Hemolytic Properties of Fine Particulate Matter (PM2.5) in In Vitro Systems.

Epidemiological studies have suggested that inhalation exposure to particulate matter (PM) air pollution, especially fine particles (i.e., PM2.5 (PM with an aerodynamic diameter of 2.5 microns or less)), is causally associated with cardiovascular health risks. To explore the toxicological mechanisms behind the observed adverse health effects, the hemolytic activity of PM2.5 samples collected during different pollution levels in Beijing was evaluated. The results demonstrated that the hemolysis of PM2.5 ranged from 1.98% to 7.75% and demonstrated a clear dose-response relationship. The exposure toxicity index (TI) is proposed to represent the toxicity potential of PM2.5, which is calculated by the hemolysis percentage of erythrocytes (red blood cells, RBC) multiplied by the mass concentration of PM2.5. In a pollution episode, as the mass concentration increases, TI first increases and then decreases, that is, TI (low pollution levels) < TI (heavy pollution levels) < TI (medium pollution levels). In order to verify the feasibility of the hemolysis method for PM toxicity detection, the hemolytic properties of PM2.5 were compared with the plasmid scission assay (PSA). The hemolysis results had a significant positive correlation with the DNA damage percentages, indicating that the hemolysis assay is feasible for the detection of PM2.5 toxicity, thus providing more corroborating information regarding the risk to human cardiovascular health.

Atmospheric microplastic deposition associated with GDP and population growth: Insights from megacities in northern China.

Microplastic (MP) pollution is evolving into one of the most pressing environmental concerns worldwide. This study assessed the impact of economic activities on atmospheric MP pollution across 17 megacities in northern China, analyzing the correlation between the deposition flux of atmospheric MPs and variables such as city population, gross domestic product (GDP), and industrial structure. The results have shown that the MP pollution is obviously impacted by human activities related to increased GDP, population, as well as tertiary service sector, in which the MP pollution shows most close relationship with the GDP growth. Polypropylene, polyamide, polyurethane, and polyethylene were identified as the primary components of atmospheric MPs. The average particle size of MPs in atmospheric dustfall is 78.3 µm, and the frequency of MP particles increases as the particle size decreases. The findings highlight the complex relationship between socio-economic development and atmospheric MP accumulation, providing essential insights for the formulation of targeted emission reduction strategies.

Microplastic atmospheric dustfall pollution in urban environment: Evidence from the types, distribution, and probable sources in Beijing, China.

Airborne microplastics (MPs) pollution is an environmental problem of increasing concern, due to the ubiquity, persistence and potential toxicity of plastics in the atmosphere. In recent years, most studies on MPs have focused on aquatic and sedimentary environments, but little research has been done on MPs in the urban atmosphere. In this study, a total of ten dustfall samples were collected in a transect from north to south across urban Beijing. The compositions, morphologies, and sizes of the MPs in these dustfall samples were determined by means of Laser Direct Infrared (LDIR) imaging and Field Emission Scanning Electron Microscopy (FESEM). The number concentrations of MPs in the Beijing dustfall samples show an average of 123.6 items/g. The MPs concentrations show different patterns in the central, southern, and northern zones of Beijing. The number concentration of MPs was the highest in the central zone (224.76 items/g), as compared with the southern zone (170.55 items/g), and the northern zone (24.42 items/g). The LDIR analysis revealed nine compositional types of MPs, including Polypropylene (PP), Polyamide (PA), Polystyrene (PS), Polyethylene (PE), Polyethylene Terephthalate (PET), Silicone, Polycarbonate (PC), Polyurethane (PU) and Polyvinylchloride (PVC), among which PP was overall dominant. The PP dominates the MPs in the central zone (76.3%), and the PA dominates the MPs in the southern zone (55.86%), while the northern zone had a diverse combination of MPs types. The morphological types of the individual MPs particle include fragments, pellets, and fibers, among which fragments are dominant (70.9%). FESEM images show the presence of aged MPs in the Beijing atmosphere, which could pose a yet unquantified health risk to Beijing's residents. The average size of the MPs in the Beijing samples is 66.62 µm. Our study revealed that the numbers of fibrous MPs increase with the decrease in size. This pollution therefore needs to be carefully monitored, and methods of decreasing the sources and mitigations developed.

Oxidative potential and water-soluble heavy metals of size-segregated airborne particles in haze and non-haze episodes: Impact of the "Comprehensive Action Plan" in China.

