Groundwater Pollution Week 1 – 0304 Introduction to Groundwater

Water in three states: liquid, solid (ice), and water vapor in the air Water in three states: liquid, solid (ice), and water vapor in the air. Clouds are water droplets, condensed from vapor-saturated air.

Water changes from one state to another Water changes from one state to another. So water can be solid, liquid or gas. Water also moves. We call this the Water Cycle.

http://ga.water.usgs.gov/edu/watercyclekoreanhi.html

http://ga.water.usgs.gov/edu/watercycleprint.html

cycle – 주기 circulation – move around something like a circle.

1.72, Groundwater Hydrology Lecture Packet 1 Prof. Charles Harvey http://ocw.mit.edu/NR/rdonlyres/Civil-and-Environmental-Engineering/1-72Fall-2005/4F444E12-8746-459D-A6BD-1F42F7498903/0/1_72_lecture_1.pdf

1.72, Groundwater Hydrology Lecture Packet 1 Prof. Charles Harvey http://ocw.mit.edu/NR/rdonlyres/Civil-and-Environmental-Engineering/1-72Fall-2005/4F444E12-8746-459D-A6BD-1F42F7498903/0/1_72_lecture_1.pdf

1.72, Groundwater Hydrology Lecture Packet 1 Prof. Charles Harvey http://ocw.mit.edu/NR/rdonlyres/Civil-and-Environmental-Engineering/1-72Fall-2005/4F444E12-8746-459D-A6BD-1F42F7498903/0/1_72_lecture_1.pdf

1.72, Groundwater Hydrology Lecture Packet 1 Prof. Charles Harvey http://ocw.mit.edu/NR/rdonlyres/Civil-and-Environmental-Engineering/1-72Fall-2005/4F444E12-8746-459D-A6BD-1F42F7498903/0/1_72_lecture_1.pdf

A lot of water is used for agriculture 56% is used by animals and plants 20% is lost when the water is moved 24% flows back into the stream or ground A lot of water is used for making electricity 87% of all industrial water use 1.72, Groundwater Hydrology Lecture Packet 1 Prof. Charles Harvey http://ocw.mit.edu/NR/rdonlyres/Civil-and-Environmental-Engineering/1-72Fall-2005/4F444E12-8746-459D-A6BD-1F42F7498903/0/1_72_lecture_1.pdf

Water can dissolve many things Water can dissolve many things. Water consists of two atoms of hydrogen and one of oxygen, which give it a chemical formula of H2O.

Water can dissolve at least small amounts of almost all substances that it contacts. Ground water usually contains the largest amounts of dissolved solids.

The composition and concentration of substances dissolved in unpolluted ground water depend on the chemical composition of precipitation, on the biologic and chemical reactions occurring on the land surface and in the soil zone, and on the mineral composition of the aquifers and confining beds through which the water moves.

The concentrations of substances dissolved in water are in units of weight per volume. In the International System (SI), the most commonly used units are milligrams per liter.

A milligram equals 1/1,000 (0.001) of a gram, and a liter equals 1/1,000 of a cubic meter, so 1 mg/L equals 1 gram m-3.

Because the concentration of most substances dissolved in water is relatively small, the weight per weight unit commonly used is parts per million (ppm).

Natural inorganic constituents commonly dissolved in water that are most likely to affect use of the water.

[    ]  Condensation [    ]  Evaporation [    ]  Evapotranspiration [    ]  Freshwater storage [    ]  Ground-water discharge [    ]  Ground-water storage [    ]  Infiltration [    ]  Precipitation [    ]  Snowmelt runoff to streams [    ]  Spring [    ]  Streamflow [    ]  Sublimation [    ]  Surface runoff [    ]  Water storage in the atmosphere [    ]  Water storage in ice and snow [    ]  Water storage in oceans [    ]  Desublimation [    ]  Plant uptake

Pollution of Groundwater  Pollution of ground water is any loss of quality of the water because of what people do.

