| Ammonia(NH3)is the main alkaline gas in the atmosphere and plays an important role in the formation of fine particles(PM2.5).High concentrations of NH3 have been observed in urban areas.At present,NH3 emission in urban areas has caused widespread concern.Therefore,taking Zhengzhou as the research area,we developed a comprehensive NH3 emission inventory,and analyzed the contributions of different emission sources,spatial and temporal distribution,historical emission trend and the driving force influencing factors.And based on the passive sampling observation of ambient NH3 at different site during the four season,we discussed the NH3 concentration and its spatial and temporal variations,and the condition of NH3 rich and NH3 poor for the nitrate formation.It hopes to provide data support for the air quality improvement of Zhengzhou.First,a 2020-based emission inventory of NH3 and emission trend from 2007 to 2020 was established for Zhengzhou.The 1 km×1 km spatial gridded emission distribution was carried out by using GIS technology.Results showed the total 2020based NH3 emission was 16290.5 t in Zhengzhou.The agricultural source was the top ammonia emission source(livestock 28.5%,N fertilizer application 28.4%),followed by fugacity source(12.4%)and on-road mobile sources(10.9%).The prime contribution sub-category sources of livestock were goats,pigs and cattle.Dengfeng,Xingyang,and Xinmi were the top three counties of the total NH3 emission.NH3 emission had obvious monthly variation characteristics with the peak value in July(3403.5 t).The NH3 emission was higher in the southern and the central of western regions of Zhengzhou and lower in the northeastern region.The NH3 emissions showed a downward trend from 2007 to 2020,however,the fugacity source and on-road mobile source showed an upward trend.The trend of NH3 emissions from 1987 to 2020 were alike to the environmental Kuznets Curve,i.e.,the emission increased first and then decreased with the development of economySecond,ambient NH3 passive sampling during typical season was conducted at 3 sites from January 2021 to December 2021.Results showed that the seasonal variation of NH3 concentration was summer(28.6 μg/m3)>spring(19.8 μg/m3)>autumn(14.8μg/m3)>winter(10.0 μ g/m3).The monthly variation showed a mono-peak distribution,with the peak value in July(32.2μg/m3).The spatial variation was transportation site(24.2 μg/m3)>urban site(18.6 μg/m3)>suburban site(18.0 μg/m3).The monthly variation of NH3 concentration was consistent with temperature and NH3 emission,and opposite to particulate matter concentration and gaseous pollutant concentration.Finally,based on PM samplings and analysis of eight grade particle size,results show that the proportion of water-soluble ions was more than 60%in fine particles which was mainly concentrated in the particle size range of 0.7-1.1μm.According to the molar equivalent concentration ratio of NO3-/SO42-and NH4+/SO42-in different particle sizes and seasons,the regimes of the formation of fine particle were NH3-poor in spring and summer,while they were NH3-rich in autumn and winter.In contrast,the regimes of the formation of coarse particle were NH3-poor basically in spring,summer and autumn,while most of region were at the boundary of NH3-rich and NH3-poor in winter. |
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