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Environmental fate assessments to understand surface water pollution from metaldehyde-based molluscicide
Published in Manish Kumar, Sanjeeb Mohapatra, Kishor Acharya, Contaminants of Emerging Concerns and Reigning Removal Technologies, 2022
Concerns over wildlife poisoning recently led to the decision to ban outdoor use of metaldehyde in the UK (Department for Environment, Food … Rural Affairs, Health and Safety Executive, and The Rt Hon Michael Gove MP, 2020). Metaldehyde can still be used elsewhere in Europe. Despite the ban on the outdoor use of metaldehyde, there is still a risk of water quality failures, as metaldehyde is persistent in water and has been observed in water sources from catchment that have not had recent applications (UKWIR, 2015). With the withdrawal of metaldehyde, growers probably have to switch to using ferric phosphate-based molluscicide. Ferric phosphate has low solubility in water, and the environmental fate of the product is not thought to significantly raise the natural concentration of iron and phosphate ions in water, when compared to artificial fertiliser usage. However, it is unclear how the product, formulated with chelate molecules, interacts with the environment, and there are concerns over toxicity to soil invertebrates, such as earthworms (Edwards, 2009).
Pesticide removal from drinking water sources by adsorption: a review
Published in Environmental Technology Reviews, 2019
Stephanie Cosgrove, Bruce Jefferson, Peter Jarvis
Metaldehyde is a molluscicide used for the protection of crop plants against slugs and snails [85]. When consumed, it causes mollusc pests to excrete excessive amounts of mucus, causing death by desiccation as the compound is broken down from metaldehyde to acetaldehyde [86]. However death can be prevented under wet or humid conditions [87]. Metaldehyde is a tetramer of acetaldehyde (C2H4O) [74,88]. Metaldehyde has a stable structure (Table 4) and is not easily degraded under anaerobic conditions. It is polar in nature meaning any interactions with suspended organic matter will be weak and so it will become easily desorbed [88]. The Kd and Kf values for metaldehyde are low indicating little adsorption to soils will occur and so the compound is likely to be mobile in the environment. The Koc value and range suggest that some interaction with organic matter could occur although this is still not high enough to prevent the pesticide from being mobile in the environment as seen from the high number of compliance failures that this pesticide has caused (Figure 1).