Development and evaluation of the chemical Mechanism for Air pollution compleX version 1.0 (MAX1)

The Mechanism for Air pollution compleX version 1.0 (MAX1) describing detailed tropospheric chemical processes has been developed based on the up-to-date understandings. MAX1 contains 940 reactions including photolysis, gaseous reactions and heterogeneous reactions of 300 species, which is adequate for both box model and climate transport model (CTM) applications. Detailed chemical processes of chlorine chemistry, chemistry of Criegee radicals and heterogeneous uptake of HO2 and N2O5 have been implemented and updated. With this level of explicitness, MAX1 can support investigations on the quantification of secondary pollutant productions and the chemical behavior of the crucial intermedia such as organic peroxy radicals. Box model and CTM tests were conducted to evaluate the performance of MAX1 from different perspectives. Simulations of MAX1 well captured the variation of ozone in all cases tested. Meanwhile, significant improvement was made on predictions of radicals compared to other mechanisms, especially under the low NOx environment, with good similarity to simulations of a nearly explicit chemical mechanism (i.e. Master Chemical Mechanism, MCM) that contains over 17000 reactions. MAX1 introduces new dimensions in atmospheric chemistry modeling, its potential application in policy-making is a promising yet exploratory step. It offers improved insights into air quality dynamics, which could assist policymakers in making more informed decisions. However, the translation of its detailed chemical understanding into practical strategies remains an area for further investigation. This model suggests a path towards more nuanced air pollution control methods, contributing to ongoing efforts in environmental management.