FANTASTIC METALS & WHERE TO PHYT THEM: Assessing the Potential of Metal Accumulation in Edible Garden Plants

University of Technology Sydney. Faculty of Science.Land contamination is a major threat to global food security. Heavy metals are ubiquitous contaminants contributing to agricultural land degradation across the globe. Their potential to cause serious harm to ecosystems and human health has led to the development of innovative remediation technologies. Harnessing the natural uptake ability of plants, phytoremediation offers an environmentally friendly, and cost-efficient method of remediating heavy metals from soils. Among known phytoremediators, many are plants with edible tissues, which can be deployed on degraded sites to promote decontamination. However, plants that accumulate high quantities of heavy metals into their edible tissues are a risk to food safety. With urban gardens in Sydney and Melbourne exceeding Australia’s Health Investigation Guideline level for heavy metals in residential soils, this thesis investigates the potential of edible plants in remediating legacy soil contamination in Australian environments and evaluates the associated risks of these species to food safety. A database analysis of edible phytoremediator plants from the literature identified a research gap of edible species tested under Australian environmental conditions. This study was followed by a germination experiment investigating single and multi-metal contaminant effects on the germination of eight commercially important crop species. Carrots were the only species able to germinate under complex multi-metal conditions inferring a greater risk to food safety if they continue to grow and accumulate metals in situ. In a controlled glasshouse experiment, mature root vegetable plants (i.e., carrots and radishes) posed the greatest risk to food safety, while common beans were found to accumulate appreciable concentrations of lead into brown leaf tissues compared to green leaves. These results present a possible avenue for the application of common beans as phytoindicators in lead-contaminated environments. Leafy herbs presented greater risk in a real-world investigation of homegrown produce from residences in North Sydney, NSW. In addition, a landmark field garden trailed on the heritage-listed White Bay Power Station, NSW, showed potential for phytoremediation using edible plants as a non-invasive, long-term strategy for contaminated industrial sites. The work presented in this thesis advances knowledge of the potential for edible plant phytoremediators to be used in Australian contexts with consideration of the associated risks to food safety. This research identifies crop species that pose lower or greater health risks based on edible tissue accumulation patterns. These findings inform species selection for the mitigation of risks to urban gardeners as well as providing candidates for future applications of phytoremediation in Australia