News & Media
Study Shows Coastal Wetlands Aid in Carbon Sequestration
Sea-level rise impacts will likely decrease ecosystem carbon stocks
Tidal marshes, seagrass beds, and tidal forests are exceptional at absorbing and storing carbon. They are referred to as total ecosystem carbon stocks, yet little data exists quantifying how much carbon is absorbed and stored by tidal wetlands in the Pacific Northwest (PNW). Knowing this information is valuable, particularly in the context of sea level rise and with the associated need for Earth system modeling to predict changes at the coast.
Researchers found that the average total ecosystem carbon stock in the PNW is higher than in other areas of the U.S. and other parts of the world. Marsh carbon stocks, in particular, are twice the global average. Researchers found progressive increases in total ecosystem carbon stocks along the elevation gradient of coastal wetland types common in the PNW: seagrass, low marshes, high marshes, and tidal forests. Total carbon also increased along the salinity gradient, with more carbon occurring in lower salinity areas.
Additionally, this research showed that common methods used to estimate soil carbon actually underestimate soil carbon stocks in coastal wetlands. Soil carbon storage below the depth of 100 centimeters proved to be an important carbon pool in PNW tidal wetlands.
The results suggest that long-term sea-level rise impacts, such as tidal inundation and increased soil salinity, will likely decrease ecosystem carbon stocks. This is a concern if wetlands can’t migrate with increased sea level due to being bound by topography and human development.
This research arose from the Pacific Northwest Blue Carbon Working Group, of which Amy Borde and Heida Diefenderfer of Pacific Northwest National Laboratory’s Coastal Sciences Division are members. The team studied 28 tidal ecosystems across the PNW coast, from Humboldt Bay, California, to Padilla Bay, Washington. They sampled common coastal wetland types that occur along broad gradients of elevation, salinity, and tidal influences, collecting the data necessary to calculate total carbon stocks in both above ground biomass and the soil profile.
In three years of study, the researchers found that most carbon is in the wetland soils not aboveground, and much of it is deeper than one meter—a typical lower limit of sampling. Total ecosystem carbon stocks progressively increased along the terrestrial-aquatic gradient of coastal wetland ecosystems common in the temperate zone including seagrass, low marshes, high marshes, and tidal forests. The findings were reported in “Total Ecosystem Carbon Stocks at the Marine-Terrestrial Interface: Blue Carbon of the Pacific Northwest Coast, USA,” published in the August 2020 online edition of Global Change Biology (DOI: 10.1111/gcb.15248).
Research Team: PNNL’s Amy Borde and Heida Diefenderfer, along with J. Boone Kauffman, Leila Giovanonni, James Kelly, Nicholas Dunstan, and Christopher Janousek (Oregon State University); Craig Cornu and Laura Brophy (Institute for Applied Ecology/Estuary Technical Group); and Jude Apple (Padilla Bay National Estuarine Research Reserve).
The grant award was administered by the Institute of Applied Ecology, and other partners included Oregon State University and the Padilla Bay National Estuarine Research Reserve. This research was supported by the National Oceanic and Atmospheric Administration, through a cooperative agreement with the University of Michigan.
Kauffman, J Boone, Leila Giovanonni, James Kelly, Nicholas Dunstan, Amy Borde, Heida Diefenderfer, Craig Cornu, Christopher Janousek, Jude Apple, and Laura Brophy. “Total Ecosystem Carbon Stocks at the Marine‐terrestrial Interface: Blue Carbon of the Pacific Northwest Coast, United States.” Global change biology, no. 0 (August 11, 2020). DOI: 10.1111/GCB.15248
NWRTC Notes From the Field (June 2020)
Interviews with public health professionals who are helping to keep us safe
PNNL's Northwest Regional Technology Center interviews Assistant Chief of Resource Management for Seattle Fire Department Willie Barrington about how his team faced the unknown when the COVID-19 pandemic hit Seattle, Washington.
Physical and Ecological Evaluation of a Fish-Friendly Surface Spillway
AbstractSpillway passage is one of the commonly accepted dam passage alternatives for downstream-migrating salmonids and other species. Fish passing in spill near the water surface have improved chances of survival than fish that pass deeper in the water column near spillway structure. In this study, an autonomous sensor device (Sensor Fish) was deployed in 2005 to evaluate fish passage conditions through the Removable Spillway Weir (RSW) at Ice Harbor Dam on the Snake River in south-central Washington State. RSWs enable fish to pass in spill nearer the water surface compared to conventional spillways where spill discharge is controlled using tainter gates. The RSW study was undertaken concurrently with a separate live fish injury and survival study. Conditions at the RSW–Spillway transition and deflector region were found to be potentially detrimental to fish. As a result, the spillway slope and deflector radius were modified, and the efficacy of the modifications was evaluated in 2015. The frequency of severe acceleration events (acceleration =95 G) during passage decreased significantly (from 51% to 35%; p-value = 0.049), and collisions with structures decreased from 47% to 27% (p-value = 0.015). Pressures observed in the Spillway–Deflector region and pressure rates of change decreased as well. Overall, the modifications resulted in improved hydraulic and fish passage conditions, which contributed to increased fish survival.
