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[T]he hypothesis that most Hg in Illinois and the USA soils is of anthropogenic origin is rejected. Chicago Tribune: Almost all the mercury that people are exposed to comes from eating fish. And almost all fish contain some amounts of the metal, much of which falls into oceans, lakes and streams from air pollution. Some of that pollution can travel around the world before falling to the ground. So emissions from a factory in China can pollute a lake in America and vice versa. Mercury also occurs naturally in rock and soil and is continually being released into the oceans through erosion and underwater volcanoes. In water, bacteria chemically alter mercury, creating a highly toxic form called methylmercury, which the tiniest fish eat or absorb. As bigger fish eat smaller fish, mercury accumulates up the food chain, with the largest predators, such as shark and swordfish, generally containing the most. (December 11, 2005) Response: Burying the Lead
Once CT finally came to bat discussing sources of mercury cycling through the environment, they fouled out to left field. Mixing metaphors, the weights of several scientific facts crumble the footings underlying their entire construction of industrial loading of MeHg to fish tissue. The principal fact is that annual total mercury entering the bio-sphere from natural sources dwarfs anthropogenic sources into near insignificance. Natural sources are not only immense and overwhelming, but are persistent over geological time. This stubborn fact has been resolute in the literature for decades, and doggedly ignored by mercury activists. Thus, readers are being misled about some of the most crucial science allowing for a rational policy approach to the issues. Mercury Deposition in Illinois
To verify this, CT would have had to look no further than to experts within their own state. Critical findings by Edward Krug and Derek Winstanley of the Illinois State Water Survey clearly show that man-made mercury from atmospheric deposition is a very small contributor to the huge amount of natural mercury already contained in the soils of Illinois specifically and the nation generally. After measuring mercury soil content, they estimated that it would take 9,000 years at current atmospheric deposition rates alone to account for all the mercury present in just the top 380-cm of Illinois soils. Similar analysis for a composite of U.S. soils yielded an estimate of 14,000 years of present atmospheric deposition required to attribute U.S. soil mercury content to man-made "air pollution." Krug and Winstanley made their point polar-star clear: “When widespread Hg pollution first became a popular concern, global anthropogenic Hg was compared to global soil Hg as part of a larger literature that criticized the common presumption that the principle source of Hg in the environment is anthropogenic. Regarding world soil Hg content, these early analyses reported that anthropogenic activities could have increased world soil Hg content by 0.02 percent. Despite this early seminal literature and a persistent stream of publications in following decades, the presumption that anthropogenic Hg is the principle source of Hg in the soils that mantle landscapes is still common and exerts a powerful effect on scientific and public perception of the role of anthropogenic atmospheric Hg deposition on the environment of Illinois and the USA. [In this work,] the hypothesis that most Hg in Illinois and the USA soils is of anthropogenic origin is rejected.” [Emphasis added] Accounting for Natural Sources Part of the earlier literature to which Krug and Winstanley alluded pointed out the critical importance of getting the natural/anthropogenic equation right. In a 1994 review paper , the researcher stated: “The most valuable information for assessing the impact of anthropogenic [mercury] activity is an understanding of natural processes.” Added Russian researchers: “The natural mercury emission from Earth’s Crust is an important factor controlling mercury distribution in marine water and atmosphere along with anthropogenic pollution. Main sources of mercury to seas are submarine volcanoes, mud volcanoes and cold gas vents.”  Some literature reviews estimate all-source natural contributions of mercury to the global environment in a range of 38,000 – 211,600 tons per year. This compares to estimated annual anthropogenic atmospheric contributions of around 2,700 tons. Likely the most reliable current estimates of natural mercury emissions (58,000 tons/yr) were recently reported by Mark Richardson of the Risklogic Scientific Service. Mercury sources included direct emissions from volcanoes, soil evasions, soil particles, plants, marine evasion, fire freshwater evasion, meteoritic dust and sea salt to the air -- all substantially underestimated by previous “best-estimates” utilized by EPA.  