Importance of Environmental Black Carbon to Dissolved Petroleum Hydrocarbons Sorption on Soil

Abstract

Importance of environmental black carbon (BC) to sorption of dissolved petroleum hydrocarbons (DPH) on two soils with high BC:TOC ratios (33% and 11%, respectively) was evaluated at a relatively high concentrations (mg/L ∼ μ g/L range). Sorption isotherms of DPH were determined for the two original soils and soils combusted at 375°C (only BC). The sorption isotherms of the original soils were linear, whereas the isotherms of the combusted soils were highly nonlinear (n _F = 0.45, 0.60). It is indicated that intrinsic BC-water sorption coefficient is not possible to be used to estimate total sorption to the original soil, even in our relatively high concentrations. From the sorption isotherms, Freundlich coefficient of environmental BC sorption, K _F,BC ^env of 10 ^{2.55 ± 0.21} was calculated and could be used as a generic starting point for environmental modeling purposes. From the data, it could be deduced that BC was responsible for 50% of the total sorption at concentrations of 45 and 4 μ g/L (μ g/L range), which were significantly higher than literature concentrations (ng/L range). These results demonstrate that in soil with high BC:TOC ratio BC is the most important geosorbent constituent with respect to sorption of DPH at relatively high concentrations ranged in μ g/L.

Keywords:

• Sorption
• black carbon
• petroleum hydrocarbons
• soil

Acknowledgments

This study was financially supported by the National Basic Research Program of China (Project No. 2004CB418504).

Notes

^apH at equilibrium with 0.01 mol/L CaCl₂ and 200 mg/L NaN₃ at the soil-to-solution ratio used for isotherms

^bwhenever a standard deviation is measured in this table, n = 3

^ana, not applicable because non-BC OC was removed in combusted soils