior and bioavailability of POPs in natural and artificial soils and apparent effects of aging on these differences. Hence, direct TOC based extrapolation between various soils seems to be limited.

Outdoor Terrestrial Model Ecosystems are suitable to detect pesticide effects on soil fauna: design and method development

Terrestrial Model Ecosystems (TME) were developed as one higher-tier option to detect and assess effects of pesticides on soil communities in a 1 year study using lindane (gamma-HCH) as a persistent and toxic reference pesticide. TME contained intact soil cores (diameter 300 mm, height 400 mm) including indigenous soil communities of undisturbed grassland. Forty units were placed outdoors between spring 2005 and 2006. The TME experiment was designed to provide data that fulfill the requirements of the revised European regulation on plant protection products (regulation 1107/2009/EEC replacing guideline 91/414/EC) with a focus on structural endpoints such as soil organisms and their community structure in case higher-tier evaluation is triggered. The key objective was to evaluate the dynamics and stability of species-diverse microarthropod communities of undisturbed grassland over at least 1 year after application. In grassland soils, less selection pressure towards insensitive species compared to arable land was presumed. Sufficient numbers of organisms and numerous TME replicates ensured that a statistical evaluation could be performed to estimate the sensitivity of the organisms upon application of lindane applied at high rates of 7.5 and 75 kg ai/ha. The application rates resulted in nominal concentrations of 10 and 100 mg ai/kg dry soil referred to the top 5 cm soil layer of 10 TME each; 20 untreated TME served as controls and were used to study the natural dynamics and the variability of populations under field conditions. Results showed that the grassland from which the soil cores were sampled contained communities of soil organisms marked by typical diversity of improved grassland. Lindane applied at excessive rates caused clear dose-related and long-lasting effects on the communities of microarthropods. On the contrary, lumbricids, the total feeding activity (bait lamina) and the growth of plant biomass were not affected up to 1 year after application. Based on the results of this study using a toxic reference insecticide, the methodology seems to be suitable for use in the regulatory context of the assessment of pesticides once protection goals, data requirements and the conceptual framework are defined.

Can avoidance in Enchytraeus albidus be used as a screening parameter for pesticides testing?

Enchytraeids are important inhabitants of a wide variety of soil types and suitable test organisms for environmental risk assessment through the determination of effects on survival and reproduction. In this study, the effect of pesticides with different modes of action is assessed in the standard test species Enchytraeus albidus. Main goals were: (a) to test the toxicity of a range of pesticides to E. albidus in a natural soil (LUFA 2.2), (b) to assess whether avoidance gave a prediction of effects on the survival and reproduction, and (c) to investigate if the organisms' response to different toxics can be grouped into the respective chemical classes. Pesticides selected were the: (1) herbicides: phenmedipham and atrazine; (2) fungicides: carbendazim and pentachlorophenol; and (3) insecticides: dimethoate and lindane. All tested pesticides caused effects in the survival and reproduction of E. albidus and the compounds that showed a higher toxicity were carbendazim, dimethoate and atrazine. The effect concentrations were not chemical class dependent. In general, survival and reproduction showed similar response patterns. Avoidance behaviour showed trends of response similar to these other measured endpoints, but was less sensitive and more variable (data from a previous study). It was not possible to establish a clear correlation between survival, reproduction and avoidance endpoints. From an ecological point of view, avoidance tests are relevant but due to lower sensitivity and higher variability it is recommended that the enchytraeid avoidance test should not be used for risk assessment purposes.

