Nickel Bioavailability in Smelter-contaminated Soils: An Environmental Case Study of Port Colborne, Canada

Everhart, Jeffrey L.

MS

University Of Delaware

2003

Metal contaminants in soil environments derived from industrial pollution have clearly established the need for research on bioavailability and potential health risks. Much research has been conducted on metal sorption in soils. However, there is still a need to better understand the availability of metal contaminants to plants and microbes. Such information will enhance both human health and decisions about remediation efforts. In this study, Welland Loam (Typic Epiaquoll) and Quarry Muck (Terric Haplohemist) soils, from Port Colborne, Canada contaminated with Ni from smelter facility, that had been treated and untreated with lime, were employed in greenhouse and bioavailability studies. These soils varied in pH from 5.1 to 7.5, organic matter content from 6% to 72%, and total Ni from 63 to 22,000 mg/kg. Avena satifa, a nonhyperaccumulator, and Alyssum murale, a hyperaccumulating plant species, were grown in the greenhouse for 45 and 120 days, respectively, to determine Ni accumulation. A novel Ni bacterial biosensor technique was also used to determine Ni bioavailability and the results compared to those from the greenhouse study and more conventional, indirect chemical extraction techniques (employing MgC12 and a Sr(NO3)2). Results from the greenhouse, chemical extraction, and biosensor studies suggested that as the pH of the soil was increased with liming, Ni bioavailability decreased. However, the phytoextraction capability of Alyssum murale increased as soil pH increased, which was not the case for Avena sativa. Furthermore, the Ni bacterial biosensor was successful in predicting Ni bioavailability in the soils and suggested that higher Ni bioavailabilities occur in the soils at pH values of 5.1 and 6. The combination of plant growth, chemical extraction, and bacterial biosensor approaches are recommended for assessing bioavailability of toxic metals.