Document Detail


Selenium removal and mass balance in a constructed flow-through wetland system.
MedLine Citation:
PMID:  12931913     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A field study on the removal of Se from agricultural subsurface drainage was conducted from May 1997 to February 2001 in the Tulare Lake Drainage District (TLDD) of San Joaquin Valley, California. A flow-through wetland system was constructed consisting of ten 15- x 76-m unlined cells that were continuously flooded and planted with either a monotype or combination of plants, including sturdy bulrush [Schoenoplectus robustus (Pursh) M.T. Strong], baltic rush (Juncus balticus Willd.), smooth cordgrass (Spartina alterniflora Loisel.), rabbitsfoot grass [Polypogon monspeliensis (L.) Desf.], salt-grass lDistichlis spicata (L.) Greene], cattail (Typha latifolia L.), tule [Schoenoplectus acutus (Muhl. ex Bigelow) A. Löve & D. Löve], and widgeon grass (Ruppia maritima L.). One cell had no vegetation planted. The objectives of this research were to evaluate Se removal efficiency of each wetland cell and to carry out a mass balance on Se. The inflow drainage water to the cells had average annual Se concentrations of 19 to 22 microg L(-1) dominated by selenate [Se(VI), 95%]. Average weekly water residence time varied from about 3 to 15 d for Cells 1 through 7 (target 7 d), 19 to 33 d for Cells 8 and 9 (target 21 d), and 13 to 18 d for Cell 10 (target 14 d). Average weekly Se concentration ratios of outflow to inflow ranged from 0.45 to 0.79 and mass ratio (concentration x water volume) from 0.24 to 0.52 for year 2000, that is, 21 to 55% reduction in Se concentration and 48 to 76% Se removal in mass by the wetland, respectively. The nonvegetated cell showed the least Se removal both in concentration and in mass. The global mass balance showed that on the average about 59% of the total inflow Se was retained within the cells and Se outputs were outflow (35%), seepage (4%), and volatilization (2%). Independent measurements of the Se retained in the cells totaled 53% of the total Se inflow: 33% in the surface (0-20 cm) sediment, 18% in the organic detrital layer above the sediment, 2% in the fallen litter, < 1% in the standing plants, and < 1% in the surface water. Thus, about 6% of the total Se inflow was unaccounted for in the internal compartments.
Authors:
S Gao; K K Tanji; Z Q Lin; N Terry; D W Peters
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of environmental quality     Volume:  32     ISSN:  0047-2425     ISO Abbreviation:  J. Environ. Qual.     Publication Date:    2003 Jul-Aug
Date Detail:
Created Date:  2003-08-22     Completed Date:  2003-11-06     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0330666     Medline TA:  J Environ Qual     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1557-70     Citation Subset:  IM    
Affiliation:
Dep. of Land, Air and Water Resources, Univ. of California, One Shields Ave., Davis, CA 95616, USA. sugao@ucdavis.edu
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MeSH Terms
Descriptor/Qualifier:
Agriculture
Disasters
Ecosystem*
Environmental Monitoring
Filtration
Geologic Sediments / chemistry
Models, Theoretical*
Poaceae
Selenium / isolation & purification*
Water Movements
Water Purification / methods*
Water Supply
Chemical
Reg. No./Substance:
7782-49-2/Selenium

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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