Source contributions to poor atmospheric visibility in China

Abstract China suffers from serious haze pollution characterized by extremely low visibility due to intensive air pollutant emissions. Designing effective visibility impairment control strategies requires quantitative measures of the contributions of different sources. In this study, a source-oriented Community Multiscale Air Quality model was applied to quantitatively determine the source contributions to visibility impairment in China in 2013. Emissions of air pollutants from seven source categories (power plants, residential sources, industries, transportation, open burning, dust, and agriculture) were separately tracked. The industrial sector dominates the visibility impairment in Beijing, Chongqing, Guangzhou, and Shanghai, contributing to 32.6–40.7% of the overall light extinction coefficient (b ext ). Agriculture and power sources contribute 13.0–16.7% and 12.6–14.9% to b ext , respectively. The residential sector is the largest source of visibility impairment in Xi’an (39.5%). It also contributes 12.3–25.2% in Beijing, Chongqing, Guangzhou, and Shanghai. Transportation (6.3–10.2%), open burning (1.7–8.8%), and dust emission (1.0–3.6%) have relatively smaller contributions to b ext in these cities. The source contributions to b ext exhibit strong spatial and seasonal variations. Contributions from industrial, power, and residential sectors are higher in the North China Plain, Northeast China, and Sichuan Basin than in other regions of China. Industrial and residential emissions become the most important sources of visibility impairment in winter. In other seasons, industrial, power, and agriculture sources are important. The large spatial and seasonal variations in the sources of b ext suggest that different pollutants mitigation programs should be designed for different regions and times of the year.