[Composition Characteristics of Volatile Organic Compounds and Associated Contributions to Secondary Pollution in Shenyang Industrial Area in Summer].

Based on the observation data of volatile organic compounds (VOCs) in the industrial area of Shenyang during the summer of 2019 and 2020, the composition characteristics and sources of VOCs were preliminarily studied. The ozone formation potential (OFP) and aerosol formation potential (AFP) of VOCs were also estimated using the max incremental reactivity (MIR) and aerosol formation coefficient (FAC) methods, respectively. The results showed that the average concentration of VOCs was 41.66 µg·m-3, and the proportions of alkanes, olefins, aromatics, and acetylene were 48.50%, 14.08%, 15.37%, and 22.05%, respectively. The top ten species of VOCs were primarily C2-C5 alkanes, also including acetylene, ethylene, and some aromatics, accounting for 69.25% of the total VOCs. VOCs showed obvious diurnal variation characteristics with a high concentration in the morning and evening (at 06:00 and 22:00) and a low concentration in the afternoon (11:00-16:00). According to the value of toluene/benzene (T/B) and isopentane/n-pentane, the atmosphere of the industrial area was mainly affected by vehicle exhaust emissions, solvent use, combustion sources, and LPG/NG. The total AFP of VOCs was up to 41.43×10-2 µg·m-3, and aromatics were the largest contributor. The total OFP of VOCs reached 117.59 µg·m-3, in which the alkenes contributed the most.

[Establishment and Spatial Distribution of S/IVOCs Emission Inventory in Jiangsu Province in 2019].

The semi-/intermediate volatile organic compound (S/IVOCs) emissions inventory of Jiangsu province was established in 2019 using the activity data of various S/IVOCs emission sources, emission factors, and an estimation method. S/IVOCs emissions for each source and city in Jiangsu province were analyzed. The total amount of S/IVOCs emissions in Jiangsu province in 2019 was 637.31 Gg. Industrial sources were the major source of total S/IVOCs emissions accounting for 63.42% (404.20 Gg), followed by residential on-road mobile sources (22.23%), and off-road mobile sources accounted for the least (0.06%). Suzhou had the highest S/IVOCs emissions in 2019, accounting for 25.40% (161.86 Gg) of the total S/IVOCs emissions in Jiangsu province. The S/IVOCs emission intensity per unit area in Suzhou was the highest, reaching 18.70 t·km-2, and the emission intensity per unit GDP was the highest in Lianyungang (22.45 t·100 million yuan-1). The spatial distribution map revealed that S/IVOCs emissions in southern Jiangsu were relatively higher. The difference in the total emission of S/IVOCs, emission intensity per unit area, and emission intensity per unit of GDP were quite different among cities. The uncertainty range of S/IVOCs emissions was -88.46%-224.38% in Jiangsu province in 2019. The uncertainty range of biomass burning sources was the largest (-96.40%-277.17%).

[Elucidating the Impacts of Meteorology and Emission Changes on Concentrations of Major Air Pollutants in Major Cities in the Yangtze River Delta Region Using a Machine Learning De-weather Method].

This study applied a de-weather method based on a machine learning technique to quantify the contribution of meteorology and emission changes to air quality from 2015 to 2021 in four cities in the Yangtze River Delta Region. The results showed that the significant reductions in PM2.5, NO2, and SO2 emissions(57.2%-68.2%, 80.7%-94.6%, and 81.6%-96.1%, respectively) offset the adverse effects of meteorological conditions, resulting in lower pollutant concentrations. The meteorological contribution of maximum daily 8-h average O3(MDA8_O3) showed a stronger effect than that of others(23.5%-42.1%), and meteorological factors promoted the increase in MDA8_O3 concentrations(4.7%); however, emission changes overall resulted in a decrease in MDA8_O3 concentrations(-3.2%). NO2 and MDA8_O3 decreased more rapidly from 2019 to 2021, mainly because the emissions played a stronger role in reducing pollutant concentrations than from 2015 to 2018. However, emissions changes had weaker reduction effects on PM2.5 and SO2 from 2019 to 2021 than from 2015 to 2018. De-weather methods could effectively seperate the effects of meteorology and emission changes on pollutant trends, which helps to evaluate the real effects of emission control policies on pollutant concentrations.

