Seasonal Characteristics of Black Carbon Aerosol and its Potential Source Regions in Baoji, China

Continuous measurements of black carbon (BC) aerosol were made at a midsized urban site in Baoji, China, in 2015. The daily average mass concentrations varied from 0.6 to 11.5 mu g m(-3), with an annual mean value of 2.9 +/- 1.7 mu g m(-3). The monthly variation indicated that the largest loading of BC occurred in January and the smallest in June. The mass concentrations exhibited strong seasonality, with the highest occurring in winter and the lowest in summer. The large BC loadings in winter were attributed to the increased use of fuel for domestic heating and to stagnant meteorological conditions, whereas the low levels in summer were related to the increase in precipitation. BC values exhibited similar bimodal diurnal patterns during the four seasons, with peaks occurring in the morning and evening rush hours and an afternoon trough, which was associated with local anthropogenic activities and meteorological conditions. A potential source contribution function model indicated that the effects of regional transport mostly occurred in spring and winter. The most likely regional sources of BC in Baoji were southern Shaanxi province, northwestern Hubei province, and northern Chongqing during spring, whereas the northeastern Sichuan Basin was the most important source region during winter

Seasonal Distribution of Atmospheric Coarse and Fine Particulate Matter in a Medium-Sized City of Northern China

Atmospheric particulate matter (PM) was measured continuously at an urban site in Baoji city in northern China in 2018 to investigate the seasonal distribution characteristics. Coarse PM (PM2.5–10) was more prevalent in spring, substantially due to the regional transport of dust. High loadings of coarse PM were found at night compared to daytime, which could result from high production and unfavorable dispersion conditions. Fine PM (PM2.5) constituted, on average, 54% of the total PM mass concentration, whereas it contributed more than 97% of the total PM number concentration. The number and mass concentrations of fine PM increased substantially in the winter, which was possibly due to the enhanced production of atmospheric secondary processes and coal combustion. Precursor gaseous pollutants and meteorology greatly influenced the PM distributions. Fine PM was associated more strongly with gas pollutants than coarse PM, which suggested that it largely originated from secondary production and combustion sources. High relative humidity appeared to promote the production of fine PM, whereas it facilitated the removal of coarse PM. This study highlights that different air-pollution control strategies should be used for coarse and fine PM according to the distribution characteristics and influencing factors in similar medium-sized urban areas

Composition and size distribution of airborne particulate PAHs and oxygenated PAHs in two Chinese megacities

Concentrations and compositions of PAHs and oxygenated PAHs (OPAHs) in four size ranges of ambient particles (9.0 mu m) collected in Xi'an and Guangzhou, two megacities of China, during the winter and summer of 2013 were measured and compared with those in 2003. The TSP-equivalent concentrations of Sigma 14PAHs in Xi'an and Guangzhou are 57 +/- 20 and 18 +/- 23 ng m(-3) in winter, 5-10 times higher than those in summer. PAHs in both cities are dominated by 5- and 6-ring congeners in summer. In contrast, they are dominated by 4- and 5-ring congeners in winter, probably due to enhanced gas-to-particle phase partitioning of the semi-volatile PAHs. TSP-equivalent Sigma OPAHs during winter are 54 +/- 15 and 23 +/- 32 ng m(-3) in Xi'an and Guangzhou and dominated by 5-ring OPAHs

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'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'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'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'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'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'an and New Delhi, accounting for 52% and 48% of the particle masses, respectively, followed by organic matter (24% and 23% in Xi'an and New Delhi, respectively) and secondary inorganic ions (sulfate, nitrate plus ammonium, 16% and 12% in Xi'an and New Delhi, respectively)

Extrapolation of anthropogenic disturbances on hazard elements in PM2.5 in a typical heavy industrial city in northwest China

Baoji is a typical heavy industrial city in northwest China. Its air quality is greatly impacted by the emission from the factories. Elements in fine particulate matter (PM2.5) that are greatly emitted from anthropogenic sources could pose diverse health impacts on humans. In this study, an online AMMS-100 atmospheric heavy metal analyzer was used to quantify 30 elements in PM2.5 under the weak and strong anthropogenic disturbance scenarios before the city lockdown period (from January 9(th) to 23(rd)) and the lockdown period (from January 26(th) to February 9(th)) due to the outbreak of COVID-19 in 2020. During the lockdown period, the average total concentration of total quantified elements was 3475.0 ng/m(3), which was 28% and 33% lower than that of the week and strong anthropogenic disturbance scenarios during the pre-lockdown period. The greatest reductions were found for the elements of chromium (Cr), titanium (Ti), manganese (Mn), and Zinc (Zn), consistent with the industrial structure of Baoji. The mass concentrations of most elements showed obvious reductions when the government post-alerted the industries to reduce the operations and production. Dust, traffic sources, combustion, non-ferrous metal processing, and Ti-related industrial processing that are the contributors of the elements in the pre-lockdown period were apportioned by the positive matrix factorization (PMF) model. Substantial changes in the quantified elements' compositions and sources were found in the lockdown period. Health assessment was conducted and characterized by apportioned sources. The highest non-carcinogenic risk (HQ) was seen for Zn, demonstrating the high emissions from the related industrial activities. The concentration level of arsenic (As) exceeded the incremental lifetime carcinogenic risk (ILCR) in the lockdown period. This could be attributed to the traditional firework activities for the celebration of the Chinese New Year within the lockdown period

