Pollution levels, characteristics, and sources of polycyclic aromatic hydrocarbons in atmospheric particulate matter across the Hu line in China. A review

There is few knowledge on the influence of geography, climate and socio-economy on pollutant levels. Therefore, here we studied atmospheric pollutants from both sides of the Hu line in China. The Hu line is a geographical line stretching from Heihe in the Northeast to Tengchong in the Southwest, and divides China into two approximately equal parts with a semi-arid region to the west and a semi-humid region in the east. This study investigated the correlation between pollution levels, characteristics, and sources of polycyclic aromatic hydrocarbons (PAHs) and the population and gross domestic product (GDP) on each side of the Hu line. We analyzed the data for PAHs in atmospheric particulate matter (PM), GDP and population from 93 above-prefecture level cities in China in 2000–2019. The concentration of PAHs in PM varied across seven regions of China: Northeast > North China > Northwest > South China > Southwest > Central China > South China Sea. The mean abundance of carcinogenic PAHs, non-carcinogenic PAHs, PAHs derived from burning organic matter, and low, medium, and high molecular weight PAHs amongst 16 priority PAHs were 53.5%, 46.5%, 80.0%, 16.9%, 45.2%, and 37.9%, respectively. From Central China to Southwest and North China, the content and pollution of PAHs increased with increasing population and decreasing GDP. From southwest to northwest and central China to South China, the PAHs content and pollution increased with decreasing population and GDP. In assessing the impact of the Hu line on pollution in Chinese cities, it is clear that objective conditions such as geography, climate, city ecology, and industrial type are closely related to PAHs pollution, while population and GDP are only weakly correlated with such pollution. Comprehensive measures must be implemented to reduce pollution and sources of PAHs in heavily polluted areas.