Search

To investigate the characteristics, source apportionment, and potential source areas of carbonaceous aerosols in Chongqing during winter, PM 2.5 samples were collected from January 2021 to February 2021 in the urban areas of Wanzhou (WZ), Yubei (YB), and Shuangqiao (SQ). The results showed that the average mass concentrations of PM 2.5 , OC, and EC in SQ were (72.6 ±33.3), (18.2 ±8.2), and (4.4 ±1.7) μg·m -3 , respectively, higher than those in WZ[(67.2 ±30.3), (17.2 ±7.4), and (5.1 ±2.4) μg·m -3 ] and YB[(63.4 ±25.7), (15.4 ±6.3), and (4.2 ±1.9) μg·m -3 ]. Compared with that during the clear period, the concentration and fraction of EC in total carbon increased by 103.0% and 8.1%, respectively, in WZ compared to that in other areas during pollution period, whereas the OC/EC ratio was decreased significantly (-10.5%), indicating that the primary emission of carbonaceous aerosols increased significantly during the pollution period. The average mass concentrations of secondary organic carbon (SOC) in SQ and YB were (7.7 ±4.8) μg·m -3 and (6.9 ±2.8) μg·m -3 significantly higher, respectively, than that in WZ[(4.5 ±1.9) μg·m -3 ] during the campaign. This indicated that the secondary transformation had a greater influence on the carbonaceous aerosols in SQ and YB than that in WZ. Furthermore, in contrast to that in WZ, the ratios of SOC/OC were increased with the increase in PM 2.5 concentrations, and significant correlations between SOC concentration and aerosol water content, NO 2 concentration, and the value of NOR were observed in SQ and YB ( P < 0.01), indicating that the increasing of carbonaceous aerosol concentrations might be mainly driven by the SOC with -NO 2 groups produced by aqueous chemical reactions during winter in SQ and YB. The positive definite matrix factor (PMF) results in these urban areas showed that the contribution of biomass/coal combustion source in WZ (47.4%) was significantly higher than that in YB (34.2%) and SQ (38.1%), whereas the gasoline motor vehicle emission and secondary transformation impacts were more significant in YB. The results of the concentration weighted trajectory (CWT) showed that the potential sources of carbonaceous aerosols were mainly the local and northeastern parts of these urban areas (such as Changshou).

Oxygenated volatile organic compounds (OVOCs) are important intermediates in the troposphere and the most important sources of ozone. Proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) was used to measure VOCs in the Chengdu Plain, Southwestern China. The diurnal variations, photochemical reactivity, O 3 formation potential, and sources were also investigated. The mixing ratios of ten kinds of VOCs (acetaldehyde, acetone, isoprene, Methyl ethyl ketone, Methyl vinyl ketone and Methacrolein, benzene, toluene, styrene, C8 aromatics, and C9 aromatics) were (10.97±4.69)×10 -9 . The concentrations of OVOCs, aromatic hydrocarbons, and biogenic VOCs were (8.54±3.44)×10 -9 , (1.53±0.93)×10 -9 , and (0.90±0.32)×10 -9 , respectively. Isoprene, acetaldehyde, and m-xylene were the top three photochemically active species with the greatest O 3 formation potentials. The dominant three OVOCs species (acetaldehyde, acetone, and MEK) were mainly derived from local biogenic sources and anthropogenic secondary sources, and acetone had a strong regional background level, indicating that pollution in this area is significantly affected by regional transmission. This study deepens the understanding of regional O 3 formation mechanisms in southwest China and provides a basis for the scientifically informed control of O 3 pollution.

