洗脱对上覆水环境及底泥氮磷迁移转化的影响

Effect of the elution on upper water environment and nitrogen and phosphorus migration and transformation in the sediment

基于黑臭水塘底泥和水构建模拟体系,进行扰动前洗腹处理,探测洗脱转移底泥中底泥存量、容重及细颗粒占比的变化,检测扰动或洗脱前后静置状态下系统中上覆水浊度、溶解氧(dissolved oxygen,DO)及上覆水和底泥间隙水中氮磷质量浓度变化。结果表明:洗脱可有效削减底泥中细颗粒物,削减底泥存量,增加底泥容重,提升上覆水透明度。扰动或洗脱前,上覆水DO低、总氮(total nitrogen,TN)和氨氮高、总磷(total phosphorus,TP)平稳、溶解性总磷(dissolved total phosphorus,DTP)波动上升,底泥间隙水氨氮质量浓度是上覆水中的2倍。扰动处理后水中DO不增反降,但洗脱组水中的DO大幅升高。扰动和洗脱后上覆水DTP质量浓度下降约80%,其他形态氮磷质量浓度在洗脱组的升高幅度显著低于扰动处理,此后63 d洗脱组氮磷质量浓度以更快速度、更大幅度下降,最终各处理中NO_(3)-N为氮的主要形态。与此同时,扰动后底泥间隙水氮、TP、DTP质量浓度分别降低50%、77%、40%,洗脱后则分别降至10%以下、14%、38%,氨氮仍是间隙水氮的主要形态,但洗脱组氨氮占TN比例低于扰动组。仅扰动处理底泥氨氮、DTP以向上覆水释放为主,而洗脱后则以吸收为主。

A simulation system was constructed using sediment and water from a black and odorous pond.Disturbance or elution(disturb-and-transfer)was applied on the system.Changes of sediment amount,bulk density,and proportion of fine particles were examined after the treatments.Turbidity and dissolved oxygen(DO)in upper water,as well as nitrogen and phosphorus mass concentrations in both upper water and sediment interstitial water of the system,under static state,were examined before and after the disturbance or elution.The results show that elution can effectively remove fine particles from sediment,reduce sediment amount,increase sediment bulk density,and significantly improve the transparency of upper water.Before disturbance or elution,the upper water had low DO,high total nitrogen(TN)and ammonia nitrogen,stable total phosphorus(TP),and fluctuating dissolved total phosphorus(DTP).The concentration of ammonia nitrogen in the sediment interstitial water was twice that in upper water.After the disturbance treatment,DO in the water did not increase but decreased,but DO in the elution group increased significantly.After disturbance and elution,the concentration of DTP in upper water decreased by about 80%,and the increase of the concentrations of other forms of nitrogen and phosphorus in elution group was significantly lower than that in disturbance group.During the following 63-day period,concentrations of nitrogen and phosphorus in upper water of the elution group decreased more rapidly and significantly,and eventually NO_(3)-N became the main form of nitrogen in each treatment.In the meantime,concentrations of nitrogen,TP and DTP in sediment interstitial water decreased by 50%,77% and 40% in disturbance group,but decreased to less than 10%,14% and 38%,respectively,in elution group.Ammonia nitrogen was still the main form of nitrogen in interstitial water,but its proportion in TN in elution group was lower than that in disturbance group.The ammonia nitrogen and DTP in the disturbance treatment were mainly released from sediment into upper water,while they were mainly absorbed into sediment after elution.