Tracer Hydrology

Front 1

flow

Back 1

movement of water

Front 2

transport

Back 2

movement of solutes by the flow

Front 3

advection

Back 3

net transport by the groundwater velocity (net center of mass at the linear velocity Vx)

Front 4

Dispersion

Back 4

molecular diffusion at very low velocities
-gradient transport - moves from area of high concentration to low concentration (causes spreading around center of mass)

Front 5

Dispersion is affected by -

Back 5

(1) pore size
(2) path length
(3) friction in pore

Front 6

the difference between surface and groundwater is -

Back 6

water-rock interactions

Front 7

hydrodyamic dispersion

Back 7

mixing caused by flow of fluids in porous media - it combines the effects of mechanical dispersion and molecular diffusion

Front 8

plume

Back 8

body of contaminated material downstream of a point source

Front 9

retardation

Back 9

movement of material through an aquifer that has been slowed (relative to groundwater flow) due to sorption processes.

Front 10

Rf

Back 10

retardation factor, relates the velocity of groundwater to that of material
-ranges from 1 to infinity

Vmat = Vx/Rf

Front 11

Sorption

Back 11

process of dissolved material attaching (adsorption) and detaching (desorption) from solid material such as mineral grains and organic matter

Front 12

level of adsorption can be affected by -

Back 12

the chemistry of the water (pH, redox potential)

Front 13

the Tail in a breakthrough curve can reflect -

Back 13

(1) retardation (in fast or slow path)
(2) slow paths
(3) diffusion into low K material

Front 14

How can you determine if the tail is determined by diffusion?

Back 14

conduct an experiment with 2 conservative tracers that have different diffusion rates

Front 15

specific conductance

Back 15

measure of dissolved salts

Front 16

What are the key features of a plume?

Back 16

(1) Material - (solutes, water quality)
(2) Velocity - (how fast it is expanding)
(3) Input function/Output function
(4) Gradient of concentration
(5) Spatial extent
(6) Dispersion (dilution)

Front 17

What are the five layers in a landfill plume (starting from the outside to center)?

Back 17

(1) Oxygen consumption
(2) Nitrate consumption (denitrification, nitrate to N2)
(3) Metals (Fe, Mn)
(4) Sulfate (SO4) production
(5) Methane (CH4) production (by methanogens)

Front 18

Shadow Plume

Back 18

what a plume would look like with a conservative tracer, is the last consumed products

Front 19

three phases of a plume:

Back 19

(1) Early - BTEX plume = smaller tan shadow plume (retardation)
(2) MIdterm - BTEX plume is at max length, microbes really start to consume plume at this point
(3) Plume shrinks - is relatively stable at certain length

Front 20

aerobic bio-barrier

Back 20

basically fill trench with gravel and PCV pipes that pump oxygen into groundwater
-provides oxygen for microbes to degrade pollutants

Front 21

Managed Aquifer Recharge is also known as -

Back 21

-groundwater banking
-artificial recharge
-aquifer storage and recovery (ASR)
-aquifer replenishment
-conjunctive groundwater/surface water banking
-bank filtration

Front 22

California Department of Public Health Water Reuse Rules -

Back 22

(1) pre-treatment of water
(2) dilution ( no more than 50% recycled water)
(3) minimum travel distance/tim between recharge area and production wells (500 ft/6 months)

Front 23

Hydrostratigraphy

Back 23

discontinuous layers of gravels, sands, and silts

Front 24

What are the benefits of using SF6 in tracer experiments?

Back 24

(1) non reactive synthetic gas
(2) easy analysis (gas chromatograph)
(3) background concentrations very low
(4) retardation is not important
(5) inexpensive

Front 25

What do two peaks in a breakthrough curve indicate?

