Observational Insights into Isoprene Secondary Organic Aerosol Formation through the Epoxide Pathway at Three Urban Sites from Northern to Southern China.

Isoprene is the most abundant precursor of global secondary organic aerosol (SOA). The epoxide pathway plays a critical role in isoprene SOA (iSOA) formation, in which isoprene epoxydiols (IEPOX) and/or hydroxymethyl-methyl-α-lactone (HMML) can react with nucleophilic sulfate and water producing isoprene-derived organosulfates (iOSs) and oxygen-containing tracers (iOTs), respectively. This process is complicated and highly influenced by anthropogenic emissions, especially in the polluted urban atmospheres. In this study, we took a 1-year measurement of the paired iOSs and iOTs formed through the IEPOX and HMML pathways at the three urban sites from northern to southern China. The annual average concentrations of iSOA products at the three sites ranged from 14.6 to 36.5 ng m-3. We found that the nucleophilic-addition reaction of isoprene epoxides with water dominated over that with sulfate in the polluted urban air. A simple set of reaction rate constant could not fully describe iOS and iOT formation everywhere. We also found that the IEPOX pathway was dominant over the HMML pathway over urban regions. Using the kinetic data of IEPOX to estimate the reaction parameters of HMML will cause significant underestimation in the importance of HMML pathway. All these findings provide insights into iSOA formation over polluted areas.

[Characterization and Size Distribution of Carbonaceous Aerosols at Mountain Dinghu].

To understand the characterization and sources of carbonaceous aerosols at Mountain Dinghu, organic carbon (OC) and elemental carbon (EC) in size-resolved aerosol samples were measured at a regional background site in South China using a DRI Model 2001A analyzer. The average mass concentrations of organic carbon (OC) are (5.6±2.0) µg ·m-3 in PM1.1, (7.3±2.4) µg ·m-3 in PM2.1, and (12.8±4.0) µg ·m-3 in PM9.0; the average mass concentrations of elemental carbon (EC) are (2.3±1.4) µg ·m-3in PM1.1, (2.7±1.6) µg ·m-3 in PM2.1, and (3.4±1.7) µg ·m-3 in PM9.0. OC concentrations in PM1.1 and PM2.1 account for 43.8% and 57.0% of OC in PM9.0, and EC concentrations in PM1.1 and PM2.1 account for 67.6% and 79.4%, respectively. OC and EC are enriched with fine particles. In PM1.1 and PM2.1, the highest concentrations of OC and EC are measured in autumn, and the lowest concentration of OC is measured in winter and EC in summer. In PM9.0, the highest OC concentration is measured in summer. Carbonaceous aerosols are mainly composed of OC2, EC1, OC3, and OC4. In summer, the concentration of OC3 is higher than that of EC1, suggesting that biogenic sources are dominant during summer. The concentration of EC1 in winter is the highest, indicating that the impacts of motor vehicle emissions are prominent in the local area during winter. OC and EC both show bimodal distributions in four seasons, with peaks in the size ranges of 0.43-0.65 µm for fine particles and 3.3-5.8 µm for coarse particles. In PM1.1 and PM2.1, the sources of OC are mainly primary emissions. In PM2.1, the highest concentration of SOC is measured in spring at (3.0±1.4) µg ·m-3 and the lowest in winter at (1.3±1.4) µg ·m-3, indicating that the secondary aerosol formation is significant in spring. At the Mountain Dinghu background site, OC is mainly from coal combustion and motor vehicle emissions for fine particles and from biogenic sources for coarse particles. EC is mainly from coal combustion, motor vehicle emissions, and dust.

[Mass Concentrations and Size Distributions of Water-soluble Inorganic Ions in Atmospheric Aerosols in Beibei District, Chongqing].

