Distribution of colloidal trace metals in the San Francisco Bay estuary
- 作者：Sañ ; udo-Wilhelmy ; Sergio A. ; Rivera-Duarte ; Ignacio ; Flegal ; A. Russell
- 刊名：Geochimica et Cosmochimica Acta
- 出版年：1996
- 期刊代码：27_00167037
- 类别：ear
- 出版时间：December, 1996
- 卷：60
- 期：24
- 页码：4933-4944
- 文件大小：1.23 M
摘要
The size distribution of trace metals (Al, Ag, Cd, Cu, Fe, Mn, Ni, Sr, and Zn) was examined in surface waters of the San Francisco Bay estuary. Water samples were collected in January 1994 across the whole salinity gradient and fractionated into total dissolved (<0.2 μm), colloidal (10 kDa-0.2 μm), and <10 kDa molecular weight phases. In the low salinity region of the estuary, concentrations of colloidal Al, Ag, and Fe accounted for ≥84%of the total dissolved fraction, and colloidal Cu and Mn accounted for 16-20%of the total. At high salinities, while colloidal Fe was still relatively high (mg align=center border=0 SRC=/images/glyphs/BQ1.GIF>40%of the dissolved), very little colloidal Al, Mn, and Cu (<10%) and no colloidal Ag was detectable. Colloidal Zn accounted for <3%of the total dissolved along the estuary, and colloidal Ni was only detectable (<2%) at the river endmember. All of the total dissolved Cd and Sr throughout the estuary consisted of relatively low molecular weight (<10 kDa) species. The relative affinity of metals for humic substances and their reactivity with particle surfaces appear to determine the amounts of metal associated with colloids. The mixing behavior of metals along the estuary appears to be determined by the relative contribution of the colloidal phase to the total dissolved pool. Metals with a small or undetectable colloidal fraction showed a nonconservative excess (Cd, Cu, Ni, and Mn) or conservative mixing (Sr) in the total dissolved fraction, relative to ideal dilution of river water and seawater along the estuary.