Phytoremediation of salt impacted soils

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The problem of elevated sodium chloride (salt) levels in soils is as important as petroleum contamination of soils for the upstream oil and gas industry. The remediation of salt impacted soils has proven difficult and costly due to the absence of a technology that is versatile and allows for in-situ or on-site remediation. Phytoremediation (plant-based bioremediation) offers many advantages over conventional removal or chemical-based remediation methods. Unfortunately, salt stress often leads to increased production of ethylene, a plant stress hormone, and results in diminished plant growth. Without high levels of biomass acceptable rates of remediation can not be achieved. Our recently developed multi-process phytoremediation system (MPPS) used for petroleum remediation has potential applications for remediation of salt impacted soils. A key feature of this biological system is the alleviation of plant stress by using plant growth promoting rhizobacteria (PGPR). These PGPR consume the precursor to the plant hormone ethylene, thus decreasing ethylene biosynthesis in plants. As a result, vigorous plant growth on salt impacted soils can be achieved, and should facilitate remediation of salt from the soil. In our pilot experiments, the PGPRs with the most promising results were two Pseudomonas putida strains (UW3 and UW4). These are the naturally occurring strains of PGPR that we currently use for petroleum remediation. They are on Environment Canada's list of safe and non-pathogenic microbes. In general, we are observing at least a 100 % increase in plant germination and total plant biomass attributable to PGPR. We have assayed for salt remediation in a greenhouse experiment. The results are inconclusive at this juncture. To accurately assess salt remediation we need more data and longer growth periods. This winter in the greenhouse, we will grow plants for longer time periods, allowing more remediation to occur within each experiment. In the Spring, we will proceed with field experiments at 3 salt-impacted sites in Alberta. These sites are associated with the upstream oil and gas industry, and have varying levels of salt contamination.