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Transport and reduction of nitrate in clayey till underneath forest and arable land.

Jørgensen, P.R.; Urup, J.; Helstrup, T.; Jensen, M.B.; Eiland, F. and Vinther, F.P. (2004) Transport and reduction of nitrate in clayey till underneath forest and arable land. Journal of Contaminant Hydrology, 73, pp. 207-226.

[thumbnail of Jørgensen,_Urup,_Helstrup,_Jensen,_Eiland_&_Vinther_2004.pdf] PDF - English


Transport and reduction of nitrate in a typically macroporous clayey till were examined at variable flow rate and nitrate flux. The experiments were carried out using saturated, large diameter (0.5 m), undisturbed soil columns (LUC), from a forest and nearby agricultural sites. Transport of nitrate was controlled by flow along the macropores (fractures and biopores) in the columns. Nitrate reduction (denitrification) determined under active flow mainly followed first order reactions with half-lives (t1/2) increasing with depth (1.5–3.5 m) from 7 to 35 days at the forest site and 1–7 h at the agricultural site. Nitrate reduction was likely due to microbial degradation of accumulated organic matter coupled with successive consumption of O2 and NO3− in the macropore water followed by reductive dissolution of Fe and Mn from minerals along the macropores. Concentrations of total organic carbon measured in soil samples were near identical at the two study sites and consequently not useful as indicator for the observed differences in nitrate reduction. Instead the high reduction rates at the agricultural site were positively correlated with elevated concentration of water-soluble organic carbon and nitrate-removing bacteria relative to the forest site. After high concentrations of water-soluble organic carbon in the columns from the agricultural site were leached they lost their elevated reduction rates, which, however, was successfully re-established by infiltration of new reactive organics represented by pesticides. Simulations using a calibrated discrete fracture matrix diffusion (DFMD) model could reasonably reproduce the denitrification and resulting flux of nitrate observed during variable flow rate from the columns.

EPrint Type:Journal paper
Keywords:Transport, Reduction, Nitrate, Clayey till, Forest and arable land
Subjects: Soil > Nutrient turnover
Environmental aspects > Air and water emissions
Research affiliation: Denmark > DARCOF II (2000-2005) > I.16 (OKOVAND) Regional groundwater protection by optimised organic farming systems
Denmark > Other organizations
Related Links:http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V94-4CVX4R1-1-N&_cdi=5888&_orig=browse&_coverDate=09%2F30%2F2004&_sk=999269998&view=c&wchp=dGLbVlb-zSkWA&_acct=C000033598&_version=1&_userid=635791&md5=58fa8bf6d10d26b4833bf16e17c37eb2&ie=f.pdf
Deposited By: Vinther, Senior scientist Finn P.
ID Code:3373
Deposited On:30 Sep 2004
Last Modified:06 Jun 2011 12:25
Document Language:English
Refereed:Peer-reviewed and accepted

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