Determination of the atmospheric volatility of pesticides using Filter Inlet for Gases and AEROsols–chemical ionisation mass spectrometry

Pesticides have been found to be transported through the atmosphere away from fields after application. A key indicator of a pesticide's likelihood to reside in the atmosphere is its vapour pressure. Within this study we evaluate a novel method, the Filter Inlet for Gases and AEROsols (FIGAERO) coupled with a chemical ionisation mass spectrometer, using a set of calibration compounds, polyethylene glycols (PEGs). Two methods of compound delivery onto the filter have been tested: atomisation and syringe deposition. Delivery results are consistent with previous studies, highlighting the lack of suitability of the syringe method. The successful calibration using the atomisation method was then used to determine the vapour pressure of six pesticides. This is the first time particle-phase pesticides have been measured with particle-phase chemical ionisation mass spectrometry (CIMS). The pesticide volatilities were compared with widely accepted standard literature values used in industry, as well as values derived from a common environmental model frequently employed in industrial applications. Results showed that measurements from the FIGAERO-CIMS were consistent with reported literature values for some compounds, while others differed by up to 2 orders of magnitude. Determinations of dicamba, MCPA, and MCPP volatility using the FIGAERO-CIMS showed them to be semi-volatile, in agreement with literature values within 1 order of magnitude. Mesotrione exhibited the largest difference in volatility, with the FIGAERO-CIMS measuring a low volatility of 4.12×10-8Pa at 298 K (compared to a literature value of 5.7×10-6Pa). The difference for 2,4-D of 1 order of magnitude can be explained by the smaller particles deposited on the FIGAERO filter compared to the aerosolised PEG calibration particles, leading to evaporation at higher Tmax values and a lower measured vapour pressure and thus further supporting the conclusion that a calibration using the same particle size is required. The atmospheric implications of the pesticide volatilities are also discussed. A pesticide's volatility is often a key indicator of the likelihood of the potential for short- or long-range transport occurring, thus determining a pesticide's fate in the atmosphere and potential for environmental pollution from transportation in the air.