Seedling Emergence and Growth Can Be Improved by Char Carbon Created During Thermal Treatment of Petroleum-Impacted Soils

ABSTRACT

Thermal treatment of soils to remove petroleum hydrocarbons alters soil properties in ways that limit germination potential for plants used in revegetation efforts. However, recent studies have shown that a char material with the potential to offset fertility-reducing effects is produced by the pyrolysis of hydrocarbons during treatment. In this study, seedling emergence and growth (14 days) of two plant species, soybean (Glycine max) and oat (Avena sativa), were evaluated in four soils of contrasting properties treated with 5% (by mass) oil addition and two levels of salt addition. Three temperatures (300, 425, and 550°C) of thermal desorption (TD) and one smolder remediation approach were employed to remove the oil prior to planting. Results indicate that seedling response to temperature of thermal treatment and salt addition is dependent both upon plant species and soil properties. Higher temperatures were necessary to remove crude oil to levels low enough to allow germination. The smoldering approach did not remove enough oil to allow germination. This is the first study to show that early shoot mass and root mass are improved following TD treatment compared with an untreated control under certain conditions. The outcomes will be valuable for designing TD treatments when revegetation is the goal.

KEYWORDS:

• Carbon
• char
• germination
• thermal desorption (TD)
• total petroleum hydrocarbons (TPH)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Chevron U.S.A.