Persistence and mobility of metals in an estuarine environment 25years after closure of a lead smelter, Bahia State, Brazil

Persistence and mobility of metals in an estuarine environment 25years after closure of a lead... A part of the Subaé River watershed in Bahia, Brazil, is highly contaminated with toxic metals, due to a former 33-year lead (Pb)-smelting activity that produced approximately 500,000 tons of slag, primarily rich in Pb, Zn, and Cd. This study aimed at determining the remaining concentrations of trace metals, 25 years after the end of the metallurgic activities, in the continental sediments of the Subaé River upstream and downstream of the Pb smelter and in the estuarine mangrove sediments, which are 4 km away from the smelter. The river sediments were collected at five sites in the fluvial continental channel and at four sites in its estuary (channel and flood plain). Physicochemical analyses were performed, and pseudo-total Pb, Zn, Cd, and Cu were extracted by aqua regia. The impact of salinization of the fluvial environment by the rise in sea level was studied by batch tests in fresh and saline waters. Concentrations of Pb, Zn, and Cd were above the minimum alert threshold (35, 123, and 0.60 mg kg−1, respectively) at minimum two of the three sites downstream of the smelter (continental area). In the estuary, Cd exceeded the alert thresholds at five of the eight sites (0.68 mg kg−1), whereas few contamination of others metals was detected. The geoaccumulation index provided comparable conclusions. Conversely, the enrichment factors were found to be more applicable in such a variable environment: another source of pollution in the estuary was detected, with similar enrichment of Cu, Pb, and Zn, possibly the industrial facilities in the region. We calculated the enrichment of metals in the flood plain, compared it to the main channel of the estuary and concluded that Cd accumulates in flooded mangroves, while Pb remains in channel sediments. The batch tests proved that salinization of the river can release an average of 6, 20, and 60% of Pb, Zn, and Cd, respectively. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Environmental Earth Sciences Springer Journals

Persistence and mobility of metals in an estuarine environment 25years after closure of a lead smelter, Bahia State, Brazil

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2017 by Springer-Verlag GmbH Germany
Subject
Earth Sciences; Geology; Hydrology/Water Resources; Geochemistry; Environmental Science and Engineering; Terrestrial Pollution; Biogeosciences
ISSN
1866-6280
eISSN
1866-6299
D.O.I.
10.1007/s12665-017-6886-0
Publisher site
See Article on Publisher Site

Abstract

A part of the Subaé River watershed in Bahia, Brazil, is highly contaminated with toxic metals, due to a former 33-year lead (Pb)-smelting activity that produced approximately 500,000 tons of slag, primarily rich in Pb, Zn, and Cd. This study aimed at determining the remaining concentrations of trace metals, 25 years after the end of the metallurgic activities, in the continental sediments of the Subaé River upstream and downstream of the Pb smelter and in the estuarine mangrove sediments, which are 4 km away from the smelter. The river sediments were collected at five sites in the fluvial continental channel and at four sites in its estuary (channel and flood plain). Physicochemical analyses were performed, and pseudo-total Pb, Zn, Cd, and Cu were extracted by aqua regia. The impact of salinization of the fluvial environment by the rise in sea level was studied by batch tests in fresh and saline waters. Concentrations of Pb, Zn, and Cd were above the minimum alert threshold (35, 123, and 0.60 mg kg−1, respectively) at minimum two of the three sites downstream of the smelter (continental area). In the estuary, Cd exceeded the alert thresholds at five of the eight sites (0.68 mg kg−1), whereas few contamination of others metals was detected. The geoaccumulation index provided comparable conclusions. Conversely, the enrichment factors were found to be more applicable in such a variable environment: another source of pollution in the estuary was detected, with similar enrichment of Cu, Pb, and Zn, possibly the industrial facilities in the region. We calculated the enrichment of metals in the flood plain, compared it to the main channel of the estuary and concluded that Cd accumulates in flooded mangroves, while Pb remains in channel sediments. The batch tests proved that salinization of the river can release an average of 6, 20, and 60% of Pb, Zn, and Cd, respectively.

Journal

Environmental Earth SciencesSpringer Journals

Published: Aug 14, 2017

References

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