Developing plant-based strategies for the sustainable remediation of salinized soils

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Impacts of soil and freshwater salinization are widespread and substantial. The Food and Agriculture Organization of the United Nations estimate that ~6.5% of the world's arable soils are already saline or sodic. In this proposal, phytoremediation (using plants to remediate soils) is explored as a means of mitigating the harmful effects of salt at affected sites. Salt-tolerant plants known as `halophytes' are evaluated for their potential to remediate salinized soils and prevent leaching of salts into surface and ground waters. While most plants are sensitive to salt, halophytic plants have developed mechanisms to tolerate and thrive in these conditions. `Accumulator halophytes' sequester salts in their tissues, while `recretohalophytes' secrete excess salts through specialized glands on their leaf surfaces. Both types of plants are useful in the context of phytoremediation. In the former, plants must be harvested and the salt-contaminated biomass disposed of, while in the latter, salts may be dispersed on the wind in a process referred to as `haloconduction'. This proposal will study: i) accumulator halophytes to remediate road salt on motor ways, and ii) recretohalophytes for the broader remediation of industrially salinized soils. Canada currently leads the world in salt consumption, applying >5 million tonnes of road salt annually. Greenhouse and field studies will be employed to investigate native plant species for remediation of salinized roadsides, and will determine if the harvested salt-laden plant biomass may be repurposed into useable by-products (e.g. fodder, compost, or biochar). In theory, the use of recretohalophytes has an advantage over accumulator halophytes as excreted salt may be dispersed through wind action, thus removing the need for plant harvesting. Ironically, while salts are hazardous at high concentrations, low levels are essential nutrients for both flora and fauna species, and hence may prove to be beneficial when dispersed. The focus will be on exploring Canadian recretohalophytes with the goal of providing an alternative phytotechnology for remediating salt-contaminated sites that is feasible and sustainable, while also being low-cost and easy to implement. The integration of plants into any remediation design has the benefits of minimizing soil degradation, mitigating climate change through carbon storage in plant matter, creating habitat for native species, and improving site aesthetics. Findings documenting best practices will be published, ultimately putting a new environmental technology into the hands of Canadians. Over a 5-year period, this proposal will support and train 12 HQP. HQP will gain skills in critical thinking and planning, laboratory analytical techniques, field work organization and mobilization, and communication skills (both oral and written), all of which are actively sought after by prospective employers be they academic, industrial or private sector.