SR9080 - The Effect of Nutrient Availability on Biogeochemical Processes Affecting the Transport of Esherichia Coli in Soils

Researcher:

Danielle Fortin, Dept. of Earth Sciences, Univ. of Ottawa

Objectives:

To develop a predictive model that can be used to evaluate environmental risk associated with manure application.

Expected Benefits:

1. Will allow us to predict the rate and extent of bacterial adhersion to soil minerals unser several different biogeochemical regimes, which we can then apply to predict the speed and extent of E. coli transport through soils.
   

2. Will permit us to better delineate areas at risk of bacterial soil contamination, which will improve water quality and benefit rural Ontarians.
   

Summary of Research Results

The major findings of our research are as follows:

• Surface complexation models (SCMs) can describe all of the experimental titration data and zeta potential data for E. coli cells, quartz and iron oxide.
  

• The SCMs show that E. coli cells and quartz particles are negatively charged above pH 4, whereas iron oxide is positively charged below pH 8 and negatively charged above pH 8.
  

• The SCMs can be combined to predict the extent of E. coli adhesion to quartz and iron oxide. Adhesion of E. coli to the minerals is governed by electrostatic and chemical forces. Due to the electrostatic repulsion between the cells and quartz, no adhesion occurs in the range 4 < pH < 8. In contrast, due to electrostatic attraction, up to 70% of the cells in an E. coli suspension will adhere to iron oxide below pH 8.

The major deliverable of this project will be a predictive model that can be applied to determine the degree of bacteria-mineral adhesion in a variety of different biogeochemical regimes, and thus be used to evaluate the environmental risks associated with manure leaching. The use of this sort of predictive tool will not only allow us to reduce the risk of environmental contamination in Ontario, but it will also provide an economic benefit, in that costs associated with site remediation will be lessened.