摇蚊幼虫与霍普水丝蚓扰动对河流沉积物中氮、磷、氧释放的影响

定量研究河床沉积物中的生物扰动对污染物的影响效应,对于维护河流健康具有重要的理论指导作用.基于室内实验模拟摇蚊和霍普水丝蚓对河床沉积物的扰动过程,研究两种生物扰动作用对沉积物中氮、磷释放以及生物扰动对上覆水中溶解氧的影响.在相同的沉积物环境中分别放入单一物种,实验结果显示,相对于空白组,摇蚊幼虫组的上覆水中氨氮、总氮、总磷平均净增量分别为2.32、0.787、0.105 mg · L^-1,霍普水丝蚓组的氨氮、总氮、总磷平均净增量分别为0.72、0.462、0.063 mg · L^-1,表明摇蚊幼虫和霍普水丝蚓的扰动作用均能促进沉积物中氨氮、总氮、总磷向上覆水中的释放,且摇蚊幼虫对污染物释放的作用效果比水丝蚓更明显;当摇蚊幼虫和水丝蚓混合放入后,摇蚊幼虫对沉积物中氨氮、总氮、总磷释放起主要促进作用;在混合实验组(摇蚊23条,霍普水丝蚓47条)中,氨氮、总氮、总磷的平均净增量均低于单一物种的摇蚊组和水丝蚓组,表明在该组中,摇蚊幼虫和霍普水丝蚓在沉积物中共同扰动作用对氮、磷释放的促进效果减弱;对上覆水中溶解氧浓度而言,摇蚊所占比例越高,溶解氧浓度就越低,且上覆水中的溶解氧浓度变化,会影响生物扰动对沉积物氮、磷释放的效果.

Effect of bioturbation of Chironomid larvae and Limnodrilus hoffmeiteri on the release of nitrogen, oxygen and phosphate in the sediments from a river

Quantitative study the impact of bioturbation on the pollutant in the sediments is of great importance in maintaining the heath of a river ecosystem. The bioturbation processes of invertebrate including Chironomid larvae and Limnodrilus hoffmeiteri, have been investigated in laboratory experiments to explore their impacts on the release of nitrogen and phosphate from sediments and the dissolved oxygen in overlying water. The results demonstrate that in a single species experiment for Chironomid larvae, the average net increasing amount of the ammonia, total nitrogen and total phosphate are 2.32 mg · L^-1, 0.787 mg · L^-1 and 0.105 mg · L^-1, respectively. In the other set of experiment for Limnodrilus hoffmeiteri, the net increase of NH₃, TN and TP are 0.72 mg · L^-1, 0.462 mg · L^-1 and 0.063 mg · L^-1, respectively. The results indicate that the activities of both Chironomid larvae and Limnodrilus hoffmeiteri enhanced the release of nutrient pollutant from sediments to overlying water, and releasing rate of the Chironomid larvae is relatively higher than that of Limnodrilus hoffmeiteri. When mixed with Chironomid larvae and Limnodrilus hoffmeiteri, by different proportions, Chironomid larvae played leading role in release process of total phosphate, total nitrogen and ammonia. In an experiment mixing 23 Chironomid larvae and 47 Limnodrilus hoffmeiteri, the average net increase of total phosphate, total nitrogen and ammonia was lower than single species experiment, indicating the mixing interactions between Chironomid larvae and Limnodrilus hoffmeiteri would lead to the attenuation of bioturbations, and the decrease of the release from sediments into the overlying water. Dissolved oxygen concentration in overlying water had a negative relationship to the proportion of Chironomid larvae. Moreover, the release of total nitrogen and ammonia can be varied with the variation of dissolved oxygen concentration.