Sónia Chelinho

Evaluating a bioremediation tool for atrazine contaminated soils in open soil microcosms: The effectiveness of bioaugmentation and biostimulation approaches

A previously developed potential cleanup tool for atrazine contaminated soils was evaluated in larger open soil microcosms for optimization under more realistic conditions, using a natural crop soil spiked with an atrazine commercial formulation (Atrazerba FL). The doses used were 20x or 200x higher than the recommended dose (RD) for an agricultural application, mimicking over-use or spill situations. Pseudomonas sp. strain ADP was used for bioaugmentation (around 10(7) or 10(8) viable cells g(-1) of soil) and citrate for biostimulation (up to 4.8 mg g(-1) of soil). Bioremediation treatments providing fastest and higher atrazine biodegradation proved to differ according to the initial level of soil contamination. For 20x RD of Atrazerba FL, a unique inoculation with Pseudomonas sp. ADP (9 +/- 1 x 10(7) CFU g(-1)) resulted in rapid atrazine removal (99% of the initial 7.2 +/- 1.6 microg g(-1) after 8d), independent of citrate. For 200x RD, an inoculation with the atrazine-degrading bacteria (8.5 +/- 0.5 x 10(7) CFU g(-1)) supplemented with citrate amendment (2.4 mg g(-1)) resulted in improved biodegradation (87%) compared with bioaugmentation alone (79%), even though 7.8 +/- 2.1 microg of atrazine g(-1) still remained in the soil after 1 wk. However, the same amount of inoculum, distributed over three successive inoculations and combined with citrate, increased Pseudomonas sp. ADP survival and atrazine biodegradation (to 98%, in 1 wk). We suggest that this bioremediation tool may be valuable for efficient removal of atrazine from contaminated field soils thus minimizing atrazine and its chlorinated derivatives from reaching water compartments.

Improving ecological risk assessment in the Mediterranean area: Selection of reference soils and evaluating the influence of soil properties on avoidance and reproduction of two oligochaete species

A current challenge in soil ecotoxicology is the use of natural soils as test substrates to increase ecological relevance of data. Despite the existence of six natural reference soils (the Euro-soils), some parallel projects showed that these soils do not accurately represent the diversity of European soils. Particularly, Mediterranean soils are not properly represented. To fill this gap, 12 natural soils from the Mediterranean regions of Alentejo, Portugal; Cataluña, Spain; and Liguria, Italy, were selected and used in reproduction and avoidance tests to evaluate the soil habitat function for earthworms (Eisenia andrei) and enchytraeids (Enchytraeus crypticus). Predictive models on the influence of soil properties on the responses of these organisms were developed using generalized linear models. Results indicate that the selected soils can impact reproduction and avoidance behavior of both Oligochaete species. Reproduction of enchytraeids was affected by different soil properties, but the test validity criteria were fulfilled. The avoidance response of enchytraeids was highly variable, but significant effects of texture and pH were found. Earthworms were more sensitive to soil properties. They did not reproduce successfully in three of the 10 soils, and a positive influence of moisture, fine sand, pH, and organic matter and a negative influence of clay were found. Moreover, they strongly avoided soils with extreme textures. Despite these limitations, most of the selected soils are suitable substrates for ecotoxicological evaluations.

Influence of soil properties on the performance of Folsomia candida: Implications for its use in soil ecotoxicology testing

