Date: September 9, 1999
To: RTDF Working Group for Phytoremediation at Petroleum Contaminated Sites
From: Jim Brown, Lockheed Martin/REAC & Royal Nadeau, U.S. EPA Environmental Response Team Center (ERTC), Edison, NJ
Re: Basis for Plant Materials Selection in Plant-Mediated Bioremediation1 at Petroleum Contaminated Sites
Selection of Suitable Plant Species
No single plant species can fulfill all these criteria; a mixture of cool and warm season grasses and legumes can. The advantage is a low-cost, low-maintenance, stable plant/soil system that also facilitates bioremediation of hydrocarbon contaminants.
Cool Season Grasses - quickly established, rapid top growth, growth during spring/fall (dormant in summer without water and nutrients), high nutrient requirement & root zone density within active treatment zone (0-6/12 inches), vigorous competitors under ideal conditions. Cool season grasses require high maintenance (i.e. regular additions of water and fertilizer).
Warm Season Grasses3 - slowly established (2 years), very deep rooted, bunchgrass characteristic, not vigorous competitors when soil moisture and nutrients are optimal; tolerant of drought and low nutrient availability. Once established, warm season grasses require little or no maintenance and tolerate marginal soil conditions.
EPA's Current Approach to Superfund Site Revegetation/Restoration
1The term 'plant-mediated bioremediation' is suggested rather than 'phytoremediation'; the latter term requires evidence of an active plant role in detoxification.
2Assumes insufficient research data currently available to select plant species based on demonstrated plant-mediated bioremediation effectiveness.
3Most drought-tolerant warm season grasses are deep-rooted, and require deep, well-drained soil. In arid and semi-arid regions, saline soils will develop under irrigation if soil drainage is impaired. Under these conditions, improvements such as tile drainage or deep ripping of compacted subsoils may be required. If soil drainage cannot be improved, salt-tolerant native grasses and shrubs may be most appropriate.
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