A 4 month scientific exchange to the University of Guelph in Canada; and

DuPont and Waterborne Environmental Inc. in the USA enabled work with

world leaders in the area of ecological risk assessment of agrochemicals.

Under the supervision of world leading toxicologists, Prof. Keith Solomon

and Prof. Mark Hanson, a toxicity experiment was conducted that

investigated the potential recovery of two species of Duckweed (Lemna gibba

and L. minor) following exposure to the herbicide Diuron at the University of

Guelph, Canada. When the macrophytes were exposed to a range of

concentrations, Diuron was found to reduce the population growth rate

(widely considered a significant toxicology endpoint for aquatic macrophytes

and algae), which is not new, however, following exposure the macrophytes

were found to recover to a point that is not significantly different to the

population growth rate of the control cultures. The results of this experiment

may highlight questions about whether standard toxicity data adequately

represent exposure scenarios that are commonly observed in catchments.

At DuPont and Waterborne environmental experience was gained in the

development of and running a spatial exposure model developed by these

organisations. Under the supervision of Dr. Aldos Barefoot and Dr. Gerco

Hoogeweg I was able to participate in the simulation modelling and data

gathering processes. It is hoped that I will be able to use these same models to

predict spatial environmental fate and exposure in the Gwydir River

catchment. Further to this, testing a number of management scenarios will

also be used to investigate the impact that they may have on the fate of

chemicals.