Concentrations of mercury in near shore surface waters of the bay of Biscay and in the Gironde Estuary

Abstract

Total and reactive mercury concentrations have been measured on samples of surface water taken along the shores of the Bay of Biscay and in the Gironde Estuary. In the low turbid areas of the Bay of Biscay the average concentration of total mercury of unfiltered samples is 3.5 ± 0.7 ( n = 15) and the reactive mercury 2.1 ± 0.7 ( n = 12) pmol l −1; the high levels, up to 27.6 (total mercury) and 4.6 (reactive mercury) pmol l −1 are from the most turbid samples taken from the Marennes-Oléron basin. In the Gironde Estuary, the distribution of total dissolved mercury rises to a peak of concentration (38 pmol l −1) within the high turbidity zone where the salinity is lower than 10‰. The possible origin of this pattern of distribution is discussed.