[Temporal Evolution and Source Appointment of Black Carbon Aerosol in Ordos During Summer and Autumn 2019].

In this study, black carbon (BC) aerosols were continuously observed using a seven-channel aethalometer (AE-33) in Ordos from August 12 to October 4, 2019; using this data combined with article matter (PM), pollutant gas, and meteorological element data; a HYSPLIT model; and potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models, we analyzed the temporal evolution and potential source appointment and main influence areas of BC. The results showed that the average of ρ(BC) was 882 ng·m-3, accounting for 6.08% of PM2.5. The ρ(BC) was mainly concentrated at 200-1000 ng·m-3, accounting for 55.9% of the total samples. In different BC mass concentration ranges, BCliquid was the mainstay, with an average proportion of 86%. The diurnal variations in BC and PM2.5 showed unimodal distributions, with peaks at 08:00 and 10:00, respectively, and peak concentrations increased by 24.3% and 47.2%, respectively. The diurnal variation in BCsolid showed a bimodal distribution, with peaks at 08:00 and 20:00, respectively. The diurnal variation in the BCliquid showed a unimodal distribution with a peak at 08:00. The strong correlation between BC and NO2 indicated a greater impact of vehicle emissions on BC concentration, whereas the weak correlation between BC and SO2 indicated a lower impact of industrial emissions on BC concentration. The dominant air masses affecting the Ordos could be divided into four categories. The southern air masses (35.6%) had the highest mass concentration of atmospheric pollutants, followed by the local air masses (26.9%) and the northwest air masses (18.8%), and the northeast air masses (18.7%) had the lowest mass concentration of pollutants. The influence of the Ordos on the downstream areas was mainly divided into the northeast air masses (40.9%), the northwest air masses (30.4%), and the southeast air masses (28.7%). High CWT value areas of BC were mainly located in the southern Yan'an-Tongchuan-Baoji-Hanzhong areas and Lvliang-Linfen-Sanmenxia-Nanyang areas. They were two long and narrow transmission belts with a weight mass concentration exceeding 1400 ng·m-3. High CWT value areas of BC had the greatest impact on the Wuhai-Bayannaoer-Baotou-Hohhot regions, with a weight concentration exceeding 900 ng·m-3. The long-range transportation of BC could reach the Yulin-Yan'an-Tongchuan-Baoji areas in the south, the Shuozhou-Datong-Beijing areas in the east, and the Xilin Gol League-Xing'an League-Hulunbuir areas in the northeast.

[Factors Influencing New Atmospheric Particle Formation in Ordos During Summer and Autumn 2019].

In this study, the aerosol number size distribution in the range of 10 nm-10 µm was collected from August 16 to October 04, 2019 at Ordos using a wide-range particle spectrometer (WPS). Combined with PM (PM2.5 and PM10), pollution gases, meteorological data, and the HYSPLIT model, the characteristics and impact factors of new particle formation (NPF) were discussed. The results indicated that there were 19 NPF events during the observation period, which have different effects on diurnal variation in aerosol number concentration in different modes. The NPF events caused a sharp increase in the number concentration of nucleation and Aitken mode aerosols, but had little effect on the number concentration of accumulation and coarse mode aerosols. The temperature, wind speed, and total solar radiation during NPF days were usually higher than those in non-NPF days, and the RH during NPF days was lower. On NPF days, the mass concentrations of PM2.5, PM10, CO, and NO2 were lower than those on non-NPF days, while the mass concentrations of O3 and SO2 were higher. NPF events were observed in 40.0% of northern air masses and 29.6% of southern air masses. There were significant differences in meteorological elements in different NPF event air mass types. The southern NPF event air mass type had the lowest wind speed and the highest RH, with averages of (2.4±1.5) m·s-1 and (48.8±10.8)%, respectively. The northern NPF event air mass type had the highest wind speed and total solar radiation, with averages of (4.2±1.9) m·s-1 and (664.5±255.6) W·m-2, respectively. The western air mass type of NPF event had the lowest RH, with an average of (29.8±12.7)%. The formation rates of new particles in the different air mass types of NPF events were similar, ranging from 1.5 to 1.8 cm-3·s-1. The largest growth rate was (12.7±13.6) nm·h-1 in the southern NPF event air mass type, which was 1.2 times and 1.4 times higher than the NPF events of northern air masses and western air masses.