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Putting Phytoremediation into Action

Researchers studying the use of bacteria and plants to remove toxins from the soil must better communicate their results if they want their techniques to be used by practitioners in the field.

Aug 1, 2015
Éric Montpetit, Erick Lachapelle

GREEN CLEAN MACHINES: A site near the city of Varennes, Quebec, where researchers on the Genome Canada project tested the efficacy of various willow cultivars to remediate soil polluted by petroleum hydrocarbons PHOTO COURTESY OF MICHEL LABRECQUE

Despite the enactment of comprehensive regulations, soil contamination remains widespread in much of the industrialized world. Researchers have estimated there are more than 160,000 sites in Western Europe alone that contain pollutants at levels above acceptable thresholds (J Environ Public Health, 2013: 158764, 2013), and the problem is just as significant in the United States (Environ Sci Technol, 39:5567-74, 2005). Owing to the cost of ex situ remediation, many contaminated sites are left untreated, allowing toxic chemicals to leach into nearby ground or surface waters and be taken up by plants and animals. Ultimately, soil contamination poses substantial risks for human health, and much work remains to significantly remediate lands that are known to be contaminated. (See “Drugging the Environment” here.)

Over the past 20 years, researchers have developed low-cost alternatives, such as phytoremediation, to clean up contaminated land. Although the strategy does not work well in all conditions, a growing body of work supports using bacteria and plants to stabilize, extract, and remediate a range of contaminants, including arsenic, zinc, and lead. Most recently, researchers have implemented transgenic manipulation and even electrokinetics to improve the efficacy of phytoremediation in particularly difficult sites. In a critical review, University of Birmingham environmental scientists Lesley Batty and Colette Dolan conclude that such techniques could represent a cost-effective and sustainable option for remediating contaminated sites (Crit Rev Environ Sci Technol, 43:217-59, 2013).

Despite this growing body of knowledge, however, phytoremediation is rarely used in the field. Conventional methods, such as excavation and off-site treatment, are much more common. In fact, in our search of the US Environmental Protection Agency (EPA) Superfund, we were able to identify only 50 cases between 1991 and 2010 in which phytoremediation was considered for treating the 1,620 highly contaminated sites on the National Priorities List, suggesting that the potential for bacteria and plants to remove toxins from soil may be substantially overlooked.

To examine the low use of phytoremediation methods, we surveyed nearly 100 accredited decontamination professionals in Quebec, Canada. These experts represent a group of individuals who play an important role in the selection of remediation technologies, as they consult on, approve, and monitor decontamination projects that occur in the province. The results reveal a surprising lack of knowledge about phytoremediation: on a scale of 0 to 10, more than 90 percent of the decontamination experts surveyed ranked their familiarity with this technique at 5 or below; none assigned themselves a score of higher than 8. When we validated this self-assessment with a series of four true-or-false questions, more than half answered fewer than two questions correctly.

The survey also suggested that knowledge of phytoremediation varied according to educational background. Chemists tended to score highest on the true-or-false questions, followed by biologists, geologists, and, lastly, engineers. With about four engineers working as decontamination professionals in Quebec for each chemist in the field, it’s not surprising that the industry as a whole has relatively little familiarity with the plant- and bacteria-based remediation strategies.

As a corollary, we also found that decontamination professionals in Quebec may be somewhat unreceptive to phytoremediation. For instance, fewer than 10 percent of our survey respondents had recommended phytoremediation more than once in the past. This mirrors the situation in the United States, where our EPA search revealed relatively few mentions of phytoremediation in the assessment of alternative clean-up methods. Our survey respondents also said they preferred conventional excavation and removal over phytoremediation, even when presented with a contamination profile most amenable to phytoremediation, as documented in the scientific literature. Of course, the survey also revealed that few decontamination professionals read such publications.

A key barrier to the employment of phytoremediation thus relates to informing and educating soil decontamination professionals working in the field. If practitioners are to make better use of the low-cost and low-risk potential of phytoremediation, researchers studying phytoremediation must make an effort to share their results. Most soil decontamination professionals get their information on decontamination alternatives from specialized conferences organized by practitioners and from newsletters circulated by their professional associations. Presenting research results in these media may serve to expedite knowledge transfer to practitioners, as heightened awareness of these techniques is likely to increase their use. Indeed, in a recent paper we published using our survey data, we found that the likelihood of accepting phytoremediation in the context of decontamination plans increases among decontamination professionals after they are exposed to scientific research on the conditions under which phytoremediation works (Environmental Politics, doi:10.1080/09644016.2015.1027058, 2015).

Much is made of the need for better science communication, usually in the context of needing to educate a scientifically illiterate public. But knowledge gaps can also occur between scientists and practitioners working in the same problem area. 

Erick Lachapelle and Éric Montpetit are assistant and full professors, respectively, in the University of Montreal’s Department of Political Science, Quebec, Canada.

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