[Pollution Characteristics and Sources of Water-soluble Organic Nitrogen in PM2.5 in Jiangbei New Area, Nanjing].

The seasonal variation characteristics of water-soluble organic nitrogen (WSON) in PM2.5 were analyzed in the Nanjing Jiangbei new area. The relationship between WSON and water-soluble inorganic nitrogen (WSIN) was also discussed. The results showed that the variation range of WSON in PM2.5 was 0.446 to 4.200 µg·m-3, with an average value of 2.04 µg·m-3. This value was slightly higher than the observed results in Beijing, Shanghai, and Changzhou. The average value of WSON was the highest in autumn[(2.967±0.643) µg·m-3], which was approximately 1.7 times that of the other three seasons. The average contribution ratio of WSON to water-soluble total nitrogen (WSTN) in fine particles of Nanjing accounted for 25%, with high ratios in summer-autumn and low ratios in winter-spring. For example, the proportion of WSON/WSTN in winter was only approximately 50% of that in summer and autumn. WSON had the highest correlation with NO2--N and the lowest correlation with NO3--N in WSIN, which may be related to the volatilization of NO3--N caused by high temperatures in summer. Principal component analysis (PCA) showed that WSON of PM2.5 in Nanjing was mainly derived from secondary transformation, sea salt, dust, and biomass combustion.

[Deposition Characteristics of Water-soluble Inorganic Nitrogen and Organic Nitrogen in Atmospheric Precipitation in the Northern Suburbs of Nanjing].

Based on atmospheric precipitation collected in the northern suburbs of Nanjing from 2019 to 2020, the pH, conductivity, and chemical components of precipitation were analyzed. The seasonal variation in pH and conductivity of atmospheric precipitation in the northern suburbs of Nanjing were studied. The pollution levels and deposition characteristics of water-soluble inorganic nitrogen (WSIN) and organic nitrogen (WSON) in precipitation were also analyzed. The frequency of acid rain (pH<5.6) in atmospheric precipitation in the northern suburbs of Nanjing reached 37.18% during the observation period. Precipitation acidification was more serious in autumn and winter, and the pH value showed a variation trend of spring>summer>autumn>winter. The average conductivity of precipitation was 29.49 µS·cm-1; high pH and conductivity in spring were related to the high dust content in the atmosphere. The seasonal difference between WSIN and WSON in precipitation was significant. The highest and lowest concentrations of NO3--N and NH4+-N appeared in spring and summer, respectively. The concentration of WSON was the highest in autumn (2.63 mg·L-1). The average concentration ratio of WSON to water-soluble total nitrogen (WSTN) in precipitation was approximately 0.47, indicating that WSON played an important role in the study of total nitrogen. The average wet deposition fluxes of WSIN and WSON were 12.10 kg·(hm2·a)-1 and 11.13 kg·(hm2·a)-1, respectively, in which the inorganic nitrogen deposition was mainly NH4+-N.

[Pollution Characteristics and Ozone Formation Potential of Ambient VOCs in Different Functional Zones of Shenyang, China].

Ambient volatile organic compounds(VOCs) were determined by GC 5000 online gas chromatography in three functional areas of Shenyang, namely industrial, traffic, and mixed cultural and educational areas. The pollution characteristics of VOCs in these functional areas during the heating and non-heating periods were analyzed, and the ozone formation potential(OFP) was estimated by using maximum incremental reactivity(MIR). The results show that the average mass concentration of VOCs is(82.19±54.99) µg·m-3 in Shenyang, of which the concentration in industrial areas is significantly higher than that in traffic and cultural and educational mixed areas, and the heating period is higher. The traffic and mixed cultural and educational areas have bi-modal characteristics due to the morning and evening traffic, and the industrial area has multiple peaks affected by the irregular operation hours. The proportion of VOCs in traffic and mixed cultural and educational areas shows the order of alkanes>aromatic hydrocarbons>alkenes>alkynes, but the proportion of alkynes in industrial areas is higher than that of alkenes. The benzene to toluene(B/T) and ethane to acetylene(E/A) ratios reflects that traffic and mixed cultural and educational areas were affected by both vehicle exhaust emissions and fuel combustion. The industrial zone is therefore affected by complex sources, and there are more aged air masses during the heating period than non-heating period. The average OFP contribution of atmospheric VOCs in Shenyang is 232.89 µg·m-3. The contribution of alkenes is largest for all functional areas, and the aromatic component also contributes more due to the high concentration of industrial areas.

