Sorption behaviour of targeted volatile organic compounds on airborne particulate matter using selected ion flow tube mass spectrometry

Abstract

Intensive agriculture emits air pollutants such as inorganic gases, volatile organic compounds (VOC) and airborne particulate matter. The public can suffer from severe odour nuisance caused by these emissions, particularly in areas with high population densities. Odorous compounds are not only present in the free gas phase but undergo a partitioning between the gas phase and particulate matter making particles possible odour carriers. In order to investigate this partitioning behaviour, an advanced analytical method was developed using selected ion flow tube mass spectrometry (SIFT-MS). This method was used to determine the particle-to-air partitioning coefficients of 4 important organic odorants (acetic acid, butanoic acid, phenol and dimethyl disulphide). An air stream with constant VOC concentration was generated in a home-made system and was injected as a step function onto a chromatographic column packed with particles (PM 10 ) collected from a pig stable using high volume sampling. From the registered breakthrough curves, dimensionless particle-to-air partitioning coefficients were calculated. They ranged from 13 × 10 3 ± 3.1 × 10 3 for dimethyl disulphide to 16 × 10 5 ± 1.7 × 10 5 for phenol. Partitioning coefficients can be estimated using octanol–air partitioning coefficients available from the literature (r 2 = 0.94). The results show that particles were enriched in VOC but the fraction of sorbed volatiles was low ( 10 concentration of 1 mg m −3 .