Herbicide accumulation and evolution in reservoir sediments

Abstract

The aim of the present study was to understand the effect of reservoir configurations on sediment pesticide fate. Two dams were selected on the River Garonne, in southwest France: Carbonne and Golfech, both with reservoirs subject to accumulation of herbicide-contaminated sediment. They are situated upstream and downstream respectively of an agricultural and urban area: the Mid-Garonne. The results presented include pesticide concentrations and C/N ratios in the smaller sediment particles (<2 mm) and values of oxygenation and herbicide concentrations in the water. The dynamic behaviour of sediment in the reservoirs is discussed. The present study shows that the theoretical lifespan (weak remanence in vitro) and the results actually observed in the sediment are conflicting. Pesticide contamination in Carbonne indicates conservation, even accumulation, of herbicide molecules while in Golfech transformation processes clearly dominate. The hydromorphological position of Golfech reservoir, i.e. located at the junction of two rivers with contrasting hydrological regimes and very different oxygenation conditions, leads to accelerated pesticide desorption or degradation. Unfortunately, this configuration is rare.

Multistress effects on goldfish (Carassius auratus) behavior and metabolism

“…The Save River watershed, located in the Gascogne area, is mainly used for intensive agriculture (corn, wheat, and sunflower). High contamination levels of surface waters and sediment by triazines (atrazine, DEA, cyanazine), ureas (isoproturon, linuron, chlorotoluron), and anilides (metolachlor, metazachlor) have been reported in the Gascogne area during spring flood (Devault et al 2009;Polard et al 2011). According to the analysis conducted by Pollard (2011), we selected six herbicides and one fungicide using three criteria: the frequency of detection, the concentration, and the representation of the different families of molecules detected.…”

Spatial distribution and reduction of PCDD/PCDF Toxic Equivalents along three shallow lowland reservoirs

“…Reservoirs also play a role as traps for suspended matter (Krasa et al 2005; Kentzer et al 2010; Li et al 2011; Ran et al 2013) and, consequently, for associated chemical toxicants (Devault et al 2009; Chi et al 2011), thus improving the water quality in downstream and coastal zones (Kentzer et al 2010). A decrease in flow velocity and an increase of flocculent settling in reservoirs create excellent conditions for the sedimentation and deposition of pollutants.…”

The role of a lowland reservoir in the transport of micropollutants, nutrients and the suspended particulate matter along the river continuum

“…Moreover, they are considered as an efficient trap for sediments and consequently, for the associated chemical toxicants, including nutrients and PCBs (Devault et al 2009). The decrease in the flow velocity and the increase of flocculent settling in constructed reservoirs create perfect conditions for sedimentation and deposition of pollutants.…”