Respiratory absorption factors (AFs) are important parameters for assessing human health risks of long-term inhalation exposure to low-level hazardous air pollutants. However, it is uncertain whether previously measured respiratory AFs for high-level exposures could be directly applied. Here we measured real-time respiratory AFs using proton transfer reaction time-of-flight mass spectrometry for 50 subjects (20–30 years of age; 24 females and 26 males) exposed in a normal office room with aromatic hydrocarbons (AHs) at concentrations of several parts per billion by volume. The mean respiratory AFs of benzene, toluene, and C8-aromatics (ethylbenzene and xylenes) from all subjects were 28.2, 63.3, and 66.6%, respectively. No gender difference in the respiratory AFs of AHs was observed. Correlation analysis revealed that exposure concentration, rather than physiological parameters like body mass index or body fat ratio, was the dominant factor influencing the AFs of AHs. The results also demonstrated that respiratory AFs decreased in a logarithmic way when exposure levels of AHs were decreased. The decreased respiratory AFs at lowered exposure levels suggest the dual effect of reducing ambient air toxics like AHs with a decrease in human inhalation intake.

•The present study explored the effects of ambient PM2.5 on endothelial cell apoptosis and underlying molecular mechanism.•The PM2.5 may cause significant apoptosis to HUVECs in culture.•EC apoptosis can be used as a sensitive biomarker for PM2.5 exposure to cardiovascular system.•The p53-Bax-caspase pathway is the major way of PM2.5-mediated apoptosis in HUVECs.Exposure to airborne fine particulate matter (PM2.5) is associated with cardiovascular diseases (CVDs). Nevertheless, a comprehensive understanding of the underlying biological mechanisms by which PM2.5 exposure induces or aggravates CVDs remain insufficiently clear. In the present study, the flow cytometry was employed to investigate the apoptosis of human umbilical vein endothelial cells (HUVECs) induced by PM2.5 in culture. The underlying apoptotic pathway was also studied through the determination of the protein expression and activation of p53, Bax, Bcl-2, caspases-9, -7, -3, and PARP by western blot. The results showed that PM2.5 could significantly induce the apoptosis of HUVECs at the tested concentrations (0.2, 1, 5, 25 μg mL−1), compared with the negative control (p < 0.05, p < 0.01). The apoptotic rate of HUVECs increased with the elevating levels of PM2.5 exposure, showing a clear dose-effect relationship. Moreover, the increasing phosphorylation of p53, decreasing ratio of Bcl-2/Bax, and enhancing activation of the downstream proteins caspase-9, -7, -3 and PARP, were also observed with the increasing concentrations of PM2.5 administration in the western blot, indicating that the intracellular approach of apoptosis, the p53-Bax-caspases pathway, is the major way of PM2.5-induced apoptosis in HUVECs. In conclusion, these results suggested that induction of EC apoptosis is an important mechanism by which ambient PM2.5 exposure poses adverse effects on the cardiovascular system.Download high-res image (260KB)Download full-size image

•Photo-oxidation of toluene/SO2/NOx in chamber in ambient air versus in purified air.•Higher SOA productions and yields in matrix of ambient air than of purified air.•Enhanced SO2 degradation and sulfate formation in ambient air matrix.•Higher particle acidity in ambient air matrix promoted acid-catalyzed SOA formation.•Elevated OH levels observed in ambient air matrix than in purified air matrix.Chamber studies on the formation of secondary aerosols are mostly performed with purified air as matrix, it is of wide concern in what extent they might be different from the situations in ambient air, where a variety of gaseous and particulate components preexist. Here we compared the photo-oxidation of “toluene + NOx + SO2” combinations in a smog chamber in real urban ambient air matrix with that in purified air matrix. The secondary organic aerosols (SOA) mass concentrations and yields from toluene in the ambient air matrix, after subtracted ambient air background primary and secondary organic aerosols, were 9.0–34.0 and 5.6–12.9 times, respectively, greater than those in purified air matrix. Both homogeneous and heterogeneous oxidation of SO2 were enhanced in ambient air matrix experiments with observed 2.0–7.5 times higher SO2 degradation rates and 2.6–6.8 times faster sulfate formation than that in purified air matrix, resulting in higher in-situ particle acidity and consequently promoting acid-catalyzed SOA formation. In the ambient air experiments although averaged OH radical levels were elevated probably due to heterogeneous formation of OH on particle surface and/or ozonolysis of alkenes, non-OH oxidation pathways of SO2 became even more dominating. Under the same organic aerosol mass concentration, the SOA yields of toluene in purified air matrix experiments matched very well with the two-product model curve by Ng et al. (2007), yet the yields in ambient air on average was over two times larger. The results however were much near the best fit curve by Hildebrandt et al. (2009) with the volatility basis set (VBS) approach.

