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Titolo:
PHYSICOCHEMICAL SPECIATION OF LEAD IN SOUTH SAN-FRANCISCO BAY
Autore:
KOZELKA PB; SANUDOWILHELMY S; FLEGAL AR; BRULAND KW;
Indirizzi:
UNIV CALIF SANTA CRUZ,DEPT CHEM & BIOCHEM SANTA CRUZ CA 95064 SUNY STONY BROOK,MARINE SCI RES CTR STONY BROOK NY 11794 UNIV CALIF SANTA CRUZ,INST MARINE SCI SANTA CRUZ CA 95064
Titolo Testata:
Estuarine, coastal and shelf science
fascicolo: 6, volume: 44, anno: 1997,
pagine: 649 - 658
SICI:
0272-7714(1997)44:6<649:PSOLIS>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
NATURAL RIVER WATER; AQUATIC COLLOIDS; METAL SPECIATION; COASTAL DIATOM; SURFACE WATERS; UNITED-STATES; TRACE-METALS; ION ACTIVITY; FRESH-WATER; COPPER;
Keywords:
LEAD; SPECIATION; ULTRAFILTRATION; ELECTROCHEMISTRY; ORGANIC COMPLEXATION; TRACE METALS; SAN FRANCISCO BAY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
46
Recensione:
Indirizzi per estratti:
Citazione:
P.B. Kozelka et al., "PHYSICOCHEMICAL SPECIATION OF LEAD IN SOUTH SAN-FRANCISCO BAY", Estuarine, coastal and shelf science, 44(6), 1997, pp. 649-658

Abstract

The speciation of lead at a site in the South San Francisco Bay was determined using a combination of physical size fractionation and electrochemical analyses. The total dissolvable' Pb was 8.1 nM from analysis of an acidified unfiltered sample. The 'dissolved' Pb was equal to 0.20 nM (41 ng l(-1)), only 2.5% of the 'total dissolvable' Pb. The difference yielded the 'particulate' Pb equal to 7.9 nM (1.6 mu g l(-1)). Results from crossflow ultrafiltration indicated that almost all (0.19 nM) of the dissolved Pb was 'in solution' [<10K nominal molecular weight (MW)] and that colloidal Pb (10K MW to 0.2 mu m) accounted for only c. 1% of the dissolved Pb at this station. This small concentration(0.01 nM) of colloidal Pb may be attributed to the low amount of organic carbon associated with colloid size fraction as determined by dissolved organic carbon analyses. The chemical speciation of lead was determined in the dissolved sample and ultrafiltered sub-sample. Differential pulse anodic stripping voltammetry (DPASV) on a thin mercury film(TMF) rotating glassy carbon disk electrode (RGCDE) was used to distinguish the kinetically labile inorganic species (Pb') from the Pb-chelated by organic ligands (PbLi). Lead tetration results were similar for both samples revealing that Pb', PbLi and excess unbound ligands were present primarily in the ultrafiltrate, rather than in the colloidalphase. The titration data can be interpreted as dissolved Pb being influenced by two classes of Pb-binding ligands. In the dissolved sample, the concentration of the stronger class of ligands was [L-1] = 0.89 /- 0.35 nM, with a conditional stability constant K-L1,Pb'(cond) = 3 /- 1 x 10(10) M-1. The weaker class was [L-2] = 12.8 +/- 1.9 nM, withK-L1,Pb'(cond) = 4 +/- 1 x 10(8) M-1. The presence of these ligands, in excess of the dissolved Pb, resulted in [Pb'] = 7 +/- 2 pM and [Pb2] = 0.3 pM (62 pg l(-1)). While less than 2.4% of the ambient Pb was 'in solution', it existed chiefly in the form of organic complexes with [PbL1] = 0.5 nM and [PbL2] = 0.03 nM. More significantly, there werelarge concentrations of unchelated Pb-binding ligands (L-i'), available to buffer the free Pb2+ concentration in the event of perturbationsin dissolved Pb. (C) 1997 Academic Press Limited.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 26/09/20 alle ore 12:52:37