摘要:气态亚硝酸（HONO）是大气中氢氧自由基（OH·）的重要来源，直接影响到大气氧化能力和空气质量。通过比较外场测定和模型计算的HONO浓度，发现白天时存在未知的大气HONO来源。研究表明，土壤可以向大气中排放HONO。其机理可能是土壤亚硝态氮和氢离子的化学平衡作用；或土壤夜间吸附和白天解吸附的动态物理化学过程；或氨氧化细菌等微生物的直接排放；也可能是硝化过程中产生的羟胺，在土壤颗粒物等表面的化学反应。因此，土壤HONO排放通量与土壤亚硝态氮浓度、pH、氨氧化细菌丰度、土壤矿物、土壤湿度及C/N值等相关。目前对于土壤HONO排放的研究尚在起步阶段，国内亦少见相关成果报道。本文综述了土壤HONO排放的研究背景、探讨了土壤HONO排放的机理及影响因素，以期为减少氮素损失、提高氮肥利用率、评估氮肥的环境效应及城市空气质量等提供理论依据和科学指导。
关键词:氮循环/
气态亚硝酸/
土壤/
pH/
硝化/
氨氧化细菌/
二氧化氮
Abstract:Nitrous acid (HONO) significantly contributes to atmospheric hydroxyl radical (OH·) and also influences atmospheric oxidation capacity and air quality. Comparison of HONO concentrations measured in a field campaign and by modeling showed a large unknown HONO source during daytime. Studies have shown that the unknown HONO source can be attributed to soil emissions, a major source of atmospheric HONO. The mechanisms may be taking the form of chemical equilibrium between soil nitrite and H+, reactive uptake and displacement by soil, emissions by ammonia-oxidizing bacteria (AOB) and other micro-organisms, or surface reaction between hydroxylamine and H2O. Therefore, HONO flux from soils is controlled by soil nitrite concentration, pH, AOB abundance, soil minerals, soil moisture and C/N ratio. The mechanism of HONO emissions from soil has remained a point of hot discussion and few results have been reported from China. Here, we introduced the background of HONO emissions from soil, reviewed studies on the mechanisms of HONO emissions from soil and the related driving factors. This review was a relevant support for research on reducing nitrogen loss, enhancing nitrogen use efficiency, and evaluating the effects of nitrogen fertilization on environmental and urban air quality.
Key words:Nitrogen cycle/
HONO/
Soil/
pH/
Nitrification/
Ammonia-oxidizing bacteria (AOB)/
Nitrogen dioxide
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