| Bioaerosol is one of the air pollutants in livestock and poultry houses,and it is the main medium that causes disease infection.North China is the main producing area of dairy cows in my country.Summer and autumn are the seasons with the most frequent gas exchange inside and outside dairy farms,and the ambient humidity,temperature and ultraviolet radiation are high during this time,which has a greater impact on the concentration of bioaerosols.The emission characteristics of bioaerosols from dairy farms in typical seasons.Bioaerosols and environmental parameters were collected continuously,the distribution characteristics of bioaerosols in different functional areas of dairy farms and the spatial distribution characteristics of bioaerosols in dairy farms were analyzed,and the comprehensive gradient method was used to estimate aerosol emission intensity in a large dairy farm in Tianjin.Based on the above results,a prediction model was established to obtain the ranking of the influence of environmental factors on the concentration of bioaerosols.The results of this study can provide prior knowledge and basic reference data for bioaerosol diffusion and biosafety assessment for the study of bioaerosols in livestock and poultry farms,and can provide suggestions for streamlining the collection of environmental factors that affect bioaerosol concentrations.The results showed that during the sampling time,the daily variation trend of the concentration in different functional areas was quite different,and the distribution ranged between1.14×10~3-7.35×10~3 CFU/m~3.It was found that bacterial bioaerosols were mainly distributed in coarse particles(particle size greater than 2.1μm).The bioaerosol concentrations were significantly higher than those at a height of 4 m near the ground(P<0.05).There is seasonality in particle size distribution.And in the same sampling period,the distribution trend of colony number distribution in different functional areas,different sampling heights and each particle size range is similar.The particle size distribution is seasonal.The larger the particle size in summer,the higher the proportion.In autumn,the proportion of particles with particle size larger than 7.0μm and between 1.1 and 2.1μm is the highest.In the same sampling period,the distribution trend of colony number distribution in each particle size range at different sampling heights was similar.The bioaerosol emission intensity was estimated using the comprehensive gradient method,in which the emission intensity of the production area was 13.03±9.63 CFU/m~2/s,and the emission intensity of the manure treatment area was 26.85±11.09 CFU/m~2/s.The discharge amount was606.61±380.52 CFU/cow/s.The study found that the emission intensity of biological aerosols in dairy farms is greatly affected by the weather,the ultraviolet radiation intensity is negatively correlated with the emission intensity,the total radiation intensity is negatively correlated with the emission intensity,temperature is negatively correlated with the emission intensity,and humidity is negatively correlated with the emission intensity.It is positively correlated with emission intensity.Based on the random forest algorithm and the control variable method,the ranking of the influence of environmental factors on the bioaerosol concentration was obtained.The results showed that in different seasons,environmental factors such as PM100 concentration,wind direction,temperature,and ultraviolet radiation intensity have a greater influence.Using the hierarchical clustering method to analyze the collinear relationship of the influencing factors,it is found that the PM1 concentration can be used to replace the PM2.5 concentration and PM10concentration,and the ultraviolet radiation intensity can be used to replace the total radiation intensity.accuracy.In other studies,the collection of environmental factors can be simplified according to the test conditions and combined with this paper,thereby saving the test cost. |
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