Nutrient input from street tree leaves is a potentially major contributor [1] to nutrient loads entering the urban water system. Nutrient inputs can cause eutrophication and reduce the biodiversity in the water body [2]. To quantify the impact of leaf litter fall in the catchment area, this research evaluated the release rate and concentrations of carbon (C), nitrogen (N) and phosphorus (P) of both fresh fallen leaves from Eucalyptus mannifera and roadside grass clippings. Leachate experiments were conducted under controlled conditions, with the temperature, water source and aeration varied between treatments. The aim of the experiment was to understand the effect of these factors on nutrient leachate.
Standard leachate tests were conducted with variations in the water used (ultrapure, creek or rain water), temperature (25 ˚C or 15˚C) and oxygenation (with or without aerator) for a 216-hour period. The nutrient leachate samples were collected at intervals of 6, 48, 120 and 216 hours. Preliminary results show that grass released dissolved organic carbon (DOC) quicker, but tree leaves released more DOC over the experimental period. For both leaves and grass-clipping samples, the non-oxidized treatment caused higher carbon release than the aerated treatment. Many leachate tests are conducted under a single set of conditions. The results from this study demonstrate the effect of changing water type, temperature, and oxygen concentrations on nutrient leaching. These results assist in understanding how variation in these conditions in the natural environment can affect leachate rates and the effect of experimental conditions when undertaking leachate experiments.