Trees and Pollution: Investigating the Impact of Sulfur Dioxide Using Ring Widths and Stable Isotopes
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TREES AND POLLUTION: INVESTIGATING THE IMPACT OF SULFUR DIOXIDE USING RING WIDTHS AND STABLE ISOTOPES ZACHARY RAWLUK A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENVIRONMENTAL SCIENCE NIPISSING UNIVERSITY SCHOOL OF GRADUATE STUDIES NORTH BAY, ONTARIO © Zachary Rawluk, March 2016 SCHOOL OF GRADUATE STUDIES THESIS/DISSERTATION CERTIFICATE OF EXAMINATION Certificate of Examination Supervisor(s): Examiner(s) Dr. Adam Csank Dr. Daniel Campbell Dr. April James Supervisory Committee: Dr. Adam Csank Dr. April James Dr. Jeff Dech The thesis by Zachary Rawluk entitled Trees and pollution: investigating the impact of sulfur dioxide using ring widths and stable isotopes is accepted in partial fulfillment of the requirements for the degree of Master of Environmental Science January 22, 2016 Dr. Dan Walters Date Chair of the Examination Committee (original signatures on file) Abstract Excessive sulfur dioxide (SO2) pollution released into the atmosphere from mining and smelting operations in northeastern Ontario, Canada has devastated surrounding forest ecosystems. Over the course of the 20th century, smelting operations in Sudbury, Ontario released more than 100 million tonnes of SO2 into the atmosphere. At peak production in 1960, Sudbury smelters generated 2.56 million tonnes of SO2 that represented approximately 4% of global sulfur emissions. Past studies have shown that in high enough doses, SO2 acts as a toxic environmental pollutant that can be associated with decreased growth in the annual growth rings of trees. However, the application and use of stable carbon-13 (δ13C) and sulfur-34 (δ34S) isotopes in dendrochemical studies involving sulfur pollution is still relatively new. This study aims to better understand the influence of atmospheric SO2 pollution loading on nearby forest ecosystems and tree physiology – from both a spatial and temporal perspective by combining tree-ring width and isotope data. Three sample sites along a 110-kilometer northeasterly transect from Sudbury to Temagami were chosen in order to quantify the interplay of pollution and climate. Ring-width and isotope data provided useful information that allowed this study to comment on the magnitude of influence and impact that SO2 pollution had on eastern white pine (Pinus strobus) trees throughout Sudbury’s entire smelting history, as well as the success of Vale’s Emission Reduction Program (ERP) that has reduced overall SO2 emissions by 90% over the last 45 years. Results indicated that the closest study site to Sudbury displayed growth ring trends that were influenced by SO2 during the peak emissions period and isotope data revealed a weakened relationship with climate variables before drastic emission reductions in the 1970s. Ultimately, this study provided 1 results in favour of white pine trees being good biorecorders of anthropogenic SO2 pollution. Because of the influence of SO2 emissions on tree growth and chemistry, failure to identify the associated signals of pollution in tree-ring widths and stable isotope records may lead to biased and inaccurate paleoclimatic reconstructions from regions affected by an increased pollution load. 2 To Nanny, for being the light to guide me in times of darkness. 3 Acknowledgments First and foremost, I would like to offer a big thank you to my supervisors, Dr. Adam Csank (Nipissing University) and Dr. April James (Nipissing University), for your valuable input, advice, guidance and support over the course of developing and conducting my thesis research project as well as throughout the entire duration of the Master of Environmental Science (MESc) program at Nipissing University. You are both greatly respected and admired for the vast amount of knowledge you possess within your fields of specialization. Working with you proved to be extremely beneficial to my development as an inquisitive researcher and scientist, while also allowing me the freedom to critically think and attempt to answer questions on my own at each step of the scientific method. Second, I would like to thank all of the Nipissing University faculty members who were involved with designing and instructing the MESc graduate courses. Our discussions were always thought-provoking and the feedback and constructive criticism provided in class greatly contributed to the evolution and improvement of my thesis. I would also like to thank Mr. Matt Rogers at the University of Alaska Anchorage Stable Isotope Laboratory for his technical assistance in conducting the mass spectrometry work that was required for isotope analysis. I am also grateful to Dr. Jeff Dech (Nipissing University) and Dr. Daniel Campbell (Laurentian University) for their feedback and comments on my written work in their roles as internal and external examiner, respectively. Furthermore, thanks to the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding the research project. Last, but certainly not least, a special thank you to my mom, Megan Williams, for providing constant motivation and encouragement that helped me make it to the finish line. 4 Table of Contents Abstract .............................................................................................................................. 1 Dedication .......................................................................................................................... 3 Acknowledgements ........................................................................................................... 4 Table of Contents .............................................................................................................. 5 1. Introduction ................................................................................................................... 6 1.1. Sudbury mining and smelting history .................................................................. 6 1.2. Trees, pollution and dendrochronology ............................................................... 9 1.3. Project goals and significance ........................................................................... 13 2. Literature review ........................................................................................................ 14 2.1. Carbon isotope theory ........................................................................................ 14 2.2. Sulfur isotope theory .......................................................................................... 19 2.3. Biological and physiological effects of SO2 on plants ....................................... 21 13 34 2.4. Observed impacts of SO2 on ring widths, δ C and δ S isotopes ..................... 22 3. Materials and methods ............................................................................................... 30 3.1. Project overview and study design .................................................................... 30 3.2. Site descriptions ................................................................................................. 31 3.3. Fieldwork and tree-ring data ............................................................................. 34 3.4. Climate records and SO2 emissions data ........................................................... 37 3.5. Sample measurement, dating and preparation .................................................. 37 3.6. Chemical processing of α-cellulose ................................................................... 40 3.7. Isotope ratio mass spectrometry (IRMS) ........................................................... 42 3.8. Statistical analyses ............................................................................................. 43 4. Results and discussion ................................................................................................ 45 4.1. RWI chronologies of White Bear, Hobbs Lake and Kukagami Lake ................. 45 4.2. RWI-climate analysis ......................................................................................... 54 4.3. RWI-pollution analysis ....................................................................................... 59 4.4. δ13C chronologies of White Bear, Hobbs Lake and Kukagami Lake ................. 61 4.5. δ13C-climate analysis ......................................................................................... 64 4.6. δ13C-pollution analysis ...................................................................................... 68 4.7. δ34S analyses ...................................................................................................... 72 5. Conclusions .................................................................................................................. 72 References ........................................................................................................................ 77 Appendices ....................................................................................................................... 85 Appendix I – Figures ................................................................................................. 85 Appendix II – Tables and Images ............................................................................ 103 5 1. Introduction 1.1. Sudbury mining and smelting history Mining, involving the extraction of copper and nickel ores, in the Sudbury region began in the late 1880s (SARA, 2008). The Canadian Copper Company was first to arrive on scene and locate significant nickel deposits. Following the company’s initial