Volatile organic compounds (VOCs), carbon monoxide (CO), and PM10 were studied by field sampling in six underground car parks beneath multi-level buildings in Guangzhou, China. CO and PM10 in the car parks range from 3.0 to 69.0 ppm and 0.087 to 0.698 mg m−3, with mean concentrations of 10.8 ppm and 0.228 mg m−3, respectively. Overall mean concentrations of methyl tertiary-butyl ether (MTBE), benzene, toluene, ethyl-benzene, and xylene (BTEX) are 90.5, 54.8, 239.9, 47.7, and 189.3 μg m−3, respectively. Indoor air pollutants in the car parks show an obvious seasonal variation and are higher in winter than in summer. The total estimated cancer risks of occupational exposure for car park staff and casual exposure for parking users are 3.73 × 10−4 and 5.60 × 10−6, indicating definite and possible risks, respectively. The hazard quotient of target VOCs is 4.33, implying a definite risk for people using underground car parks. Indoor/outdoor (I/O) ratios for MTBE and BTEX are significantly higher than one, reflecting strong emission sources in underground car parks. The BTEX to MTBE ratios in the car parks are almost the same as those in tunnel air, indicating that indoor aromatic hydrocarbons were mainly from engine emissions and gasoline evaporation. With increasing urbanization in China, more attention should be paid to the exposure of staff and users to hazardous air pollutants in underground car parks.

China has the world’s largest population of smokers with serious health consequences, yet we know a very limited spectrum of hazardous chemicals in cigarette smoke even for carcinogenic polycyclic aromatic hydrocarbons (PAHs). Here, we chose 13 popular cigarette brands sold in China markets, collected particulate matters in mainstream smoke using filter pads and an automatic smoking machine, and analyzed 56 PAHs, including 31 parent, 18 alkylated, and 7 sulfur/oxygen-containing PAHs (S/O PAHs). The 56 PAHs in mainstream smoke totaled from 244.2 ± 28.5 to 10254.8 ± 481.5 ng cig–1; parent, alkylated, and S/O PAHs shared 16–23%, 64–74%, and 6–18%, respectively. Benzo[a]pyrene (BaP) ranged 1.1–41.6 ng cig–1, while BaP equivalent concentrations (BaPeq) ranged 3.6–120.2 ng cig–1, but contributions to BaPeq by individual carcinogenic PAH species varied with cigarette brands. When these cigarette smoke source profiles were pooled together with those of other combustion ones available in the literature, we found that widely used diagnostic ratios of parent PAHs failed to distinguish cigarette smoke from other combustion sources, except that the ratio indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene + benzo[g,h,i]perylene) can largely separate cigarette smoke from vehicular emissions and that the ratio of Retene/(Retene + chrysene) can further discriminate cigarette smoke from coal combustion when alkylated PAHs are involved.

Ammonia (NH3) plays vital roles in new particle formation and atmospheric chemistry. Although previous studies have revealed that it also influences the formation of secondary organic aerosols (SOA) from ozonolysis of biogenic and anthropogenic volatile organic compounds (VOCs), the influence of NH3 on particle formation from complex mixtures such as vehicle exhausts is still poorly understood. Here we directly introduced gasoline vehicles exhausts (GVE) into a smog chamber with NH3 absorbed by denuders to examine the role of NH3 in particle formation from GVE. We found that removing NH3 from GVE would greatly suppress the formation and growth of particles. Adding NH3 into the reactor after 3 h photo-oxidation of GVE, the particle number concentration and mass concentrations jumped explosively to much higher levels, indicating that the numbers and mass of particles might be enhanced when aged vehicle exhausts are transported to rural areas and mixed with NH3-rich plumes. We also found that the presence of NH3 had no significant influence on SOA formation from GVE. Very similar oxygen to carbon (O:C) and hydrogen to carbon (H:C) ratios resolved by aerosol mass spectrometer with and without NH3 indicated that the presence of NH3 also had no impact on the average carbon oxidation state of SOA from GVE.

