Impact of HONO sources on the performance of mesoscale air quality models

Abstract

a b s t r a c tNitrous acid (HONO) photolysis constitutes a primary source of OH in the early morning, which leads to changes in model gas-phase and particulate matter concentrations. However, state-of-the-art models of chemical mechanisms share a common representation of gas-phase chemistry leading to HONO that fails in reproducing the observed profiles. Hence, there is a growing interest in improving the definition of additional HONO sources within air quality models, i.e. direct emissions or heterogeneous reactions. In order to test their feasibility under atmospheric conditions, the WRF-ARW/HERMES/CMAQ modeling system is applied with high horizontal resolution (4 Â 4 km 2 ) to Spain for November 24e27, 2008. HONO modeled sources include: (1) direct emissions from on-road transport; NO 2 hydrolysis on aerosol and ground surfaces, the latter with (2) kinetics depending exclusively on available surfaces for reaction and (3) refined kinetics considering also relative humidity dependence; and (4) photoenhanced NO 2 reduction on ground surfaces. The DOMINO measurement campaign performed in El Arenosillo (Southern Spain) provides valuable HONO observations. Modeled HONO results are consistently below observations, even when the most effective scenario is assessed, corresponding to contributions of direct emissions and NO 2 hydrolysis with the simplest kinetics parameterization. With the additional sources of HONO, PM 2.5 predictions can be up to 14% larger in urban areas. Quantified impacts on secondary pollutants have to be taken as a low threshold, due to the proven underestimation of HONO levels. It is fundamental to improve HONO sources definition within air quality models, both for the scientific community and decision makers.

Impacts of Additional HONO Sources on Concentrations and Deposition of NO_y in the Beijing-Tianjin-Hebei Region of China

“…The extended model with the additional HONO sources succeeded to capture the magnitude and the diurnal variations of the observed data (Table S1), e.g., promising improvement in the model performance is found for predictions of O 3 peaks in urban areas (Li et al 2011). Our results agree with other studies (Li et al 2010;Elshorbany et al 2012;Gonçalves et al 2012), showing that at least the Het and the Emis should be included in models, since their impact on second- (2010) and Spataro et al (2013). Case R is a reference case; Case E includes NO 2 * chemistry, the NO 2 heterogeneous reaction on aerosol surfaces and HONO emissions.…”

“…Air quality models usually severely underestimate HONO observations even though some new HONO formation mechanisms have been considered (Li et al 2010;Gonçalves et al 2012). Previously, the NO 2 * chemistry (Li et al 2008), the NO 2 heterogeneous reaction on aerosol surfaces (Het), and HONO emissions (Emis) were implemented in the fully coupled WRF-Chem resulted in a significant improvement of HONO simulations over the BTH (Li et al 2011;2014b).…”

Large conversion rates of NO2 to HNO2 observed in air masses from the South China Sea: Evidence of strong production at sea surface?

“…Current global and regional chemical transport models that consider the heterogeneous production of HONO on the ground surfaces either do not distinguish sea and land [Elshorbany et al, 2012] or do not consider the HONO formation on the sea at all [Goncalves et al, 2012;Sarwar et al, 2008;Zhang et al, 2012]. Our study indicates that HONO may be produced at a faster rate on the sea; if this finding is confirmed and applicable to other regions, current chemical transport models may need to consider HONO formation on the sea and to adopt different parameterizations for reactions on land and sea.…”

Impact of HONO on global atmospheric chemistry calculated with an empirical parameterization in the EMAC model

“…Li et al (2011) and Goncalves et al (2012) showed that modelled HONO was consistently lower than observations, even when the most effective recently suggested formation mechanisms were considered. This underestimation of HONO by models may be expected to impact the simulated HO x and O 3 budgets as well as other secondary products.…”