{"659238":{"#nid":"659238","#data":{"type":"event","title":"Phd Defense by Zijian Li","body":[{"value":"\u003Cp\u003EZijian Li\u003Cbr \/\u003E\r\n(Advisor: Prof. Christopher Reinhard) will defend a doctoral thesis entitled,\u003Cbr \/\u003E\r\nThallium isotope investigation of paleo ocean redox and carbon dioxide removal via enhanced rock\u0026nbsp;\u003Cbr \/\u003E\r\nweathering\u003Cbr \/\u003E\r\nOn\u003Cbr \/\u003E\r\nFriday, July 15 at 2:00 p.m.\u003Cbr \/\u003E\r\nES\u0026amp;T Classroom L1125\u003Cbr \/\u003E\r\nhttps:\/\/gatech.zoom.us\/j\/2527896823\u003C\/p\u003E\r\n\r\n\u003Cp\u003EAbstract\u003C\/p\u003E\r\n\r\n\u003Cp\u003EThe oxygenation of Earth\u0026rsquo;s surface fundamentally reshaped global biogeochemical cycles, and surface oxygen levels\u0026nbsp;\u003Cbr \/\u003E\r\nhave played a critical role in the origin and diversification of metazoans. Stable thallium (Tl) isotope systematics\u0026nbsp;\u003Cbr \/\u003E\r\nare mechanistically linked to the burial of manganese (Mn) oxides, making the system an effective redox proxy to\u0026nbsp;\u003Cbr \/\u003E\r\ntrack free oxygen (O2) levels in the ocean. The Mesoarchean and mid-Proterozoic are two critical periods of time in\u0026nbsp;\u003Cbr \/\u003E\r\ngeologic history for the evolution of microbial and complex life. In the first half of this thesis, I analyze Tl\u0026nbsp;\u003Cbr \/\u003E\r\nisotopic compositions of mid-Proterozoic black shales and Mesoarchean siliciclastic sediments and perform stochastic\u0026nbsp;\u003Cbr \/\u003E\r\nmodeling of marine Tl isotope mass balance to extract paleo-redox conditions that have been poorly constrained. The\u0026nbsp;\u003Cbr \/\u003E\r\n\u0026chi;205Tl composition of the upper Velkerri Formation is indistinguishable from the crustal value, which\u0026nbsp;\u003Cbr \/\u003E\r\nimplies the global burial of Mn oxides was limited at 1.36 Ga and contemporaneous deep ocean was pervasively\u0026nbsp;\u003Cbr \/\u003E\r\nanoxic. The strong positive \u0026chi;205Tl values of the 2.95 Ga Sinqeni Formation are not likely to\u0026nbsp;\u003Cbr \/\u003E\r\nrepresent global seawater records, but rather preserve a primary signal of localized Mn oxides\u0026nbsp;\u003Cbr \/\u003E\r\nburial in Mesoarchean marine sediments. Given the free O2 is required to stabilize Mn oxides\u0026nbsp;\u003Cbr \/\u003E\r\nagainst reductive dissolution during settling, our results provide strong evidence for the early\u0026nbsp;\u003Cbr \/\u003E\r\nemergence of oxygenic photosynthesis at least 3 billion years ago.\u003Cbr \/\u003E\r\nThere is increasing consensus that immediate and deep reductions in greenhouse gas (GHG) emissions are\u0026nbsp;\u003Cbr \/\u003E\r\nnecessary in the coming decades to limit global warming to 1.5\u0026deg;C target (the Paris Agreement).\u0026nbsp;\u003Cbr \/\u003E\r\nCarbon dioxide removal (CDR) from Earth\u0026rsquo;s atmosphere is likely to play a significant role in\u0026nbsp;\u003Cbr \/\u003E\r\nachieving the climate mitigation goals. The second half of this thesis focuses on enhanced rock\u0026nbsp;\u003Cbr \/\u003E\r\nweathering (ERW), a negative-emission CDR strategy that spreads milled calcium- and magnesium-rich\u0026nbsp;\u003Cbr \/\u003E\r\nsilicates (or alkaline materials) on croplands or in the ocean to artificially speed up the\u0026nbsp;\u003Cbr \/\u003E\r\nweathering process and associated atmospheric CO2 removal. A hierarchy of models is adopted to\u0026nbsp;\u003Cbr \/\u003E\r\nevaluate the CDR potential and environmental impacts of ocean-based ERW using natural and synthetic\u0026nbsp;\u003Cbr \/\u003E\r\nmineral feedstocks. Compared to olivine and basalt, application of alkaline metal oxides (CaO and\u0026nbsp;\u003Cbr \/\u003E\r\nMgO) leads to higher CDR efficiency with reduced environmental impacts, but deployment at scale\u0026nbsp;\u003Cbr \/\u003E\r\nfaces challenges of substrate limitation and process CO2 emissions. I then\u003Cbr \/\u003E\r\nperform an analysis of the energetic and economic demands of rock grinding, the most energydemanding\u003Cbr \/\u003E\r\nand cost-intensive step in the ERW life cycle, and conduct state-level assessment of\u003Cbr \/\u003E\r\ncarbon footprints, costs, and energy requirements associated with grinding for the U.S. The results\u003Cbr \/\u003E\r\nof geospatial analysis highlight the regional differences in deploying grinding and indicate that the\u003Cbr \/\u003E\r\noperation of grinding in the U.S. is generally cost-effective and energy-efficient based on the\u003Cbr \/\u003E\r\nnation\u0026rsquo;s average electricity mix.\u003Cbr \/\u003E\r\nCommittee\u003Cbr \/\u003E\r\n\u0026bull; Prof. Christopher Reinhard \u0026ndash; School of Earth and Atmospheric Sciences (advisor)\u003Cbr \/\u003E\r\n\u0026bull; Prof. Yuanzhi Tang \u0026ndash; School of Earth and Atmospheric Sciences\u003Cbr \/\u003E\r\n\u0026bull; Prof. Ellery Ingall \u0026ndash; School of Earth and Atmospheric Sciences\u003Cbr \/\u003E\r\n\u0026bull; Prof. Jennifer Glass \u0026ndash; School of Earth and Atmospheric Sciences\u003Cbr \/\u003E\r\n\u0026bull; Prof. Jeremy Owens \u0026ndash; Department of Earth, Ocean, and Atmospheric Science, Florida\u003Cbr \/\u003E\r\nState University\u003Cbr \/\u003E\r\n\u0026bull; Prof. Shuang Zhang \u0026ndash; Department of Oceanography, Texas A\u0026amp;M University\u003C\/p\u003E\r\n","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":"","field_summary_sentence":[{"value":"Thallium isotope investigation of paleo ocean redox and carbon dioxide removal via enhanced rock weathering"}],"uid":"27707","created_gmt":"2022-07-06 01:23:51","changed_gmt":"2022-07-06 01:23:51","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2022-07-15T15:00:00-04:00","event_time_end":"2022-07-15T17:00:00-04:00","event_time_end_last":"2022-07-15T17:00:00-04:00","gmt_time_start":"2022-07-15 19:00:00","gmt_time_end":"2022-07-15 21:00:00","gmt_time_end_last":"2022-07-15 21:00:00","rrule":null,"timezone":"America\/New_York"},"extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78761","name":"Faculty\/Staff"},{"id":"78771","name":"Public"},{"id":"78751","name":"Undergraduate students"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}