[Characteristics and Sources of Water-soluble Ion Pollution in PM2.5 in Winter in Shenyang].

In order to explore the characteristics of PM2.5 and water-soluble ions in Shenyang in winter, the URG-9000D online monitoring system was used to continuously sample PM2.5 and gas components during 2018. The results indicated that the average concentration of PM2.5 in Shenyang during the sampling period was 80.67 µg·m-3, and the total water-soluble ion concentration ranged from 2.68 to 132.79 µg·m-3. Compared with clean days, the proportion of NO3-, SO42-, and NH4+ (SNA) in polluted days increased significantly, reached 43.7% of PM2.5. The rapid accumulation of SO2 in a short period of time made atmospheric PM2.5 explosively increase in Shenyang in winter. A Pearson correlation analysis showed that the correlation coefficients of SNA, Cl-, and PM2.5 were all above 0.78, indicating that the main contribution components of winter PM2.5 in Shenyang were SNA and Cl-. The apportionment of PMF sources indicated that the sources of pollutants in winter in Shenyang mainly included secondary reaction sources, coal and biomass combustion sources, and dust sources.

[Spatio-Temporal Distribution and Variation Characteristics of Aerosol Optical Properties in Henan Province].

The temporal variation and spatial distribution characteristics of aerosol optical depth (AOD), aerosol column mass concentration (AMC), and fine mode fraction (FMF) were analyzed based on the aerosol product information obtained from MODIS/Terra C6.1 from 2001 to 2018 in the Henan province. The spatial distribution of AOD and AMC in all seasons are high in the east and low in the west, and high in the north and low in the south, which was related to the special topography, population distribution, and number of enterprises in each region. Meanwhile, the spatial distribution of FMF is opposite to that of AOD and AMC. In spring, AMC was the highest, while FMF was the lowest, indicating that it was mainly affected by dust aerosol in spring. AOD and FMF were the highest in summer, while the AMC was lower, mainly because the high values of AOD in summer were caused by the hygroscopic growth of aerosol. The increase of rainwater scouring and secondary aerosol generation led to the domination of fine-mode aerosols in summer. In autumn and winter, the AOD and AMC were relatively low, and the FMF was slightly higher than in spring. The AOD and AMC in the Henan Province showed a decreasing annual trend, while the FMF exhibited an increasing trend. The average monthly peak-valley difference of AOD, AMC, and FMF decreased after 2011.

[Pollution and Deposition Characteristics of Precipitation and Its Source Apportionment in Xi'an City].

Chemical and deposition characteristics as well as potential sources of precipitation in Xi'an from 2000 to 2017 were analyzed based on the acid deposition monitoring network in East Asia (EANET). The pH of precipitation showed increasing trends, whereas the conductivity of precipitation showed decreasing trends between 2000 and 2017 in Xi'an. The decreasing order of ion concentration in precipitation was as follows:SO42- > Ca2+ > NH4+ > NO3- > Na+ > Cl- > Mg2+ > K+. The percentage of SO42- in the total ion concentration decreased from 38.6% in 2000 to 27.9% in 2017. The ratio of SO42- to NO3- in recent years indicated that the type of pollutant in Xi'an changed from the coal-burning type to the mixed type. The deposition of SO42- in precipitation had a declining trend, which was consistent with the results of the Mann-Kendall test. Nitrogen and sulphur depositions in precipitation were 16.89 kg·(hm2·a)-1 and 33.52 kg·(hm2·a)-1, respectively, and ammonium nitrogen (NH4+-N) was the main deposition component of atmospheric active nitrogen in the precipitation of Xi'an. Vehicle emissions were the major contributors to SO42- (15.43%) and NO3- (72.99%). NH4+ originated mainly from agriculture sources, and the percentage reached up to 75.47%.

[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.

[Establishment and Spatial Distribution of Anthropogenic Ammonia Emission Inventory in Zhejiang Province].

