Introduction into the environment of elements (such as arsenic, cadmium, lead, and mercury) which have a deleterious effect on living organisms when found naturally in only minor amounts (concentrations less than 1.0 milligram per liter) in water or sediment.
Arsenic and boron were the trace elements that most frequently occurred at high concentrations. Fumigants (pesticides) were detected at high concentrations in 3% of the primary aquifers. Herbicides and insecticides were detected at low concentrations.
Recent study indicating inorganic constituents as the primary items of concern in this area. Chemical and mineralogical compositions of the aquifer rocks probably explain variation among localities here.
Coordinated studies of the effect of historical mining for mercury, origin and composition of metals in groundwaters and surface waters, history of volcanic and intrusive activity, and the complex geological history of this area.