[Atmospheric Ozone Concentration Prediction in Nanjing Based on LightGBM].

Based on the air quality data and conventional meteorological data of the Nanjing Region from January 2015 to December 2016, to analyze the characteristics of O3 concentration changes in the Nanjing Region, a light gradient boosting machine (LightGBM) model was established to predict O3 concentration. The model was compared with three machine learning methods that are commonly used in air quality prediction, including support vector machine, recurrent neural network, and random forest methods, to verify its effectiveness and feasibility. Finally, the performance of the prediction model was analyzed under different meteorological conditions. The results showed that the variation in O3 concentration in Nanjing had significant seasonal differences and was affected by a combination of its pre-concentration, meteorological factors, and other air pollutant concentrations. The LightGBM model predicted the ground-level O3 concentration in the Nanjing area more precisely to a large extent (R2=0.92), and the model outperformed other models in prediction accuracy and computational efficiency. In particular, the model showed a significantly higher prediction accuracy and stability than that of other models under a high-temperature condition that was more likely prone to ozone pollution. The LightGBM model was characterized by its high prediction accuracy, good stability, satisfactory generalization ability, and short operation time, which broaden its application prospect in O3 concentration prediction.

[Vertical Distribution Characteristics of Boundary Layer Volatile Organic Compounds in Autumn in the Mixed Industrial and Rural Areas over the Northern Suburb of Nanjing].

Based on the sounding data of VOCs in the lower troposphere (0-1000 m) in the northern suburb of Nanjing in the autumn of 2020, the vertical profile distribution, diurnal variation, and photochemical reactivity of VOCs in this area were analyzed. The results showed that the volume fraction of VOCs decreased with the increase in height (72.1×10-9±28.1×10-9-56.4×10-9±24.8×10-9). Alkanes at all heights accounted for the largest proportion (68%-75%), followed by aromatics (10%-12%), halohydrocarbons (10%-11%), alkenes (3%-7%), and acetylene (2%). The diurnal variation of the boundary layer had a great influence on the VOCs profile. The lower boundary layer in the morning and evening caused the volume fraction of VOCs to accumulate near the ground and lower in the upper layer. The vertical distribution of VOCs was more uniform in the afternoon. In the morning, the volume fraction proportion of alkenes (alkanes) with strong (weak) photochemical reactivity decreased (increased) with the increase in height, indicating that the photochemical aging of VOCs in the upper layer was significant. In the afternoon, the vertical distribution of VOCs volume fraction and OFP in the lower troposphere were more uniform. Affected by the surrounding air masses with different sources, the volume fraction and component proportion of VOCs at each height were significantly different. The alkanes in rural air masses were vertically evenly distributed, and the proportion increased gradually with the height. The vertical negative gradient of VOCs volume fraction in the urban air mass was the largest, the volume fraction of VOCs near the ground was high, and it was rich in aromatics. The proportion of aromatics increased with the increase in VOCs volume fraction between 200-400 m height of industrial air mass. The near-surface VOCs volume fraction of the highway traffic air mass was high, and alkanes accounted for the largest proportion.

[Characteristics and Health Risk Assessment of BTESX in the Northern Suburbs of Nanjing].

AMA GC5000BTX was used to monitor the mixing ratio of benzene, toluene, ethylbenzene, m,p-xylene, o-xylene, and styrene (BTESX) in the atmosphere of the northern suburb of Nanjing from January 2014 to December 2016. The temporal variation characteristics of BTESX and the influence of meteorological elements on it were analyzed, and the characteristic ratio method (T/B) was used to qualitatively analyze the source of BTESX. Finally, the human exposure analysis and evaluation method of EPA was used to evaluate the health risk of BTESX. The results showed that during the observation period, the average mixing ratio of BTESX was (7.28±6.63)×10-9, and the mixing ratio of benzene was the highest at (2.45±3.91)×10-9. The mixing ratio of other species from large to small was toluene>ethylbenzene>m,p-xylene>o-xylene>styrene, which were (2.41±2.61)×10-9, (1.37±1.28)×10-9, (0.51±0.48)×10-9, (0.3±0.36)×10-9, and (0.22±0.42)×10-9, respectively. Due to the existence of stable aromatic sources, the monthly and seasonal variation in BTESX mixing ratio was not as obvious as that of other species (NOx, CO, SO2, PM2.5, etc.). The weekend effect of BTESX and other pollutants was not significant. The mixing ratio of BTESX was largely affected by the short distance transportation of chemical enterprises and traffic trunk roads in the northeast, resulting in a large mixing ratio of BTESX in the northeast. The mixing ratio of BTESX was jointly affected by relative humidity and temperature, and its high value area was mainly located in the range of 30%-70% relative humidity. In this range of relative humidity, the high value range of BTESX volume fraction increased with the elevation of temperature. The HI (hazard index) of BTESX in different seasons was within the safety range recognized by EPA, whereas the R (carcinogenic risk of benzene) value was higher than the safety threshold specified by EPA. At the same time, the HI and R values were higher in summer, to which great attention should be paid.

