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Atmospheric particulate matter (PM 2.5 and PM 10) samples were collected at urban and suburban sites in Xi'an City from December 2016 to November 2017. Sixteen priority polycyclic aromatic hydrocarbons (PAHs) associated with PM 2.5 and PM 10 were analyzed for their seasonal variations, sources, health risks, and influencing factors. The results showed that the annual average concentrations of PM 2.5 and PM 10 were 111 and 185 μg/m3, respectively, exceeding the National Ambient Air Quality Standard of China (35 μg/m3 for PM 2.5 and 70 μg/m3 for PM 10 in Grade II). The annual averages of PM 2.5 - and PM 10 -bound total PAHs were 63.1 and 66.8 ng/m3, respectively, with a PM 2.5 decrease in the order of winter (115 ng/m3) > > spring (47.6 ng/m3) > summer (33.2 ng/m3) > autumn (30.8 ng/m3) and a PM 10 decrease in the order of winter (127 ng/m3) > > spring (55.6 ng/m3) > autumn (32.6 ng/m3) > summer (30.2 ng/m3). The most abundant PAHs were benzo[ a ]anthracene, benzo[ b ]fluoranthene, and fluoranthene. The PM 2.5 - and PM 10 -bound PAHs were originated mainly from traffic emissions (51.0% and 43.4%), followed by combustion of biomass (20.4% and 23.6%) and coal (16.8% and 23.1%). Pressure and relative humidity were positively correlated with PM 2.5 and PM 10 as well as PM 2.5 - and PM 10 -bound PAHs, while temperature, visibility and wind speed had negative correlations. The annual means of TEQs (toxic equivalency quantities) for the 16 PAHs in PM 2.5 and PM 10 were 10.1 and 10.2 ng/m3, respectively, being attributed to 7 carcinogenic PAHs (> 95%). The ECRs (lifetime excess cancer risks) for PM 2.5 - and PM 10 -bound PAHs were 1.12 × 10−3 and 1.17 × 10−3, i.e., 1125 and 1169 lung cancer cases per million, respectively. The ILCRs (incremental lifetime cancer risks) due to PM 2.5 - and PM 10 -bound PAHs for adults (1.21 × 10−6 and 1.26 × 10−6) were larger than those for children (2.09 × 10−7 and 2.17 × 10−7), with acceptable carcinogenic risks. The ambient levels of PM and most PM-bound PAHs as well as their TEQs, ECRs and ILCRs exhibited a spatial pattern of the suburban site > the urban site and a seasonality with winter and spring > summer and autumn. The results suggest that it is important to control PM 2.5 and PM 10 for local air quality improvement and special attention should be paid to PM and PM-bound PAHs in suburban areas, particularly in winter and spring. • PM 2.5 - and PM 10 -bound PAHs were investigated in a semi-arid city, Xi'an of China. • PM and PM-bound PAH levels were higher in suburb, particularly in winter and spring. • PM-bound PAHs were dominated by high molecular weight PAHs, i.e., BaA, BbF and Fla. • Meteorological conditions had significant influences on the PM and PM-bound PAHs. • PM-bound PAHs incurred a high lung cancer risk in Xi'an relative to other study areas. [ABSTRACT FROM AUTHOR]

PM 2.5 and PM 10 samples were collected in the semi-arid city of Xi'an in Northwest China from November 2016 to November 2017 and analyzed to assess pollution characteristics, sources, health risks, and influencing factors of 6 priority phthalate esters (PAEs). The results showed that the sum of the 6 PAEs (Σ 6 PAEs) was 85.5 ng m−3 in PM 2.5 and 94.5 ng m−3 in PM 10 , being higher at the suburban site than the urban site and winter > spring > summer > autumn. The most abundant PAE was bis(2-ethylhexyl phthalate) (DEHP). PM 2.5 - and PM 10 -bound PAEs were associated mainly with the use of plasticizers plus the uses of cosmetics and personal care products, construction materials, and home furnishings. Temperature, relative humidity, and visibility had stronger influences on the concentrations of PM and PM-bound PAEs than pressure and wind speed. Pressure and relative humidity were positively correlated with the concentrations of PM and most of the PM-bound PAEs, while temperature, visibility and wind speed had negative correlations with the concentrations of PM and PM-bound PAEs. The non-carcinogenic risks of human inhalation exposure to PM-bound PAEs were in the range of 10−7 to 10−3, suggesting low non-cancer risks, which were higher at the suburban site than the urban site and higher to children than adults. The cancer risks of human inhalation exposure to PM-bound DEHP and butyl benzyl phthalate (BBP) were in the range of 10−12 to 10−10, suggesting low carcinogenic risks, being in the order of the suburban site > the urban site and DEHP > BBP. Special attention should be paid to long-term low dose exposure to PAEs in the suburb, especially in winter and spring. Image 1 • PM 2.5 - and PM 10 -bound PAEs were studied in the semi-arid city of Xi'an in China. •PM and PM-bound PAE levels were higher in suburb, especially in winter and spring. •PM-bound PAEs were mainly dominated by bis(2-ethylhexyl phthalate). •Meteorological conditions had important influences on PM and PM-bound PAEs contents. •Special concern should be paid to long-term low dose exposure to PM-bound PAEs. [ABSTRACT FROM AUTHOR]

As an important central city in western China, Xi'an has the worst atmospheric pollution record in China and many measures have been taken to improve the air quality in the past few years. In this study, PM 2.5 samples were collected across four seasons from 2017 to 2018 in Xi'an. Organic carbon and elemental carbon, water soluble ions, and elements were monitored to assess the air quality. The average annual PM 2.5 concentration was (134.9 ± 48.1 μg/m3), with the highest concentration in winter (188.8 ± 93.2 μg/m3), and lowest concentration in summer (71.2 ± 12.1 μg/m3). The secondary generation of sulfate (SO 4 2−) and nitrate (NO 3 −) was strong in spring, and secondary organic carbon (SOC) was formed in all seasons. The compositions of PM 2.5 changed greatly during a sandstorm occurred and the Spring Festival. The sandstorm played a positive role in removing local pollutant NO 3 −, but also increased the concentration of SO 4 2−, however both the concentration of SO 4 2− and NO 3 − greatly increased by secondary generation during Spring Festival. Potential source analysis showed that during the sandstorm, pollutants were transported over a long distance from the northwest of China, whereas it was mainly from the local and surrounded emissions during the Spring Festival. Except Ca2+ and geological dust (GM), the other components in PM 2.5 increased significantly on the day of the Spring Festival. During sampling time in Xi'an, the positive matrix factorization (PMF) model analysis showed that PM 2.5 mainly came from vehicle emission, coal combustion, and biomass burning. • The average annual PM 2.5 concentration in Xi'an has increased from 2004 to 2007, and gradually decreased from 2012 to 2018. • It has higher exposure levels in wintertime in Xi'an, especially during the pollution events with seasonal variations. • NO 3 – decreased and SO 4 2– increased during the sandstorm, whereas both SO 4 2– and NO 3 – increased during the Spring Festival. • As one of the three main sources for PM 2.5 in Xi'an, the contribution of vehicle emission has elevated in the past years. [ABSTRACT FROM AUTHOR]