Pesticides measured in air and precipitation in the Yamaska Basin (Québec): occurrence and concentrations in 2004.

Air and precipitation samples were collected and analyzed for 91 pesticides or metabolites from May to September 2004 at St. Damase, an agricultural site located in Yamaska basin in Québec, Canada. A broad range of pesticides was detected during this experiment where 40 different compounds were measured. Most of the samples showed more than 10 simultaneous pesticide detections and sometimes reaching 19 simultaneous detections. The most detected pesticides in air were trifluralin, metolachlor and captan, which were found in all the samples during the 5 months of measurements. For the detected compounds, the average concentrations ranged from 4 pg/m3 to 8 ng/m3. Some of the pesticides detected in air were found in precipitation samples as well showing that wet deposition can occur and have an impact on aquatic ecosystems. The most important pesticides detected were related to corn and soya cultivations, the two main cultures in this region highlighting that the major sources come from local applications. On the other hand, the detection of some pesticides in precipitation which were undetectable in air implies that some compounds may have a long range transport origin.

Hepatic retinoids of bullfrogs in relation to agricultural pesticides.

Agricultural pesticides often have been cited as a factor affecting indigenous amphibian populations, but possible effects of pesticides and other factors associated with agricultural practices are understood poorly. Adult bullfrogs (Rana catesbeiana) were collected within the Yamaska River basin (Quebec, Canada) in subwatersheds representing low, medium, and high agricultural activities and 53 pesticides were analyzed in surface water. More pesticides were detected in subwatersheds associated with high agricultural activities like Rivière Noire and Rivière à la Barbue and pesticide concentrations were higher compared to the other study sites. Female and male body weights differed between sites. In the case of males, body weight was significantly less at Rivière à la Barbue. Liver retinol stores were decreased significantly in male bullfrogs from Rivière Noire, although total retinyl esters concentrations varied between sites having the highest concentration at Yamaska-Nord where the agricultural activity was considered low. The ratio of hepatic retinyl palmitate to retinol tended to be higher for male bullfrogs from Rivière Noire and Rivière à la Barbue. These results suggest that factors associated with intensive agricultural practices may affect the body weight and retinoid stores in male bullfrogs living in these agroecosystems.

Plasma retinoid profile in bullfrogs, Rana catesbeiana, in relation to agricultural intensity of sub-watersheds in the Yamaska River drainage basin, Québec, Canada.

Amphibian populations are decreasing globally and the causes are presently unclear. Retinoids have been extensively studied in other vertebrate classes where they are associated with pleiotropic effects such as susceptibility to disease (including cancer and parasitic infections), deformities and reproduction. To investigate the hypothesis that retinoid homeostasis is influenced by agricultural activities, blood samples were collected from adult bullfrogs, Rana catesbeiana, at each of six sub-watersheds chosen to represent a gradient of agricultural intensity within the Yamaska River drainage basin. Samples of surface water were collected at each of the study sites approximately 1 month after spraying and analyzed for 53 pesticides. Male body weight was significantly different (p<0.001) between study sites with the smallest bullfrogs captured from the Rivière à la Barbue sub-watershed associated with high agricultural intensity. A significant linear regression (p<0.001; R2=0.176) was obtained between plasma retinol and body weight. Plasma retinol concentrations were significantly different between study sites (p<0.001) being lowest at both Rivière Noire and Rivière à la Barbue. More than 60% of the land area in these sub-watersheds is under intensive corn-soya cultivation and surface water contained the highest concentrations of the herbicides atrazine, deethyl-atrazine, simazine, metolachlor, dimethenamide, chlopyralide, dicamba and bentazone. Plasma 13-cis-4-oxo-retinoic acid was significantly different (p<0.001) between sub-watersheds, however this effect was apparently unrelated to agricultural intensity. Plasma retinol was negatively correlated (p=0.026; r=-0.237) with plasma 13-cis-4-oxo-retinoic acid. These results suggest that retinoid homeostasis in bullfrogs may be influenced by agricultural practices.