Emissions of ammonia and hydrogen sulfide from typical dairy barns in central China and major factors influencing the emissions.

There are few studies on the concentrations and emission characteristics of ammonia (NH) and hydrogen sulfide (HS) from Chinese dairy farms. The purpose of this study was to calculate the emission rates of NH and HS during summer and to investigate influencing factors for NH and HS emissions from typical dairy barns in central China. Eleven dairy barns with open walls and double-slope bell tower roofs from three dairy farms were studied. Five different locations in each barn were sampled both near the floor and at 1.5 m above the floor. Concentrations of NH and HS were measured using the Nessler's reagent spectrophotometry method and the methylene blue spectrophotometric method, respectively. NH concentrations varied between 0.58 and 4.76 mg/m with the average of 1.54 mg/m, while HS concentrations ranged from 0.024 to 0.151 mg/m with the average of 0.092 mg/m. The concentrations of NH and HS were higher during the day than at night, and were higher near the ground than at the height of 1.5 m, and were higher in the manure area than in other areas. NH and HS concentrations in the barns were significantly correlated with nitrogen and sulfur contents in feed and manure (P < 0.05), and with temperature inside the barns (P < 0.05). Calculated emission rates of NH ranged from 13.8 to 41.3 g NH/(AU·d), while calculated emission rates of HS ranged from 0.15 to 0.46 g HS/(AU·d). These results will serve as a starting point for a national inventory of NH and HS for the Chinese dairy industry.