Remediation of Cement Kiln Dust (CKD)-contaminated sites using excretory halophytes: Quantification, optimization and modelling of salt extraction and dispersion

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Soil salinization can occur due to industrial spills, the application of road salt, and the landfilling of high salt content industrial waste materials. Regardless of the mode of contamination, soil salinization is a growing problem both in Canada, where it is estimated that >7.2 million ha of soil are affected, and word wide. Soil salinization leads to the degradation of soil, reduces microbial activity, and diminishes plant growth. It can also lead to ground and surface water contamination. Common remediation strategies for salt-impacted soils including the application of chemical amendments, landfilling, and capping are typically very expensive, energy intensive, and destroy the soil matrix. The use of vascular plants to clean up contaminated sites (i.e. phytotechnology) is a low cost alternative to conventional remediation strategies, but has to date, not been exploited in salt-impacted soils. In this proposal, we employ salt-tolerant plants, known as halophytes, to take up salt ions from contaminated soil and either sequester them in the plant tissue, or excrete them through specialized salt glands. When salts are excreted on stem and leaf surfaces, they can theoretically be dispersed on the wind and redistributed across a large area. The theoretical dispersal of salt in this manner is referred to as 'haloconduction' in the scientific literature, but has never been demonstrated in laboratory or field trials. We propose to measure the dispersal of excreted salts using a variety of different techniques both at an industrial field site, and in the laboratory. This information will then be used to create a model of salt dispersion. Given that common salt ions such as K+ and Cl- are plant and animal nutrients, their dispersal over a wide area could actually benefit the environment. This research is important as it addresses the known and growing problem of soil salinization in Canada using a 'green technology'. Using plants to clean up salt-impacted soils improves the appearance of contaminated sites, decreases our reliance on more energy-intensive technologies, and reduces the amount of contaminated material going to landfills. Our results will provide site owners with a remediation strategy that is both 'environmentally friendly' and cost-effective.