A total of 87 daily PM 2.5 samples were collected in the urban area of Suzhou city during 2015, representing spring, summer, autumn, winter, respectively. Mass concentration of PM 2.5 was analyzed gravimetrically. Water-soluble inorganic ions, including F - , Cl - , NO 3 - , SO 4 2- , Na + , NH 4 + , K + , Mg 2+ and Ca 2+ , were determined by ion chromatography. The average mass concentration of PM 2.5 was (74.26±38.01) μg·m -3 . The seasonal variations of PM 2.5 concentrations decreased in the order of winter > spring > autumn > summer. The average total mass concentrations of 9 ions was (43.95±23.60) μg·m -3 , and the order of concentration of ions was NO 3 - > SO 4 2- > NH 4 + > Na + > Cl - > K + > Ca 2+ > F - > Mg 2+ . Seasonal variation of ion concentrations was significant, with the highest concentration observed in winter and the lowest in summer. The secondary inorganic species, including SO 4 2- , NO 3 - and NH 4 + (SNA) were the major components of the water-soluble ions in PM 2.5 . SNA's correlations with each other were significant. SO 4 2- , NO 3 - and NH 4 + were probably in the form of NH 4 NO 3 and (NH 4 ) 2 SO 4 . The [NO 3 - ]/[SO 4 2- ] ratio approaching to 1 implied that mobile sources were as important as stationary sources. Ion balance calculations indicated strong correlations between anion and cation equivalents. The PM 2.5 was acidic. Industrial emission, combustion process, secondary formation and fugitive dust were the major sources of the water-soluble ions in PM 2.5. .

In order to investigate the characteristics of atmospheric trace metals deposition in the hinterland of the Three Gorges Reservoir, the wet and dry deposition samples were collected at an urban area sampling site in Wanzhou during January to June 2014. Besides, the samples were collected at five other sampling sites in April 2014 for comparative analysis, including factory region, town suburb, nature reserve, county suburb, and rural area. pH, conductivity, and trace metals (Al, As, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Li, Mn, Pb, Ni, Sb, Sr, Sn, Ti, Zn, V) were analyzed. In urban area, the acid rain frequency was 48.44% , and the acid rain occurred mainly in the period of January to April. The order of acid rain frequency in various functional areas was factory region > urban area > county suburb > town suburb > nature reserve > county rural area. All of the trace metals in wet deposition during the sampling period were lower than the National Environmental Quality Standard for Surface Water Standard of Class III. Cd, Cu, Ph and Zn were found exceeding the standard of class I , and the pollution in factory region was more serious compared to other functional areas. The extract pH of dry deposition in urban area was in the range of 4.91-6.74, with an average value of 5.79. The order of dry deposition in various functional areas was factory region > county suburb > urban area > county rural area > town suburb > nature reserve, which was exactly the same as that of the wet deposition, indicating the similar sources of dry and wet deposition. In urban area, the contents of Ba, Co, Cu, Cr, Li, Mn, Ni, Sr, Zn in dry deposition were greater than those in wet deposition, but the contents of Al, As, B, Bi, Cd, Fe, Ph, Sb, Sn, Ti, V showed the opposite trend. Analysis of the enrichment factors showed that Al was in moderate enrichment, while Bi and Cd were significantly enriched.

In the present work, a method was developed for determining lead, zinc, copper, cadmium, znd chromium in PM2. 5 by inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis with microwave digestion and glass fibre filter collection of samples. The microwave digestion systems were investigated and the experimental conditions were optimized. The results show that (1) HNO3-H2O02 digestion system is more stable and complete than HNO3-HCl and HNO3-H2 SO4 digestion systems; (2) The most sensitive emission wave length of lead, zinc, copper, cadmium, and chromium are 220.353, 213.857, 327.393, 228.802, and 267.716 nm, respectively; (3) The highest signal-to-noise ratios were observed under the conditions: RF power of 1 300 W, peristaltic pump flow rate of 1.5 mL x min(-1), cooling gas flow rate of 15 L x min(-1), and carrier gas flow rate of 0.8 L x min(-1). In addition, the detection limit for these elements ranged between 2.02 x 10(-3) and 8.20 x 10(-3(μg x mL(-1), the relative standard deviations (RSD, n = 6) for the samples were in the range of 1.86%-2.82%, and the recovery for the elements determined was from 91.6% to 103.7%. The proposed method was used for determination of the above five elements in atmospheric fine particulate matter at Wanzhou Monitoring Site of Chongqing Institute of Green and Intelligent Technology. The results revealed that the atmospheric fine particulate matter at this monitoring site was not polluted by cadmium and chromium, lead was at the level of potential contamination, while zinc and copper were at the level of slight pollution.

