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EEWR Brown Bag Seminar with Xuehui Gao and Heather Hunter, Graduate Students

Speaker: Xuehui Gao and Heather Hunter, Graduate Students
Series: EEWR Brown Bag Seminars
Location: Engineering Quad E225
Date/Time: Friday, April 21, 2017, 12:00 p.m. - 1:00 p.m.


Xuehui Guo: Ammonia Emissions, Deposition and Variability

Ammonia is the most abundant alkaline gas in the air and a precursor to ammonium aerosols. Ammonia also contributes to the deposition of reactive nitrogen, which has substantial implications on environmental quality. Agricultural activities such as fertilization and livestock waste management dominate anthropogenic ammonia emissions, and there remain significant uncertainties of ammonia dry deposition. Accurate measurements of ammonia are challenging and limit our abilities to understand these processes. Recent advancements of ground-based and remote sensing techniques have provided new possibilities for studying ammonia. We are developing an algorithm for validating satellite ammonia measurements using in-situ profiles, and we will evaluate the variability of ammonia emissions between different spatiotemporal scales. We are also developing mid-infrared laser-based sensors to overcome the sampling challenges. The sensors will be deployed to quantify ammonia fluxes from the biosphere within forest canopies and at a natural grassland and from agricultural activities. These data will be used in conjunction with satellite measurements to enhance our understanding of ammonia emissions, deposition in the natural environment and spatiotemporal variability.
Heather Hunter: Barite Precipitation Kinetics and Trace Metal Uptake
Chemical precipitation is an effective treatment method for the removal of a number of toxic metals and radionuclides (e.g. Ba, Sr, Ra, As, Cd, Cr) from contaminated water.  Removal of hazardous metals and radionuclides from industrial wastewaters via co-precipitation with barite requires an understanding of the precipitation of solid solutions.  Solid solutions are controlled thermodynamically by the solubilities of the pure endmembers (BaSO4, SrSO4, BaHAsO4, etc.).  Variation in the kinetics of precipitation can also affect the quantities of the co-precipitates within the solid solution.  Solution chemistry conditions such as salinity, saturation, and cation/anion ratio have been shown to change the rates of nucleation and growth.  I investigate the effects of solution chemistry on barite particle growth dynamics and trace element uptake through synchrotron-based X-Ray fluoresence mapping, laboratory kinetic measurements, and a corresponding population balance model.