Fate Pollutants in Subsurface Environments - Lecture 1

Vocabulary flashcards covering key terms and concepts from the lecture on Pollutant Fate and Transport in Subsurface Environments.

Porosity (\u03B7)

The ratio of the volume of voids (empty spaces) to the total volume of a material, calculated as Vvoids / Vtotal or 1 \u2013 (\u03C1b/\u03C1m).

Non-reactive tracer

A substance used to track water movement without undergoing significant chemical reactions or interactions with the surrounding environment.

Kd

Often refers to the distribution coefficient for sorption, representing the ratio of a contaminant adsorbed onto a solid to the concentration remaining in solution.

Capillary zone

The zone directly above the water table where water is held by capillary forces against gravity, filling some but not all of the pore spaces.

NAPL (Non-aqueous Phase Liquid)

Organic liquids, such as gasoline or solvents, that are not miscible with water but are sparingly soluble, and can exist as a separate phase in the subsurface.

Remediation

Approaches or methods used to clean up or mitigate contamination in the environment.

Saturated zone

The depth in the ground where all openings in soil or rock are completely filled with water.

Groundwater

Water found in the saturated zone beneath the Earth's surface, originating from rain and snowmelt that seeps into the ground.

Water table

The top surface of the saturated zone, which rises and falls with season and precipitation.

Baseflow

The portion of streamflow during dry periods that originates from groundwater discharge.

Losing stream

A stream that contributes water to the groundwater aquifer because the stream bed is higher than the surrounding water table.

Cone of depression

A localized lowering of the water table near a pumping well caused by the withdrawal of groundwater.

Area of influence

The land area above a cone of depression, where groundwater flow is altered by pumping from a well.

Hydrologic cycle

The continuous movement of water on, above, and below the surface of the Earth, involving processes like evaporation, precipitation, and groundwater flow.

Zone of aeration (Vadose zone)

The unsaturated zone above the water table, where pore spaces contain both air and water. It includes the soil-water zone, intermediate zone, and capillary zone.

Soil-water zone

The uppermost part of the vadose zone, where plant roots extract moisture and water content fluctuates with rainfall and evaporation.

Unconfined aquifer (Water table aquifer)

An aquifer that does not have a confining layer above it, where the top surface is the water table and the water level in a well is the same as the water table.

Confined aquifer

An aquifer located below a confining layer of solid rock or clay, where groundwater is usually under pressure.

Confining layer

A layer of solid rock or clay that restricts the flow of water, often found above a confined aquifer.

Artesian well

A well that penetrates a confining layer and draws water from a confined aquifer, where pressure causes the water to rise above the aquifer level.

Flowing artesian well

An artesian well where the pressure is sufficient to cause the groundwater to rise above ground level and overflow naturally.

Watershed

The area of land drained by a single river system, where groundwater in unconfined aquifers typically moves in the same direction as surface water flow.

CERCLA

Comprehensive Environmental Response, Compensation, and Liability Act, a federal law addressing hazardous waste sites.

RCRA

Resource Conservation and Recovery Act, a federal law that governs the disposal of solid and hazardous waste.

DNAPLs (Dense Non-aqueous Phase Liquids)

NAPLs that are denser than water and tend to sink through the aquifer until they reach an impermeable layer.

LNAPLs (Light Non-aqueous Phase Liquids)

NAPLs that are less dense than water and tend to float on top of the water table.

Advection

The process by which contaminants are transported with the bulk flow of groundwater.

Dispersion

The spreading of a contaminant plume due to variations in groundwater velocity at the pore scale and macroscopic heterogeneities, causing it to mix with uncontaminated water.

Retardation

A process, such as sorption (sticking to porous media), that slows down the movement of a contaminant relative to the groundwater flow.

Attenuation

A process, such as biodegradation, that reduces the concentration or toxicity of a contaminant in the subsurface.

Continuous contaminant source

A source that introduces pollutants into the environment over an extended, ongoing period.

Pulse contaminant source

A source that introduces pollutants into the environment as a single, discrete event or for a short, finite duration.

Discharge (Q)

The volume of fluid moving through a given cross-sectional area per unit of time (volume/time).

Velocity (q or flux J)

The volume of fluid moving per unit of time per unit of cross-sectional area (length/time).

Average linear velocity (v)

The actual average speed at which groundwater moves through porous media, calculated as flux (q) divided by porosity (\u03B7).

Darcy's Law

A fundamental hydrological law that describes the flow of fluid through a porous medium, stating that discharge is proportional to the hydraulic conductivity, cross-sectional area, and hydraulic gradient.