| Ammonia is one of the key components involved in the atmospheric nitrogen cycle and is the most important alkaline gas in the atmosphere.Studies have shown that ammonia emissions have direct or indirect effects on many environmental problems such as acid deposition,atmospheric visibility,soil acidification,greenhouse effect and eutrophication.Ammonia and SO2 and NOx in the atmosphere together constitute an important precursor of fine particles in the atmosphere,and the secondary particles(NH4NO3,NH4HSO4,(NH4)2SO4,etc.)formed by mutual reaction are important components of atmospheric PM2.5,and its high moisture absorption and small particle size can significantly affect the scattering level of visible light in the atmosphere,thus reduce the visibility of the atmosphere,and play an important role in the formation of strontium.In general,the sources of ammonia in the atmosphere are divided into anthropogenic sources and natural sources.Most studies have shown that anthropogenic sources are the main source of atmospheric ammonia emissions,and anthropogenic sources of NH3 are mainly derived from agricultural farming and livestock and poultry farming processes.These two sources account for about 70-90%of the total ammonia emissions,and livestock and poultry farming is the most important source of ammonia emissions.As the scale of dairy farming is increasing in China,and there are few localization studies on ammonia emission characteristics currently carried out in dairy farms,it is of great significance to carry out research on ammonia emission characteristics of typical scale dairy farms in Shanghai.In this study,the typical,scaled dairy farms in Shanghai were used to study the ammonia emission characteristics of shed housing breeding,manure composting and sewage storage by means of on-line monitoring of electrochemical sensors,and the effects of major meteorological factors(temperature,wind speed)on ammonia emissions were discussed.The ammonia emission factors of the three major ammonia emission links were calculated using the micrometeorological model,and a localized ammonia emission factor for large-scale dairy farms is obtained by aggregation.The results shows:(1)Ammonia emission characteristics of shed housing breedingThe ammonia concentration levels in the typical days of spring,summer,autumn and winter in the scale dairy farm shed housing are 2.5～4.67 mg·m-3、5.36～7.95 mg·m-3、4.65～1.16 mg·m-3、2.34～3.10 mg·m-3,respectively.Ammonia concentration is expressed as summer>autumn>spring>winter,The ammonia concentration in typical days of spring,summer and autumn is characterized by higher daytime and lower nighttime,The ammonia concentration increased from 8:00 am and to 15:00～16:00 pm to reach the maximum,while the typical ammonia concentration in the winter did not fluctuate overall and was relatively stable.The ammonia emission factors of spring,summer,autumn and winter are 34.61±15.06 g·head-1·d-1 46.93±3.89 g·head-1·d-1,36.82±8.99 g·head-1·d-1,16.86±6.00 g.head-1·d-1 respectively,and the average annual emission factor is 36.11±14.16 g head-1·d-1.(2)Ammonia emission characteristics of manure compostingThe ammonia concentration levels in the typical day of spring,summer,autumn and winter in the scale dairy farm manure composting are 1.83～3.76 mg·m-3、3.40～8.71 mg·m-3、2.40～8.68 mg·m-3、1.36～3.06 mg·m-3 respectively.The change of ammonia concentration is characterized as summer>autumn>spring>winter.The ammonia concentration in typical days of spring,summer and autumn is characterized by higher daytime and lower nighttime.The ammonia concentration rises from 8:00 am to 12:00～15:00 pm,and the ammonia concentration in the typical daytime fluctuates little.The ammonia emission factors of spring,summer,autumn and winter are 12.83±5.31 g·head-1·d-1、36.29±10.27 g·head-1·d-1、11.58±4.12 g·head-1·d-1、10.01±3.83 g·head-1·d-1 respectively,and the average annual emission factor is 21.08±14.14 g·head-1·d-1.(3)Ammonia emission characteristics of sewage storageThe ammonia concentration level of the scale dairy farm sewage storage link in the spring,summer and autumn seasons is 2.74～9.18 mg·m-3、4.68～9.80 mg·m-3、3.84～7.71 mg·m-3 respectively.The change of ammonia concentration is characterized as summer>spring>autumn.The typical intra-season ammonia concentration is characterized by higher ammonia concentration during dry-wet separation operation and lower ammonia concentration in other periods.The ammonia emission factors in spring,summer and autumn are 23.52±13.90 g·head 1·d-1,33.26±11.06 g·head-1·d-1,20.19±6.32 g·head-1·d-1 respectively,and the three-season average ammonia emission factor is 26.68±12.35 g·head-1·d-1.(4)Comprehensive ammonia emission characteristics of scale dairy farmsThe average ammonia emission factors of the three major discharges of typical scale dairy farms of shed housing,manure composting,and sewage storage are 36.11±14.16 g·head-1·d-1,21.08±14.14 g·head-1·d-1,26.68±12.35 g·head-1·d-1.The ammonia emission intensity of the three links is:shed housing>sewage storage>manure composting.It shows that the shed housing breeding is the most important part of ammonia discharge in scale dairy farms,and the control of ammonia emissions in dairy farms should be the priority control target.The average annual ammonia emission factor of large-scale dairy farms is 83.87 g·head-1·d-1.Annual emission level reached 30.61 kg·head-1·y-1.Explain that the contribution of single-headed cows to atmospheric ammonia emissions is considerable.(5)Correlation between ammonia concentration with temperature and wind speed in shed housing breeding,manure composting and sewage storageThe influence of ambient temperature and wind speed on the overall ammonia concentration of the four seasons of shed culture,manure composting and sewage storage was significant(P<0.01).The correlation coefficients with ambient temperature are 0.845,0.794,0.712,respectively,and the correlation coefficients with ambient wind speed are-0.471,-0.284,-0.483,respectively;and the ambient temperature was positively correlated with the ammonia concentration of the three ammonia emission links.The wind speed and three ammonia emissions.The ammonia concentration in the link was negatively correlated. |
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