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RESEARCH PRODUCT

Global impact of monocyclic aromatics on tropospheric composition

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Abstract. Aromatic compounds are reactive species influencing ozone formation, OH concentrations and organic aerosol formation. An assessment of their impacts on the gas-phase composition at a global scale has been performed using a general circulation atmospheric-chemistry model. Globally, we found a small annual average net decrease (less than 3 %) in global OH, ozone, and NOx mixing ratios when aromatic compounds are included in the chemical mechanism. This inclusion of aromatics also results in CO mixing ratio increases, which cause a general decrease in OH concentrations. The largest changes are found in glyoxal and NO3, with increases in the atmospheric burden of 10 % and 6 %, respectively. Regionally, significant differences were found particularly in high NOx regime areas, with an increase of up to 4 % in O3 mixing ratios and 8 % in OH concentrations. NO3 increased by more than 30 % in several regions of the northern hemisphere, and glyoxal increased up to 40 % in Europe and Asia. Large increases in formaldehyde were found in urban areas. Although the relative impact of aromatics at the global scale is limited, at a regional level they are important in atmospheric chemistry.