Distribution of Dissolved Mercury in the Irish Sea

Abstract

PRESTON et al.¹ have recently examined the distribution of a number of heavy metals in British coastal waters. They have found that the average concentrations of these elements in waters and marine organisms were significantly higher in samples from the eastern Irish Sea than in those from other areas. Fish and shellfish from this region (particularly the Mersey Estuary and Lune Deep) have been observed to have the highest average contents of mercury of any from around the British Isles². No data are available for the concentration of the element in the seawater of the Irish Sea, nor is anything known about whether significant mercury pollution arises from liquid wastes discharged into the sea from the populous, highly industrialized areas of Lancashire. Trade effluents from the many chemical and industrial plants (including three chlorine-alkali works) would probably be the principal sources of mercury, but the input from sewage, which may contain a significant concentration of mercury (2–150 p.p.m. on the dry weight)^3,4, would also be important, as the total daily discharge of (mainly untreated) sewage to the area amounts to about 0.7 × 10⁶ m³ (ref. 3). We describe here the distribution pattern of dissolved mercury in the Irish Sea, and have demonstrated that significant pollution occurs in the eastern coastal strip.