During the 2003 Chinese Arctic Research Expedition (CHINARE2003) from the Bohai Sea to the high Arctic (37°N–80°N), filter-based particle samples were collected and analyzed for tracers of primary and secondary organic aerosols (SOA) as well as water-soluble organic carbon (WSOC). Biomass burning (BB) tracer levoglucosan had comparatively much higher summertime average levels (476 ± 367pg/m3) during our cruise due to the influence of intense forest fires then in Siberia. On the basis of 5-day back trajectories, samples with air masses passing through Siberia had organic tracers 1.3–4.4 times of those with air masses transporting only over the oceans, suggesting substantial contribution of continental emissions to organic aerosols in the marine atmosphere. SOA tracers from anthropogenic aromatics were negligible or not detected, while those from biogenic terpenenoids were ubiquitously observed with the sum of SOA tracers from isoprene (623 ± 414pg/m3) 1 order of magnitude higher than that from monoterpenes (63 ± 49 pg/m3). 2-Methylglyceric acid as a product of isoprene oxidation under high-NOx conditions was dominant among SOA tracers, implying that these BSOA tracers were not formed over the oceans but mainly transported from the adjacent Siberia where a high-NOx environment could be induced by intense forest fires. The carbon fractions shared by biogenic SOA tracers and levoglucosan in WSOC in our ocean samples were 1–2 orders of magnitude lower than those previously reported in continental samples, BB emissions or chamber simulation samples, largely due to the chemical evolution of organic tracers during transport. As a result of the much faster decline in levels of organic tracers than that of WSOC during transport, the trace-based approach, which could well reconstruct WSOC using biogenic SOA and BB tracers for continental samples, only explained ∼4% of measured WSOC during our expedition if the same tracer-WSOC or tracer-SOC relationships were applied.

The release of isoprene and 12 monoterpenes during the decomposition of orange wastes was studied under controlled aerobic conditions in laboratory for a period of 2 months. Monoterpenes (mainly limonene, β-myrcene, sabinene, and α-pinene) dominated among the released volatile organic compounds, but isoprene was only a very minor constituent. Two time windows with peak microbial activity were indicated by CO2 emission fluxes and waste temperature, both of which reached their maximums 3–4 days and 15–20 days after the incubation, respectively. Although isoprene had only one emission peak synchronizing with the first peak microbial activity, monoterpenes had relatively high emission rates, but they decreased at the beginning without correlation to the first peak of microbial activity, due largely to direct volatilization of these monoterpenes primarily present in orange substrates as inherited constituents. However, after the initial decrease the emission rates of monoterpenes rose again in conjunction with the second peak of microbial activity, indicating secondary production of these monoterpenes through microbial activity. On the basis of monitored emission fluxes, the amounts of secondarily formed monoterpenes from microbial activity well surpassed those inherited in the orange wastes. Production of total terpenes reached 1.10 × 104 mg kg−1 (dry weight), of which limonene alone was 63%. For either limonene or total terpenes, about 95% of their emission occurred in the first 30 days, implying that organic wastes might give off considerable amount of terpenes during early disposal under aerobic conditions before the conventional anaerobic landfilling, and emission measurements just in landfills might underestimate the waste-related emissions of reactive organic gases.

