Matrix Diffusion Effects on Nitrate Fate and Transport in Prince Edward Island's Sedimentary Bedrock Aquifer
Tuesday, September 24, 2013: 1:30 p.m.
Amanda Malenica, BSc.
,
School of Environmental Science, University of Guelph, Toronto, ON
Beth L. Parker, Ph.D.
,
School of Engineering, G360, University of Guelph, Guelph, ON, Canada
Steven W. Chapman, M.Sc., P.Eng.
,
School of Engineering, University of Guelph, Guelph, ON, Canada
John A. Cherry, Ph.D.
,
School of Engineering, University of Guelph, Guelph, ON, Canada
The province of Prince Edward Island is unique in Canada because 100% of the population is reliant on groundwater. Island wide studies have shown increasing nitrate levels associated with intensive agriculture, a major concern both from a human health standpoint and surface water impacts (eutrophication, fish kills). A multicomponent research study is being conducted at four sites focused on nitrate behavior in the fractured bedrock aquifer. As part of this study, effects of matrix diffusion are being evaluated including impacts on nitrate persistence with reduced loading as a result of changes in management practices. The Discrete Fractured Network (DFN) approach is being applied to this problem, which recognizes that much contaminant mass in fractured sedimentary aquifers may reside in the pore water of the rock matrix due to diffusion. The matrix (which has high porosity, typically 5-20% in sandstone) has very large storage capacity compared to the fractures (which have very low porosity, typically 10-3 to 10-5). A key study component is collecting detailed profiles of nitrate distribution from subsampling of continuous cores from boreholes ranging in depth from 80 to 200 feet with matrix pore water analyses for various analytes. Other components include borehole geophysical methods, transmissivity profiling, and design and installation of multi-level groundwater monitoring systems for detailed understanding of hydraulic head and groundwater concentrations. Discrete zones of interest will be monitored long term for temporal changes in nitrate and other analytes. This research will aid in the understanding of the role of matrix-stored nitrate and attenuation mechanisms, and ideally in linking groundwater nitrate fluxes to agricultural management. Ulimately this will improve conceptual models and help agricultural researchers better understand controls on the fate of nitrate under different loading scenarios leading to more scientifically defensible decisions on agricultural best management practices and water supply protection.
Amanda Malenica, BSc., School of Environmental Science, University of Guelph, Toronto, ON
Amanda Malenica is a Masters Student in Hydrogeology at the University of Guelph, Guelph, Ontario. She has a BSc. From McMaster University, Hamilton, Ontario, in Earth and Environmental Science. Her undergraduate research focused on nutrients and toxic contaminants from groundwater sources along Lake Simcoe urban shorelines. Her current research focuses on the transport and fate of nitrate in Prince Edward Island’s fractured sedimentary bedrock aquifer.
Beth L. Parker, Ph.D., School of Engineering, G360, University of Guelph, Guelph, ON, Canada
Beth Parker, Ph.D., University of Guelph Professor in the School of Engineering and Director of the G360 Centre for Applied Groundwater Research, has more than 30 years of experience investigating subsurface contamination at numerous sites around the world, using high resolution data sets for site conceptual model development and testing. Her current research activities emphasize developing improved field and laboratory methods for characterizations and monitoring of industrial contaminants in sedimentary rocks, clayey deposits, and sandy aquifers, and focus on the effects of diffusion in low permeability zones, plume attenuation, and hydrogeologic controls on remediation.
Steven W. Chapman, M.Sc., P.Eng., School of Engineering, University of Guelph, Guelph, ON, Canada
Steven Chapman is a Senior Research Engineer/Hydrogeologist in the G360 Centre for Applied Groundwater Research in the School of Engineering at the University of Guelph. He is a Professional Engineer (Civil) with an M.Sc. from the University of Waterloo (Earth Sciences). Chapman has more than 15 years of hydrogeologic experience. His research focuses on contaminant behavior in unconsolidated porous media and sedimentary rock, involving high resolution site characterization at industrial and research sites and numerical modeling, with a focus on the role of diffusion including impacts on remediation performance.
John A. Cherry, Ph.D., School of Engineering, University of Guelph, Guelph, ON, Canada
John Cherry holds geological engineering degrees from the University of Saskatchewan and the University of California Berkley, and earned a Ph.D. in hydrogeology from the University of Illinois. He joined the University of Waterloo in 1971, concentrating on field studies of the migration and fate of contaminants in groundwater, and continues research as a Distinguished Professor Emeritus. He has co-authored the textbook Groundwater and several chapters in the book on dense chlorinated solvents and other DNAPLs in groundwater. He is the Director of the University Consortium for Field-Focused Groundwater Contamination Research and is now based at the University of Guelph.