These important results (shown in Fig. 5-A), if proven correct, have serious implications for the efficacy of legislative and regulatory proposals aimed at removing mercury from the environment through mandatory reductions in emissions from coal-fired power-plants. (See discussion in Sec. 21)The above findings taken together with similar estimates by Richardson et al. (2003) for natural mercury emissions just in Canada and the US (shown in Fig. 5-B), pose reasonable questions concerning control of mercury in the environment. Momentarily setting aside issues of toxicology and epidemiology, even if 100% capture of man-made Hg emissions were technologically and economically feasible, would it make any difference in the persistent, historical levels of micro-trace MeHg present in fish? (See Fig. 5-A) Richardson addresses this question: “There is an on-going regulatory concern for metals [including Hg] in the environment, and numerous regulations have been implemented globally, or are being developed, to control or curtail industrial metal emissions. However, the relative contribution made by natural sources, versus those of anthropogenic origin, is typically ignored in environmental regulation, or dated publications are cited as evidence that natural sources are relatively insignificant. ... The primary citation concerning the contribution made by natural sources to environmental metal contamination remains Nriagu (1989). Volcanic degassing may serve as a significant source of ocean and atmospheric mercury. According to the Smithsonian Institution, there are well over 5,000 surface and submarine volcanoes in the world, with about 50 to 60 eruptions each month. Perhaps more important is the constant, non-event venting of mercury-laden heated water at seafloor vents, such as the black smokers in the Easter Pacific Rise. At Roaming Mountain, Wyoming, researchers measured mercury emanating from the clay hillside at up to 2,400 nanograms per square meter per hour. By comparison, background levels away from geothermal areas range from zero to 10! So, Hg emissions from active geothermal areas could range from tens to hundreds times more than from other background areas. At Yellowstone Lake, researchers have discovered submerged faults, explosion craters, domal features, hydrothermal vents, lava flows extending far out into the lake and much more. Therefore, it is hardly surprising that a report issued by the Idaho National Engineering and Environmental Lab showed that several places in Yellowstone Park emit higher levels of airborne mercury than power plants. Researchers estimated that Yellowstone could equal or exceed mercury emissions from Wyoming’s eight coal-fired power plants combined. Instead of reporting these findings, CT artfully wrote that “much” of the mercury that people become exposed to through fish ingestion comes from anthropogenic “air pollution.” The insinuated, false paradigm seems clear: natural sources of mercury are unimportant; remove the Hg from human activities, and one sufficiently removes MeHg from fish to make them “safe” again. From Hg to MeHg
Finally, CT touches on the bio-transformation of raw (Hg) mercury into methylmercury (MeHg). Again, the substance and relevance of the science is ignored. A fuller discussion of these issues follows in Sec. 21. Suffice it here to observe that it is a highly complex process; that the biochemical transformation of Hg into MeHg, and its ultimate bioaccumulation up the food chain, is not easily predictable. Neither is the process simply dependent on manipulation of raw Hg inputs, regardless of source or magnitude. To demonstrate this complexity and the uncertainty it introduces, following is a partial listing from the literature of variable and interactive conversion and transformation factors: (1) levels of MeHg are independent of raw Hg levels (Marvin-DiPasquale et al. 2003; Paller et al. 2004; Bonzongo & Lyons 2004) As a more local illustration of mercury cycling complexity facing would-be regulators, consider that quantitative estimates of elemental mercury revolatilization in the Great Lakes of about 2.3 to 13.7 tons per year. Estimated direct deposition of all species of mercury from the atmosphere is estimated at only 4.7 tons per year. This suggests the perplexing management accounting in which natural revolatilization output exceeds total input. |
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CT’s passive acknowledgment of mercury emissions from natural sources such as "underwater volcanoes," failed to follow Richardson’s strong counsel to consider the size and scope of dominant, natural sources. | < Prev | Next > |
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