太湖地区蟹塘养殖湿地脱氮量及机制研究

Denitrification and anaerobic ammonium oxidation (anammox) are primary processes that regulate the removal of bioavailable nitrogen from aquatic ecosystems. Current shift from rice paddy to crab farming wetland have a considerable impact on nitrogen removing processes. Large nitrogen input and low nitrogen use efficiency in crab farming wetlands, the surplus portion of nitrogen has removed back into the atmosphere through denitrification process. How to quantitative the process of denitrification is important for assessment of the environmental impact on the water body. This study will be carried out in typical crab farming wetlands, which were converted from conventional paddy fields with the conventional paddy fields as control. Based on inteact soil core technique, by using membrane inlet mass spectrometry (MIMS) we measure the nitrogen removing rate from the carb farming wetlands, and combining the 15N isotope pairing technique (15N IPT) we measure the denitrificate rate and anammox rate. The activity and abundance and diversity of denitrifying bacteria and anammox bacteria were detected with real time PCR (qPCR), T-RFLP and high-throughputpyro sequencing produre. The results of this study would be conducive the denitrificate rates, key factors and mechanisms. We can evaluate the effects of N pollution of surface water and provide a scientific basis for recommending reduce N pollution for environment and climate.

反硝化和厌氧氨氧化作用是活性氮以惰性氮形式离开土壤、水体而回到大气的主要自然途径。由稻田转变成的蟹塘氮素投入量大，利用率低，准确定量蟹塘自然脱氮量是正确评估该系统对水体环境影响的前提。本项目以太湖河网地区蟹塘养殖湿地为研究对象，采用膜进样质谱法（MIMS）直接测定蟹塘的脱氮速率，结合15N同位素配对技术（15N IPT）研究反硝化和厌氧氨氧化的脱氮贡献率；同时应用微生物分子生物学技术分析反硝化细菌和厌氧氨氧化细菌的基因丰度、群落组成和结构。该研究将揭示蟹塘养殖湿地周年脱氮总量、脱氮速率的季节动态变化规律及其关键影响因素，明确反硝化、厌氧氨氧化的脱氮贡献率，并阐明其微生物学机制。研究结果将为评估蟹塘活性氮对河网地区水环境的影响以及准确估算蟹塘氮收支提供科学依据。

反硝化和厌氧氨氧化作用是活性氮以惰性氮形式离开土壤、水体而回到大气的主要自然途径。由稻田转变成的蟹塘氮素投入量大、利用率低，富余的部分活性氮通过脱氮过程回到大气，准确定量其自然脱氮过程直接影响到关于活性氮对水体环境影响的准确评估。本项目以太湖河网地区由稻田转变来的蟹塘养殖湿地为研究对象（转变期为5年），采用膜进样质谱法（MIMS）直接测定了蟹塘的周年脱氮速率，结果显示由稻田转变来的蟹塘养殖湿地周年脱氮总量为54 kg N ha-1 yr-1，同时结合15N同位素配对技术（15N IPT）测定了反硝化和厌氧氨氧化的脱氮贡献率，结果表明反硝化的贡献率为64.5%，厌氧氨氧化的贡献率为35.5%；本研究应用16S rRNA基因分析发现Proteobacteria是厌氧氨氧化细菌群落的优势种。研究结果为评估土地利用方式转变条件下农田水体活性氮对河网地区水环境的影响提供科学依据。