Implementation of an updated chlorine chemistry for the Community Multiscale Air Quality (CMAQ) modeling system using Korean Flexible Chemistry (KFC) editor

Abstract

The heterogeneous reaction of dinitrogen pentoxide (N2O5) and nitryl chloride (ClNO2) is a representative reaction that contributes to the activation of particles containing chlorine in the atmosphere. Chlorine from various sources such as biomass burning and sea salt is reacted with N2O5 to produce ClNO2. ClNO2 is photolyzed to produce chlorine radical. Although reactions of chlorine is diverse, yet there are some that are not reflected among reactions. Additional chlorine reactions were considered in this study because it aims to simulate the actual atmospheric chemistry. Studies of chlorine chemistry have been conducted through the chemical transport model (CTM) involving Community Multiscale Air Quality (CMAQ). However, there are omitted several factors that can alter contributions of chlorine containing particles. CMAQ modeling was conducted improved chlorine chemistry mechanism during the Korea United States Air Quality (KORUS-AQ) campaign. Meanwhile, Korean Flexible Chemistry (KFC) editor to modify chemical mechanism of CMAQ with ease have been developed. In this study, gas-phase chemistry was updated using the KFC editor to combine three homogeneous reactions of formyl chloride (ClCHO) which are considered in CB05tucl mechanism but not in SAPRC07tc. In addition, the update of heterogeneous reactions of hydrochloric acid (HCl), hypochlorous acid (HOCl), and chlorine nitrate (ClONO2) was taken into account in CMAQ. To evaluate the effect of uptake coefficient of N2O5 on the formation of ClNO2, ozone (O3), and nitrate (NO3-), sensitivity analyses of the uptake coefficient ranging from 0.0001 to 0.086 was imposed in CMAQ to show. The results of this study show how chlorine containing substances affect Cl2, ClNO2, O3, and NO3-. In addition, CMAQ-simulated results suggest which uptake coefficient is appropriate for different regions.