In order to study the concentration and distribution characteristics of water-soluble inorganic ions in aerosol particles of the Beibei district of Chongqing, aerosol samples were collected with an Andersen cascade impactor between March 2014 and February 2015. Water-soluble inorganic ions, including Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO42- were determined for different particle sizes (9.00, 5.80, 4.70, 3.30, 2.10, 1.10, 0.65, and 0.43 µm) using the ion chromatography method. Results showed that SO42-, NH4+, NO3-, Cl-, Na+, and K+ were mainly distributed in fine particles, while Mg2+, Ca2+, and F- were mainly present in coarse particles. SNA (SO42-, NH4+, and NO3-) exhibited clear unimodal distribution, with peaks in the droplet mode of 0.65-1.10 µm, mainly present in the form of (NH4)2SO4 and NH4NO3 in fine particles. The formation of SO42- is mainly attributed to in-cloud processes and partly to oxidation of SO2. Na+, Cl-, and Mg2+ exhibited bimodal distribution in coarse and fine particles; K+ was a single peak distribution in the range of 0.43-1.10 µm, while peaks of F- and Ca2+ concentrations were in coarse particles. Average annual concentrations of total water-soluble ions in PM2.1 and PM9.0 were (32.68±15.28) µg·m-3and (48.01±19.66) µg·m-3 over the observation period. Seasonal variations of PM2.1 and PM9.0concentrations decreased in the order of winter > spring > summer > autumn. This was the same for most ions, but a small number of ions (F-, Mg2+ and Ca2+) had a different pattern in the spring, summer, and winter. The SNA were the major components of water-soluble ions in PM2.1, and Ca2+ was the major component of water-soluble ions in PM9.0 besides SNA. The concentration of cations was significantly higher than that of anions' in PM2.1 and PM9.0, with a certain correlation between different ions. Emissions from motor vehicle exhaust, combustion processes, soil sources, and fugitive dust were the major sources of water-soluble ions in this area. The effect of air temperature on secondary ions is significant (P<0.05), but relative humidity and wind speed have no significant effect (P>0.05).

[Pollution Characteristics of Organic Carbon and Elemental Carbon in Atmospheric Aerosols in Beibei District, Chongqing].

To study the pollution characteristics of atmospheric carbon aerosols, aerosol samples were collected via a cascade impactor (Andersen) from March 2014 to February 2015 in Beibei District, Chongqing. Organic carbon (OC) and element carbon (EC) were detected using a DRI 2001A carbon analyzer. The results showed that the annual average concentrations of OC and EC in PM2.1 were (16.3±7.6) and (1.8±0.7), respectively, and (25.0±9.6), and (3.2±1.3) µg·m-3, respectively, in PM9.0. The concentrations of both OC and EC were higher in winter and spring than in summer and autumn for PM2.1, whereas, for PM9.0, the concentration of OC was higher in summer and spring than in winter and autumn and that of EC was higher in winter and spring than in summer and autumn. The particle size distributions of OC and EC for the study year were analyzed, and it was found that those of OC were bimodal, with peaks in the size ranges of 0.43-0.65 µm for fine particles and 4.7-5.8 µm for coarse particles, and those of EC were trimodal, with peaks in the size ranges of 0.43-0.65 µm for fine particles and 4.7-5.8 µm for coarse particles and a concurrent significant peak in the particle size range of 2.1-3.3 µm. In addition, the correlations between OC and EC were analyzed and the SOC in PM2.1 was estimated. It was found that the average concentration of SOC was (6.3±5.9) µg·m-3, which accounted for 33.5%±22.6% of the OC concentration in Beibei District. Furthermore, OC and EC were significantly correlated. Finally, the pollution sources of atmospheric aerosols in Beibei were analyzed, and it was found that the pollution in Beibei mainly came from the exhaust gas of gasoline vehicles, biomass combustion, and coal combustion.

[Characteristics of the Size Distribution of Water Soluble Inorganic Ions in Sanya, Hainan].

