Title: Removal, distribution and retention of metals in a constructed wetland over 20 years

Abstract

The A-01 wetland treatment system (WTS) was designed to remove metals (primarily copper) from the effluent at the A-01 National Pollution Discharge Elimination System (NPDES) outfall at the Savannah River Site, Aiken, SC. This research investigated metal removal, distribution and retention in the A-01 WTS over a period of 20 years. The findings are important for ensuring continued metal sequestration in the A-01 WTSs over time, providing management guidance for constructed wetlands, and investigating changes in metal remediation effectiveness as a wetland ages. During 20 years of operation, systematic water and sediment sampling validated the wetlands' performance. After passage through the treatment cells, Cu concentrations were well below permit limits during all years of operation, often falling below 10 μg L^-1. Cu removal has been consistent over time, averaging about 80% despite large changes in influent Cu concentrations. Most divalent metals were rapidly removed from the water and held in the sediments shortly after the water entered the treatment wetland. Average removal of Pb from water by the wetland system was 67 and 74% in 2004 and 2020, respectively. Comparable values for Zn were 52 and 65%, respectively. Generally, the highest concentrations of Cu, Pb, and Zn were found inmore » the sediment from the first cell in each pair of cells suggesting that most of the Cu, Pb, and Zn in the A-01 effluent was bound to the sediment quickly. Diffusive gradients in thin films (DGT) measurements of Cu and Zn in the sediments were much lower than bulk sediment concentrations. These results suggest that most of the Cu and Zn in the A-01 WTS sediments was not bioavailable, hence not toxic to aquatic organisms, as a likely consequence of adsorption to sediment particles and complexation with organic and inorganic substances.« less

Authors:

Knox, Anna Sophia ^[1]; Paller, Michael H. ^[1]; Seaman, John C. ^[2]; Mayer, John ^[1]; Nicholson, Cher ^[2]

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+ Show Author Affiliations

1. Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)
2. Savannah River Site (SRS), Aiken, SC (United States). Savannah River Ecology Lab. (SREL)

Publication Date:

Thu Jul 15 00:00:00 EDT 2021

Research Org.:

Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

Sponsoring Org.:

USDOE Office of Environmental Management (EM)

OSTI Identifier:

1838343

Report Number(s):

SRNL-L3210-2021-00001
Journal ID: ISSN 0048-9697; TRN: US2300987

Grant/Contract Number:  

89303321CEM000080

Resource Type:

Accepted Manuscript

Journal Name:

Science of the Total Environment

Additional Journal Information:

Journal Volume: 796; Journal ID: ISSN 0048-9697

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES