| The NH3 emissions from the pig farms account for a large proportion of agricultural NH3 in our country,which contributes a lot to the formation of atmosphere PM2.5 and haze.To estimate the amount of NH3 emissions from piggeries accurately and investigate their effects on mass concentration and chemical compositions of atmospheric PM2.5,we calculated the NH3 emission factors of pigs using the crude protein estimation method,material flow method,and direct measurement method,respectively.Then,the NH3 and PM2.5 concentration were continuously monitored on July 13 to19,2017,using the stationary NH3 on-line detectors and the ambient PM2.5on-line monitoring analyzers inside and outside a pig farm situated at Jiancaoping district,Taiyuan city,China.A modified seven-stage MAY cascade impactor and two medium-volume filter-type PM2.5 samplers were used to collect atmospheric PM2.5 samples for single-particle and bulk analysis,respectily.The contents of water-soluble inorganic ions in PM2.5were measured by an ion chromatograph and the morphology,mixing state and X-ray element characteristics of individed particles were analyzed by the electron microprobe X-ray microanalysis（EPMA）.The relationship between the concentrations of NH3 and ambient PM2.5 inside and outside the farm and the influences of NH3 on PM2.5 compositions were analyzed using correlation analysis and other methods.The results showed:（1）The NH3 emission factors of pigs calculated by the crude protein estimation,the material flow method and the direct measurement method,were 11.33,6.90 and 0.56 kg/（animal·yr）,respectively,and the results calculated by direct measurement method were close to those obtained by calibration.（2）The daily average concentrations of NH3 outside and inside farms were（5.37?0.35）mg/m3 and（7.49?0.37）mg/m3,respectively,and their changes were consistent,while the daily mean concentrations of atmospheric PM2.5 in pigs and piggeries were（0.093?0.0018）mg/m3 and（0.081?0.0055）mg/m3 respectively,and their fluctuation range were different.However,the concentration of NH3 inside and outside the farms is significantly related to the concentration of ambient PM2.5 outside the farm.（3）There was significant correlation between NH4+and SO42-and NO3-in water-soluble inorganic ions of PM2.5 inside and outside the farm,and the NH4+/SO42-is more than 1.5.（4）The relative abundance of mineral dust particles,carbon-containing particles and secondary particles in the farm was 37.6%-61.5%,25.9%-49.6%and10.0%-14.9%,together with 37.1%-58.9%,26.0-47.4%and 8.2%-23.5%outside the farm,respectively.The reactive mineral dust particles containing nitrogen in the pig farm was significantly larger than that out of piggery,and the concentration of N element in the secondary particles in the farm was higher than that outside the pig farm.The above results indicate that NH3 emissions from piggery are affected by many factors,and the NH3 emission factors calculated by different methods are quite different.The NH3 emissions from pig farms can not only increase the mass concentration of PM2.5 surrounding the farms,but also increase the nitrogen-containing particles in the atmospheric PM2.5,accelerating the aging process of particles.However,further researches on the mechanism of NH3 emissions from pig farms and its effects on ambient PM2.5.5 are still needed. |
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