These include sediment from the subsurface formation, microorganisms, and chemical precipitates that might form as a result of the disturbances brought about by the well. The concentrations of the dissolved and particulate substances are of interest because they can affect the water use or operation of the well. One of the most common considerations is whether the concentrations of constituents fall below levels mandated or recommended for drinking-water supply. Table 1 lists the maximum and recommended concentrations for common major, minor, and trace constituents naturally present in Dakota aquifer water. The concentrations are values listed by the Kansas Department of Health and Environment and were adopted mainly from the US Environmental Protection Agency.
Natural rainfall contains dissolved air and a very small amount of dissolved solids.
During the travel of rainfall through soil, sediment, and rock to reach an aquifer, the water dissolves additional solids. Most of the soluble solids picked up by the water are inorganic because inorganic minerals are the main component of soils, sediments, and rocks, and natural organic substances tend to be less soluble than common mineral salts. Water flowing deeper into the subsurface may encounter very soluble minerals such as rock salt and produce saltwater after dissolving the salt. Other deep subsurface waters can be highly saline because they were originally trapped seawater that has been further altered through geologic time. Bicarbonate may also be represented as alkalinity in some water analyses.