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Over the past three decades, thousands of contaminated sites have been assessed and remediated through the EPA’s Superfund program, and many are currently on the program’s National Priorities List awaiting assessment and cleanup. Remediation of contaminated sites and spills is still a major concern in the U.S. and technology is improving to address needed cleanup. In the past, scientifically-proven methods of remediation generally involved engineered technologies, such as removal of materials to a landfill or pump and treat systems, which can be very costly. Technologies that utilize naturally occurring organisms to mitigate or remove toxic substances from soils and groundwater are increasingly being studied and employed on contaminated sites. These technologies, known as “bioremediation,” can offer advantages over conventional methods, including potentially lower costs and less transport of hazardous materials.
Bioremediation has been used to treat a number of organic and inorganic contaminants in the environment including hydrocarbons, chlorinated chemicals, pesticides, metals, and other contaminants. Various treatment methods may be used depending on the chemicals of concern, but most generally employ microorganisms to reduce toxic potential. Microbes, for example, can be applied to contaminated soils where they metabolize contaminants into less toxic forms (Donlon and Bauder 2015).
Phytoremediation, a similar kind of natural remediation, uses plants for decontamination and has demonstrated effectiveness at former mines and industrial sites. The method is attractive because it enables remediation at the site (in-situ) without transport of soils and can be performed at a relatively low cost. Plant species with faster relative growth are used to speed up the phytoremediation process. In particular, species of willow have been studied due to their rapid growth and premature foliation (Université de Montréal 2011). A recent study in Finland looked at the ability of different species of willow, with varying degrees of phytoremediation capacity, for remediation of heavy metals at a mine site (University of Eastern Finland 2014). The observed species which exhibited the best results was Salix schwerinii, as well as a hybrid of Salix schwerinii and Salix viminalis. These projects are helping to isolate the most efficient species of plants, as well as ideal proportions of microorganisms, to speed up site decontamination.
Although bioremediation is a well-known process, a number of studies are being performed aimed at making remediation potential faster and more effective, with fewer toxic byproducts. In the case of phytoremediation, the key seems to be identifying plant species that perform decontamination most effectively and expeditiously. Phytoremediation may have limitations however, which requires understanding of local conditions, including soils and local ecology to design effective remediation strategies. However, the potential for creating more cost-effective remediation that minimizes earth-moving is significant (University of Eastern Finland 2014) – not to mention the aesthetic benefits of a greener landscape.
About the Author
George Patten is an environmental scientist with experience in water quality assessments and watershed planning in Colorado. He has extensive experience assessing ecological and human health risks of contaminated soils, sediments, and groundwater. George also has a strong background in geospatial analysis, GIS, and other data visualization tools.