Recent EES Division Highlights

Other Archived Highlights

August 26, 2009

Student Symposium Awards - Earth and Space Science

Benjamin Linhoff, EES-14, collected groundwater samples from domestic wells throughout the Santa Fe region for analysis at LANL. He used GIS, geochemical modeling, and data analyses to investigate the source and distribution of uranium. The results suggest that cation exchange is an important process mobilizing uranium (VI) within aquifer systems and that groundwater isotope signatures of uranium are consistent with natural sources. Approximately 50% of the wells have uranium concentrations exceeding EPA's drinking water standard. EES-14's Patrick Longmire is Benjamin's mentor.

Irena Ossola, EES-16 investigated model simulations to explain the release of carbon dioxide (CO₂) and methane (CH₄) from permafrost into the atmosphere. Microbes generate CO₂ and/or CH₄ through the breakdown of stored carbon compounds within the shrinking permafrost, making CO₂ and CH₄ available for release into the atmosphere. Models and research of the permafrost's active layer cycle and microbe development provide a better understanding of the future implications of climate change as a result of permafrost melting. Bryan Travis of EES-16 mentors Irena.

August 5, 2009

Tracer Experiments and Modeling simulations through Unsaturated Tuff

Yucca Mountain was studied extensively to determine whether it is a suitable site for a high-level nuclear waste repository. Much research has been conducted on the hydrologic and geochemical properties of the vadose and saturated zones surrounding Yucca Mountain. Experiments have been performed at the proposed waste storage horizon in the Exploratory Science Facility, but rocks below this level are difficult to access within Yucca Mountain. Therefore, the Busted Butte Unsaturated Zone Transport Test (UZTT) was designed to access exposures of the Topopah Spring Tuff and the Calico Hills Tuff, units stratigraphically correlative and mineralogically similar to the unsaturated rocks underlying the proposed repository.

Busted Butte is located at the Nevada Test Site, 8 km southeast of Yucca Mountain. The UZTT was initiated to explore the in situ behavior of solute and colloid movement through the tuff horizons that underlie the proposed repository. Specific issues of concern include the interaction of solute and colloid transport with heterogeneity and fractures, applicability of measured laboratory parameters to the field scale and site scale, and evaluation of numerical models for unsaturated transport in fractured tuff.

EES researchers Philip Stauffer, Jasper Vrugt, H. Jake Turin, Carl Gable, and Wendy Soll conducted a series of experimental and modeling tests using data from the Busted Butte Unsaturated Zone Transport Test.

Left - Magnitude of the vertical volumetric flux at the time of initial tracer breakthrough. Advection is dominant in the upper 10 cm while diffusion becomes dominant in the lower section of the tracer flow path.
Right - Cover image for the Vadose Zone Journal showing the L-shaped alcove used to conduct the Busted Butte Unsaturated Zone Transport Test. Gilles Bussod (formerly of EES) led this interdisciplinary project.

The scientists conducted a suite of reactive (e.g., lithium), nonreactive (bromide), and colloidal tracer experiments in a side alcove at the Test Facility. The researchers used the FEHM numerical simulator (finite element heat and mass transfer porous flow) populated with laboratory-measured hydrologic properties to verify that the conceptual model of the tracer test yielded a good fit to the tracer breakthrough data. They also employed search algorithms to find optimal parameter estimates in the conceptual model and to estimate their uncertainty. The FEHM model was run more than 50,000 times using parallel computing on a distributed computer cluster. The experimental and modeling results show that no observed breakthrough of colloids, low breakthroughs of lithium, and measured significant and rapid breakthrough of bromide.

The test captured both advective (transport of a substance in a fluid) and diffusive tracer transport. Measured hydraulic parameters from rock core samples provide a relatively accurate description of flow and transport at the scale and flow rates of the Busted Butte test. The data imply that one should be particularly careful in assigning values of the unsaturated subsurface flow and transport parameters without recourse to examining both parameter and model formulation uncertainty.

This paper is highlighted in the journal cover artwork and is further discussed in a News Article entitled "Unsaturated Zone Interest Group Overcomes Barriers to Advance Interdisciplinary Science" in the May 2009 edition of CSA News, the official magazine for members of the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

"Untangling Diffusion from Advection in Unsaturated Porous Media: Experimental Data, Modeling, and Parameter Uncertainty," Vadose Zone Journal 8, (2009), doi: 10.2136/vzj2008.0055.