Back 25

Two flow paths

Front 26

mean linear velocities

Back 26

velocities measured from the center of mass

Front 27

maximum velocities

Back 27

velocities measured from the first arrival

Front 28

aquifer

Back 28

rock/sediment that is saturated and sufficiently permeable to transmit economic quantities of water

Front 29

aquitard

Back 29

low permeability unit

Front 30

confined vs unconfined aquifers

Back 30

aquifers that are found between aquitards are confined, while unconfined aquifers have a free surface

Front 31

unsaturated zone

Back 31

(vadose zone) zone between the land surface and water table where some water may be suspended or moving

Front 32

water table

Back 32

the surface represent the transition between the saturated and unsaturated zones

Front 33

recharge zone

Back 33

area where water infiltrates into an aquifer

Front 34

recharge

Back 34

process of moving water across the water table

Front 35

permeability

Back 35

a measure of the ability of rocks to transmit fluids - property of an aquifer

Front 36

hydraulic conductivity

Back 36

a measure of the ability of a material to transmit water - property of both the aquifer and water (K)

Front 37

Porosity

Back 37

ratio of the void volume to the total volume

n = V(void) / [V(void) + V(grains)]

Front 38

piezometric (potentiometric) surface

Back 38

surface that represents the level to which water will rise in tightly cast wells

Front 39

Piezometer

Back 39

(monitoring well) a non pumping well, typically of a small diameter and short screen

Front 40

hydraulic gradient

Back 40

the change in water head (pressure) with distance (dh/dL)

Front 41

residence time

Back 41

t = (mass)/(summation of sources)
-small sources = slow replenishment
-large sources - fast replenishment

or

t = (mass)/(summation of sinks)

Front 42

artesian well

Back 42

pressure is so high that water comes up from the aquifer when drilled into (requires little or no pumping)

Front 43

groundwater age

Back 43

time since recharge

Front 44

recharge rate

Back 44

rate of transfer from soil to groundwater (across water table)

Front 45

The infiltration rate does not equal the recharge rate because -

Back 45

transpiration (plants) - some of the infiltration is used by plants, doesn't make it to recharge

Front 46

chemical hydrologic cycle

Back 46

changes before and after evaporation

Front 47

recharge is typically what percentage of precipitation?

Back 47

1% to 10%

Front 48

hydraulic head

Back 48

(h) specific measurement of water pressure above a datum, but is typically measured as water surface elevation (height from bottom of well)

Front 49

fractionation

Back 49

evaporation occurs at different rates for different isotopes of water, causes certain isotopes of hydrogen and oxygen to separate between pools (water vs atmosphere)

Front 50

isotopic fractionation factor

Back 50

(alpha) = Ra /Rb

Front 51

R =

Back 51

18O/16O or D/H

Front 52

delta units

Back 52

[Rsam/Rstandard - 1] • 1000%.

is a measure of a deviation from the standard ratio of two isotopes

Front 53

(delta18)O(liquid) - (delta18)O(vapor) =

Back 53

9.3 %

(Rayleigh's distillation model)

Front 54

evaporation occurs over the ocean at ____ humidity

Back 54

85%

Front 55

condensation occurs in clouds at ____

Back 55

100%

Front 56

global meteoric water line

Back 56

trend-line of precipitation observed globally.
(delta)D = 8((delta)18O) + 10

Front 57

evaporation changes the slope of the global metoeric water line :

Back 57

increases the ratio of (delta18)O to (delta)D.
changes slop from 8 to 3-7

Front 58

what are the three types of tracers?

Back 58

(1) radioactive isotopes (age based on decay laws)
(2) accumulating tracer (produced by radioactivity)
(3) Event marker (globally distributed compounds with known (historical) atm input functions)

Front 59

what is the uncertainty of CFC T/He dating?

Back 59

+/- 2 years

Front 60

which CFC degrades faster?

Back 60

CFC-11 degrades 10x faster that CFC-12
-results in CFC-11 ages older than CFC-12 ages

Front 61

what is the half life of Tritium?

Back 61

12.43 years