Arsenic in groundwater
Arsenic is a semimetal, or metalloid: its properties lie between those of metals and those of non-metals. It occurs naturally in the earth and in the seas. It is odourless and tasteless. Arsenic is an element (As) that occurs in the earth’s crust-rock, soil, all natural sources of exposure, or can be traced to deep water brines used to produce oil and natural gas. Environmental sources of arsenic stem from the continuing use of its compounds and pesticides, from its unintended release during the mining of gold and lead and from the combustion of coal, of which it is a contaminant. Industrial effluents also contribute arsenic to water in some areas. It is widely thought that naturally occurring arsenic dissolves out of certain rock formations when groundwater levels drop significantly. Surface arsenic-related pollutants enter the groundwater systems by gradually moving with the flow of groundwater from rains, melting of snow, etc. Drinking water, especially groundwater, is a major source of arsenic for most people.
Information about arsenic removal from water is available here.