Mercury news roundup – Hg in snakes, Hg in fish, and Hg emission from forest fires and artisinal gold mining
July 16th, 2010
- High Mercury Levels Found in Burmese Pythons living in the Everglades
- Large fires may contribute to mercury in fish in southwest Colorado
- US Fish Mercury Concentrations Decrease in the 1970s and 80s; Recent Trends Show Variation
- Mercury levels increasing in popular species of game fish in Lake Erie
- Mercury found in fish from San Francisco water supply
- Mercury poisoning, the dark side of Colombia’s gold boom
High Mercury Levels Found in Burmese Pythons in the Everglades:
http://www.usgs.gov/newsroom/article.asp?ID=2546
Some invasive Burmese pythons have high levels of mercury, enough to merit concern from anyone interested in hunting them to eat, according to preliminary research by USGS researchers. Pythons are at the top of the food chain –they eat over 35 different species of mammals and birds, some of which are endangered and even alligators. As predators, these pythons are at a higher risk of mercury bioaccumulation because mercury builds up in organisms higher on the food web. One possible strategy to reduce the population of invasive pythons is to allow hunting; however, if the mercury content of the pythons is too high, the flesh of the pythons could present an unsafe level of mercury exposure to those humans who consume it. So far, the USGS Mercury Research Laboratory has analyzed over 50 python tail-tissue samples, with about equal numbers of adults and hatchlings. These results show that on average, tissue from the adults contained high levels of mercury, and the hatchlings were on average 22 times lower in mercury levels than their mother. An additional 100 samples are scheduled for further examination. This study, Mercury Bioaccumulation in Everglades Pythons, will be presented on July 15 in the afternoon poster session. For more information, contact David Krabbenhoft at 608-335-4234 or atdpkrabbe@usgs.gov
Researchers say large fires may contribute to mercury in fish in southwest Colorado
http://www.colorado.edu/news/r/6d84cd710276293086e23fd58d72e749.html
Forest fires that have burned thousands of acres near Durango, Colorado, over the last several years may be responsible for unlocking the mercury trapped beneath the soil in the San Juan National Forest and allowing it to wash into Vallecito Reservoir northeast of Durango, according to preliminary findings by a University of Colorado at Boulder engineering Professor, Joseph Ryan.
Vallecito is one of five reservoirs in the Four Corners region under fish consumption advisories due to elevated mercury levels in fish. The reservoir is used for recreational fishing, irrigation and water sports.
Coal-fired power plants in the Four Corners region are believed to be the primary source of mercury in La Plata and Montezuma counties. The mercury would be harmless if not for the sulfate-reducing bacteria beneath the soil that turns it into methylmercury, a toxic substance that is readily absorbed in the fatty tissues of organisms, according to Ryan.
When a large forest fire such as the 2002 Missionary Ridge Fire burns through an area containing mercury from atmospheric deposition, it appears to make matters worse by oxidizing sulfur molecules that bind the mercury in organic matter in the soil. This causes the mercury to be released and allows it to be more readily converted to methylmercury.
“We think the Missionary Ridge fire might have resulted in the fish consumption advisories for mercury that are now in effect at Vallecito Reservoir,” Ryan said.
For more information on the Colorado Fish Tissue study and fish consumption advisories, go to http://www.cdphe.state.co.us/wq/FishCon/index.html .
Fish Mercury Concentrations Decrease in the 1970s and 80s; Recent Trends Show Variation
A recent U.S. Geological Survey study examined a compilation of state and federal fish-monitoring data for trends in mercury levels in fish from 1969 to 2005 in U.S. rivers and lakes. Twenty-two of 50 sites sampled across the nation from 1969 to 1987 showed significant decreases in fish mercury concentration, whereas only four sites showed increases. Where decreases were observed, mercury concentrations in fish decreased rapidly in the 1970s and more gradually or not at all during the 1980s.
Trends were more variable from 1996 to 2005. Upward trends may, in part, be attributed to a greater influence of long-range global mercury emissions in the Southeast. In general, however, fish mercury concentrations did not change from 1996-2005. The report, “Mercury trends in fish from rivers and lakes in the United States, 1969-2005,” was published in the journal Environmental Monitoring and Assessment, and is available online with other materials.
This USGS study was implemented by the National Water-Quality Assessment Program, which was initiated in 1991 to support national, regional, state and local information needs and decisions related to water-quality management and policy. The NAWQA Program is designed to answer: What is the condition of our nation’s streams and groundwater? How are the conditions changing over time? How do natural features and human activities affect the quality of streams and groundwater, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities.
