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Jes Jessen Rasmussen

Buffer strip width and agricultural pesticide contamination in Danish lowland streams: Implications for stream and riparian management

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  • Department of Freshwater Ecology
Non-point source contamination with agricultural pesticides is widely acknowledged as one of the greatest sources of pollution in stream ecosystems, and surface runoff is an important transport route. Consequently, maximum pesticide concentrations occur briefly during heavy precipitation events. According to the WFD, member states are obliged to obtain good ecosystem quality in natural surface waters in 2015. Mitigating the risk of non-point source contamination by agricultural pesticides is therefore an essential management task in river basins. Recently, the SPEAR index was introduced for German streams aiming specifically to detect pesticide impact in streams among a multitude of environmental stressors. In subsequent field studies, SPEAR was successfully linked to pesticide toxicity in terms of toxic units (TU).
In this study we aimed to characterise the occurrence and toxicity (TU) of agricultural pesticides originating from normal agricultural practices. We link the findings to a predictive model for pesticide surface runoff (RP) and evaluate the potential impact of pesticides on benthic macroinvertebrates. Furthermore, we apply detailed land-use data and field characteristics to identify the most important environmental parameters governing the occurrence of agricultural pesticides in Danish streams. We measured the concentration of 23 selected agricultural pesticides in 15 Danish 1st and 2nd order streams. Water samples (storm flow) and sediment samples (bed sediment) were collected. The streams represent a gradient of potential pesticide contamination based on the percentage of agricultural land in the catchment.
Preliminary analyses show that the strongest predictor of TU was minimum buffer strip width (BSW) (P<0.001) followed by percentage of agricultural land and applied amounts of pesticides (P<0.05) in a 2x100 m stream corridor extending 1,000 m upstream. The RP model significantly predicted TU of detected pesticides (P<0.05), and predictive power of the model was enhanced by adding a function of buffer strip width (P<0.05). Measured pesticide toxicity (TU) ranged from -1.57 to -6.5, and the highest observed TU is proposed to have significant effects on benthic macroinvertebrates. This study emphasises the importance of integrating buffer strip characteristics in the assessment and mitigation of risk in agricultural streams. Based on the correlation between BSW and TU, we link BSW to the SPEAR index and estimate a minimum BSW required to mitigate effects of pesticide contamination in lowland streams in rural areas.
Original languageEnglish
Publication year2011
Publication statusPublished - 2011
EventNordic Benthological Society Meeting - Aalborg, Denmark
Duration: 9 May 2011 → …

Conference

ConferenceNordic Benthological Society Meeting
CountryDenmark
CityAalborg
Period09/05/2011 → …

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