DDT污染沉积对氨氧化过程以及相关氨氧化微生物的影响

DDT作为持续性有机污染物（POPs）的一种，所形成的沉积至今仍对土壤造成污染，但是对土壤氨氧化过程的影响机制尚无报道。氨氧化过程是全球氮循环的中心环节，是土壤硝化作用的第一个步骤，也是限速步骤。因此，负责完成这一功能的氨氧化细菌（AOB）/古菌（AOA）在土壤中的相对贡献，也成为焦点。实验发现，在DDT污染土壤中NH4+-N浓度明显升高，推测是由于氨氧化被抑制。本项目将首次研究DDT污染对土壤氨氧化过程及相关的AOA和AOB的影响机制。项目将利用amoA和特异性16S rDNA片段，对实验室和野外的DDT污染土壤监测，分析AOA和AOB丰度、功能和群落结构的变化；利用稳定同位素技术，检测“有活力”的AOA与AOB丰度，确定他们对氨氧化的相对贡献及功能和群落结构。本项目将为DDT污染土壤的评价、治理以及污染土壤氨氧化过程研究提供理论基础和数据参考。

Dichlorodiphenyltrichloroethane (DDT)，as one of Persistent Organic Pollutants (POPs) and sediments，is a long-period contaminant in soil until now. It seems to be one of nitrification inhibitors due to its chemical structure, but little reports have been published on that. Ammonia oxidation, as the first step in the nitrification process（NH4+-N→NO2--N→NO3--N）, plays a central role in the global nitrogen cycling. The differential contributions of Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) have been the controversial focus due to their responsibility for ammonia oxidation. Then we found that the NH4+-N concentration increased obviously in DDT-contaminated soils compared to the uncontaminated samples, indicating ammonia oxidation may be inhibited. In this program, we try to study the effect mechanism of DDT contamination on the ammonia oxidation as well as AOA and AOB in soils. The abundance, function and community structures of AOA and AOB will be analyzed by quantitative real-time PCR and pyrosequencing of their specific genes amoA and 16S rDNA in indoor and outdoor DDT-contaminated soils; with 13C stable isotope labeled, the active AOA and AOB abundance will be also quantified in order to confirm their relative contributions in ammonia oxidation during DDT contamination, and meanwhile their function and community structures may be investigated by quantitative real-time PCR and pyrosequencing, too. In a word, this program will systematically demonstrate the mechanism of ammonia oxidation in DDT-contaminated soils and provide a theory and data basement for the control of DDT-contaminated soils and ammonia oxidation behavior in contaminated environment.