A Wiki on Conductivity-Sensing is available on the Public Lab Website: https://publiclab.org/wiki/conductivity_sensing
[ Photo Credit: Stephen Gray estudiosdelafisica ]
Historical contributors to electrical conductivity theory include:
Stephen Gray (1666-1736) http://www.sparkmuseum.com/BOOK_GRAY.HTM
Benjamin Franklin (1706-1790)
Alessandro Volta (1745-1827)
George Simon Ohm (1787- 1854) André Marie Ampère (1775-1836) Sir Joseph John Thompson (1856-1940) http://science.jrank.org/pages/2321/Electrical-Conductivity-History.html
According to the U.S. EPA archive, "Conductivity is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium, iron, and aluminum cations (ions that carry a positive charge). Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity is reported as conductivity at 25 degrees Celsius (25 C)....The basic unit of measurement of conductivity is the mho or siemens. Conductivity is measured in micromhos per centimeter (µmhos/cm) or microsiemens per centimeter (µs/cm). Distilled water has a conductivity in the range of 0.5 to 3 µmhos/cm. The conductivity of rivers in the United States generally ranges from 50 to 1500 µmhos/cm. Studies of inland fresh waters indicate that streams supporting good mixed fisheries have a range between 150 and 500 µhos/cm. Conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates.** Industrial waters can range as high as 10,000 µmhos/cm."
The Community Science Institute (CSI) initiated a community science volunteer program, referred to as Red Flag Monitoring http://www.communityscience.org/volunteer/red-flag-monitoring/ along New York's Catatonk Creek and Cayuta Creek. "Red Flag volunteers test for five parameters: Temperature, pH, Dissolved Oxygen, Conductivity and Total Hardness. Conductivity and Total Hardness are specifically geared towards picking up impacts from shale gas waste. Conductivity is a measure of water’s ability to conduct electricity and is an excellent indicator for brine waste."
Public Lab, under the heading Water Quality Parameters https://publiclab.org/wiki/water-quality-parameters, also describes the significance of measuring water quality for variables such as electrical conductivity, pH, temperature and oxidation-reduction potential (ORP).
A detailed report published in Catchment News on August 13, 2017, entitled ["Catchments, water quality and community science – a tale from County Antrim](null)" provides an informative insight into a coalition between an academic institution, Queens University Belfast, and a community organization, Sixmilewater River Trust, who were concerned as a result of "Extensive pasture and associated drainage of wet soils, coupled with widespread intensive livestock rearing units, form a significant suite of potentially polluting agricultural activities, while other pressures on water quality can include (on-site and centralised) sewage disposal, urbanisation, landfills and manufacturing industry." The collaboration demonstrated that "Community science initiatives can have a range of benefits, including generating community support for conservation, providing local knowledge to researchers and offering additional human resources to assist in data acquisition."
The Sixmilewater River Trust community scientists conducted "seven rounds of Temperature/specific electrical conductivity measurements, made at 38 monitoring points across the 278km2 catchment during the eight week period, revealed specific electrical conductivity to vary from just under 55mS/cm to just over 200mS/cm." The volunteers utilized data loggers in 2015 and their results "revealed a gradual increase in specific electrical conductivity, corresponding to a decline in river discharge; this was interspersed with sharp declines (and recoveries) in specific electrical conductivity following periods of intense rainfall." Moreover, "Comparison of the results of specific electrical conductivity measurements with those of laboratory analyses revealed an excellent correlation with chloride concentrations." Review of the full article https://www.catchments.ie/catchments-water-quality-community-science-tale-co-antrim/ may provide some guidance to community science initiatives seeking to replicate the project in their own communities, plagued by analygous water quality vulnerabilities.