Variations of Particle Size Distribution, Black Carbon, and Brown Carbon during a Severe Winter Pollution Event over Xi'an, China

Real-time particulate matter (PM) size distributions, 4-hour time resolution, PM2.5, carbonaceous materials, and their optical properties were measured during a severe pollution event in Xi'an, China High PM2.5 /PM10 ratios were observed on both pollution (0.83) and non-pollution (0.73) days, emphasizing the abundance of fine particles during sampling days. The particle number (PN) first peaked with a wide size range (30-100 nm) before morning rush hours (approximately 01:00-05:00) on pollution and non-pollution days, demonstrating that PN was governed by the accumulation of freshly emitted diesel particles and characterized by distinct aerosol condensation growth. By contrast, the second peak time and size range differed between pollution and non-pollution days because of different formation mechanisms The light-absorbing coefficients of both black carbon (BC, b(abs-880nm,BC)) and brown carbon (BrC, b(abs-370nm, BrC)) were high on pollution days and decreased to approximately half of those values on non-pollution days, indicating that the degree of light absorption is reduced by rain. The diurnal variation in b(abs-880nm, BC) pollution peaked with traffic on January 1 and 2. By contrast, it remained in relatively stable and high ranges (120-160 Mm(-1)) in the second period (January 3-5) without traffic peaks, illustrating that the dominant sources changed even during the same pollution period. High values of both b(abs-370nm, BrC) and b(abs-880nm,) (BC )coincided in the afternoon and evening due to emissions from primary sources, and abundant aqueous secondary organic carbon, respectively. A highly variable mass absorption coefficient of BrC also indicated the variety of fuel combustion sources of primary BrC in Xi'an

Kraft Lignin Biodegradation by Dysgonomonas sp. WJDL-Y1, a NewAnaerobic Bacterial Strain Isolated from Sludge of a Pulp and PaperMill

Wastewater containing kraft lignin (KL) discharged from pulp and paper industries could cause serious environmental contamination. Appropriate effluent treatment is required to reduce the pollution. Investigations on anaerobic bacteria capable of degrading KL are beneficial to both lignin removal and biofuel regeneration from the effluent. In this paper, an anaerobic strain capable of degrading KL was isolated from the sludge of a pulp and paper mill and identified as Dysgonomonas sp. WJDL-Y1 by 16S rRNA. Optimum conditions for KL degradation by strain WJDL-Y1 were obtained at initial pH of 6.8, C:N ratio of 6 and temperature of 33&deg;C based on statistical analyses by Response Surface Methodology (RSM). For 1.2g/L KL solution, COD removal rate of 20.7% concomitanting with biomass increase of 17.6% were achieved after 4 days incubation under the optimum conditions. After the treatment by strain WJDL-Y1, KL was modified and degraded.</p

Characterization, mixing state, and evolution of urban single particles inXi'an (China) during wintertime haze days

A Single Particle Aerosol Mass Spectrometer (SPAMS) was deployed in the urban area of Xi&#39;an to investigate size-resolved chemical composition and mixing state of single particles during the heavy haze episode occurred from January 13 to January 27 in 2013. Nine major single particle types were resolved with ART-2a algorithm including biomass burning (BB), Potassium-Secondary (KSec), elemental and organic Carbon (ECOC), sodium-potassium-rich ECOC (NaKECOC), sodium-potassium-rich-secondary (NaKSec), EC, OC, and Dust. Daily PM2.5 mass concentration was 213&nbsp;&plusmn;&nbsp;122&nbsp;&mu;g&nbsp;m&minus;&nbsp;3. ~&nbsp;96% of the ambient particles were carbonaceous and internally mixed with secondary species such as sulfate and nitrate. The major particle types were from combustion sources, including coal burning, biomass burning, and vehicle exhaust. Mixing state analysis suggests gas-to-particle conversion was an important mechanism forming organic species during the winter haze episode. The relative abundances of the aged particle types, such as KSec and NaKSec increased with the elevated RH when RH&nbsp;&lt;&nbsp;80%. The fraction of aged particles in terms of number concentration was prominent during high levels of PM2.5 under stagnant air conditions. This study gained new knowledge on atmospheric aerosol formation and evolution in urban environment heavy winter haze condition.</p

