Numerous hazardous pollutants are found in groundwater, including pesticides, metals and substances leaching from contaminated sites.

Metals in the groundwater. Depending on the soil type, inorganic trace elements, including metals, occur in groundwater in higher or lower concentrations. Metals occur naturally in groundwater, but lowering of the groundwater table and oxidation of metallic minerals can raise the concentration. High concentrations of metalloids, such as arsenic in the groundwater and drinking water, can be extremely harmful.

Source: EEA

Organic micropollutants that have been used in large amounts, or have been dispersed in the environment may also affect groundwater quality, in particular aromatic hydrocarbons and chlorinated solvents:

• The aromatic hydrocarbons typically derive from landfills, oil installations, petrol installations, asphalt factories, tar enterprises and gasworks.
• The chlorinated solvents mainly derive from the metals industry and the paints and dyes industry, landfills, petrol installations and dry-cleaning enterprises.

 
Salt (sodium chloride) is found in deep groundwater and in groundwater located near the coast. The presence of salt can restrict abstraction of water for drinking water. If water abstraction is excessive, intruding salt water can contaminate the groundwater. In addition, salting of roads during the winter can result in locally increased groundwater salt concentrations. Sulphate mainly occurs in areas where the ground contains sulphide minerals, and where lowering of the groundwater table promotes oxidation. Fluoride minerals are mainly found in limestone aquifers, where they can be released into the groundwater as fluoride.

 
Publications and links

EEA 2005: The European environment - State and outlook 2005. Part A: Integrated assessment, chapter 5 Freshwaters

EEA 2003: Europe's water: An indicator-based assessment. Topic report No 1

EEA 2000: Groundwater quality and quantity in Europe. Environmental assessment report No 3

Proposal for a Directive of the European Parliament and of the Council on the Protection of Groundwater against Pollution COM(2003) 550 final

Commissions DG environment homepage on the Nitrate Directives

WHO and CEC 2002: Eutrophication and health