ABSTRACT
Online measurements of indoor and outdoor ammonia (NH3 ) were conducted at a university building in Haidian District, Beijing, to investigate their variation characteristics, indoor-outdoor differences, influencing factors, and possible contribution of indoor NH3 to atmospheric NH3 . Indoor NH3 mixing ratios varied greatly among the rooms of the same building. Indoor NH3 mixing ratio peaked at 1.43 ppm in a toilet. Both indoor and outdoor NH3 mixing ratios exhibited higher values during summer and lower values during winter and correlated significantly with relative humidity and temperature. Moreover, their daily mean mixing ratios were significantly correlated with each other. But indoor and outdoor NH3 in cold months exhibited quite different diurnal variations. During the measurement period, indoor NH3 mixing ratios were substantially higher than those outdoors, by an average factor of 3.1 (1.0-6.6). This indicates that indoor NH3 could be a source of outdoor atmospheric NH3 . The contribution of indoor NH3 to atmospheric NH3 was estimated at 0.7 ± 0.5 Gg NH3 -N·a-1 , accounting for approximately 1.0 ± 0.7% of total emissions in Beijing and being comparable to industry, biomass combustion, and soil emissions, but lower than transportation emissions. The influence of COVID-19 control measures caused indoor and outdoor NH3 mixing ratios to decrease by 22.8% and 19.3%, respectively-attributable to decreased human activity and traffic flow.
Subject(s)
Air Pollutants , Air Pollution, Indoor , COVID-19 , Air Pollutants/analysis , Air Pollution, Indoor/analysis , Environmental Monitoring , Humans , SARS-CoV-2ABSTRACT
High levels of secondary air pollutants during COVID-19 in China have aroused great concern. In Beijing, measured daily mean peroxyacetyl nitrate (PAN) concentrations reached 4 ppb over the lockdown period (24 January to 15 February), whose averages were 2-3 times that before lockdown (1-23 January). The lockdown PAN levels also reached a high historical record based on our long-term measurements (2016-2019). Unlike ozone and PM2.5, PAN formation depends on less complex photochemistry between NOx and volatile organic compounds (VOCs), providing a novel approach to investigate the wintertime photochemistry during COVID-19. The GEOS-Chem simulations suggest a markedly enhanced photochemistry by a factor of 2 during the lockdown. Change of meteorology featuring with anomalous wind convergence under higher temperatures is the main reason for enhanced photochemical formation of PAN, while chemically nonlinear feedbacks also play a role. Our results suggest implementing targeted VOC emission controls in the context of increasing photochemical pollution over this complex polluted region.
ABSTRACT
Abstract High levels of secondary air pollutants during COVID-19 in China have aroused great concern. In Beijing, measured daily mean peroxyacetyl nitrate (PAN) concentrations reached 4 ppb over the lockdown period (01/24?02/15), whose averages were 2?3 times that before lockdown (01/01?01/23). The lockdown PAN levels also reached a high historical record based on our long-term measurements (2016?2019). Unlike ozone and PM2.5, PAN formation depends on less complex photochemistry between NOx and volatile organic compounds (VOCs), providing a novel approach to investigate the wintertime photochemistry during COVID-19. The GEOS-Chem simulations suggest a markedly enhanced photochemistry by a factor of 2 during the lockdown. Change of meteorology featuring with anomalous wind convergence under higher temperatures is the main reason for enhanced photochemical formation of PAN, while chemically nonlinear feedbacks also play a role. Our results suggest implementing targeted VOC emission controls in the context of increasing photochemical pollution over this complex polluted region.