Mercury in Mersey estuary sediments, and the analytical procedure for total mercury

Abstract

THE Mersey estuary consists of a wide, shallow upper region, separated from the sea by deeper ‘narrows’. The upper estuary (Fig. 1) is an area of continuous accretion of sediment, observed since the mid-nineteenth century with occasional short periods of depletion. The main freshwater inflows are the River Mersey itself, flowing over Howley Weir, and the Manchester Ship Canal, entering the estuary at Eastham Locks. The River Weaver flows into the Manchester Ship Canal at Weston¹. The area is industrialised and heavily populated and the estuary receives both domestic sewage from surrounding towns and industrial effluent^1,2. We are aware of no published data for mercury concentrations in the sediments of the estuary, and have undertaken such measurements. Samples were obtained from the places shown in Fig. 1. We analysed 136 samples for total mercury and the results presented in Fig. 1 and in Table 1 are compared with other data. The levels found are, in general, somewhat higher than in other, more limited, surveys.