RISK ASSESSMENT OF PESTICIDES IN DRAINAGE CHANNELS FROM THE RÍO NEGRO AND NEUQUEN VALLEY (ARGENTINA)

MACCHI PABLO; MONZA LILIANA; GUIÑAZÚ NATALIA; MONTAGNA MONICA; LATINI LORENA; LOEWY MIRIAM

Congreso; XIII Congreso Brasilero de Ecotoxicologia; 2014

Sociedad Brasilera de Ecotoxicología

Agriculture represents the second most important economic activity in the North Patagonia. Despite the implementation on 2006 of an integrated pest management, non-selective insecticides are still being used with significant implications to the environment quality. Previous studies have demonstrated the presence of pesticides in both groundwater and drainage channels2. The aim of this study was to evaluate the risk to aquatic organisms from pesticide-contaminated waters. The study area involves an irrigated 100 ha section of fruit production. Pesticides concentrations were determined during the application period (October to March) from 2008 to 2011 at five sites along drains, and one site from an upstream irrigation channel. In the last two seasons, a macroinvertebrate biomonitoring was also accomplished. The pesticides risk to aquatic organisms was assessed by a tier approach3. A preliminary deterministic assessment of the potential risk was determined by the acute and chronic hazard quotient (HQ). Additionally, the frequency distribution of exposure concentrations was integrated with the concentration-response relationship to generate a Joint Probability Curves (JPC). Finally, in situ analyses of benthic macroinvertebrates were incorporated to compare species density and richness between control site and drains. The concentration ranges (µg/L) determined for azinphosmethyl, chlorpyrifos and carbaryl in drains, during the monitoring period, were from non-detected to 1.02, 1.45, and 11.21; respectively. The pesticide most frequently detected was chlorpyrifos (61%) followed by azinphosmethyl (44%) and carbaryl (21%), in accordance with previously reported data1. For all three pesticides, the acute and chronic HQ exceeded the risk criteria (0.5 and 1; respectively) for invertebrates.The effects of the three pesticides on aquatic organisms, characterized by JPC, showed that azinphosmethyl, chlorpyrifos and carbaryl concentrations over the LC50 of 5% of the species were exceeded 7, 5 and 2 times during the analyzed period; respectively. The benthic community at drains was comprised by 43 invertebrate taxa and 8589 individuals. Relative abundance of macroinvertebrates at the control site was mostly represented by Diptera (Chironomidaespp.and Simulium spp.), Amphipoda (Hyalella curvispina) and Ephemeroptera (Americabaetis alphus, Baetodes sp.). In contrast, the most abundant taxa in drains were Amphipoda (H. curvispina), Mollusca (Heleobia parchapii, Chillina dombeyana) and some Diptera. Taxa richnessat the control site was always significantly higher than at drain channels. Moreover, both taxa richness and abundance were significantly decreased in drains during November, where peak concentrationsof chlorpyrifos and azinphosmethylwere detected in water. The correlation between the pesticide concentration and taxonomic richness and density of the benthic community indicated that only chlorpyrifos concentrations were negatively correlated (Spearman r2 -0.61, p=0.0051 and Spearman r2 -0.59, p=0.0068 for taxonomic richness and density correlation; respectively). Other field studies had also found that Ephemeroptera spp3,4 were among the most pesticide sensitive species. In conclusion, both drain macroinvertebrates taxa richness and abundance were affected by pesticide concentrations, mainly by chlorpyrifos.