Potential phytoremediation system using macrophyte Limnobium laevigatum to remove in situ Cr from contaminated bottom sediments.

The contamination of aquatic environments with heavy metals is an important issue, and in turn, it is crucial to study remediation techniques that can be applied in situ. In this work, the use of a containment system with macrophytes Limnobium laevigatum is explored in the laboratory to evaluate the remotion of Cr in contaminated sediments. The roots of the plants were placed in contact with the bottom sediment through a containment system. The concentration of Cr in macrophyte and sediment samples exposed to different exposure times (1, 4 and 7 days) was determined by laser-induced breakdown spectroscopy technique. The initial concentration of Cr in the sediment was 112 ± 5 mg/kg and decreased by 65% to the control (p < 0.05) after 24 h of exposure. The removal continued throughout the study time until reaching values of 23 ± 1 mg/kg. In macrophytes, the Cr concentration increased from 20 ± 5 mg/kg to 2066 ± 216 mg/kg after seven days of exposure. The correlation coefficient between Cr concentrations in both matrices was -0.96. Finally, the bioaccumulation factor of Cr in L. laevigatum was 95.22 ± 8.51. Therefore, the system studied could be a potential tool to remedy the bottom sediments of streams and lakes contaminated with heavy metals in situ.

Ecotoxicology and environmental safety toxicity of pyrethroid cypermethrin on the freshwater snail Chilina parchappii: Lethal and sublethal effects.

The aim of the present work was to study the effect of the pyrethroid cypermethrin (CYP) on the non-target freshwater snail Chilina parchappi. Initially, the sensitivity of adult snails to CYP was evaluated via the 96-h LC50 test. Then, snails were exposed to subtethal CYP concentrations (0.1 and 10 mg/l) for 1, 4 and 10 days and the digestive glands were dissected for biomarkers analyses. Enzymatic activity of catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as total glutathione reduced (GSH) levels, were determined. Histological analyses of morphology, intracellular accumulation of lipofucsins and neutral lipids accumulation in the digestive gland were also evaluated. As compared to other molluscs, C. parchappi showed high resistance to CYP exposure evidenced by the 96-h LC50 value (44.59 mg/l). Snails exposed to sublethal CYP concentrations showed a statistically significant increase (p < 0.01) in GST (79-116%) and GPx (45-190%) activities with respect to controls. However, CAT activity showed a tendency to decrease with CYP treatment but was not statistically significantly different compared to control. Only high CYP concentration caused a statistically significant increase (p < 0.01) in GSH content (95-196%). There was evidence of structural changes in the digestive gland of snails exposed to CYP, showing a dose-dependent response. In exposed snails, some of the main symptoms included a reduction in the thickness of the epithelium, vacuolisation of the digestive cells and an increase in the number of excretory cells. Accumulation of lipofuscins (933-1006%) and neutral lipids (403%) were statistically significantly higher (p < 0.05) in snails exposed to CYP compared to control. This study showed that C. parchappii is quite tolerant to CYP exposure and that at sublethal concentrations, GSH metabolism could play a protective role against the pesticide harm in snails. Therefore, it would be interesting to study the response of this organism to other environmental stressors to assess its potential use in monitoring programs.

Environmental diagnosis of an urban basin from a social-ecological perspective.

The critical factor in restoration and conservation of urban streams and their catchments is the human population, however the most of studies of urban ecosystems do not present social descriptors as concrete variables of analysis. The objective of this study is to perform an environmental diagnosis from a social-ecological perspective by considering both ecological and urban development descriptors of an urban basin. We selected 12 sampling sites of the Langueyú upper basin where social and ecological descriptors were determined. We arranged sampling sites according to their physicochemical characteristics (pre-urban, urban and post-urban sites). An ecological index was defined from habitat and biological descriptors: vegetation cover, richness and total density of invertebrates and organic matter. The index determined that urban and post-urban sites showed similar characteristics, and pre-urban sites presented the best habitat and biological conditions. An urbanisation index was defined from urban development descriptors: distance to the stormwater drainage network, number of industries, distance to a house without sewage, impervious surface and housing density. The results showed that the pre-urban and post-urban sites share a greater similarity in relation to the urban descriptors but with different impact in ecological quality. The headwaters in the hills (pre-urban zone) still presents a very good ecological condition (although threatened by urbanisation and tourism); however, once it crosses the dense urban area, no >5 km distance, the environmental degradation is alarming. We were able to determine that the structural measures associated with greater urbanisation, added to illegally connected sewer pipes and illegally industrial connections, produce the ecological degradation of the stream. This environmental diagnosis allowed us a deep understanding of the urbanisation impact on the ecological integrity of an urban stream in a developing country which, like many others, doesn't have monitoring programs or an integrated vision of water resources.

Pesticide residue analyses and biomarker responses of native Costa Rican fish of the Poeciliidae and Cichlidae families to assess environmental impacts of pesticides in Palo Verde National Park.

Pesticide chemical residues in water samples and biomarker responses in transplanted fish were used to monitor environmental hazards of pesticides in Palo Verde National Park (Costa Rica). The Costarican fish, Parachromis dovii (Ciclhidae) and Poecilia gillii (Poecillidae), were selected as sentinel species. Contaminant analyses detected up to 15 different pesticide residues in water with hexachlobenzene (2261 ng l(-1)), phorate (473 ng l(-1)), epoxiconazole (314) and bromacil (117 ng l(-1)) being the compounds found in higher concentrations. Biomarker responses evidenced impacts on cholinesterase activities in transplanted fish at Barbudal site probably due to the presence of organophosphate insecticides such as phorate. High enzyme activities of glutathione S-transferase and catalase and elevated levels of lipid peroxides were also observed at a site impacted by rice fields (Cabuyo); those effects could be associated with the presence of hexachloro benzene and triazole fungicides. In general, P. dovii biomarkers were affected to a greater extent than those of P. gillii in fish transplanted to sites associated with agriculture, which suggests the former species is a good candidate for future surveys.