[Size Distribution of Particulate Chemical Components in Nanjing Jiangbei New Area].

In order to explore the pollution characteristics of the chemical components of atmospheric particulate matter in Nanjing Jiangbei New Area, size-resolved samples were collected from 2013 to 2014. The size distribution and seasonal variation of the chemical components of the particles were studied. The results showed that the total concentration of nine water-soluble ions in fine particles was higher in autumn and winter than in spring and summer, while the concentration of coarse particles was highest in winter. The ratio of NO3-/SO42- for the fine particles in winter was slightly higher than in the other three seasons, and lowest in the coarse particles. The trend of particle size distribution in spring, summer and autumn was consistent. The distribution of water-soluble ions was bimodal, and NO3- peaked at 0.65-1.1 µm in all four seasons. The peak radius of SO42- in the fine particles in summer and autumn was 0.43-0.65 µm, and the peak value in winter moved towards the coarser particles, while Na+ and Cl- mainly existed in the coarse particles. The charge equivalent of anion and anion indicated that the coarse and fine particles were alkaline and weakly alkaline, respectively. Organic carbon (OC) and elemental carbon (EC) mainly existed in the fine particles, with a bimodal distribution. The secondary organic carbon (SOC) in the fine particles in autumn and winter was significantly higher than in spring and summer. The ratio method further indicated that the carbonaceous component of the particulate matter in Nanjing Jiangbei New Area is mainly from the emissions of coal and biomass combustion, and vehicle exhaust.

[Urban Aerosol Hygroscopicity During Haze Weather].

The hygroscopicity of aerosols has an important influence on atmospheric visibility and is one of the main causes of haze pollution. Based on observations of the aerosol hygroscopic growth factor (GF), water soluble inorganic ions, and organic carbon/elemental carbon (OC/EC) data during haze weather from April 17 to May 21, in 2014, the hygroscopic properties of aerosols and corresponding effects on haze in Nanjing were analyzed. The results showed that the distribution of GF was bimodal and varied from 1.12 to 1.64. With the increase of particle size, the average hygroscopic growth factor (GFmean) changed less and the standard deviation of wettability (σ) increased gradually; meanwhile, the degree of external mixing of chemical components increased gradually. The hygroscopicity of aerosol particles in the day was better than that at night, but the mixing degree was weaker than that at night; in non-haze weather, the hygroscopicity of aerosol particles was stronger and the degree of external mixing was higher, while the hygroscopicity and mixing degree of haze particles showed opposite trends. With the increase of haze levels, the hygroscopicity of aerosol particles grew weaker and the degree of external mixing decreased further. Relative humidity can have a significant impact on the chemical components of aerosols and their hygroscopic capacity. Under a low humidity background, the main chemical components of aerosols included NH4+, NO3-, SO42-, OC, and EC, and the content of OC/EC in aerosols during haze days was more abundant; in haze weather with low relative humidity, abundant organic matter was the main reason for the decrease of the moisture absorption capacity of small-scale aerosols. The level of relative humidity in the haze weather was also an important factor affecting the hygroscopic capacity of aerosols. The contents of (NH4)2SO4, OC, and insoluble substances in aerosols were the highest, followed by NH4NO3. The contents of these chemical components showed obvious diurnal variation characteristics, which resulted in significant diurnal variation of the hygroscopicity of the aerosols. κchem calculated by the chemical composition and κmean acquired by observations using H-TDMA showed good consistency, and the correlation coefficient was 0.8903. In haze weather, the correlation between them was further enhanced. Therefore, the major chemical components of aerosols could be used to predict the hygroscopic properties of aerosols.

