Tidal Cycles of Total Particulate Mercury in the Jade Bay, Lower Saxonian Wadden Sea, Southern North Sea

摘要

In this study, we evaluate the nature of the relationship between particulate matter and total mercury concentrations. For this purpose, we estimate both of the two values in water column over 12-h tidal cycles of the Jade Bay, southern North Sea. Total particulate mercury in 250 mL water samples was determined by oxygen combustion-gold amalgamation. Mercury contents varied from 63 to 259 ng/g suspended particulate matter (SPM) or 3.5-52.8 ng/L in surface waters. Total particulate mercury content (THgp) was positively correlated with (SPM), indicating that mercury in tidal waters is mostly associated with (SPM), and that tidal variations of total particulate mercury are mainly due to changes in (SPM) content throughout the tidal cycle. Maximum values for THgp were observed during mid-flood and mid-ebb, while the lowest values were determined at low tide and high tide. These data suggest that there are no mercury point sources in the Jade Bay. Moreover, the THgp content at low tide and high tide were significantly lower than the values recorded in the bottom sediment of the sampling site (> 200 ng/g DW), while THgp content during the mid-flood and mid-ebb were comparable to the THg content in the surface bottom sediments. Therefore, changes in THgp content in the water column due to tidal forcing may have resulted from re-suspension of underlying surface sediments with relatively high mercury content.