Air pollution is a major environmental health challenge in megacities, and as such a Comprehensive Action Plan (CAP) was issued in 2017 for Beijing, the capital city of China. Here we investigated the size-segregated airborne particles collected after the implementation of the CAP, intending to understand the change of oxidative potential and water-soluble heavy metal (WSHM) levels in 'haze' and 'non-haze' days. The DNA damage and the levels of WSHM were analyzed by Plasmid Scission Assay (PSA) and High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS) techniques. The PM mass concentration was higher in the fine particle size (0.43-2.1 µm) during haze days, except for the samples affected by mineral dust. The particle-induced DNA damage caused by fine sized particles (0.43-2.1 µm) exceeded that caused by the coarse sized particles (4.7-10 µm). The DNA damage from haze day particles significantly exceeded those collected on non-haze days. Prior to the instigation of the CAP, the highest value of DNA damage decreased, and DNA damage was seen in the finer size (0.43-1.1 µm). The Pearson correlation coefficient between the concentrations of water-soluble Pb, Cr, Cd and Zn were positively correlated with DNA damage, suggesting that these WSHM had significant oxidative potential. The mass concentrations of water-soluble trace elements (WSTE) and individual heavy metals were enriched in the finer particles between 0.43 µm to 1.1 µm, implying that smaller sized particles posed higher health risks. In contrast, the significant reduction in the mass concentration of water-soluble Cd and Zn, and the decrease of the maximum and average values of DNA damage after the CAP, demonstrated its effectiveness in restricting coal-burning emissions. These results have demonstrated that the Beijing CAP policy has been successful in reducing the toxicity of 'respirable' ambient particles.

Hydrocarbon Generation Potential and Depositional Setting of Eocene Oil-Prone Coaly Source Rocks in the Xihu Sag, East China Sea Shelf Basin.

The Xihu Sag in the East China Sea Shelf Basin is a focus for hydrocarbon exploration and development. Hydrocarbons in the Xihu Sag are believed to have mainly originated from coals in the Paleogene Pinghu Formation (shortened as Pinghu coal). In this study, the hydrocarbon generation potential, origin of organic matter, and depositional setting of the Pinghu coal were analyzed by means of optical microscopic analysis, bulk organic geochemistry, and molecular geochemistry analysis. The results reveal that the maceral compositions of the Pinghu coal are characterized by a predominance of vitrinite (73.91-96.13%) with relatively high contents of liptinite (1.47-23.02%) and only minor amounts of inertinite (0-5.18%). Type II-III kerogen and high values of TOC (total organic carbon) (8.24-56.77%), EOM (extractable organic matter) (14 601-112 259 ppm), and HI (hydrogen index) (178.76-291.18 mg·HC/g·TOC) indicate that the Pinghu coal is both gas- and oil-prone and could not only generate but also expel hydrocarbons. The results of vitrinite reflectance (0.54-0.90%), Tmax (421-453 °C), and biomarker-related parameters, including CPI (carbon preference index) (1.10-1.61), OEP (odd-to-even predominance) (1.09-1.49), 22S/(22S + 22R) for C31 homohopane (0.59-0.62), and 22S/(22S + 22R) for C32 homohopane (0.57-0.60), suggest that these coaly source rocks have entered the hydrocarbon generation threshold, most of which have entered the expulsion threshold. Biomarker-related parameters of ∑n-C21-/∑n-C22+ (0.38-3.62), Pr/Ph (3.33-9.23), Pr/n-C17 (1.91-14.88), Ph/n-C18 (0.35-1.83), 22S/(22S+22R) of C31 homohopane (0.59-0.62), 22S/(22S + 22R) of C32 homohopane (0.57-0.60), 1,2,7-TMN/1,3,7-TMN (0.74-14.39), and 1,2,5-TMN/1,3,6-TMN (2.22-21.07) suggest that organic matter in the Pinghu coal was deposited under relatively oxic peatland conditions characterized by a predominance of terrestrial higher plant input, especially the resin-rich Pinaceae and Taxodiaceae. The absence of combustion-derived PAHs indicates that neither vegetation fire nor peat fire occurred very frequently during the formation of peat. Areas in the Xihu sag with considerable thicknesses of coal should be paid particular attention for future hydrocarbon exploration. From a global perspective, Cenozoic coaly source rocks, which are characterized by a relatively high content of aliphatic components, should be paid special attention for their oil-prone properties related to the advent of conifer plants.

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.

Iron solubility in fine particles associated with secondary acidic aerosols in east China.

