G³⁶⁰ Research featured in Canadian Journal of Earth Sciences Special Issue

The special issue entitled Quaternary Geology of Southern Ontario and Applications to Hydrogeology brings together 11 papers.

Co-edited by G360 Principal Investigater Dr. Emmanuelle Arnaud and Geological Survey of Canada colleague Dr. Hazen Russell, with the Ontario Geological Survey as collaborators, the issue focuses on buried valleys, moraines, and late glacial lake basins to provide insights on aquifer/aquitard distribution, connectivity, heterogeneity and modeling approaches.

The paper version of the special issue was distributed Fall 2018. The full publication is open access online.

The article summarizing this research was published in the 2018 G360 Newsletter here.

New Paper Available: On methods for in-well nitrate monitoring using optical sensors.

We are pleased to announce the publication of a new article in Groundwater Monitoring and Remediation from the G360 Institute Team.

On methods for in-well nitrate monitoring using optical sensors.
MacDonald*, G., Levison, J., Parker, B.L.
DOI: 10.1111/gwmr.12248

Acknowledgments
The authors would like to acknowledge the Canadian Foundation for Innovation (CFI), Ontario Research Fund: Small Infrastructure, Ontario Research Fund Research Excellence Round 3 Award ORF-RE 03-061 (ORF RE-3), The Canadian Natural Sciences and Engineering Research Council (NSERC) and the University of Guelph School of Engineering for financial support of this research. Norfolk County, the Region of Waterloo and City of Guelph are acknowledged for providing access to wells/field sites. Bill Banks of Banks Groundwater Engineering Ltd. provided valuable technical input throughout the research and is gratefully acknowledged.

Funding
University of Guelph School of Engineering
Canadian Natural Sciences and Engineering Research Council
Small Infrastructure, Ontario Research Fund Research Excellence Round 3. Grant Number: ORF-RE 03-061
Canadian Foundation for Innovation (CFI)

Abstract:
Optical sensors are promising for collecting high resolution in-well groundwater nitrate monitoring data. Traditional well purging methods are labor intensive, can disturb ambient conditions and yield an unknown blend of groundwater in the samples collected, and obtain samples at a limited temporal resolution (i.e., monthly or seasonally). This study evaluated the Submersible Ultraviolet Nitrate Analyzer (SUNA) for in-well nitrate monitoring through new applications in shallow overburden and fractured bedrock environments. Results indicated that SUNA nitrate-N concentration measurements during flow cell testing were strongly correlated (R 2 = 0.99) to purged sample concentrations. Vertical profiling of the water column identified distinct zones having different nitrate-N concentrations in conventional long-screened overburden wells and open bedrock boreholes. Real-time remote monitoring revealed dynamic responses in nitrate-N concentrations following recharge events. The monitoring platform significantly reduced labor requirements for the large amount of data produced. Practitioners should consider using optical sensors for real-time monitoring if nitrate concentrations are expected to change rapidly, or if a site’s physical constraints make traditional sampling programs challenging. This study demonstrates the feasibility of applying the SUNA in shallow overburden and fractured bedrock environments to obtain reliable data, identifies operational challenges encountered, and discusses the range of insights available to groundwater professionals so they will seek to gather high resolution in-well monitoring data wherever possible.

New Paper Available: High resolution spatial and temporal evolution of dissolved gases in groundwater during a controlled natural gas release experiment.

We are pleased to announce the publication of a new article in Science of the Total Environment, 622-623: 1178-1192, from the G360 Institute Team.

High resolution spatial and temporal evolution of dissolved gases in groundwater during a controlled natural gas release experiment.
Cahill*, A.G., Parker, B.L., Mayer, B., Mayer, K.U., Cherry, J.A.
DOI: 10.1016/j.scitotenv.2017.12.049

Acknowledgments
Funding for this study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC) under grant STPGP 463045 – 14 awarded to Professors John Cherry and Beth Parker. Special thanks for field and laboratory assistance are given to Michael Nightingale, Andreas Haggman, Bethany Ladd, Dylan Klazinga, Terri Cheung, Leon Halwa and Alyssa Verdin.

Abstract:
Fugitive gas comprised primarily of methane (CH4) with traces of ethane and propane (collectively termed C1–3) may negatively impact shallow groundwater when unintentionally released from oil and natural gas wells. Currently, knowledge of fugitive gas migration, subsurface source identification and oxidation potential in groundwater is limited. To advance understanding, a controlled release experiment was performed at the Borden Research Aquifer, Canada, whereby 51 m3 of natural gas was injected into an unconfined sand aquifer over 72 days with dissolved gases monitored over 323 days. During active gas injection, a dispersed plume of dissolved C1–3 evolved in a depth discrete and spatially complex manner. Evolution of the dissolved gas plume was driven by free-phase gas migration controlled by small-scale sediment layering and anisotropy. Upon cessation of gas injection, C1–3 concentrations increased to the greatest levels observed, particularly at 2 and 6 m depths, reaching up to 31.5, 1.5 and 0.1 mg/L respectively before stabilizing and persisting. At no time did groundwater become fully saturated with natural gas at the scale of sampling undertaken. Throughout the experiment the isotopic composition of injected methane (δ13C of − 42.2‰) and the wetness parameter (i.e. the ratio of C1 to C2 +) constituted excellent tracers for the presence of fugitive gas at concentrations > 2 mg/L. At discrete times C1–3 concentrations varied by up to 4 orders of magnitude over 8 m of aquifer thickness (e.g. from < 0.01 to 30 mg/L for CH4), while some groundwater samples lacked evidence of fugitive gas, despite being within 10 m of the injection zone. Meanwhile, carbon isotope ratios of dissolved CH4 showed no evidence of oxidation. Our results show that while impacts to aquifers from a fugitive gas event are readily detectable at discrete depths, they are spatially and temporally variable and dissolved methane has propensity to persist.