Characteristics of PM2.5 emitted from different cooking activities in China

PM2.5 samples were collected from five different cooking activities, namely, meat roasting, cafeteria frying, fish roasting, snack-street boiling, and cafeteria boiling in Ya&rsquo;an, China. Their chemical compositions were investigated. The PM2.5 concentrations in the cooking samples were 2.5&ndash;9.6 times higher than those in the corresponding backgrounds. Meat roasting produced the highest amount of PM2.5. In general, charbroilings emitted more PM2.5 than the other cooking activities because of the characteristics of cooking method and fuel type. High organic carbon (OC) contents (N53% of PM2.5) and OC/EC ratios (N54) in meat roasting and cafeteria frying samples suggest that oils and high-fat raw materials significantly affect the PM2.5 and OC emissions. However, the cooking activity was proved to be a minor source for elemental carbon (EC) with its low contents in all of the samples. High ion compositions in PM2.5 and WSOC/OC ratios in the snack-street boiling and cafeteria boiling samples represent that water-based cooking emitted more water-soluble species. Considering that high OC/EC ratios were measured in the oil-based cooking samples and most secondary organic aerosols (SOAs) are water soluble, it is more reasonable to estimate SOA with WSOC/OC ratio in populated urban areas. We found that the formation of SOA is significant when the WSOC/OC ratio is larger than 0.40. Principal component analysis (PCA) with the quantified metals identified four contributors to the samples, including coal combustion and non-licensed business activities, soil dust, charcoal burning, and stainless steel utensils, and explained 73% of the total variance. The high emissions of PM2.5 and toxic components from the cooking activities suggest that food safety control and environmental standard establishment should be strengthened in small and medium-sized cities in China.</p

Molecular Distribution and Stable Carbon Isotopic Composition of Dicarboxylic Acids, Ketocarboxylic Acids, and alpha-Dicarbonyls in Size-Resolved Atmospheric Particles From Xi'an City, China

Size-resolved airborne particles (9-stages) in urban Xi&#39;an, China, during summer and winter were measured for molecular distributions and stable carbon isotopic compositions of dicarboxylic acids, ketocarboxylic acids, and alpha-dicarbonyls. To our best knowledge, we report for the first time the size-resolved differences in stable carbon isotopic compositions of diacids and related compounds in continental organic aerosols. High ambient concentrations of terephthalic (tPh, 379 +/- 200 ng m(-3)) and glyoxylic acids (omega C-2, 235 +/- 134 ng m(-3)) in Xi&#39;an aerosols during winter compared to those in other Chinese cities suggest significant emissions from plastic waste burning and coal combustions. Most of the target compounds are enriched in the fine mode (&lt;2.1 mu m) in both seasons peaking at 0.7-2.1 mu m. However, summertime concentrations of malonic (C-3), succinic (C-4), azelaic (C-9), phthalic (Ph), pyruvic (Pyr), 4-oxobutanoic (omega C-4), and 9-oxononanoic (omega C-9) acids, and glyoxal (Gly) in the coarse mode (&gt;2.1 mu m) are comparable to and even higher than those in the fine mode (&lt;2.1 mu m). Stable carbon isotopic compositions of the major organics are higher in winter than in summer, except oxalic acid (C-2), omega C-4, and Ph. delta C-13 of C-2 showed a clear difference in sizes during summer, with higher values in fine mode (ranging from -22.8 parts per thousand to -21.9 parts per thousand) and lower values in coarse mode (-27.1 parts per thousand to -23.6 parts per thousand). The lower delta C-13 of C-2 in coarse particles indicate that coarse mode of the compound originates from evaporation from fine mode and subsequent condensation/adsorption onto pre-existing coarse particles. Positive linear correlations of C-2, sulfate and omega C-2 and their delta C-13 values suggest that omega C-2 is a key intermediate, which is formed in aqueous-phase via photooxidation of precursors (e.g., Gly and Pyr), followed by a further oxidation to produce C-2.</p

Chemical characteristics of haze particles in Xi'an during Chinese Spring Festival: Impact of fireworks burning

