Sun Shiquan

The Influence of Tubifex Bioturbation on Total Nitrogen Release from Sediment of Dongting Lake

This study investigated the release rule of total nitrogen from sediments by Tubifex tubifex bioturbation indifferent environmental conditions. Tubifex tubifex density¡¢temperature¡¢pH value and dissolved oxygen were selected as influencing factors. The results showed that bioturbation of Tubifex tubifex had a good accelerating effect on total nitrogen release of sediment and the concentration of total nitrogen in overlying water respectively increased to 1.2 fold and 1.3 fold when Tubifex tubifex density was 1ind./cm2 and 2ind./cm2compared to control test. Appropriate increasing of water temperature was helpful to the fast growth of Tubifex tubifex, which caused that total nitrogen in overlying water raised by56 percent when temperature increased from 15¡æ to 25¡æ. Adversity stress on Tubifex tubifex, induced by acidic and alkali environment, enhanced its bioturbation effect and also accelerated the total nitrogen releasing from sediment. Total nitrogen increase amplitude of overlying water in anaerobic was 1.3 fold compared to aerobic environment, which indicated that Tubifex tubifex had good adaptability to anaerobic environment in which bioturbation was more than in aerobic environment.

The influence of Limnodrilus hoffmeisteri bioturbation on nitrogen release from sediments in the East Lake Dongting

The effects of Limnodrilus hoffmeisteri bioturbation on nitrogen releasing from sediments of the East Lake Dongting,with the different densities and environments were studied in this paper.The results showed that bioturbation of L.hoffmeisteri had a good accelerating effect on nitrogen release from sediments,which was caused mainly by ammonium release.When the density of L.hoffmeisteri was at 1 and 2ind./cm2,the concentrations of total nitrogen in overlying water were increased by 15% and 32% respectively comparing to the control test.Appropriate increasing of temperature was helpful for vital movement of L.hoffmeisteri,which caused that total nitrogen release increment were increased by 23% and 69% respectively when temperatures were 15℃ and 25℃ compared to the cotrolling 5℃.Adversity stress on L.hoffmeisteri,induced by acidic and alkali environments,enhanced its bioturbation effect and also accelerated nitrogen releasing.In comparison with a condition of pH 7,total nitrogen release increment were increased by 32% and 41% when pH values were 5 and 9,respectively.Total nitrogen release increment in hypoxia was 1.52 fold compared to the aerobic environment,which indicated that L.hoffmeisteri had good adaptability and survivability to hypoxia environment in which bioturbation was stronger than in aerobic environment.