Abstract: Contaminants in soils can enter food chains through primary producers. Bioavailable contaminants can induce growth, and reproductive or biochemical changes in plants. To evaluate the bioavailability of heavy metals in two soils from Jales mine surroundings, bioassays with the plants Brassica rapa (RCBr) and Avena sativa were performed. Biochemical parameters (protein and malondialdehyde [MDA] content, and catalase and peroxidase activities) were also measured. The soils had different heavy metal contents: JNC soil contained low heavy metal concentrations, whereas JC soil had high heavy metal contents. Results stressed the difference between species sensitivity, with A. sativa showing no toxicity effects when exposed to both soils. On the other hand, B. rapa presented a decrease in growth parameters when exposed to JNC soil and no changes when exposed to JC soil. A Life Cycle Bioassay confirmed this trend for B. rapa exposed to JNC soil, but also evidenced that JC soil was affecting B. rapa in terms of flower and seed pod production. Biochemical assays showed that plants affected by heavy metals also displayed oxidative stress, with an increase in MDA production, reduction of protein content, and reduction of catalase and peroxidase activities. All bioassays revealed that JNC soil, although with a lower heavy metal content, had a higher bioavailable fraction when compared to JC soil, which consequently increased its toxicity to plants.
Abstract: Soil decomposition is mainly dependent on the nature and characteristics of organic matter within the soil, the environmental conditions and the activity of microorganisms and soil fauna. Isopods play an important role in decomposition through litter fragmentation and stimulating and/or ingesting fungi and bacteria. The aim of this study was to jointly evaluate the effect of different food types and the effect of heavy metal contamination of those foods through isopod feeding performance assays. These studies used the terrestrial isopod Porcellionides pruinosus. After feeding with different leaf types for the study on feeding performance, alder leaves were chosen for the contamination experiments. Feeding parameters like consumption, assimilation, egestion and growth ratios were calculated and compared among treatments and food type. Lower quality food decreased isopods performance. Exotic food types were shown to be less preferred than alder or oak leaves. Contaminated food also resulted in a decrease in performance among the feeding parameters studies, although isopods can tolerate in certain cases high amounts of heavy metals. For this reason it is possible that in future this crustacean can be used as bioindicators of soil contamination or in the evaluation of contaminated sites or remediation processes.
Abstract: 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.
Abstract: Soil contamination can be one path for streams and groundwater contamination. As a complement of chemical analysis and total contaminants determination, bioassays can provide information on the bioavailable fraction of chemical compounds, focusing on the retention and habitat function of soils. In this study the evaluation of the toxicity of two soils from the abandoned Jales Mine (Portugal) regarded both functions. The buffer capacity of soils was tested with bioassays carried out using the cladoceran Daphnia magna and the marine bacteria Vibrio fischeri. The habitat function of soils was evaluated with the reproduction bioassay with the collembolan Folsomia candida. The Microtox solid-phase test was performed with V. fischeri using soil as test medium, and soil elutriates were extracted to perform the Microtox basic test, and an immobilization and reproduction bioassay with D. magna. The marine bacteria showed high sensitivity to the soil with low heavy metal content (JNC soil) and to JNC soil elutriates, while the soil with highest heavy metal content (JC soil) or soil elutriates exposure did not cause any toxic effect. In the bioassays with D. magna, organisms showed sensitivity to JNC and also to JC soil elutriates. Both mobilization and reproduction features were inhibited. The bioassay with F. candida did not reflect any influence of the contaminants on their reproduction. Although JNC soil presented lower heavy metal contents, elutriates showed different patterns of contamination when compared to JC soil and elutriates, which indicates different retention and buffer capacities between soils. Results obtained in this study underlined the sensitivity and importance of soil elutriate bioassays with aquatic organisms in the evaluation strategy in soil ERA processes.
Abstract: The effects of carbendazim on substrate induced respiration (SIR), dehydrogenase activity (DHA), phosphatase activity and thymidine incorporation by bacteria were evaluated in an experiment with an open intact Terrestrial Model Ecosystem (TME) and in a simultaneous field-validation study. Experiments were performed on four different European soils in Germany, The Netherlands, United Kingdom and Portugal. Data analysis focused on (i) detecting differences between experiments, especially in control values, (ii) checking similarity in data variability at each treatment level between experiments and (iii) analysing the resemblance of response to the model chemical in both experiments. Results obtained showed that control values from TME experiments were similar to those obtained on the respective field site, in most of the comparisons made for SIR, DHA and thymidine incorporation. Phosphatase activity revealed more differences, but values of both experiments had the same order of magnitude. At least part of the variation could be explained from the correlation of the microbial parameters with soil moisture content. Comparisons on data variability also revealed the absence of significant differences between experiments in all parameters in most cases, indicating that TMEs were able to represent the spatial variability found in the field. Effects of carbendazim, when occurring, were observed at treatment levels exceeding the highest recommended application rate of 0.36 kg a.i./ha. Effects on SIR and DHA were observed early in time, but effects on phosphatase activity and thymidine incorporation rate were found 8 or 16 weeks after chemical application. These effects were mild, and rarely a 50% inhibition on any of these parameters was seen at carbendazim dosages up to 87.5 kg a.i./ha. The response to the model chemical in TMEs and field plots was similar in most cases. These results give promising prospects for the use of TMEs as an integrative tool in higher tier levels of different assessment schemes.
Abstract: An achievable way to evaluate the bioavailability of a certain toxic in the environment is to measure the concentration inside soil organisms. Non-target saprotrophic organisms like isopods are often exposed to agrochemicals or other kind of persistent chemicals. In this study the isopod Porcellionides pruinosus was exposed to a constant concentration of Lindane (gamma-HCH) via food. Using toxicokinetic models the bioaccumulation and fate of the pesticide by isopods was assessed and compared with previous studies, where an unexpected decrease in gamma-HCH concentration was observed. Animal body burdens showed higher values, and a lower assimilation rate constant, although the elimination rate constant was twice the value previously observed. It was also observed that a significant amount of gamma-HCH had an unknown fate. To discover its possible destiny, a factorial experiment was carried out using two types of CO2 traps and contaminated leaves in the presence and absence of isopods. It was concluded that isopod activity might have been responsible for a more rapid biotransformation of gamma-HCH in leaves, since the amount of the pesticide is reduced in their presence.
