Researchers at the University of Nevada, Reno have found that an instrument the scientific community commonly uses to measure mercury in the air yields inaccurate results.

Principal researcher Mae Gustin in the Department of Natural Resources and Environmental Sciences has been leading the effort to determine the accuracy of a widely used mercury measuring instrument. The study is expected to support and inform regulatory decision-making aimed at protecting human and wildlife health.

"It's robust what we're saying scientifically," Gustin said. "We've demonstrated that the instrument is not measuring gaseous oxidized mercury or particulate bound mercury very well. In fact, gaseous oxidized mercury in the air is two to 13 times higher in the air than the instrument is measuring."

When deposited to ecosystems, gaseous oxidized mercury can be converted to methyl mercury. This form is bio-accumulated and biomagnified in food webs and due to the solubility would be more mobile in ecosystems. Although the atmosphere is a relatively minor reservoir of mercury compared to the ocean or soils, it is an important pathway by which atmospheric mercury is distributed globally over short timescales.

The mercury measuring system has been used by many scientific agencies and scientists, and is deployed in monitoring networks such as the Canadian Mercury Network, Atmospheric Mercury Network and Global Mercury Observation System.

Gustin analyzed the accuracy of the Tekran mercury measurement system, which consists of three units numbered as 2537, 1130 and 1135. These units measure gaseous elemental, gaseous oxidized and particulate bound mercury in the air. Gustin's research team has been focusing on the 1130 unit and has demonstrated that measurements are inaccurate and it does not work as thought.

When Gustin first began publishing more definitive findings in 2013 she said she received resistance from the company that makes the instrument as well as people who had been using the device. She said she now is not getting the same kind of pushback from the scientific community as when her findings were first presented.

Recently, the National Atmospheric Deposition Program, along with the National Oceanic Atmospheric Administration, made measurements of their own and determined that Gustin's research was accurate which has led to other researchers considering her work.

She said that her team suspected the measurements were not correct because the data being collected just did not make sense because of global trends of mercury deposits in the air according to historical data.

Historically, mercury inputs into the atmosphere worldwide have increased several-fold in the past 150 years. Gustin says this requires a dramatic shift in thinking regarding the scientific community's understanding of atmospheric mercury.

Since there has been inaccurate data available through the past 15 years, a big part of a biogeochemical cycle was misinterpreted, which is counteractive for lawmakers around the world who are attempting to reduce the sources. In light of the findings, they will now have to rethink how to address recent agreements like The Minamata Convention, Gustin said.

Gustin and her team outlined several recommendations to move forward the science of atmospheric mercury, including:

• a standard, field-deployable calibration system
• a new passive sampler design is need that determines concentrations, and is calibrated
• quantitative correction factors needed for particles collected with the existing Tekran equipment
• Narrowing uncertainty in the emission speciation of coal-fired utilities, and better understanding of the mechanism and prevalence of in-plume gaseous elemental mercury reduction to gaseous oxidized mercury would be useful.

The Minamata Convention is a United Nations treaty designed to protect human health and the environment from the release of harmful mercury compounds. The treaty has been signed by more than 120 nations, including the United States and Russia, and is now in the process of being ratified.

The treaty will become ratified if 50 of the 120 nations that were part of the original agreement support a ratification. Nineteen countries have agreed to ratification so far.

Representatives of China, one of the countries that signed the agreement, invited Gustin to present her research at a mercury conference in Beijing at the Tsinghua University December 8. During her trip she said that the Chinese and people from other Asian countries were very receptive to her work.

Gustin's work on this topic began in 2007 with a research team based in the University's College of Agriculture, Biotechnology and Natural Resources and comprised of post-doctoral research graduate students and multiple undergraduate students over the years. Through the team's research, they found that data yielded by the Tekran 1130 were significantly underestimated.

Gustin and her team were able to conduct the research with the help of multiple grants totaling more than $2 million through various organizations and agencies such as the National Science Foundation, The Electric Power Research Institute and the Environmental Protection Agency.

"Dr. Gustin's research is characterized by the highest scientific standard and a record of productivity and continuous funding while at the University," said Robert Nowak, professor and chair of Natural Resources and Environmental science. "Her work has brought stature to CABNR and the University, helped CABNR attract high quality graduate students, provided unparalleled opportunities for undergraduates to work in an internationally renowned lab, and provided valuable mentorship for CABNR faculty."