Distribution and sources of PM2.5-bound free silica in the atmosphere of hyper-arid regions in Hotan, North-West China

The composition of atmospheric fine particulate matter (PM2.5) is complex and exhibits strong regional differences. Free silica (alpha-SiO2) in atmospheric particulate matter is carcinogenic and is an important component of respirable particulate matter in urban areas. Measurements determined that the concentration of silicon dioxide (alpha-SiO2) in PM2.5 in the urban area of I lotan City, China, was 8.02 mu g.m(-3) during the dust period and exceeded 1.77 mu g.m(-3) during the non-dust period. The proportion of a-SiO2 in PM2.5 was 8.07% during the dust period and 2.25% during the non-dust period. Atmospheric visibility during the dust period was mainly influenced by the content of atmospheric floating dust. Analysis of alpha-SiO2 pollution sources during the dust period showed that the air masses containing sand and dust originated from the desert hinterland. Following passage through oasis areas, the air mass was effectively reduced in the concentration of alpha-SiO2 in PM2.5. During the dusty period, alpha-SiO2 and PM2.5 originated from the same source in Hotan City. Moreover, wind speed was the main influencing factor for the alpha-SiO2 concentration. During the non-dust period, alpha-SiO2 and PM2.5 were not from the same source of pollution.

Automated summary

This study found that the concentration of silica dioxide (α-SiO2) in PM2.5 was higher during dust period and lower during non-dust period in urban areas. The atmospheric visibility during dust period was mainly influenced by the content of atmospheric floating dust. Additionally, the sources of α-SiO2 and PM2.5 were different during dust period and non-dust period.