[Application of Support Vector Machine Regression in Ozone Forecasting].

Support vector machine regression (SVMr) was proposed to forecast hourly ozone (O3) concentrations, daily maximum O3 concentrations, and maximum 8 h moving average O3 concentrations (O3 8 h) by employing the observations of meteorological variables and O3 and its precursors during the high O3 periods from May 20 to August 15, 2016 at an industrial area in Nanjing. The squared correlation coefficient (R2) of the hourly O3 concentrations forecast was 0.84. The mean absolute error (MAE) and mean absolute percentage error (MAPE) were 3.44×10-9 and 24.48, respectively. The key factors for the hourly O3 forecast were the O3 pre-concentrations, amount of ultraviolet radiation B (UVB), and the NO2 concentration. The main factors for the O3 daily maximum forecast were the NOx concentrations at 07:00 and the UVB level. Temperature and UVB played an important role in predicting O3 8 h. In general, taking precursors into account could increase the accuracy of O3 prediction by 10%-28%. For O3 concentration forecasting, SVMr gave significantly better predictions than multiple linear regression methods.

[Source Analysis of Volatile Organic Compounds in the Nanjing Industrial Area and Evaluation of Their Contribution to Ozone].

Ambient volatile organic compounds (VOCs) were continuously measured during the high ozone (O3) periods from May 1 to May 31 and June 1 to July 16, 2015 at an industrial area in the north suburb of Nanjing. A positive matrix factorization (PMF) model and an observation-based model (OBM) were combined for the first time to investigate the contributions of VOC sources and species to local photochemical O3 formation. The average VOC concentrations in 2014 and 2015 were (36.47±33.44)×10-9 and (34.69±34.08)×10-9, respectively. The VOC sources identified by the PMF model for 2014 and 2015 belonged to 7 source categories, including vehicular emissions, liquefied petroleum gas usage, biogenic emissions, furniture manufacturing industry, chemical industry, chemical coating industry, and chemical materials industry emission sources. The OBM was modified to assess the O3 precursors' relationships. Generally, photochemical O3 production was VOC limited, with positive relative incremental reactivity (RIR) values for VOC species and a negative RIR value for NO. It can be seen that alkenes (1.20-1.79) and aromatics (1.42-1.48) presented higher RIR values and controlling O3 would be the most effective when the VOC emissions from alkenes were reduced by 80%. Vehicle emissions (1.01-1.11), LPG (0.74-0.82), biogenic emissions (0.34-0.42), and furniture manufacturing industry (0.32-0.49) sources were the top four VOC sources making significant contributions to photochemical O3 formation, which suggests that controlling vehicle emissions, biogenic emissions, LPG, and furniture manufacturing industry sources should be the most effective strategy to reduce photochemical O3 formation.

[Variation Characteristics and Health Risk Assessment of BTEX in the Atmosphere of Northern Suburb of Nanjing].

BTEX concentrations were determined by GC5000 online gas chromatography in the atmosphere of the north suburb of Nanjing in March 2013 to February 2014, using the EPA human exposure analysis evaluation method for benzene series compounds of volatile organic compounds (VOCs) in health risk assessment. The results showed that the total amount of BTEX showed the variation characteristics of spring > winter > autumn > summer. BTEX concentration was higher in the periods of 07:00-10:00 and 17:00-20:00, and the lowest was detected between 13:00-15:00; At the weekend, the concentration of BTEX was higher than on the working day. The sources of BTEX included traffic sources, industrial sources and solvent evaporation. The HQ of BTEX in all four seasons showed the order of benzene > xylene > ethylbenzene > toluene, and the HQ risk values were within the safety range in all analysis periods. The distribution of R value was winter > autumn > spring > summer, and R was higher than the safety threshold for all the analyses, indicating the existence of carcinogenic risk.

[Aerosol Chemical Characteristics for Different Air Pollution Levels in North Suburban Nanjing].