Size-resolved filter samples were collected in Sanya every other week from June 2012 to May 2014. The mass concentrations of water-soluble inorganic ions, including anions (Cl-, NO3-, SO42-) and cations (Na+, NH4+, K+, Mg2+, Ca2+) were measured by ion chromatography. The results showed that the total concentrations of measured water-soluble inorganic ions were (8.91±7.27) and (11.34±9.37) µg·m-3 in PM2.1 and PM2.1-9, respectively. In PM2.1, SO42- and NH4+ comprised 72.2% of all water-soluble inorganic ions, while in PM2.1~9, Cl-, Ca2+ and Na+ comprised 67.6% of all water-soluble inorganic ions. In PM2.1, the total concentrations of water-soluble inorganic ions had highest concentrations in winter and lowest concentrations in summer. In PM2.1~9, the total concentrations of water-soluble inorganic ions presented the highest concentrations in summer. SO42- and NH4+ showed bimodal size distributions and the peaks in the fine mode shifted from 0.43-0.65 µm in spring, summer and autumn to 0.65-1.1 µm in winter. NO3-, Na+, Cl-, Ca2+ and Mg2+ were unimodal with the peaks in the coarse mode of 4.7-9.0 µm. K+ showed bimodal size distribution with the fine mode at 0.43-0.65 µm and the coarse mode at 4.7-5.8 µm. PCA analysis showed that water-soluble inorganic ions were mainly affected by the secondary formation, sea salt and soil particles or falling dust.

Spatial and seasonal variations of isoprene secondary organic aerosol in China: Significant impact of biomass burning during winter.

Isoprene is a substantial contributor to global secondary organic aerosol (SOA). The formation of isoprene SOA (SOAI) is highly influenced by anthropogenic emissions. Currently, there is rare information regarding SOAI in polluted regions. In this study, one-year concurrent observation of SOAI tracers was undertaken at 12 sites across China for the first time. The tracers formed from the HO2-channel exhibited higher concentrations at rural sites, while the tracer formed from the NO/NO2-channel showed higher levels at urban sites. 3-Methyltetrahydrofuran-3,4-diols exhibited linear correlations with their ring-opening products, C5-alkenetriols. And the slopes were steeper in the southern China than the northern China, indicating stronger ring-opening reactions there. The correlation analysis of SOAI tracers with the factor determining biogenic emission and the tracer of biomass burning (levoglucosan) implied that the high level of SOAI during summer was controlled by biogenic emission, while the unexpected increase of SOAI during winter was largely due to the elevated biomass burning emission. The estimated secondary organic carbon from isoprene (SOCI) exhibited the highest levels in Southwest China. The significant correlations of SOCI between paired sites implied the regional impact of SOAI in China. Our findings implicate that isoprene origins and SOAI formation are distinctive in polluted regions.

[Concentrations and Size Distributions of Water-soluble Inorganic Ions in Aerosol Particles in Taiyuan, Shanxi].

Size-resolved filter samples were collected in Taiyuan every other week from June 2012 to May 2014. The mass concentrations of water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3- and SO42-) were measured by ion chromatography. The results showed that the total concentrations of measured water-soluble ions were (15.39±9.91), (21.10±15.49) and (36.34±18.51) µg·m-3 in PM1.1, PM2.1 and PM9, respectively. In PM1.1 and PM2.1, secondary water-soluble ions (SO42-, NO3- and NH4+) comprised 87.59% and 86.30% of all water-soluble ions, respectively, while in PM9, SO42- and Ca2+ comprised 32.78% and 28.54% of all water-soluble ions, respectively. SO42- and NH4+ had higher concentrations in winter and summer, and lower in spring and autumn. NO3-, K+and Cl- presented similar seasonal variation with a descending order of winter >autumn >spring >summer, and Ca2+ and Mg2+ followed the sequence of spring >winter >autumn >summer. SO42- and NH4+ showed a unimodal size distribution and the peak in the fine mode shifted from 0.43-0.65 µm in spring and autumn to 0.65-1.1 µm in summer. NO3- showed a bimodal size distribution. NO3- and NH4+ were dominated by the fine mode peaking at 0.43-2.1 µm in winter, and NO3- was dominated by the coarse mode peaking at 4.7-5.8 µm in summer. K+, Na+and Cl- also showed a bimodal size distribution with the fine mode at 0.43-1.1 µm and the coarse mode at 4.7-5.8 µm. Ca2+, Mg2+ and F- were unimodal with the peak in the coarse mode of 4.7-5.8 µm. On heavily polluted days, the mass concentrations of secondary water-soluble ions and Cl- accumulated, and secondary water-soluble ions were unimodal with the peak in the fine mode of 1.1-2.1 µm. However, on clear days, secondary water-soluble ions showed a bimodal size distribution with the fine mode at 0.43-0.65 µm and the coarse mode at 4.7-5.8 µm. The peak of secondary water-soluble ions in the fine mode shifted. PCA analysis showed that the sources of water-soluble ions were dominated by the secondary formation, coal combustion, industrial emission, biomass burning, and soil particles or falling dust.

