Characterization of peroxyacetyl nitrate (PAN) under different PM2.5 concentration in wintertime at a North China rural site.

As a secondary pollutant of photochemical pollution, peroxyacetyl nitrate (PAN) has attracted a close attention. A four-month campaign was conducted at a rural site in North China Plain (NCP) including the measurement of PAN, O3, NOx, PM2.5, oxygenated volatile organic compounds (OVOCs), photolysis rate constants of NO2 and O3 and meteorological parameters to investigate the wintertime characterization of photochemistry from November 2018 to February 2019. The results showed that the maximum and mean values of PAN were 4.38 and 0.93 ± 0.67 ppbv during the campaign, respectively. The PAN under different PM2.5 concentrations from below 75 µg/m3 up to 250 µg/m3, showed different diurnal variation and formation rate. In the PM2.5 concentration range of above 250 µg/m3, PAN had the largest daily mean value of 0.64 ppbv and the fastest production rate of 0.33 ppbv/hr. From the perspective of PAN's production mechanism, the light intensity and precursors concentrations under different PM2.5 pollution levels indicated that there were sufficient light intensity and high volatile organic compounds (VOCs) and NOx precursors concentration even under severe pollution level to generate a large amount of PAN. Moreover, the bimodal staggering phenomenon of PAN and PM2.5 provided a basis that PAN might aggravate haze through secondary organic aerosols (SOA) formation.

Compositions, sources, and potential health risks of volatile organic compounds in the heavily polluted rural North China Plain during the heating season.

Severe volatile organic compound (VOC) pollution has become an urgent problem during the heating season in the North China Plain (NCP), as exposure to hazardous VOCs can lead to chronic or acute diseases. A campaign with online VOC measurements was conducted at a rural site in Wangdu, NCP during the 2018 heating season to characterize the compositions and associated sources of VOCs and to assess their potential health risks. The total concentration of VOCs with 94 identified species was 77.21 ± 54.39 ppb. Seven source factors were identified by non-negative matrix factorization, including coal combustion (36.1%), LPG usage (21.1%), solvent usage (13.9%), biomass burning and secondary formation (14.2%), background (7.0%), industrial emissions (4.5%), and vehicle emissions (3.3%). The point estimate approach and Monte Carlo simulation were used to estimate the carcinogenic and non-carcinogenic risks of harzadous VOCs. The results showed that the cumulative health risk of VOCs was above the safety level. Acrolein, 1.2-dichloroethane, 1,2-dichloropropane, chloroform, 1,3-butadiene, and benzene were identified as the key hazardous VOCs in Wangdu. Benzene had the highest average carcinogenic risk. Solvent usage and secondary formation were the dominant sources of adverse health effects. During the Spring Festival, most sources were sharply reduced; and VOC concentration declined by 49%. However, coal and biomass consumptions remained relatively large, probably due to heating demand. This study provides important references for the control strategies of VOCs during the heating season in heavily polluted rural areas in the NCP.

Contribution of transregional transport to particle pollution and health effects in Shanghai during 2013-2017.

Transregional transport plays an important role in air pollution. This study investigated the impact of transregional transport on particle pollution in Shanghai from 2013 to 2017. A conditional potential source contribution function (CPSCF) method with high time resolution (1 h) PM2.5 and PM10 data was used to quantify the contribution of transregional transport. The corresponding health impact was also assessed. The average annual contribution of transregional transport to PM2.5 (PM2.5_CTRT) and PM10 (PM10_CTRT) was 22 and 30 µg/m3, 18 and 24 µg/m3, 19 and 24 µg/m3, 14 and 19 µg/m3, and 14 and 19 µg/m3, for 2013 to 2017, respectively, thus accounting for 31-37% of total PM2.5 and PM10. As PM2.5_CTRT is a dominant component of PM10_CTRT, the health effects related to PM2.5_CTRT were assessed to avoid double counting. The number of annual deaths associated with PM2.5_CTRT in Shanghai during the study period ranged from 636 (95% confidence intervals: 350, 936) to 1039 (573, 1530), among which cardiovascular disease and respiratory disease accounted for 62.8-67.6% and 16.6-19.5% of mortality, respectively. PM2.5_CTRT-related deaths accounted for 5.3-8.2‰ of the total mortality in Shanghai during the study period. Between 9764 (9251, 10,277) and 12,190 (11,549, 12,830) cases of all-cause hospital admissions were attributable to PM2.5_CTRT in Shanghai in one year, among which cardiovascular disease and respiratory disease hospital admissions accounted for 15.9-20.0% and 7.9-9.2%, respectively. Internal medicine and pediatrics outpatient visits related to PM2.5_CTRT ranged from 70,684 (39,009, 100,829) to 97,380 (53,788, 138,793) cases and 23,185 (8302, 37,173) to 32,702 (11,726, 52,361) cases, respectively. The current work provides scientific evidence of the impact of transregional transport on air pollution and its health burden in Shanghai.