Seasonal variations in the behaviour of particle reactive heavy metals in Loch Etive, a fjordic estuary on the West Coast of Scotland, have been investigated using the natural radioactive tracers <SUP>210</SUP>Pb, <SUP>210</SUP>Po and <SUP>234</SUP> Th. A multi-sample (water column samples; sediment traps; short sediment cores) time-series (monthly sampling for eighteen months) study is reported for one station in a stagnant, 140 m deep, basin. In all water samples the distinction between particulate and dissolved was made by filtering through 0.45μm filters. Emphasis has been placed on assessing the post-depositional mobility of Pb in organic-rich, high sedimentation-rate, coastal sediments. There was no renewal of the water in the deep basin during the study period, and the dissolved oxygen concentration gradually fell, to ~2.4 ml<SUP>-1</SUP>. River and rainwater samples were analysed for <SUP>210</SUP>Pb and <SUP>210</SUP>Po in order to determine their input fluxes into Loch Etive. The mean particulate, dissolved and total <SUP>210</SUP>Pb riverine concentrations were 0.43±0.33, 1.14±0.93 and 1.30±1.09 Bq m<SUP>-3</SUP> respectively. The similar <SUP>210</SUP>Po concentrations were 1.77±1.39, 2.60±0.93 and 4.21±3.01 Bq m<SUP>-3</SUP> respectively. The total riverine <SUP>210</SUP>Pb and <SUP>210</SUP>Po flux, averaged over the whole surface of Loch Etive, was 149±125 and 483±345 Bq m<SUP>-2</SUP> year<SUP>-1</SUP> respectively. The mean rainwater total <SUP>210</SUP>Pb and <SUP>210</SUP>Po activities of 53.8±15.2 and 97.5±107 Bq m<SUP>-3</SUP> respectively, result in mean depositional fluxes to Loch Etive of 118±33.5 and 214±235 Bq m<SUP>-2</SUP> year<SUP>-1</SUP> respectively. The relative importance of the riverine input reflects Loch Etive's large catchment area (~2000 km<SUP>3</SUP>). Water column particulate, dissolved and total <SUP>210</SUP>Pb and <SUP>210</SUP>Po concentrations were determined monthly for 17 months. The dissolved/particulate ratio was close to unity, which reflects the large concentration of particulate material in coastal samples. The surface (0-10 m) concentrations, varied greatly, dependent on the amount of run-off in the weeks prior to sampling. The intermediate (10-60 m) and deep (60-120 m) water concentrations were more constant, with <SUP>210</SUP>Pb particulate, dissolved and total means: 0.17±0.09, 0.18±0.14 and 0.36±0.20 Bq m<SUP>-3 </SUP>respectively. The corresponding <SUP>210</SUP>Po means were: 0.15±0.07, 0.27±0.19 and 0.42±0.20 Bq m<SUP>-3</SUP> respectively.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:664171 |
| Date | January 1996 |
| Creators | Young, Stuart Andrew |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/11656 |
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