Study on the Applicability of Passive Sampling Method for Ambient Ammonia and Its Application in Urban Observation
In this study,the applicability of the ALPHA passive sampling method in terms of sampling adsorption filter preparation,sample preservation,and sampling period was carried out for ambient ammonia observation and compared with the active sampling method for validation,and further field observation application studies were conducted in different functional areas of Shanghai based on the results of the study.The results showed that the NH+4 content of the adsorption filters obtained by the acid immersion method was(0.27±0.13)μg,which was about 8%higher than that of the untreated adsorption filters,and the number of single immersions could be increased in the range of 1∶4-8∶4(slice/mL)to reduce the amount of solvent used in the preparation process.The preparation process of the acid immersion method and the different filter-to-liquid ratio treatments had few effects on the NH+4 content of the blank adsorption filter.The method detection limit for this passive method of ambient ammonia determination was 0.08 μg/m3 when the sampling temperature was 20℃and the sampling period was 168 h.The preservation method using the double-sealed bag,4℃frozen,and preserving for less than 30 days had not significantly increased the NH+4 content of the blank filter,which is suitable for the preservation of blank and sample filters.The applicability verification results of the sampling period showed that the number of the sampling period is recommended to be at least 6 days and at least 30 days for continuous sampling when using ALPHA passive sampling in urban areas to measure ambient ammonia.The observed NH3 concentration trends of the ALPHA passive sampling method and active sampling method were more consistent,and the measurement results were correlated well(correlation coefficient of 0.87,slope of 1.16),which further proved that the passive NH3 sampling method used in this study has good reliability for the measurement of ambient ammonia concentration.The actual observation results showed that the average ambient atmospheric NH3 concentration during the summer of 2022 in Shanghai was 10.01±5.22 μg/m3,and the NH3 concentration level affected by the extremely high-temperature climate in summer of 2022 was significantly higher than the results of past studies.The NH3 concentrations in different functional areas were ranked as follows:agricultural area(13.36±5.24)μg/m3＞industrial area(11.22±5.24)μg/m3＞urban area(10.35±4.39)μg/m3＞ecological area(4.28±2.4)μg/m3,which showed that although the high concentrations of NH3 at the monitoring stations related to agricultural activities were significant,the influence of non-agricultural source emissions on NH3 concentrations in the urban and industrial areas could not be ignored as well.The ALPHA passive sampling method can better capture the characteristics of ammonia concentration in different functional areas of the city,which can meet the application of ammonia concentration observation in urban environment,and the applicability verification and application provide a reference for accurate measurement of NH3 in the regional and urban atmosphere.
万方数据
维普
