Final study terms (ground water)

Question 1

definition of unsaturated zone

Answer 1

air, water and soil. water is held in tension and is considered unavailable

Question 2

definition of water table

Answer 2

upper bound of the saturated zone

Question 3

definition of saturated zone

Answer 3

water and soil. water flows as groundwater

Question 4

definition of capillary fringe

Answer 4

up to 100% saturated but water is held in tension

Question 5

definition of aquifer

Answer 5

saturated layer that is permeable enough to allow water to flow fairly easily through it. water can be pumped out at an economical rate

Question 6

definition of aquitard

Answer 6

saturated layer that is not permeable enough to allow water to flow easily through it. water cannot be pumped out at an economical rate

Question 7

definition of artesian

Answer 7

confined aquifer with water that flows upward out of a well (no pumping)

Question 8

definition of perched

Answer 8

groundwater above a low permeability layer, usually above an aquifer

Question 9

definition of groundwater

Answer 9

the water contained in interconnected pores below the water table in an aquifer

Question 10

definition of groundwater flow

Answer 10

the movement of water through openings in sediment and rock; occurs in the zone of saturation

Question 11

different types of containment transportation

Answer 11

• advection: due to groundwater
• dispersion: due to irregular flow paths
• diffusion: due to concentration gradient

Question 12

What is advection (groundwater)

Answer 12

• movement due to groundwater flow
• contaminant (plume) moves with groundwater
• similar to a rubber ducky flowing on a river - it moves at the same speed as the river

Question 13

What is dispersion (groundwater)

Answer 13

• due to irregular flow paths
• micro, macro and mega scale dispersions
• smaller pores = higher velocity
• higher velocities = higher dispersion

Question 14

what is diffusion (groundwater)

Answer 14

• due to a concentration gradient
• contaminant plume moves from high concentration to low concentration
• important is low velocity souls (clays and bedrocks)

Question 15

how are dispersion and diffusion similar?

Answer 15

they cause the contaminant (plume) to move beyond what would have been expected with just advection alone

Question 16

what is sorption? (groundwater)

Answer 16

• refers to the property of a solute (dissolved) to either attach to the surface of a solid (adsorption) and/or then penetrate the solid (absorption)
• retardation causes the mean (average) contaminant velocity to be slower than the groundwater velocity

Question 17

definition of NAPLs

Answer 17

do not readily dissolve in water

Question 18

definition of LNAPLs

Answer 18

lighter than water

Question 19

definition of DNAPLs

Answer 19

denser than water

Question 20

definition of a non-aqueous phase liquids

Answer 20

• blobs, blebs, globules, ganglion, form as NAPL migrates through the subsurface
• immobile - not connected, do NOT flow
• long term source of groundwater contamination
• difficult to remove or remediate

Question 21

what are some groundwater remediation technologies?

Answer 21

• fluid pumping technologies (groundwater pump and treat, SVE, air sparging)
• mass destruction technologies (bioventing, oxidation, MNA)
• enhanced fluid pumping technologies (heat, steam, high vacuum, surfactants)
• enhanced bioremediation technologies (reactive zone, election donors)

Question 22

what happens during pump and treat?

Answer 22

• uses advective treatment methods to remediate contaminated aquifer (P&T) and vadose (SVE) zones
• advective methods rely on a fluid to move through the geology, have the contaminant transfer to the fluid, and then the fluid is brought above ground for treatment
• water and air have typically been those fluids

Question 23

remediation technologies: pumping

Answer 23

• NOT CONSIDERED A REMEDIATION TECHNOLOGY ANYMORE
• used as a hydraulic containment technology

Question 24

how are groundwater plumes controlled?

Answer 24

• hydrodynamic/hydraulic control
• extracted groundwater must be treated prior to release

Question 25

what is a disadvantage of groundwater P&T

Answer 25

- rebound (tailing)) occurs due to: - adsorption/desorption - back diffusion - NAPL ganglion - Heterogeneities

Question 26

what does SVE (soil vapour extraction) air flushing do for remediation?

Answer 26

- unsaturated zone - soil remediation

Question 27

what does AS (air sparging) air flushing to for remediation?

Answer 27

saturated zone - plume remediation

Question 28

what do PRBs (permeable reactive barriers do for remediation?

Answer 28

- passive interception and in situ treatment of dissolved contaminants in ground water

Question 29

what are the two different types of PRBs?

Answer 29

- passive ( no moving parts, no pumping, no on-going additives) - semi-passive (some maintenance activities, additives, etc.)

Question 30

what is ISCO and how is it used as a remediation technology

Answer 30

- Oxidation chemically converts hazardous contaminants to non-hazardous or less toxic compounds that are more stable, less mobile, and/or intert - oxidizing agents most commonly used are: (ozone, hydrogen peroxide, permanganate)

Question 31

when is ISCO used?

Answer 31

- used to remediate groundwater and soil - applicable to a variety of soil types and grain sizes (silts and clays) - applicable to treat (VOCs (PCE, TCE, DCE, BTE) - rapid destruction/degradation of contaminants - produces no significant wastes

Question 32

what is MNA (remediation technology)

Answer 32

- monitored natural attenuation "naturally-occurring processes in soil and groundwater environments that act WITHOUT HUMAN INTERVENTION to reduce the mass, toxicity, mobility, volume or concentration of contaminants in those media"

Question 33

when is MNA used?

Answer 33

- used as remedial alternative must be fully protective of human health and the environment - typically used in conjunction with active remediation of source zones (removal, treatment or containment) - use of MNA must be supported through scientific line-of-evidence approach - monitoring must continue until remedial objectives are achieved

Question 34

what is a reactive zone?

Answer 34

- created through injection of air, oxygen, O2 releasing compounds (ORC), etc - designed to treat or immobilize contaminants through biodegradation

Question 35

what is thermal remediation technology?

Answer 35

- soil or groundwater - heat can destroy or volatilize contaminants - in-situ technology - uncertainties related to uniform heating/treatment due of subsurface variabilities

Question 36

what are the different types of thermal remediation technologies?

Answer 36

- electrical resistivity heating - conduction heating - steam injection

Question 37

what is phytoremediation?

Answer 37

- uses plants to address contaminant issues - objectives can be for (containment and control, removal and destruction)

Question 38

what is phytoremediation applicable for?

Answer 38

- metals - pesticides - explosives - oils - solvents - can also prevent wind, rain, and groundwater from carrying contaminants off-site