Fireworks burning releases massive fine particles and gaseous pollutants, significantly deteriorating air quality during Chinese Lunar New Year (LNY) period. To investigate the impact of the fireworks burning on the atmospheric aerosol chemistry, 1-hr time resolution of PM2.5 samples in Xi'an during the winter of 2016 including the LNY were collected and detected for inorganic ions, acidity and liquid water content (LWC) of the fine aerosols. PM2.5 during the LNY was 167 ± 87 μg/m3, two times higher than the China National Ambient Air Quality Standard (75 μg/m3). K+ (28 wt.% of the total ion mass) was the most abundant ion in the LNY period, followed by SO42 − (25 wt.%) and Cl− (18 wt.%). In contrast, NO3− (34 wt.%) was the most abundant species in the haze periods (hourly PM2.5 > 75 μg/m3), followed by SO42 − (29.2 wt.%) and NH4+ (16.3 wt.%), while SO42 - (35 wt.%) was the most abundant species in the clean periods (hourly PM2.5 < 75 μg/m3), followed by NO3− (23.1 wt.%) and NH4+ (11 wt.%). Being different from the acidic nature in the non-LNY periods, aerosol in the LNY period presented an alkaline nature with a pH value of 7.8 ± 1.3. LWC during the LNY period showed a robust linear correlation with K2SO4 and KCl, suggesting that aerosol hygroscopicity was dominated by inorganic salts derived from fireworks burning. Analysis of correlations between the ratios of NO3−/SO42 − and NH4+/SO42 − indicated that heterogeneous reaction of HNO3 with NH3 was an important formation pathway of particulate nitrate and ammonium during the LNY period

Size Differentiation of Individual Atmospheric Aerosol during Winter in Xi'an, China

Airborne particulate matter (including TSP, PM10, PM2.5, and PM1) were collected at an urban site in Xi&#39;an during winter 2010. Individual particles were analyzed using scanning electron microscopy and energy dispersive X-ray spectrometer (SEM-EDX). The morphologies, size distributions, and relative abundance of aerosol particles in each size were summarized. The monomodal particle size distribution was found in all the samples under different weather conditions, with the peaks located at less than 1.0 mu m. The majority of particles were composed of soot, mineral dust, and tar balls, with minor fly ash particles. Soot aggregates were the predominant species (in numbers), ranging from 56.6% in TSP on a sunny day to 86.3% in PM1 on a cloudy day, with an average of 73.2% in all the samples. The particle mass concentration and chemical composition, including water-soluble inorganic ions, elemental compositions, organic carbon (OC) and elemental carbon (EC) contents of 24-hr integrated PM2.5, were also subject to chemical bulk analysis. Soot was predominantly observed in the PM2.5 samples (from 74.7% to 82.7% in numbers), whereas EC accounted for only a small amount (&lt; 8%) of the PM2.5 mass. Corresponding to the mass concentrations of geological materials (29.2%, 44.5%, and 37.3% on sunny, cloudy, and hazy days), the number concentrations of mineral dust and fly ash particles on the sunny, cloudy, and hazy days were 14.6%, 7.1%, and 7.7%, respectively.</p

N-Alkanes and polycyclic aromatic hydrocarbons in total suspended particulates from the southeastern Tibetan Plateau: Concentrations, seasonal variations, and sources

Sixty-two suspended particle (TSP) samples were collected from Lulang on the southeastern Tibetan Plateau from July 2008 and July 2009 to investigate the concentrations, seasonal variations, and sources of n-alkanes and polycyclic aromatic hydrocarbons (PAHs). Samples were analyzed using thermal-deposition gas chromatography mass spectrometry. The concentrations of particulate total n-alkanes ranged from 0.10 to 21.83ngm-3, with an annual mean of 1.25ngm-3; the PAHs ranged from 0.06 to 2.53, with a mean of 0.59 ngm-3. Up to 70% of PAHs were 5- and 6-ring compounds. The n-alkanes and PAHs both showed higher concentrations in winter and lower concentrations in summer. Analyses of diagnostic ratios indicate that 6.4% to 58.9% (mean 24.9%) of the n-alkanes were from plant waxes. Source characterization studies, i.e. diagnostic ratio and positive factor matrix analysis, suggest that the PAHs were from biomass burning as well as from fossil fuel combustion. Backward trajectory analysis suggests that the biomass mass burning pollutants could be from South Asia and western China via long distance transport. The study contributes to a more comprehensive understanding of the concentrations, seasonal variations, and sources of n-alkanes and PAHs in a remote background area in Tibetan Plateau.</p

