Denitrification and Organic Carbon Availability in Two Aquifers

Nitrate is one of the most common ground-water contaminants, and denitrification, the bacterially mediated conversion of nitrate into molecular nitrogen, is the only geochemical process that contributes significantly to the renovation of nitrate-contaminated aquifers. Previous workers have shown that denitrification occurs in some, but not all, nitratecontaminated unconfined aquifers in southern Ontario, Canada. Denitrification tends to occur in aquifers that have a very shallow water table, but not in aquifers whose water table is deeper than about two to three meters. This paper describes an investigation of the importance of organic carbon in controlling the occurrence of denitrification in two shallow sandy aquifers in southern Ontario, Canada. In situ and laboratory measurements of denitrification rates using the acetylene block technique show that: (1) organic carbon availability decreases with depth below the ground surface; (2) denitrification occurs in an aquifer with a very shallow water table, but organic carbon availability limits the denitrification rate; and (3) denitrification does not occur in an aquifer with a deeper water table because there is insufficient labile organic carbon present.

[1]  Robert J. Miller,et al.  Nitrogen Balance in the Southern San Joaquin Valley 1 , 1976 .

[2]  R. Gillham,et al.  An integrated approach to hydrogeologic investigations — A case history , 1983 .

[3]  D. Keeney,et al.  Sources of Nitrate to Ground Water , 1986 .

[4]  Peter L. Churcher,et al.  Analysis of ancient sediments for total organic carbon - some new ideas , 1987 .

[5]  A. Mariotti,et al.  15N isotope biogeochemistry and natural denitrification process in groundwater: Application to the chalk aquifer of northern France , 1988 .

[6]  A. Hill.  Nitrate Distribution in the Ground Water of the Alliston Region of Ontario, Canada , 1982 .

[7]  K. Howard.  Denitrification in a major limestone aquifer , 1985 .

[8]  J. Morris,et al.  Potential denitrification rates in deep sediments from the southeastern coastal plain. , 1988, Environmental science & technology.

[9]  S. Korom.  Natural denitrification in the saturated zone: a review , 1992 .

[10]  W. Edmunds,et al.  The Lincolnshire Limestone — Hydrogeochemical evolution over a ten-year period , 1983 .

[11]  C. Kreitler.  Nitrogen-isotope ratio studies of soils and groundwater nitrate from alluvial fan aquifers in Texas☆ , 1979 .

[12]  R. Markel,et al.  Sources of Nitrate in Ground Water in a Sewered Housing Development, Central Long Island, New York , 1984 .

[13]  Kevin J. Boyle,et al.  Benefit transfer studies: Myths, pragmatism, and idealism , 1992 .

[14]  R. Mccready,et al.  Distribution, source and evolution of nitrate in a glacial till of southern Alberta, Canada , 1984 .

[15]  John A. Cherry,et al.  Migration of contaminants in groundwater at a landfill: A case study: 2. Groundwater monitoring devices , 1983 .

[16]  J. Gilliam,et al.  Riparian Losses of Nitrate from Agricultural Drainage Waters , 1985 .

[17]  Roy F. Spalding,et al.  Sources and Concentrations of Nitrate‐Nitrogen in Ground Water of the Central Platte Region, Nebraskaa , 1979 .

[18]  O. Strebel,et al.  Denitrifikation in einem reduzierenden Grundwasserleiter , 1983 .

[19]  R. E. Jackson,et al.  Oxidation–reduction sequences in ground water flow systems , 1979 .

[20]  J. Costerton,et al.  Heterotrophic activity and biodegradation of labile and refractory compounds by groundwater and stream microbial populations , 1982, Applied and environmental microbiology.

[21]  F. Chapelle,et al.  Bacteria in deep coastal plain sediments of Maryland: A possible source of CO2 to groundwater , 1987 .

[22]  W. Payne,et al.  Blockage by acetylene of nitrous oxide reduction in Pseudomonas perfectomarinus , 1976, Applied and environmental microbiology.