Effects of fungicide chlorothalonil on freshwater plankton communities: a microcosm study.

Direct and indirect effects of the fungicide chlorothalonil on aquatic plankton community structure were investigated by exposing plankton to chlorothalonil concentrations of 0.010, 0.025, 0.100, 0.250 and 1.000 mg/L over 20 days in 18 microcosms (glass tanks having 8 L of pond water). Each treatment was executed in three replicates. Total phytoplankton and zooplankton abundance and chlorophyll-a concentrations in microcosms were measured 5, 10 and 20 days after pesticide exposure. Plankton community and taxa response to pesticide concentrations were analyzed using the similarity of percentages procedure (SIMPER) and one-way ANOVA test. The results of the study indicated that highest concentration levels of chlorothalonil exposure had a significant impact on phytoplankton and zooplankton taxa. Phytoplankton taxa Amphora sp. and Staurastrum sp. and zooplankton taxa Moina sp. and copepod Nauplius were highly sensitive to chlorothalonil exposure. Phytoplankton taxa Mougeotia sp. increased with increased chlorothalonil (0.1-1.0 mg/L) concentrations, and zooplankton taxa of Aeolosoma sp. showed no significant reduction of individuals in response to pesticide exposure. Results showed that pesticide residues have a direct and rapid impact on phytoplankton and zooplankton community structure. Changes in diversity and species composition induced by pesticides indicate the importance of considering indirect effects of pesticides on the ecological food chain in the aquatic environment.

Evaluation of the effect of landfill leachate on surface and groundwater quality: a case study in tropical Sri Lanka using the evidence of stable isotopes.

The disposal of solid wastes is a significant problem in urban areas in many developed and developing countries. Waterways are often subjected to pollution by effluents discharged from solid waste dumpsites. The stable isotopes and water quality data provide useful information on tracing pollutant sources and their contaminant pathways. The effect of a major solid waste dumpsite on surface and groundwater quality of the surrounding area was investigated by measuring water quality parameters and stable isotopes of deuterium (2H), oxygen (18O), 15 N-ΝΟ3 and 18O-NO3 in tropical Sri Lanka. The surface water and groundwater wells close to the dumpsite indicated clear evidence of leachate contamination with enriched total dissolved solids (TDS), total suspended solids (TSS), ammonia, biochemical oxygen demand (BOD5) and Cl- levels. The correlation of groundwater quality parameters, i.e. EC (-r2 = 0.8), TDS (-r2 = 0.8), TSS (-r2 = 0.5), ammonia (-r2 = 0.4), phosphates (-0.6), sulphates (-0.5), Cl- (-0.6) and isotope δ2H‰ (-0.9) with distance from the dumpsite, further confirmed the effects of dumpsite on groundwater quality. The composition of δ15N-ΝΟ3 and δ18O-NO3 isotopes in the groundwater indicated that the dominant source of NO3- to groundwater is manure septic originating from the dumpsite. The findings of the study provided clear evidence of the effect of open dumping on the water resources of the surrounding area and the need for remedial measures.