Dissolved and particulate trace metal fluxes through the central English Channel, and the influence of coastal gyres

Measurements of dissolved Cd, Co, Cu, Mn, Ni, Pb, and Zn have been made on a seasonal basis at five stations on a north-south transect across the cent ral English Channel between Cherbourg and the Isle of Wight. Vertical and h orizontal distributions of dissolved Cd, Pb, Cu and Zn art: relatively unif orm except for sampling sites near the English coast. Dissolved Mn and Co s how increased concentrations in the English coastal waters, and for Mn the seasonal trend in concentration follows the pattern seen in the Strait of D over with higher values in the late summer. Ni and Cu are higher in concent ration on the English side, which reflects mainly riverine sources. Measure ments were also made of particulate forms of the metals above plus particul ate Al, Ca, Fe, Mg, Sr and Ti. Water column concentrations of particulate m etals broadly follow the distribution of suspended particulate matter, with highest concentrations near the UK coast. Trace metal concentrations have been integrated with modelled data on fluxes of water to provide estimates of fluxes for these elements into the eastern Channel, and an initial compa rison is made with data for fluxes of metals through the Strait of Dover ob tained during an earlier study. A major influence on the fluxes of particul ate metals through the Isle of Wight-Cherbourg transect is the gyre system to the South east to the Isle of Wight, which has important east to west as well as west to east transport components. For those elements where the di ssolved form of the metal dominates, the large flow of water in the central Channel waters leads to major fluxes of the metals towards the east and th e Strait of Dover. However, the high suspended particulate matter loadings in the coastal waters and impact of the gyre system lead to net east to wes t fluxes of particulate Al, Fe, Mn and Ti. Comparison of these fluxes with data on the net west to east transport of these materials through the Strai t of Dover infers that there must be a significant supply of these particul ate metals to the eastern Channel. (C) 1999 Elsevier Science Ltd. All right s reserved.