Characteristics of PM(2.5) and Its Correlation with Feed, Manure and NH3 in a Pig-Fattening House

Fine particulate matter (PM), including PM(2.5) in pig houses, has received increasing attention due to the potential health risks associated with PM. At present, most studies have analyzed PM(2.5) in Chinese pig houses utilizing natural ventilation. These results, however, are strongly affected by the internal structure and regional environment, thus limiting their applicability to non-mechanically ventilated pig houses. This experiment was carried out in an environmentally controlled pig house. The animal feeding operation and manure management in the house were typical for Southwest China. To reduce the influence of various environmental factors on PM(2.5), the temperature and humidity in the house were maintained in a relatively stable state by using an environmental control system. The concentration of PM(2.5) in the pig house was monitored, while the biological contents and chemical composition of PM(2.5) were analyzed, and feed, manure, and dust particles were scanned using an electron microscope. Moreover, bacterial and fungal contents and some water-soluble ions in PM(2.5) were identified. The results showed that the concentration of PM(2.5) in the pig house was strongly affected by pig activity, and a phenomenon of forming secondary particles in the pig house was found, although the transformation intensity was low. The concentration of PM(2.5) had negative correlations of 0.27 and 0.18 with ammonia and hydrogen sulfide, respectively. Interestingly, a stronger correlation was observed between ammonia and hydrogen sulfide and ammonia and carbon dioxide concentrations (the concentration of ammonia had stronger positive correlations with hydrogen sulfide and carbon dioxide concentrations at +0.44 and +0.59, respectively). The main potential sources of PM(2.5) production were feed and manure. We speculate that manure could contribute to the broken, rough, and angular particles that formed the pig house PM(2.5) that easily adhered to other components.