Upflow reactors for riparian zone denitrification.
We used permeable reactive subsurface barriers consisting of a C source (wood particles), with very high hydraulic conductivities ( approximately 0.1-1 cm s(-1)), to provide high rates of riparian zone NO3-N removal at two field sites in an agricultural area of southwestern Ontario. At one site, a 0.73-m3 reactor containing fine wood particles was monitored for a 20-mo period and achieved a 33% reduction in mean influent NO3-N concentration of 11.5 mg L(-1) and a mean removal rate of 4.5 mg L(-1) d(-1) (0.7 g m(-2) d(-1)). At the second site, four smaller reactors (0.21 m3 each), two containing fine wood particles and two containing coarse wood particles, were monitored for a 4-mo period and were successful in attenuating mean influent NO3-N concentrations of 23.7 to 35.1 mg L(-1) by 41 to 63%. Mean reaction rates for the two coarse-particle reactors (3.2 and 7.8 mg L(-1) d(-1), or 1.5 and 3.4 g m(-2) d(-1)) were not significantly different (p > 0.2) than the rates observed in the two fine-particle reactors (5.0 and 9.9 mg L(-1) d(-1), or 1.8-3.5 g m(-2) d(-1)). A two-dimensional ground water flow model is used to illustrate how permeable reactive barriers such as these can be used to redirect ground water flow within riparian zones, potentially augmenting NO3- removal in this environment.
van Driel
Peter W
PW
Department of Earth Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON, Canada.
Robertson
William D
WD
Merkley
L Craig
LC
D000383:Agriculture; D001673:Biodegradation, Environmental; D019149:Bioreactors; D008962:Models, Theoretical; D009566:Nitrates / Q000302:isolation & purification* / Q000378:metabolism; D009584:Nitrogen; D045483:Rivers; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000302:isolation & purification* / Q000378:metabolism; D018508:Water Purification / Q000379:methods*; D014881:Water Supply; D014934:Wood
D009566:Nitrates; D014874:Water Pollutants, Chemical; D009584:Nitrogen