Premium
Organic complexation of copper in surface waters of Galveston Bay
Author(s) -
Tang Degui,
Warnken Kent W.,
Santschi Peter H.
Publication year - 2001
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2001.46.2.0321
Subject(s) - cathodic stripping voltammetry , chemistry , ultrafiltration (renal) , fraction (chemistry) , seawater , colloid , ligand (biochemistry) , copper , salinity , sulfur , environmental chemistry , inorganic chemistry , chromatography , voltammetry , electrochemistry , organic chemistry , oceanography , biochemistry , receptor , electrode , geology
The importance of colloidal ligands in the organic complexation of Cu was elucidated in the estuarine waters of Galveston Bay by use of a number of instrumental techniques. Ultrafiltration was conducted to isolate the ultra‐permeate fraction from the filter‐passing fraction and competitive ligand equilibration/adsorptive cathodic stripping voltammetry measurements were conducted by use of varying amounts of catechol as the competitive ligand. Greater than 99.9% of Cu was bound by strong organic ligands with log[K′ (M −1 )] values of 12.3 ± 0.15 and 11.1 ± 0.29 in the filter‐passing and ultrapermeate fractions, respectively. The concentrations of Cu complexing ligands were lower in the ultrapermeate than in the filter‐passing fraction, and the calculated K9 values for the colloidal ligands (log K′ = 12.9) were 60 times greater than those for the ultrapermeate fraction, suggesting that good separation of the colloidal fraction during ultrafiltration was achieved. Total Cu concentrations in the filter‐passing fraction ranged from 2.27 to 12.9 nM and were fairly constant at salinity <20 but decreased at salinity ≫20. The calculated free Cu concentrations (0.05–0.49 pM) showed an overall increasing trend with salinity, possibly resulting from decreasing concentrations of Cu complexing ligands toward the seawater endmember. The concentration of Cu complexing ligands (21–54 nM) in the estuarine regions of Galveston Bay was approximately equal to the concentration of total reduced sulfur species (20–60 nM) in the filter‐passing fraction, suggesting that reduced sulfur species could account for most of the Cu‐complexing ligands in these waters.