Characterization of atmospheric organic and elemental carbon of PM2.5 in a typical semi-arid area of northeastern China

In the spring of 2006, daily particulate matter (PM2.5) aerosol samples were collected in Tongyu, a semi-arid area in northeastern China. The concentrations of organic carbon (OC) and elemental carbon (EC) were determined with a thermal/optical carbon analyzer in the filter samples. The average concentrations of OC and EC in PM2.5 were 14.1 &plusmn; 8.7 and 2.0 &plusmn; 1.3 &mu;g/m3, respectively. A good correlation between OC and EC was observed during the spring season, suggesting that they might be derived from similar sources. The correlation between OC and K+ was high (R = 0.74), and the K+/OC ratio, as determined from their linear regression slope, reached 2.57. The good correlation and high K+/OC ratio indicated that biomass-burning was probably one of the major sources of OC in this region. The concentrations of estimated secondary organic carbon (SOC) in PM2.5 in Tongyu ranged from below the detection limit to 26.1 &mu;g/m3 (mean, 5.9 &mu;g/m3). The percentages of SOC in OC and in PM2.5 mass were 42.0% and 2.1%, respectively. The SOC concentrations during dust storm (DS) periods were higher than those during non-dust storm (NDS) ones, suggesting that chemical reaction processes involving gas-particle conversion occurred during the long-distance transport of aerosol particles.</p

Chemical composition and size distribution of wintertime aerosols in the atmosphere of Mt. Hua in central China

TSP, PM(10) and size-segregated aerosols were collected at the summit (2060 m, a.s.l.) of Mt. Hua in central China during the winter of 2009, and determined for organic (OC) and elemental carbon (EC), pH of water-extracts and inorganic ions. OC in TSP and PM(10) are 6.9 +/- 2.9 and 5.9 +/- 2.5 mu g m(-3), while EC in TSP and PM(10) are 0.9 +/- 0.6 and 0.9 +/- 0.5 mu g m(-3), respectively. SO(4)(2-), NO(3)(-), NH(4)(+) and Ca(2)(+) are major ions in PM(10) with concentrations of 5.8 +/- 3.7, 2.7 +/- 1.6, 1.6 +/- 0.9 and 1.5 +/- 0.7 mu g m(-3), respectively. OC/EC ratios (8.2 +/- 3.1 in TSP and 6.6 +/- 1.8 in PM(10)) at the mountaintop are 2-4 times higher than those in lowland surface, suggesting an enhanced transformation of organics from gas- to solid- phase because of an increased photochemical oxidation and/or an increased condensation due to lower temperature, as well as an increased organic input from mountain plant emission. Air mass backward trajectories showed that compared with those derived from north/northwest China aerosols transported from the south contained higher concentrations of SO(4)(2-) and NH(4)(+) and lower concentrations of Ca(2+). Size distributions of NH(4)(+) and K(+) presented as an accumulation mode with a peak at 0.7-1.1 mu m, in contrast to Ca(2+) and Mg(2+), which maximized at the size 4.7-5.8 mu m as a coarse mode. SO(4)(2-) and NO(3)(-) showed a bimodal pattern with a large peak at the range 0.7-1.1 mu m and a small peak at the size of 4.7-5.8 mu m, whereas Na(+) and Cl(-) displayed a bimodal pattern with two equivalent peaks in the fine (&lt; 2.1 mu m) and coarse (&gt;= 2.1 mu m) ranges. pH values of the water-extracts demonstrate that aerosols originate from southern China are more acidic than those from the north/northwest, and the particles with a diameter of 0.7-11 mu m are most acidic.</p

Seasonal Variation of Ammonia and Ammonium Aerosol at a Background Station in the Yangtze River Delta Region, China

