Removal of aqueous-phase naphthalene by organically modified soils for use in permeable pavement technologies.

摘要

A method of protecting subsurface and surface water quality by enhancing a soil's natural retention properties of Polycyclic Aromatic Hydrocarbons (PAHs) contained in urban stormwater runoff was developed. This task was accomplished by increasing the organic carbon content in a typical Rhode Island glacial outwash soil using two amendment methods. The first method directly modified the soil with two types of quaternary ammonium cations through ion exchange reactions. The two cations used for modification were Hexadecyltrimethyl ammonium chloride (HDTMA) and Benzyldimethylhexadecyl ammonium chloride (BHDH). The second method consisted of blending a commercial organoclay with the Rhode Island glacial outwash soil. Soil modification results showed a 70% increase in organic carbon compared to the unmodified glacial outwash. To quantify the capabilities of the modified soils to sorb PAH a series of batch isotherms and column experiments were performed using naphthalene. Isotherm results were fit with the Langmuir and Freundlich linearizations and showed an average R2 of 0.96. All column intrinsic properties were determined using sodium chloride as a conservative tracer. Retardation factors of naphthalene in column experiments ranged from 52.3 for the unmodified soil to 406.3 for the commercial organoclay amended soil. R2 values for column regression equations averaged 0.88. These results showed that the increase of organic carbon in the modified soils enhanced retardation and sorption of naphthalene. Considering the modified soils were designed for application with permeable pavement technologies, the enhanced PAH sorption capacities suggest that organic carbon amendments would be beneficial to extend this type of best management practices for removing PAHs contained from stormwater runoff.