Nineteen Mediterranean natural soils with a wide range of properties and the Organisation for Economic Co-operation and Development (OECD) artificial soil were used to assess the influence of soil properties on the results of avoidance and reproduction tests carried out with the soil collembolan species Folsomia candida. Compared to natural soils, the OECD soil was mostly rejected by individuals when a natural soil was offered in avoidance tests, and the number of offspring produced was generally lower than the one obtained in natural soils. None of the soil properties assessed showed a significant influence on the avoidance behavior. More precisely, only soil moisture was included in the model explaining the avoidance response (avoidance increased with increasing differences in moisture), but its contribution was marginally not significant. The model derived explained only 16% of the variance in avoidance response. On the contrary, several soil properties significantly influenced reproduction (number of offspring increased with increasing moisture content, increasing coarse texture, and decreasing nitrogen content). In this case, the model explained 45% of the variance in reproduction. These results, together with the fact that most of the selected soils fulfilled the validity criteria in both avoidance and reproduction tests, confirm the literature experience showing that this species is relatively insensitive to soil properties and hence highly suitable to be used in ecotoxicological tests with natural soils. In addition, our study highlights the need for accuracy in soil moisture adjustment in soil ecotoxicological tests with this species. Otherwise, results of both avoidance and reproduction tests might be biased.

Integrated ecological risk assessment of pesticides in tropical ecosystems: A case study with carbofuran in Brazil

The aim of the present study is to contribute an ecologically relevant assessment of the ecotoxicological effects of pesticide applications in agricultural areas in the tropics, using an integrated approach with information gathered from soil and aquatic compartments. Carbofuran, an insecticide/nematicide used widely on sugarcane crops, was selected as a model substance. To evaluate the toxic effects of pesticide spraying for soil biota, as well as the potential indirect effects on aquatic biota resulting from surface runoff and/or leaching, field and laboratory (using a cost-effective simulator of pesticide applications) trials were performed. Standard ecotoxicological tests were performed with soil (Eisenia andrei, Folsomia candida, and Enchytraeus crypticus) and aquatic (Ceriodaphnia silvestrii) organisms, using serial dilutions of soil, eluate, leachate, and runoff samples. Among soil organisms, sensitivity was found to be E. crypticus < E. andrei < F. candida. Among the aqueous extracts, mortality of C. silvestrii was extreme in runoff samples, whereas eluates were by far the least toxic samples. A generally higher toxicity was found in the bioassays performed with samples from the field trial, indicating the need for improvements in the laboratory simulator. However, the tool developed proved to be valuable in evaluating the toxic effects of pesticide spraying in soils and the potential risks for aquatic compartments.

Carbofuran effects in soil nematode communities: using trait and taxonomic based approaches.

This work intends to implement the use of native soil nematode communities in ecotoxicological tests using a model pesticide and two geographically nematode communities (Mediterranean and sub-tropical) in order to obtain new perspectives on the evaluation of the toxic potential of chemical substances. The environmental condition of the nematode communities was described using a trait-based approach (grouping the organisms according to their feeding traits) and a traditional taxonomic method (identification to family level). Effects on total nematode abundance, number of families and abundance of nematode feeding groups as well as potential shifts in both trophic and family structure were assessed. Agricultural soils from Curitiba (Brazil) and Coimbra (Portugal) were sampled and the corresponding nematode communities were extracted. Part of the collected soil was defaunated and spiked with four doses of a carbofuran commercial formulation. Afterwards each of the replicates was inoculated with a nematode suspension containing ≈200 or 300 nematodes. After 14 and 28 d of exposure the nematodes were extracted, counted and identified at family level and separately classified according to their feeding traits. The patterns of nematode responses revealed a decrease in the total abundance and a reduction in the number of families. Despite the similar effects observed for both communities, statistically significant toxic effects were only found within the Portuguese community. The total nematode abundance was significantly reduced at the highest carbofuran concentrations and significant shifts in the family structure were detected. However, the trophic structure, i.e., the contribution of each feeding group for the overall community structure, did not significantly change along the contamination gradient. Results showed that using such a trait-based approach may increase the ecological relevance of toxicity data, by establishing communalities in the response to a chemical from two different taxonomic communities, although with potential loss of information on biodiversity of the communities.

