The distribution of hydrocarbons and metals in the north-eastern Irish Sea prior to development of the Morecambe Bay gas field

Samples of subsurface water and surface sediments, collected from the north-eastern Irish Sea in 1982–3 before development of the Morecambe Bay gas field, have been analysed for hydrocarbons and metals. Total hydrocarbon concentrations were determined in both water and sediments by fluorescence spectroscopy; specific aliphatic and aromatic hydrocarbons were also determined in sediment samples from selected stations by computerised gas chromatography—mass spectrometry. At selected stations, concentrations of metals (Cr, Ni, Cu, Zn, Cd, Ba, Hg and Pb) were determined in whole surface sediments and of these metals, with the exception of barium, in the sediment fine fraction (< 90 μm). The results of these analyses show widespread contamination of the north-eastern Irish Sea by both metals and hydrocarbons, particularly in the south of the survey area, close to the Rivers Mersey, Dee and Ribble, and in Liverpool Bay, but extending through the area around the gas field. Estimates are made of the magnitude of the input of certain metals that may result from cuttings discharge during the development of the gas field, and these are compared with the inputs to the area from other sources including sea disposal and river inputs.