Abstract
The procedure was developed to assess the effect of soil heterogeneity
on transport of dissolved contaminants in saturated zone. The method is
presented by a case study from the Helsinki area. The study area is situated
in a clay filled valley formed in the end of ice age about 10 000 years ago.
The topograghy of the area is flat besides the northern side which consists
of moraine hills. The valley itself has a deposition of clay which can be
over 9 m thick. Under the clay deposit there is almost 10 m thick layer of
silt, sand, gravel and moraine. All main units are very heterogeneous
consisting of several thin layers of different types of soil reflecting the
historical stages of the current Baltic Sea. The geological 3D model was
created by using geotechnical drilling data and the known geological history
of these Quaternary deposits. The associated uncertainties were defined by
using geological inference and geostatistical simulation. There were seven
ground water pipes installed at the subarea of 240 m length and 90 m width to
measure in situ velocities, groundwater levels and electric conductivity of
water with depth. The analysed maximum concentration of trichloroethane
(TCE) was 1111 g/l and tetrachloroethane 207 g/l. Altogether 95 flow velocity
measurements with 20 cm measurement section were performed systematically
in the screen section of ground water pipes. The hydraulic properties for
different soil layers were inferred from these measurements. The
uncertainties from the geological model were combined with the uncertainty of
inferred hydraulic properties for soils. The effect of soil heterogeneity on
TCE transport was then studied by solving the flow and transport equations
for series of equally likely 3D realizations of hydraulic properties by
numerical heat and multiphase multicomponent flow code T2VOC (Falta et al.,
1995) and analytical code REMChlor (Falta et al. 2006). Uncertainty in
transport predictions has been characterized by frequency distribution formed
on the quantity of mass arriving on the exit location as a function of time
and TCE concentration distribution maps with uncertainty estimates. The
statistic of mass flux has been used as input to risk assessment.
| Original language | English |
|---|---|
| Title of host publication | 33rd International Geological Congress |
| Place of Publication | Oslo |
| Publisher | Norwegian Academy of Science and Letters |
| Pages | 3381 |
| Number of pages | 1 |
| ISBN (Print) | 978-1-62748-373-5 |
| Publication status | Published - 2008 |
| MoE publication type | Not Eligible |
| Event | 33rd International Geological Congress 2008 - Oslo, Norway Duration: 6 Aug 2008 → 14 Aug 2008 |
Conference
| Conference | 33rd International Geological Congress 2008 |
|---|---|
| Country/Territory | Norway |
| City | Oslo |
| Period | 6/08/08 → 14/08/08 |