On a global scale tropical regions in developing countries are thought to be significant source areas of organochlorine pesticides (OCPs), owing to a long history of widespread use and only a recent production ban or restriction on the application of these pesticides. In the present study, 32 soil samples were collected in 2004 from agriculture lands around the urban area of Guangzhou, in southern China, and analyzed for residues of OCPs including p,p’-DDT, p,p’-DDE, p,p’-DDD, and α-, β-, γ-, and δ-HCH. The dry weight concentrations of ΣHCH (ΣHCH = α-HCH + β-HCH + γ-HCH + δ-HCH) ranged from 0.2 to 103.9 ng/g, with a median of 4.4 ng/g. Residues of ΣDDT (ΣDDT = p,p’-DDT + p,p’-DDE + p,p’-DDD) ranged from 7.6 to 662.9 ng/g, with a median of 67.3 ng/g. The predominance of β-HCH among HCHs in most soil samples suggested that they were from historical contamination rather than recent input. The mean HCH α/γ-ratio of 2.72 was lower than that of technical HCHs, possibly due to more loss of α-HCH via evaporation from soil with time, conversion of γ-HCH to α-HCH or recent application of lindane in the region. The mean ratio of (DDE + DDD)/ΣDDT was 0.54, indicating that quite a portion of DDT in soils was degraded since its official ban in 1983. Higher DDT concentrations with lower (DDE + DDD)/ΣDDT ratios at a few sites suggested possible local DDT sources via the application of Dicofol. A positive but weak correlation (r = 0.449, p < 0.01) between DDT residues and TOC contents implied that soil organic matter might enhance adsorption of DDT in soils in the tropical regions. Hierarchical cluster analysis and principal component analysis were also performed to study the distribution and compositional patterns of OCPs as well as their sources and environemtal fates within the study area.

A laboratory study was conducted to investigate volatile organic compound (VOC) emissions from agricultural soil amended with wheat straw and their associations with bacterial communities for a period of 66 days under non-flooded and flooded conditions. The results indicated that ethene, propene, ethanol, i-propanol, 2-butanol, acetaldehyde, acetone, 2-butanone, 2-pentanone and acetophenone were the 10 most abundant VOCs, making up over 90% of the total VOCs released under the two water conditions. The mean emission of total VOCs from the amended soils under the non-flooded condition (5924 ng C/(kg·hr)) was significantly higher than that under the flooded condition (2211 ng C/(kg·hr)). One “peak emission window” appeared at days 0–44 or 4–44, and over 95% of the VOC emissions occurred during the first month under the two water conditions. Bacterial community analysis using denaturing gradient gel electrophoresis (DGGE) showed that a relative increase of Actinobacteria, Bacteroidetes, Firmicutes and γ-Proteobacteria but a relative decrease of Acidobacteria with time were observed after straw amendments under the two water conditions. Cluster analysis revealed that the soil bacterial communities changed greatly with incubation time, which was in line with the variation of the VOC emissions over the experimental period. Most of the above top 10 VOCs correlated positively with the predominant bacterial species of Bacteroidetes, Firmicutes and Verrucomicrobia but correlated negatively with the dominant bacterial species of Actinobacteria under the two water conditions. These results suggested that bacterial communities might play an important role in VOC emissions from straw-amended agricultural soils.Download full-size image

Carbonyl sulfide (OCS) and dimethyl sulfide (DMS) are important trace gases contributing to sulfate aerosol formation in the lower and upper atmosphere and hence greatly impacting global radiative balance. In the present study the exchange of OCS and DMS between rice (Oryza sativa L.) paddy fields and the atmosphere was studied in subtropical China from November 2004 to July 2005. OCS and DMS fluxes were compared between the planted and non-planted paddy fields, and between dry and waterlogged soils. The rice paddy fields were found to be a net sink for OCS and a source for DMS, with an uptake rate of 12.1 ± 16.0 pmol m−2 s−1 for OCS and an emission rate of 25.9 ± 35.2 pmol m−2 s−1 for DMS. OCS fluxes varied significantly between non-planted dry and waterlogged soils, with an uptake rate of 11.4 ± 7.1 pmol m−2 s−1 for non-planted dry soils and an emission rate of 9.0 ± 5.4 pmol m−2 s−1 for non-planted waterlogged soils. For DMS the variation between non-planted dry and waterlogged soils was not significant. Both OCS and DMS fluxes showed significant differences between the planted and non-planted waterlogged soils. For OCS, the planted waterlogged soil acted as a sink with an uptake rate of 29.0 ± 25.7 pmol m−2, but the non-planted waterlogged soil acted as a source with an emission rate of 9.0 ± 5.4 pmol m−2 s−1. For DMS, both the planted and non-planted waterlogged soils acted as sources, with an emission rate of 51.2 ± 37.5 pmol m−2 s−1 for the planted waterlogged soil, which was significantly higher than that for the non-planted waterlogged soil (3.8 ± 2.8 pmol m−2 s−1). OCS and DMS exchange rates differed significantly at different rice growth stages, with the highest fluxes at the jointing-booting stage. The potential factors causing the variations between the different treatments are also discussed. This work revealed that rice paddy field in subtropical China acts as a sink for OCS and an emission source for DMS as a whole and further investigation on the influence of soil microorganisms and soil redox potential on the OCS and DMS fluxes in rice paddy field are needed.

