Thermophilic fungi in air samples in surroundings of compost piles of municipal, agricultural and horticultural origin

Abstract

In this study, the effect of the thermophilic fungi of composts was analysed on the fungal composition of the air above. Air samples were collected with an Andersen air sampler at 1.5 m height in three large industrial composting facilities treating different waste types. Repetition was collected on three calm and rain-free days of three consecutive weeks in October 2011, in January, April and July 2012; five plates were exposed successively per sampling day. Compost samples were also collected (averaging 1 kg/compost piles). Air and compost samples were cultured at 50 °C. The thermophilic fungal composition of the air near the compost piles of different waste types differed significantly (p < 0.05) from that of the control site above a grassland ecosystem at each sampling time. Seasonal differences could be detected regarding the total number of thermophilic fungi in the air near the agricultural and horticultural compost types, but smaller differences were found near the municipal compost type. A total of 13 and 11 fungal species were detected in the compost and air samples where the dominant species were Thermomyces lanuginosus and Rasamsonia emersonii, respectively. The concentration of airborne thermophilic fungi was higher near the horticultural compost type and lower near the municipal compost. The results suggest that the differences between the incidences of some species in composts and associated aerosols refer to spore ontogeny and biological mechanisms of spore liberation.