Impact of sub-grid particle formation in sulfur-rich plumes on particle mass and number concentrations over China

Abstract

Particle formation in point source plumes is a typical sub-grid process not explicitly resolved in chemical transport models, and is an important contributor to atmospheric aerosols. The sub-grid particle formation (SGPF) is closely associated with the concentration of hydroxyl radical and condensation sinks in the plume, thus it has diurnal, seasonal and spatial variations. The impacts of SGPF in point source plumes on both aerosol mass and number concentrations were first investigated in China by a newly developed global nested chemical transport model with a SGPF parameterization scheme. Although a mean oxidation fraction of 2.5% sulfur dioxide for parameterizing the SGPF is suggested, the oxidation fraction and the particles formed in point source plumes have clear spatiotemporal variations based on the results of the SGPF scheme. The SGPF can enhance the annual mean concentration of sulfate by more than 1 μg m−3 (10–25%) over high emission areas (HEAs) in central-eastern China (CEC). In terms of particle number concentration, the SGPF contributes much more to nucleation mode particles with increasing number concentration, by 25–50% in HEAs, 10–25% in CEC, and 1–5% in northwestern China (NWC) compared with lower values (within ±5%) for the accumulation mode. This study reveals the significant impacts of SGPF over China and its strong dependence on meteorological and environmental factors. Physically-based SGPF scheme should be incorporated when studying the regional effects of point source plumes on air quality and climate.