In fall–winter, 2007–2013, visibility and light scattering coefficients (bsp) were measured along with PM2.5 mass concentrations and chemical compositions at a background site in the Pearl River Delta (PRD) region. The daily average visibility increased significantly (p < 0.01) at a rate of 1.1 km/year, yet its median stabilized at ~ 13 km. No haze days occurred when the 24-hr mean PM2.5 mass concentration was below 75 μg/m3. By multiple linear regression on the chemical budget of particle scattering coefficient (bsp), we obtained site-specific mass scattering efficiency (MSE) values of 6.5 ± 0.2, 2.6 ± 0.3, 2.4 ± 0.7 and 7.3 ± 1.2 m2/g, respectively, for organic matter (OM), ammonium sulfate (AS), ammonium nitrate (AN) and sea salt (SS). The reconstructed light extinction coefficient (bext) based on the Interagency Monitoring of Protected Visual Environments (IMPROVE) algorithm with our site-specific MSE revealed that OM, AS, AN, SS and light-absorbing carbon (LAC) on average contributed 45.9% ± 1.6%, 25.6% ± 1.2%, 12.0% ± 0.7%, 11.2% ± 0.9% and 5.4% ± 0.3% to light extinction, respectively. Averaged bext displayed a significant reduction rate of 14.1/Mm·year (p < 0.05); this rate would be 82% higher if it were not counteracted by increasing relative humidity (RH) and hygroscopic growth factor (f(RH)) at rates of 2.5% and 0.16/year − 1 (p < 0.01), respectively, during the fall–winter, 2007–2013. This growth of RH and f(RH) partly offsets the positive effects of lowered AS in improving visibility, and aggravated the negative effects of increasing AN to impair visibility.Download full-size image

Information about soil nitric oxide (NO) emissions from subtropical forests is quite limited, and even less is known about the pulse emission of NO when wetting soils after a long period of dryness. In this study, we measured NO fluxes following wetting of dry soil in a broadleaf forest and a pine forest in subtropical China. Large pulses of NO fluxes were observed after soil wetting in both forests. NO fluxes increased significantly within 0.5 h following wetting in both forests and reached peak 1 and 4 h after soil wetting in the pine forest and the broadleaf forest, respectively. In the broadleaf forest, averaged peak flux of NO pulses was 157 ng N m−2 s−1, which was 8 times the flux value before wetting, and in the pine forest, the averaged peak flux was 135 ng N m−2 s−1, which was 15.5 times the flux value before wetting. The total pulses-induced NO emissions during the dry season were roughly estimated to be 29.4 mg N m−2 in the broadleaf forest and 22.2 mg N m−2 in the pine forest or made up a proportion of 4.6% of the annual NO emission in the broadleaf forest and 5.3% in the pine forest.

