Occurrence and behaviour of trace metals in coastal waters of Bermuda, and chromium in the Sargasso Sea
Occurrence and behaviour of trace metals in coastal waters of Bermuda, and chromium in the Sargasso Sea
The distribution of the dissolved and particulate forms of the trace metals, cadmium, copper, lead, manganese and nickel were investigated in the coastal waters of Bermuda over a 3-4 year period; together with salinity, temperature and the nutrients nitrate, nitrite and phosphorus. Trace metal concentrations were determined in the predominantly calcareous sediments of the inshore areas of Bermuda. A selective extraction technique was used to assess the environmental mobility of the metals in the sediments.
Concentration of trace metals in the waters and sediments are generally elevated in the enclosed harbour areas which have high human populations. The concentrations of metals are elevated with respect to the offshore Sargasso Sea water that exchanges with the coastal waters, concentrations of cadmium range from 0.1-2.4 nmol 1-1, copper 0.42-60 nmol 1-1, lead 0.03-3.5 nmol 1-1, manganese 0.3-40 nmol 1-1 and nickel 0.45-14 nmol 1-1.
Most of the metals in the sediments were associated with the non-labile, presumably organic fraction of the sediments. However lead and manganese were associated with the labile fraction of the sediments. An in-depth study of Devil's Hole; a 24m deep basin in Harrington Sound which has a seasonal thermocline, and subsequent anoxia, was undertaken. Results from this study indicated that there was release of dissolved manganese across the anoxic/oxic interface. Reduced manganese was rapidly oxidised to the particulate material in the oxic water column. Data indicated that the sediments can readily release cadmium under both oxic and anoxic conditions. The concentrations of cadmium in St. George's Harbour are found to be elevated with respect to other stations and previous work in the same area.
Inputs of cadmium into the Bermuda coastal zone were found to be from diffuse sources; copper from anti-fouling compound on boats; lead, manganese and nickel showed a strong associated with run-off during rain events.
A study of the seasonal trends in the distributions of the metals was performed. Some evidence for seasonal factors was cadmium and manganese, the other metals exhibited no evidence of seasonal trends.
University of Southampton
Connelly, Douglas Patrick
40a2493b-363e-4e19-8302-419d0a6e5cdd
1997
Connelly, Douglas Patrick
40a2493b-363e-4e19-8302-419d0a6e5cdd
Connelly, Douglas Patrick
(1997)
Occurrence and behaviour of trace metals in coastal waters of Bermuda, and chromium in the Sargasso Sea.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The distribution of the dissolved and particulate forms of the trace metals, cadmium, copper, lead, manganese and nickel were investigated in the coastal waters of Bermuda over a 3-4 year period; together with salinity, temperature and the nutrients nitrate, nitrite and phosphorus. Trace metal concentrations were determined in the predominantly calcareous sediments of the inshore areas of Bermuda. A selective extraction technique was used to assess the environmental mobility of the metals in the sediments.
Concentration of trace metals in the waters and sediments are generally elevated in the enclosed harbour areas which have high human populations. The concentrations of metals are elevated with respect to the offshore Sargasso Sea water that exchanges with the coastal waters, concentrations of cadmium range from 0.1-2.4 nmol 1-1, copper 0.42-60 nmol 1-1, lead 0.03-3.5 nmol 1-1, manganese 0.3-40 nmol 1-1 and nickel 0.45-14 nmol 1-1.
Most of the metals in the sediments were associated with the non-labile, presumably organic fraction of the sediments. However lead and manganese were associated with the labile fraction of the sediments. An in-depth study of Devil's Hole; a 24m deep basin in Harrington Sound which has a seasonal thermocline, and subsequent anoxia, was undertaken. Results from this study indicated that there was release of dissolved manganese across the anoxic/oxic interface. Reduced manganese was rapidly oxidised to the particulate material in the oxic water column. Data indicated that the sediments can readily release cadmium under both oxic and anoxic conditions. The concentrations of cadmium in St. George's Harbour are found to be elevated with respect to other stations and previous work in the same area.
Inputs of cadmium into the Bermuda coastal zone were found to be from diffuse sources; copper from anti-fouling compound on boats; lead, manganese and nickel showed a strong associated with run-off during rain events.
A study of the seasonal trends in the distributions of the metals was performed. Some evidence for seasonal factors was cadmium and manganese, the other metals exhibited no evidence of seasonal trends.
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Published date: 1997
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Local EPrints ID: 463082
URI: http://eprints.soton.ac.uk/id/eprint/463082
PURE UUID: d19ca1cc-4274-42d4-a2db-24a5fd357a78
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Date deposited: 04 Jul 2022 20:44
Last modified: 16 Mar 2024 19:01
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Author:
Douglas Patrick Connelly
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