SEASONAL PATTERN OF N2O CONCENTRATIONS AND EMISSIONS IN THE SEWAGE-ENRICHED RIVERS: CASE OF CHAOHU LAKE BASIN IN SOUTHEAST CHINA

Abstract

Two sewage-enriched urban rivers within Chaohu Lake Basin in Southeast China were selected to study the seasonal variations in Nitrous Oxide (N2O) concentrations, to improve the information of N2O concentrations and emissions in the similar areas. The results indicate that N2O concentrations ranged 16.12~1043.09 nmol/L and averaged 266.27 ± 250.28 nmol/L during the sampling period. N2O was oversaturated in both rivers ranging 184~12084% (mean 2964%). The significantly higher level of N2O concentrations and emissions were observed in cold months. It is indicated that the two rivers were net sources of atmospheric N2O. N2O emissions ranged 11.32~2920.38 μg N-N2O/m/h with an overall mean value of 743.57 ± 831.78 μg N-N2O/m/h. A significant negative correlation exists between N2O concentration and water temperature, which may be regulated by inverse tendencies between temperature and riverine nutrient loadings. Dissolved Oxygen (DO) is a predictor of N2O in Nanfei River explaining 60% of variability in N2O; while water temperature and NO3 are better predictors of N2O in Ershibu River explaining 73% of variability in N2O. The riverine N2O may be produced by denitrification in Nanfei River while by coupled nitrification-denitrification in Ershibu River.