The ammonia emissions inventory of Zhejiang Province was established in 2017 using the activity data of various ammonia emission sources, emission factors, and an estimation method. Ammonia emissions for each source and city in Zhejiang Province were analyzed. The spatial distribution and intensity of ammonia emissions in 2017 were mapped using ArcGIS software. The total anthropogenic ammonia emissions in Zhejiang Province in 2017 were 122.00 kt. The farmland ecosystem was the major source of total ammonia emissions (36.06 kt), and nitrogen fertilizer applications was the largest contributor in this category (87.12%), followed by the livestock and poultry source (29.44%). The waste and human-activity sources were the two major non-agricultural sources, accounting for 44.07% and 28.49%, respectively. Hangzhou City had the highest ammonia emissions in 2017, accounting for 17.83% of the total ammonia emissions in Zhejiang Province. However, the ammonia emission intensity in Jiaxing City was the highest, reaching 3.82 t ·km-2. The spatial distribution map revealed that ammonia emissions in the northern and southeastern Zhejiang were relatively higher, while ammonia emission intensity was higher in the northern and northeastern region.

[Diurnal Variations and Source Apportionment of Water-soluble Ions in PM2.5During Winter in Nanjing Jiangbei New Area].

To gain a better understanding of the day-night variation characteristics of water-soluble ions, PM2.5 samples were continuously collected for two months in the Nanjing Jiangbei New Area during winter. The diurnal variation and sources of water-soluble ions were studied. Results showed that the mass concentration of water-soluble ions ranged from 17.07 µg·m-3 to 168.43 µg·m-3 with a mean value of (59.01±30.75) µg·m-3. The average mass concentration of water-soluble ions in daytime was higher than that in the nighttime. The concentration ratio of NO3- and NH4+ to total ion concentrations was higher at night, while SO42- and Cl- were higher during daytime. SO42-, NO3-, and NH4+ (SNA) were the dominant species of water-soluble ions in PM2.5 in Nanjing. The mass concentration of SNA on polluted days was higher than that on clean days. The ratio of the anion-cation balance (AE/CE) was larger than 1, indicating that the PM2.5 was acidic. There was a significant linear correlation between NH4+ with NO3- and SO42-, indicating that it occurred mainly in the form of NH4NO3 and (NH4)2SO4 in PM2.5. The PMF source apportionment indicated that water-soluble ions of PM2.5 were mainly derived from motor vehicle emissions, fossil fuel combustion, biomass burning, and dust in the Nanjing Jiangbei New Area.

[Source Apportionment and Mixing State of Single Particles in the Nanjing Jiangbei New Area].

To characterize the ambient particles in the Nanjing Jiangbei New Area, a single particle aerosol mass spectrometer (SPAMS) was deployed from December 1 to 31, 2015. A total of 7.478 million particles were analyzed with both positive and negative ion spectra. The air quality of Nanjing during the measurement period was poor, and the percentage of pollution days was 49.2%. The correlation (R) between the SPAMS particle number and PM2.5 concentration was 0.83, showing that the particle number could reflect the trend in the variation of atmospheric pollution. The dominant pollutant source at the monitoring site was coal combustion, followed by vehicle emissions and industrial emissions, with a contribution ratio of 63.5%. The increase in the PM2.5 mass concentration was accompanied by a high proportion of coal combustion or vehicle emissions. A high mixing state between EC, ECOC, and OC and NO2-, NO3-, and SO4- was observed for the sources of biomass burning, dust, vehicle emissions, coal combustion, and industrial emissions.

[Establishment and Characteristics of an Artificial Ammonia Emissions Inventory in Jiangsu Province from 2013 to 2017].

According to activity level data of various ammonia emission sources in Jiangsu Province, using a reasonable inventory calculation method and emission factor, an ammonia emission inventory in Jiangsu Province from 2013 to 2017 was established, and the trend of anthropogenic ammonia emissions over these years was analyzed. The distribution characteristics of anthropogenic ammonia emissions and emission intensity in Jiangsu Province were analyzed using ArcGIS software. The results showed that the ammonia emissions in Jiangsu Province decreased from 624.84 kt in 2013 to 562.47 kt in 2017 with an average annual rate of decline of approximately 2.6%. Agricultural has always been the most important source of ammonia emissions in Jiangsu Province and accounted for 82.4% of the total ammonia emissions in 2017. Laying hens are the largest source of ammonia emissions from livestock and poultry sources, accounting for 49.3% of the ammonia emissions from livestock and poultry. The average ammonia emission intensity in Jiangsu Province was 5.3 t·km-2 in 2017. Yancheng and Xuzhou are two cities with the largest anthropogenic ammonia emissions and emission intensity in Jiangsu Province. Zhenjiang City has the lowest ammonia emission and emission intensity.

