TRACE-METALS AND DISSOLVED ORGANIC-CARBON IN ESTUARIES AND OFFSHORE WATERS OF NEW-JERSEY, USA

The behavior and distribution of dissolved (< 0.4-mu-m) Al, Cu, Fe, Mn, Ni, Ti, Zn, Si, and organic carbon have been examined in the inshore and offshore estuarine waters of New Jersey during two seasons (September-October 1986 and June-July 1987). Water samples collected had average salinities of 22 parts per hundred for inshore and 30 parts per hundred for offshore. The removal or addition normalized to the inshore concentration of an element during transport offshore was calculated in this salinity range. Dissolved Si was removed by nearly 50%, and dissolved Fe by 15-30% in both seasons. Removal did not occur for other metals. Dissolved organic carbon was conservative. In offshore water, dissolved Fe, Al, and Ti seemed to be associated with the same colloidal particles. During estuarine mixing, most of the dissolved Fe, probably associated with colloidal oxyhydroxide, was removed; only the Fe that was associated with Al and Ti remained stable. As a result of removing oxyhydroxide, all the dissolved Fe, Al, and Ti in the high-salinity offshore water occurred in the same colloidal particles, possibly clays. This conclusion is further supported by chemical evidence in suspended sediments. The correlation between Al, Fe, and Ti in suspended particles generally indicates the same pattern as that for dissolved metals. These smaller metal-bearing particles (< 0.4-mu-m) might have been supplied through deflocculation of the larger ones (> 0.4-mu-m). These results imply that there is a need to further examine the influence of coastal water on the form of dissolved (< 0.4-mu-m) Fe in the near-shelf seawater. The dissolved Fe in the near-shore region is probably colloidal. This is also possible for some regions of the open ocean where dissolved Fe is supplied mainly by near-shore sources.