The DOE Civilian Radioactive Waste Management Program, Yucca Mountain Site Characterization Program Office supported the experimental design, data collection, and initial modeling. A LANL J. Robert Oppenheimer Fellowship supported J.A. Vrugt.

August 4, 2009

Boundary Layer Micro-Streaming

Behavior of colloidal particles subject to ultrasonic stimulations in bulk solution or at interfaces is critical to many applications. The behavior of these particles can be detrimental or beneficial, depending on the application. Acoustically induced clustering of tracer particles and/or their adhesion to the walls of test channels, tubes, vessels, or organs is problematic for medical, flow cytometry, and microfluidics applications.

However, some induced phenomena can be adapted to provide unique advantages to applications such as segregation and manipulation of particles, lab-on-a-chip, enhancing mixing in microfluidic and surface acoustic wave (SAW) devices, enhanced oil recovery, wastewater treatment, and groundwater remediation applications. Understanding the underlying phenomena provides improved insight into the interplay between two fundamental science areas - acoustics and electrokinetics.

To achieve this objective Amr Abdel-Fattah and Sowmitri Tarimala of EES-14 and Peter Roberts of EES-17 conducted microscopic visualization experiments using the Automated Video Microscopic Imaging and Data Acquisition System, an advanced video microscopic visualization tool unique to LANL (U.S. Patent # 6,836,559).

Left - Behaviors induced by acoustic wave (f = 313 kHz; Vpp = 0.6 V) interaction with a suspension of 2.26-micron polystyrene particles in de-ionized water: wavelength-scale Rayleigh streaming; transport by direct radiation forces; and boundary-layer microstreaming.
Right - Resulting high speed orbiting can be engineered to build micro-stirrers for microfluidics applications.

The scientists uncovered and characterized intriguing phenomena representing the first experimental manifestation of boundary-layer acoustic micro-streaming. A colloidal suspension of 2.2-micron diameter fluorescent polystyrene microspheres was injected into a parallel-plate glass flow cell and subjected to high-frequency acoustics (200-500 kHz) through a piezoelectric transducer attached to one of the cell's outer walls. When suspended in de-ionized water, the acoustic stimulation of the colloid suspension at 313 kHz induced three distinct particle behaviors...

1. entrainment and bulk transport via wavelength-scale Rayleigh streaming,
2. transport via direct radiation forces to concentrate at nodal planes, and
3. suspended particles orbiting particles deposited on the glass surface as seen in the image above.

Left- A true image of "chain-like" particle clusters in an ionic suspension.
Right - The illustration depicts that the growth of the cluster is opposite to the direction of streaming.

The scientists attribute this latter phenomenon to the interplay between the boundary layer vortex micro-streaming and bulk Rayleigh streaming. Particle orbiting occurs at specific frequencies and locations. The shape of the orbits is determined by the applied frequency, whereas the rotation speed (~50-1100 rpm) is proportional to the applied amplitude (100-600 mV). Changing the orbiting behavior is highly controllable and instantaneous, making such a phenomenon suitable for remotely enhanced mixing in microfluidics. This could be the basis for a new electrokinetics-based power generation technology.

The scientists observed additional behavior at higher ionic strength. Chain-like clustering at the cell's surface started with a deposited particle as the "seed" for this chain and grows in the direction opposite to that of Rayleigh streaming as seen in the image above. These observations indicate that boundary layer effects are strongly coupled with electrokinetic effects. The varied particle behavior observed in the experiments represents important processes such as colloidal release in sub-surface environment and contaminant transport in ground water aquifers whereby acoustic energy is capable of affecting colloid mobility and distribution in systems of various scales.

The DOE Office of Science, Basic Energy Sciences Program supported the work.

July 15, 2009

Understanding Arctic Temperature Change Amplification

Understanding the past variability in Arctic temperatures is essential to assess the future melting of the Greenland ice sheet, Arctic sea ice, and Arctic permafrost. Models predict that the Arctic warms 2 to 3 times faster than the global mean.

