Spatial and temporal trends and flow dynamics of glyphosate and other pesticides within an agricultural watershed in Argentina

Abstract

In the present study, we evaluated the spatial and temporal trends of current-use pesticides in surface water and sediments as well as their relationship with hydrological stream dynamics within the agricultural watershed of El Crespo stream (Buenos Aires Province, Argentina). We sampled 2 contrasting sites: site 1 (upstream), surrounded by agricultural lands, and site 2 (downstream), surrounded by natural grasslands. Most of the applied pesticides (glyphosate, 2,4-D, atrazine, tebuconazole, and imidacloprid) were detected at high frequencies in surface water samples at both sites. However, only glyphosate and aminomethylphosphonic acid (AMPA) were present at high concentrations and had a significant spatial-temporal trend. The highest concentrations were found during spring 2014 at site 1, in association with the intense rains that occurred in that season. The fact that glyphosate and AMPA concentrations were higher than the rest of the studied compounds is closely related to the land use within the watershed, as glyphosate was the most applied herbicide during the fallow period of glyphosate-resistant crops (soybean, maize). The pesticide mixture had a significant spatial-temporal trend, reaching the highest levels during storm flow events in spring 2014. The intensive rains in spring 2014 could be the main factor influencing stream hydrology and pesticide behavior at El Crespo watershed. The estimated annual pesticide losses were 3.11 g/ha at site 1 and 0.72 g/ha at site 2. This result indicates that an attenuation process could be decreasing pesticide loads during downstream transport from site 1 to site 2. Environ Toxicol Chem 2017;36:3206-3216. © 2017 SETAC.

Pesticide bioaccumulation in epilithic biofilms as a biomarker of agricultural activities in a representative watershed

“…In autumn/winter season, only two pesticides were found at 100% of the sites monitored (2,4-D and carbendazim), but all 20 compounds were quantified in biofilms with frequency ranging from 22% (thifensulfuron-methyl) to 83% (atrazine and tebuconazole, Table 2). Some spring and early summer rainfall events (Pascual Aguilar et al 2017;Pérez et al 2017;Rabiet et al 2010); the 230 same was observed in biofilms in the present study.…”

Daily stream samples reveal highly complex pesticide occurrence and potential toxicity to aquatic life

“…Current-use pesticides are frequently detected in streams globally, often occur as complex mixtures, and can pose risks to aquatic life (Bereswill et al, 2013;Gilliom et al, 2006;Hageman et al, 2019;Hladik and Kolpin, 2016;Metcalfe et al, 2016;Nowell et al, 2018;Pérez et al, 2017;Stehle and Schulz, 2015;Stone et al, 2014). Shortterm peaks in pesticide concentrations in streams can occur as a result of seasonal or event-driven pesticide applications (e.g., infestation or public-health hazard) and streamflow conditions (Liess et al, 1999;Rabiet et al, 2010).…”

Pesticide contamination of the upper Elbe River and an adjacent floodplain area

“…Pesticides enter the riverine system either as particle bound, if the substances are sorbed to the topsoil and eroded and transported via surface-runoff, dissolved via drainage and the groundwater, or directly via spray-drift (Schulz 2004;Topaz et al 2018). The transport pathways for the particle bound or dissolved transport depend on the physicochemical properties of the substances, time of pesticide application, and the characteristics of the catchment (e.g., soils, land management) (Larson et al 1995;Pérez et al 2017). Once, entered the stream, the pesticide load dynamics is affected by the partitioning between the dissolved and the adsorbed phases, whereby some pesticides tend to bind to the suspended sediments and are transported as particulatebound pollutants, whereas others are more stable in their dissolved phase (Chapman et al 2013;Birch et al 2015;Carpenter et al 2016).…”