Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - In situ speciation measurements of trace metals in headwater streams
AU - Warnken, Kent
AU - Lawlor, Alan J.
AU - Lofts, Stephen
AU - Tipping, Edward
AU - Davison, William
AU - Zhang, Hao
PY - 2009
Y1 - 2009
N2 - Concentrations of Al, Fe, Mn, Ni, Cu, Cd, Pb, and Zn were measured using DGT (diffusive gradients in thin-films) devices deployed in situ in 34 headwater streams in Northern England.Mean values of filtered samples analyzed by ICP-MS (inductively coupled plasma mass spectrometry) were used, along with DOC (dissolved organic carbon), pH and major ions, to calculate the distribution of metal species using the speciation code WHAM. DGT-measured concentrations, [Me]DGT, of Zn and Cd were generally similar to concentrations in filtered samples, [Me]filt. For the other metals, [Me]DGT was similar to or lower than [Me]filt. Calculation of the maximum dynamic metal from the speciation predicted usingWHAM showed that most of the lower values of [Cu]DGT could be attributed to the dominance of Cu-fulvic acid complexes, which diffuse more slowly than simple inorganic species. Similar calculations for Al, Pb, and Mnwere consistent with appreciable proportions of these metals being present as colloids that are not simple complexes withhumic substances. Differences betweenWHAMpredictions and the measured [Ni]DGT indicated that WHAM used with the default binding parameters underestimates Ni binding to natural organic matter. Plots of [Me]DGT versus the ratio of bound metal to DOC provided slight evidence of heterogeneous bindingof Pb and Cu, while results for Mn, Cd, and Zn were consistent with weak binding and complete lability.
AB - Concentrations of Al, Fe, Mn, Ni, Cu, Cd, Pb, and Zn were measured using DGT (diffusive gradients in thin-films) devices deployed in situ in 34 headwater streams in Northern England.Mean values of filtered samples analyzed by ICP-MS (inductively coupled plasma mass spectrometry) were used, along with DOC (dissolved organic carbon), pH and major ions, to calculate the distribution of metal species using the speciation code WHAM. DGT-measured concentrations, [Me]DGT, of Zn and Cd were generally similar to concentrations in filtered samples, [Me]filt. For the other metals, [Me]DGT was similar to or lower than [Me]filt. Calculation of the maximum dynamic metal from the speciation predicted usingWHAM showed that most of the lower values of [Cu]DGT could be attributed to the dominance of Cu-fulvic acid complexes, which diffuse more slowly than simple inorganic species. Similar calculations for Al, Pb, and Mnwere consistent with appreciable proportions of these metals being present as colloids that are not simple complexes withhumic substances. Differences betweenWHAMpredictions and the measured [Ni]DGT indicated that WHAM used with the default binding parameters underestimates Ni binding to natural organic matter. Plots of [Me]DGT versus the ratio of bound metal to DOC provided slight evidence of heterogeneous bindingof Pb and Cu, while results for Mn, Cd, and Zn were consistent with weak binding and complete lability.
UR - http://www.scopus.com/inward/record.url?scp=70349611513&partnerID=8YFLogxK
U2 - 10.1021/es900112w
DO - 10.1021/es900112w
M3 - Journal article
AN - SCOPUS:70349611513
VL - 43
SP - 7230
EP - 7236
JO - Environmental Science and Technology
JF - Environmental Science and Technology
SN - 0013-936X
IS - 19
M1 - 43
ER -