An Analysis of Elemental and PAH Concentrations in Soils Due to Vehicular Traffic Along the Manali-Leh Highway, Northwestern
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An analysis of elemental and PAH concentrations in soils due to vehicular traffic along the Manali-Leh Highway, northwestern Himalaya, India A thesis submitted to the Graduate School of The University of Cincinnati in partial fulfilment of the requirements of the degree of Master of Science in Department of Geology of McMicken College of Arts and Sciences by Rajarshi Dasgupta B.Sc. Honours (Geography), University of Calcutta, Kolkata, India, 2005 M.A. (Geography), Jawaharlal Nehru University, New Delhi, India, 2008 March 2014 Advisory Committee: Dr. Brooke E. Crowley (Chair) Dr. J. Barry Maynard (Member) Dr. Aaron F. Diefendorf (Member) Dr. Lewis A. Owen (Member) ABSTRACT Vehicles constitute one of the most important sources of environmental pollution. Most studies on roadside soil pollution have been carried out in urban areas, where the main fuel used is petrol. These studies indicate that the concentrations of heavy metals associated with vehicular movement decrease with increasing distance from the highway and with depth in the soil profile. In contrast, most of the vehicles that travel along the Manali-Leh Highway in northwestern Himalaya, India are fueled by diesel. The present study assessed the concentrations of the heavy metals (Al, Fe, Cr, Cu, Pb, Ni, Co, Zn, V and Ba), total organic carbon (TOC), total sulphur and polycyclic aromatic hydrocarbons (PAHs) concentrations along this highway. Soil samples were collected from four sites at incremental distances from the highway (0m, 2m, 5m, 10m, 20m and 150m) and from three depths in the soil profile (3cm, 9cm and 15cm). The concentrations of the various elements were measured using X-ray Fluorescence Spectrometry and an Elemental Analyzer, while those of the PAHs using Gas Chromatography-Mass Spectrometry. Results suggest that heavy metal concentrations are generally very low compared to those in other published studies. There is no clear relationship between concentrations of heavy metals and either distance from the highway or depth within the soil profile. However, elevated concentrations of sulphur are found in the soils. Cluster analysis was applied to determine the association of various elements in the soil. There are six main clusters, which are interpreted to be the organic, clay, carbonate, iron oxides, sand and silt and windblown deposited fractions of the soil. This indicates that most of the metals are associated with the natural fractions of the soils. Sulphur is found to be clustered with the organic fraction of the soils. PAHs are also found, albeit in very low concentrations compared to other published studies on highways. The main conclusion of this study is that at present, the amount of heavy metals in the soils along the Manali-Leh Highway is very low, but there are elevated sulphur concentrations. High sulphur concentrations can increase soil acidity, which can have important edaphic implications. The strong association of sulphur with TOC, Pb and Zn, as well as a strong correlation between sulphur and PAHs suggests that the regular use of the road by an increasing number of vehicles can contaminate the soil further with metals and PAHs, which may then move up the food chain i and directly affect human health. The results of this study imply that monitoring of heavy metals alone suggests that there is no contamination of the soils, but by measuring sulphur, it has been shown that that there is, in fact, considerable human impacts along the highway. Therefore, both inorganic and organic pollutants should be regularly monitored in the soils along this highway. ii iii ACKNOWLEDGEMENTS I would like to mention about a few individuals without whose continuous and endearing support, this thesis would not have seen the light of the day. First and foremost is my advisor, Dr. Brooke Crowley, who decided to take me under her tutelage, and supervised a thesis on a topic that was totally new to me. She has spent countless hours discussing my (often crazy!) research ideas, refining funding applications and reading many drafts of the thesis. Thank you very much Dr. Crowley. It was a pleasure to work with and learn from you. I particularly enjoyed learning the nuances of doing and communicating science. In the same vein, I wish to extend my sincere appreciation to the other members of my advisory committee, namely Dr. Barry Maynard, Dr. Aaron Diefendorf and Dr. Lewis Owen. In particular, Dr. Maynard was like a second advisor to me and provided many crucial inputs and suggestions at various stages of this project; Dr. Diefendorf taught organic and isotopic geochemistry to a complete newbie in the field, while Dr. Owen chipped in with his expertise on the physical environment of the study area. Thank you gentlemen- I gratefully acknowledge your support. Thanks are also due to the other faculty and staff members of the Department of Geology, University of Cincinnati (UC), especially to Dr. Tom Algeo for allowing me to work in the Fisk Laboratory, Drs. Warren Huff and Yurena Yanes for always maintaining an interest in my research, Drs. Aaron Diefendorf and Andy Czaja for organizing the weekly colloquiums on Fridays, which helped me (and I am sure, all of us) to unwind a bit at the end of the week, and Mrs. Krista Smilek for taking care of the administrative nitty-gritty of pursuing graduate studies at UC. I was fortunate to be part of a very vibrant and extremely diverse research group, and my lab mates were a source of joy and support. So thumbs up to you Jani Sparks, Stella Mosher, Eric Baumann, Matt Vrazo and Bevin Kenney. I acknowledge also the camaraderie of other graduate students in the department, especially Gary Motz, Julia Wise, Kelsey Feser and Chris Aucoin. Gary and Jules, I can never forget or thank you both enough for all that you have done for me ever since I arrived in Cincinnati; Kels, I really appreciate your general support and especially your words of wisdom on all things statistical when I was stuck and iv did not know what to do; Chris, I know I spent very little time as your ‘office’ mate, but I really enjoyed our conversations whenever I was in the office and will miss them. The University of Cincinnati provided me with not only the resources to carry out my research, but also financial support to sustain myself, in terms of a graduate assistantship. Funding for this project was obtained through a UC Research Council faculty research grant to my advisor and a Sigma Xi grant-in-aid of research (No. G20131015322038) to myself. No words are ever enough to thank my parents for being the biggest source of inspiration and support in my life. I know it would sound cliché, but Mum and Bapi, believe me- you two are THE BEST!! I also want to thank my best friends, Sumanta Chakraborti and Dipanjan Mukherjee, for showing me the signs of positivity even when things were a bit down. Finally to the Almighty for keeping me in good health and providing me with this opportunity to study in the United States. v CONTENTS ABSTRACT .................................................................................................................................................. i ACKNOWLEDGEMENTS ...................................................................................................................... iv LIST OF FIGURES ................................................................................................................................. viii LIST OF TABLES ...................................................................................................................................... x 1. INTRODUCTION: ................................................................................................................................. 1 1.1. Heavy metals in roadside soils: ............................................................................................................ 1 1.2. Elemental characteristics of petrol (gasoline) and diesel exhaust: ....................................................... 3 1.3. Sulphur in roadside soils: ...................................................................................................................... 4 1.4. Polycyclic aromatic hydrocarbons in roadside soils: ............................................................................ 6 1.5. Study aim and objectives: ..................................................................................................................... 7 2. MATERIALS & METHODS: .............................................................................................................. 8 2.1. Study area: ............................................................................................................................................ 8 2.2. Sample collection and preparation: ....................................................................................................... 9 2.3. Analytical methods: ............................................................................................................................ 10 2.3.1. X-Ray Fluorescence: ....................................................................................................................... 10 2.3.2. Carbon-Sulphur Analysis: ............................................................................................................... 10 2.3.3. PAH Analysis: ................................................................................................................................. 11 2.4. Data processing and analyses: ...........................................................................................................