The chemistry of the degradation of organic pesticides, herbicides and fungicides in natural systems determines operationally important parameters such as withholding times before planting or consumption. Free radicals are being increasing recognised as important in environmental chemistry and in aqueous systems the OH, H, and O2- radicals are believed to be relevant to the degradation of organic molecules. Sources of these radicals in the natural aqueous systems have been suggested as photo chemical or transition metal reactions involving dissolved organic species such as humic acids.
We are undertaking a systematic study of the reactions of free radicals with important herbicides and fungicides in order to obtain rate constant data for modelling the possible reactions in field conditions and to establish whether the postulated reactions are capable of accounting for the disappearance of the materials in the environment. In addition to using gamma and pulse radiolysis to determine product yields, rate constants and the presence of reactive intermediates, we have begun to explore the stability and geometry of possible radical intermediates using Gaussian computations.
At present ten pesticides in current use in Australia are being studied. Their structures can be seen below.
The now defunked pulse radiolysis apparatus I use to use
The electrospray mass spectrometer (a LC-Q) that I use to analyse the products of the free radical reaction
Definition of a Ph.D!!!!