PM2.5samples were collected in a northern suburb of Nanjing during the winter of 2015. Water soluble ions and carbonaceous substances under different air quality levels were analyzed by an 850 professional IC-type ion chromatograph produced by Metrohm and a Model 2001A carbon analyzer. The results show that the average mass concentration of PM2.5, SO42-, NO3-, and NH4+ during heavy pollution days was 4.0, 6.4, 3.1, and 3.9 times higher than on clear days, respectively. Three main secondary ions were all in the form of (NH4)2SO4 and NH4NO3 on all days. Two kinds of acid pollution days were mainly affected by the flow source. The proportion of fixed sources on the heavy pollution days was greater than on the light/moderate pollution days. The highest mass concentrations of organic carbon (OC) and elemental carbon (EC) were 49.8 µg·m-3 and 10.3 µg·m-3, respectively. The average concentration of SOC on clear days was the lowest (4.28 µg·m-3). The proportion of secondary organic carbon (SOC) in the OC on clear days was more than on the other two pollution days (41.14%). Coal combustion and motor vehicle exhaust emissions were the main contributors to carbonaceous substances by abundances of carbonaceous components.

[Source Apportionment of Volatile Organic Compounds and Health Assessment of Benzene Series in Northern Suburb of Nanjing in Winter].

Volatile organic compounds (VOCs) in the atmosphere of the north suburb of Nanjing in December 2015 were determined by GC5000 online gas chromatography,and the main composition and characteristics of VOCs were analyzed by using the PMF receptor model sources of VOCs parsing.The United States Environmental Protection Agency (EPA) human exposure analysis and evaluation method in the United States were used to evaluate Human health risk of benzene series.The results showed that there were 6 sources in the PMF mode.Natural gas leakage accounted for 32.05%,automobile exhaust accounted for 18.99%,solvent use 13.67%,industrial emissions 2 13.20%,gasoline volatile 11.72%,and industrial emissions 1(chemical type)10.36%.The high value areas of the emission source were in accordance with the location of pollution sources surrounding the observation point.The B/T ratio was 0.74,which was at a relatively high level.The noncarcinogenic risk hazard quotient value HQ at 06:00 reached the highest value.HQ risk values were within the safe range specified by EPA.HQ of each source was as follows:automobile exhaust emissions 20.67×10-2,solvent use 6.97×10-2,natural gas leakage 6.34×10-2.In the carcinogenic risk of benzene,automobile exhaust emissions was 4.11×10-6,and natural gas leakage was 1.09×10-6,both were higher than the EPA specified safety threshold.

[Estimating the Secondary Organic Aerosol Concentration and Source Apportionment During the Summer and Winter in the Nanjing Industrial District].

Volatile organic compounds (VOCs) were determined by GC5000, an automatic on-line Gas Chromatography-Flame Ionization Detector. Elemental carbon (EC) and organic carbon (OC) were determined by the thermal/optical method using DRI-2001A during the periods of June 15th-July 15th 2015 and December 16th 2015-January 15th 2016. The concentration of secondary organic aerosol(SOA) was estimated by fractional aerosol coefficients (FAC) and EC tracer method. The source apportionment relied on the positive matrix factorization model (PMF). There were several conclusions:First, aromatic hydrocarbon was the main substance causing the SOA pollution in the Nanjing Industrial district, the contributions of aromatic hydrocarbon to SOA during summer and winter were 80.39% and 94.63%, respectively. The main contributers were benzene, toluene, ethylbenzene, m,p-xylene and o-xylene (BTEX). In the summer, SOA concentration ranged from 5.84-20.88 µg·m-3 with an average of 12.15 µg·m-3 and in the winter ranged from 2.17-17.73 µg·m-3 in which the average concentration was 6.91 µg·m-3. Secondly, SOA concentration decreased when wind and precipitation increased. By using the PMF model, a total of 7sources of SOA were determined in summer and 6 were determined in winter. There were 3 main sources in summer, including painting, petroleum processing and petrochemical industry, and the contributions to SOA were 0.65 µg·m-3, 0.21 µg·m-3, 0.18 µg·m-3, respectively. In winter, the most important SOA pollution was from painting, in which the contribution was 0.94 µg·m-3.

