| Ammonia is a toxic gas with an irritating and foul odor.The secondary inorganic aerosol formed by atmospheric ammonia with sulfuric acid and nitric acid is the main component of atmospheric fine particulate matter(PM2.5)and is the key of haze pollution.At the same time,ammonia has become the main nitrogen sediment,which leads to the degradation of ecosystem function.However,the international community still lacks attention to ammonia emission reduction.One of the main reasons for this situation is that anthropogenic ammonia emission sources and their contribution to atmospheric ammonia is not completely clear,so it is difficult to formulate practical emission reduction plan.At present,the study of atmospheric ammonia source analysis is very lacking.Studies have generally classified ammonia emissions as agricultural sources and non-agricultural sources in two broad categories.Agricultural sources include livestock and poultry breeding and planting industry.The total emission of non-agricultural sources is relatively small,but there are many kinds of sub-emission sources,including waste water discharge sources,solid waste discharge sources,fossil fuel combustion sources(coal-fired power plants and car exhaust emissions).The δ15N-NH3 of ammonia was used as the analytical tool in atmospheric ammonia source analysis.Using the δ15N-NH3 value can distinguish the agricultural source and fossil fuel combustion sources exactly.However,the analysis of atmospheric ammonia sources requires further searching sub-discharge sources,it is difficult to achieve with only δ15N-NH3.Stable isotope combination technology can provide more information to distinguish different sources of compounds.Therefore,the combination of δ155N-NH3 and δD-NH3 can be used to allocate NH3 source and establish a more perfect ammonia source spectrum.Meanwhile,based on theδ15N-NH3 and δD-NH3 data of ammonia and emission sources in the atmospheric environment,the atmospheric ammonia sources in urban areas were analyzed by isotopic mixing model(Isosource).Finally,the contribution rate of each emission source in Qingdao to the atmospheric ammonia in urban areas is revealed,and the impact of anthropogenic ammonia emission on the ecological environment is evaluated.The specific research contents are as follows:1.It has been experimentally verified that the Chemcomb honeycomb denuder(coated with 4%citric acid methanol solution)with absorption efficiency of more than 99%for different concentrations of NH3 can be used to collect atmospheric ammonia for δ15N-NH3 analysis of samples.At the same time,it was found that the adsorption efficiency of MgCl2 to different concentrations of NH3 was over 99%,and it could be collected NH3 for δD-NH3 analysis,thus avoiding the interference of hydrogen isotopes in water to ammonia.For the analysis method of samples forδ15N-NH3,the phosphoric acid solution was reduced by BrO-oxidized hydroxylamine(NH2OH)converting NH3 to N2O for analysis.Regarding the analytical method ofδD-NH3,by experiments,it was determined that the MgCl2 after the ammonia gas was collected(MgCl2·xNH3)in different emission sources were injected element analyzer to release NH3 and the NH3 splitting into H2 and N2 simultaneously.Subsequently,N2 was introduced into the isotope ratio mass spectrometer(IRMS)for isotope analysis.2.Two sets of field sampling devices were prepared according to the above sampling methods for the sampling of δ15N-NH3 and 8D-NH3,respectively.Field sampling sites are mainly determined to include:pig farms.chicken farms,wheat fields,straw incinerators,power plants,road tunnels,municipal sewage plants,public classrooms,urban environmental areas.The samples collected in the field were analyzed by the above isotopic analysis methods.δ15N-NH3 can distinguish the agricultural and non-agricultural sources of atmospheric ammonia better,but its sub-emission sources have more overlap.Also observe the δD-NH3 of each emission source found under each emission source,their sub-emission sources have a large difference about δD-NH3.Therefore,the combination analysis of the δ15N-NH3 andδD-NH3 of atmospheric ammonia emission sources can identify each emission source better,and provide theoretical basis for predicting ammonia pollution,which is of practical significance in perfecting the ammonia emission inventory and formulating the ammonia emission reduction plan in China.The contribution rate of each ammonia emission source to urban area is as follows:the percentages of fossil fuel burning,livestock and poultry farming,farmland fertilizer,biomass burning,human respiratory emissions,and sewage plants are 39%,10%,19%,8%,3%,21%.The analysis found that fossil fuel combustion and agricultural emission sources contributed the most to ammonia emissions in urban areas of Qingdao,which may be related to urban intensive nitrogen fertilizer farming.Secondly,it was found that biomass combustion still has a higher contribution rate,so the control of biomass burning should be further strengthened on the basis of the original.At the same time,the contribution of residents ’emission sources to Qingdao’s urban areas is large,and it needs to be given sufficient attention. |
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