OCTANOL PARTITION-COEFFICIENTS FOR WETLAND HUMUS

Many of the wetlands on the Swan Coastal Plain, Western Australia are nutrient-rich and subject to blooms of blue-green algae. Some of these wetlands, however, are dystrophic and are less likely to experience a lgal blooms possibly because of high gilvin levels. Gilvin (yellow col our determined by absorbance at 440 nm) levels and the octanol/water p artition coefficient (Khow) for humic stained waters from eleven wetla nds and the leachate from the leaves of two Eucalyptus tree species an d Bassendean soil, all major components of the Swan Coastal Plain, Wes tern Australia were determined. Gilvin levels in the wetlands were hig h (20-58 m(-1)) while gilvin in leachate from Eucalyptus marginata lea ves soaked for 30 days was 349 m(-1) and gilvin in Bassendean soil lea chate was 610 m(-1). Gilvin from E. calophylla leaves soaked for 30 da ys was markedly less (67 m(-1)). Three samples, the leachate from the leaves of E. calophylla, the leachate from the top 50 cm of Bassendean soil and water from one wetland (Gingin) showed ecologically signific ant Khow values ranging from 1.68 to 3.59 at pH 4. These Khow's derive d are similar to many organic chemicals in use today including algicid es and herbicides. It is suggested that inhibition of algal growth and production will occur in the humic stained waters of Gingin wetland. A probable source of this humus rich material is decomposing Eucalyptu s leaves and other material in the upper horizon of Bassendean soils o f the wetland catchment.