Arctic - ~37 surface temperature monitoring stations from which data are used to reconstruct the Arctic temperature record from 1880.

In a paper published in July 2009, Petr Chylek (ISR-2), Manvendra Dubey (EES-14), and collaborators at UK-Met Office, University of Washington, and Dalhousie University analyzed the century-long observational record of surface temperatures to quantify the warming in the Arctic relative to the global mean. They identified two distinct warming periods, 1910-1940 and 1970-2008, with respective Arctic warming rates that are 5.4 and 2 times larger than rates of global warming. The intervening period of 1940-1970 cooled at a rate about 9 times faster than the global cooling rate.

Annual average temperature anomalies relative to the 1910-2008 average for the Arctic (left) and Earth (right). The heavy solid black line is a 5-year running mean. The solid colored lines are the linear regressed trends for the 3 distinct periods.

The Arctic temperature changes are highly correlated with the Atlantic Multi-decadal Oscillation (AMO), suggesting that the Atlantic thermohaline circulation is linked to the Arctic temperature variability on multi-decade timescales. The scientists conclude that the ocean thermohaline circulation may be a greater factor than carbon dioxide and other greenhouse gases in influencing the Arctic climate. The observations confirm that the Arctic has warmed twice as fast as the world over the last 4 decades as simulated by coupled climate models.

The 11- year running average of Arctic temperature anomaly in K (red lines, detrended is thick red line) and the AMO index anomaly from NOAA (black) and UK Met Office (Blue).

However, most models under-predict the rapid Arctic warming observed in the early part of the 20th century. This result suggests that there are physical processes in the climate system that are not yet fully understood and properly described by the current models. This problem should be resolved by ensuring that coupled-climate models reproduce the observed natural oscillations such as the AMO. This is critical to determine whether natural climate variability will make the Arctic more or less vulnerable to anthropogenic global warming that is projected to intensify in the near future.

"Arctic Air Temperature Change Amplification and the Atlantic Multidecadal Oscillation", Geophysical Research Letters 36, L14801 (2009), doi:10.1029/2009GL038777.

LANL Laboratory Directed Research and Development (LDRD) supported the LANL research.

July 14, 2009

Nuclear Explosion Monitoring: A Test Case in North Korea

One of the most important US global security efforts is the monitoring of nuclear weapons development. The recent underground nuclear test by North Korea highlights one of LANL's important nonproliferation programs in this arena. In response to this test, the Ground Based Nuclear Explosion Team (GNEM, in the Geophysics Group) analyzed seismic and infrasonic data and quickly reported their analysis to DOE. Key elements of the report include yield estimates, high-precision event location, infrasonic analysis, discrimination results, and a spectral comparison between the 2006 and 2009 events. Since the GNEM team performs event detection, location, identification, and characterization research that enhances this critical national security capability, these events provide an opportunity to demonstrate progress of the capability and to test new analysis algorithms.

Click thumbnail to view larger image.

Left - Analysis by Hans Hartse shows separation of chemical and nuclear explosions versus earthquakes based on seismic amplitude ratios in the vicinity of North Korea. The top left plot shows amplitude ratios versus magnitude, and the bottom left plot shows amplitude ratios versus distance.

Right - The Korean Peninsula, with locations of earthquakes (green dots), a chemical explosion (red star) and two nuclear explosions (pink stars). Seismic stations MDJ and KSRS are also shown.

The North Korea information was compiled by Ward Hawkins (GNEM Program Manager) and Dale Anderson (Deputy Program Manager), and, along with Howard Patton, was presented at DOE two days after the occurrence of the test. Key elements of the report include yield estimates by Scott Phillips, high-precision event location by Michael Begnaud, infrasonic analysis by Rod Whitaker, and discrimination results from Hans Hartse. George Randall performed a spectral comparison between the 2006 and 2009 event, and Richard Stead compiled data for the analyses.

The NNSA Office of Nonproliferation Research and Development funds the GNEM team's work.

July 12, 2009

EES Scientists Provide Seismic Hazard Assessments

Emily Schultz-Fellenz and Richard Kelley (EES-16) had a major role in helping LANL submit its revised draft hazardous waste permit to the New Mexico Environment Department (NMED). Permitted facilities, including those that accept or process hazardous waste at LANL, must show compliance with the seismic location standard of 40 CFR §§ 264.18(a) and 270.14(b)(11)(ii). These regulations prohibit location of a new, enlarged, or re-permitted facility closer than 200 feet to a fault that has had displacement in Holocene time.

