Elucidating the mechanisms utilized in phytotechnolgies and biochar immobilization to optimize contaminated site remediation

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Persistent organic pollutants (POPs) are recalcitrant contaminants known to cause a number of ecological and human health effects. Soil salinity is an escalating problem due to current agricultural practices and industrial processes, and is one of the major abiotic stresses that affect plant growth and yield. Similarly, contamination with petroleum hydrocarbons (PHCs) is at the forefront of many Canadians minds given the escalation in activity in the oil and gas industry in Canada in recent decades. Each of these contaminants can be addressed, at least to some extent, using innovative plant-based techniques known as ‘phytotechnologies’ (or phytoremediation). Phytoextraction is a specific phytotechnology whereby contaminants are taken up by plant roots, translocated to the shoots, and then sequestered in the above-ground plant tissue. Plants are then harvested and undergo biomass reduction (e.g. composting), with the goal being to significantly reduce the total volume of contaminated waste, while leaving the soil matrix intact. In the past six years, my group has made several significant advances in the area of contaminant phytoextraction, including the use of native colonizers. During the same time period, we have pioneered the use of biochar (a charcoal like material produced from the pyrolysis of organic matter under very low oxygen conditions) to decrease the bioavailability of contaminants in soils, reducing their risk to environmental and human health, and at the same time improving soil quality and decreasing CO2 emissions. These innovative techniques are now starting to be utilized more widely, however, a fundamental understanding of the processes involved in contaminant uptake into plants, and stabilization within soils is still lacking, as is the role that biochar plays in soil microbial communities and in the health of plants. This proposal will address these shortcomings and further our understanding of the mechanisms of phytoextraction. We will use methods developed by my group, such as measuring contaminants in the xylem sap of native plants at varying distances from the root. The application of community-level physiological profiling (CLPP) to obtain phenotypic information regarding microbial community function in contaminated soils alone, and those amended with biochar, is another innovative tool developed by my group. The novel use of these emerging techniques in combination with greenhouse trials employing real soil and plant systems will broaden our understanding of interactions between soil contaminants, plants, and the microbial community. Carrying out this critical phytoextraction work in combination with biochar amendment to the soil, will provide us with a deeper appreciation of the mechanisms involved in contaminant uptake and mobility within plants, and allow us to examine important changes in the microbial soil population. This will lead to our ability to also enhance the degradation of contaminants, in particular PHCs, in the root zone of phytoextraction plots. Hence, using established phytoextraction and carbon amendment immobilization techniques (combined with the emerging methods of xylem sap analysis, CLPP and biochar), this proposal will explore the efficacy of using these technologies simultaneously to remediate POPs-, salt-, and PHC-impacted sites. Ultimately, the goal of this work is to determine how phytotechnologies in conjunction with biochar can best interact to optimize contaminated site remediation. In so doing, these technologies will become more accepted and mainstream, providing contaminated site owners, government legislatures, and environmental consultants with the information they need to incorporate them into their ‘toolbox’ when remediating contaminated sites.