Reconstructed Light Extinction Coefficients Using Chemical Compositions of PM2.5 in Winter in Urban Guangzhou, China

The objective of this study was to reconstruct light extinction coefficients (b(ext)) according to chemical composition components of particulate matter up to 2.5 mu m in size (PM2.5). PM2.5 samples were collected at the monitoring station of the South China of institute of Environmental Science (SCIES, Guangzhou, China) during January 2010, and the online absorbing and scattering coefficients were obtained using an aethalometer and a nephelometer. The measured values of light absorption coefficient by particle (b(ap)) and light scattering coefficient by particle (b(sp)) significantly correlated (R-2 &gt; 0.95) with values of b(ap) and b(sp) that were reconstructed using the Interagency Monitoring of Protected Visual Environments (IMPROVE) formula when RH was &lt;70%. The measured b(ext) had a good correlation (R-2 &gt; 0.83) with the calculated bext under ambient RH conditions. The result of source apportionment of bext showed that ammonium sulfate [(NH4)(2)SO4] was the largest contributor (35.0%) to b(ext), followed by ammonium nitrate (NH4NO3, 22.9%), organic matter (16.1%), elemental carbon (11.8%), sea salt (4.7%), and nitrogen dioxide (NO2, 9.6%). To improve visibility in Guangzhou, the effective control of secondary particles like sulfates, nitrates, and ammonia should be given more attention in urban environmental management.</p

Synthesis of SrFexTi1-xO3-delta nanocubes with tunable oxygen vacancies for selective and efficient photocatalytic NO oxidation

Oxygen vacancies of metal oxides play critical roles in tunning activity and selectivity for many photocatalysis mediated reactions, yet the mechanism of NO oxidation on defect enriched photocatalyst surface is seldomly discussed. Herein, we provide detailed insight into the relationship between oxygen vacancy manipulation by extrinsic Fe3+ substitution in SrTiO3 host lattice and the photocatalytic performance of NO abatement. In particular, the hydrothermal synthesized SrFexTi1-xO3-δ nanocubes (denoted as SFTO-hyd sample) rather than the impregnated-post annealing sample, enabled oxygen vacancy formation, and promoted O2 adsorption and superoxide anion radicals (O2−) formation. The SFTO-hyd (x = 5%) sample showed remarkably higher NO removal activity and selectivity under Xe lamp (λ > 420 nm), in comparison with the pristine SrTiO3, P25 and impregnation-doped SFTO sample, underlining the important roles played by coexisted Fe3+ sites and oxygen vacancies. The in situ diffuse reflectance IR spectroscopy (DRIFTS) mechanically revealed that SrTiO3 provided Lewis acidic sites for NO dark adsorption and photoreaction with nitrates as final products; the substitutional Fe3+ sites provided more active sites for NO adsorption and photoreaction with enhanced number of radicals. This study deepens the understanding of photocatalytic NO abatement on defective surface, and may also provide a simple and cost effective strategy for synthesizing efficient and selective photocatalysts for environmental remediation

Numerical Simulation of Airflow Structure and Dust Emissions behind Porous Fences Used to Shelter Open Storage Piles

Porous fences can reduce dust emissions from storage piles in open storage yards, but their sheltering effect depends on the airflow structure around the pile, and the shear stress distribution on each surface. In this study, static flow fields were numerically simulated using k-epsilon standard The turbulence model; the shear stress characteristics and distribution on the windward side, flat-top surface, and leeward side of a typical prismatic material stack were analyzed. The distribution of the aerodynamic structure of each surface of the storage pile was determined according to the flow field data for fences of the porosities epsilon = 0, 0.2, 0.3, 0.4, 0.5, and 0.6. The results indicated that at low porosities (epsilon = 0, 0.2) a recirculating flow appeared in the region between the fence and the pile. The shear force acted downward the windward slope, and the maximum dust emission occurred at two-thirds the height of the windward side, rather than at the top, as in unfenced conditions. Using the porous fence simulated in this study, shear stress on the windward side and the flat-top surface first decreased, then increased with increasing porosity; the lowest porosity values were 0.2 and 0.3, and the shear stress on the prismatic leeside changed little with increasing porosity. The numerical predictions indicated that a fence with porosity between 0.2 and 0.3 is optimal.</p

Impacts of aerosol compositions on visibility impairment in Xi'an, China

Daily particle light scattering coefficient, PM2.5 mass and chemical composition were measured in Xi&#39;an from February to December 2009. Visibility was strongly affected by anthropogenic air pollution sources, resulting in an average visual range (VR) of 6.4 &plusmn; 4.5 km. The threshold PM2.5 mass concentration, corresponding to VR &lt;10 km, was &sim;88 &mu;g m&minus;3. The revised IMPROVE equation was applied to estimate chemical extinction (bext), which on average was &sim;15% lower than measured bext. PM2.5 ammonium sulfate was the largest contributor, accounting for &sim;40% of bext, followed by organic matter (&sim;24%), ammonium nitrate (&sim;23%), and elemental carbon (&sim;9%), with minor contributions from soil dust (&sim;3%), and NO2 (&sim;1%). High secondary inorganic aerosol contributions (i.e., SO42&minus; and NO3&minus;) were the main contributors for VR &lt;5 km. A Positive Matrix Factorization (PMF) solution to the Chemical Mass Balance (CMB) receptor model showed that coal combustion was the dominant factor, accounting for &sim;52% of the dry particle light scattering coefficient, followed by the engine exhaust factor (&sim;31%). Other factors included biomass burning (&sim;12%) and fugitive dust (&sim;5%).</p

The impact of biomass burning on total suspended particulate matter in the southeastern Tibetan Plateau

