[Impact of Parameterization on the Estimation of Ammonia Emissions:A Case Study over the Yangtze River Delta].

Atmospheric ammonia plays an important role in the formation of secondary inorganic composition of PM2.5, which has attracted a high level of attention from researchers both in China and abroad. Quantifying ammonia emissions is of great scientific significance regarding research on the formation of secondary aerosol, realizing better model performance, and control of ammonia emissions. Previous studies have shown that agricultural activities are the dominant source of atmospheric ammonia, of which livestock and poultry farming contribute the most. Existing studies on estimating ammonia emissions from livestock and poultry farming activities are mostly based on emission factors and activities. However, the choice of different emission activities could lead to large differences in estimated ammonia emissions. This study makes a variety of assumptions from the selection of activity levels (volume vs. inventory) and emission coefficients (monthly vs. annual average temperature), and establishes eight scenarios from which to calculate atmospheric ammonia emissions from livestock and poultry farming in the Yangtze River Delta region in 2017. The results show that selection of different activity levels has the greatest impact on estimated ammonia emissions; estimation based on volume is higher than that based on inventory by 27.6%-34.1%. Calculation based on a more detailed monthly average temperature is higher than using average annual temperature by 3000 to 4000 tons per year. In addition, the spatial and temporal distributions of the ammonia emissions are also closely related to the choice of volume vs. inventory and the choice of monthly average temperature vs. annual average temperature. When using inventory as the emission activity, Zhoushan (Zhejiang Province) has the lowest ammonia emissions, while Huainan (Anhui Province) has the highest. In contrast, when volume is used, Lishui (Zhejiang Province) has the lowest ammonia emissions and Nanjing (Jiangsu Province) has the highest. Emissions calculations based on monthly average temperature are supposed to be more representative than those based on annual average temperature, with the highest emissions from May to September and the lowest in the winter (December, January, and February).

[Regional Air Pollution Process in Winter over the Yangtze River Delta and Its Influence on Typical Northern Cities].

In this study, we analyzed several pollution episodes that occurred in the autumn and winter of 2018-2019 using multiple methods including the hierarchical clustering analysis, backward trajectory, and potential source contribution analysis based on monitored air quality and meteorological data. Bengbu, being a representative city to the north of the Yangtze River Delta (YRD) region and located in a heavily polluted area during these two pollution processes, is the focus of this work. The results indicated that the northern part of the YRD region is affected because of unfavorable meteorological conditions such as weak ground pressure, high humidity, low temperature, low wind speeds, and regional transport. The regional pollution processes over the YRD region in the autumn and winter seasons exhibit characteristics of wide influence and long duration with mainly two types of pollution:regional transport and intra-regional accumulation. During the two selected pollution episodes, the average PM2.5 concentration in the northern YRD region reached 131.6 µg·m-3 and 115.4 µg·m-3, respectively. The former type had a shorter duration but exhibited rapid accumulation of pollutants in a short period of time with greater pollution intensity, wider pollution range, and deeper pollution intrusion. Qualitative and quantitative analysis of the potential sources of PM2.5 based on PSCF and CWT showed that the PM2.5 concentration during EP1 was due to transport from cities such as Linyi, Xuzhou, Suqian, and Lianyungang to the pollution trajectory. The CWT value generally exceeded 80 with the highest value near 200. In contrast, EP2 was affected by the neighboring cities such as Suqian, Suzhou, and Xuzhou, and the CWT value was over 60 with the highest approaching 160, indicating that the interaction among cities in the study area is significant. This study shows that cross-regional air pollution control strategies are particularly important for alleviating the pollution situation in the northern part of the YRD region.

[Spatial-Temporal Distribution of Absorptive Aerosols in the Yangtze River Delta].

Based on the ozone monitoring instrument (OMI)/Aura L2 OMAERUV data from 2008 to 2017, the spatial-temporal distribution of absorptive aerosols during the past 10 years were studied. The results are as follows. ① In the temporal distribution, the inter-annual variation of absorptive aerosol optical depth (AAOD) first increased and then decreased, reaching the highest value of 0.056 in 2011; this is consistent with the aerosol optical depth (AOD) of 0.702 in the Yangtze River Delta. The inter-monthly variation shows that the high value of AAOD appeared mostly in January, March, and June and increased significantly from November to January. ② In the spatial distribution, the AAOD was higher in the north than in the south in the Yangtze River Delta, and the AOD was similar to the AAOD. High values of AAOD above 0.05 were concentrated mainly in northern Anhui and Jiangsu provinces and in Nanjing, Hangzhou, and Jinhua. The seasonal spatial distribution of AAOD and AOD was higher in spring and winter and lower in autumn, although the AOD was very high and the AAOD was low in summer. The contribution of black carbon in the Yangtze River Delta was consistent with the annual spatial distribution of the AAOD and AOD.

