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

Regression Analyses between Recent Air Quality and Visibility Changes in Megacities at Four Haze Regions in China

The Chinese government has put forward a series of aggressive control measures to tackle environmental problems, such as poor visibility, since the first year of its 11th five-year plan (2006-2010). Recently recorded visibility, air quality and meteorological data in four major megacities (Beijing, Shanghai, Guangzhou and Chengdu) in different haze regions (and climatic zones) of China were analyzed with the aim of evaluating the extent to which the control actions have affected these measures. The ambient concentrations of three major air pollutants (SO2, NO2 and PM10) in these cities all decreased in the years 2005-2009. However, improved visibility was observed only in Beijing and Guangzhou; it remained steady in Shanghai, and showed a decreasing trend in Chengdu. The results highlight the fact that the correlation between air quality and visibility is complex. Optimal empirical regression models were developed, based on measured air quality and meteorological parameter data, to better isolate possible causal correlations between visibility and air quality, as well as meteorological conditions. Our results show that the improvement in visibility in both Beijing and Guangzhou was mainly due to the reduced PM10 concentration. In Guangzhou, improved atmospheric visibility was also helped by a reduction in SO2 concentration in winter. In contrast, lower wind speed, together with possible changes in fine particle concentration and composition, could explain why no improvement in visibility trend was found in Shanghai or Chengdu.</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

Hazardous airborne carbonyls emissions in industrial workplaces in China

A pilot hazardous airborne carbonyls study was carried out in Hong Kong and the Mainland of China. Workplace air samples in 14 factories of various types of manufacturing and industrial operations were collected and analyzed for a panel of 21 carbonyl compounds. The factories can be classified into five general categories, including food processing, electroplating, textile dyeing, chemical manufacturer, and petroleum refinery. Formaldehyde was invariably the most abundant carbonyl compound among all the workplace air samples, accounting for 22.0-44.0% of the total measured amount of carbonyls on a molar basis. Acetone was also found to be an abundant carbonyl in workplace settings; among the selected industrial sectors, chemical manufacturers&#39; workplaces had the highest percentage (an average of 42.6%) of acetone in the total amount of carbonyls measured in air. Benzaldehyde accounted for an average of 20.5% of the total amount of detected carbonyls in electroplating factories, but its contribution was minor in other industrial workplaces. Long-chain aliphatic carbonyls (C-6-C-10) accounted for a large portion (37.2%) of the total carbonyls in food-processing factories. Glyoxal and methylglyoxal existed at variable levels in the selected workplaces, ranging from 0.2% to 5.5%. The mixing ratio of formaldehyde ranged from 8.6 to 101.2 ppbv in the sampled workplaces. The observed amount of formaldehyde in two paint and wax manufacturers and food-processing factories exceeded the World Health Organization (WHO) air quality guideline of 81.8 ppbv. Carcinogenic risks of chronic exposure to formaldehyde and acetaldehyde by the workers were evaluated. The lifetime cancer hazard risks associated with formaldehyde exposure to male and female workers ranged from 2.01x10(-5) to 2.37x10(-4) and 2.68x10(-5) to 3.16x10(-4), respectively. Such elevated risk values suggest that the negative health impact of formaldehyde exposure represents a valid concern, and proper actions should be taken to protect workers from such risks. Implications: Many carbonyl species (e.g., formaldehyde, acetaldehyde, and acrolein) are air toxins and they pose public health risks. The scope of this investigation covers 21 types of carbonyls based on samples collected from 14 different workplaces. Findings of the study will not only provide a comprehensive assessment of indoor air quality with regard to workers&#39; healthy and safety, but also establish a theoretical foundation for future formulation of intervention strategies to reduce occupational carbonyl exposures. No similar study has been carried out either in Hong Kong or the Mainland of China.</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

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

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