CO_2浓度升高对水体硝化、反硝化作用的影响研究进展

大气CO_2浓度升高潜移默化地影响着水体生态系统的碳循环过程.然而,该过程如何影响与其耦合的氮循环过程仍不明确.水体硝化、反硝化过程作为水体氮循环的重要环节,必然会对大气CO_2浓度升高产生一系列的响应.本文总结了国内外关于大气CO_2浓度升高对水体理化性质、硝化作用、反硝化作用及N形态转化影响方面的研究工作,发现大气CO_2浓度升高会降低水体的p H,增加水中CO_2和HCO_3^-含量,但对富营养化与寡营养化水体中硝化、反硝化作用的影响具有明显差异.大气CO_2浓度升高抑制寡营养化水体的硝化作用和反硝化作用,降低N2_O的释放通量,抑制富营养化水体的硝化作用,但当水体pH在7～9时,可能促进反硝化作用,增加N2_O的释放通量,最终可能导致水体中NH_4^+的积累及NO_3^-浓度的降低,影响水体中微生物的多样性.在此基础上提出目前相关研究存在的瓶颈问题及值得深入探讨的科学问题,为进一步深入理解温室效应背景下全球CO_2浓度升高对水体生态系统N循环的影响提供参考.

Influence of elevated CO2 on nitrification and denitrification in water bodies: A review

Elevated atmospheric CO₂ has imperceptible impacts on carbon cycle in aquatic ecosystems. However, it remains a question how this process will impact nitrogen cycle that is naturally coupled with carbon cycle. The nitrification and denitrification are two critical processes in the nitrogen cycle. It is reasonable to expect that elevated atmospheric CO₂ will influence both processes. We reviewed the previous literatures concerning the effects of elevated atmospheric CO₂ on the physico-chemical properties, nitrification, denitrification and nitrogen transformation in water bodies. The published results revealed that the elevated CO₂ would reduce the water pH, increase CO₂ and HCO₃^- concentrations, but with different effects on the nitrification and denitrification between eutrophic and oligotrophic water. Elevated atmospheric CO₂ could inhibit nitrification and denitrification in oligotrophic water, thereby reduce N₂O flux from water. The nitrification process in the eutrophic water bodies was also inhibited, but its denitrification might be promoted by the elevated CO₂. In the eutrophic water bodies, there could be an increase of N₂O flux when pH was maintained in the range of 7-9. These might eventually result in the accumulation of NH₄⁺ and reduction of NO₃^- in water, producing an impact on the microbial diversity. Based on these reviews, we proposed some research gaps related to the relevant research fields as well as some scientific questions that is worth to be further explored. This review would be helpful to better understanding on how the greenhouse effect caused by the elevated atmospheric CO₂ would affect nitrogen cycle in aquatic ecosystem.