Studies on nitrobacteria and nitrification in Liaohe estuary wetland sediments

Nitrobacteria, nitrification and its impact factors were discussed based on the method of on-site incubation and laboratory simulation in Liaohe estuary wetland sediments in June and August 2009, respectively. The results showed that the number of ammonia-oxidizing bacteria (AOB) ranged from 0.54 x 10(4) to 5.69 x 10(4) cells x g(-1) with an average of (2.21 +/- 2.32) x 10(4) cells x g(-1) in June and ranged from 1.90 x 10(4) to 7.90 x 10(4) cells x g(-1) with an average of (3.61 +/- 2.87) x 10(4) cells x g(-1) in August. The potential nitrification rates ranged from 9.72 to 16.45 mmol x (m2 x h)(-1) with an average of (12.54 +/- 3.14) mmol x (m2 x h)(-1) in June and ranged from 14.66 to 24.62 mmol x (m2 x h)(-1) with an average of (18.71 +/- 4.21) mmol x (m2 x h)(-1) in August. The net nitrification rates were 0.41 mmol x (m2 x h)(-1) in June and ranged from 0.20 to 0.53 mmol x (m2 x h)(-1) with an average of (0.35 +/- 0.16) mmol x (m2 x h)(-1) in August. The potential nitrification rates were apparently higher than the net nitrification rates. The AOB abundance and nitrification rates were all higher in August than in June. Ammonia concentration in the overlying water, pH, organic matter, total nitrogen content, total phosphorus content, ammonia nitrogen content and the number of AOB in sediments were the main environmental impact factors on nitrification by SPSS 13.0 statistical analysis (p < 0.05), and it also showed ammonia concentration in the overlying water, total phosphorus content and ammonia nitrogen content in sediments were key impact factors on nitrification by partial correlation analysis. The flux of transformed ammonium into nitrate by nitrification process was 1.14 x 10(5) kg per day, suggesting that nitrification was important on nitrogen cycle in Liaohe estuary wetland sediments.