Brownfields Remediation

I'm not one to follow a trend, but when it's a worthwhile trend such as the remediation of prime land (please see the current installment of The Ontario Agrologist Volume 2, Number 1, Spring 2006) I'm all for it.

The feature article is succint: prior industrial use in key strategic locations that were vacated before the induction of the Brownfields Statute Law Amendment Act (October 2004) continue to be unused because of contamination by industrial chemicals. Yet, these lands represent prime real estate because of their location, particularly since cities are expanding to encompass them.

There exist two principal means to remediate brownfields (so-called because the vegetation is sparse in these areas due to high concentrations of industrial pollutants). The first method is to remove the contaminated soil for transport to a landfill. The second method involves the remediation of the soil on the site, without removal of contaminated material.

The second option is the better of the two in my eyes. Why? Because with the "dig-and-dump" method, the problem is simply transferred to another location. Additionally, the logistics of containing the contaminants for transport adds to the bill. Transportation also adds risk to the remediation efforts, especially since vehicle accidents can cause toxic spills.

On-site remediation can be done using plants and microorganisms. Research done at the University of Guelph's Environmental Biology Department demonstrate the ability of several microorganisms (bioremediants) to degrade complex contaminants such as PCB's, hydrocarbons, and other toxic molecules. Plants have also been demonstrated, in association with symbionts such as mycorrhizas, to be able to take up significant levels of metals which can then be recovered in the vegetation after harvest.

There may be unforseen problems associated with using plants for brownfields remediation - not detrimental to the remediation efforts or containment of contaminants - not at all! I am referring to the possibility that the decreased ecological activity of soil microbes may actually make these lands breeding grounds for plant pathogens, or make the plants more susceptible to disease. Why would this be a concern - since the plants will be harvested, and they'll likely have a short lifespan anyways?

The answer lies in the efficiency of the brownfields remediation efforts. One has to remember that special equation: time = money. Efficiency can be measured as the amount of time it takes to remove the contaminants from the land. If plants get sick and die sooner than expected, the whole effort takes longer (a key aspect of using plants is that the longer the plant is in place, the more contaminants it will be able to remove from the soil), thereby adding to the bill.

To reduce this possibility, a clear plan to supplement additional soil microorganisms complimentary to the bioremediants and mycorrhizal symbionts will help to circumvent this issue. The addition of biological control agents (microorganisms with a proven antagonistic or preventative action against plant pathogens) to the foliage will help to maintain plant health.

Clearly, this regime would have to be carefully developed, but the various parts of the mechanism are already available. What needs to be developed is the practical application stage - taking the results out of the laboratory and applying them.