Solid & groundwater QM

• The major source of all fresh water drinking supplies in some countries is groundwater. Groundwater is stored underground in aquifers and is highly vulnerable to pollution.
• Understanding groundwater processes and aquifers is crucial to the management and protection of this precious resource.
• Groundwater comes from precipitation


  Precipitated water must filter down through the vadose zone to reach the zone of saturation, where groundwater flow occurs
• Vadose zone


  The material between the Earth's surface and the zone of saturation
• Surface pollutants must filter through the vadose zone before entering the zone of saturation.
• Subsurface monitoring of the vadose zone is used to locate plumes of contaminated water, tracking the direction and rate of plume movement.
• Infiltration rate


  A function of soil type, rock type, antecedent water, and time
• Aquifer


  A formation that allows water to be accessible at a usable rate. Aquifers are permeable layers such as sand, gravel, and fractured rock.
• Confined aquifer


  Has non-permeable layers, above and below the aquifer zone, referred to as aquitards or aquicludes. These layers restrict water movement.
• Perched aquifer


  A lens of non-permeable material found within more permeable material. Water percolating through the unsaturated zone will be intercepted by this layer and will accumulate on top of the lens.
• Unconfined aquifer


  Has no confining layers that retard vertical water movement.
• Artesian aquifer


  Confined under hydraulic pressure, resulting in free-flowing water, either from a spring or from a well.
• Water is continually recycled through aquifer systems.
• Groundwater recharge


  Any water added to the aquifer zone, including precipitation, streamflow, leakage (reservoirs, lakes, aqueducts), and artificial means (injection wells).
• Groundwater discharge


  Any process that removes water from an aquifer system, such as natural springs and artificial wells.
• Soil mass


  Consists of the solid particles and the voids in between them, which can be filled with air or/and water.
• The water table is actually a sloping surface.
• Hydraulic head


  The driving force that moves groundwater, combining fluid pressure and gradient, and can be thought of as the standing elevation that water will rise to in a well.
• Groundwater always moves from an area of higher hydraulic head to an area of lower hydraulic head.
• Porosity


  The fraction (or percentage) of void space in rock or soil.
• Permeability


  A measure of an earth material's ability to transmit fluid, expressed in terms of m/day (distance/time).
• Hydraulic conductivity (K)


  The ability of material to allow water to move through it, a function of the size and shape of particles, and the size, shape, and connectivity of pore spaces.
• Overpumping of groundwater will lower the water table, change the groundwater flow direction, and can lead to desertification in some areas.
• In many locations, groundwater withdrawal exceeds natural recharge rates, known as overdraft. In such areas, the water table is drawn down "permanently", so groundwater is considered a nonrenewable resource.
• Saltwater intrusion


  The interface between freshwater (groundwater) and saltwater in coastal areas, which can be affected by excessive pumping leading to cone of depression and cone of ascension of the interface.
• Soil and groundwater contamination/pollution


  The introduction of substances, biological organisms, or energy into the soil and/or groundwater, resulting in a change of the soil & groundwater quality, which is likely to affect the normal use of the soil and groundwater or endangering public health and the living environment.
• Common soil and groundwater pollutants


  • Petroleum hydrocarbons
  • Heavy metals
  • Pesticides
  • Solvents
• Sources of soil and groundwater contamination

  • Spills from pipelines
  • Accidental spills and seepage
  • Agricultural practices - excessive use of fertilizers and pesticides
  • Direct discharge of pollutant on soil surface
  • Leaks waste disposal sites (dumpsites and landfills)
  • Improper disposal of hazardous and other chemical wastes
  • Discharge from improperly operated or located septic systems
  • Leaking underground storage tanks (LUSTs)
  • Recharge of groundwater with contaminated surface water
  • Illegal dumping of wastes and disposal sites (leachate contamination)
  • Leaking retention ponds or lagoons
  • Saltwater intrusion
  • Usage of fertilizers and pesticides
• The more water soluble a chemical, the more likely it will travel down through the soil and into an underlying aquifer.
• Examples of naturally occurring groundwater contaminants


  • Arsenic
  • Fluoride
  • Selenium
  • Radon
  • Uranium
  • Nitrate
  • Nitrite
• Fluoride


  Can cause dental and skeletal fluorosis at high concentrations, guideline is 1.5 mg/L
• Selenium


  An essential trace element, but too much can cause loss of hair and fingernails, finger deformities, skin lesions, tooth decay and neurological disorders, guideline is 0.01 mg/L
• Arsenic


  Can cause skin and internal cancers, guideline is 10 ug/L
• Radon


  Emits alpha particles that can damage lung tissue, guideline is 100 Bq/L
• Uranium


  Long term exposure can lead to kidney problems, guideline is 15 ug/L
• BTEX (Aromatic Hydrocarbons)


  Benzene is highly carcinogenic, guidelines range from 10-700 ug/L for the different BTEX compounds
• Non-aqueous-phase liquids (NAPL)


  Liquids that are immiscible with water, associated with petroleum hydrocarbons
• Uranium


  Long term exposure can lead to kidney problems
• Uranium isotopes


  • 234
  • 235
  • 238
• Guideline for uranium in drinking water


  15 ug/L