Emily Schultz-Fellenz, second from left, leads a geological tour at LANL.

As requested by LANL's RCRA Permitting and Compliance Team (ENV-RCRA), Schultz-Fellenz and Kelley prepared seismic hazard assessment reports for three LANL facilities to demonstrate each facility's compliance with the seismic location standard. The reports summarized published geologic data, synthesized previous aerial reconnaissance of the areas, showed aerial photographic analyses of lineaments based on the most recent aerial imagery of the area, shared maps of the most recent state of knowledge of the Pajarito fault system, and described fieldwork completed to confirm each site's compliance with the seismic location standard. Schultz-Fellenz and Kelley led members of the NMED's Hazardous Waste Bureau on a day-long geologic site visit to the three LANL sites under consideration for permitting. The NMED determined that the work by Schultz-Fellenz and Kelley satisfied the seismic locations standard for the three LANL facilities to be permitted. Both Schultz-Fellenz and Kelley received high praise from the ENV-RCRA Team Leader for the excellent quality of their work and deliverables, the effectiveness of their interface with NMED personnel, and their professionalism.

The hazardous materials waste organizations at TA-55 and TA-54, and ENV Division sponsored the work.

July 8, 2009

High School Students Learn About Nuclear Science from EES-12 Scientists

Carlsbad High School students learned about nuclear science from Jef Lucchini, an actinide chemist with the EES-12 Actinide Chemistry and Repository Science Program (ACRSP), and others affiliated with the Waste Isolation Pilot Plant (WIPP). The Carlsbad High School nuclear symposium is an outreach program, which Lucchini organized for the 4th year in a row in collaboration with science teachers and administration. The students attended lectures and toured the New Mexico State University Carlsbad Environmental Monitoring and Research Center (NMSU/CEMRC), where the ACRSP team works. Lucchini gave an overview about radioactivity and nuclear science, and other scientists from CEMRC, Sandia National Laboratory, and URS Washington TRU Solutions, gave talks about background radiation effects, options for the end of the nuclear fuel cycle, and the importance of education in a professional career. The American Nuclear Society, Carlsbad chapter offered scholarships to the two seniors who received the best scores on a 20-question quiz about the information presented. The high quality and accuracy of the responses indicated that the students understood the major concepts of the educational event.

Jef Lucchini (EES-12) presents the concept of radioactive decay.

July 2, 2009

Energy and Environment are Topics in Café Scientifíque Presentations

Bruce Robinson (EES-DO), Bill Tumas (SPO-AE), Cathy Wilson (EES-14), and Andy Wolfsberg (EES-16) interacted with New Mexico high school students in recent Café Scientifique meetings. The Café aims to get students to ponder local to global challenges and discuss how science can help address these big problems. The Café engages students in Española, Albuquerque, Santa Fe, and Los Alamos. Over the last few months the Café sessions have focused on energy and environment issues.

Bruce Robinson, Cathy Wilson, and Andy Wolfsberg.

Robinson spoke about nuclear energy and the challenge of assessing the risk of waste disposal options. Tumas discussed the future of cars and the science and engineering that are needed to make safe, affordable hydrogen powered vehicles. Wilson posed the question: "Where will our water come from as we face population growth and climate change?" Wolfsberg asked students to consider the social and engineering challenges of reducing our massive greenhouse gas emissions.

For more information, see www.cafenm.org.

Ground Water Transport Model of the Saturated Zone for Yucca

The DOE has submitted a license application to the Nuclear Regulatory Commission (NRC) to create a geologic repository at the Yucca Mountain, located about 150 km northwest of Las Vegas, NV, for the disposal of spent nuclear fuel and high-level radioactive waste. LANL scientists, including S. Kelkar (EES-16), M. Ding (EES-14), S. Chu (EES-16), and B. Robinson (EES-DO), collaborated with scientists from Sandia National Laboratory and consultants to develop a computational model of radionuclide transport in the ground waters beneath the Yucca Mountain. This work assisted the DOE in the license application.

