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Titolo:
DISTRIBUTION OF COLLOIDAL TRACE-METALS IN THE SAN-FRANCISCO BAY ESTUARY
Autore:
SANUDOWILHELMY SA; RIVERADUARTE I; FLEGAL AR;
Indirizzi:
SUNY STONY BROOK,MARINE SCI RES CTR STONY BROOK NY 11794 UNIV CALIF SANTA CRUZ,EARTH SCI BOARD SANTA CRUZ CA 95064
Titolo Testata:
Geochimica et cosmochimica acta
fascicolo: 24, volume: 60, anno: 1996,
pagine: 4933 - 4944
SICI:
0016-7037(1996)60:24<4933:DOCTIT>2.0.ZU;2-5
Fonte:
ISI
Lingua:
ENG
Soggetto:
U-238 TH-234 DISEQUILIBRIA; DISSOLVED ORGANIC-MATTER; RIVER WATER; PARTICLE CONCENTRATION; OCEAN WATERS; HUMIC ACIDS; SEA-WATER; SEAWATER; IRON; BEHAVIOR;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
78
Recensione:
Indirizzi per estratti:
Citazione:
S.A. Sanudowilhelmy et al., "DISTRIBUTION OF COLLOIDAL TRACE-METALS IN THE SAN-FRANCISCO BAY ESTUARY", Geochimica et cosmochimica acta, 60(24), 1996, pp. 4933-4944

Abstract

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 mu m), colloidal (10 kDa-0.2 mu m), and <10 kDa molecular weight phases. In the low salinity region of the estuary, concentrations of colloidal Al, Ag,and Fe accounted for greater than or equal to 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 (similar to 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 molecularweight (<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 behaviorof 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. The salt-induced coagulation of colloidal Al, Fe, and Cu is indicated by their highly nonconservative removal along the salinity gradient. However, colloidal metals with low affinityfor humic substances (Mn and Zn) showed conservative mixing behavior,indicating that some riverine colloids are not effectively aggregatedduring their transport to the sea. While colloidal metal concentrations correlated with dissolved organic carbon, they also covaried with colloidal Al, suggesting that colloids are a mixture of organic and inorganic components. Furthermore. the similarity between the colloidal metal:Al ratios with the crustal ratios indicated that colloids could be the product of weathering processes or particle resuspension. Distribution coefficients for colloidal particles (K-c) and for large, filter-retained particles (K-d) were of the same magnitude, suggesting similar binding strength for the two types of particles. Also, the dependence of the distribution coefficients on the amount of suspended particulate matter(the so-called particle concentration effect) was still evident for the colloids-corrected distribution coefficient (K-p+c) and for metals (e.g., Ni) without affinity for colloidal particles.

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