Total suspended particles (TSP), collected during a typical haze period in Guangzhou, were analyzed for the fatty acids (C12-C30) and low molecular weight dicarboxylic acids (C3-C9) using gas chromatography/mass spectrometry (GC/MS). The results showed that the concentration of total fatty and carboxylic acids was pretty high during the haze episode. The ratios of fatty acids and carboxylic acids in haze to those in normal days were 1.9 and 2.5, respectively. During the episode of the increasing pollution, the fatty acids and carboxylic acids at night (653 ng x m(-3)) was higher than that (487 ng x m(-3)) in days. After that, the level of fatty acids and carboxylic acids in days (412 ng x m(-3)) was higher than that (336 ng x m(-3)) at night. In general, the time-series of fatty acids and carboxylic acids was similar to that of the air particle and carbonaceous species, however, the trend of the ratio of fatty acids and carboxylic acids to organic carbon was opposite to that of air particle and carbonaceous species. This ratio decreased with the increase of the concentration of air particle and after the night of 27th, the ratio increased with the decrease in the concentration of air particle. The results showed that haze pollution had a significant inhibitory effect on the enrichment of fatty and carboxylic acids. Based on the ratio of malonate to succinate (C3/C4), it could be found that primary sources contribute more to the atmospheric fatty and carboxylic acids during the autumn haze pollution periods in Guangzhou.

Volatile Organic Compounds (VOCs) in Foshan City were investigated in December 6 to 30 2008. The concentrations of VOCs in haze days were significantly higher than those in no-haze days. Toluene (68.93 microg x m(-3) +/- 37.78 microg x m(-3)) was the most abundant compound of VOCs in haze days and i-pentane (20.59 microg x m(-3) +/- 14.28 microg x m(-3)) was the most abundant compound in no-haze days, respectively. During haze episodes, the diurnal variations of alkanes and alkynes were not significantly; however, alkenes and aromatic hydrocarbon decreased significantly at noon. During no-haze episodes, the diurnal variations patterns of VOCs were stable. Propylene-equivalent concentrations in haze days were significantly higher than those in no-haze days, toluene was the most abundant compound of Propylene-equivalent concentration in haze days, followed by propene and ethene; propene was the most abundant compound in no-haze days, followed by ethene and 1-butene. High concentration of benzene (18.1 microg x m(-3)) in haze days posed a great health threat to public in Foshan city. Both diurnal variation of VOCs and measured ratios indicated vehicular emissions acted as the main sources of most VOCs and other sources like solvent application also contributed to VOCs (benzene and toluene).

The purpose of this study is to investigate the effect of fog processes on the physical and chemical properties of aerosol particles in an urban atmosphere. Atmospheric particles were collected in the urban atmosphere of Beijing during fog and non-fog episodes. The morphology, size and elemental composition of individual particles were characterized using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDX). EDX analysis showed that elongated particles were composed of Ca-K-S or Ca-S, and most sub-round particles contained sulfur. Large amounts of elongated and sub-round particles were identified in the samples collected during fog episodes, and they were rarely detected in the samples collected during non-fog episodes. This suggests that the high relative humidity in the fogs facilitated the formation of elongated and sub-round particles. Number concentrations of particles larger than 0.2 microm were about 5 to 8 times higher during the fog episodes. In addition, a new mode around 0.4 microm appeared in number size distribution of particles during the fog episodes. These results indicate that heterogeneous reactions in the fogs could greatly change the chemical and physical properties of particles.

To understand the concentration levels and temporal variations of the mineral component of PM2.5 in the ambient air of Beijing, weeklong samples were simultaneously collected for one year at Qinghuayuan and Chegongzhuang. The concentrations of five major crustal elements Al, Si, Ca, Mg, and Fe exhibited similar significant weekly variations, with their maximum values in the week of a serious dust event in the spring of 2000. Obvious seasonal pattern was also found for these elements, indicating different influences on fine mineral particles from the source emissions and meteorology in different seasons. Soil dust concentration increased from a low level in summer to the peak value (21.1 microg x m(-3)) in spring, suggesting that frequent dust events made a significant contribution to fine soil dust. A large number of construction activities in Beijing substantially increased the loading of fine calcium-bearing particles, and their emissions thus need to be further controlled.