Global and regional patterns of soil nitrous acid emissions and their
acceleration of rural photochemical reactions
Abstract
Abiotic and biotic releases of nitrous acid (HONO) from soils contribute
substantially to the missing source of tropospheric HONO and hydroxyl
radicals (OH). However, global and regional patterns of soil HONO
emissions are rarely quantified, and the contributions of such emissions
to atmospheric oxidization capacity are unclear. Here, we present that
the best estimate of global soil HONO emissions in 2017 is 9.67 with a
range of 7.36-11.99 Tg N yr⁻1, where cropland soils
accounted for ~ 79%. The analyses also indicate that
regional soil HONO emissions enhanced ground OH concentrations by
10-60% and ozone concentrations by 0.5-1.5 ppb at daytime in the
ambient area of Shanghai, China. The impact of soil HONO emissions on OH
budgets were more important in rural than urban areas. These findings
suggest that the global soil HONO emissions, especially from cropland,
could quicken photochemical reactions and aggravate air pollution in
rural areas.