Contribution of HONO sources to the NO sub(x)/HO sub(x)/O sub(3) chemistry in the polluted boundary layer

The contribution of HONO photolysis to the primary production of OH radicals and the impact of HONO sources to the O sub(3) and NO sub(x) budgets has been investigated using a two-layer box model. Three sources of HONO were considered: direct emissions, heterogeneous production on the ground surface and heterogeneous production on the aerosol surface. We considered two scenarios representing typical urban and polluted rural area and simulations were conducted for both summer and winter conditions. For summertime conditions, HONO sources were found to have a slight impact on the NO sub(x)/HO sub(x)/O sub(3) concentration profiles, except for conditions favoring the formation of photochemical pollution episodes where it becomes significant. For wintertime conditions, HONO sources were found to be major contributors to the primary OH production, leading to major changes in the HO sub(x) and NO sub(x) budget all day long.