An unexpected catalyst dominates formation and radiative forcing of regional haze
| Autor: | Yele Sun, Mario J. Molina, Chao Liu, Jianfei Peng, Jiayun Zhao, Xiaochun Zhang, Annie L. Zhang, Gen Zhang, Yixin Li, Gehui Wang, Renyi Zhang, Fang Zhang, Xinlei Ge, Yuan Wang, Yuepeng Pan, Yuemeng Ji, Lian Duan, Min Hu, Lu Chen, Yuesi Wang |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Multidisciplinary
Haze 010504 meteorology & atmospheric sciences Air stagnation Global warming air pollution 010501 environmental sciences Radiative forcing Atmospheric sciences black carbon Corrections 01 natural sciences haze Atmosphere Atmospheric radiative transfer codes Earth Atmospheric and Planetary Sciences Greenhouse gas Physical Sciences Radiative transfer multiphase chemistry climate 0105 earth and related environmental sciences |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America Proceedings of the National Academy of Sciences of the United States of America, vol 117, iss 8 |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Significance Regional haze adversely affects human health and possibly counteracts global warming by greenhouse gases, but its formation and radiative forcing remain unclear. Here we present field measurements to show reduced frequency but not severity for heavy haze and little-improved moderate haze, when SO2 is significantly reduced in China. Our laboratory experiments identify black carbon (BC)-catalyzed sulfate formation involving NO2 and NH3. Radiative transfer calculations accounting for this BC chemistry indicate small net climatic cooling/warming but large surface cooling, atmospheric heating, and air stagnation. Our work reveals that this BC catalytic chemistry dominates the formation, trend, and radiative forcing of regional haze, suggesting the necessity of simultaneous reduction in emissions of SO2, NOx, NH3, and BC for air-quality improvement. Although regional haze adversely affects human health and possibly counteracts global warming from increasing levels of greenhouse gases, the formation and radiative forcing of regional haze on climate remain uncertain. By combining field measurements, laboratory experiments, and model simulations, we show a remarkable role of black carbon (BC) particles in driving the formation and trend of regional haze. Our analysis of long-term measurements in China indicates declined frequency of heavy haze events along with significantly reduced SO2, but negligibly alleviated haze severity. Also, no improving trend exists for moderate haze events. Our complementary laboratory experiments demonstrate that SO2 oxidation is efficiently catalyzed on BC particles in the presence of NO2 and NH3, even at low SO2 and intermediate relative humidity levels. Inclusion of the BC reaction accounts for about 90–100% and 30–50% of the sulfate production during moderate and heavy haze events, respectively. Calculations using a radiative transfer model and accounting for the sulfate formation on BC yield an invariant radiative forcing of nearly zero W m−2 on the top of the atmosphere throughout haze development, indicating small net climatic cooling/warming but large surface cooling, atmospheric heating, and air stagnation. This BC catalytic chemistry facilitates haze development and explains the observed trends of regional haze in China. Our results imply that reduction of SO2 alone is insufficient in mitigating haze occurrence and highlight the necessity of accurate representation of the BC chemical and radiative properties in predicting the formation and assessing the impacts of regional haze. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|