| NH3 is an important alkaline gas in the atmosphere.The increasing concentration of the near-surface NH3has brought many environmental and ecological problems.A comprehensive understanding of the temporal and spatial characteristics of near-surface NH3 concentration in the world,especially in China,and analysis of factors related to near-surface NH3 concentration changes can provide scientific basis and data support for clarifying NH3 emission laws,compiling NH3 emission inventories,and controlling NH3 pollution.In this paper,the near-surface NH3 concentration of the world was estimated using the data of the NH3 column from the Infrared Atmospheric Sounder Interferometer(IASI)and the GEOS-Chem model.The results were verified by ground station observation data,and spatiotemporal variations of near-surface NH3concentrations in China and the world from 2010 to 2019 were presented by using spatial statistics and time series trend analysis methods.On this basis,the correlation analysis method was used to quantitatively analyze the correlations between land cover types,population density,GDP,NH3 emissions,meteorological factors(surface temperature,precipitation,wind speed,air relative humidity)and the dynamic changes of near-surface NH3 concentration in China.The main findings are as follows:(1)The near-surface NH3 concentration estimated by combining the IASI NH3column concentration data and the GEOS-Chem model data can generally reflect the actual near-surface NH3 concentration value and spatial distribution.(2)The high value of near-surface NH3 concentration is mainly distributed in the areas with frequent human activities,forming the feature of non-point source distribution with agricultural intensification as the center and point source distribution with densely populated cities as the center.(3)During 2010-2019,the global average near-surface NH3 concentration has been increasing,mainly due to the continuous increase of nitrogen fertilizer use,the expansion of livestock breeding scale,the decrease of other pollution gases in the atmosphere,and the increase of municipal waste.In addition,the abnormal meteorological conditions and a large amount of concentrated combustion of biomass will also have a short-term effect on the near-surface NH3 concentration.(4)The near-surface NH3 concentration presents seasonal and periodic changes,with different causes and significant spatial heterogeneity.From a global perspective,the seasonal relationship of the near-surface NH3 concentration in the northern hemisphere is summer(June-July-August),spring(March-April-May),autumn(September-October-November),and winter(December-January-February),and the seasonal relationship of near-surface NH3 concentration in the southern hemisphere as a whole is spring(September to November),winter(June-July-August),and autumn(March-April-May),summer(December-January-February).All administrative regions in China have the highest in summer,followed by spring,but the relationship between autumn and winter is different.Changes in the growing season of crops,seasonality of the climate,seasonality of grazing activities,and production management economic policies in various regions have combined to cause the seasonal variation of the near-surface NH3 concentration in different regions.(5)The near-surface NH3 concentration in China is related to many factors,such as land cover,human activities,meteorology and so on,and different factors have different influence degrees.The near-surface NH3 concentration of different land cover types is impervious surface(6.15?g/m3),farmland(5.77?g/m3),water area(3.05?g/m3),woodland(2.12?g/m3),grassland(1.74?g/m3),snow and ice area(0.95?g/m3),and desert area(0.87?g/m3).Anthropogenic factors are positively correlated with near-surface NH3 concentration,with the highest correlation coefficient being NH3 emission(r=0.61,P<0.01),followed by population density(r=0.34,P<0.01),and GDP(r=0.16,P<0.01)being the lowest.The relationship between meteorological factors and near-surface NH3 concentration is complex and has obvious spatial heterogeneity.Surface temperature in most parts of China has significant positive correlation with near-surface NH3 concentration;Precipitation has significant correlation with near-surface NH3concentration in only a few areas and most of them are positively correlated;Air relative humidity and wind speed in only the individual regions has significant correlation with near-surface NH3 concentration,but have no correlation in most areas of China. |
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