The impact of Brown Carbon (BrC) to aerosol light absorption has been paid more attention recently and there are a large number of studies showing that the influence of BrC on radiative forcing should not be ignored.B...The impact of Brown Carbon (BrC) to aerosol light absorption has been paid more attention recently and there are a large number of studies showing that the influence of BrC on radiative forcing should not be ignored.BrC also acts as an important component of haze pollution which is occurring frequently in Wuhan,China.Therefore,it is essential to estimate their optical properties,composition,and mass concentration.Considering most haze pollution happens during the coldest time,we retrieved BrC columnar content during winter in Wuhan for the first time.Our method bases on the fact that BrC showed the strong spectral dependence on UV-light absorption.Using this method,we found that BrC makes up the small proportions of total aerosol volume (less than 10％).In the winter of 2011,we retrieved the daily-averaged columnar-integrated mass concentration of BrC on clear day is 4.353 mg/m2 while that of haze day is 12.750 mg/m2.According to the sensitivity study,we found that the results highly relied on the assumed aerosol refractive index.To reduce the uncertainty of this approach,we need to gain a better understanding of the temporal variability of the radiation absorbing components of these aerosols in the future.展开更多
Characteristics of atmospheric carbonaceous aerosols in Lanzhou City from December 2014 to November 2015 are analyzed using a multiwavelength thermal/optical carbon analyzer. Results reveal that average concentrations...Characteristics of atmospheric carbonaceous aerosols in Lanzhou City from December 2014 to November 2015 are analyzed using a multiwavelength thermal/optical carbon analyzer. Results reveal that average concentrations of black carbon (BC) and organic carbon in atmospheric aerosols at Lanzhou are 6.7 and 25.4 μg m^(-3), respectively, showing obvious seasonality (higher in winter and lower in summer). This is consistent with findings in cities of northern China. Primary organic aerosols and secondary organic aerosols respectively account for approximately 60% and 17% of carbonaceous aerosols. No significant seasonality is found for secondary organic carbon, indicating that its potential sources do not vary significantly throughout the study period. The mass absorption cross-section (MAC_(632nm)) of BC is 7.1 m^2g^(-1), slightly higher than that of immediately emitted BC. MAC values of BC at different wavelengths vary drastically; they are higher for ultraviolet and visible light (8.5–10.2 m^2g^(-1)) than for near-infrared light (4.9–5.7 m^2g^(-1)). The aerosol absorption optical depth generally declines from the near-infrared to the near-ultraviolet region. The values are higher in winter than in summer, thus showing there are different contributions of BC deposition in different seasons. Brown carbon (BrC) has an ?ngstr?m absorption exponent (AAE) value of approximately 2.75, which is similar to the AAE value of BrC generated by diesel combustion (2.3). The contribution of BrC to light absorption is as much as 34% at a wavelength of 635 nm. This study demonstrates that the multiwavelength thermal/optical carbon analyzer can quantify absorption properties of BrC in atmospheric aerosols. This can enhance understanding of carbonaceous aerosols and provide key parameters for simulations of climate models.展开更多
基金This work was financially supported by National Natural Science Foundation of China [grant number 41627804,41401498,and 41601044],the National Key Research and Development Program of China [grant number 2017YFC0212600] and Natural Science Foundation of Hubei Province (grant number 2017CFB404)
文摘The impact of Brown Carbon (BrC) to aerosol light absorption has been paid more attention recently and there are a large number of studies showing that the influence of BrC on radiative forcing should not be ignored.BrC also acts as an important component of haze pollution which is occurring frequently in Wuhan,China.Therefore,it is essential to estimate their optical properties,composition,and mass concentration.Considering most haze pollution happens during the coldest time,we retrieved BrC columnar content during winter in Wuhan for the first time.Our method bases on the fact that BrC showed the strong spectral dependence on UV-light absorption.Using this method,we found that BrC makes up the small proportions of total aerosol volume (less than 10％).In the winter of 2011,we retrieved the daily-averaged columnar-integrated mass concentration of BrC on clear day is 4.353 mg/m2 while that of haze day is 12.750 mg/m2.According to the sensitivity study,we found that the results highly relied on the assumed aerosol refractive index.To reduce the uncertainty of this approach,we need to gain a better understanding of the temporal variability of the radiation absorbing components of these aerosols in the future.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41671067, 41630754)the Key Research Program of Frontier Sciences CAS (Grant No. QYZDJSSW-DQC039)+1 种基金the State Key Laboratory of Cryospheric Sciences, Chinese Academy of Sciences (Grant No. SKLCS-ZZ-2018)the Youth Talents Project of Northwest Institute of Environmental Resources, Chinese Academy of Sciences, China Scholarship Council Project
文摘Characteristics of atmospheric carbonaceous aerosols in Lanzhou City from December 2014 to November 2015 are analyzed using a multiwavelength thermal/optical carbon analyzer. Results reveal that average concentrations of black carbon (BC) and organic carbon in atmospheric aerosols at Lanzhou are 6.7 and 25.4 μg m^(-3), respectively, showing obvious seasonality (higher in winter and lower in summer). This is consistent with findings in cities of northern China. Primary organic aerosols and secondary organic aerosols respectively account for approximately 60% and 17% of carbonaceous aerosols. No significant seasonality is found for secondary organic carbon, indicating that its potential sources do not vary significantly throughout the study period. The mass absorption cross-section (MAC_(632nm)) of BC is 7.1 m^2g^(-1), slightly higher than that of immediately emitted BC. MAC values of BC at different wavelengths vary drastically; they are higher for ultraviolet and visible light (8.5–10.2 m^2g^(-1)) than for near-infrared light (4.9–5.7 m^2g^(-1)). The aerosol absorption optical depth generally declines from the near-infrared to the near-ultraviolet region. The values are higher in winter than in summer, thus showing there are different contributions of BC deposition in different seasons. Brown carbon (BrC) has an ?ngstr?m absorption exponent (AAE) value of approximately 2.75, which is similar to the AAE value of BrC generated by diesel combustion (2.3). The contribution of BrC to light absorption is as much as 34% at a wavelength of 635 nm. This study demonstrates that the multiwavelength thermal/optical carbon analyzer can quantify absorption properties of BrC in atmospheric aerosols. This can enhance understanding of carbonaceous aerosols and provide key parameters for simulations of climate models.