Bioavailability of xenobiotics in the soil environment

It is often presumed that all chemicals in soil are available to microorganisms, plant roots, and soil fauna via dermal exposure. Subsequent bioaccumulation through the food chain may then result in exposure to higher organisms. Using the presumption of total availability, national governments reduce environmental threshold levels of regulated chemicals by increasing guideline safety margins. However, evidence shows that chemical residues in the soil environment are not always bioavailable. Hence, actual chemical exposure levels of biota are much less than concentrations present in soil would suggest. Because "bioavailability" conveys meaning that combines implications of chemical sol persistency, efficacy, and toxicity, insights on the magnitude of a chemicals soil bioavailability is valuable. however, soil bioavailability of chemicals is a complex topic, and is affected by chemical properties, soil properties, species exposed, climate, and interaction processes. In this review, the state-of-art scientific basis for bioavailability is addressed. Key points covered include: definition, factors affecting bioavailability, equations governing key transport and distributive kinetics, and primary methods for estimating bioavailability. Primary transport mechanisms in living organisms, critical to an understanding of bioavailability, also presage the review. Transport of lipophilic chemicals occurs mainly by passive diffusion for all microorganisms, plants, and soil fauna. Therefore, the distribution of a chemical between organisms and soil (bioavailable proportion) follows partition equilibrium theory. However, a chemical's bioavailability does not always follow partition equilibrium theory because of other interactions with soil, such as soil sorption, hysteretic desorption, effects of surfactants in pore water, formation of "bound residue", etc. Bioassays for estimating chemical bioavailability have been introduced with several targeted endpoints: microbial degradation, uptake by higher plants and soil fauna, and toxicity to organisms. However, there bioassays are often time consuming and laborious. Thus, mild extraction methods have been employed to estimate bioavailability of chemicals. Mild methods include sequential extraction using alcohols, hexane/water, supercritical fluids (carbon dioxide), aqueous hydroxypropyl-beta-cyclodextrin extraction, polymeric TENAX beads extraction, and poly(dimethylsiloxane)-coated solid-phase microextraction. It should be noted that mild extraction methods may predict bioavailability at the moment when measurements are carried out, but not the changes in bioavailability that may occur over time. Simulation models are needed to estimate better bioavailability as a function of exposure time. In the past, models have progressed significantly by addressing each group of organisms separately: microbial degradation, plant uptake via evapotranspiration processes, and uptake of soil fauna in their habitat. This approach has been used primarily because of wide differences in the physiology and behaviors of such disparate organisms. However, improvement of models is badly needed, Particularly to describe uptake processes by plant and animals that impinge on bioavailability. Although models are required to describe all important factors that may affect chemical bioavailability to individual organisms over time (e.g., sorption/desorption to soil/sediment, volatilization, dissolution, aging, "bound residue" formation, biodegradation, etc.), these models should be simplified, when possible, to limit the number of parameters to the practical minimum. Although significant scientific progress has been made in understanding the complexities in specific methodologies dedicated to determining bioavailability, no method has yet emerged to characterized bioavailability across a wide range of chemicals, organisms, and soils/sediments. The primary aim in studying bioavailability is to define options for addressing bioremediation or environmental toxicity (risk assessment), and that is unlikely to change. Because of its importance in estimating research is needed to more comprehensively address the key environmental issue of "bioavailability of chemicals in soil/sediment."

Assessing joint toxicity of chemicals in Enchytraeus albidus (Enchytraeidae) and Porcellionides pruinosus (Isopoda) using avoidance behaviour as an endpoint

Contamination problems are often characterized by complex mixtures of chemicals. There are two conceptual models usually used to evaluate patterns of mixture toxicity: Concentration Addition (CA) and Independent Action (IA). Deviations from these models as synergism, antagonism and dose dependency also occur. In the present study, single and mixture toxicity of atrazine, dimethoate, lindane, zinc and cadmium were tested in Porcellionides pruinosus and Enchytraeus albidus, using avoidance as test parameter. For both species patterns of antagonism were found when exposed to dimethoate and atrazine, synergism for lindane and dimethoate exposures (with the exception of lower doses in the isopod case study) and concentration addition for cadmium and zinc occurred, while the exposure to cadmium and dimethoate showed dissimilar patterns. This study highlights the importance of dose dependencies when testing chemical mixtures and that avoidance tests can also be used to asses the effects of mixture toxicity.

