Factors Affecting Denitrification Rate in Barato Lake, Hokkaido, Japan

Article type: Research Article

Authors: Jha, Pawan Kumar | Masao, Minagawa

Affiliations: Graduate School of Environmental Science, Hokkaido University, Sapporo Hokkaido, Japan 060-0810. E-mail: findpawan@gmail.com

Abstract: We examined the sediment denitrification rate and factors affecting the denitrification in Barato lake, an eutrophic oxbow lake in lower Ishikari river basin. Denitrification rate was measured using acetylene inhibition technique on the sediment samples collected during August 2009 to July 2010. The sediment denitrification rate ranged from 0.13 to 2.21 μg N g^{-1}DMh^{-1} with an average of 0.91 μg N g^{-1} DM h^{-1} in Barato lake. Denitrification rate showed positive correlation with dissolved nitrate concentration of lake water, indicating that water column nitrate concentration control the sediment denitrification rate in Barato lake. Nutrient amended denitrification assay experiments showed that denitrification rate increased significantly with addition of nitrate regardless of sediment C content, while no significant variation was observed with addition of labile C (glucose). Temperature positively affected the rate of denitrification with five-fold increase in activity on increasing temperature from 5°C to 20°C. Nitrate controlled denitrification followed Michaelis-Menten kinetics with V_{max} as 2.65 μg N g^{-1} DM h^{-1} and K_m as 0.48 mg/l NO_3^--N. The value of K_m was comparable with other studies but was well below the median dissolved nitrate concentration (2.95 mg/l NO_3^--N) indicating that the process of denitrification was saturated in Barato lake.

Keywords: Barato lake, denitrification rate, Ishikari river, Michaelis-CMenten kinetics

Journal: Asian Journal of Water, Environment and Pollution, vol. 8, no. 3, pp. 1-10, 2011