[Characteristics of the Size Distribution of Water Soluble Inorganic Ions During a Typical Haze Pollution in the Autumn in Shijiazhuang].

To characterize the size distribution of water soluble inorganic ions (WSⅡ) in haze days, particle samples were collected by an Andersen cascade impactor in Shijiazhuang from October 15 to November 14 in 2013, and the concentrations of eight kinds of WSⅡ (Na+, NH4+, K+, Mg2+, Ca2+, Cl-, NO3-and SO42-) during a typical haze episode were analyzed by ion chromatography. Sources and formation mechanism of WSⅡ were analyzed based on their size distributions. The results showed that Shijiazhuang suffers serious air pollution during the autumn season. The daily average concentrations of PM10and PM2.5were (361.2±138.7) µg·m-3 and (175.6±87.2) µg·m-3 and the daily average concentration of PM2.5was 2.3 times as high as the national secondary standard. The total water soluble inorganic ion concentrations (TWSⅡ) in clean days, light haze days and heavy haze days were(64.4±4.6)µg·m-3, (109.9±22.0)µg·m-3 and (212.9±50.1) µg·m-3 respectively. In addition, the ratio of secondary inorganic ions (SNA:SO42-, NO3- and NH4+) in TWSⅡ increased from 44.9% to 77.6% as changed from clean days to the heavy haze days, suggesting the evolution of haze episodes mainly originated from the formation and accumulation of SNA. The size distributions of SO42-, NO3- and NH4+ were bimodal in clean days, peaking at 0.43 -0.65 µm and 4.7-5.8 µm, respectively, which changed to unimodal distribution in both the light and heavy haze days, peaking at 0.65-1.1 µm. Owing to high humidity during the heavy haze days, the aqueous phase reactions of SO42- and NO3- were likely promoted, which led to the transformation of condensation mode in clean days to the droplet mode in haze days. The size distributions of Na+, Mg2+ and Ca2+ were different with that of SNA, which showed a coarse mode peaking at 4.7-5.8 µm both in clean and haze days, whereas K+and Cl- showed a bimodal distribution both in clean and haze days, although the modal size was different in clean and haze days.

[Characteristics of Water-soluble Inorganic Ions in Atmospheric Aerosols in Shenyang].

To investigate the levels and seasonal variation of water soluble inorganic components in ambient aerosol in Shenyang, 25 samples were collected with Andersen cascade sampler from Jun. 2012 to May. 2013 and nine water-soluble ions in samples were analyzed by IC. The different characteristics of aerosols between clean and pollution days in winter were discussed based on these samples. The results showed that the annual concentrations of total water soluble inorganic ions were 22.30 µg·m-3 and 14.29 µg·m-3 in fine and coarse particles, and SO42- and Ca2+ were the most abundant ions, respectively. The ratio of mass concentration between SO42- and NO3- was 2.28 and the NH4+ existed in the form of (NH4)2SO4 and NH4NO3 in fine particles. The concentrations of total water soluble ions in fine particles were higher in winter and spring compared with those in summer and autumn, and they varied significantly between different seasons. The fossil fuel consumption led to the maximum values of secondary inorganic ions in fine particles during winter. The concentrations of total water soluble ions in coarse particles varied slightly though they were higher in autumn and lower in winter, and the wind-drifting sand was responsible for the higher concentration of Ca2+ in autumn in coarse particles. The concentration of SO42-, NO3-, NH4+ accounted for 80% of total water soluble inorganic ions during clean days and rose to 94% during pollution days. The ions were mostly concentrated in the size ranges of 0.43-0.65 µm and 0.43-2.1 µm respectively during clean and pollution days in fine mode. The peaks of SO42-, NO3-, NH4+ in fine mode shifted from 0.43-0.65 µm to 1.1-2.1 µm, which meant these ions were transformed from condensing mode to droplets mode during pollution days. The air mass produced at Lake Baikal and transported through high altitude to the sampling point caused clean days, however the air mass transported through industrial areas might bring pollutions to the sampling point then caused pollution days.