To investigate the impact of biomass burning (BB) emissions on total suspended particulate (TSP) in the southeastern Tibetan Plateau (TP), BB tracers (including levoglucosan, mannosan, and galactosan) were measured at Lulang (a remote site, &sim;3300 m above sea level) during the period 2015&ndash;2016. The concentrations of levoglucosan and mannosan showed large variability of more than 8-fold (range: 0.029&ndash;0.253 &mu;g m&minus;3) and 6-fold (range: 0.01&ndash;0.061 &mu;g m&minus;3), respectively. The highest seasonal average concentrations of levoglucosan (0.131 &plusmn; 0.073 &mu;g m&minus;3) and mannosan (0.028 &plusmn; 0.019 &mu;g m&minus;3) were observed during the winter season. The BB contributions to the TSP organic carbon (OC) and TSP mass were estimated with positive matrix factorization (PMF) by using BB tracers, inorganic ions, elements, OC, and EC. The BB contributions to the TSP OC and TSP mass were quite substantial in winter with 26% and 14%, respectively. The results evidenced a major contribution of BB to the aerosol OC during winter season. Major potential source distributions of BB were identified, which included the pollution bands along the Indo-Gangetic Plain, the Yarlung Tsangpo River Valley and the interior of the TP. In addition to the long-range transport of BB, the sources of anthropogenic emissions (residential BB for cooking and heating) in the TP may be an important contributor. The results facilitated understanding of the characteristics and effects of BB in the TP.</p

Methionine oxidation in albumin by fine haze particulate matter: An in vitro and in vivo study

The potential effects of inhaled fine particulate matter (PM2.5), found in haze episodes, on the oxidation of the proteins in the lungs are not well understood. We investigated the effects of PM2.5 from haze episodes on protein oxidation. PM2.5 was collected from the air pollution in Beijing (BJ), Xian (XA), Xiamen (XM) and Hong Kong (HK) during a period of intensive haze episodes. The chemical characteristics of these samples and their effects on albumin oxidation were investigated. The levels of PM2.5 in BJ and)CA were 4-6 times higher than in XM and HK. The concentrations of the polycyclic aromatic hydrocarbons (PAHs) components of the PM2.5 from BJ and XA were 10 times higher than those found in XM and HK. The haze PM2.5 increased oxidative stress. Addition of PM2.5 samples collected from haze episodes to albumin in vitro resulted in oxidation of methionine moieties; nasal instillation of PM2.5 suspensions in mice resulted in oxidation of methionine in the albumin in the bronchoalveolar lavage fluid. The methionine moieties participate in peptide chain crosslinking, and methionine oxidation in the albumin could be attributed to the PAH compounds. Our findings may be helpful in explaining the potential respiratory effects during haze episodes.</p

Winter and Summer PM2.5 Chemical Compositions in Fourteen Chinese Cities

PM2.5 in 14 of China&#39;s large cities achieves high concentrations in both winter and summer with averages &gt; 100 mu g m(-3) being common occurrences. A grand average of 115 mu g m(-3) was found for all cities, with a minimum of 27 mu g m(-3) measured at Qingdao during summer and a maximum of 356 mu g m(-3) at Xi&#39;an during winter. Both primary and secondary PM2.5 are important contributors at all of the cities and during both winter and summer. While ammonium sulfate is a large contributor during both seasons, ammonium nitrate contributions are much larger during winter. Lead levels are still high in several cities, reaching an average of 1.68 mu g m(-3) in Xi&#39;an. High correlations of lead with arsenic and sulfate concentrations indicate that much of it derives from coal combustion, rather than leaded fuels, which were phased out by calendar year 2000. Although limited fugitive dust markers were available, scaling of iron by its ratios in source profiles shows similar to 20% of PM2.5 deriving from fugitive dust in most of the cities. Multipollutant control strategies will be needed that address incomplete combustion of coal and biomass, engine exhaust, and fugitive dust, as well as sulfur dioxide, oxides of nitrogen, and ammonia gaseous precursors for ammonium sulfate and ammonium nitrate.</p

Simultaneous Measurements of Surface Ozone at Two Sites over the Southern Asia: A Comparative Study

This article presents variations of simultaneous measurements of near surface ozone (O(3)) at two sites namely Anantapur [14.62 degrees N, 77.65 degrees E], a semi arid rural location in India and Xi&#39;An [34.20 degrees N, 108.98 degrees E], a semi arid urban location in China during January-July 2009. The results showed a clear diurnal cycle of O(3) with a minimum at sunrise and a maximum at noon for both the sites. The monthly average diurnal variation shows that the maximum/minimum ozone was observed in March/July whereas in Xi&#39;An maximum/minimum ozone was observed in July/February because of different climatic zones and rainfall activity. The average diurnal variation of O(3) for different seasons (summer and winter) shows higher ozone concentration at Anantapur than at Xi&#39;An. This may be due to slower titration of NO in the evening hours at Anantapur. But in Xi&#39;An, the highest ozone levels recorded in noon hours for some days in June and July months. This is mainly due to strong emissions of NO(x), VOC and high solar radiation and this implies significant negative effects on vegetation and regional air quality around Xi&#39;An. The rate of increase of ozone is almost the same at two sites but the rate of decrease of ozone is more at Xi&#39;An than at Anantapur which is due to the higher NO(x) concentration from vehicular emission and also due to the fast titration of O(3). The maximum 54% of frequency distribution of ozone lies between 20-45 ppbv at Anantapur whereas in Xi&#39;An 34% lies in the range of 0-5 ppbv, 32% of Ozone lie between 5-20 ppbv and 24% of all O(3) lie in the range of 20-45 ppbv.</p