Towards a better understanding of the lifecycle of Pesticides in the Atmosphere

Since pesticides have been measured on regional scales and in the background environment there is a pathway for transport to these remote locations from the area of application. Given the distance scales this is likely to involve transport via the atmosphere, either in the gas phase or particle phase, or in all likelihood both. There are potential health impacts at the near field scale to farm workers or nearby inhabitants and previous work has investigated this near field transport during periods of application.

There is an absence of data on how the emission of pesticides evolves after application and what environmental factors, if any control further release. There is also a lack of data at the wider scale. This PhD project will examine the fluxes of pesticide from the point of application to the regional scale.

Mass spectrometric detection of pesticides in the gas phase is now possible using online methods. UoM has extensive expertise in eddy correlation flux measurements of particulates and gases. Essentially the technique uses correlation between rapid changes in the component concentration of interest and the vertical wind velocity to derive a flux.

Chemical ionisation mass spectrometry (CIMS) has been shown to be capable of measuring pesticides in the gas phase and this has previously been applied to eddy correlation measurements of organic matter in Finland. The UoM CIMS can be developed into such a flux system and used to examine gas phase emission fluxes. The UoM instrument can also be fitted with an electrospray ionisation inlet (EESI) which allows online measurement of the particle phase concentration of pesticides and this can also be operated in flux mode.

The objectives are: 1) to develop a flux system for both the gas and particle phase characterisation of pesticides 2) to demonstrate the capability of the system at the field scale 3) to quantify fluxes of pesticides at the field and regional scale

Initially the work will involve developing a working knowledge of the CIMS-ToF-MS instrument and the analysis tools used to analyse the data. The EESI inlet will also be fitted and the student will work on understanding this system. We have collaborators in the USA who have already worked on an eddy correlation version of the CIMS instrument and will assist with the development of the CIMS and the EESI configurations, both of which will use the same mass spectrometer system.

The development of this system will be a major task of the first year and the first part of the second year of the study.

The system will then be tested in a series of field studies designed to assess the emission fluxes during and following application under a range of environmental conditions and around specific farming practices such as ploughing and harvesting. Particle flux measurements will also be made during controlled trials. This work can then be extended by examining the concentrations of pesticides at the region scale during a period before, during and after extensive pesticide application to examine the regional burden.

A way of achieving this could be to target aircraft flights with generic seasonal periods and link these to documented activity in emission under suitable boundary layer conditions. The PhD would entail instrument development, as well as data analysis and interpretation.