Current‐use pesticides in stream water and suspended particles following runoff: Exposure, effects, and mitigation requirements

Abstract

The European Union's directive for sustainable use of pesticides requires implementing risk mitigation measures at streams threatened by pesticide entries. The need for mitigation measures was investigated at 10 stream sites within an intensively used arable region in central Germany by characterizing pesticide exposure following edge-of-field runoff and effects on the aquatic macroinvertebrates. Moreover, the influence of riparian buffer strip width (as a mitigation measure) at the sampling sites was considered. Generally, invertebrate fauna was dominated by pesticide-tolerant species, suggesting a high pesticide exposure at almost all sites. This result is also reflected by the elevated levels of suspended particle contamination in terms of toxic units (logTUMax > -2), corresponding to one-hundredth of the median lethal concentration (LC50) to Daphnia magna. At two sites that received high aqueous-phase entries of the pyrethroid lambda-cyhalothrin (logTUMax > -0.6), the abundance and number of sensitive species in terms of the species at risk index decreased during the pesticide application period. In contrast, no acute significant negative effects on macroinvertebrates were observed at sites characterised by low water-phase toxicity (logTUMax < -3.5). An influence of riparian buffer strip width on pesticide exposure was not observed, supposedly because of the presence of erosion rills and ephemeral ditches. In conclusion, results show that mitigation measures (such as the improvement of currently present riparian buffer strips) are needed in the study area.

Pesticide authorization in the EU—environment unprotected?

“…It follows that insecticides are an important threat to European freshwater biodiversity, as insecticide levels > RACs lead to severe biodiversity reductions (Stehle and Schulz 2015). This conclusion is in line with smaller-scale field studies reporting pesticide-induced adverse effects on ecosystem function and aquatic biodiversity in small agricultural surface waters (e.g., Schäfer et al 2012;Berenzen et al 2005;Bereswill et al 2013) and a study conducted on organic pollutants in larger EU surface waters (Malaj et al 2014). However, for the first time, the present meta-analysis uses empirical evidence based on scientific data and official RACs to illustrate the extent of the risk for European aquatic ecosystems.…”

“…In addition, several additional small-scale field studies conducted in the EU reported that pesticide exposure produced adverse effects on the aquatic ecosystem structure and function (e.g., Bereswill et al 2013;Schäfer et al 2012;Beketov et al 2013;Schulz 2004). However, no scientific study exists that has evaluated pesticide, or specifically insecticide, field concentrations in EU agricultural surface waters using the regulatory acceptable concentrations (RACs) defined by the environmental risk assessment conducted for official EU authorization.…”

Erosion rills offset the efficacy of vegetated buffer strips to mitigate pesticide exposure in surface waters

“…Moreover, this study proved that buffer strip widths were of limited importance for pesticide exposure levels in streams due to concentrated runoff entries via erosion rills, which prevented laminar sheet flow of runoff across the buffer. In addition, Bereswill et al (2013) showed for an intensively used arable agricultural region in central Germany with slopes varying between 1% and 3% that wide buffer strips do not protect surface waters from high pesticide concentrations due to the presence of erosion rills at the investigated sites.…”

Invertebrate community responses to emerging water pollutants in Iberian river basins

“…More recently, Zubrod et al (2014) has provided evidence that single fungicides and fungicide mixtures result in sublethal and also lethal effects in amphipods at environmentally relevant concentrations. Moreover, they have suggested that when considering repeated exposure together with the presence of multiple stressors in the field, synergistic effects may appear (Holmstrup et al, 2010;Bereswill et al, 2013). Some of these fungicides, such as imazalil and tebuconazole, have been detected in the Júcar River.…”