REGγ Mediated Regulation of p21Waf/Cip1, p16INK4a and p14ARF/p19ARF in Vivo

peer reviewedp21Waf/Cip1, p16INK4a and p14ARF (p19ARF in mice) have been demonstrated to be degraded by REGγ-proteasome pathway in an ATP- and ubiquitin-independent manner in vitro. However, the in vivo roles of REGγ mediated-degradation of p21Waf/Cip1, p16INK4a and p14ARF remain unclear. In this study, we showed enhanced expression of p21Waf/Cip1, p16INK4a and p19ARF in multiple tissues from REG–/– mice compared to REG+/+ mice. Furthermore, we examined the expression of p21Waf/Cip1, p16INK4a and p14ARF in different cancer tissues and observed that the REGγ protein levels were highly expressed in different human cancers while the level of p21Waf/Cip1, p16INK4a and p14ARF appears to be inversely corre- lated. These results demonstrate that REGγ may exert its function in physiological and pathological conditions through degradation of p21Waf/Cip1, p16INK4a and p14ARF in vivo

Comparison of dicarboxylic acids and related compounds in aerosol samples collected in Xi'an, China during haze and clean periods

PM10 aerosols from Xi&#39;an, a mega city of China in winter and summer, 2009 were measured for secondary organic aerosols (SOA) (i.e., dicarboxylic acids (DCA), keto-carboxylic acids, and &alpha;-dicarbonyls), water-soluble organic (WSOC) and inorganic carbon (WSIC), elemental carbon (EC) and organic carbon (OC). Molecular compositions of SOA on haze and clean days in both seasons were compared to investigate their sources and formation mechanisms. DCA in the samples were 1843&plusmn;810ngm-3 in winter and 1259&plusmn;781ngm-3 in summer, respectively, which is similar and even higher than those measured in 2003. Oxalic acid (C2, 1162&plusmn;570ngm-3 in winter and 1907&plusmn;707ngm-3 in summer) is the predominant species of DCA, followed by t-phthalic (tPh) in winter and phthalic (Ph) in summer. Such a molecular composition is different from those in other Asian cities where succinic acid (C4) or malonic acid (C3) is the second highest species, which is mostly due to significant emissions from household combustion of coal and open burning of waste material in Xi&#39;an. Mass ratios of C2/diacids, diacids/WSOC, WSOC/OC and individual diacid-C/WSOC are higher on the haze days than on the clean days in both seasons, suggesting an enhanced SOA production under the haze condition. We also found that the haze samples are acidic while the clean samples are almost neutral. Such a difference in particle acidity is consistent with the enhanced SOA production, because acid-catalysis is an important aqueous-phase formation pathway of SOA. Gly/mGly mass ratio showed higher values on haze days than on clean day in both seasons. We comprehensively investigated the ratio in literature and found a consistent pattern. Based on our observation results and those documented data we proposed for the first time that concentration ratio of Gly/mGly can be taken as an indicator of aerosol ageing.</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

Airborne particulate organic markers at the summit (2060 m,a.s.l.) of Mt. Hua in central China during winter: Implications for biofuel and coal combustion

Sugars, n-alkanes and PAHs in PM10 and size-segregated samples collected from the summit (2060 m, altitude) of Mt. Hua in Guanzhong Plain, central China during the winter of 2009 were characterized using a GC/MS technique. Concentrations of sugars, n-alkanes and PAHs in PM10 are 107&plusmn;52, 121&plusmn;63, 7.3&plusmn;3.4 ng m&minus;3, respectively. Levoglucosan and fossil fuel derived n-alkanes are more abundant in the air masses transported from southern China than in those from northern China with no spatial difference found for PAHs, suggesting that emissions from biomass burning and vehicle exhausts are more significant in southern part of the country. Dehydrated sugars, fossil fuel derived n-alkanes and PAHs presented a unimode size distribution, peaking at the size of 0.7&ndash;1.1 &mu;m, whereas non-dehydrated sugars and plant wax derived n-alkanes showed a bimodal pattern, peaking at 0.7&ndash;2.1 and 5.8&ndash;9.0 &mu;m, respectively. Principal component analysis showed that biofuel combustion plus plant emission is the most important source in Mt. Hua, being different from the cases in Chinese urban areas where fossil fuel combustion is the major source. By comparison with previous mountain and lowland observations and aircraft measurements we found that wintertime PAHs in China are still characterized by coal burning emissions especially in the inland regions, although in the country increasing rate of SO2 emission from coal combustion has decreased and emissions of vehicle exhaust has sharply increased.</p