Land–sea mercury transport through a modified watershed, SE Brazil

River management has altered the land–sea transport of water, sediments, and chemical compounds with profound impacts on the structure of continental and costal ecosystems. Understanding riverine transport across modified watersheds allow for better assessment of the influence of river management on...

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Bibliographic Details
Published in:Water research (Oxford) 2007-05, Vol.41 (9), p.1929-1938
Main Authors: Molisani, Mauricio Mussi, Kjerfve, Björn, Barreto, Renata, Drude de Lacerda, Luiz
Format: Article
Language:English
Subjects:
Applied sciences
Brackish
Brazil
chemical concentration
chemical speciation
Dams
emissions
Exact sciences and technology
Freshwater
geographical variation
Geologic Sediments - analysis
Geologic Sediments - chemistry
heavy metals
Mass balance
Mercury
Mercury - analysis
Other industrial wastes. Sewage sludge
Paraíba do Sul River
Pollution
rivers
Rivers - chemistry
Seawater
sediments
Sepetiba Bay
soil erosion
Transport
Wastes
Water diversion
water management
Water Movements
water pollution
water quality
Water Supply
Water treatment and pollution
watersheds
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Summary:River management has altered the land–sea transport of water, sediments, and chemical compounds with profound impacts on the structure of continental and costal ecosystems. Understanding riverine transport across modified watersheds allow for better assessment of the influence of river management on material fluxes to coastal waters. Here, we assess the quantitative and qualitative aspects of mercury (Hg) transport across a modified watershed by diversion of Paraíba do Sul River waters into Sepetiba Bay, Brazil. We measured concentrations and speciation of Hg in water samples collected at sites within the modified watershed. These data, together with water discharge and sediment load from numerical models and measurements were used to estimate mass balances. In the Sepetiba watershed, mercury is mainly associated with suspended sediments (90%) and therefore Hg flux displayed the characteristic trend of downstream reduction due to trapping efficiency of particulate load by successive reservoirs. The mass balance suggests that the major source of mercury to Sepetiba Bay is the erosion of soil-derived particles from the drainage basin rather than mercury diverted from Paraíba do Sul River watershed.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2007.02.007