Yuanxun Zhang

Source profiles of particulate organic matters emitted from cereal straw burnings

Cereal straw is one of the most abundant biomass burned in China but its contribution to fine particulates is not adequately understood. In this study, three main kinds of cereal straws were collected from five grain producing areas in China. Fine particulate matters (PM2.5) from the cereal straws subjected to control burnings, both under smoldering and flaming status, were sampled by using a custom made dilution chamber and sampling system in the laboratory. Element carbon (EC) and organic carbon (OC) was analyzed. 141 compounds of organic matters were measured by gas chromatography-mass spectrum (GC-MS). Source profiles of particulate organic matters emitted from cereal straw burnings were obtained. The results indicated that organic matters contribute a large fraction in fine particulate matters. Levoglucosan had the highest contributions with averagely 4.5% in mass of fine particulates and can be considered as the tracer of biomass burnings. Methyloxylated phenols from lignin degradation also had high concentrations in PM2.5, and contained approximately equal amounts of guaiacyl and syringyl compounds. beta-Sitostrol also made up relatively a large fraction of PM2.5 compared with the other sterols (0.18%-0.63% of the total fine particle mass). Normal alkanes, PAHs, fatty acids, as well as normal alkanols had relatively lower concentrations compared with the compounds mentioned above. Carbon preference index (CPI) of normal alkanes and alkanoic acids showed characteristics of biogenic fuel burnings. Burning status significantly influenced the formations of EC and PAHs. The differences between the emission profiles of straw and wood combustions were displayed by the fingerprint compounds, which may be used to identify the contributions between wood and straw burnings in source apportionment researches.

Highway proximity and black carbon from cookstoves as a risk factor for higher blood pressure in rural China

Significance Air pollution is a leading health risk factor and important contributor to regional climate change in China and other parts of Asia. China’s particulate matter (PM) air pollution dramatically exceeds health guidelines and is impacted by industrial emissions, motor vehicles, and household use of biomass and coal fuels. Black carbon (BC) from biomass and fossil fuel burning is a major climate-forcing component of PM. We found that BC exposure from biomass smoke is more strongly associated with blood pressure than total PM mass, and that coexposure to motor vehicle emissions may strengthen BC’s impact. Air pollution mitigation efforts focusing on reducing combustion pollution are likely to have major benefits for climate and human health. Air pollution in China and other parts of Asia poses large health risks and is an important contributor to global climate change. Almost half of Chinese homes use biomass and coal fuels for cooking and heating. China’s economic growth and infrastructure development has led to increased emissions from coal-fired power plants and an expanding fleet of motor vehicles. Black carbon (BC) from incomplete biomass and fossil fuel combustion is the most strongly light-absorbing component of particulate matter (PM) air pollution and the second most important climate-forcing human emission. PM composition and sources may also be related to its human health impact. We enrolled 280 women living in a rural area of northwestern Yunnan where biomass fuels are commonly used. We measured their blood pressure, distance from major traffic routes, and daily exposure to BC (pyrolytic biomass combustion), water-soluble organic aerosol (organic aerosol from biomass combustion), and, in a subset, hopane markers (motor vehicle emissions) in winter and summer. BC had the strongest association with systolic blood pressure (SBP) (4.3 mmHg; P < 0.001), followed by PM mass and water-soluble organic mass. The effect of BC on SBP was almost three times greater in women living near the highway [6.2 mmHg; 95% confidence interval (CI), 3.6 to 8.9 vs. 2.6 mmHg; 95% CI, 0.1 to 5.2]. Our findings suggest that BC from combustion emissions is more strongly associated with blood pressure than PM mass, and that BC’s health effects may be larger among women living near a highway and with greater exposure to motor vehicle emissions.

