20-37. Metal phytoextraction from ultramafic soils, sediments, and mine wastes

CLOSED

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Background: Comprehensive solutions to mitigating climate change include the use of low-carbon technology such as electric vehicles (EVs), photovoltaics, and wind turbines. However, ramping up manufacturing requires raw materials in the form of mineral (element) resources for which demand could begin to outstrip production. For many of the elements needed to accelerate low-carbon technologies, non-traditional mining activities such as mining of lower quality materials, recycling manufactured products, and re-mining old mine wastes will be needed to meet demand as well as to provide a fallback source in case of supply chain disruption[1].          

The EV case illustrates all these points: nickel (Ni) and cobalt (Co)[2] are both vital to current EV battery compositions, yet our Nation’s import reliance is 50% and 76% for the two elements, respectively according to USGS-NMIC’s 2021 reports[3]. Federal and state (of California) mandates for rapid transition of government and private sector vehicle fleets to EVs is projected to raise domestic demand for Ni and Co still further. At the same time, a 10 – 15% increase in yearly worldwide Co demand is projected, driven largely by heavily subsidized European and Chinese markets for EVs[4]^,[5]. Increasing production of these elements, both worldwide (in new locations) as well as domestically (securing our nation’s own most important needs) is an important but overlooked “infrastructure” activity that strengthens our nation’s resilience in the face of climate- or geopolitically-based disruptions to the current network of worldwide supply chains.          

Mineral deposits in ultramafic rocks[6] have become the primary source of the world’s Ni (they have always been the primary sources of asbestos and chromium). Some ultramafic mineral deposits contain Co, copper (Cu), scandium (Sc), and platinum group element (PGE) resources at levels that might be extracted in the future. Soils developed on ultramafic rocks and mine wastes in ultramafic deposits are significantly enriched in Ni, Co, and Cr relative to other soils and mine wastes. In the past, these low-grade enrichments were not considered profitable to mine, but the economic picture is changing, especially for Ni, Co, Sc, and PGEs in ultramafic deposits^3,4. The situation is somewhat different for Cr and Cu in ultramafic soils, sediment, and mine wastes, since these two elements occur at high enough concentrations to present significant hazard to humans (Cr, in hexavalent form) and aquatic life (Cu). Whether traditional or non-traditional sources are the target of resource extraction, reclamation efforts to limit human exposure to hazardous levels of Cr and Cu (and Ni) and to protect ecosystem health will also be essential.

Optimizing phytoextraction of Ni, Co, or Cr from ultramafic soils, sediments, and/or mine wastes could have benefits for both phytomining[7] and phytoremediation[8], since both rely on growth and subsequent harvest of a crop that accumulates metals in above ground biomass (thereby diminishing its concentration in subsurface). Phytomining might be faster to develop than a traditional mine and might have fewer social and economic costs. Similarly, phytoremediation may require less financial outlay and infrastructure development to achieve the goal of lowering offsite transport of elements (in aqueous or solid phase). However, lack of data regarding phytoextraction using native species and relevant materials makes estimates of key economic parameters (for phytomining and phytoremediation) highly uncertain.

Description of the Research Opportunity: The USGS Mineral Resources Program (MRP) in Menlo Park, California seeks a postdoctoral fellow to conduct laboratory (and possibly field) studies to optimize phytoextraction of element resources and/or contaminants from UM soils, sediments, and/or mine wastes. The postdoc will advance scientific knowledge about fundamental biogeochemical processes controlling phytoextraction. Laboratory experiments are anticipated that will evaluate two phytomining scenarios on (currently) sub-economic materials: (1) low productivity soils developed on ultramafics (e.g., serpentine soils) and (2) and ultramafic mine wastes. Wastes from lateritic Ni (Co) mineral deposits are of particular interest due to their domestic occurrence (i.e., CA, OR, Puerto Rico, AK), but waste from other ultramafic deposit types, such as low sulfide Ni (Co)-Cu-PGE (i.e., Duluth Complex), are also of interest.

The applicant will have latitude to think independently and to develop and conduct innovative work within the proposed scope of activities. Potential topics include (but are not limited to: (1) novel methods to reduce off-site transport for hazard mitigation; (2) plant or microbial (particularly fungal) physiological mechanisms of phytoextraction and metal mobilization; (3) improvements in soil health during phytoextraction; (4) geochemical controls on plant metal uptake and mobilization (and how these might affect phytoextraction over multi-year timescales); (5) micro-scale re-distributions of metals and microorganisms in response to phytoextraction; and (6) comparison of hyperaccumulator mechanisms in ultramafic soils as a function of climate or soil age.

We seek a candidate with expertise in plant-microbe or microbe-metal interactions. The candidate should have some experience optimizing plant growth or yields, ideally by manipulating rhizosphere, endosphere, or phyllosphere communities. The candidate will have the opportunity to work in a multi-disciplinary team with a geochemist/mineralogist/spectroscopist (Foster), soil scientist (Creamer), and other USGS colleagues with expertise in geology, GIS, and decision analysis, as well as with industry and other government partners to provide practical insight and experience and novel technologies that might improve phytoextraction potential.

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

References:

Creamer, C. A., Foster, A. L., Lawrence, C., McFarland, J., Schulz, M., & Waldrop, M. P. (2019). Mineralogy dictates the initial mechanism of microbial necromass association. Geochimica et Cosmochimica Acta, 260, 161-176. https://doi.org/10.1016/j.gca.2019.06.028.

Creamer C. A., Leewis M.-C., Governali, F. C., Freeman, J., Kacur, S., Kracmarova, M., Papík, J., Foster, A. L. (2019). Does enhancing plant-microbe symbiosis improve phytostabilization in mine tailings more than compost amendment? 2019 AGU Fall Meeting Abstract (Poster).

Diedrich, T., Fix, P., and Foster, A. (2017). Mineralogical characterization of weathered outcrops as a tool for constraining water chemistry predictions during project planning. 2017 IMWA conference abstract (Lappeenranta, Finland).

Leewis M.-C., Creamer C. A., Wilson, N., Gray, F., and Foster, A. L. (2019). The phytostabilization potential of native plants: a survey of endemic plants and microbes across the historic Harshaw Mining District, S. Arizona. Abstract.

Proposed Duty Station: Menlo Park, California

Areas of PhD: Biology, plant physiology, botany, soil science, mycology, geomicrobiology, geobotany, soil microbiology or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet the qualifications for one of the following: Research Botanist, Research Biologist, Research Ecologist, Research Forester, Research Geneticist, Research Microbiologist, Research Soil Scientist, or Research Wildlife Biologist.

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Human Resources Office Contact: Paj Shua Cha, 650-439-2455, pcha@usgs.gov 

[1] International Atomic Energy Agency (2021);  de Koning et al. (2018)

[2] Copper (Cu), Lithium (Li), and Graphite (a mineral composed solely of carbon) are the other elements needed for current high-energy density battery formulations for EVs.

[3] NMIC 2021 Cobalt MCS ; NMIC 2021 Nickel MCS

[4] InvestingNews (2021) Cobalt Outlook

[5] WSJ (2021)

[6] Ultramafic rocks are low in silica (typically < 45%), high in Mg and Fe, and low in Ca. Important ultramafic mineral deposit types include serpentinite-hosted asbestos (8d), podiform chromite (8a, 8b), Lateritic Ni (Co) (38a), placer Au-PGE (39a), and magmatic Ni (Co)-Cu-PGE deposits (5a, 5b).

[7] Phytomining: Brooks et al., 1998; van der Ent et al. (2015)

[8] Phytoremediation: Garbisu and Alkorta (2001) ; Suman et al (2018)