Protocol for the Derivation of Environmental and Human ... - CCME

Part C, Section 5
• K oc (sorption coefficient for soil organic carbon), K ow (n-octanol/water partition coefficient) or water
solubility data
• organic matter content and field capacity mass moisture content of the reference soil
• relevant water quality guideline
Normally, K oc data are preferred to K ow or S. If several studies are available, K oc should be estimated
from the geometric mean. Because the chemical and physical nature of organic matter affects the
magnitude of K oc measurements (Rutherford et al., 1993, Xing et al., 1994) it is necessary to restrict
candidate sources to those relevant to upland Canadian soils. Accordingly, data from sediments or
poorly humified organic materials (e.g., peats, forest floor materials) are not appropriate.
If K oc data are not available, tabulated K ow or S calculate K oc . A peer-reviewed regression that
explains at least 90% of the variation in log K oc should be used. Regressions prepared for groups of
related chemicals (e.g., monoaromatics, chlorinated aliphatics, PAHs) should be sought, and a minimum
residual sum of squares used to arbitrate among any competing models. K oc -predictive equations are
summarized in Dragun (1988), Lyman et al. (1991), and Mackay et al. (1992).
The organic matter content and mass moisture at field capacity are specified in "Evaluation and
Distribution of Master Variables Affecting Solubility of Contaminants in Canadian Soils" (Alder et al.
1994). Briefly, organic carbon content was chosen after considering:
• the range over which the linear partitioning isotherm holds,
• the range of organic carbon contents of Canadian soils and subsoils, and
• the goal of developing guidelines that would be protective at a majority of sites.
These considerations led to recommending the following conditions:
• organic carbon = 0.1%
• clay = 10%
Given these values, the field capacity, also called humidity percentage (0.03 MPa suction) value will be
approximately 0.1.
5.3.2.4 Acceptability of Soil Guidelines. On a generic basis, drinking water guidelines are the
appropriate source for groundwater quality to check the preliminary soil quality guideline derived in
Sections 5.1 and 5.2.
If the contaminant soil concentration determined through considering aquifer concentrations at steady
state with contaminated site drainage water is greater or equal to the derived preliminary human health-
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