Groundwater Modeling Involving PRBs: General Aspects, Case Study - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 73

FIGURE 4.3
Local groundwater contours at the site in January 2010.
The simulation began with the contaminant plume, as interpolated from
the chemical analyses in March 2010. The vertical limit of the plume is
set uniformly at 6 m Australian Height Datum (AHD) based on the filter
screen positions of the wells. The highest TCE concentrations have been
measured in the wells with shallow filter screens, while concentrations in
the deep screened wells are negligible.
4.4.3 Reactive Contaminant Transport
When referring to reactive contaminant transport, it is important to distin-
guish between the TCE adsorption on naturally occurring organic matter
within the modeled area and TCE adsorption onto the reactive material
(Remat™) in the annular space of the extraction wells.
For the reactive contaminant transport within the model area, uniform
organic carbon content was defined as the mean of the measured con-
tents. For the adsorption, a linear sorption isothermal curve was assumed
(Henry Isotherm). From the organic carbon content (0.042%) and the K oc
value of TCE (adsorption on organic matter, 94), the distribution coefficient,
K D , is calculated. K D defines the ratio of dissolved TCE in the groundwater
and TCE adsorbed to the organic matter in the sediment (Equation 4.1). For
TCE in this aquifer it is 0.039 L/g. From the value of K D , the bulk density
(1.5), and the water content (0.1), the retardation factor, R, of TCE in the
aquifer is calculated. It defines how much more slowly TCE is transported
compared to a water molecule (Equation 4.2). The value of R for TCE at this