| Description |
The composition of the Earth's atmosphere is strongly affected by the biogeochemical cycling of reactive nitrogen species. Nitrous acid, HONO, is a key species due to its effect on free radical formation and recycling. At low soil water content, HONO is released by aerobic ammonia-oxidizing bacteria, but little is known about HONO release in water-saturated and oxygen-limited soils. We find large HONO emissions from soils at high water content (80 - 140% of water holding capacity) and from pure cultures of nitrate reducing bacteria incubated with nitrate or nitrite. Gene expression analyses show a correlation of HONO emissions with imbalances in nitrite production and consumption that may result in nitrite accumulation at the cell surface. High throughput Illumina sequencing of 16S rRNA as well as nitrate and nitrite reduction associated functional gene transcripts indicate that HONO emissions from an agricultural soil sample are associated with the activity of diverse Proteobacteria. This biological process is an additional source of atmospheric HONO that should be considered in biogeochemical nitrogen cycling, global models of soil reactive nitrogen emissions, and air chemistry. |