[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.

[Important Effect of Secondary Inorganic Salt Extinction on Visibility Impairment in the Northern Suburb of Nanjing].

Observed data regarding the visibility and aerosol chemical composition from May 2013 to May 2014 were used to analyze the variation of visibility, the relationship between aerosol chemical composition and visibility variations, and their contributions to atmospheric light extinction. An important effect of secondary inorganic salt extinction on the visibility impairment was determined. The present study suggests that the average visibility during the observation period was (6.78±3.68) km, and there was obvious seasonal variation in the visibility. Fine particles with size less than 2.1 µm have a great influence on visibility, with the main chemical components of SO42-, NO3-, NH4+, and OC. The secondary inorganic ions make significant contributions to visibility degradation. The mean light extinction coefficient of Nanjing was (527.2±295.2) Mm-1, which was calculated by using the revised IMPROVE equation. Regarding the chemical composition of PM2.1, the most contributive species to the light extinction coefficient were ammonium sulfate, ammonium nitrate, and organic species, which accounted for 80.6%. Although the light extinction contribution of organic matter was as high as 43.51% on a clear day (VR>10 km), with the decrease of visibility, the extinction contribution of organic matter decreased, but the contribution of secondary inorganic salt increased. The contribution of extinction was 58.96% for heavy haze days with low visibility (VR<5 km). This proves that the secondary inorganic salt extinction plays a significant role in visibility impairment.

[Source Apportionment of Black Carbon Aerosol in the North Suburb of Nanjing].

Based on one year real-time measurements from a seven-wavelength Aethalometer combined with an Aethalometer model, the measured aerosol absorption coefficients at different wavelengths have been used to apportion the contribution of fossil fuel and biomass burning sources to the total black carbon (BC) mass concentration in the north suburb of Nanjing. Good consistency in the relationship between the Angstrom absorption exponent(α)and the ratio of BC from biomass burning sources to total BC (BB) was obtained during this period. The α was highest in winter and lowest in summer, which indicates the change in the source of the absorbing aerosols and their relative source strength. The BC and the BC from fossil fuel (BCff) and biomass burning (BCbb) mass concentrations exhibit significant diurnal variation, with higher values during 07:00 to 09:00 (local time) and 18:00 to 21:00. The BCff was three to five times higher than the BCbb and contributes greatest to the BC mass concentrations throughout the day. Night time BC values were about a factor of 1.2 higher than day time BC values. Meanwhile, the concentration weighted trajectory (CWT) analysis indicates that the highest value of BC was concentrated in the Zhejiang, Anhui, Jiangxi, and Fujian provinces.

[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.

[Characteristics of Black Carbon Aerosol and Influencing Factors in Northern Suburbs of Nanjing].

Based on the hourly averaged data of black carbon(BC) aerosol, PM2.5, gaseous pollutants, and meteorological data in the northern suburb of Nanjing from January to October 2015, characteristics and influencing factors of BC concentration variation were analyzed. The mean concentration of BC was found to be (2524±1754) ng·m-3 during the observation period. BC concentrations in Nanjing showed strong seasonality, the highest mean concentration of BC occurred during winter reaching (3468±2455) ng·m-3, and the lowest mean BC concentration was found during spring being (2142±1240) ng·m-3; a distinct diurnal variation of BC with two high peaks occurred, one in the morning during 07:00 to 08:00 and the other in late evening during 21:00 to 22:00 local time. The strong correlation between BC and NOx indicated a greater impact of vehicle emissions on BC concentration, while a lower rate of ΔBC/ΔCO was found in the northern suburb of Nanjing, suggesting that biomass burning emission might be another important source of BC in here. BC concentration increased with decreasing wind speed. BC concentration lower than 2000 ng·m-3 mainly occurred in westerly wind and adjacent wind in all seasons, whereas BC concentration higher than 6000 ng·m-3 more frequently appeared in easterly winds in autumn and winter. BC concentration was higher in hazy and heavy hazy weather, which were 2 and 2.3 times as large as that in non-hazy weather, respectively.

[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.