Phytoremediation of a Cement Kiln Dust (CKD)-Contaminated Landfill Using Halophytes

Abstract

Soil salinization is an environmental issue affecting global soil quality and plant productivity. Landfilling of cement kiln dust (CKD), a saline waste by-product from the cement manufacturing process, results in soil salinization, negatively impacting the physical and chemical characteristics of soil, and potentially affecting the health of plant and aquatic communities. Phytotechnologies were selected and implemented in an effort to remediate a CKD landfill located in Bath, ON. Halophytes are salt tolerant plants that make up ~1% of the world’s terrestrial flora and have been previously employed to remediate salinized soils. Objective 1: following the phytoextraction of chloride via a resident, invasive grass, Phragmites australis (common reed), aboveground biomass was harvested and placed in composters in a laboratory and directly at the field site. Significant reductions in biomass (28  6%) and reductions in chloride, with rinsing, (43.7  37.4%) were achieved in the laboratory, and significant reductions in both closed composters (87  6%) and in open compost piles (89  8%) were achieved at the field site, indicating that composting is a feasible alternative disposal method to landfilling and incineration of salt-contaminated plant material. Objective 2: recretohalophytes utilize specialized salt glands, which excrete salt onto their shoot surfaces. In a theory referred to as ‘haloconduction’, excreted salt has the potential to be transported away from the site of contamination via wind. Two native recretohalophytes, Spartina pectinata (prairie cordgrass) and Distichlis spicata (inland saltgrass), were selected to explore the theory of haloconduction in the field. Under ideal conditions, this study found that both species have the potential to remediate the site in 0.5 – 3.5 years. Three windborne salt collection methods were devised and implemented at the field site, and were able to confirm the transportation of salt via wind. Their continued use will be critical for establishing further understanding of the theory of haloconduction before a full-scale method of phytoremediation is established at the site. This thesis provides promising results for the use of phytotechnologies to remediate a salt-impacted CKD landfill that may be applied to other industrial sites, roadsides, or agricultural operations in the future.