Unisense MicroProfiling System for High-Resolution Aqueous Geochemical Measurements

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The equipment requested, an automated MicroProfiling System (MPS) from Unisense, will allow for chemical measurements of oxygen, nitrogen species, sulfide, hydrogen, redox and pH at micrometer spatial resolution in water, sediments, soils, and biofilms. The following are research topics that require the MPS: (1) Determining how modern microbial processes impact the trace metal composition of sediments, such as shales. The MPS will measure the in situ biogeochemical zonation in modern coastal sediment, which combined with the analyses of porewater and sediment geochemistry, shows how trace metal patterns are modified during burial. This is, in turn, important for assessing whether the composition of ancient shales can be used to infer paleo-seawater composition. (2) Ascertaining the influence of biochar (pyrolyzed carbon) on global elemental cycling, soil chemistry and redox properties, and contaminant transport. The MPS is needed to measure redox changes and microbial respiration at the grain scale in the upper part of soils where redox conditions change rapidly, and in laboratory column experiments that aim to simulate biochar migration in a controlled environment. (3) Establishing the influence of lowered dissolved oxygen in marine waters on animal size and diversity in seafloor sediments through aquaria studies where sediment-dwelling communities are held under controlled conditions. The MPS allows an observation of animal-population size and diversity responses to lowered oxygen and rising sulfide that can be used to interpret trace fossil data in the rock record. (4) Examining the cycles of life-constituting elements (e.g., carbon, nitrogen, sulfur) and critical metals (e.g., iron) and their impacts on the habitability in deep subsurface groundwaters and hot springs. The MPS allows for in situ measurements of redox conditions at a high spatial resolution, specifically nitrogen species for which there is a dearth of data in such environments. (5) Studying the mechanisms by which microbes form minerals and how they influence mineral phase transitions. The MPS will make it possible to collect profiles of pH, redox conditions, and trace gas concentrations at the sediment-water interface in both the environment and laboratory aquaria. This data will be combined with electron and synchrotron microscopy to provide an unprecedented picture of biomineralization at the micron scale. (6) Characterizing how nutrients in glacial meltwaters of the Canadian Arctic impact marine microbial communities. The MPS will extend these studies by determining the biogeochemical zonation of underlying sediments, thus elucidating how biomass and their assimilated nutrients are processed. This pairing of water and sediment column datasets will show how biomass is preserved in modern sediment, and ultimately to understand the effects of past periods of extensive glaciation in Earth's history (e.g., `Snowball Earth') on the evolution of marine phytoplankton.