I Solute and Contaminant Transport

Question 1

advection

Answer 1

mass transport simply due to the flow of water in which the mass is dissolved

Question 2

change in conc over time is

Answer 2

the pore velocity

Question 3

contaminant plumes in the direction of flow

Answer 3

get broader and spread by diffusion

Question 4

Fick’s law qd

Answer 4

diffusive flux M/L^2/T

Question 5

Fick’s law Dw

Answer 5

molecular diffusion co in free water L^2/T

Question 6

tortuosity

Answer 6

dist a molecule must travel divided by the shortest dist between those points

Question 7

diffusion alone can not account for

Answer 7

the transport of chemical mass, as more spread than predicted

Question 8

mechanical dispersion

Answer 8

mixing that happens because the porous media forces some solute molecules to move faster than others (shorter pathways)

Question 9

longitudinal dispersion is bigger than

Answer 9

transverse dispersion

Question 10

molecular diffusion depends

Answer 10

solely on a concentration
gradient to operate, is
dominant at lower velocities

Question 11

mechanical dispersion
depends

Answer 11

on advection to
operate and dominates at
higher velocities

Question 12

mechanical dispersion alpha

Answer 12

dispersivity

Question 13

dispersivity

Answer 13

mixing parameter L

Question 14

matrix diffusion
if GW flow is slow,

Answer 14

solutes diffuse into lower permeability zones
as conc in the transmissive zone reduce, solutes diffusion back out
causing long extended tail of conc
mean its very hard to clean up contaminates

Question 15

Differential conduit recharge

Answer 15

Occurs under rapid flow conditions
driven by differences in pressure
between the conduit and the
adjacent matrix

Question 16

conservative contaiminants

Answer 16

does not react with
soil / aquifer solids, transport
controlled simply by dispersion
and advection

Question 17

reactive contaminants

Answer 17

sorbed into mineral grains
as well as organic matter, and change in concentration due to reactions or radioactive decay

Question 18

LNAPL light non aqueous phase liquids

Answer 18

Lighter than water so plume forms at water table
migrates down hydraulic grad

Question 19

DNAPL Dense non aqueous phase liquids

Answer 19

denser than water so sinks and pools at base of aquifer
migrate down the dip of aquifer

Question 20

radioactive decay

Answer 20

Radionuclides entering the groundwater system which are cations are subject to
retardation on soil surfaces
they undergo radioactive decay which reduces radionuclide concentration in BOTH dissolved and sorbed phases

Question 21

sorption processes include

Answer 21

absorption and adsorption
cation exchange -attraction between clay and cation minerals
chemisorption

Question 22

colloid

Answer 22

large particle that doesn’t settle

Question 23

Partition Coefficient

Answer 23

estimates contaminant retardation
partitioning of contaminant between solid and aqueous phase

Question 24

Ai for Partition coefficient

Answer 24

mass of absorbate sorbed

Question 25

Ci for Partition coefficient

Answer 25

mass of absorbate in solution

Question 26

partition coefficient (Kd) is small means

Answer 26

contaminant is very mobile

Question 27

Kd (partition coe) is large means

Answer 27

contaminant is immobile

Question 28

partition coe parameters

Answer 28

varies greatly between contaminants
sensitivity of contaminant to changing conditions not addressed
only valid conditions measured in

Question 29

diffuse sources

Answer 29

waste water, pesticides and fertilizers
much more difficult to deal with as over a larger area

Question 30

fully quantitative tracer tests requires accurate messurement of …

Answer 30

amount (mass) of tracer injected,
discharge from the spring or aquifer during the test, and
concentration or total mass of tracer in the discharging water.