# Enviroment question

1. Mar 7, 2013

hi all
i am structural engineer, and i tok an enviroment course because the course options was limted
i have a question to solve but the problem i feel stupied because my back ground in this area is zero
the question is

A soil has a porosity of 0.23, a bulk density of 1.87 Mg/m3 and a permeability of 9.6 x10-8
m/s. It is being used as a clean-up barrier 450mm thick underneath a waste deposit that covers 50 x 120 m plan area. There is a hydraulic head of 1.8m across the barrier. If the contaminant concentration in the fluid which passes through the barrier is, initially, 125 mg/l, calculate how much contaminant escapes through the barrier in 30days. The partition coefficient is 25 l/kg. Ignore diffusion and dispersion effects in this case and assume that the thickness of the barrier acts uniformly.
Hints:
1) you will (probably1) need to calculate the ratio of the mass of solids to the volume of water in the soil.
2) you may consider the flow through the barrier as being a number of discrete transits, each comprising one bed-volume which suddenly replaces the previous bed-volume, waits without moving for the length of time indicated by the transit time, and then is suddenly displaced by the next bed volume.
3) I suggest you work out the contaminant that escapes for the first bed-volume; then work out the volume escaping in the second bed-volume. After that you will be able to set up a spreadsheet-based solution for as many bed-volumes as you need.

2. Mar 7, 2013

### Andre

It's not within my comfort zone but it seems to be covered well in a textbook,
"Earth Science: The Water Planet" issued by McGraw Hill, chapter 3 Groundwater.