Soluble iron (FeS) in aerosols contributes to free oxygen radical generation with implications for human health, and potentially catalyzes sulfur dioxide oxidation. It is also an important external source of micronutrients for ocean ecosystems. However, factors controlling FeS concentration and its contribution to total iron (FeT) in aerosols remain poorly understand. Here, FeS and FeT in PM2.5 was studied at four urban sites in eastern China from 21 to 31 December, 2017. Average FeT (869-1490 ng m-3) and FeS (24-68 ng m-3) concentrations were higher in northern than southern China cities, but Fe solubility (%FeS, 2.7-5.0%) showed no spatial pattern. Correlation analyses suggested %FeS was strongly correlated with FeS and PM2.5 instead of FeT concentrations. Individual particle observations confirmed that more than 65% of nano-sized Fe-containing particles were internally mixed with sulfates and nitrates. Furthermore, there was a high correlation between sulfates or nitrates/FeT molar ratio and %FeS. We also found that the sulfates/nitrates had weaker effects on %FeS at RH < 50% than at RH > 50%, suggesting RH as indirect factor can influence %FeS in PM2.5. These results suggest an important role of chemical processing in enhancing %FeS in the polluted atmosphere.

Particle-induced oxidative damage by indoor size-segregated particulate matter from coal-burning homes in the Xuanwei lung cancer epidemic area, Yunnan Province, China.

Size-segregated samples of airborne particulate matter were collected at the coal-burning homes of the Hutou high lung cancer epidemic village and a comparison site Xize village of the Xuanwei County, Yuanan Province, by an Anderson Cascade Impact Sampler in winter and spring to study the toxicological characteristics of different-sized particles. The DNA damage caused by the water-soluble fractions of these size-segregated particles was analyzed by the plasmid scission assay, and the trace element compositions were determined by Inductively Coupled Plasma Mass Spectrometry. The DNA damage rate from the airborne particles in the high lung cancer incidence area was higher than that in Xize village. The different-sized particles have highly varying DNA damage rates, with the values being greater in the small size range than in the large size range. The particle-induced DNA damage rates had a significantly positive correlation with total water-soluble trace elements. Further analysis of the individual elements indicated that the water-soluble heavy metals Zn, Cu, Cd, Rb, Cs, and Sb had a positive correlation with the particle-induced DNA damage, implying that these water-soluble heavy metals played an important role in the DNA damage. The Sr had a negative correlation with the particle-induced DNA damage, suggesting that the water-soluble Sr might counter DNA damage. The mass concentrations of the total and individual water-soluble trace elements were mostly enriched in the small particle size ranges, thus implying the indoor airborne particles in the small size ranges would have a higher health risk.

Air pollution-aerosol interactions produce more bioavailable iron for ocean ecosystems.

It has long been hypothesized that acids formed from anthropogenic pollutants and natural emissions dissolve iron (Fe) in airborne particles, enhancing the supply of bioavailable Fe to the oceans. However, field observations have yet to provide indisputable evidence to confirm this hypothesis. Single-particle chemical analysis for hundreds of individual atmospheric particles collected over the East China Sea shows that Fe-rich particles from coal combustion and steel industries were coated with thick layers of sulfate after 1 to 2 days of atmospheric residence. The Fe in aged particles was present as a "hotspot" of (insoluble) iron oxides and throughout the acidic sulfate coating in the form of (soluble) Fe sulfate, which increases with degree of aging (thickness of coating). This provides the "smoking gun" for acid iron dissolution, because iron sulfate was not detected in the freshly emitted particles and there is no other source or mechanism of iron sulfate formation in the atmosphere.

Seasonal variation of particle-induced oxidative potential of airborne particulate matter in Beijing.

An in vitro plasmid scission assay (PSA), the cell apoptosis assay, and ICP-MS were employed to study the oxidative potentials and trace element compositions of the airborne particulate matter (PM) in Beijing during a one year-long field campaign from June 2010 to June 2011. The cell damages induced by PM reveled by the cell apoptosis assay showed a similar variation pattern to the DNA damages obtained by PSA, verifying the feasibility of the PSA in analyzing the oxidative capacity of PM samples. The PSA experiments showed that the particle-induced DNA damage was highest in summer, followed by spring, winter and autumn in descending order. The percentages of the oxidative damages to plasmid DNA induced by the water-soluble fractions of PM under the particle doses from 10 to 250µg/ml were generally lower than 45%, with some values peaking at above 50%. The peak values were frequently present in late spring (i.e. April and May) and early summer (i.e. June) but they were scarcely observed in other seasons. These peak values were mostly associated with haze days or the days with low wind speed (less than 4m/s), indicating that the PM samples during haze had higher oxidative potential than those during non-haze periods. The oxidative potential induced by the water-soluble fraction of the PM displayed a significant positive correlation with the concentrations of the water-soluble elements Cd, Cs, Pb, Rb, Zn, Be and Bi, demonstrating that the particle-induced oxidative potentials were mainly sourced from these elements. The exposure risk represented by the mass concentration of these elements in unit volume of atmosphere was higher in summer and winter, and lower in autumn and spring. The haze day PM samples not only had higher level of oxidative potentials but also had higher concentrations of water-soluble elements.

Source Apportionment of Elemental Carbon in Beijing, China: Insights from Radiocarbon and Organic Marker Measurements.