[Modeled Deposition of Fine Particles in Human Airway in Northern Suburb of Nanjing].

The particles number concentrations were determined by Wide-range Particle Spectrometer (WPS) in northern suburb of Nanjing in January and April 2015. The information of size distributions was applied in the multiple-path particle dosimetry model (MPPD) v.3.04 to quantify deposition fractions (DF) and number concentration (NC) depositions of fine particles in different regions of human airway, at different air quality levels, at rest and exercise. DF of nucleation mode and Aitken mode at rest and exercise were similar, while DF of accumulation mode at exercise was 2.49 times of that at rest. DF of nucleation mode and Aitken mode in pulmonary (PUL) was the highest, about 48.17% of total deposition fractions (TDF) at rest and 54.23% of TDF at exercise. DF of accumulation mode in head was the highest, about 41.23% of TDF at rest and 80.47% of TDF at exercise. The particle NC deposition in human airway in winter was lower than that in spring, and the total NC deposition in 3 regions was in the order of PUL > tracheobronchial(TB) > head. Compared with resting, nucleation mode deposition in PUL and accumulation mode deposition in TB and head increased at exercise. The worse the air quality, the higher the deposition growth rate of exercising to resting in head. DF difference among regions was mainly due to the different physiological parameters, while NC deposition difference was mainly due to the different particle NC in the local environment.

[Characteristic Study on the "Weekend Effect" of Atmospheric O3 in Northern Suburb of Nanjing].

The data of ozone (O3) and its precursors (NOx, CO, VOCs) observed at northern suburb of Nanjing from December 01, 2013 to November 30, 2014 were used to analyze the difference of pollutant concentrations on weekends and weekdays, and its causes. The results showed that there was an obvious "Weekend Effect" in northern suburb of Nanjing. The mass concentrations of O3 on weekdays were higher than those on weekends, whereas mass concentrations of its precursors were higher on the weekends; The average mass concentrations of O3 were 19.84 µg·m-3, 53.45 µg·m-3, 57.17 µg·m-3, and 40.43 µg·m-3 in winter, spring, summer, and autumn respectively. Compared with other seasons, "Weekend Effect " was more distinct in spring. The value of NO2/NO was 4.81% higher on weekdays (3.63) than on weekends (3.46). The longer cumulative time and higher accumulation rate of O3, and the stronger atmospheric oxidation capacity on weekdays were responsible for the higher O3 mass concentrations on weekdays. The correlation coefficients of the mass concentrations of O3 with VOCs, NOx, NO, and NO2 were higher on weekdays than on weekends.

[Contributions of Factors That Influenced the Visibility In North Suburb of Nanjing In Winter and Spring].

The data of visibility, relative humidity (RH), temperature (T), concentrations and chemical compositions of particles from January to May in 2014 were analyzed to understand the effects of meteorological elements and aerosols on the visibility in north suburb of Nanjing, research the contributions of different aerosol chemical compositions to extinction coefficients and propose the visibility fitting solutions of this region based on different parameters. As the results showed, the average visibility during the observation period was (5.78 ± 3.64) km; there were obvious negative correlations between visibility and RH, PM2.5 and the correlation coefficients were -0.66 and -0.48, respectively. The average extinction coefficient in winter was (398.72 ± 219.88) Mm⁻¹, the contributions of Organic, NH4NO3, (NH4)2SO4 and EC to extinction coefficient were 38.81%, 27.81%, 23.95% and 7.15%, respectively; and the average extinction coefficient in spring was (248.36 ± 78.42) Mm⁻¹, the contributions of Organic, NH4NO3, (NH4) 2SO4 and EC to extinction coefficient were 31.59%, 24.36%, 32.63% and 8.64%, respectively. The visibility fitting solution based on chemical compositions of aerosols was better than that based on extinction coefficient when comparing the different fitting solutions. The levels of PM2.5 mass concentrations' influences on the visibility depended on different ranges of RH; the visibility fitting solutions based on PM2.5, RH and T explained that the effects of PM2.5 on visibility were strong when RH stayed low, while RH became the more important factor with its increase.

[Distribution Characteristics of Water Soluble Ions Under Different Weather Conditions During the Youth Olympic Games in Nanjing].

