Variations in soil HONO emissions under greenhouse field conditions and their driving mechanisms

Atmospheric nitrous acid (HONO), a precursor of hydroxyl radicals, is a key species influencing atmospheric chemistry and air quality. Soils have been identified as important sources of HONO emissions; however, greenhouse soils have so far remained unexplored.

Filed observation of soil HONO emissions was conducted along with metatranscriptomic analyses across different phases of vegetable cultivation in a greenhouse in this study to investigate the variations in soil HONO emissions and explore their driving mechanisms.

The results show that HONO fluxes from greenhouse soils reached 18.89 ng N m^-2 s^-1 following fertilization. The findings demonstrated that greenhouse soils were important source of HONO emissions that may need to be considered in global atmospheric budgets. Moreover, variations in HONO emissions in the greenhouse field were primarily affected by soil electrical conductivity. Metatranscriptomic analyses revealed that the transcription of narH and nasA in Bacillariophyta and nmo in Actinomycetota might contribute to elevated HONO emissions. In addition, microbial nitroalkane oxidation was identified as a potential mechanism of soil HONO production, operating alongside nitrate reduction. Therefore, future studies should more comprehensively address the mechanistic and budgetary implications of soil HONO emissions.