Atmospheric lead pollution in fine particulate matter in Shanghai, China

The Pb-monitoring program was extended for 6 years from 2002 to 2007 at 17 representative urban sites (6 traffic, 5 industrial, and 6 residential sites), and 3 suburban sites to assess the lead pollution in fine particulate matter (PM2.5) after phasing out leaded gasoline in Shanghai. Compared with Pb levels reported in other places, the Pb pollution in Shanghai is still serious after phasing out leaded gasoline, which remains at high concentration range (213-176 ng/m3) in PM2.5 in winter. Significant spatial variation of Pb concentrations and strong seasonal variation of higher Pb concentration in winter than that in summer were detected. The size distribution of Pb in particulate matter has a unimodal mode that peaks at approximately 0.154-1.59 microm particle diameter, indicating that Pb is mainly concentrated in fine fraction. Lead in the fine fraction is enriched by a factor of 10(3)-10(4) relative to Pb abundance in crust. Eight categories of Pb pollution sources were identified in the PM2.5 in the winter of 2007 in Shanghai. The important emission sources among them are vehicle exhaust derived from combustion of unleaded gasoline, metallurgic industry emission, and coal combustion emission.

Oxidative potential and inflammatory impacts of source apportioned ambient air pollution in Beijing

Air pollution exposure is associated with a range of adverse health impacts. Knowledge of the chemical components and sources of air pollution most responsible for these health effects could lead to an improved understanding of the mechanisms of such effects and more targeted risk reduction strategies. We measured daily ambient fine particulate matter (<2.5 μm in aerodynamic diameter; PM2.5) for 2 months in peri-urban and central Beijing, and assessed the contribution of its chemical components to the oxidative potential of ambient air pollution using the dithiothreitol (DTT) assay. The composition data were applied to a multivariate source apportionment model to determine the PM contributions of six sources or factors: a zinc factor, an aluminum factor, a lead point factor, a secondary source (e.g., SO4(2-), NO3(2-)), an iron source, and a soil dust source. Finally, we assessed the relationship between reactive oxygen species (ROS) activity-related PM sources and inflammatory responses in human bronchial epithelial cells. In peri-urban Beijing, the soil dust source accounted for the largest fraction (47%) of measured ROS variability. In central Beijing, a secondary source explained the greatest fraction (29%) of measured ROS variability. The ROS activities of PM collected in central Beijing were exponentially associated with in vivo inflammatory responses in epithelial cells (R2=0.65-0.89). We also observed a high correlation between three ROS-related PM sources (a lead point factor, a zinc factor, and a secondary source) and expression of an inflammatory marker (r=0.45-0.80). Our results suggest large differences in the contribution of different PM sources to ROS variability at the central versus peri-urban study sites in Beijing and that secondary sources may play an important role in PM2.5-related oxidative potential and inflammatory health impacts.

Relative impact of emissions controls and meteorology on air pollution mitigation associated with the Asia-Pacific Economic Cooperation (APEC) conference in Beijing, China

The Beijing government and its surrounding provinces implemented a series of measures to ensure haze-free skies during the 22(nd) Asia-Pacific Economic Cooperation (APEC) conference (November 10(th)-11(th), 2014). These measures included restrictions on traffic, construction, and industrial activity. Twelve hour measurements of the concentration and composition of ambient fine particulate matter (PM2.5) were performed for 5 consecutive months near the APEC conference site before (September 11(th)-November 2(nd), 2014), during (November 3(rd)-12(th), 2014) and after (November 13(th), 2014-January 31(st), 2015). The measurements are used in a positive matrix factorization model to determine the contributions from seven sources of PM2.5: secondary aerosols, traffic exhaust, industrial emission, road dust, soil dust, biomass burning and residual oil combustion. The source apportionment results are integrated with backward trajectory analysis using Weather Research and Forecast (WRF) meteorological simulations, which determine the relative influence of new regulation and meteorology upon improved air quality during the APEC conference. Data show that controls are very effective, but meteorology must be taken into account to determine the actual influence of the controls on pollution reduction. The industry source control is the most effective for reducing concentrations, followed by secondary aerosol and biomass controls, while the least effective control is for the residual oil combustion source. The largest reductions in concentrations occur when air mass transport is from the west-northwest (Ulanqab). Secondary aerosol and traffic exhaust reductions are most significant for air mass transport from the north-northwest (Xilingele League) origin, and least significant for northeast transport (Chifeng via Tangshan conditions). The largest reductions of soil dust, biomass burning, and industrial source are distinctly seen for Ulanqab conditions and least distinct for Xilingele League.

