Detection and Localization of Hidden Radioactive Sources with Spatial Statistical Method

Annals of Operations Research, Online 10 November 2010

Hong Wan, Tonglin Zhang and Yu Zhu

“The detection of radioactive materials has become a critical issue for environmental services, public health, and national security. This paper proposes a spatial statistical method to detect and localize a hidden radioactive source. Based on a detection system of multiple radiation detectors, the statistical model assumes that the counts of radiation particles received by those detectors are spatially distributed of Poisson distribution, and each comprises a signal and a background. By considering the physical law of signal degradation with distance, the paper provides a numerical method to compute the maximum likelihood estimates of the strength and location of the source. Based on these estimates, a likelihood ratio statistic is used to test the existence of the source. Because of the special properties of the model, the test statistic does not converge asymptotically to the standard chi-square distribution. Thus a bootstrap method is proposed to compute the p-value in the test. The simulation results show that the proposed method is efficient for detecting and localizing the hidden radioactive source.”

Soil Samples Reveal Urban Mercury Footprints

Indianapolis, St. Louis, Detroit, Buffalo, Richmond and Providence – cities scattered across the eastern half of the United States – have something in common, all have coal-fired power plants. A new study from the School of Science at Indiana University-Purdue University Indianapolis (IUPUI ) is among the first to investigate mercury deposits in industrialized city soil near this type of facility.

The study, which appears in the July 2011 issue of the journal Water, Air & Soil Pollution, reports that measurable amounts of the mercury emitted by coal-fired power plants is deposited in local soil and subsequently enters regional watersheds, contaminating fish and making them unsafe for human consumption.

Soil Samples Reveal Urban Mercury Footprints

The wind patterns in this area of Indiana blow dominantly to the northeast (see wind rose on lower left). The high soil mercury values are seen downwind of the largest mercury emitter in central Indiana. This pattern suggests that local sources of mercury also impact local deposition of mercury in central Indiana, which in turn causes high levels of mercury in waterways and in fish.

Previous research on the spread of environmental mercury has focused on waterways. The IUPUI researchers looked at land, testing soil samples, detecting hot spots of mercury contamination in central Indiana specifically tied to local coal-fired power plants by chemical signatures. Winds blew the mercury contaminated soil to the northeast and the natural flow of waterways brought the mercury back to the southwest, far into bucolic appearing areas frequented by anglers.

While wind patterns vary by cities, the process in various urban areas is similar with mercury emitted from coal-fired power plants contaminating soil that is then transported downstream. Since cities have a high percentage of impervious surfaces like roads and parking lots, the mercury enters waterways rapidly.

“Mercury from coal-fired power plants has been found in the ice at the North and the South Poles, so the fact that these noxious emissions are swept far away to other areas or even continents, with global environmental impact, is well known.  What had not been previously shown is the impact of the mercury on the environments in cities, suburbs and rural areas near specific coal-burning power plants,” said senior author Gabriel M. Filippelli, Ph.D., professor of earth sciences at the School of Science at IUPUI.

Coal-fired power plants produce electricity at a relatively low cost. This is false economy, according to Filippelli, who directs the Center for Urban Health at IUPUI, because these cost figures do not factor in the impact of these plants on human health. He is a pioneer in the emerging field of medical geology and served as the first elected chair of the Geological Society of America’s Geology and Health Division.

Mercury poisoning can cause permanent neurological damage in humans. Pregnant women and their fetuses are especially susceptible to mercury, much of which enters the body through consumption of contaminated fish.

“We are fouling our local as well as global environment and little has been done to stop it. It all comes down to the choices we make to produce energy. As we gain a better understanding of the deposition and risk patterns of mercury from using dirty coal as our primary energy source in the Midwest, we hopefully will be better able to stop or decrease the emission of this neurotoxin and halt the damage it is causing humans,” said Filippelli.

Carrie Lynn Hatcher, a former graduate student in the School of Science at IUPUI, now at the University of Toronto, is the co-author of “Mercury Cycling in an Urbanized Watershed: The Influence of Wind Distribution and Regional Subwatershed Geometry in Central Indiana, USA.”

The study was supported by the School of Science at IUPUI and the IUPUI Center for Urban Health.

In a November 2010 publication, the U.S. Geological Survey (USGS) reported that mercury concentrations in Indiana watersheds “routinely exceeded criteria protective of humans and commonly exceeded criteria protective of wildlife.” One in seven fish in Indiana contain mercury in levels not fit for human consumption.

[Source: IUPUI press release]

Geo-Literacy Coalition Responds to 2010 National Assessment of Geography Education with Call to Action

The Geo-Literacy Coalition, a newly formed alliance of major corporations and non-profits, has responded to the release of the 2010 results of “The Nation’s Report Card” with a call for the U.S. to invest in geography education.

The Geo-Literacy Coalition has been formed to advocate for improvement in geography, geoscience, and geotechnology education in the United States. The Coalition’s Founding Council consists of the National Geographic Society, CH2M HILL, Esri, and the US Geospatial Intelligence Foundation. They have joined together over their mutual concern about the unpreparedness of Americans to make decisions that require geographic knowledge and skills.

In its statement, the Geo-Literacy Coalition argues that low scores on the national geography assessment are the result of decades-long inattention to geography education. It says that geography education should be treated as a strategic priority on a par with engineering and other sciences.

The Coalition’s Founding Council includes two corporations and two non-profits operating in very different sectors. The Coalition’s joint statement reflects the recognition of the importance of geographic education by each member’s leadership for both its sector and the national interest.

For example, CH2M HILL is a global leader in consulting, design, construction, and operations that works on water, transportation, environmental, and energy projects throughout the world. “As a global company working in more than 70 countries, we recognize the importance of geographic literacy in both doing business and in recruiting a future workforce,” says Lee McIntire, chairman and CEO of CH2M HILL. “One of the challenges faced by our clients is developing sustainable solutions that address the impact of worldwide economic growth on natural resources. The more we understand geographic implications, and help future engineers understand them, the more successful we will be at creating these sustainable solutions.”

Esri is the global leader in geographic information systems technology. Every day more than a million people in 350,000 organizations use Esri software to make decisions based on geographic information. According to Jack Dangermond, founder and president of Esri, “Everyone faces tasks large and small every day that require the application of geographic thinking. From navigating in a crowd to forming an opinion about local land-use patterns to thinking about global climate change, we make geographic decisions. Doing this intelligently requires an understanding of our world.”

The United States Geospatial Intelligence Foundation (USGIF) is an educational foundation dedicated to education, training, and community-building for professionals in the geospatial intelligence field. USGIF has more than 175 corporate, government, and academic member organizations representing thousands of professionals who develop and apply geospatial technologies to address national security challenges. Referring to the NAEP results, Keith Masback, USGIF’s president, said: “Precision location data has never been so available, and the power of place has never been so important — for individuals, businesses, and for our nation’s security. The low scores indicated in the report should serve as a catalyst for increasing investment in educational programs in the geosciences in order to get our young people competent at thinking and working spatially. We simply can’t afford as a nation to get left behind in this critical area.”

[Source: Geo-Literacy Coalition press release]