Validation of avoidance assays for the screening assessment of soils under different anthropogenic disturbances

A chemical characterization of the soil compartment per se does not supply any information about the synergistic/antagonistic effects of mixtures of chemicals, resulting in an under- or overestimation of the risks. Therefore the existence of rapid and ecologically relevant toxicity assays becomes of paramount importance, allowing the evaluation of invertebrate's behavioural parameters with equal consequences in terms of functionality of the edaphic community. The aim of this study was to evaluate the sensitivity of avoidance assays, with the earthworm Eisenia andrei, in discriminating natural soils under different anthropogenic disturbances. Although earthworms were able to discriminate soils with similar contamination, it is nonetheless questionable whether the preference for some soils is determined by the reduced bioavailability of contaminants, the great affinity of the species for organic matter-rich soils, or the inability of chemoreceptors to detect some contaminants from complex environmental mixtures, usually present in natural contaminated soils.

Fate and behaviour of phenanthrene in the natural and artificial soils

OECD artificial soil has been used routinely as a standardized substrate for soil toxicity tests. However, can be the fate, behaviour and effects of contaminants in artificial soil extrapolated to natural soils? The aim of our study was to verify this hypothesis by comparing the loss, extraction, and bioavailability of phenanthrene in three artificial and three natural soils of comparable organic carbon content. Soils were spiked with 14C-phenanthrene and total 14C-activity change, the fractions extracted by dichloromethane, 70% ethanol, and hydroxypropyl-beta-cyclodextrin, the fraction mineralized by Pseudomonas sp., and taken up by Enchytraeus albidus were measured after 1, 14, 42, and 84 d aging. The loss, extraction, biodegradation and uptake were several times lower in the artificial than natural soils and these differences increased with increasing soil-phenanthrene contact time. These results imply that artificial soil should be used cautiously for the prediction of fate and behaviour in natural soils.

Derivation of soil values for the path 'soil-soil organisms' for metals and selected organic compounds using species sensitivity distributions

BACKGROUND, AIMS AND SCOPE

According to the German Federal Soil Protection Act, the natural function of soil as a habitat for human beings, animals, plants and soil organisms is, among other things, to be protected by deriving soil values for important chemicals regarding their amounts in the environment, their persistence and/or their toxicity. This contribution presents the results of the mathematical derivation of such values for nine metals and ten organic substances from soil ecotoxicological effect values available in the literature for microbial processes, plants and soil invertebrates.

MATERIAL AND METHODS

Ecotoxicological data were mostly extracted from published papers and reports and had to originate from valid studies that were performed according to internationally standardised guidelines (e.g. ISO) or were otherwise well documented, plausible and performed according to accepted laboratory practice. As test results, both structural (i.e., effects on mortality, growth or reproduction) and functional (i.e., effects on microbial activity or organic matter breakdown) parameters were included. The derivation of soil values was performed using the distribution based extrapolation model (DIBAEX) and EC(50)s (Effective Concentration) as input data.

RESULTS

For 19 compounds, soil values could be calculated. In 18 of these 19 cases clear laboratory ecotoxicological effects (i.e., EC50 values) below the calculated soil value have been found in the literature.

DISCUSSION

In those few cases where a comparison with field studies is possible, effects have been observed in the same order of magnitude as the calculated soil values. A comparison with other similar approaches confirmed the plausibility of the calculated values.

CONCLUSIONS

The DIBAEX-method is a feasible and widely accepted method for deriving soil values from ecotoxicological input data. Data availability was already satisfactory for some substances, but other substances, especially organics, were only poorly covered. The soil values presented here were based on EC50 input data. However, depending on the protection level aimed at by using soil values in legislation, it might be appropriate to use other input data such as NOECs in the derivation process.

RECOMMENDATIONS AND PERSPECTIVES

It is recommended to generate an appropriate number of data for further relevant substances by means of a test battery or multi-species approaches such as terrestrial model ecosystems. These tests should also consider the influence of the bioavailability of substances. A final recommendation for legally binding soil values demands a plausibility check of the mathematically derived values. This should include a comparison with natural background concentrations, soil values for other pathways and soil values used in legislation of other countries. Finally, expert judgement always has to be considered.

