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

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