USGS claims that mercury and selenium are accumulating in the Colorado River

A study conducted by the U.S. Geological Survey (USGS) claims to have found “relatively high -compared with other large rivers” concentrations of mercury (Hg) and selenium (Se) in the food web along the Colorado River between Glen Canyon Dam and the Grand Canyon, The study was done in the summer of 2008, but curiously, results were just published in the journal Environmental Toxicology and Chemistry in August 2015. Perhaps they were taking advantage of publicity associated with the toxic spill from the Gold King mine in Colorado earlier this month.

USGS Hg Se study map

Some excerpts from the press release:

“The study, led by the U.S. Geological Survey, found that concentrations of mercury and selenium in Colorado River food webs of the Grand Canyon National Park, regularly exceeded risk thresholds for fish and wildlife. These risk thresholds indicate the concentrations of toxins in food that could be harmful if eaten by fish, wildlife and humans. These findings add to a growing body of research demonstrating that remote ecosystems are vulnerable to long-range transport and bioaccumulation of contaminants.”

“The study examined food webs at six sites along nearly 250 miles of the Colorado River downstream from Glen Canyon Dam within Glen Canyon National Recreation Area and Grand Canyon National Park in the summer of 2008. The researchers found that mercury and selenium concentrations in minnows and invertebrates exceeded dietary fish and wildlife toxicity thresholds.”

“Although the number of samples was relatively low, mercury levels in rainbow trout, the most common species harvested by anglers in the study area, were below the EPA threshold that would trigger advisories for human consumption.”

See full paper: http://onlinelibrary.wiley.com/doi/10.1002/etc.3077/epdf

From the paper:

“Sampling occurred from 12 to 28 June 2008. At each site, we collected representative basal resources (organic matter and primary producers), macroinvertebrates, and fishes. Basal resources included fine benthic organic matter, seston (suspended organic matter), epilithon (benthic biofilm), attached algae (Cladophora sp.), and epiphyton (diatoms attached to Cladophora). We collected fine benthic organic matter from sandy depositional habitats using a Ponar dredge (0.052 m2 ) deployed from a boat.”

As far as I can determine, the study analyzed fewer than 25 samples of each group along 250 miles of river. That is indeed a very low number upon which to form conclusions.

“In the present study we found no significant differences in Hg and Se accumulation among sites throughout the Grand Canyon.”

“There is a well-documented antagonistic interaction between Se and Hg, whereby Se protects animals from Hg toxicity when Hg:Se molar ratios are approximately 1 or less. The Hg:Se molar ratios were typically much lower than 1 in the present study, ranging from 0.04 (rainbow trout) to 0.38 (fathead minnow) among fish species. Assuming that Se and Hg in prey are equally transferred to consumers, this large excess of Se in this system suggests that the risks of Hg toxicity could be considerably lower than the Hg wildlife risk values alone would indicate.”

From the press release:

“The good news is that concentrations of mercury in rainbow trout were very low in the popular Glen Canyon sport fishery, and all of the large rainbow trout analyzed from the Grand Canyon were also well below the risk thresholds for humans,” said one of the study authors.

“We also found some surprising patterns of mercury in rainbow trout in the Grand Canyon. Biomagnification usually leads to large fish having higher concentrations of mercury than small fish. But we found the opposite pattern, where small, 3-inch rainbow trout in the Grand Canyon had higher concentrations than the larger rainbow trout that anglers target.”

Regarding mercury: “Airborne transport and deposition — with much of it coming from outside the country — is most commonly identified as the mechanism for contaminant introduction to remote ecosystems, and this is a potential pathway for mercury entering the Grand Canyon food web.” Selenium is derived from “irrigation of selenium-rich soils in the upper Colorado River basin contributes much of the selenium that is present in the Colorado River in Grand Canyon.”

The paper abstract notes that “consistent longitudinal patterns in Hg or Se concentrations relative to the dam were lacking.” That would seem to cast in doubt the proposed source of selenium from upstream irrigation of agricultural land. The “relatively high” concentrations they were talking about in fish are 0.17–1.59 ppm Hg and 1.35–2.65 ppm Se.