•24-h PM2.5 samples were collected in fall-winter of 2007–2012.•The annual reduction trends of [H+]total and [H+]in-situ of PM2.5 was −32 ± 1.5 and −9 ± 1.7 nmol m−3, respectively.•On hazy days, the concentration of OM showed significant enhancement when [H+]in-situ ranged from 85 to 240 nmol m−3.•[H+]in-situ presented a close relationship with NO3− formation mechanisms in low and high acidity of PM2.5.Based on field observations and thermodynamic model simulation, the annual trend of PM2.5 acidity and its characteristics on non-hazy and hazy days in fall-winter of 2007–2012 in the Pearl River Delta region were investigated. Total acidity ([H+]total) and in-situ acidity ([H+]in-situ) of PM2.5 significantly decreased (F-test, p < 0.05) at a rate of −32 ± 1.5 nmol m−3 year−1 and −9 ± 1.7 nmol m−3 year−1, respectively. The variation of acidity was mainly caused by the change of the PM2.5 component, i.e., the decreasing rates of [H+]total and [H+]in-situ due to the decrease of sulfate (SO42−) exceeded the increasing rate caused by the growth of nitrate (NO3−). [H+]total, [H+]in-situ and liquid water content on hazy days were 0.9–2.2, 1.2–3.5 and 2.0–3.0 times those on non-hazy days, respectively. On hazy days, the concentration of organic matter (OM) showed significant enhancement when [H+]in-situ increased (t-test, p < 0.05), while this was not observed on non-hazy days. Moreover, when the acidity was low (i.e., R = [NH4+]/(2 × [SO42−] + [NO3−]) > 0.6), NH4NO3 was most likely formed via homogenous reaction. When the acidity was high (R ≤ 0.6), the gas-phase formation of NH4NO3 was inhibited, and the proportion of NO3− produced via heterogeneous reaction of N2O5 became significant.

•Primary and secondary OA of diesel exhaust characterized with a smog chamber.•Much higher primary and secondary OA from diesel vehicles than gasoline ones•Higher diesel vehicle primary emission and secondary production of OA in China•Traditional precursor VOCs explained less than 3% SOA formed during aging.•Particle number emission factors of 0.65–4.0 × 1015 # kg-fuel− 1 for diesel vehiclesIn China diesel vehicles dominate the primary emission of particulate matters from on-road vehicles, and they might also contribute substantially to the formation of secondary organic aerosols (SOA). In this study tailpipe exhaust of three typical in-use diesel vehicles under warm idling conditions was introduced directly into an indoor smog chamber with a 30 m3 Teflon reactor to characterize primary emissions and SOA formation during photo-oxidation. The emission factors of primary organic aerosol (POA) and black carbon (BC) for the three types of Chinese diesel vehicles ranged 0.18–0.91 and 0.15–0.51 g kg-fuel− 1, respectively; and the SOA production factors ranged 0.50–1.8 g kg-fuel− 1 and SOA/POA ratios ranged 0.7–3.7 with an average of 2.2. The fuel-based POA emission factors and SOA production factors from this study for idling diesel vehicle exhaust were 1–3 orders of magnitude higher than those reported in previous studies for idling gasoline vehicle exhaust. The emission factors for total particle numbers were 0.65–4.0 × 1015 particles kg-fuel− 1, and particles with diameters less than 50 nm dominated in total particle numbers. Traditional C2-C12 precursor non-methane hydrocarbons (NMHCs) could only explain less than 3% of the SOA formed during aging and contribution from other precursors including intermediate volatile organic compounds (IVOC) needs further investigation.Download high-res image (170KB)Download full-size image

Oxygenated volatile organic compounds (OVOCs) emitted from orange wastes during aerobic decomposition were investigated in a laboratory-controlled incubator for a period of two months. Emission of total OVOCs (TOVOCs) from orange wastes reached 1714 mg/dry kg (330 mg/wet kg). Ethanol, methanol, ethyl acetate, methyl acetate, 2-butanone and acetaldehyde were the most abundant OVOC species with shares of 26.9%, 24.8%, 20.3%, 13.9%, 2.8% and 2.5%, respectively, in the TOVOCs released. The emission fluxes of the above top five OVOCs were quite trivial in the beginning but increased sharply to form one “peak emission window” with maximums at days 1–8 until leveling off after 10 days. This type of “peak emission window” was synchronized with the CO2 fluxes and incubation temperature of the orange wastes, indicating that released OVOCs were mainly derived from secondary metabolites of orange substrates through biotic processes rather than abiotic processes or primary volatilization of the inherent pool in oranges. Acetaldehyde instead had emission fluxes decreasing sharply from its initial maximum to nearly zero in about four days, suggesting that it was inherent rather than secondarily formed. For TOVOCs or all OVOC species except 2-butanone and acetone, over 80% of their emissions occurred during the first week, implying that organic wastes might give off a considerable amount of OVOCs during the early disposal period under aerobic conditions.Download full-size image