GROUNDWATER & WETLANDS

Inorganic Chemicals

Inorganic contaminants include elements and compounds that are released into the environment most often through mining, industry, transportation, and urban activities. Chloride, nitrate (NO₃), arsenic, lead, and uranium are some of the more common inorganic groundwater pollutants in Utah. Inorganic nutrients that are necessary for plant growth become pollutants when their concentration in groundwater and surface water becomes too high. The nutrient phosphate can be from geologic material, like phosphorous-rich rock, but is most often sourced from fertilizer and animal and human waste. Untreated sewage and agricultural runoff concentrates nitrogen and phosphorus which are essential for the growth of microorganisms. Nutrients like nitrate and phosphate in surface water can promote growth of microbes, like blue-green algae (cyanobacteria), which in turn use oxygen and create toxins (microcystins and anatoxins) in lakes.

Metals are inorganic elements or compounds that may contaminate groundwater. Lead, mercury, and arsenic are some of the more problematic inorganic groundwater contaminants. In Sanpete County, high concentrations of arsenic in groundwater may be associated with poultry farms. Other isolated elevated arsenic levels in Utah groundwater may be associated with volcanic rocks or volcanic-derived sediments in valley-fill deposits.

Mining can also cause significant inorganic contamination. Groundwater in parts of southwest Salt Lake County has been contaminated by seepage from a reservoir and evaporation ponds associated with the Bingham Canyon Copper Mine. The most severely contaminated groundwater in this area is acidic and laden with metals and very high TDS concentrations. Clean-up of the groundwater by the mining company is ongoing.

Salt, typically sodium chloride, is a common inorganic contaminant. It can be introduced into groundwater from natural sources, such as evaporite deposits like the Arapien Shale in central Utah, or from human activity-related sources like the salts applied to roads in the winter to keep ice from forming. Salt contamination can also occur from saltwater intrusion, where cones of depression around fresh groundwater pumping near saline lakes or the ocean induce the encroachment of saltwater into the freshwater body.