Chalmers et al, 2010, Environmental Monitoring and Assessment
Mercury levels increasing in popular species of Lake Erie game fish
OTTAWA — Mercury levels in a species of Lake Erie game fish are increasing after two decades of steady decline, scientists report. The joint study by researchers from the Ontario and federal government and the University of Toronto is the most comprehensive to date on mercury levels in Great Lakes fish, and was published in the journal ACS Environmental Science & Technology.
An analysis of the nearly 6,000 samples of lake trout and walleye collected from the lakes between the 1970s and 2007 showed that concentrations in the fish steadily declined in that period in the upper Great Lakes — Superior and Huron. But between 1990 and 2007, despite a levelling off of mercury concentrations in Lake Ontario walleye, contamination increased in Lake Erie walleye. Researchers hypothesize that the invasions of dreissenid mussels and round goby fish in the ecosystem contributed to the rise in Lake Erie mercury concentrations. Bhavsar et al (2010)
Mercury found in fish from S.F. water supply
Largemouth bass at Lower Crystal Springs Reservoir, which collects rainwater as well as water piped in from Yosemite’s Hetch Hetchy reservoir, had some of the highest mercury levels in California. The study was done by researchers at the San Francisco Estuary Institute, who released the results of the two-year project in June. They sampled sport fish at nearly 300 popular fishing lakes in California for methyl mercury, PCBs, DDT and other contaminants. Twenty-one percent of the lakes, including Crystal Springs, had at least one fish species with mercury concentration above 0.44 parts per million – a level considered unsafe for ingestion by young children and women of child-bearing age. However, the contamination doesn’t indicate that the water itself is unsafe.
At many of the lakes, the mercury results weren’t wholly unexpected. San Jose’s Almaden Lake, which had the highest fish mercury levels in the state, is in a geological zone rich with mercury, extracted during the 1800s for its ability to bind with gold. Fishing is allowed at Almaden, but signs in several languages warn against eating fish pulled from that lake and others in the area. To help control mercury levels at Almaden, the Santa Clara Valley Water District is aerating the water – adding oxygen to reduce the bacteria that mixes with mercury to form the toxic methyl mercury.
Mercury in the Crystal Springs area may be coming from a source other than local sediments, according to Jay Davis, senior scientist at the San Francisco Estuary Institute, and Tim Ramirez, manager for natural resources and land management at the San Francisco Public Utilities commission’s water enterprise division.
“It’s still possible that geology in the (Crystal Springs) watershed could contribute to the contamination we see, but it seems like a case where atmospheric deposition might play a role,” Davis said. “It’s not of immediate concern to people right now, but we want to know what’s happening,” Ramirez said. “That said, if it’s airborne pollution from a global source, that’s going to be hard for us to do something about.”
Mercury poisoning-dark side of Colombia’s gold boom
http://www.reuters.com/article/idUSTRE66C62L20100713
BOGOTA, July 13 (Reuters) – Colombia’s gold bonanza has a dark side, U.N. experts said on Tuesday: mercury poisoning spreading from miners to the population of a northwest state where they use mercury to extract the precious metal, U.N. experts said on Tuesday. Analysts say Colombia is one of the world’s top mercury polluters, as 50 to 100 tonnes of mercury are lost annually in the process of capturing gold .
“As prices of gold have been increasing, more artisanal miners are mining and processing gold using mercury which is accessible, easier and cheaper to use,” said Marcello Veiga, an adviser to the U.N. industrial development arm. Miners have used mercury to separate gold for decades, but part of it is lost in the process, contaminating rivers and soils. The environment ministry currently allows mercury but may soon forbid it, with a few exceptions.
In northwest Antioquia state, they use the most damaging process, adding around 120 grams (4.2 ounces) of mercury to 60 kilograms (132 pounds) of ore, without condensing or capturing the mercury, Veiga said. As a result, mercury levels in some urban areas of Remedios, Segovia and Zaragosa can be 1,000 times higher than the levels accepted by the World Health Organization, he said.
“Around 15 kidney transplants are carried out in Remedios every year … because mercury vapor stays in the kidneys, damaging them,” Veiga said, citing data from the Remedios department of health.
Colombia is experiencing a gold boom with more than 40 companies exploring for the metal and production likely to grow over the next two years to around 3 million troy ounces (93.3 kilograms) of gold, the mining regulator says. The United Nations calls for a gradual elimination of mercury in mining as miners switch over to use of centrifuges, which allow for greater gold extraction than mercury. “With the centrifuge, small miners can produce twice as much gold than using mercury without affecting their health or the environment,” said Monica Roeser, who leads the Global Mercury Project in Colombia for the United Nations.
