High NH3 deposition in the environs of a commercial fattening pig farm in central south China

Intensive livestock production has been increasing, and has resulted in the emission of more than seven teragram per year of ammonia (NH3) in China in recent years. However, little is known about the fate of the emitted NH3, especially the dry deposition of NH3 in the environs of intensive animal farms. In this study, the spatial and temporal variations of NH3 deposition in the environs of an intensive fattening pig farm were investigated in the central south of China. NH3 concentrations were measured at sites situated 50, 100, 200, 300, and 500 m in the downwind direction from the farm each month from July 2018 to June 2019. The NH3 deposition was calculated based on a bidirectional NH3 exchange model. The monthly NH3 emissions from the pig farm were estimated based on the breeding stock. The annual average NH3 concentrations ranged from 1200 to 14 mu g m(-3) at the downwind sites within 500 m of the pig farm, exhibiting exponential decay as distance increased. Strong seasonality in NH3 deposition was observed, with the highest season being in the summer and lowest in the winter, and air temperature was found to be an important factor affecting this seasonal variation. The estimated monthly total dry deposition within 500 m of the pig farm ranged from 92 to 1400 kg NH3-N mo(-1), which accounted for 4.1%-14% of the total monthly NH3 emissions from the pig farm. The estimated total NH3 emissions and NH3 deposition from the pig farm were 63 000 kg NH3-N yr(-1) and 5400 kg NH3-N yr(-1), respectively, with the annual average ratio of NH3 deposition to NH3 emission being 8.6%. This study found NH3 deposition around intensive pig farms is high, and determined it as a significant fate of the NH3 emitted from pig farms.

Automated summary

Intensive livestock production in China has led to significant NH3 emissions, with high levels of NH3 deposition observed around intensive pig farms. Seasonal variations show higher deposition in summer and lower in winter, with air temperature playing a key role in this seasonal trend. NH3 deposition accounts for 4.1%-14% of NH3 emissions within 500 meters of the pig farm, with an annual average NH3 deposition to emission ratio of 8.6%.