| Agricultural ammonia emissions are the main contributors to anthropogenic ammonia emissions.Agricultural sources of ammonia emissions,on the one hand,come from the application of chemical fertilizers,mainly from animal production(50%to 80%).With the highly intensive development of China's livestock and poultry breeding industry,environmental pollution caused by NH3 emissions has become more and more serious.At present,China is paying close attention to ammonia emissions from farms,but relevant research data is still lacking.Therefore,accurately assessing and effectively mitigating ammonia emissions at the scale of livestock and poultry breeding is of great significance to improving nitrogen use efficiency,reducing nitrogen deposition and mitigating smog pollution in China.This study selected two types of(3)dairy farms with different feeding and manure management modes in the Bashang cold region of Hebei Province(including a"Barn only" and two "Barn+Lot" structured dairy farm),Adopting the inverse dispersion technique in combination with open-path tunable diode lasers to measurement on site,and inputting information such as feed and manure management from the farm into the"Ammonia and Greenhouse gases Intelligent Tool"(AGRIT)software for model estimation.The characteristics and differences of NH3 emission from different types of(3)dairy farms in winter and summer under different feeding conditions and different manure management measures.In addition,for the direct open-air storage of dairy farm manure,the simulation and investigation of ammonia reduction during the process of wild manure storage by adding coverings and additives.On this basis,the consistency of the three methods for measuring ammonia by venting chamber technique(VCT),dynamic chamber technique(DCT),and passive sampling technique(PST)were compared.The emission reduction rates of the two types of emission reduction measures obtained were further input into the "Barn+Lot" type dairy farm to explore the overall ammonia emission reduction effect.The main findings are as follows:(1)The concentration of ammonia near the ground in winter and summer is within the range of 0.36?1.69ppmv,0.03?0.72ppmv and 0.16?0.77ppmv,respectively.The concentration of ammonia in the air of the tested farms was far lower than the safety standard of the breeding industry(20?25ppmv),which was in line with the breeding code.(2)The daily ammonia emission characteristics of dairy farms are high during the day and low at night.The seasonal ammonia emission characteristics are higher in summer than in winter.The ammonia emission rate increases exponentially with temperature and wind speed.Therefore,temperature and wind speed affect ammonia volatilization on the farm main environmental factors.(3)The annual ammonia emission factors of dairy#1?#3 measured by the "bLS"method are 12.95,44.98 and 53.77 kg·head-1·yr-1,and the annual ammonia of 3 dairy farms is estimated by the "AGRIT" software.The emission factors are 15.56,28.23,and 30.64 kg·head-1·yr-1.Compared with the "Barn+Lot" type dairy farm(#2,#3),the actual measurement and model estimation results show that "Barn only"(#1)significantly reduced the NH3 emission rate.(4)VCT,DCT and PST methods all showed the significant reduction effects of the two mitigation practices,where the mitigation potentials of the CZ and TJ were 35.83%?70.33%and 35.89?65.01%,respectively,and the effectiveness of covering vinegar residue(CZ)and applying external additives(TJ)for ammonia mitigation were confirmed.(5)The cumulative ammonia emissions measured by VCT and PST during the test were lower than those of DCT.The ammonia emissions of CK,CZ and TJ treated by VCT method was only 20.46%,10.09%and 11.17%of the measured values by DCT method,while the ammonia emissions of CK,CZ and TJ treated by PST method was 64.38%,68.64%and 61.67%of the measured value by DCT method.(6)After the manure storage process is covered by CZ treatment,the overall ammonia emission reduction rate of the "Barn+Lot" type dairy farm is 10.11?10.33%;after the application of TJ treatment,the overall ammonia emission reduction rate is 9.12?9.31%.To sum up,the "Barn only" housing structure is a breeding method that helps reduce ammonia emissions;Covering vinegar grains and additives(potassium dihydrogen phosphate plus magnesium chloride)are effective measures for reducing ammonia emissions in the state of manure storage in the "Barn+Lot" type farms;The combination of the inverse dispersion technique in combination with open-path tunable diode lasers is a research tool suitable for testing the effect of ammonia control on a farm scale;The combination of DCT and PST is an effective method to test the effect of ammonia reduction on the scale of manure management. |
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