Elemental carbon (EC) or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In this study, radiocarbon ((14)C) based source apportionment is used to distinguish between fossil fuel and biomass burning sources of EC isolated from aerosol filter samples collected in Beijing from June 2010 to May 2011. The (14)C results demonstrate that EC is consistently dominated by fossil-fuel combustion throughout the whole year with a mean contribution of 79% ± 6% (ranging from 70% to 91%), though EC has a higher mean and peak concentrations in the cold season. The seasonal molecular pattern of hopanes (i.e., a class of organic markers mainly emitted during the combustion of different fossil fuels) indicates that traffic-related emissions are the most important fossil source in the warm period and coal combustion emissions are significantly increased in the cold season. By combining (14)C based source apportionment results and picene (i.e., an organic marker for coal emissions) concentrations, relative contributions from coal (mainly from residential bituminous coal) and vehicle to EC in the cold period were estimated as 25 ± 4% and 50 ± 7%, respectively, whereas the coal combustion contribution was negligible or very small in the warm period.

Soot particles at an elevated site in eastern China during the passage of a strong cyclone.

Atmospheric particles larger than 0.2 µm were collected at the top of Mt. Tai (36.25°N, 117.10°E, 1534 m a.s.l.) in eastern China in May 2008 during the passage of a strong cyclone. The particles were analyzed with electron microscopes and characterized by morphology, equivalent diameter and elemental composition. Soot particles with coating (coated soot particles) and those without apparent coating (naked soot particles) were predominant in the diameter range smaller than 0.6 µm in all samples. The number-size distribution of the relative abundance of naked soot particles in the prefrontal air was similar to that in the postfrontal air and their size modes were around 0.2-0.3 µm. However, the distribution of inclusions of coated soot particles showed a mode in the range of 0.1-0.3 µm. The coating degree of coated soot particles, which was defined by the ratio of the diameter of inclusion to the diameter of particle body, showed a mode around 0.5 with the range of 0.3-0.6. These results indicate that the status of soot particles in the prefrontal and postfrontal air was similar although air pollution levels were dramatically different. In addition, the relative abundance of accumulation mode particles increased with the decrease of soot particles after the front passage.

Internally mixed sea salt, soot, and sulfates at Macao, a coastal city in South China.

Direct observation of the mixing state of aerosol particles in a coastal urban city is critical to understand atmospheric processing and hygroscopic growth in humid air. Morphology, composition, and mixing state of individual aerosol particles from Macao, located south of the Pearl River Delta (PRD) and 100 km west of Hong Kong, were investigated using scanning electron microscopy (SEM) and transmission electron microscopy coupled with energy-dispersive X-ray spectrometry (TEM/EDX). SEM images show that soot and roughly spherical particles are prevalent in the samples. Based on the compositions of individual aerosol particles, aerosol particles with roughly spherical shape are classified into coarse Na-rich and fine S-rich particles. TEM/EDX indicates that each Na-rich particle consists of a Na-S core and NaNO3 shell. Even in the absence of heavy pollution, the marine sea salt particles were completely depleted in chloride, and Na-related sulfates and nitrates were enriched in Macao air. The reason could be that SO2 from the polluted PRD and ships in the South China Sea and NO2 from vehicles in the city sped up the chlorine depletion in sea salt through heterogeneous reactions. Fresh soot particles from vehicular emissions mainly occur near curbside. However, there are many aged soot particles in the sampling site surrounded by main roads 200 to 400 m away, suggesting that the fresh soot likely underwent a quick aging. Overall, secondary nitrates and sulfates internally mixed with soot and sea salt particles can totally change their surface hygroscopicity in coastal cities.

Silica-volatile interaction and the geological cause of the Xuan Wei lung cancer epidemic.

Parts of Xuan Wei County, Yunnan Province, China have the highest known lung cancer mortality in nonsmoking women. This high mortality displays a clear spatial relationship to the mines producing coal from the uppermost Permian. Geochemical, petrographic, and grainsize analyses were undertaken on a set of coal samples from Xuan Wei. Results demonstrate that the single geochemical property that makes this coal unusual is its high concentration of quartz (13.5 wt %) of which 35-55% occurs as <10 microm grains. We propose the potential for silica-volatile interaction (PSVI) as a new method for assessing the combined influence of silica and volatile organic matter and use this as a basis for re-evaluating existing ecological data. Published lung cancer mortality values are more strongly correlated with PSVI values for Xuan Wei coal than with volatiles or silica alone and the PSVI values measured are distinct from those of other coals. Finally we propose that the localization of this epidemic to Xuan Wei results from enhanced weathering of the local Emeishan basalts as a consequence of geochemical perturbations at the Permo-Triassic Boundary.