近日，美国加州大学 Alexander H. Krichels 的课题组成员取得一项新突破。他们提出在南加州干旱地区，细菌反硝化作用导致了 N₂O 排放量的增加这一新观点。2023年12月8日，国际知名学术期刊《科学进展》发表了这一成果。

课题组人员在加州沙漠中使用同位素和分子方法，发现反硝化菌在干燥土壤湿润后的 15 分钟内产生 N₂O(位置偏好= 12.8±3.92 per mil， δ ¹⁵N^bulk = 18.6±11.1 per mil)。与这一发现一致，课题组人员在干燥土壤中检测到了硝酸盐还原转录物，发现抑制微生物活性可减少 59 %的 N₂O 排放量。研究结果强调，尽管存在极端的环境条件（没有降水的月份，土壤温度≥ 40°C，土壤重量含水量为 1 %），细菌反硝化菌也可以解释干燥土壤湿润时排放的大部分 N₂O。

据课题组人员介绍，土壤是大气中一氧化二氮(N₂O)的最大来源，N₂O 是一种强大的温室气体。干燥的土壤很少存在有利于反硝化的缺氧条件，而反硝化是主要的 N₂O 产生过程，然而，研究人员在湿润的夏季—干燥的沙漠土壤中测量了最大的 N₂O 排放量并提出了一个科学问题，即反硝化细菌能忍受极端干旱并在降雨后立即产生 N₂O 吗？

附：英文原文

Title: Bacterial denitrification drives elevated N₂O emissions in arid southern California drylands

Author: Alexander H. Krichels, G. Darrel Jenerette, Hannah Shulman, Stephanie Piper, Aral C. Greene, Holly M. Andrews, Jon Botthoff, James O. Sickman, Emma L. Aronson, Peter M. Homyak

Issue&Volume: 2023-12-08

Abstract: Soils are the largest source of atmospheric nitrous oxide (N₂O), a powerful greenhouse gas. Dry soils rarely harbor anoxic conditions to favor denitrification, the predominant N₂O-producing process, yet, among the largest N₂O emissions have been measured after wetting summer-dry desert soils, raising the question: Can denitrifiers endure extreme drought and produce N₂O immediately after rainfall Using isotopic and molecular approaches in a California desert, we found that denitrifiers produced N₂O within 15 minutes of wetting dry soils (site preference = 12.8 ± 3.92 per mil, δ¹⁵N^bulk = 18.6 ± 11.1 per mil). Consistent with this finding, we detected nitrate-reducing transcripts in dry soils and found that inhibiting microbial activity decreased N₂O emissions by 59%. Our results suggest that despite extreme environmental conditions—months without precipitation, soil temperatures of ≥40°C, and gravimetric soil water content of <1%—bacterial denitrifiers can account for most of the N₂O emitted when dry soils are wetted.

DOI: adj1989

Source: https://www.science.org/doi/10.1126/sciadv.adj1989