The measurement of atmospheric NH3 was conducted by mean of passive samplers from September 2009 to December 2010 at Lin&#39;an regional background station located in the economically blooming Yangtze River Delta (YRD) region in eastern China. NH4+ in fine particles was also measured in 2010 at this site. The NH3 concentration ranged from 0.1 to 41.8 ppb, with the annual average of 16.5 +/- 11.2 ppb in 2010. The daily NH4+ concentrations ranged from 0.02 to 19.2 mu g/m(3), with an annual average of 4.3 +/- 3.5 mu g/m(3). NH3 concentrations were highest in summer and lowest in winter, showing positive correlations with agricultural activities and temperature. The highest concentrations of NH4+ were in autumn coinciding with the period of active open burning of agricultural residues. The mean mass ratio of NH3/NHx is estimated to be 0.8 +/- 0.1 during 2010, indicating that NHx was mainly influenced by local sources around Lin&#39;an. The air mass back trajectory analysis suggests that both local sources and long-distance transport played important roles in the observed ammonium aerosol at Lin&#39;an. High NHx deposition in this regional background station suggests the urgency of reducing NH3 emission in the YRD region.</p

Comparison of abundances, compositions and sources of elements, inorganic ions and organic compounds in atmospheric aerosols from Xi'an and New Delhi, two megacities in China and India

Wintertime TSP samples collected in the two megacities of Xi&#39;an, China and New Delhi, India were analyzed for elements, inorganic ions, carbonaceous species and organic compounds to investigate the differences in chemical compositions and sources of organic aerosols. The current work is the first time comparing the composition of urban organic aerosols from China and India and discussing their sources in a single study. Our results showed that the concentrations of Ca, Fe, Ti, inorganic ions, EC, PAHs and hopanes in Xi&#39;an are 1.3-2.9 times of those in New Delhi, which is ascribed to the higher emissions of dust and coal burning in Xi&#39;an. In contrast, Cl- levoglucosan, n-alkanes, fatty alcohols, fatty acids, phthalates and bisphenol A are 0.4-3.0 times higher in New Delhi than in Xi&#39;an, which is attributed to strong emissions from biomass burning and solid waste incineration. PAHs are carcinogenic while phthalates and bisphenol A are endocrine disrupting. Thus, the significant difference in chemical compositions of the above TSP samples may suggest that residents in Xi&#39;an and New Delhi are exposed to environmental hazards that pose different health risks. Lower mass ratios of octadecenoic acid/octadecanoic acid (C-18:1/C-18:0) and benzo(a)pyrene/benzo(e)pyrene (BaP/BeP) demonstrate that aerosol particles in New Delhi are photochemically more aged. Mass closure reconstructions of the wintertime TSP indicate that crustal material is the most abundant component of ambient particles in Xi&#39;an and New Delhi, accounting for 52% and 48% of the particle masses, respectively, followed by organic matter (24% and 23% in Xi&#39;an and New Delhi, respectively) and secondary inorganic ions (sulfate, nitrate plus ammonium, 16% and 12% in Xi&#39;an and New Delhi, respectively).</p

Selected water-soluble organic compounds found in size-resolved aerosols collected from urban, mountain and marine atmospheres over East Asia

Primary (i.e. sugars and sugar-alcohols) and secondary (i.e. carboxylic acids) water-soluble organic compounds (WSOCs) in size-segregated aerosols from the urban and mountain atmosphere of China and from the marine atmosphere in the outflow region of East Asia were characterized on a molecular level. Levoglucosan is the most abundant compound among the quantified WSOCs in the urban and mountain atmosphere, whose concentration at the urban site was 1-2 orders of magnitude higher than that at the mountain and marine sites. In contrast, malic, succinic and phthalic acids were dominant among the measured WSOCs at the marine site. In the urban air, sugars except levoglucosan gave a bimodal size distribution with a large peak in fine range (&lt;2.1 mu m) and a small peak in coarse range (&gt;= 2.1 mu m) during winter, being opposite to those in spring. In contrast, these WSOCs at the mountain and marine sites dominated in the coarse range but diminished and even disappeared in the fine range. Geometric mean diameters (GMDs) of the measured WSOCs in the fine mode at the urban site were larger in winter than in spring. Levoglucosan and carboxylic acids except for azelaic and benzoic acids showed a larger GMD in the coarse mode at the marine site probably due to an increased hygroscopic growth.</p