Size Distribution and Sources of Trace Metals in Ultrafine/Fine/Coarse Airborne Particles in the Atmosphere of Shanghai

Airborne particulate matter (PM) samples in 13 different size-fractions from 0.0283 to 9.92 μm were collected in winter of 2007 at three sites in Shanghai, China. The PM exhibited a bimodal distribution with a major mode in the fine particle size range (Dp = 0.2–1 μm) and a minor mode in the coarse range (Dp = 1–10 μm), suggesting that fine particle pollution is dominant in the Shanghai atmosphere. Trace metals in PM exhibited the following distribution patterns: (1) unimodal distribution in the fine fraction (Pb, Cd, Se, Sn, Bi, and Zn), (2) unimodal distribution in the coarse fraction (Mg, Al, Fe, Ca, Ba, Sr, Ge, Zr, U, and rare earth elements), (3) bimodal distribution, with one mode in the fine fraction and one in the coarse fraction (Cu, Mn, K, Ga, V, Rb, and Cs), and (4) multimodal distribution (Na, Ti, Cr, Co, As, Ni, Mo, Ag, W, Pt, Au, S, and Cl) throughout the entire aerosol size spectrum. In addition to these size distributions, Aitken modes due to local origins were also evident for Se, Sn, Cu, V, Ti, Cr, Co, As, Ag, Mo, and Pt, whose respective mass in the ultrafine particles (<0.1 μm) was 10, 23, 13, 19, 23, 14, 67, 32, 79, 40, and 21%, with submicron mass median aerodynamic diameters (MMADs) in PM0.02-9.92 (except Pt). In particular, the MMADs for Co and Ag were <0.1 μm, which increase potential health issues. The measured distributions are believed to result from a combination of processes including local anthropogenic and natural sources, such as traffic, coal combustion, and the steel industry.

Seasonal variation in outdoor, indoor, and personal air pollution exposures of women using wood stoves in the Tibetan Plateau: Baseline assessment for an energy intervention study.

Cooking and heating with coal and biomass is the main source of household air pollution in China and a leading contributor to disease burden. As part of a baseline assessment for a household energy intervention program, we enrolled 205 adult women cooking with biomass fuels in Sichuan, China and measured their 48-h personal exposure to fine particulate matter (PM2.5) and carbon monoxide (CO) in winter and summer. We also measured the indoor 48-h PM2.5 concentrations in their homes and conducted outdoor PM2.5 measurements during 101 (74) days in summer (winter). Indoor concentrations of CO and nitrogen oxides (NO, NO2) were measured over 48-h in a subset of ~80 homes. Womens geometric mean 48-h exposure to PM2.5 was 80μg/m(3) (95% CI: 74, 87) in summer and twice as high in winter (169μg/m(3) (95% CI: 150, 190), with similar seasonal trends for indoor PM2.5 concentrations (winter: 252μg/m(3); 95% CI: 215, 295; summer: 101μg/m(3); 95% CI: 91, 112). We found a moderately strong relationship between indoor PM2.5 and CO (r=0.60, 95% CI: 0.46, 0.72), and a weak correlation between personal PM2.5 and CO (r=0.41, 95% CI: -0.02, 0.71). NO2/NO ratios were higher in summer (range: 0.01 to 0.68) than in winter (range: 0 to 0.11), suggesting outdoor formation of NO2 via reaction of NO with ozone is a more important source of NO2 than biomass combustion indoors. The predictors of womens personal exposure to PM2.5 differed by season. In winter, our results show that primary heating with a low-polluting fuel (i.e., electric stove or wood-charcoal) and more frequent kitchen ventilation could reduce personal PM2.5 exposures. In summer, primary use of a gaseous fuel or electricity for cooking and reducing exposure to outdoor PM2.5 would likely have the greatest impacts on personal PM2.5 exposure.

