Abstracts Biological Sciences

Field testing of a biological system for reducing nitrate pollution

by Marc-David. Andrade

The overall goal of this study was to investigate the possibility of reducing NO3 – concentration in the lower soil horizon by promoting denitrification. The study looked at an inexpensive remediation practice for subsurface-drained fields in order to degrade N0j' and consequently diminish NO3 – pollution. The experiments were conducted on a corn field at the Macdonald Campus Farm. The field was composed of sandy loam soil underlined by a clay layer. In this study, sucrose was injected at a concentration of 20 mg L  – 1 within the subirrigation water. Furthermore, the water table was maintained at approximately 70 cm from the soil surface in order to create an anaerobic environment that allows for denitrification. The purpose was to furnish dissolved organic carbon (DOC) to the resident microorganisms in order to carryout a higher amount of denitrification. The NO3 – levels in ground water were monitored weekly. Gas samples were taken from the field to observe whether N2O emissions increased as a result of the treatment This was considered to be important since N2O is a greenhouse gas. It was found that the addition of sucrose significantly resulted in a faster rate of denitrification. The higher biological activity severely damped the NO3 – peaks in the subsoil, which arose following major rainfall events. The addition of sucrose at 20 mg L – 1 was found to be significant in lowering the amounts of released N2O. Therefore, adding DOC in the subirrigation water not only helped remediate water contamination but also served as a remedy to atmospheric pollution. In addition, the hydraulic conductivity of the soil was monitored to ensure that no bioclogging arose from an anticipated rise in the bacterial population due to the addition of sucrose. It was found that the addition of sucrose at 20 mg L – 1 did not contribute in anyway to reduce the soil's hydraulic conductivity.