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 (α-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 (α-SiO2) in PM2.5 in the urban area of Hotan City, China, was 8.02 µg·m-3 during the dust period and exceeded 1.77 µg·m-3 during the non-dust period. The proportion of α-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 α-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 α-SiO2 in PM2.5. During the dusty period, α-SiO2 and PM2.5 originated from the same source in Hotan City. Moreover, wind speed was the main influencing factor for the α-SiO2 concentration. During the non-dust period, α-SiO2 and PM2.5 were not from the same source of pollution.

Distribution, sources, risks, and vitro DNA oxidative damage of PM2.5-bound atmospheric polycyclic aromatic hydrocarbons in Urumqi, NW China.

Research has focused on the impacts of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere due to their potential carcinogenicity. In this study, we investigated the seasonal variation, sources, incremental lifetime cancer risks (ILCRS), and vitro DNA oxidative damage of PAHs in Urumqi in NW China. A total of 72 atmospheric samples from Urumqi were collected over a year (September 2017-September 2018) and were analyzed for 16 PAHs that are specifically prioritized by the U.S Environmental Protection Agency (U·S EPA). The highest PAHs concentrations were in winter (1032.66 ng m-3) and lowest in spring (146.00 ng m-3). Middle molecular weight PAHs with four rings were the most abundant species (45.28-61.19% of the total). The results of the diagnostic ratio and positive matrix factorization inferred that the major sources of atmospheric PAHs in Urumqi were biomass burning, coking, and petrogenic sources (52.9%), traffic (30.1%), coal combustion (8.9%), and the plastics recycling industry (8.1%). ILCRS assessment and Monte Carlo simulations suggested that for all age groups PAHs cancer risks were mainly associated with ingestion and dermal contact and inhalation was negligible. The plasmid scission assay results showed a positive dose-response relationship between PAHs concentrations and DNA damage rates, demonstrating that toxic PAHs was the primary cause for PM2.5-induced DNA damage in the air of Urumqi.