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Metal behaviour in an estuary polluted by acid mine drainage: the role of particulate matter

Metal behaviour in an estuary polluted by acid mine drainage: the role of particulate matter
Metal behaviour in an estuary polluted by acid mine drainage: the role of particulate matter
The concentrations of dissolved and suspended particulate Cd, Cu and Zn have been determined in water samples obtained during two axial transects of the Rio Tinto-Huelva Ria system in south-west Spain, which is severely impacted by acid mine drainage. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and, in the upper estuary, constituted >99% of total metal in the water column. Dissolved metals behaved non-conservatively on each transect, with maximum concentrations in the low salinity region. There was no evidence of metal adsorption within the turbidity maximum zone, despite the high specific surface areas of resuspending particles. Measurements of electrophoretic mobility showed that the suspended particulate matter (SPM) had a positive surface charge in the salinity range 0–4, where the waters had a pH<3. Desorption experiments were carried out in which SPM from the turbidity maximum zone was resuspended in coastal seawater. The desorption of the metals was monitored for 24 h, using anodic stripping voltammetry (ASV) to detect the variation in total dissolved Cd, Cu and Zn and the species of Cu and Zn. Total dissolved Cd concentrations doubled during the incubation period, whereas the concentration of total dissolved Cu declined and that of Zn remained rather constant. The ASV-labile fraction of dissolved Cu and Zn showed an initial sharp release followed by a slower uptake. However, desorption was shown to be a minor source of dissolved metals and made little contribution to the non-conservative behaviour in the low salinity zone. The results are used to predict the effects of acid mine drainage on estuarine ecology.
Estuary, Acid mine drainage, Metals, Distributions, Suspended particulate matter
0269-7491
283-292
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Braungardt, C.B.
e235ed81-73f5-4178-a4d2-577036c9cdab
Herzl, V.M.C.
95cbb338-0488-4606-805e-fd7fab83b51d
Millward, G.E.
723dc5eb-bbd3-463f-8485-4291c329f96b
Achterberg, E.P.
685ce961-8c45-4503-9f03-50f6561202b9
Braungardt, C.B.
e235ed81-73f5-4178-a4d2-577036c9cdab
Herzl, V.M.C.
95cbb338-0488-4606-805e-fd7fab83b51d
Millward, G.E.
723dc5eb-bbd3-463f-8485-4291c329f96b

Achterberg, E.P., Braungardt, C.B., Herzl, V.M.C. and Millward, G.E. (2003) Metal behaviour in an estuary polluted by acid mine drainage: the role of particulate matter. Environmental Pollution, 121, 283-292. (doi:10.1016/S0269-7491(02)00216-6).

Record type: Article

Abstract

The concentrations of dissolved and suspended particulate Cd, Cu and Zn have been determined in water samples obtained during two axial transects of the Rio Tinto-Huelva Ria system in south-west Spain, which is severely impacted by acid mine drainage. Although the metal concentrations in both phases were elevated, dissolved metals were dominant and, in the upper estuary, constituted >99% of total metal in the water column. Dissolved metals behaved non-conservatively on each transect, with maximum concentrations in the low salinity region. There was no evidence of metal adsorption within the turbidity maximum zone, despite the high specific surface areas of resuspending particles. Measurements of electrophoretic mobility showed that the suspended particulate matter (SPM) had a positive surface charge in the salinity range 0–4, where the waters had a pH<3. Desorption experiments were carried out in which SPM from the turbidity maximum zone was resuspended in coastal seawater. The desorption of the metals was monitored for 24 h, using anodic stripping voltammetry (ASV) to detect the variation in total dissolved Cd, Cu and Zn and the species of Cu and Zn. Total dissolved Cd concentrations doubled during the incubation period, whereas the concentration of total dissolved Cu declined and that of Zn remained rather constant. The ASV-labile fraction of dissolved Cu and Zn showed an initial sharp release followed by a slower uptake. However, desorption was shown to be a minor source of dissolved metals and made little contribution to the non-conservative behaviour in the low salinity zone. The results are used to predict the effects of acid mine drainage on estuarine ecology.

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More information

Published date: 2003
Keywords: Estuary, Acid mine drainage, Metals, Distributions, Suspended particulate matter

Identifiers

Local EPrints ID: 12538
URI: http://eprints.soton.ac.uk/id/eprint/12538
ISSN: 0269-7491
PURE UUID: ff070db4-ad38-4827-bda5-6ae0bbaa50e6

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Date deposited: 26 Nov 2004
Last modified: 15 Mar 2024 05:06

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Contributors

Author: E.P. Achterberg
Author: C.B. Braungardt
Author: V.M.C. Herzl
Author: G.E. Millward

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