[Size distributions of water-soluble inorganic ions in atmospheric aerosols in Fukang].

To investigate the levels and size distributions of water soluble inorganic components, samples were collected with Andersen cascade sampler from Feb. 2011 to Feb. 2012, in Fukang, and were analyzed by IC. The variation trend, concentration level, composition, sources and size distribution of major ions during non-heating period were compared with heating period. Based on the specific samples, ionic compositions and size distributions were analyzed during heavy pollution, straw burning and spring planting periods. The results showed that inorganic components in Fukang were severely affected by heating. The total water soluble ions in fine and coarse particles during non-heating and heating periods were 11.17, 12.68 microg x m(-3) and 35.98, 22.22 microg x m(-3), respectively. SO4(2-) was mainly from saline-alkali soil, NO3(-) and NH4(+) were from resuspension of farmland soil during non-heating period, while SO4(2-), NO3(-) and NH4(+) were all from the fossil fuel consumption during the heating period. All ions were bimodal distribution during non-heating and heating periods. During the heating period, the particle size growth of SO4(2-), NO3(-) and NH4(+) in fine mode was found, SO4(2-) and NH4(+) peaked at 3.3-4.7 microm in coarse particles. Secondary pollutions were serious during heavy pollution days with high levels of secondary ions between 1.1 and 2.1 microm. Biomass burning obviously affected the size distribution of ions during the straw burning period and ions focused on smaller than 0.65 microm, while there were more soil dusts during spring planting periods and ions concentrated in larger than 3.3 microm.

[Seasonal variation of water-soluble ions in PM2.5 at Changbai Mountain].

To study seasonal variation of water-soluble ions in PM2.5 at Changbai Mountain. PM2.5 was collected with a high-volume sampler from Jun. 2005 to Dec. 2008, and the concentrations of water-soluble ions were analyzed using ion chromatography. The results showed that the three major ions of SO4(2-), NH4+ and NO3 showed obvious seasonal variation. The mass concentration of SO4(2-) was the highest in summer and lowest in autumn. The mass concentration of NO3- was the highest in winter and lowest in summer. The seasonal variation of NH4+ was influenced by SO4(2-) and NO3-. The total concentrations of water-soluble ions in PM2.5 from different directions were evidently different, following the order of NE < NW < SW, with the average concentrations of 5.43, 7.63 and 10.26 microg x m(-3), respectively. Ca2+ was strongly correlated with CO3(2-), and the correlation(R) was higher in spring (0.74) than that in summer (0.30).

[Observation of size distribution of atmospheric OC/EC in Tangshan, China].

Atmospheric particulate matter pollution is serious in Tangshan, a heavy industrial city of North China. The annual average concentrations of PM1.1, PM2.1, PM9.0 and TSP were (75 +/- 43), (106 +/- 63), (221 +/- 100) and (272 +/- 113) microg x m(-3), respectively, from 2009 to 2011. Carbonaceous aerosols were the key components in various size particles. Elemental carbon (EC) accounted for 9%, 9%, 6% and 4% of PM1.1, PM2.1, PM9.0 and TSP, respectively, meanwhile, organic carbon (OC) accounted for 25%, 24%, 16% and 14% of PM1.1, PM2.1, PM9.0 and TSP, respectively. The concentration spectrum distribution of particulate matter and the enrichment amount of the carbonaceous aerosols showed seasonal variations. In autumn and winter, the EC and OC concentration in the fine particulate matter reached up to (9 +/- 4), (11 +/- 5) and (19 +/- 7), (28 +/- 10) microg x m(-3), respectively, accounting for 11%, 10% and 26%, 25% of fine particles; EC and OC in spring and summer were (5 +/- 2), (5 +/- 1) and (15 +/- 3), (15 +/- 1) microg x m(-3), respectively, accounting for about 7%, 6% and 26%, 18% of TSP, respectively.

