Contaminant Risk Factors - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 352

TABLE 10.4
CRF GW for Select PAHs
PAH Compound

Soil Type GWCRF

Naphthalene Clay 0.0004

Silty clay 0.003

Sand silty clay 0.004

Sand 0.01

Chrysene Clay 0.000002

Silty clay 0.00002

Sand silty clay 0.00002

Sand 0.0009

Benzo[b]fluoranthrene Clay <0.00001

Silty clay <0.00001

Sand silty clay <0.00001

Sand <0.00001

Benzo[k]fluoranthrene Clay <0.00001

Silty clay <0.00001

Sand silty clay <0.00001

Sand <0.00001

Phenanthrene Clay 0.00002

Silty clay 0.0002

Sand silty clay 0.0002

Sand 0.0007

Benzo[g,h,i] perylene Clay <0.00001

Silty clay <0.00001

Sand silty clay <0.00001

Sand <0.00001

Benzo(a)pyrene Clay <0.00001

Silty clay <0.00001

Sand silty clay <0.00001

Sand <0.00001

Mean PAH CRF GW Clay 0.0001

Silty clay 0.0008

Sand silty clay 0.001

Sand 0.002

Source: Kaufman, M.M. et al., Water, Air, and Soil Pollut .,

167, 365, 2005; Rogers, D.T. et al., Assessment of
groundwater contaminant vulnerability in an
urban watershed in southeast Michigan, USA, in
Urban Groundwater—Meeting the Challenge , Howard,
K.W.F. (ed), Taylor & Francis, London, U.K., 2007a,
129-144.

Another characteristic gleaned from these data is the correspondence between the
increase in the risk factor for each contaminant and the increase in mean grain size from
clay to sand. Larger mean grain sizes increase permeability and raise the mobility fac-
tor, especially if a specific contaminant's physical chemistry has a high relative solubility
and low sorptive potential. If this relationship is correct, then contaminants with a high