[Applicability of MODIS C006 Aerosol Products in a Typical Environmental Area of the Beijing-Tianjin-Hebei Region].

By fitting with the aerosol optical depth (AOD) from AERONET ground observations at sites in Beijing, Xianghe, and Xinglong with different environmental backgrounds, MODIS C051 Dark Target (DT C051), C006 Dark Target (DT C006), C006 Deep Blue (DB C006), and C006 Deep Blue/Dark Target merged AOD products were compared and evaluated to understand their applicability in the Beijing-Tianjin-Hebei region. The main conclusions are as follows:① The comparison of the C051 and C006 algorithms shows that the accuracy of the AOD at the Beijing and Xianghe sites notably improved, while an improvement was not observed at the Xinglong site; the DB C006 AOD is closest to the AERONET AOD at the Beijing site and the DT C006 AOD is closest to the AERONET AOD at the Xianghe site; the combined C006 AOD is closest to the AERONET AOD at the Xinglong site. ② The inversion error of the MODIS DT C006 at the Beijing site is caused by the improper selection of the aerosol model and surface reflectance; the inversion error of the MODIS DB C006 is mainly due to surface reflectance in spring and the aerosol model in winter. ③ Compared with the DT C051 AOD, the effective data coverage of the DT C006 is reduced, but that of DB C006 and the combined C006 increased; the combined C006 AOD data have the largest coverage. The results show that the application of the combined AOD product is best for the Beijing-Tianjin-Hebei region.

[Chemical Composition Characteristics of PM2.5 Emitted by Medium and Small Capacity Coal-fired Boilers in the Yangtze River Delta Region].

Seven small and medium coal-fired boilers were selected to analyze the emission factors and chemical composition characteristics of PM2.5, and the efficiency of the dust collection unit in removing PM2.5, OC, and EC of different particle sizes. At the outlet of the dust collection unit, PM2.5 mass emission factor was around 0.047-0.283 g·kg-1 with an average of (0.146±0.081) g·kg-1. SO42- was the most abundant ionic component, followed by NH4+ and Ca2+. S was the most abundant among all the elements, followed by Al, Ca, and Fe. The contents of OC and EC fluctuated greatly, and the ratio of OC and EC produced by each boiler was greater than one. In the range of the measured particle sizes, the mass concentration of PM2.5 showed a singlet or bimodal distribution, and the peak value appeared at 0.07-0.12 µm and greater than 1 µm in bimodal distribution. The mass concentration of OC showed a bimodal or trimodal distribution, and the peak value appeared at 0.04 µm, 0.20-0.31 µm, and greater than 1 µm in trimodal distribution. The efficiencies of the dust collection unit in removing PM2.5, OC, and EC were 66%, 53%, and 23%, respectively.

[Analysis of Aerosol Optical Depth Variation Characteristics for 10 years in Urumqi Based on MODIS_C006].

Based on the MYD04_L2_C006 dataset gained from Moderate resolution imaging spectroradiometer MODIS Level 2 at 10 km resolution of NASA's EOS (Earth Observing System) from 2006 to 2015, the aerosol optical depths (AODs) for 10 years under the condition of mild above atmospheric pollution (including mild) were analyzed for Urumqi City. The results showed that the average AODs in Urumqi were unimodally distribution over the 10 years. From January to April, the AODs gradually increased. During a year, the annual peak of 0.37±0.19 was in April, and the lowest value of 0.22±0.20 was in October. Owing to the frequent occurrence of dust weather conditions in spring, the largest seasonal variation of AOD was in spring, as the air pollution in the entire area was very serious, followed by summer and winter, with the smallest in autumn. In addition, the urban area was the high AOD value area in Urumqi, as its air pollution was more severe than that in the suburbs. The average value of AOD during the 10 years was 0.293. The highest value of AOD was 0.33 in 2006, and the lowest value of 0.24 was in 2008, which declined to 23.3% of that in 2007. The annual change in AOD in Urumqi over the 10 years rose steadily. Compared with previous studies, the lowest and highest values were both higher to different degrees. Despite the deduction trend in 2015, air pollution in Urumqi was serious in the studied decade, and thus control of such needs to be strengthened.

[Correlations of Light-duty Gasoline Vehicle Emissions Based on VMAS and CVS Measurement Systems].

