The ecotoxicity of binary mixtures of Imazamox and ionized ammonia on freshwater copepods: Implications for environmental risk assessment in groundwater bodies.

Groundwater bodies are impacted by substances such as pesticides and N-fertilizers, which usually occur in the environment as complex mixtures rather than isolated pollutants. The threat that these mixtures pose to groundwater-dwelling organisms is still poorly understood. The aims of the present study were to test the acute effect of a binary mixture of a herbicide (Imazamox) and NH4+ on epigean (Eucyclops serrulatus) and hypogean (Diacyclops belgicus) freshwater copepod species. In addition, to evaluate if the effect of the mixture can be explained by referencing non-interaction models or by more complex interaction models; and the implications for groundwater risk assessment. Compared with the action of the compounds evaluated separately, the effects of Imazamox and NH4+ in the binary mixture were more than additive or synergistic for both species. MixTox models evidenced a dose ratio and dose level deviations from concentration addition and independent action traditional models. The hypogean species was three times more sensitive to NH4+ that the epigean species when assayed as a single chemical. However, D. belgicus was only 1.13 times more sensitive than E. serrulatus when NH4+ was assayed in the mixture. The use of an integrated approach for substances that are known to interact in groundwater, should include copepods species as test organisms.

Environmental impact of insecticides applied on biotech soybean crops in relation to the distance from aquatic ecosystems.

Aquatic environments located in areas cultivated with biotech soybean were studied. Water and sediment samples were analyzed for insecticides, acute toxicity, genotoxicity, detoxification biomarkers, and fish diversity. Samples were taken in the core area of soybean cultivation in Argentina; all measures were related to the distance between the crops and the streams sampled. Endosulfan (alpha + beta) concentrations as high as 553.33 microg/kg were found in sediments from environments located at 0.15 m from treated fields. Ethoxyresorufin-O-deethylase (EROD) activity and cytochrome P4501A1 (CYP1A1) gene expression in fish showed the highest correlation with the environmental concentration of endosulfan. These biomarkers and mortality of amphipods significantly correlated with the concentration of endosulfan in water and sediment, which correlates inversely with the distance between the crop and streams. The differences with respective controls disappear at distances greater than 5 m. The fish diversity was significantly lower from distances between the margin of the stream and soybean crops, not exceeding 2 m.

Improved single-cell gel electrophoresis assay for detecting DNA damage in Eisenia foetida.

The earthworm (Eisenia foetida) is an attractive sentinel species for detecting genotoxicity in soil. In this study, an improved single-cell gel electrophoresis (SCGE) assay was developed for detecting DNA damage in the coelomocytes (lymphocytes) of earthworms. Coelomocytes were obtained from the coelomic fluid using a modified extrusion medium that did not include the mucolytic agent guaiacol. The extruded coelomocytes contained at least three types of cells: eleocytes (75% of the total), amoebocytes, and granulocytes. The DNA migration parameters were determined for untreated cells of each type in order that the assay could be performed with minimum inter- and intra-individual variation. In addition, lysis time was reduced to 10 min, and only one neutralization step was used. DNA damage was detected in isolated eleocytes treated with hydrogen peroxide and cadmium, and in eleocytes from earthworms exposed for up to 21 days to soil containing polycyclic aromatic hydrocarbons. The SCGE assay using earthworm eleocytes appears to be a sensitive biomarker for evaluating exposure to genotoxic compounds.