[Water-soluble inorganic salts in ambient aerosol particles in Tangshan].

To investigate the levels, seasonal variation and size distributions of water soluble inorganic components, samples were collected with an Andersen cascade sampler in Tangshan from Sep. 2010 to Aug. 2011, and were analyzed by IC. The results showed that the secondary inorganic components (SO4(2-), NO3(-) and NH4(+)) were the major contributors to PM9 and PM2.1, accounting for 68% and 77% of the total water soluble salts in PM9 and PM2.1, respectively. The total concentrations of these three ions in spring, summer, autumn, and winter were 35.0, 84.7, 67.3 and 61.6 microg x m(-3) in PM9, and 23.2, 64.8, 52.7 and 49.6 microg x m(-3) in PM2.1. About 70%, 75% and 94% of SO4(2-), NO3(-) and NH4(+) were found in the fine mode of aerosol, respectively. Ca2+ and Mg2+ were unimodal and mostly concentrated in the coarse mode. Those results indicated that the pollution caused by atmospheric particles is serious in Tangshan. It is urgent to control the anthropogenic emissions sources, such as vehicle emission, coal and biomass burning. Meanwhile, it is necessary to strengthen the greening and reinforce the management of the road construction.

[Characterization of water-soluble ions in PM2.5 at Dinghu Mount].

To study the characteristics and source of aerosol in the background region of the Pearl River Delta, PM2.5 samples were collected with a high volume sampler from Jan. 2007 to Dec. 2008 at Dinghu Mountain. Water-soluble ions in PM2.5 were analyzed by ion chromatography (IC). The results showed that the annual concentrations of total water-soluble ions was (36.3 +/- 16.4) microg x m(-3) The three major ions SO4(2-), NH4(+) and NO3(-), accounted for 89% of the total water-soluble ions. The correction of Na+ and Cl- was significantly enhanced in summer by the marine air mass, and the correlation coefficient R2 was 0.91. The mean value of NO3(-)/SO(2-) was 0.32, indicating that stationary sources had more contributions to Dinghu Mountain. The range of sigma cation/ sigma anion was 0.44 - 2.59, with a mean of 1.03 in PM2.5. The charge of water-soluble ions almost achieved balance in PM2.5

[Element characteristics and sources of PM2.5 at Mount Dinghu in 2006].

To study the characteristics and sources of particles in Pearl River Delta Region, samples of PM2.5 were collected by high volume sampler, and elements of the samples were determined by ICP-MS. The results showed that concentrations of Pb, V, Cu, As, Zn and Se were 216.24, 15.40, 60.56, 31.81,432.06 and 8.12 ng x m(-3) respectively, those were in high level. Factor analysis on the chemical composition of PM2.5 showed that fuel combustion, metal-working industry, ash and sea salt were the main sources of PM2.5 in this region.

[Observation and analysis on water-soluble inorganic chemical compositions of atmospheric aerosol in Gongga Mountain].

Samples of aerosol are sampled by high volume sampler from Dec. 2005 to Nov. 2006 at high altitude of 1640 m of Gongga Mountain. Water-soluble ions in PM2.5 and PM10 are analyzed by ion chromatogram(IC). The results shows that the annual concentrations of total water-soluble inorganic ions are respectively 6.46 and 8.86 microg/m3 in PM2.5 and PM10, three major ions of SO4(2-), NO3-; and NH4+, account for respectively 82% and 85% in PM2.5 and PM10, Na+, NH4+, K+, Cl- and SO4(2-) were mostly distributed in fine particles, NO3-, Mg2+ and Ca2+ occupied each one half in coast of crude and fine particles. The correlation of Na+ and Cl- is significantly enhanced in wet season in Gongga Mountain, the correlation coefficient R2 are respectively 0.87 and 0.84 in PM2.5 and PM10. The concentration ratio of SO4(2-) and NH4+ is approximate to 1:2 in PM10, main existence form of SO4(2-) and NH4+ (NH4)2SO4 at Gongga Mountain.