To study the variation characteristics of water soluble ions during youth Olympic Games, PM2.5 and water soluble ions were observed by using the beta dust instrument, Anderson 9th sampler and IC type ion chromatography analyzer from August 6 to September 4, 2014. The observations were divided into three types of weather, sunny, rainy and cloudy. The average concentrations of PM2.5 under different weather conditions were sunny > cloudy > rainy days. The concentrations of water soluble ions in PM1.1, PM1.1-2.1 and PM2.1-10 were also sunny > cloudy > rainy days, and the obliterate of fine particles by precipitation process was more obvious. The spectra of Ca2+ and Mg2+ were bimodal. The scavenging effects of SO42- and NH4+ in range of 0.65-1.1 µm were stronger. The ratio of NO3-/SO42- under different weather conditions was less than 1, and the ratio of NO3-/SO42- in rainy and cloudy days was higher than that in sunny days. The values of SOR and NOR in the three kinds of weather conditions were more than 0.1, SO2 and NO2 had different degrees of transformation, there was more secondary pollutant in the atmosphere.

[Characteristics of Winter Atmospheric Mixing Layer Height in Beijing-Tianjin-Hebei Region and Their Relationship with the Atmospheric Pollution].

Atmospheric mixing layer height (MLH) is one of the main factors affecting the atmospheric diffusion and plays an important role in air quality assessment and distribution of the pollutants. Based on the ceilometers data, this paper has made synchronous observation on MLH in Beijing-Tianjin-Hebei region (Beijing, Tianjin, Shijiazhuang and Qinhuangdao) in heavy polluted February 2014 and analyzed the respective overall change and its regional features. Results show that in February 2014,the average of mixing layer height in Qinhuangdao is the highest, up to 865 +/- 268 m, and in Shijiazhuang is the lowest (568 +/- 207 m), Beijing's and Tianjin's are in between, 818 +/- 319 m and 834 +/- 334 m respectively; Combined with the meteorological data, we find that radiation and wind speed are main factors of the mixing layer height; The relationship between the particle concentration and mixing layer height in four sites suggests that mixing layer is less than 800 m, concentration of fine particulate matter in four sites will exceed the national standard (GB 3095-2012, 75 microg x m(-3)). During the period of observation, the proportion of days that mixing layer is less than 800 m in Beijing, Tianjin, Shijiazhuang and Qinhuangdao are 50%, 43%, 80% and 50% respectively. Shijiazhuang though nearly formation contaminant concentration is high, within the atmospheric mixed layer pollutant load is not high. Unfavorable atmospheric diffusion conditions are the main causes of heavy pollution in Shijiazhuang for a long time. The results of the study are of great significance for cognitive Beijing-Tianjin-Hebei area pollution distribution, and can provide a scientific reference for reasonable distribution of regional pollution sources.

[Size distribution and characterization of OC and EC in atmospheric aerosols during the Asian Youth Games of Nanjing, China].

Aerosol samples were collected by an Andersen cascade impactor (Andersen) in Nanjing during the Asian Youth Games (AYG), and organic carbon (OC) and elemental carbon (EC) in particles were determined by DRI Model 2001A carbon analyzer of USA. Observations indicated that OC (51.55%) and EC (54. 81%) were enriched in the fine aerosol particles with size below 1. 1 µm, the highest mass concentrations of OC and EC were located at 0-0.43 µm and 0.43-0.65 µm, respectively, accounting for 20. 90% ±5.02% and 22. 68% ±9.90% of the total concentration. The mass concentrations of OC and EC in PM1.1, PM1.1-2.1 and PM(2.1-10) during AYG period were decreased by 43. 44% -56. 17% and 59. 17% -73.55% as compared to the values before AYG. The spectral distribution of OC was bimodal during the whole observation period, while the spectrum distribution of EC was changed from bimodal to unimodal. OC and EC during the observation period were in good homology. OC and EC were attributed to automobile exhaust fumes before AYG. During AYG, OC and EC in PM1.1 were mostly from automobile exhaust fumes, while OC and EC in PM1.1-2.1 and PM2.1-10 were from automobile exhaust fumes and coal combustion.

[Pollution characteristics of organic and elemental carbon in atmospheric particles in Nanjing northern suburb in summer].