Gas-to-particle conversion of atmospheric ammonia and sampling artifacts of ammonium in spring of Beijing

PM2.5 and gaseous pollutants (SO2, HNO2, HNO3, HCl, and NH3) were simultaneously collected by Partisol® Model 2300 Sequential Speciation Sampler with denuder-filter pack system in the spring of 2013 in Beijing. Water-soluble inorganic ions and gaseous pollutants were measured by Ion Chromatography. Results showed that the concentrations of NH3, NH4+ and PM2.5 had similar diurnal variation trends and their concentrations were higher at night than in daytime. The results of gas-to-particle conversion revealed that [NH3]:[NH4+] ratio was usually higher than 1; however, it was less than 1 and the concentration of NH4+ increased significantly during the haze episode, indicating that NH3 played an important role in the formation of fine particle. Research on the sampling artifacts suggested that the volatilization loss of NH4+ was prevalent in the traditional single filter-based sampling. The excess loss of HNO3 and HCl resulted from ammonium-poor aerosols and semivolatile inorganic species had severe losses in the clean day, whereas the mass of NH4+ was usually overestimated during the single filter-based sampling due to the positive artifacts. Correlation analysis was used to evaluate the influence of meteorological conditions on the volatilization loss of NH4+. It was found that the average relative humidity and temperature had great effects on the loss of NH4+. The loss of NH4+ was significantly under high temperature and low humidity, and tended to increase with the increasing of absorption of gaseous pollutants by denuder. The total mass of volatile loss of NH4+, NO3− and Cl− could not be ignored and its maximum value was 12.17 μg m−3. Therefore it is important to compensate sampling artifacts for semivolatile inorganic species.

Household Air Pollution and Childrenʼs Blood Pressure

To the Editor:Childhood blood pressure (BP) is an important predictor of hypertension and cardiovascular risk later in life1; risk factors for elevated BP in children remain mostly unknown. Ambient air pollution is associated with impaired vascular health, oxidative stress, and systemic inflammation

The oxidative potential of PM2.5 exposures from indoor and outdoor sources in rural China.

BACKGROUND Airborne particulate matter (PM) is a widespread environmental exposure and leading health risk factor. The health effects of PM may be mediated by its oxidative potential; however, the combustion and non-combustion sources and components of PM responsible for its oxidative potential are poorly understood, particularly in low- and middle-income rural settings where coal and biomass burning for cooking and heating contribute to PM exposure. METHODS We measured 24-h personal exposures to fine particulate matter (PM2.5) of 20 rural women in northern (Inner Mongolia) and southern (Sichuan) Chinese provinces who used solid fuels (i.e., coal, biomass). PM2.5 exposures were characterized for mass, black carbon, water-soluble organic carbon, major water-soluble ions, and 47 elements. The oxidative potential of PM2.5 exposures was measured using acellular (dithiothreitol-based) and cellular (macrophage-based) assays. We performed factor and correlation analyses using the chemical components of PM2.5 to identify sources of exposure to PM2.5 and their chemical markers. Associations between oxidative potential and chemical markers for major sources of PM2.5 exposure were assessed using linear regression models. RESULTS Womens geometric mean PM2.5 exposures were 249μgm(-3) (range: 53.9-767) and 83.9μgm(-3) (range: 73.1-95.5) in Inner Mongolia and Sichuan, respectively. Dust, biomass combustion, and coal combustion were identified as the major sources of exposure to PM2.5. Markers for dust (iron, aluminum) were significantly associated with intrinsic oxidative potential [e.g., one interquartile range increase in iron (ppm) was associated with an 85.5% (95% CI: 21.5, 149) increase in cellular oxidative potential (μgZymosanmg(-1))], whereas markers for coal (arsenic, non-sulfate sulfur) and biomass (black carbon, cadmium) combustion were not associated with oxidative potential. CONCLUSIONS Dust was largely responsible for the intrinsic oxidative potential of PM2.5 exposures of rural Chinese women, whereas biomass and coal combustion were not significantly associated with intrinsic oxidative potential.