A review of the pesticide MCPA in the land‐water environment and emerging research needs

Abstract

Due to its high solubility and poor adsorption to the soil matrix, the post‐emergence herbicide 2‐methyl‐4‐chlorophenoxyacetic acid (MCPA) is susceptible to transport into surface and groundwater bodies, where it can result in compromised water quality and breaches of legislative standards. However, there is still poor understanding of catchment scale dynamics and transport, particularly across heterogeneous hydrogeological settings. While it is known that MCPA degrades under aerobic conditions, negligible breakdown can occur in anaerobic environments, potentially creating a legacy in saturated soils. Fast runoff pathways post application are likely transport routes, but the relative contribution from the mobilization of legacy MCPA from anaerobic zones has yet to be quantified, making the delineation of MCPA sources encountered during monitoring programs challenging. While ecotoxicological effects have been examined, little is known about the interaction of MCPA (and its degradation products) with other pesticides, with nutrients or with colloids, and how this combines with environmental conditions to contribute to multiple stressor effects. We examine the state of MCPA knowledge, using case study examples from Ireland, and consider the implications of its widespread detection in waterbodies and drinking water supplies. Research themes required to ensure the sustainable and safe use of MCPA in an evolving agricultural, social and political landscape are identified here. These include the need to identify mitigation measures and/or alternative treatments, to gain insights into the conditions governing mobilization and attenuation, to map pathways of migration and to identify direct, synergistic and antagonistic ecotoxicological effects. This article is categorized under: Water and Life > Stresses and Pressures on Ecosystems Science of Water > Water Quality

Capillary electrophoresis-mass spectrometry for the direct analysis of glyphosate: method development and application to beer beverages and environmental studies

“…Glufosinate (GLU) is a herbicide structurally related to GLP; a degradation product of GLU is 3-(methylphosphinico)propionic acid (3-MPPA) [94]. MCPA (2-methyl-4-chlorophenoxyacetic acid) is a herbicide with converse properties to GLP; it poorly adsorbs to soil components and thus is highly mobile in the environment [95]. Trifluoroacetic acid (TFA) is a persistent, highly water soluble industrial chemical, which is also derived by (photo)degradation from refrigerants, (per)fluorinated chemicals, pharmaceuticals, and pesticides [96].…”

Benchmarking a decade of holistic agro-environmental studies within the Agricultural Catchments Programme

“…In Ireland, the phenoxy herbicide MCPA (2-methyl-4-chlorophenoxyacetic acid) is frequently used to reduce and inhibit rush (Juncus spp.) cover on grasslands and certain broadleaf weed species (Morton et al, 2020). The compound is highly susceptible to contaminate both surface and groundwater due to its high water solubility and low soil adsorption.…”

“…In Irish groundwater bodies, there were more pesticide metabolites present than the parent active ingredients themselves (McManus et al, 2017). Morton et al (2020) identified a need for more knowledge on mobilisation and transfer processes of MCPA to be able to identify mitigation and treatment measures. Acid herbicides were detected in private drinking water wells (some exceeded recommendations) and were present in the rivers all year in two hydrologically contrasting catchments within the ACP, even though these areas are not associated with herbicide pollution in water.…”

A Fuzzy Cognitive Map method for integrated and participatory water governance and indicators affecting drinking water supplies

“…The characterization of water abstraction and contamination due to point and diffuse losses of nutrients (e.g. nitrogen and phosphorus, Fenton et al, 2017), pesticides (Morton et al, 2019), pathogens (Ashekuzzaman et al, 2018) and emerging contaminants such as micro-plastics and pharmaceuticals (Lou et al, 2014;Naidu et al, 2016;Machado et al, 2016;Lai et al, 2018) in areas with connectivity to drinking water supplies are subjects of on-going research (McGrory et al, 2017;Khan et al, 2018;Schutz et al, 2019;Panikkar et al, 2019;Jaramillo and O'Shea, 2019). Indeed, research into the provision and implementation of "best management practices" on agricultural landscapes to protect drinking water supplies is an important area of research.…”