Gaseous emissions from 25 State 2-5 light-duty gasoline vehicles were tested by Vehicle Mass Analysis System (VMAS) and CVS (Constant Volume Sampling) system, respectively. The correlations of emission factors of tested vehicles measured by these 2 methods were analyzed. The results showed that emission factors of light-duty gasoline vehicle had a decreasing trend with the promotion of emission standard. There were some high-emitting vehicles in the fleet of tested State 2 and State 3 vehicles, but fewer in State 4 or Stated 5 vehicle fleet. The correlations of the emission factors measured by the 2 methods deteriorated with the promotion of emission standard. The relative bias of CO and HC+NOx emission factors measured by the 2 methods reached 197% and 177%, respectively. The correlation coefficient of emission factors of higher-emitting vehicles was 0.75-0.85, while that of lower-emitting vehicles was only 0.46. If tighter emission standard of in-use light-duty gasoline vehicle was adopted, the false positive rate of measurement results by VMAS would rise significantly. In summary, VMAS method is hard to be applied in the emission measurements of light-duty gasoline vehicles with stricter emissions standard. It is necessary to conduct more studies on sophisticated in-use vehicle measurement system.

[Analysis of characteristics of black carbon concentration in Shanghai from 2008 to 2012].

The variations of black carbon (BC) mass concentration in Shanghai are analyzed and discussed by using hourly averaged data monitored continuously at Shanghai Urban Environmental Meteorological Center from January 2008 to December 2012. The results show that the annual mean mass concentration of BC decreased from (4 045.3 +/- 3 375.4) ng x m(-3) in 2008 to (2 766.2 +/- 2 078.9) ng x m(-3) in 2012, and the annual changes are 2.3%, - 6.5%, -18.7% and -12.1%, respectively. The yearly averaged BC mass concentration in Shanghai is on the low side of middle-level compared with other mega-cities of China. According to the test data,the highest monthly averaged concentration of BC appeared in November and December,which were 5 426.6 ng x m(-3) and 5 365.3 ng x m(-3), respectively,and then in January, June and October, which were 4402.5, 3763.3 and 3412.7 ng x m(-3), respectively. The diurnal cycles of the BC mass concentration show that there are two obvious peaks during morning 07:00-10:00 and during evening 18:00-22:00 Beijing time (BT), and the first peak was higher than the second on weekdays, but opposite on weekends and holidays. The daily mean mass concentration of BC was 9% higher on weekdays than on weekends and holidays. In addition, an empirical equation is obtained for daily BC concentration estimation and prediction using all the effective test data during the 5-year observation period and employing the regression analysis.

[A floating-dust case study based on the vertical distribution of aerosol optical properties].

The vertical distribution of aerosol optical properties of a typical floating-dust event on October 19, 2009 in Shanghai was analyzed by using Micro-pulse Lidar (MPL) and the CALIPSO satellite. The results showed that the floating-dust aerosol mainly existed below 2 km of height. The floating-dust aerosol backscatter coefficient ranged from 0 to 0.015 km(-1) x sr(-1), and the MPL extinction coefficient ranged from 0 to 0.32 km(-1). The MPL data showed that the aerosol extinction coefficient first increased and then decreased during the floating-dust event. At the same time, the aerosol layer was constantly lifting. The CALIPSO data showed that a large number of small particles were suspended in air at a height of below 2 km, while the big particles always stayed near the ground (0-0.5 km). At the height of 2-10 km, there was only few aerosols; in the range of 4-6 km, there was a mixture of particles with regular and irregular shapes. The vertical distribution of CALIPSO 532 nm total attenuated backscatter coefficient and MPL normalized relative backscatter signal was basically the same, but the extinction coefficient values gained by them were different. Observations by CALIPSO and MPL together could be more comprehensive and objective for monitoring floating-dust in Shanghai.

[Seasonal variations in the vertical distribution of aerosols during dry haze periods in regions around Shanghai].

Based on the onboard lidar data from CALIPSO satellite of National Aeronautics and Space Administration (NASA) from January 2007 to November 2010, the vertical distribution of optical and micro-physical properties of aerosols around Shanghai during the haze periods when relative humidity less than 80% were revealed by analyzing the parameters of 532 nm total attenuated backscatter coefficient, volume depolarization ratio and total attenuated color ratio. The results showed that during dry haze periods, the scattering ability of lower troposphere (0-2 km) was the highest and the main constituents were regular aerosols. The scattering ability of the upper troposphere (8-10 km) was the lowest and the proportion of irregular aerosols was the highest among the five altitude layers. In addition, the scattering ability of the altitude range (2-8 km) was lower than that of the lower troposphere, and the scattering ability and irregularity of aerosols at different altitude levels within the range were close to each other. Fine particle aerosols were the dominant aerosols in altitude range of 0-10 km. To be noted, the proportion of fine particles decreased with increasing altitude within the altitude range of 2-8 km. The proportion of large and irregular aerosols were higher in spring, whereas the proportion of fine and regular aerosols were higher in summer. According to the analysis of a dry haze episode on May 7th, 2007, it was found that a mass of aerosols mainly distributed within the altitude range of 0-1.5 km and partially within the altitude range of 4.0-5.5 km. The HYSPLIT model was applied to analyze the sources of aerosols in the episode, and the results indicated that the dry haze was mainly caused not only by local emissions but also by the dust aerosols transported from Mongolia, the northwest and north of China by the airflow.