Hype about Mercury in the oceans

“A new paper by a group that includes researchers from the Woods Hole Oceanographic Institution (WHOI), Wright State University, Observatoire Midi-Pyréneés in France, and the Royal Netherlands Institute for Sea Research appears in this week’s edition of the journal Nature and provides the first direct calculation of mercury in the global ocean from pollution based on data obtained from 12 sampling cruises over the past 8 years. The work, which was funded by the U.S. National Science Foundation and the European Research Council and led by WHOI marine chemist Carl Lamborg, also provides a look at the global distribution of mercury in the marine environment,” says the press release.

 What made headlines in the press is this: “Analysis of their results showed rough agreement with the models used previously—that the ocean contains about 60,000 to 80,000 tons of pollution mercury. In addition, they found that ocean waters shallower than about 100 m (300 feet) have tripled in mercury concentration since the Industrial Revolution…..” “Tripled” is what the press picked up, but most sources did not print the rest of the sentence: …” and that the ocean as a whole has shown an increase of roughly 10 percent over pre-industrial mercury levels.”

But “tripled.” Wow. How much is that? According to the researchers, the tripling amounts to a concentration of 0.6 parts per trillion in the upper ocean (that means it changed from 0.0000000000002 to 0.0000000000006, less than one molecule of mercury per liter of water). Are instruments so refined that they can even measure such a small amount? And, how do they know how much mercury was in the oceans in pre -industrial times?

As it turns out, the researchers could not actually measure mercury present in pre-industrial times. Rather, “The group started by looking at data sets that offer detail about oceanic levels of phosphate, a substance that is both better studied than mercury and that behaves in much the same way in the ocean… By determining the ratio of phosphate to mercury …the group was able to estimate mercury in the ocean that originated from natural sources such as the breakdown, or weathering, of rocks on land.” In other words they made a very big assumption.

The researchers also said that current mercury concentration is lower than that reported in several previous papers.

Let’s look at the bigger picture. The following is from a fact sheet published by the Science and Public Policy Institute:

Mercury (Hg) is an element that has existed (and will continue to exist) naturally since the earth was formed 4.5 billion years ago. The oceans alone contain millions of tons of mercury. [So called “pollution mercury” even at 80,000 tons is small compared to the naturally-occurring millions of tons.]

There are two major forms of mercury emitted during fossil fuel combustion:

1. Oxidized, which is water soluble and can be washed out of the air into rivers, lakes, and streams.

2. Elemental, which is not water soluble and moves around in a global mercury cycle.

A small fraction (about one one-thousandth) of the oxidized mercury that ends up in waterways may be changed into an organic form called methylmercury (MeHg) which is the kind of mercury with which EPA is concerned. This type of mercury can be eaten by tiny organisms that are then eaten by small fish, resulting in possible bioaccumulation in larger fish eaten by humans.

Methylmercury is not emitted directly from fossil-fuel-fired power plants. It is produced and

accumulated within the biosphere by a myriad of mercury transformation processes that do not depend upon the amount of inorganic mercury emitted from man-made sources. The natural cyclical production and destruction is controlled by environmental factors and ecosystem processes that are largely beyond human control or intervention.

A new estimate by scientists from the National Center for Atmospheric Research shows that mercury emissions from forest fires in the lower 48 U.S. states and Alaska amount to about 44 tons per year. This is of similar magnitude to the total mercury emissions from U.S. power plants. When estimates of all natural sources are considered, including geothermal events under oceans and lakes, US power plants may account for as little as 0.002% of the entire annual world mercury emissions budget.

Another SPPI report examines the safety of eating fish and concludes:

“The preponderance of the latest scientific literature strongly suggests that at historic

consumption levels we have always been, and will continue to be, safe from the fish we eat.

All sectors of the U.S. population, especially pregnant women, children and the elderly, should

continue deriving critically needed nutrition from fish. There is no sound scientific evidence to suggest that the American public, especially infants and young children, have been exposed to harmful levels of mercury.”

It’s just another phantom menace so scare the people so they demand that government save us.