Controlling Power Plant Emissions
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Mercury is a global problem that knows no national or continental boundaries.
It can travel thousands of miles in the atmosphere before it is eventually
deposited back to the earth in rainfall or in dry gaseous forms.
Types of Sources
Worldwide Distribution of Emissions
The U.S. in the Global Context
Related Information
Types of Sources
Natural sources of mercury—such as volcanic eruptions and emissions
from
the ocean—have been estimated to contribute about a third of current
worldwide mercury air emissions, whereas anthropogenic (human-caused)
emissions account for the remaining two-thirds. These estimates are
highly uncertain. Much of the mercury circulating through today's
environment is mercury that was released years ago,
when mercury was commonly used in many industrial, commercial, and
residential products and processes. Land and water surfaces can
repeatedly re-emit mercury into the atmosphere after its initial release
into the environment. The pie chart below shows that anthropogenic
emissions are roughly split between these re-emitted emissions
from previous human activity, and direct emissions from current human
activity.
Source: Seingeur, 2004 and Mason and Sheu, 2002.
Worldwide Distribution of Emissions
Recent estimates, which are highly uncertain, of annual total global
mercury emissions from all sources, natural and anthropogenic, are about
4,400 to 7,500 metric tons emitted per year. The world map and the pie
chart below provide information about the worldwide distribution of mercury
emissions.
Source: United Nations Environment Programme Global Mercury Assessment, 2002,
using J. Pacyna 1995 data, as presented by the Arctic Monitoring and Assessment
Programme
Source: Presentation by J. Pacyna and J. Munthe at mercury workshop in Brussels,
March 29-30, 2004
The U.S. in the Global Context
U.S. anthropogenic mercury emissions are estimated to account for roughly
three percent of the global total, and emissions from the U.S. power
sector are estimated to account for about one percent of total global
emissions. (United Nations Environment Programme (UNEP). Chemicals, Global
Mercury Assessment, Geneva, 2002.).
EPA has estimated that about one third of U.S. emissions are deposited
within the contiguous U.S. and the remainder enters the global cycle.
Current estimates are that about half of all mercury deposition within
the U.S. comes from U.S. sources. However there are regional differences
in these numbers. For example, U.S. sources represent a greater fraction
of the total deposition in the Northeast because of the direction of
the prevailing winds.
Related Information
The Emissions Progress page presents information
about progress in reducing mercury emissions in the U.S. from all human-caused
sources.
The Controlling Power Plant Emissions: Decision
Process and Chronology page describes the history of regulatory
steps EPA has taken to reduce mercury emissions from power plants. |
