A review of long-term pesticide monitoring studies to assess surface water quality trends

Abstract

Aquatic pesticide pollution from both agricultural and urban pest control is a concern in many parts of the world. Making an accurate assessment of pesticide exposure is the starting point to protecting aquatic ecosystems. This in turn requires the design of an effective monitoring program. Monitoring is also essential to evaluate the efficacy of mitigation measures aimed to curb pesticide pollution. However, empirical evidence for their efficacy can be confounded by additional influencing factors, most prominently variable weather conditions. This review summarizes the experiences gained from long-term (>5 years) pesticide monitoring studies for detecting trends and provides recommendations for their improvement. We reviewed articles published in the scientific literature, with a few complements from selected grey literature, for a total of 20 studies which fulfill our search criteria. Overall, temporal trends of pesticide use and hydrological conditions were the two most common factors influencing aquatic pesticide pollution. Eighteen studies demonstrated observable effects to surface water concentrations from changes in pesticide application rates (e.g., use restriction) and sixteen studies from interannual variability in hydrological conditions during the application period. Accounting for seasonal- and streamflow-related variability in trend analysis is important because the two factors can obscure trends caused by changes in pesticide use or management practices. Other mitigation measures (e.g., buffer strips) were only detectable in four studies where concentrations or loads were reduced by > 45%. Collecting additional agricultural (e.g., pesticide use, mitigation measures) and environmental (e.g., precipitation, stream flow) data, as well as establishing a baseline before the implementation of mitigation measures have been consistently reported as prerequisites to interpret water quality trends from long-term monitoring studies, but have rarely been implemented in the past.

Reducing MCPA herbicide pollution at catchment scale using an agri-environmental scheme

“…A combination of BACI experimental design (Van Loon et al, 2019) and enhanced water quality monitoring were innovations in this study and particularly at the large scale studied. For example, out of twenty reviewed studies on pesticide trends in river systems, Chow et al (2020) noted that only four included mitigation monitoring in a full BACI design. Enhanced monitoring of pesticides in catchment rivers is rarer (but see Holvoet et al, 2007 andBaets et al, 2018 for enhanced monitoring in small catchments), with other studies reporting enhanced datasets of up to eighty samples per year (e.g.…”

Optimal design of experiments to improve the characterisation of atrazine degradation pathways in soil

“…Several different (and possibly simultaneously occurring) AT degradation pathways can lead to the formation of identical metabolites. This poses a challenge to the determination of the fate of AT, which in turn confounds our ability to understand why AT persists in natural systems, thus hampering strategies for mitigating pesticide contamination of soils (Chow et al, 2020).…”

Pesticide Research on Environmental and Human Exposure and Risks in Sub-Saharan Africa: A Systematic Literature Review

“…There are only a few research studies on environmental occurrence [ 18 , 19 ] or human exposure and health outcomes of pesticides [ 20 ] in low- and middle-income countries (LIMCs), with particular research gaps in SSA. Additionally, research studies in LMICs often have a disciplinary focus on a specific environmental matrix (e.g., water [ 21 ], soil [ 22 ], or dust [ 23 ]); knowledge, attitude, and practice (KAP) of users [ 16 , 24 , 25 ]; human exposure; and health risks for farmers and farmworkers and vulnerable groups, such as women and children [ 24 , 25 ].…”