Size-resolved airborne particulate oxalic and related secondary organicaerosol species in the urban atmosphere of Chengdu, China

Size-segregated (9-stages) airborne particles during winter in Chengdu city of China were collected on a day/night basis and determined for dicarboxylic acids (diacids), ketocarboxylic acids (ketoacids), α-dicarbonyls, inorganic ions, and water-soluble organic carbon and nitrogen (WSOC and WSON). Diacid concentration was higher in nighttime (1831 ± 607 ng m− 3) than in daytime (1532 ± 196 ng m− 3), whereas ketoacids and dicarbonyls showed little diurnal difference. Most of the organic compounds were enriched in the fine mode (< 2.1 μm) with a peak at the size range of 0.7–2.1 μm. In contrast, phthalic acid (Ph) and glyoxal (Gly) presented two equivalent peaks in the fine and coarse modes, which is at least in part due to the gas-phase oxidation of precursors and a subsequent partitioning into pre-existing particles. Liquid water content (LWC) of the fine mode particles was three times higher in nighttime than in daytime. The calculated in-situ pH (pHis) indicated that all the fine mode aerosols were acidic during the sampling period and more acidic in daytime than in nighttime. Robust correlations of the ratios of glyoxal/oxalic acid (Gly/C2) and glyoxylic acid/oxalic acid (ωC2/C2) with LWC in the samples suggest that the enhancement of LWC is favorable for oxidation of Gly and ωC2 to produce C2. Abundant K+ and Cl− in the fine mode particles and the strong correlations of K+ with WSOC, WSON and C2 indicate that secondary organic aerosols in the city are significantly affected by biomass burning emission

Chemical characteristics of PM2.5 during dust storms and air pollution events in Chengdu, China

Daily fine particulate (PM2.5) samples were collected in Chengdu from April 2009 to February 2010 to investigate their chemical profiles during dust storms (DSs) and several types of pollution events, including haze (HDs), biomass burning (BBs), and fireworks displays (FDs). The highest PM2.5 mass concentrations were found during DSs (283.3 mu g/m(3)), followed by FDs (212.7 mu g/m(3)), HDs (187.3 mu g/m(3)), and BBs (130.1 mu g/m(3)). The concentrations of most elements were elevated during DSs and pollution events, except for BBs. Secondary inorganic ions (NO3-, SO42-, and NH4+) were enriched during HDs, while PM2.5 from BBs showed high K+ but low SO42-. FDs caused increases in K+ and enrichment in SO42-. Ca2+ was abundant in DS samples. Ion-balance calculations indicated that PM2.5 from HDs and FDs was more acidic than on normal days, but DS and BB particles were alkaline. The highest organic carbon (OC) concentration was 26.1 mu g/m(3) during FDs, followed by BBs (23.6 mu g/m(3)), HDs (19.6 mu g/m(3)), and DSs (18.8 mu g/m(3)). In contrast, elemental carbon. (EC) concentration was more abundant during HDs (10.6 mu g/m(3)) and FDs (9.5 mu g/m(3)) than during BBs (6.2 mu g/m(3)) and DSs (6.0 mu g/m(3)). The highest OC/EC ratios were obtained during BBs, with the lowest during HDs. SO42-/K+ and TCA/SO42- ratios proved to be effective indicators for differentiating pollution events. Mass balance showed that organic matter, SO42-, and NO3- were the dominant chemical components during pollution events, while soil dust was dominant during DSs.</p

Characterization of particulate-bound polycyclic aromatic compounds (PACs) and their oxidations in heavy polluted atmosphere: A case study in urban Beijing, China during haze events