The effect of tributyltin-oxide on earthworms, springtails, and plants in artificial and natural soils

Chemical bioavailability in Organisation for Economic Co-operation and Development (OECD) artificial soil can contrast with bioavailability in natural soils and produce ecotoxicologic benchmarks that are not representative of species' exposure conditions in the field. Initially, reproduction and growth of earthworm and Collembolan species, and early seedling growth of a dicotyledonous plant species, in nine natural soils (with a wide range of physicochemical properties) and in OECD soil were evaluated. Soils that supported reproduction and growth of the test species were then used to investigate the toxicity of tributyltin-oxide (TBT-O). Natural soils caused greater toxicity of TBT-O to earthworms (EC(50) values varied from 0.5 to 4.7 mg/kg soil dry weight [dw]) compared with toxicity in OECD soil (EC(50) = 13.4 mg/kg dw). Collembolans were less sensitive to TBT-O than earthworms in natural soils, with EC(50) values ranging from 23.4 to 177.8 mg/kg dw. In contrast, the toxicity of TBT-O to collembolans in OECD soil (EC(50) = 104.0 mg/kg dw) was within the range of EC(50) values in natural soils. Phytotoxicity tests revealed even greater difference between the effects in natural soils (EC(50) values ranged from 10.7 to 189.2 mg/kg dw) and in OECD soil (EC(50) = 535.5 mg/kg dw) compared with results of the earthworm tests. Studies also showed that EC(50) values were a more robust end point compared with EC(10) values based on comparisons of coefficients of variation. These results show that toxicity testing should include studies with natural soils in addition to OECD soil to better reflect exposure conditions in the field.

Terrestrial avoidance behaviour tests as screening tool to assess soil contamination

To assess soil quality and risk assessment, bioassays can be useful tools to gauge the potential toxicity of contaminants focusing on their bioavailable fraction. A rapid and sublethal avoidance behaviour test was used as a screening tool with the earthworm Eisenia andrei and the isopod Porcellionides pruinosus, where organisms were exposed during 48 h to several chemicals (lindane, dimethoate and copper sulphate, for isopods and carbendazim, benomyl, dimethoate and copper sulphate for earthworms). Both species were also exposed to soils from an abandoned mine. For all bioassays a statistical approach was used to derive EC50 values. Isopods and earthworms were able to perceive the presence of toxic compounds and escaping from contaminated to clean soil. Furthermore the behaviour parameter was equally or more sensitive then other sublethal parameters (e.g. reproduction or growth), expressing the advantages of Avoidance Behaviour Tests as screening tools in ERA.

Folsomia candida (Collembola): a "standard" soil arthropod

Folsomia candida Willem 1902, a member of the order Collembola (colloquially called springtails), is a common and widespread arthropod that occurs in soils throughout the world. The species is parthenogenetic and is easy to maintain in the laboratory on a diet of granulated dry yeast. F. candida has been used as a "standard" test organism for more than 40 years for estimating the effects of pesticides and environmental pollutants on nontarget soil arthropods. However, it has also been employed as a model for the investigation of numerous other phenomena such as cold tolerance, quality as a prey item, and effects of microarthropod grazing on pathogenic fungi and mycorrhizae of plant roots. In this comprehensive review, aspects of the life history, ecology, and ecotoxicology of F. candida are covered. We focus on the recent literature, especially studies that have examined the effects of soil pollutants on reproduction in F. candida using the protocol published by the International Standards Organization in 1999.

Application of an artificial sea salt solution to determine acute toxicity of herbicides to Proisotoma minuta (Collembola)

The acute toxicity test is described in this experiment where the Collembola species Proisotoma minuta was exposed to herbicides in an artificial sea salt solution for seven days. The salt solution did not prohibit the insects' reproduction system. The seven day LD50 values for trifluralin, pendimethalin, metolachlor, prometryn, paraquat, atrazine, fluometuron, and diuron were 3.48, 10.4, 12.4, 13.0, 23.1, 33.4, 250, and 711 mg L(-1), respectively. A good correlation between toxicity of the compounds and their lipophilicity and vapor pressure was recorded in this study.