A number of engineered and natural barriers are expected to retard any potential release of radionuclides from the repository and to reduce their concentrations. In the event of a release, the ground water beneath the Yucca Mountain is a primary medium through which most radionuclides might move from the geologic repository to the accessible environment at the compliance boundary. The role of the saturated zone is to delay the transport of radionuclides to the accessible environment and to reduce the concentration of radionuclides before they reach the accessible environment. Thus, the flow and transport through the saturated zone form an important input to the total system performance assessment (TSPA) calculations. Performance assessment results are likely to depend strongly on the radionuclide breakthrough curves which are determined by the specific discharge, flow paths, and flow distribution of ground water and the mechanisms of solute transport. The model is based on the LANL computer code FEHM, a general purpose unsaturated-saturated zone non-isothermal code built around state-of-the-art control volume finite element numerical procedures. The transport model uses particle tracking and incorporates matrix diffusion, dispersion and sorption. Model validation is accomplished by comparing a) predicted hydraulic heads with new water-level data, b) predicted flow paths with those estimated from hydrochemistry and isotope data, c) calibrated parameter values with those derived from well testing, and d) predicted specific discharge with the conclusions of the Expert Elicitation Panel.

Particle tracks resulting from the Site-Scale Saturated Zone Base-Case Transport Model (blue), and those deduced from geochemistry (black).

The flow paths and travel times agree with the regional geochemistry data, providing confidence in the transport model. The carbon-14 ages for water samples from wells within the site scale model domain range from about 11,430 years to 16,390 years, which compare well with the mode's predictions. The results show that the radionuclides in the ground waters beneath Yucca Mountain are expected to follow a southward path, turning somewhat to the west at the southern boundary of the model at the Amargosa valley. Transit times for the breakthrough of 50% of the initial solute mass at the 18 km compliance boundary downstream of the Yucca Mountain are on the order of 710 years for the base case of non-reactive transport for radionuclides such technetium and carbon. These transit times can range up to 20,000 to 30,000 years for mildly sorbing radionuclides such as neptunium, and in excess of a million years for strongly sorbing radionuclides such as americium.

July 1, 2009

Patrick Longmire Teaches Environmental Aqueous Geochemistry Course

Patrick Longmire of EES-14, the Earth Systems and Observations Group, taught an Environmental Aqueous Geochemistry two-day short course in Santa Fe, NM. Staff from the DOE Oversight Bureau, Solid Waste Bureau, Hazardous Waste Bureau, Petroleum Storage Tank Bureau, City of Santa Fe, Good Water Company, HydraTech New Mexico, and LANL attended. The New Mexico Environmental Department (NMED) requested that Longmire teach the class based on his technical credentials and experience in aqueous geochemistry at LANL and elsewhere in New Mexico. This type of interaction between analytical geochemists, modelers, and community scientists is ideal to inform the local community of pressing water quality needs, problems, and solutions. The short course provided detailed information about the scientific process that is used to inform policy makers and disseminate findings to the public. Dave Cobrain of the New Mexico Environmental Department commented that "Pat did an excellent job presenting the material" and that the discussions between modelers and analytical chemists during the course "was useful not only to the NMED people who work on LANL projects but also provided a bit of insight to some of our other staff on issues that they don't usually think about".

The New Mexico Small Business Assistance program supports Longmire's efforts to work with private industry to identify areas within the Espantilde;ola basin where the groundwater contains concentrations of arsenic, uranium, nitrate, and other solutes above drinking water limits. He also works with the Good Water Company to develop water treatment technologies designed to remove arsenic, uranium, silica, and other chemicals from groundwater. Ben Linhoff (EES-14), a post-masters student, provides geochemical and geographic information system expertise. Longmire collaborates with Michael Dale and Kim Granzow of the NMED on various groundwater studies including quantifying naturally occurring perchlorate, applying stable isotopes of nitrogen and sulfur for determining sources nitrate and sulfate, and conducting groundwater dating using tritium/helium and carbon-14 methods.

Patrick Longmire lectures on stable isotopes during the Environmental Aqueous Geochemistry course. NMED staff seated left to right: Daniel Martinez, Kim Granzow, and Michael Dale.

Other Archived Highlights