To understand organic carbon (OC) and elemental carbon (EC) mass concentration, the particles samples were collected by an Andersen cascade impactor and analyzed with the DRI analyzer in Nanjing northern suburb during May to July in 2013. The results showed that the average mass concentrations of EC and OC in PM2.1 were (2.6 +/- 1.1) microg x m(-3), (13.0 +/- 5.2) microg x m(-3) and (3.4 +/- 1.7) microg x m(-3), (20.3 +/- 7.3) microg x m(-3) in PM90, respectively. EC was mainly enriched in ultrafine particles, and OC was mainly in fine particles. The ratios of PM1.1 (EC)/PM9.0 (EC) and PM2.1 (OC)/PM9.0 (OC) were 0.62 and 0.64, respectively. The average peak of concentration of both EC and OC appeared in 0.43 microm, accounting for 33.4% of TEC and 21.1% of TOC. EC and OC in PM1.1, PM2.1 and PM9.0 had a good relation during the summer in Nanjing northern suburb, suggesting that they shared the same source. Ratios of OC and EC indicated that the main origins of carbonaceous particles were attributed to automobile exhaust fumes, coal combustion and road dust.

[Variation characteristics of surface ozone and its precursors during summertime in Nanjing northern suburb].

It is not optimistic about current air quality in Nanjing northern suburb, an area with the agglomeration of heavy industry such as steel-making and petrochemical industry. Measurement of ozone and its precursors conducted from May 18th to August 31st, with the Meteorological data recorded simultaneously, were analyzed to characterize the local photochemical pollution in summertime. The results showed that the average volume fraction of ozone (O3), nitrogen oxide (NO(x)) and volatile organic compounds (VOCs) in Nanjing northern suburb was about (32.01 ± 15.20) x 10(-9), (21.50 ± 14.02) x 10(-9) and (33.16 ± 25.20) x 10(-9), respectively, and carbon monoxide (CO) was (0.66 ± 0.44) x 10(-6). For O3, the maximum value reached 146.42 x 10(-9), exceeding the National Ambient Air Quality Standard II by a rate of 14.1%. The background level of O3, NO(x), VOCs and CO were estimated to be (5.71 ± 2.51) x 10(-9), (12.20 ± 0.36) x 10(-9), (22.44 ± 0.38) x 10(-9) and (0.28 ± 0.01) x 10(-6), respectively, from the frequency distribution of their hourly averaged volume fraction. Pollutants were significantly affected by local emission sources near the site. When affected by the southwest wind with the speed of 2-3 m x s(-1), active species of VOCs were easy to reach high level, accompanied by an increased concentration of O3; Under the influence of easterly winds, NO(x), CO and VOCs, mainly emitted from industrial sources and traffic sources, were prone to reach high level. The regulation and control measures were taken on industrial production and some vehicles during the Nanjing Asian Youth Games, but the concentration of O3 was not significantly reduced, and there were 4 days exceeding the National Ambient Air Quality Standard II.

[Distribution characteristics of pollution gases and water soluble ion in aerosol during the Asian Youth Games of Nanjing, China].

Water soluble ions were observed by an Andersen cascade impactor (Andersen) and ion chromatography in Nanjing during the Asian Youth Games (AYG), and PM2.5, NO, NO2, O3 and CO were observed by ray ß dust instrument, EMS pollution gases monitoring system. Concentrations of PM2.5, NO2, O3 and CO, were 37.0, 19.3, 48.1 and 0.7 x 10(3) µg x m(-3) during the AYG period, 26.0%, 42.6%, 36.1% and 46.1% lower than the value before the AYG period. During the AYG period, the main water-soluble ions in PM2.1 were Na(+), NH4(+) , Ca(2+) and SO4(2-), accounting for 80.6%; the main water-soluble ions in PM2.1-10 were Na(+), Ca(2+), NO3(-) and SO4(2-), accounting for 77.9%. The spectral distribution of Ca(2+), Mg(2+) and NO3(-) were bimodal during the AYG period, other ions were three models. Before and after the AYG period, all ions were three models. From NO3(-)/SO4(2-), we can judge SO2 and NO(x) mainly come from the mobile source before and after the AYG period, from stationary sources during the AYG period.