Seasonal Variation of Denitrification Rate in Estuary Sediments of Liaohe, China

The regulatory effects of environmental factors and denitrifying bacteria on denitrification were studied in the estuary sed iments of L ia oh e. Seasonal variation of denitrification rates over a one-year period were measured using the acetylene inhibition technique (AIT). Denitrification rates ranged at 2.4116.75 μmol/ (m²·h) in spring (May), 0.61113.14 μmol/ (m² ·h) in summer (August), and 2.11106.87 μmol/ (m²·h) in fall (November), indicating an apparent seasonal variation. Sediment denitrification rates were greatest in the spring and lowest in the summer and early autumn, primarily due to seasonal differences in nitrate concentration and water temperature. Of various environmental factors on denitrification that we assessed, nitrate was determined to be the key factor limiting denitrification rates in the sediments of Liaohe. In addition, at the two sites denitrification rates were also regulated by DO. Positive and linear relationships were regularly observed between denitrification rate and the number of denitrifying bacteria.