Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Environ Sci Technol. 2023 Feb 21;57(7):2970-2980. doi: 10.1021/acs.est.2c06124. Epub 2023 Jan 31.
Paddy fields are one of the most important sources of nitrous oxide (NO), but biogeochemical NO production mechanisms in the soil profile remain unclear. Our study used incubation, dual-isotope (N-O) labeling methods, and molecular techniques to elucidate NO production characteristics and mechanisms in the soil profile (0-60 cm) during summer fallow, rice cropping, and winter fallow periods. The results pointed out that biotic processes dominated NO production (72.2-100%) and NO from the tillage layer accounted for 91.0-98.5% of total NO in the soil profile. Heterotrophic denitrification (HD) was the main process generating NO, contributing between 53.4 and 96.6%, the remainder being due to ammonia oxidation pathways, which was further confirmed by metagenomics and quantitative polymerase chain reaction (qPCR) assays. Nitrifier denitrification (ND) was an important NO production source, contributing 0-46.6% of total NO production, which showed similar trends with NO emissions. Among physicochemical and biological factors, ammonium content and the ratio of total organic matter to nitrate were the main driving factors affecting the contribution ratios of the ammonia oxidation pathways and HD pathway, respectively. Moisture content and pH affect -carrying and thus the NO production rate. These findings confirm the importance of ND to NO production and help to elucidate the impact of anthropogenic activities, including tillage, fertilization, and irrigation, on NO production.
稻田是氧化亚氮（NO）的最重要来源之一，但土壤剖面中生物地球化学 NO 产生机制仍不清楚。本研究采用培养、双同位素（N-O）标记方法和分子技术，阐明了夏季休耕、水稻种植和冬季休耕期间土壤剖面（0-60cm）中 NO 的产生特征和机制。结果表明，生物过程主导了 NO 的产生（72.2-100%），且耕作层的 NO 占土壤剖面中总 NO 的 91.0-98.5%。异养反硝化（HD）是产生 NO 的主要过程，贡献了 53.4-96.6%，其余则归因于氨氧化途径，这进一步通过宏基因组学和定量聚合酶链反应（qPCR）试验得到了证实。硝化-反硝化（ND）是重要的 NO 产生源，占总 NO 产生量的 0-46.6%，其与 NO 排放具有相似的趋势。在理化和生物因素中，铵含量和总有机碳与硝酸盐的比值分别是影响氨氧化途径和 HD 途径贡献比例的主要驱动因素。含水量和 pH 值影响着-携带，从而影响 NO 的产生速率。这些发现证实了 ND 对 NO 产生的重要性，并有助于阐明包括耕作、施肥和灌溉在内的人为活动对 NO 产生的影响。
