News

Cole J.C. Van De Ven, Keelin Scully, Mikaela Frame, Natasha J. Sihota, and K. Ulrich Mayer

As a result of the prevalence of fuels in our everyday lives, these fuels can be spilled or accidently released into the subsurface causing environmental and human health concerns. Fortunately, as a result of natural biodegradation in subsurface systems, these contaminants can be consumed and converted to less harmful by-products, carbon dioxide (CO2) and methane (CH4). Utilizing this biodegradation is a viable remedial approach called natural source zone depletion (NSZD). To determine the effectiveness of NSZD, a non-invasive method of measuring the surface efflux of CO2 and CH4 has been developed. However, this study looked to better quantify this biodegradation in dynamic subsurface systems resulting from water table fluctuations, which are expected in natural systems. Using a unique experimental sand tank, measuring 4 m long, 1 m wide and 1.5 m tall, a fuel spill was simulated then we induced water table fluctuations and measured the resulting changes in effluxes and biodegradation. Results show that lowering the water table led to both short-term, large increases in effluxes and long-term increases in biodegradation. This research advances our knowledge of dynamic subsurface effects on NSZD and allows us to better monitor and assess the remediation of contaminated groundwater systems.

On decline, mobile fuel moves downward with the water table, allowing for the rapid release of anaerobically produced gas from below the water table and enhanced aerobic degradation of the more exposed, trapped fuel above the water table.

Karen S. Harpp and Dominique Weis

At the Pacific Centre for Isotopic and Geochemical Research, we performed new, high-precision analyses on isotopes of Pb-Sr-Nd-Hf for 83 samples from the Galápagos islands and compared them to data of similar quality from Hawaiian volcanoes. Both island chains are formed by mantle plumes that are rooted in the deep mantle and that play significant roles in mantle dynamics. This work is exciting because it shows comparable mantle plume structures and geochemical sources for both volcanic island chains: 1) both plumes are compositionally split into two halves and the volcanoes that form above either half have unique isotopic compositions, 2) both plumes straddle the boundary between the Pacific large low shear velocity province (LLSVP) and the ambient Pacific lower mantle, 3) the isotopic compositions of their volcanoes converge at a common composition representative of the average lower Pacific mantle (‘PREMA’), and 4) both plumes incorporate material from the Pacific LLSVP but erupt very different isotopic compositions from these plume domains (‘EMI’ and ‘HIMU’), which suggests that the Pacific LLSVP is more heterogeneous than previously thought. Studies like this that assess the composition Earth’s mantle are important to help us understand how the entire Earth system works.

Schematic diagram showing a side-view and plan-view of the Hawaiian and Galápagos plumes. Each plume consists of two main isotopic halves coloured orange and purple for those originating from the Pacific LLSVP and blue for those originating from the ambient lower Pacific mantle. Direction of plate motion is indicated in both cases and influences how the isotopic domains in the plumes are expressed in the overlying volcanoes – e.g., as a double geochemical chain for Hawaiian volcanoes and as stacked geochemical layers for Galápagos volcanoes.

Joel Saylor and Kurt Sundell

Creating a green economy requires increasing amounts of metals to support electrical generation, transport, and storage. However, new sources of metal and other economically valuable resources are increasingly difficult to find. Information about the location of economic resources is stored in sediments and sedimentary rocks that are eroded from the rocks that originally contained those resources. New research by Joel Saylor and Kurt Sundell develops a method of extracting information about the eroded rocks from the sediments themselves, even if the original rocks are unknown or unavailable for analysis. The new method, called non-negative matrix factorization, can identify specific chemical or isotopic features of the original rocks, as well as identifying the relative amounts of different source rocks that might have been mixed into a specific sediment sample. This new tool can guide exploration by identifying regions that have a high proportion of the economically relevant rocks and so help geoscientists zero in on potential areas for future mines.

Saylor and Sundell's research provides a tool that links sources of sediment (colored mountains and associated curves) containing economically valuable resources to the sediments eroded from them (red dots and associated black curves).

Amy G. Ryan, James K. Russell, Michael J. Heap, Mark E. Zimmerman, and Fabian B. Wadsworth

Whether volcanoes will erupt explosively depends on the behavior of gases trapped in the subsurface. If gas pressures are high within a volcano, the surrounding magma and rocks can break, causing explosive eruptions. Alternatively, if gases vent to the surface through interconnected void spaces, explosive behavior does not occur. Void spaces in volcanoes are ephemeral – numerous processes can close them. Here we show that solid state sintering – a historically neglected process – operates pervasively and efficiently within volcanic conduits. We use high-temperature-pressure experiments and models to characterize and understand the timescales of this process under typical volcanic conditions. Our resarch shows the timescales (days to weeks) to be commensurate with the periodicity of explosive eruptions during lava dome producing eruptions.

Elise M. Olson, Susan E. Allen, Vy Do, Michael Dunphy, and Debby Ianson

The University of British Columbia sits on a promontory overlooking the Salish Sea. As you look out over the water, you see its quickly changing variations in color and roughness. That is just the surface! We have run a model (SalishSeaCast: salishsea.eos.ubc.ca) every day since 2014 to capture the motion of the water, the mixing, and the changes in temperature and salinity. Now we have added a biological component so we can see changes in the phytoplankton growth as the phytoplankton blooms in the spring, then dies back due to nutrient limitation and grazing by zooplankton. Events, like wind storms, that resupply nutrients to the sunlit surface waters, can trigger new phytoplankton growth during summer months. In the manuscript, we present the model and its evaluation showing how accurately it represents this seasonal cycle and variability in time and space. We show that strong tidal flow through the narrow Discovery Passage, near Campbell River, leads to turbulent mixing, bringing deep nutrients to the surface. Tidal currents carry these nutrient-rich surface waters into the northern Strait of Georgia, relieving nutrient limitation and allowing phytoplankton to grow, contributing to the region's fish and shellfish productivity.

Strong tidal flow through the narrow Discovery Passage, near Campbell River, leads to turbulent mixing, bringing deep nutrients to the surface. Tidal currents carry these nutrient-rich surface waters into the northern Strait of Georgia, relieving nutrient limitation and allowing phytoplankton to grow, contributing to the region's fish and shellfish productivity.

Manar is a research scientist in the Department of Earth, Ocean & Atmospheric Sciences at the University of British Columbia. She is interested in understanding the evolution of different parts of the solar system and its constituents. Her research career started with studying the interactions between Mercury’s magnetic field and the solar wind, and continued through her involvement as a scientific collaborator and Deputy Instrument Scientist on the OSIRIS-REx mission, the first NASA mission to attempt to bring a pristine sample back to Earth from an asteroid. Manar will begin her Ph.D. at the University of Berkley in January 2020 where she will expand her knowledge of planetary evolution through the study of the motion of material throughout Earth. Her main focus will be the interactions between the core and mantle throughout Earth’s history.

Pacific Museum of Earth · Quarantine Conversation with Manar Al Asad - Planetary Scientist