基于硝化速率法的重金属元素Pb、Cu生物毒性研究

文章采用硝化速率法研究了重金属元素 Pb、Cu的毒性，分析了重金属 Pb、Cu对污泥胞外聚合物（EPS）的影响，初步探讨了重金属毒性机理。研究结果表明：Cu和Pb均是氨氧化细菌的高毒物质，其半最大效应浓度EC50分别是63.60、77.40 mg/L ；Cu/Pb的联合作用方式为协同效应；对细胞活性产生促进、抑制的ρ（Cu）范围分别是0.01～1 mg/L和1～50 mg/L ，ρ（Cu）＝100 mg/L是细胞死亡、结构破坏的临界点；ρ（Pb）＜1 mg/L可以促进细胞活性，而ρ（Pb）＞1 mg/L后，细胞活性降低，且随着ρ（Pb）增加细胞结构破损加剧。

胞外聚合物对生物脱氮效果的影响研究

考察了PAC-MF系统启动阶段在不同水力停留时间(HRT)下的生物除氮的效果;同时,以硝化速率法表征硝化活性,研究了胞外聚合物(EPS)对硝化菌活性的影响.结果表明,HRT较短的1#系统启动完成所需的时间、NO2-—N积累持续的时间均大于2#系统,NH4+—N的去除效果远远差于2#系统;EPS对硝化活性的抑制作用存在一个临界质量浓度,由硝化速率法得到的临界质量浓度为10 mg/L.

Comparison of Gross N Transformation Rates in Two Paddy Soils Under Aerobic Condition

Although to date individual gross N transformations could be quantified by 15N tracing method and models, studies are still limited in paddy soil. An incubation experiment was conducted using topsoil （0-20 cm） and subsoil （20-60 cm） of two paddy soils, alkaline and clay （AC） soil and neutral and silt loam （NSL） soil, to investigate gross N transformation rates. Soil samples were labeled with either 15NHaNO3 or NH4SN03, and then incubated at 25 ℃for 168 h at 60% water-holding capacity. The gross N mineralization （recalcitrant and labile organic N mineralization） rates in AC soil were 1.6 to 3.3 times higher than that in NSL soil, and the gross N nitrification （autotrophic and heterotrophic nitrification） rates in AC soil were 2.4 to 4.4 times higher than those in NSL soil. Although gross NO3 consumption （i.e., NO3 immobilization and dissimilatory NO3 reduction to NH＋） rates increased with increasing gross nitrification rates, the measured net nitrification rate in AC soil was approximately 2.0 to 5.1 times higher than that in NSL soil. These showed that high NO3 production capacity of alkaline paddy soil should be a cause for concern because an accumulation of NO3 can increase the risk of NO3 loss through leaching and denitrification.