Phytoremediation of Nitrogen Fertilizer Impacted Soil and Groundwater At An Industrial Plant Site.

In-situ remediation techniques such as plant-assisted remediation have shown promise as economical alternatives for reducing the risk of environmental contaminants at impacted sites. During the summer of 2010, research trials were initiated to determine the efficacy of plant-assisted remediation for soil and groundwater contaminated with high levels of nitrogen fertilizer at a fertilizer plant in Alberta, Canada.  Four plant types including alfalfa, willow, Okanese poplar and Saltlander grass were selected for phytoremediation experiments based on water use, rapid growth capability and tolerance to salinity. Experimental trials were conducted in environmental growth chambers, and all trials were carried out for a growing degree day period equivalent to an average growing season.  Initially, plant growth trials were conducted with soils artificially contaminated with varying levels of ammonium nitrate to determine the approximate upper limit of plant nitrogen tolerance. Following this, historically contaminated soil and groundwater containing high levels of ammonium, nitrate, phosphate and sulphate fertilizers was investigated using electromagnetic surveying, sampling and chemical analysis.  Using this data, samples were collected and growth chamber experiments designed to determine if plants could assist in the remediation of naturally occurring soils and groundwater contaminated with excess fertilizer.

Initial results indicate that plants can take up excess soil nitrogen caused by fertilizer contamination. Of the plant types selected, only Saltlander grass can survive in soils with up to 4000 mg/kg of ammonium nitrate. Plant-assisted remediation is potentially very effective under conditions where soils are contaminated by high concentrations of a variety of plant nutrients, as well as being economical, sustainable and aesthetically pleasing. The results of this research will be used to develop plant-assisted remediation programs at many western Canadian fertilizer facilities.