Most pollution of ground water comes from the disposal of wastes on the land surface, in shallow holes including septic tanks, or through deep wells and mines; the use of fertilizers and other agricultural chemicals; leaks in sewers, storage tanks, and pipelines; and animal feedlots (excreta).

The size of any pollution problem depends on the size of the area affected and the amount of the pollutant involved, the solubility, toxicity, and density of the pollutant, the mineral composition and hydraulic characteristics of the soils and rocks through which the pollutant moves, and the effect or potential effect on ground-water use.

Affected areas range in size from point sources, such as septic tanks, to large urban areas having leaky sewer systems and numerous municipal and industrial waste-disposal sites.

Nearly all substances are soluble to some extent in water, and many chemical wastes are highly toxic even in minute (very small) concentrations.

Effects of Contamination Why do we care if there was only 1ppm (1/1,000,000) of a particular contaminant? It seems like too small of a number to matter.

With groundwater contaminants, both chemical and biological, a very small concentration of contaminant could still lead to serious health effects. Different kinds of contaminants have different concentration limits at which they start to effect us or the environment.

In dealing with groundwater contamination problems, it is necessary to find out both the specific type of contaminant and the concentration of the contaminant.

The concentration of different contaminants in the groundwater. Mr The concentration of different contaminants in the groundwater. Mr. Blue reacts in the same way a healthy person would to these chemicals. A person who is not as healthy, such as an older person or a small child, might suffer the effects even more. http://techalive.mtu.edu/meec/module04/ContaminationEffects.html

Which chemical needs to exist in the least concentration in the groundwater in order to avoid hurting someone?

Density The density of a liquid substance - that is, the weight per unit volume of the substance relative to that of water - affects its underground movement.

Densities range from those of petroleum products that are less dense than water other substances that are denser than water.

Substances less dense than water stay at the top of the saturated zone; if, like petroleum, they are immiscible, they will tend to spread in all directions as a thin film.

Substances denser than water tend to move downward through the saturated zone to the first extensive confining bed.

Contaminant Movement Contaminants can enter the groundwater by seeping in from the surface or by flowing in from another part of the aquifer. Once in the aquifer they move with the groundwater flow.

As contamination moves it disperses As contamination moves it disperses. This means that the concentration decreases as it moves farther away from the source of the pollution. For that reason there are different concentrations of contaminants at different points in the aquifer.

The mineral composition and physical characteristics of soils and rocks through which pollutants move may affect the pollutants in several ways.

If a pollutant enters the ground at a "point," it will be dispersed longitudinally and laterally in granular materials so that its concentration will be reduced in the direction of movement.

The visual representation of these different concentrations is called a contamination plume. How the plume looks depends on the type of contamination source, the specific contaminant(s), where the aquifers are located, and different soils in that area.

These animations show the two main categories of plumes based upon their source. Here are two animations of the Dispersal of a Pollutant from a Point source http://techalive.mtu.edu/meec/module04/OneTimePlume.html (Click Play) http://techalive.mtu.edu/meec/module04/ContinuousPlume.html (Click Play)

Organic Substances Organic substances and other biodegradable materials tend to be broken down both by oxidation and by bacterial action in the unsaturated zone.

Certain earth materials, especially clays and organic matter, may also absorb trace metals and certain complex organic pollutants and reduce their concentration as they move through the underground environment.

The hydraulic characteristics of the soils and rocks determine the path taken by and the rate of movement of pollutants.

Substances dissolved in water move with the water except when they are tied up or delayed by adsorption.

The movement of pollutants is most through the most permeable zones; the farther their point of origin from a ground-water discharge area, the deeper they penetrate into the ground-water system and the larger the area ultimately affected.

The movement of pollutants must be carefully considered in the selection of waste-disposal sites, animal feedlots, and sites for other operations that may cause ground-water pollution.

Here is an animation to allow you to Pick the Best Site for a New Well http://techalive.mtu.edu/meec/module06/WellSiting.htm