Other groundwater sources

Electromagnetic (EM) Conductivity Measures the electrical conductivity of materials in microohms over a range of depths determined by the spacing and orientation of the transmitter and receiver coils, and the nature of the earth materials. Delineates areas of soil and groundwater contamination and the depth to bedrock or buried objects. Surveys to depths of SO to 100 ft are possible. Power lines, underground cables, transformers and other electrical sources severely distort the measurements. Low resistivities of surficial materials makes interpretation difficult. The top layers act as a shunt to the introduction of energy info lower layers. Capabilities for defining the variation of resistivity with depth are limited. In cases where the desired result is to map a contaminated plume in a sand layer beneath a surficial clayey soil in an area of cultural interference, or where chemicals have been spilled on the surface, or where clay soils are present it is probably not worth the effort to conduct the survey. 

From time immemorial, surface water played a pivotal role to human life as a source of drinking water because of its easy access compared with any other water source. A few decades ago, the use of contaminated surface water sources was found to contribute to the transmission of waterborne bacterial diseases. Thus, a paradigm shift in water usage from surface to groundwater was inevitable. 

Paerl, H.W. (1997) Coastal eutrophication and harmful algal blooms Importance of atmospheric deposition and groundwater as new nitrogen and other nutrient sources. Lirnnol. Oceanogr. 42, 1154—1165. 

Alkalinity has to be measured in the field because C02 is often pressurized in groundwater (due to addition of C02 from soil and other underground sources). Upon exposure to the atmosphere some C02 may leave the water, causing part of the HCO3 to break down. For these reasons it is highly recommended that alkalinity be determined in the field. Field-measured alkalinity values are needed for water-rock saturation calculations. Various setups are available for alkalinity measurements in the field by titration of the sample with an acid and pH coloring indicator. 

Groundwater is abstracted from many different types of aquifers, some of which may be highly susceptible to pollution as a consequence of human activity. The vulnerability of groundwater sources is important when assessing the risks to groundwater posed by various activities, Some aquifers are protected by one or more layers of impermeable material, such as clay, that lie above the saturated zone and that will prevent or retard the transport of chemicals from their sources to the saturated zone. Also, aquifers at certain depths may be protected from chemicals (even from some naturally occurring chemicals) that may be present at other depths in the geological profile. 

The Safe Drinking Water Act (SDWA) is designed to ensure that public water systems provide water meeting the minimum national standards for protection of public health. The act mandates establishment of uniform federal standards for drinking water quality, and sets up a system to regulate underground injection of wastes and other substances that could contaminate groundwater sources. (Surface water is protected under the Clean Water Act.)... 

In comparison with other groundwater pollution sources, the complexity of the source means that many different compounds (inorganic and organic) and processes (geochemical and microbial) will be interacting in a landfill leachate plume. 

Recall that only 0.6% of the hydrosphere is made up of liquid freshwater. Almost all of this freshwater is found as groundwater and other underground sources. Very small amounts (0.01%) come also from surface water such as... 

With few exceptions, most blind U deposits and other potential sources of He are situated below the water table, so that He must be released into the groundwater prior to its escape to the soil gas and the atmosphere. In consequence, groundwater, or at least groundwater as represented by water in drill holes and wells, has been sampled extensively as a means of determining the dispersion of He. Surface waters, however, tend to be equilibrated with the atmosphere and are unsuitable as sample media, except when collected from springs and at depth from lakes. 

In some cases the source of soil contamination is the soil itself. For example, soils rich in toxic elements such as arsenic, lead, mercury, and cadmium provide their own source of contamination. In addition, soils rich in uranium and its radioactive decay product radium provide continuous long-term sources of the radioactive gas radon in soil. The radon can diffuse from soil into the air of buildings or into groundwater, with resulting radiation exposures to human and animal populations. Other possible sources of contamination internal to soil itself are biological organisms, which are either themselves health threatening or which produce toxic chemicals. 

Other point sources of groundwater pollution include both deep injection wells and shallower dry wells used to inject chemical wastes (including radioactive waste) directly into the subsurface environment. While it is customary to make waste injections into deep aquifers that are salty or otherwise unusable for potable water, it is not unusual for injection wells to leak, or to force the flow of water from one layer of aquifer into another, resulting in contamination of an otherwise usable source of groundwater. 

Perdue, 1981) state, that soil is one source of stream humic substances or humic substance precursors, but to assume soil as the source or only source is exaggerated. To do so is to totally ignore other known sources / such as groundwater, decaying vegetation and litter, canopy drip, sewage, i and autochthonous material. 

---