Effects of NaCl and seawater induced salinity on survival and reproduction of three soil invertebrate species

The increase of global mean temperature is raising serious concerns worldwide due to its potential negative effects such as droughts and melting of glaciers and ice caps leading to sea level rise. Expected impacts on soil compartment include floodings, seawater intrusions and use of saltwater for irrigation, with unknown effects on soil ecosystems and their inhabitants. The present study aimed at evaluating the effects of salinisation on soil ecosystems due to sea level rise. The reproduction and mortality of three standard soil invertebrate species (Folsomia candida, Enchytraeus crypticus, Hypoaspis aculeifer) in standard artificial OECD soil spiked with serial dilutions of seawater/gradient of NaCl were evaluated according to standard guidelines. An increased sensitivity was observed in the following order: H. aculeifer≪E. crypticus≈F. candida consistent with the different exposure pathways: springtails and enchytraeids are exposed by ingestion and contact while mites are mainly exposed by ingestion due to a continuous and thick exoskeleton. Although small differences were observed in the calculated effect electrical conductivity values, seawater and NaCl induced the same overall effects (with a difference in the enchytraeid tests where a higher sensitivity was found in relation to NaCl). The adverse effects described in the present study are observed on soils not considered saline. Therefore, the actual limit to define saline soils (4000 μS cm(-1)) does not reflect the existing knowledge when considering soil fauna.

Toxicity of phenmedipham and carbendazim to Enchytraeus crypticus and Eisenia andrei (Oligochaeta) in Mediterranean soils

PurposeThe main objective of the present study was to evaluate the toxicity of two reference chemicals, Carbendazim and Phenmedipham, for the compostworm Eisenia andrei (effects of Carbendazim) and the potworm Enchytraeus crypticus (effects of Phenmedipham) in 12 Mediterranean soils with contrasting soil properties. The observed toxicity was also compared to that obtained for OECD standard soil, used as a control.Materials and methodsThe soils were selected to be representative for the Mediterranean region and to cover a broad range of soil properties. The evaluated endpoints were avoidance behavior and reproduction. Soils were also assembled in two groups according to their pedological properties.Results and discussionToxicity benchmarks (AC50s) obtained for E. andrei avoidance behavior in carbendazim-contaminated soils were generally higher for sandy soils with low pH. The toxic effects on the reproduction of the compostworms were similar in the six tested soils, indicating a low influence of soil properties. The avoidance response of E. crypticus towards Phenmedipham was generally highly variable in all tested soils. Even though, a higher toxicity was observed for more acidic soils. The EC50s for reproduction of the latter species varied by a factor of 9 and Phenmedipham toxicity also tended to be increasing in soils with lower pH, except for the soils with extreme organic matter content (0.6 and 5.8%).ConclusionsA soil effect on chemical toxicity was clearly confirmed, highlighting the influence that test soils can have in site-specific ecological risk assessment. Despite some relationships between soil properties and toxicity were outlined, a clear and statistically significant prediction of chemical toxicity could not be established. The range of soil properties was probably narrow to give clearer and more consistent insights on their influence. For the four groups of tests, the toxicity observed for OECD soil was either similar, lower, or generally higher if compared with Mediterranean soils. Moreover, it did represent neither the organic matter content found in Mediterranean soils nor their textural classes.

Suitability of a Saccharomyces cerevisiae-based assay to assess the toxicity of pyrimethanil sprayed soils via surface runoff: Comparison with standard aquatic and soil toxicity assays

