Do local releases cause global effects?
Mercury moves from the Earth’s crust into the biosphere as a result of both natural processes and human activities. Examples of natural processes include the weathering of rocks and volcanic activity. Human activity can release mercury • when it is intentionally mined, processed or used in products; • unintentionally, from processes where mercury is an unwanted impurity in raw materials, minerals and fossil fuels, particularly coal; and • from soils, sediments, water bodies, landfills and waste or tailings piles, contaminated previously by human activities. Once released, mercury enters the air, water and soil and can continue to move between them over long periods of time, depending on its chemical form (see section 1.3). Mercury is only removed from the biosphere when it reaches sediments deep under the oceans or when it is immobilised in controlled landfills. This implies that, even as we gradually eliminate mercury releases from human activity, levels in the environment will take s
