This experiment will use high resolution neutron diffraction to determine for the first time thesolvation structure of the pesticide paraquat in bulk aqueous solution and in the presence of a swelling montmorillonite clay. This latter sample is directly relevant to the problems associated with the pollutant action of our target molecule (and remediation via immobilisation in clays), while more generally this molecule is of fundamental interest as an aromatic hydrogen-bonding molecule soluble in water, and also of major environmental importance as a pollutant of groundwaters, resulting from its use as a herbicide and pesticide. Here we will use second order H/D substitution and EPSR analysis to investigate the solvation of paraquat.