Gas-PM2.5 partitioning, health risks, and sources of atmospheric PAHs in a northern China city: Impact of domestic heating

Pollution characteristics, source apportionment and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity of China

Polycyclic aromatic hydrocarbons (PAHs) have the capability for solar radiation absorption related to climate forcing. Herein, pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles in a cold megacity were comprehensively investigated. The mean concentrations of Σ18PAHs in all the 11 particle size ranges were 3.95 ± 4.77 × 104 pg/m3 and 2.17 ± 1.54 × 103 pg/m3 in heating period (HP) and non-heating period (NHP), respectively. Except for most PAHs with 2 and 3 benzene rings in NHP, most other PAHs showed a unimodal distribution pattern with the peak at 0.56-1.0 µm in both periods, which was caused by PAH emission sources. The PAH-related climate forcing was mainly caused by the solar radiation absorptions at ∼325 (∼330) nm and ∼365 nm. In general, the absorption intensities were higher in HP than NHP. The absorption intensity in the particle size range of 0.56-1.0 µm was the highest, and benzo[e]pyrene was the dominant contributor. In colder periods in HP, higher PAH concentrations caused more intensive PAH-related climate forcing. This study provided new insights for pollution characteristics and absorption spectra of size-resolved PAHs in atmospheric particles, which will be useful for better understanding PAH-related climate forcing.

Characteristics, sources and health risk assessment of trace metals and polycyclic aromatic hydrocarbons in PM2.5 from Hefei, China

Trace metals (TRs) and polycyclic aromatic hydrocarbons (PAHs) are major toxic components of fine particulate matter (PM2.5) and related to various health adverse outcomes. The study aims to get a better understanding of the contents, sources and risks of PM2.5-bounded TRs and PAHs in Hefei, China, during the period of 2019-2021. We collected 504 samples and measured twelve TRs and sixteen priority PAHs by inductively coupled plasma mass spectrometry and high-performance liquid chromatography. The annual mass concentrations of PM2.5 was fluctuated in the year of 2019-2021 at 50.95, 47.48 and 59.38 μg/m3, with seasonal variations in rank order of winter > spring > autumn > summer. The median concentrations of PM2.5-bounded ƩTRs and ƩPAHs were also fluctuated, 132.85, 80.93 and 120.27 ng/m3 for ƩTRs, 2.57, 5.85 and 2.97 ng/m3 for ƩPAHs, in the year of 2019, 2020 and 2021, respectively. Seasonal variations of ƩTRs and ƩPAHs show the highest concentration in winter. Positive matrix factorization was used for identified pollution emission sources, and TRs mainly originated from coal combustion, traffic emission and fugitive dust, while PAHs stemmed from biomass, diesel, gasoline and coal combustion. Health risk assessment indicated that adults were more vulnerable than children, the carcinogenic risk assessment of As and Cr manifested a certain degree of cancer risk (1.0 × 10-6 < CR < 1.0 × 10-4) in adults group, and health risks of TRs were higher than PAHs in Hefei. These findings suggest that PM2.5-bounded TRs and PAHs should be considered when making emission control strategies for air pollution, and winter, combustion sources and adults should achieve more policy attention to decrease exposure risks in Hefei.

Household characteristics associated with environmentally persistent free radicals in house dust in two Australian locations

The association between air pollution and adverse health outcomes has been extensively studied, and while oxidative stress in likely to be involved, the underlying mechanism(s) remain unclear. Recent studies propose environmentally persistent free radicals (EPFRs) as the missing connection between air pollution and detrimental health impacts. However, the indoor environment is rarely considered in EPFR research. We measured EPFRs in household dust from two locations in Australia and investigated household characteristics associated with EPFRs. Random forest models were built to identify important household characteristics through variable importance plots and the associations were analysed using Spearman's rho test. We found that age of house, type of garage, house outer wall material, heating method used in home, frequency of extractor fan use when cooking, traffic related air pollution, frequency of cleaning and major house renovation were important household characteristics associated with EPFRs in Australian homes. The direction of association between household characteristics and EPFRs differ between the locations. Hence, further research is warranted to determine the generalisability of our results.

Pollution characteristics and light-driven evolution of environmentally persistent free radicals in PM2.5 in two typical northern cities of China

Environmentally persistent free radicals (EPFRs) in PM_2.5 can pose significant health risks by generating reactive oxygen species (ROS). In this study, Beijing and Yuncheng were chosen as two representative northern cities of China that mainly relied on natural gas and coal respectively as the energy source for domestic heating in winter. The pollution characteristics and exposure risks of EPFRs in PM_2.5 around the heating season of 2020 were investigated and compared between the two cities. Through laboratory simulation experiments, the decay kinetics and secondary formation of EPFRs in PM_2.5 collected in both cities were also studied. EPFRs in PM_2.5 collected in Yuncheng in the heating period showed longer lifetime and lower reactivity, suggesting that EPFRs originated from coal combustion were more stable in the atmosphere. However, the generation rate of hydroxyl radical (·OH) by the newly formed EPFRs in PM_2.5 in Beijing under ambient conditions was 4.4 times of that in Yuncheng, suggesting higher oxidative potential of EPFRs from the atmospheric secondary processes. Accordingly, the control strategies of EPFRs and their health risks were raised for the two cities, which would also have direct implication for the control of EPFRs in other areas of similar atmospheric emission and reaction patterns.