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How Global Change Will Impact Mercury around the World

How Global Change Will Impact Mercury around the World

Podcast:  Mercury and Global Change

Rising global temperatures and changing human actions will significantly affect the behavior and distribution of mercury worldwide, according to a recent article by the U.S. Geological Survey and Harvard University.

Mercury, especially in the form of methylmercury, is an extremely toxic chemical to all life forms. It occurs both naturally and as the result of human activities.  A majority of mercury releases to the environment presently are atmosphere emissions from human activities, and reemissions of previously deposited mercury from soils and the oceans. The largest sources of man-made mercury emissions are small-scale gold mining and burning coal for electrical generation.

“Studies like this help us better understand the overall effects of multiple impacts on the environment,” said USGS Acting Director Suzette Kimball. “We are just beginning to understand many of the consequences of global climate change and how interrelated many environmental issues truly are.”

Several seemingly unconnected aspects of climate change are expected to affect mercury at the global scale, according to the article.  In the atmosphere, higher temperatures and weaker air circulation patterns from climate change will likely have significant impacts on the atmospheric lifetime and patterns of mercury deposition.

In most climate change scenarios, storms will be less frequent but more intense, resulting in larger amounts of mercury being released from the soil through erosion that may end up in rivers, lakes and oceans, the study said.  When mercury reaches these surface waters, it can be processed by naturally occurring bacteria into the neuro-toxic methylmercury.

In addition, the article explained that climate change will likely lead to more frequent and intense forest fires, which release mercury from relatively stable and safe storage in the soil and allow it to be transported downwind and then redeposited and possibly converted into methylmercury.

“The intersection of the complex behavior of mercury in the environment with the myriad of aspects of global change provided a significant challenge to describe in this paper,” said USGS scientist David Krabbenhoft, the article’s lead author. “Although the science behind mercury research has exponentially increased in the past couple decades, providing reliable information to resource managers and decision makers on such complex topics remains a significant research challenge.”

Changes in human behavior will also have substantial impacts on global mercury, according to the article. Current human emissions of mercury total 2,000 metric tons per year. Under the best-case scenario of curbing human emissions and mitigating climate change, that number could fall to 800 metric tons per year by 2050. If no actions are taken and a business-as-usual approach is followed, the number will likely increase to 3,400 metric tons per year by 2050.

Human activity has already had a significant impact on the release of mercury emissions, the article explained.  For example, since the Industrial Revolution and widespread development of mercury emitting processes like coal combustion for electric power generation, soil records show a 3 to 5 fold increase in atmospheric deposition since the 1880s, and 7 to10 fold since antiquity. During the 20th century, coal-fired power plants dominated the human emissions of mercury.

However, with the current high cost of gold and relatively inexpensive liquid mercury, small-scale gold mining has taken over as the primary source of human emissions of mercury. Mercury is used to separate gold from rock deposits, and is often done in a manner that results in the miners and the local environment being exposed to toxic levels of mercury, according to the report.

Positive steps at controlling mercury emissions have been taken, though, Krabbenhoft noted. In 2011, the United States enacted the first-ever emissions regulations on coal-fired electricity-generating power plants. However, the United States only accounts for six to ten percent of global emissions.

To tackle global emissions, the United Nations Environmental Program brought together 140 countries to craft the Minamata Convention on Mercury, which is a binding resolution that includes emissions standards for mercury. It is scheduled to be signed in October, 2013.

USGS provides information on mercury sources; mercury cycling in the atmosphere, land surface, lakes, streams and oceans; and bioaccumulation and toxicity of mercury. This information helps land and resource managers understand and reduce mercury hazards to people and wildlife. Learn more about this article online.

USGS Newsroom

More information

Parameter Value Description
Magnitude mb The magnitude for the event.
Longitude ° East Decimal degrees longitude. Negative values for western longitudes.
Latitude ° North Decimal degrees latitude. Negative values for southern latitudes.
Depth km Depth of the event in kilometers.
Place Textual description of named geographic region near to the event. This may be a city name, or a Flinn-Engdahl Region name.
Time 1970-01-01 00:00:00 Time when the event occurred. UTC/GMT
Updated 1970-01-01 00:00:00 Time when the event was most recently updated. UTC/GMT
Timezone offset Timezone offset from UTC in minutes at the event epicenter.
Felt The total number of felt reports
CDI The maximum reported intensity for the event.
MMI The maximum estimated instrumental intensity for the event.
Alert Level The alert level from the PAGER earthquake impact scale. Green, Yellow, Orange or Red.
Review Status Indicates whether the event has been reviewed by a human.
Tsunami This flag is set to "1" for large events in oceanic regions and "0" otherwise. The existence or value of this flag does not indicate if a tsunami actually did or will exist.
SIG A number describing how significant the event is. Larger numbers indicate a more significant event.
Network The ID of a data contributor. Identifies the network considered to be the preferred source of information for this event.
Sources A comma-separated list of network contributors.
Number of Stations Used The total number of Number of seismic stations which reported P- and S-arrival times for this earthquake.
Horizontal Distance Horizontal distance from the epicenter to the nearest station (in degrees).
Root Mean Square sec The root-mean-square (RMS) travel time residual, in sec, using all weights.
Azimuthal Gap The largest azimuthal gap between azimuthally adjacent stations (in degrees).
Magnitude Type The method or algorithm used to calculate the preferred magnitude for the event.
Event Type Type of seismic event.
Event ID Id of event.
Event Code An identifying code assigned by, and unique from, the corresponding source for the event.
Event IDS A comma-separated list of event ids that are associated to an event.

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