The frequency of Environmental Quality Standard (EQS) exceedance for chlorinated organic pollutants in rivers of the Humber catchments

The southern industrial rivers (Aire, Calder, Don and Trent) feeding the Humber estuary were routinely monitored for a range of chlorinated micro-organic contaminants at least once a week over a 1.5-year period. Environmental Quality Standards (EQSs) for inland waters were set under the European Economic Community for a limited number of problematic contaminants (18). The results of the monitoring program for seven classes of chlorinated pollutants on the EQS list are presented in this study. All compounds were detected frequently with the exception of hexachlorobutadiene (where only one detectable measurement out of 280 individual samples occurred). In general, the rivers fell into two classes with respect to their contamination patterns. The Aire and Calder carried higher concentrations of micro-pollutants than the Don and Trent, with the exception of hexachlorobenzene (HCB). For Σhexachlorocyclohexane (HCH) isomers (α+γ) and for dieldrin, a number of samples (∼5%) exceeded their EQS for both the Aire and Calder. Often, ΣHCH concentrations were just below the EQS level. Levels of p,p′-DDT on occasions approached the EQS for these two rivers, but only one sample (out of 140) exceeded the EQS. No compounds exceeded their EQS levels on the Don and Trent. Analysis of the ratio of γHCH/αHCH indicated that the source of HCH for the Don and Trent catchments was primarily lindane (γHCH) and, to a lesser extent, technical HCH (mixture of HCH isomers, dominated by αHCH), while the source(s) for the Aire and Calder had a much higher contribution from technical HCH.