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Centre for Plant & Water Science 2008 Annual Report MODELLING THE ROLE OF VEGETATION IN PHYTOCAPPING SUMMARY Landfill has been the most popular method of disposing wastes in urban areas. Landfills mostly contain putrescible wastes which can cause environmental hazards, if they come in contact with water. Thus, preventing entry of water into buried waste is the most important aspect in landfill remediation. Currently compacted clay capping is used to prevent percolation of water into waste. However, recent studies have shown that this practice is often ineffective. An alternative capping system known as ‘Phytocapping’ was, therefore, tested at Rockhampton. Phytocapping is the process of establishing vegetation on a layer of soil placed over the waste, so that the soil layer stores the water during rainfall events and the plants will remove the stored water during subsequent periods. Optimisation of these two events can result in prevention of water entering the waste. The Rockhampton trial involved the use of two depths of soil (thick 1400 mm and thin 700 mm) and 21 tree species. The trees and the soil were monitored for three years. The trial demonstrated that the phytocapping can effectively limit the entry of water into the landfill, and the presence of vegetation is critical to achieve a desirable site water balance. The predicted percolation was 133.3 mm yr -1 and 153 mm yr -1 in thick and thin systems respectively, when the vegetation component was removed in the simulation, as compared to 16.7 mm yr -1 and 23.8 mm yr -1 when the vegetation component was included in the simulation. Furthermore, the percolation rates in phytocapping systems (with vegetation) were much less than those expected of a clay capping system. Since the phytocapping systems are effective, they halve the cost of construction (compared to clay capping) and provide other environmental benefits, their use is recommended in low (
Centre for Plant & Water Science 2008 Annual Report Vegetation component removed in the simulation Vegetation component included in the simulation Figure 1: Comparison of site water balance in thick and thin capping systems under non-vegetated (top) and vegetated (bottom) scenarios. Note the differences in Y axis values in vegetated and non-vegetated scenarios. The simulation was based on 15 years (1992 to 2006) of rainfall data. Fig 2. Luxurious growth of bamboo on a phytocapped landfill PROJECT STAFF Principal Investigators: Assoc. Prof. Nanjappa Ashwath Kartik Venkatraman Co-Principal Investigator: Dr. Ninghu Su Others Craig Dunglison & Richard Yeates FUNDING Qld Dept of Premier and Cabinet - Growing the Smart State Grant & CQUniversity INCOME $7,136 42
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Centre for Plant & Water Science - Central Queensland University

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