TECHNICAL REFERENCE
CREOSOTE AND COAL TAR FILM FORMATION
In 2004, Journal of Contaminant Hydrology published an article by Alshafie and Ghoshal titled “The role of interfacial films in the mass
transfer of naphthalene from creosotes to water”. The authors demonstrated with pendant drop tests that viscous interfacial films form
in creosote-water systems after four days. Similar films were identified for coal tar-water interfaces by Luthy et al. (1993). In this
method, a DNAPL is expelled from a syringe immersed in water to form a drop at the syringe tip. Newly formed drops have a smooth
surface. For DNAPL drops that over time form a tar-water film, retraction of the aged drop results in textural changes (Figure 1).
Also, Alshafie and Ghoshal saw mass transfer of naphthalene decrease by 30% over a 1-week period in systems containing creosote and
water.
Benson (see CETCO TR-850) reported NAPL conductivity between creosote and CETCO Organoclay® of 7.6 x 10-10 cm/s. At a typical
NAPL head, it would take much longer than 4 days for tar to flow through Organoclay® Reactive Core Mat®. Thus, a tar film would be
expected to form at the tar-Organoclay® Reactive Core Mat® interface. The formation of this film may impede the movement of tar
through the Organoclay® Reactive Core Mat®.
This film formation may explain the long life of Organoclay® Reactive Core Mat® used to cap shoreline and sediment tar seeps. For
example, in Salem, MA an Organoclay® Reactive Core Mat® has been in place over a coal tar seep since 2006 without DNAPL
breakthrough.
REFERENCES
Alshafie, M. and Ghoshal, S., 2004. “The role of interfacial films in the mass transfer of naphthalene from creosotes to water”, Journal of
Contaminant Hydrology, 74 (2004) 283-298. http://www.sciencedirect.com/science/article/pii/S0169772204000579
Luthy, R.G., Ramaswami, A., Ghoshal, S., Merkel, W., 1993. “Interfacial films in coal tar non-aqueous-phase liquid–water systems”.
Environ. Sci. Technol. 27, 2914–2918. http://pubs.acs.org/doi/abs/10.1021/es00049a035
TR-856
TR_856_AM_EN_201401_v1
revised 11/12