硫酸盐对养殖池塘沉积物中氨氮的影响研究

Pollution by ammonia nitrogen has been a serious problem in high-density aquaculture, and its transformation in aquaculture pond sediment has been hampered by limited electric acceptors. Sulfur constitutes another important pollutant in aquaculture pond. Recent studies indicate that under anoxic conditions, products from redox reactions of sulfur species act as important electron shuttles in a series of biochemical processes including nitrification, and may server as electric acceptors for ammonia oxidization. However, little attention has been paid on the effect of sulfate on ammonia transformation in aquaculture pond. This proposed project made a hypothesis that addition of sulfate may cause effects on ammonia transformation in aquaculture pond sediment. In view of this, meso-/microcosms will be designed to study the influence law as well as the pathways. The main research contents will include: 1) effects of sulfate addition on ammonia transformation in aquaculture pond sediments; 2) variations of ammonia-oxidizing microorganisms in aquaculture pond sediments after sulfate addition; and 3) pathways of effects of sulfate on ammonia transformation in aquaculture pond sediments under anoxic conditions, with the purpose to study the possible mechanisms of effects of sulfate on ammonia transformation in aquaculture pond sediment. Results from this proposed project will help to further understand the interactions between nitrogen and sulfur cycles, and may also provide theoretic basis for removal of nitrogen and sulfur pollutants in sediment of aquaculture ponds.

氨氮污染是高密度池塘养殖迫切需要解决的问题，但养殖池塘沉积物中氨氮的转化受到电子受体缺乏的限制。硫是养殖池塘中的另一类重要的污染物，最近的研究表明厌氧条件下硫的还原氧化产物在包括硝化作用在内的一系列生化过程中具有重要的电子穿梭功能，并可能用作氨氧化反应的电子受体。但目前还很少有研究关注养殖池塘中硫酸盐对氨氮的影响。本课题假设硫酸盐的加入会对养殖池塘沉积物中氨氮的转化造成影响，并基于此设计中/微宇宙系统来研究其影响规律和机制。本项目的主要研究内容包括：①不同浓度硫酸盐加入对养殖池塘沉积物中氨氮的影响；②不同浓度硫酸盐加入后养殖池塘沉积物中氨氧化微生物群落的改变；③厌氧条件下硫酸盐影响养殖池塘沉积物中氨氮的途径，以分析硫酸盐影响养殖池塘沉积物中氨氮的可能机制。本研究结果有助于进一步揭示氮、硫等物质循环间的交互规律，还能为养殖池塘沉积物中氮、硫污染物的修复提供基础依据，具有重要的理论和应用价值。

氮素和硫素是养殖池塘中的大量元素，其物质平衡对于池塘水体稳定和养殖动物健康具有重要意义。越来越多的证据表明，氮、硫等元素间存在密切的相互关系。为了更全面的了解养殖池塘水体氮、硫等元素间的相互作用，本项目研究了加入不同浓度硫酸盐后池塘沉积物碳、氮、硫等物质及微生物的变化规律。结果表明：（1）高浓度SO42-能够引起养殖池塘水体pH和盐度的显著改变，并可引起沉积物有机质分解和氮循环过程的明显改变。SO42-可能对沉积物-水柱界面NO3-、NO2-和NH4+扩散通量造成影响。同时，SO42-浓度的增加会抑制池塘表层沉积物的氨氧化速率，影响池塘沉积物氨氮的转化。（2）较长时间的高浓度SO42-会对池塘沉积物微生物群落造成重要影响，微生物群落自身的转变和硫酸盐引起的有机质分解改变可能是造成微生物群落变化的关键因素。（3）养殖池塘表层沉积物氨氧化微生物类群较稳定，能够耐受一定程度的SO42-浓度升高引起的环境改变，其群落的变化主要是由于SO42-引起的有机质分解改变。（4）在缺氧条件下，池塘沉积物SO42-很容易被还原为S2-，并可能通过促进反硝化作用来促进氮的移除，但高浓度SO42-可能抑制有机质分解和氮素转化。同时，池塘沉积物Fe2+和Mn2+在固定还原性硫并减少其不利影响中发挥重要作用。总之，SO42-的还原氧化反应可能通过介导有机质的分解转化来影响池塘底泥氨氮的转化。提高底泥有机质的分解转化，对于减少养殖池塘硫和氮素的污染可能都有重要的意义。