Bp. Wilcox et Dd. Breshears, INTERFLOW IN SEMIARID ENVIRONMENTS - AN OVERLOOKED PROCESS IN RISK ASSESSMENT, Human and ecological risk assessment, 3(2), 1997, pp. 187-203
Risk assessment, both human and ecological, embodies fundamental assum
ptions about hydrological processes, especially how they affect the mo
vement of contaminants in the environment. The lateral movement of wat
er through the soil, or interflow, is frequently a component of risk a
ssessments for humid environments, but not of those for semiarid envir
onments. Our research has shown that, contrary to what was previously
thought, interflow can be important in semiarid landscapes and is, the
refore, an essential consideration for risk assessment in these region
s. To illustrate and assess the effect of interflow on estimates of ri
sk, we (1) developed a simple conceptual model to describe the role th
at interflow may have in the redistribution of surface and near-surfac
e contamination, and (2) used RESRAD, an exposure model for assessing
radionuclide doses to humans, to evaluate the effectiveness of landfil
l covers in mitigating doses of three contaminants (H-3, U-238, and Pu
-239/240) at a site in northern New Mexico at which interflow is known
to be occurring. Only those calculations of the model that took inter
flow into account yielded the result that the radionuclides would cont
aminate groundwater - underscoring the potential importance of interfl
ow as a mechanism for the transport of contaminants. We conclude that
failure to take interflow into account can render risk assessments ina
ccurate and remediation ineffective. Further, our work demonstrates th
at a general understanding of hydrological processes is essential for
accurate risk assessment, ecological as well as human.