Characterisation of Natural Organic Matter (NOM) in litter Leachates from Drinking Water Catchments

Pruning, thinning and harvesting of planted Pinus radiata forests have the potential to export large amounts of terrestrial natural organic matter (NOM) to surface waters. The characteristics of NOM are a function of its precursor material. The chemical composition of NOM has the potential to interfere with water treatment processes, by fouling membranes and reacting with the disinfection process. In this study, litter leachates from two drinking water catchments were compared; a mixed vegetation native forest and a catchment dominated by Pinus radiata. Greater amounts of NOM were leached from native forest litter when compared to pine forest litter. However, NOM in pine forest litter leachate was characterised by lower molecular weight and more protein-like compounds. These compounds are more difficult to remove during water treatment and considered reactive with the water treatment process. Due to the management activities occurring, planted pine forests have the potential to transport large quantities of harder to treat and reactive NOM to surface waters. Understanding the differences in NOM chemistry between vegetation types will allow water utilities to better predict the quantity and quality of NOM transported to surface waters in drinking water catchments.