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Synthetic halogenated organic chlorofluorocarbons (CFCs) play an important role in stratospheric ozone depletion, and contribute significantly to the greenhouse effect. In this work, the mid-infrared solar spectra measured by ground-based high-resolution Fourier transform infrared spectroscopy (FTIR) were used to retrieve atmospheric CFC-11 CCl3F) and CFC-12 (CCl2F2) at Hefei, China. We implemented a new retrieval strategy, and analyzed the retrieval errors. The CFC-11 columns observed from January 2017 to December 2020 and CFC-12 columns from September 2015 to December 2020 show a similar annual decreasing trend and seasonal cycle, with an annual rate of (-0.47% ± 0.16) % yr-1 and (-0.79 ± 0.31) % yr-1, respectively. CFC-11 total columns were higher in summer, and CFC-12 total columns were higher in summer and autumn. Both of CFC-11 and CFC-12 total columns reached the lowest in spring. The annual decreasing rate of nearsurface concentration is (-0.60 ± 0.26) % y-1 for CFC-11, and (-0.81 ± 0.25) % y-1 for CFC-12. So the decline rate of CFC-11 significantly lower than that of CFC-12. Further, FTIR data were compared with the ACE-FTS satellite data, WACCM Whole Atmosphere Community Climate Model) data and the data from other NDACC (Network for the Detection of Atmospheric Composition Change) station. The mean relative difference between the vertical profiles observed by FTIR and ACE-FTS is (-5.6 ± 3.3) % and (4.8 ± 0.9) % for CFC-11 and CFC-12 for altitude from 5.5 to 17.5 km, respectively. The results demonstrate our FTIR data agree relatively well with the ACE-FTS satellite data. The annual decreasing rate of CFC-11 measured from ACE-FTS and calculated by WACCM are (-1.15 ± 0.22) % and (-1.68 ± 0.18) %, respectively. The interannual decreasing rates of atmospheric CFC-11 obtained from ACE-FTS and WACCM data are higher than that from FTIR observations. Also, the annual decreasing rate of CFC-12 from ACE-FTS and WACCM is (-0.85 ± 0.15) % and (-0.81 ± 0.05) %, respectively, close to the corresponding values from the FTIR measurements. Further, the total columns of CFC-11 observed at the Hefei site are very close to those at St. Petersburg station, with a mean difference of 3.63 × 1012 molec·cm-2, while the total columns of CFC-12 are 1.69 × 1014 molec·cm-2, slightly higher than those at St. Petersburg station. [ABSTRACT FROM AUTHOR]

Atmospheric ammonia (NH3) plays an important role in the formation of fine particulate matter, leading to severe environmental degradation and human health issues. In this work, ground-based FTIR observations are used to obtain the total columns and vertical profiles of atmospheric NH3 at a measurement site in Hefei, China, from December 2016 to November 2018. The spatial distribution and temporal variation, seasonal trend, emission sources and potential sources of NH3 are analyzed. The time series of ammonia columns show that FTIR observations captured the seasonal cycle of NH3 over the two years of measurement, with a 22.14 % yr-1 annual increase rate over the Hefei site. We used IASI satellite data to compare with the FTIR data, and the correlation coefficients (R) between the two datasets are 0.86 and 0.78 for IASI-A and IASI-B, respectively. The results demonstrate the IASI data are in broad agreement with our FTIR data. To examine the contribution of traffic to NH3 columns, we analyze the relationship of NH3 columns with CO surface concentrations. NH3 columns show high correlation (R = 0.77) with CO concentrations in summer, indicating that the elevated NH3 columns are partly caused by urban emissions from vehicles. Further, high correlation of NH3 columns with air temperature is obvious from their diurnal variation during the observation period. In addition, the clear correlation between NH3 columns and air temperature in spring and autumn over Hefei, suggests that agriculture was indeed the main source of ammonia in spring and autumn. Furthermore, the back trajectories of air masses calculated by the HYSPLIT model confirmed that agriculture was the dominant source of ammonia in spring, autumn and winter, while urban anthropogenic emissions contributed to the high level of NH3 in summer over the Hefei site. The potential source areas influencing the NH3 columns were distributed in the local area of Hefei, the northern part of Anhui province, as well as Shangdong, Jiangsu and Henan provinces. This study helps to identify the emission sources and potential sources that contribute to NH3 columns over Hefei, a highly populated and polluted area. This is the first time that ground-based FTIR remote sensing of NH3 columns and comparison with satellite data are reported in China. [ABSTRACT FROM AUTHOR]