Pre-nuclear level of 129I in environment (Subsurface, Groundwater and Minerals)
Iodine is an anion and is mobilized from nuclear waste in aqueous environments. Among all of iodine’s isotopes, 129I has the longest half-life. The objective of this research will be the determination of the natural abundance of 129I in four different environments.
High background geological site (Cigar Lake Natural Analog): Determination of 129I in natural analogs is important because it can reduce the uncertainty of long-term predictions about the mobility of 129I in a deep geological repository (DGR) system. The Canadian Nuclear Safety Commission (CNSC) is interested in Cigar Lake to investigate the mobility of 129I in a high background geological site. Cigar Lake is considered a high background site due to the high uranium concentrations (up to 662,000 ppm). 129I is in secular equilibrium with its parent (238U). As such, the measured value will be compared with predicted secular equilibrium values in order to interpret the results of 129I measurement.
Low background geological site (Bruce Site): The Bruce Nuclear Site (Kindardine, ON) is one of the areas that Ontario Power Generation (OPG) is considering for a DGR to store low and intermediate level radioactive waste. This site allows us to explore background levels of 129I in a pristine environment. Compared to Cigar Lake, Bruce site is considered a low background geological site as the uranium concentrations in this area vary from 1 to 5 ppm.
Low background surficial site (Elmvale artesian flows): Elmvale artesian wells are considered as a low background surficial site to find the background level of 129I in the environment. The concentration of tritium in this artesian flow is zero, therefore this site is a good candidate for measuring pre-nuclear levels of 129I. In addition we will also use 129I as a tracer to understand the regional hydrology.
Iodine-Rich Minerals (Iodargyrie and Marshite): Iodine rich minerals like Iodargyrite (AgI) and Marshite (CuI) can be used to measure 129I when the ore formed. We can measure the background level of 129I in these minerals with the least amount of chemical preparation (reducing potential contamination) and are measured directly with AMS.
Isobar separation for anions in accelerator mass spectrometry studies
My work will integrate the Isobar Separator for Anions (ISA), a radiofrequency quadrupole reaction cell system, into a second injection line of the Lalonde AMS system. This innovative isobar separation method will provide a compact, affordable way for AMS laboratories to measure a larger variety of radioisotopes by reducing or eliminating the interference of abundant isobars. This is accomplished using a gas-filled cell, in which the gas is carefully chosen to react preferentially with the interfering isobar. Using the ion-optics simulation software, SIMION, to guide the choice of applied fields along the ion path, I am optimizing the characteristics of the beam and so producing the highest ion transmission through the ISA.
Once the beam has been experimentally characterised and transmission has been optimized, the ISA will be used in the measurement of many isotopes previously unstudied at the Lalonde AMS laboratory, including but not limited to 36Cl, 90Sr, and 135,137Cs. 36Cl is an important isotope for age determination, paleoclimate studies, and meteorite or lunar material studies, while 90Sr and 135,137Cs are found in fallout from nuclear weapons tests or nuclear accidents.
Ion Sourcery: When counting atoms, every atom counts!The origin of accelerator mass spectrometry (AMS) and its success as a method for 14C (and other isotopic) dating traces back to the discovery that it’s ubiquitous isobar, 14N, does not produce stable negative ions. Since then, the cesium sputter ion source has been the method of choice for extracting these negative ions. Samples from all over the world, used for all kinds of research, are chemically prepared and pressed into identical targets which are injected individually into the ion source for extraction into the accelerator. Inside the ion source, positively charged cesium ions are accelerated by an electric potential difference until they collide with the sample. Carbon atoms within the sample are liberated and obtain an extra electron as they pass through a thin layer of cesium on the surface of the target. The resulting negative ion beam is accelerated by the same potential difference and injected into the accelerator.
Radiocarbon and stable carbon isotopic measurements of dissolved inorganic carbon (DIC) in Baffin BayThe oceans store around half of the carbon dioxide (CO2) emitted into the atmosphere from fossil fuels as dissolved inorganic carbon (DIC), holding ~38,000 GtC and making it the largest marine carbon reservoir. The Arctic Ocean is a region that is both chemically and ecologically sensitive, and little is known about the impacts of climate change on the marine carbon cycle of this region and on atmospheric CO2). Baffin Bay is an ocean basin that feeds cold, fresh surface water into the Labrador Sea, critical for deep water formation and the ‘engine’ driving global deep ocean circulation. The residence time of water in Baffin Bay remains an area of scientific debate, with estimated ventilation times ranging from 77 to 1,450 years.
Source and age of CO2 emissions in the riparian zone adjacent to farm fieldsThe carbon cycle is comprised of 3 main reservoirs: the atmosphere, oceans and the terrestrial biosphere, in which carbon cycles through. This study looks at the contribution of soil respiration to the carbon cycle. The soil cores were collected outside of Ottawa from farm fields and the adjacent riparian zone. The atmosphere currently holds around 800 gigatons of carbon which equates to around 400 ppm of CO2. It is crucial to understand respiration of sequestered carbon which is released as CO2 back into the atmosphere. As this allows for the calculation of a rate at which the sequestered carbon is released as CO2 by respiration.
“I truly enjoy doing research, as there are so many questions one can ask and so many possibilities to answer them, while learning something new each and every day.”