Soil-Related Input Parameters for the Biosphere Model

This report presents one of the analyses that support the Environmental Radiation Model for Yucca Mountain Nevada (ERMYN), referred to in this report as the biosphere model. Biosphere Model Report (BSC 2004 [DIRS 169460]) describes the details of the conceptual and mathematical biosphere models and the required input parameters. The biosphere model is one of a series of process models supporting the postclosure total system performance assessment (TSPA) for the Yucca Mountain repository.
A schematic representation of the documentation flow for the biosphere model and its input to TSPA is presented in Figure 1-1. This figure shows the relationships among the products (i.e., analysis and model repqrts) developed for biosphere modeling, and the biosphere abstraction products for TSPA (based on BSC 2006 [DIRS 176938]). This figure is included to provide an understanding ofhow this analysis report contributes to biosphere modeling.
This report, Soil-Related Input Parameters for the Biosphere Model, is one of the: five analysis reports that develop input parameters for use in the biosphere model. This report is the source documentation for the six biosphere parameters identified in Table 1-1. Most of these parameters (partition coefficients, soil erosion rate, volumetric water content of soil, and irrigation duration) are only used in the surface soil submodel of the biosphere model for the groundwater exposure scenario and are associated with the accumulation and depletion of radionuclides in the . soil. These parameters support the calculation o f radionuclide concentrations in surface soil from on-going irrigation. The biosphere model for the volcanic ash exposure scenario does not consider radionuclide accumulation and depletion in surface soil. This is because the radionuclide concentration in surface soil is calculated :in the tephra redistribution model (BSC 2005 [DIRS 174067], Section 6.6) and is the source term for the calculations of dose from volcanic release of radionuclides Gust like the radionuclide
. concentration in groundwater is the source term for calculation of doses from radionuclide release in groundwater). The soil bulk density and enhancement factors are used in biosphere models for both exposure scenarios. Radionuclide concentration in surfac~::: soil affects radionuclide concentration in other environmental media, such as air, plants, and animals. The six parameters developed in this analysis are subsequently used as biosphere model inputs to calculate the biosphere dose conversion factors (BDCFs) for the biosphere groundwater exposure scenario and for the volcanic ash exposure scenario.