Solution Exercise 2
Assume one-dimensional flow for the purpose of calculations and consider the rate of S consumption in a 1 L cube of aquifer material (10 cm x 10 cm x 10 cm).
Determine the amount of S in the 1 L aquifer cube which weighs:
We know S is 0.02 percent of the dry material by weight, so:
NO3––N flux through the cube is determined as follows.
From Equation 14, 1 M of NO3––N will consume 10/14 M S:
Given that there is 0.36 g S in each 1 L cube of aquifer, each cube has sufficient S to support autotrophic denitrification of a plume for 0.052 years as shown below.
= =
Thus, the NO3––N plume will advance 10 cm every 0.052 yr, or one could say it can consume all S from 19.2 cubes each year (1/0.052=19.2), which is a rate of NO3––N plume advance of 192 cm/yr. Another way to calculate the advance rate is as follows.