CitationDuncan J.P., Z. Deng, J.L. Arnold, T. Fu, B.A. Trumbo, T.J. Carlson, and D. Zhou. 2018. "Physical and Ecological Evaluation of a Fish-Friendly Surface Spillway." Ecological Engineering 110. PNNL-SA-126408. doi:10.1016/j.ecoleng.2017.10.012
Wet Waste Hydrothermal Liquefaction and Biocrude Upgrading to Hydrocarbon Fuels: 2019 State of Technology
Each year, the DOE Bioenergy Technologies Office (BETO) assesses progress in their research and development efforts toward sustainable production of renewable fuels (DOE 2016). Technical and cost targets were previously established for the wet waste hydrothermal liquefaction and biocrude upgrading pathway and summarized in a design report (Snowden-Swan et al. 2017). The present report summarizes the research and associated techno-economic analysis (TEA) in support of the 2019 state of technology (SOT) assessment for this pathway. Data from Pacific Northwest National Laboratory’s Conversion hydrothermal liquefaction (HTL) program for wet waste was used to update the pathway techno-economic analysis (TEA) for the fiscal year 2019 State of Technology (2019 SOT). An overview of the current process model, experimental data and plant economics for the SOT is presented.
Snowden-Swan L.J., J.M. Billing, M.R. Thorson, A.J. Schmidt, D.M. Santosa, S.B. Jones, and R.T. Hallen. 2020. Wet Waste Hydrothermal Liquefaction and Biocrude Upgrading to Hydrocarbon Fuels: 2019 State of Technology. PNNL-29882. Richland, WA: Pacific Northwest National Laboratory.
Strange water behavior on aluminum oxide
Not all surfaces are created equally
Researchers adding water to the surface of alumina measured some surprising results. They were preparing the surface of an alumina crystal in ultrahigh vacuum, intending to achieve a hydroxylated surface to approximate another form of aluminum, called gibbsite (α-Al(OH)3). They're interested in gibbsite because it is part of the mix of materials that comprise highly radioactive waste stored in tanks at various former weapons production sites.
The water was supposed to adsorb to the alumina and then immediately dissociate or separate into its components creating hydroxyl or OH components. Surprisingly, the water remained intact, raising important questions regarding the fundamental reactions that govern chemical transformations of aluminum oxides and hydroxides. The new research stems from work at the Interfacial Dynamics in Radioactive Environments and Materials (IDREAM) Energy Frontier Research Center.
The work, led by Pacific Northwest National Laboratory scientists in collaboration with scientists at University of Notre Dame and Georgia Institute of Technology was published in The Journal of Physical Chemistry C in a paper titled, "Molecular Water Adsorption and Reactions on α-Al2O3(0001) and α-Alumina Particles."
Why it matters: Aluminum oxides play an important role in the processing of high-level radioactive waste because they are one of the largest, nonradioactive components of the wastes generated from defense nuclear materials production during the Cold War.
Detailed knowledge of water behavior on aluminum oxide surfaces is key to understanding corrosion and catalytic properties of alumina and other aluminum-based materials in engineering applications.
Summary:Researchers investigated the adsorption and reactions of water on well-characterized alumina under well-controlled experimental conditions: under ultrahigh vacuum (UHV), using temperature programmed desorption (TPD), infrared reflection absorption spectroscopy (IRAS), electron-stimulated desorption (ESD) and other surface science techniques.
They found that water adsorbs on the pristine surface of an alumina crystal α-Al2O3(0001), with no evidence of further reaction. Conversely, when water contacts α-alumina particles under ambient conditions it dissociates and does create hydroxyls on the particles. Dissociation is energetically favorable for both surfaces, but it appears to be hindered on the defect-free surface of alumina, which is counter to some findings in the literature.
Using UHV and IR spectroscopy techniques, which is typically only done on metals, researchers observed the vibration of water when adsorbed on the face of an alumina crystal. Although surface hydroxyls from dissociation of the molecule were expected, no evidence was observed by IRAS used to measure the vibration. But when alumina nanoparticles were exposed to water, a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) instrument indicated the presence of surface hydroxyls.
What's next? More research is needed to understand why the experiments and theory indicate such different reactivities for this important surface of alumina and to discover if there’s a barrier for water to dissociate and, if so, how to get over that barrier.
This work was supported as part of IDREAM (Interfacial Dynamics in Radioactive Environments and Materials), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The authors acknowledge the Notre Dame Radiation Laboratory, which is supported by DOE BES through Grant DE-FC02-04ER15533.
Sponsors: This work was supported as part of IDREAM (Interfacial Dynamics in Radioactive Environments and Materials), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences and led by Pacific Northwest National Laboratory (PNNL)
User Facilities: The experiments on α-Al2O3(0001) were performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research and located at PNNL.
Research Team: Nikolay G. Petrik and Greg A. Kimmel (Pacific Northwest National Laboratory), Thomas M. Orlando and Patricia L. Huestis (Georgia Institute of Technology), Jay A. LaVerne and Alexandr B. Aleksandrov (University of Notre Dame).
Reference: N.G. Petrik, P.L. Huestis, J.A. LaVerne, A.B. Alekandr, T.M. Orlando, G.A. Kimmel. 2018. “Molecular Water Adsorption and Reactions on α-Al2O3(0001) and α-Alumina Particles.” The Journal of Physical Chemistry C2018, 122, 17, 9540-9551 DOI: 10.1021/acs.jpcc.8b01969