[Concentrations and size distributions of water soluble ions of atmospheric aerosol at the summit of mount Tai].

In order to research on the air pollutants' long-range transportation in North China, aerosol samples were collected with Andersen cascade sampler at the summit of mount Tai during June 2006, in Shandong Province. The water soluble ionic concentrations were analyzed by IC. It shows that there are three types of size distribution: 1) ions whose mass resided mainly within the accumulation mode with the peak at 0.43-0.65 microm (SO4(2-), NH4+, K+); 2) Ions whose mass resided mainly within coarse particles with the peak at 4.7-5.8 microm (Ca2+, Mg2+); 3) Ions which were two modes with the peak at 0.43-0.65 microm and 4.7-5.8 microm (NO3-, NO3-,Cl-). The mass median diameter of SO4(2-) with high concentration is between 0.5 microm and 0.8 microm, and belongs to the "drop mode". The concentration of ions such as SO4(2-), NO3-, NH4+ and K+ has a huge variety and the sulfate has the most great variety with the lowest concentration which is 4.0 microg x m(-3) and the highest concentration which is 42.3 microg x m(-3). The ions (SO4(2-), NO3-, NH4+) reach the high value when the humid air mass comes from the south.

[On-line analysis and mass concentration characters of the alkali metal ions of PM10 in Beijing].

The mass concentration characters and the sources of water-soluble alkali metal ions in PM10 in 2004 and 2005 in Beijing were analyzed by using the system of rapid collection of particles. The result showed that the average concentration of Na+, K+, Mg2+ and Ca2+ was 0.5-1.4, 0.5-2.5, 0.1-0.5 and 0.6-5.8 microg/m3, respectively. The highest and lowest concentration appeared in different seasons for the alkali metal ions, which was related to the quality and source. The concentration of alkali metal ions was no difference between the heating period and no heating period, which meant the heating was not the main source. Sea salt and soil were the important sources of Na+. The source of K+ came from biomass burning and vegetation. Soil was the large source of Mg2+ and Ca2+. The alkali metal ions appeared different daily variation in different seasons. Precipitation could decrease the concentration of Na+, K+, Mg2+ and Ca2+, which was 10%-70%, 20%-80%, 10%-77%, 5%-80% respectively.

[Characteristics and sources of elements of atmospheric particles before and in heating period in Beijing].

In order to study the characteristics and sources of atmospheric particles before and in heating period, samples of atmospheric particles were collected in November of 2006. Concentrations of elements in particles were determined with ICP-MS. The results shows that concentrations of As, Se, Mo, Cd in heating period are more than twice of those before heating period, and there is sharp increasing of concentrations of Zn, Pb, Tl, K, Se, As, Cu, Cd, Ag in fine particles in heating period. Furthermore, Zn, Na are associated with finer particles in heating period than those before heating period. Factor analysis on the chemical composition of particles shows that contribution of combustion and biomass burning goes up and contribution of crust goes down in heating period.

[Introduction and calibration of the Chinese sun hazemeter network].

Much of the current uncertainty in the quantitative assessment of the climate and environment change is due to our lack of knowledge of the aerosol, for which the large-scale sun hazemeter ground-based network directly provides basic data. The data also can revise the results of the satellite remote sensing. Depending on the stations of CERN, the standard network was first built in China. The accurate and reliable hazemeter (LEDs) was uniformly used in the network. The hazemeters were calibrated by Langley plot method and transfer calibration and were uniformly checked. The AODs, which were synchronously retrieved from hazemeters (RSD < 3%) and CEMIL (RSD < 5%), were coherent and comparable. The stability and reliability of the hazemeters and the network was approved.