Characterizations on polycyclic aromatic compounds (PACs) during frequent haze periods have been conducted in an urban site of Beijing, China. Particulate polycyclic aromatic hydrocarbons (PAHs) and oxygenated-PAHs (OPAHs) and other carbonaceous matters were quantified. The average PM2.5 during haze events (256.3 +/- 103.7 mu g/m(3)) were one magnitude over than that of clear periods (CRs, 24.7 +/- 27.7 mu g/m(3)). The average total quantified PAHs (Sigma PAHs) and OPAHs (Sigma OPAHs) during haze events were 423.9 +/- 178.4 ng/m(3) and 581.4 +/- 299.8 ng/m(3), respectively, which were approximately 10 times higher than those of 40.3 +/- 68.2 ng/m(3) and 54.4 +/- 82.4 ng/m(3) in clear days. Four-rings PAHs had the highest compositions. 1,8-Naphthalic anhydride (1,8-NA) is the most abundant OPAHs, accounted for 49.8% of Sigma OPAHs, followed by 9,10-anthraquinone (9,10-AQ) (13.8%) and benzo(a)anthracene-7,12-dione (BaAQ) (8.31%). In haze events, the contents of 5- to 7-rings PAHs decreased by 2.32% compared with those of clear days, while lower molecular weight fractions of 3- and 4-rings PAHs increased. The relationships between PAHs, OPAHs and relative humidity (RH) were found to be exponential. High oxygenation rate (R-0) ratios of OPAH/PAH represents higher rates in secondary formation or degradation and gas-particle conversion for each PAH or OPAH during the wintertime. Significant positive correlation between BeP and OPAHs (r = 0.97), combined with the results of photochemical aging and negatively correlationwith O-3, suggest that secondary atmospheric reactions of PAHs played an important role in the burden of OPAHs

Mixing State of Black Carbon Aerosol in a Heavily Polluted Urban Area of China: Implications for Light Absorption Enhancement

Black carbon (BC) is important for climate forcing, and its effects on the Earth&#39;s radiative balance remain a major uncertainty in climate models. In this study, we investigated the mixing state of refractory black carbon (rBC) and aerosol optical properties in a polluted atmosphere at Xi&#39;an, western China. The average rBC mass concentration was 9.9 mu g m (3) during polluted periods, 7.6 times higher than that in clean periods. About 48.6% of the rBC was internally-mixed or coated with nonrefractory materials during polluted periods; this was 27% higher than in clean periods. Correlation analysis between the number fraction of thickly-coated rBC particles (f(BC)) and the major particulate species indicate that organics may be the primary contributor to rBC coatings during polluted periods. The average mass absorption cross section of rBC (MAC(BC)) particles at lambda = 870 nm was 7.6 +/- 0.02 m(2) g(-1) for the entire campaign. The MAC(BC) showed a positive correlation with f(BC), and the enhancement of MAC(BC) due to internal mixing was 1.8 times. These observations suggest that an enhancement of BC absorption by a factor of similar to 2 could be appropriate for climate models associated with high PM2.5 levels.</p

Optical characteristics and source apportionment of brown carbon in winterPM2.5 over Yulin in Northern China