The present study is aimed at evaluating whether a gene expression assay with the microbial eukaryotic model Saccharomyces cerevisiae could be used as a suitable warning tool for the rapid preliminary screening of potential toxic effects on organisms due to scenarios of soil and water contamination with pyrimethanil. The assay consisted of measuring changes in the expression of the selected pyrimethanil-responsive genes ARG3 and ARG5,6 in a standardized yeast population. Evaluation was held by assessing the toxicity of surface runoff, a major route of pesticide exposure in aquatic systems due to non-point-source pollution, which was simulated with a pyrimethanil formulation at a semifield scale mimicking worst-case scenarios of soil contamination (e.g. accident or improper disposal). Yeast cells 2-h exposure to the runoff samples led to a significant 2-fold increase in the expression of both indicator genes. These results were compared with those from assays with organisms relevant for the aquatic and soil compartments, namely the nematode Caenorhabditis elegans (reproduction), the freshwater cladoceran Daphnia magna (survival and reproduction), the benthic midge Chironomus riparius (growth), and the soil invertebrates Folsomia candida and Enchytraeus crypticus (survival and reproduction). Under the experimental conditions used to simulate accidental discharges into soil, runoff waters were highly toxic to the standard test organisms, except for C. elegans. Overall, results point out the usefulness of the yeast assay to provide a rapid preview of the toxicity level in preliminary screenings of environmental samples in situations of inadvertent high pesticide contamination. Advantages and limitations of this novel method are discussed.

Applying a GLM-based approach to model the influence of soil properties on the toxicity of phenmedipham to Folsomia candida

PurposeSoil properties are the main explanation to the different toxicities obtained in different soils due to their influence on chemical bioavailability and the test species performance itself. However, most prediction studies are centred on a few soil properties influencing bioavailability, while their direct effects on test species performance are usually neglected. In our study, we develop prediction models for the toxicity values obtained in a set of soils taking into account both the chemical concentration and their soil properties.Materials and methodsThe effects on the avoidance behaviour and on reproduction of the herbicide phenmedipham to the collembolan Folsomia candida is assessed in 12 natural soils and the Organisation for Economic Co-operation and Development (OECD) artificial soil. The toxicity outcomes in different soils are compared and explanatory models are constructed by generalised linear models (GLMs) using phenmedipham concentrations and soil properties.Results and discussionAt identical phenmedipham concentrations, the effects on reproduction and the avoidance response observed in OECD soil were similar to those observed in natural soils, while effects on survival were clearly lower in this soil. The organic matter and silt content explained differences in the avoidance behaviour in different soils; for reproduction, there was a more complex pattern involving several soil properties.ConclusionsOur results highlight the need for approaches taking into account all the soil properties as a whole, as a necessary step to improve the prediction of the toxicity of particular chemicals to any particular soil.

Semifield testing of a bioremediation tool for atrazine-contaminated soils: Evaluating the efficacy on soil and aquatic compartments

The present study evaluated the bioremediation efficacy of a cleanup tool for atrazine-contaminated soils (Pseudomonas sp. ADP plus citrate [P. ADP + CIT]) at a semifield scale, combining chemical and ecotoxicological information. Three experiments representing worst-case scenarios of atrazine contamination for soil, surface water (due to runoff), and groundwater (due to leaching) were performed in laboratory simulators (100 × 40 × 20 cm). For each experiment, three treatments were set up: bioremediated, nonbioremediated, and a control. In the first, the soil was sprayed with 10 times the recommended dose (RD) for corn of Atrazerba and with P. ADP + CIT at day 0 and a similar amount of P. ADP at day 2. The nonbioremediated treatment consisted of soil spraying with 10 times the RD of Atrazerba (day 0). After 7 d of treatment, samples of soil (and eluates), runoff, and leachate were collected for ecotoxicological tests with plants (Avena sativa and Brassica napus) and microalgae (Pseudokirchneriella subcapitata) species. In the nonbioremediated soils, atrazine was very toxic to both plants, with more pronounced effects on plant growth than on seed emergence. The bioremediation tool annulled atrazine toxicity to A. sativa (86 and 100% efficacy, respectively, for seed emergence and plant growth). For B. napus, results point to incomplete bioremediation. For the microalgae, eluate and runoff samples from the nonbioremediated soils were extremely toxic; a slight toxicity was registered for leachates. After only 7 d, the ecotoxicological risk for the aquatic compartments seemed to be diminished with the application of P. ADP + CIT. In aqueous samples obtained from the bioremediated soils, the microalgal growth was similar to the control for runoff samples and slightly lower than control (by 11%) for eluates.