Attenuation of ultraviolet radiation reaching the surface due to atmospheric aerosols in Guangzhou

The UV attenuation due to atmospheric aerosols in Guangzhou was quantitatively assessed using surface ultraviolet radiation (UV, 295–385 nm) observation, sun photometer and radiation models. Observations showed that the annual average value of aerosol optical depth (AOD) was 1.19 in UV spectral region of 340 nm, the annual average occurrence frequency of aerosol optical depth AOD340 nm>1.0 was 55%, and the annual average attenuation rate of surface UV direct radiation of 340 nm was 68%. It was proven in the observation of surface UV radiation and model evaluation that annual average attenuation of UV due to atmosphere was 75%, and that reached 72% in the dry season (October, November, December and January); while average attenuation of UV due to atmospheric aerosols reached 62% in the dry season. It was indicated that very significant UV attenuations due to atmospheric aerosols existed in Guangzhou urban agglomeration, and at least half of UV radiation was attenuated due to atmospheric aerosols. Such large-amplitude attenuation will have a significant impact on urban ecosystem and species chemical cycles, especially photochemical reaction processes.