In this study, daily PM2.5 samples were collected at an urban site in Yulin of Northern China during a winter season. Eight carbon fractions, 13 kinds of polycyclic aromatic hydrocarbons (PAHs), and nine water-soluble ions in PM2.5 were measured. The light-absorption characteristics of brown carbon (BrC) both in water and in methanol extracts were evaluated and quantified. The total quantified PAHs exhibited high concentrations (228.4 &plusmn; 52.6 ng m&minus;3), contributing 0.2% of the PM2.5 mass. High indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene + benzo[ghi]-perylene) ratio but low NO3&minus;/SO42&minus; ratio revealed the important contribution of coal combustion to PM2.5. The absorption coefficient (babs) for methanol extracts measured at 365 nm averaged 27.5 &plusmn; 12.0 Mm&minus;1. Light absorption by methanol extracts exhibited strong wavelength dependence, with an average absorption &Aring;ngstr&ouml;m exponent of 5.2 in the 330&ndash;400 nm range. The mass absorption cross section (for methanol extracts averaged 1.4 &plusmn; 0.4 m2 g&minus;1 by normalizing babs measured at 365 nm to organic carbon mass. A relatively strong positive relationship between babs, methanol and benzo[a]pyrene as well as with six carbon fractions indicated the important contribution of coal burning to BrC. Source apportionment based on the positive matrix factorization receptor model and multiple linear regression showed that residential coal combustion accounted for 37.4% of babs365,methanol. The estimated relative radiative forcing by methanol-soluble organic carbon relative to elemental carbon was 36.9% at 300&ndash;400 nm

Primary PM2.5 and trace gas emissions from residential coal combustion: assessing semi-coke briquette for emission reduction in the Beijing-Tianjin-Hebei region, China

In response to severe haze pollution, the Chinese State Council set PM2.5 improvement targets for the Beijing-Tianjin-Hebei (BTH) region in 2013. To achieve the targets for the residential sector, semi-coke briquettes are being considered as a replacement for traditional raw coals with the help of financial subsidy, but information on the emission from them and the impacts on the air quality is limited. Laboratory experiments were conducted to determine emission factors (EFs) for a typical semi-coke briquette, its parent material (bituminous raw-coal-chunk) and three types of traditional coals (bituminous raw-coal-chunk, anthracite raw-coal-chunk and anthracite coal-briquette) extensively used in BTH. Compared with the parent material, significant lower EFs of primary PM2.5, organic carbon (OC), element carbon (EC), the sum of 16 polycyclic aromatic hydrocarbon components (PAHs), SO42−, NO3−, hazardous trace elements (HTEs) and NOx were found in semi-coke briquette. A scenario for the BTH region in 2015 in which raw coals were replaced with the semi-coke briquette showed that amounts of pollutants emitted from residential coal combustion could decrease by 91.6% for primary PM2.5, 94.0% for OC, 99.6% for EC, 99.9% for PAHs, 94.2% for NO3−, 45.6% for HTEs, 70.9% for NOx and 22.3% for SO2. However, SO42− loadings evidently would increase if raw coals were replaced with either semi-coke briquette or anthracite coal-briquette. Geographic distributions of modeled reductions were developed to identify emission-reducing hot-spots and aid in the development of clean energy policies. Replacement of traditional raw coals with the semi-coke briquette apparently could lead to significant environmental improvements in BTH and other regions in China

Chemical composition of PM2.5 at an urban site of Chengdu in southwestern China

PM2.5 aerosols were sampled in urban Chengdu from April 2009 to January 2010, and their chemical compositions were characterized in detail for elements, water soluble inorganic ions, and carbonaceous matter. The annual average of PM2.5 was 165 mu g m(-3), which is generally higher than measurements in other Chinese cities, suggesting serious particulate pollution issues in the city. Water soluble ions contributed 43.5% to the annual total PM2.5 mass, carbonaceous aerosols including elemental carbon and organic carbon contributed 32.0%, and trace elements contributed 13.8%. Distinct daily and seasonal variations were observed in the mass concentrations of PM2.5 and its components, reflecting the seasonal variations of different anthropogenic and natural sources. Weakly acidic to neutral particles were found for PM2.5. Major sources of PM2.5 identified from source apportionment analysis included coal combustion, traffic exhaust, biomass burning, soil dust, and construction dust emissions. The low nitrate: sulfate ratio suggested that stationary emissions were more important than vehicle emissions. The reconstructed masses of ammonium sulfate, ammonium nitrate, particulate carbonaceous matter, and fine soil accounted for 79% of the total measured PM2.5 mass; they also accounted for 92% of the total measured particle scattering.</p