Pesticides drive risk of micropollutants in wastewater-impacted streams during low flow conditions

Abstract

Micropollutants enter surface waters through various pathways, of which wastewater treatment plants (WWTPs) are a major source. The large diversity of micropollutants and their many modes of toxic action pose a challenge for assessing environmental risks. In this study, we investigated the potential impact of WWTPs on receiving ecosystems by describing concentration patterns of micropollutants, predicting acute risks for aquatic organisms and validating these results with macroinvertebrate biomonitoring data. Grab samples were taken upstream, downstream and at the effluent of 24 Swiss WWTPs during low flow conditions across independent catchments with different land uses. Using liquid chromatography high resolution tandem mass spectrometry, a comprehensive target screening of almost 400 organic substances, focusing mainly on pesticides and pharmaceuticals, was conducted at two time points, and complemented with the analysis of a priority mixture of 57 substances over eight time points. Acute toxic pressure was predicted using the risk assessment approach of the multi-substance potentially affected fraction, first applying concentration addition for substances with the same toxic mode of action and subsequently response addition for the calculation of the risk of the total mixture. This toxic pressure was compared to macroinvertebrate sensitivity to pesticides (SPEAR index) upstream and downstream of the WWTPs. The concentrations were, as expected, especially for pharmaceuticals and other household chemicals higher downstream than upstream, with the detection frequency of plant protection products upstream correlating with the fraction of arable land in the catchments. While the concentration sums downstream were clearly dominated by pharmaceuticals or other household chemicals, the acute toxic pressure was mainly driven by pesticides, often caused by the episodic occurrence of these compounds even during low flow conditions. In general, five single substances explained much of the total risk, with diclofenac, diazinon and clothianidin as the main drivers. Despite the low predicted acute risk of 0%-2.1% for affected species, a significant positive correlation with macroinvertebrate sensitivity to pesticides was observed. However, more effect data for pharmaceuticals and a better quantification of episodic pesticide pollution events are needed for a more comprehensive risk assessment.

Resilience to heat waves in the aquatic snail Lymnaea stagnalis: Additive and interactive effects with micropollutants

“…Previous studies looking into the effects of simultaneous exposure to high temperature and pollutants have reported higher frequency and impact of synergistic effects of these stressors (summarised by, e.g., Holmstrup et al., ). The concentrations of pollutants in these studies were, however, higher than what is normally observed in natural environments (Munz et al., ). The magnitude of synergism may thus depend on both the chemical concentration and the exposure temperature (e.g.…”

“…While no data on the MP concentrations in pond water in the area exist, MPs are common in freshwater systems in the central Europe (e.g. Munz et al, 2016;Wittmer et al, 2010).…”

Prospective mixture risk assessment and management prioritizations for river catchments with diverse land uses

“…The outputs of the present study suggest strong simplifying patterns of risk in highly diverse sets of mixture exposures. Land use–related chemical signatures appear to exist, whereby mixture effects are commonly caused by a few chemicals (for a given toxicological endpoint), although those few chemicals differ with land use and time (Munz et al 2017). …”

Simultaneous exposure to a pulsed and a prolonged anthropogenic stressor can alter consumer multifunctionality

“…This consisted of low concentrations of pharmaceuticals, a hormone, a herbicide, a fungicide, a pesticide, an insecticide, a corrosion inhibitor and a sweetener (Supplementary material Appendix 1 Table A1) similar to the mix described in Stamm et al (2016) and Salo et al (2017). These chemicals and concentrations were chosen because they are commonly observed in freshwater ecosystems in central Europe (Wittmer et al 2010, Munz et al 2017) and known to cause organismal level effects in snails (Salo et al 2017). To ensure constant exposure to MPs and sufficient water quality, water was changed every second day in all experimental units.…”