Occurrence of Four Biocides Utilized in Antifouling Paints, as Alternatives to Organotin Compounds, in Waters and Sediments of a Commercial Estuary in the UK

Waters and sediments from marinas, mooring areas and coastal sites in the Blackwater Estuary, Essex, UK were collected and analysed for the occurrence of Irgarol 1051, chlorothalonil, dichlofluanid and diuron. These biocides were introduced as alternatives to organotin compounds in antifouling products, after restrictions imposed on the use of tributyltin (TBT) in 1987. Samples were collected at the end of one boating season (October 98) and the beginning of the following one (June 99). An input survey was also undertaken with the objective of identifying input sources of these biocides and quantifying the amounts used in the catchment area. The results of the monitoring exercise exhibited some agreement with the findings of the input survey. Irgarol, dichlofluanid and chlorothalonil were detected at a number of sites. Concentrations of Irgarol and dichlofluanid in waters and sediments were enhanced after the boating season and the highest ones were relatively enhanced within the marinas, implying that use in antifoulants accounted for the inputs. Contamination with chlorothalonil was more widespread, consistent with its use in agriculture.