Nitrous oxide concentration and nitrification and denitrification in Zhujiang River Estuary, China

The concentrations of nitrous oxide varies between 57 and 329 nmol/dm³, saturation is 674%~4 134% in the Zhujiang River Estuary.This suggests that the area is an emissive source of nitrous oxide. The acetylene inhibition technique is employed to evaluate the rates ofnitrification, denitrification and nitrate reduction by bacterial activities in the sediments at three sites. The average of nitrification,denitrification and nitrate reduction rates ranges from 0.32 to 2.43,0.03 to 0.84 and 4.17 to 13.06 mmol/(m²·h),respectively.The vertical profiles of the sediments show that the nitrification and denitrification processes mainly take place in the depth from 0 to 4 cm and depend on regional conditions. The rates of nitrification, denitrification and nitrate reduction are dominated by Eh, nitrate and ammonium concentrations in sediments and DO in overlay water. There is a coupling between nitrification and denitrification.