Digestion Of Epiphytic Lichens For Analysis By ICP-MS, As Applied To Monitoring Atmospheric Heavy Metals by 0 Jocelyn Ann Tucker, B.Sc. (Hons.) A thesis submitted to the School of Graduate Studies in partial fulfilment of the requirements for the degree of Master of Science Environmental Science Programme Memorial University ofNewfoundland August 2003 St. John' s Newfoundland To Marleen, ii Abstract Lichens are excellent biomonitors. This study was undertaken to develop and refine a partial digestion procedure for lichen, suitable for ICP-MS analysis of trace elements, for the purpose of environmental monitoring. The developed digestion method consisted of a series of alternating dry and wet ashings utilizing nitric acid and hydrogen peroxide. Acceptable ICP-MS data were obtained for the following suite of elements: Mg, P, Ca, Mn, Co, Zn, Sr, Ba, V, Cr, Fe, Cu, Rb, Cd, Sb, Cs, and Ce. The application of the procedure to lichens from different sites indicated that sites could be distinguished by their trace element concentrations; the elements with differences included elements of environmental interest such as V, Zn, and Cu. The concentrations determined by this research for Newfoundland lichens were generally much lower than those reported by other researchers. The digestion procedure was also applied to different lichen species (Alectoria sarmentosa, Bryoria sp., and Cladonia alpestris) collected at the same site. It was found that different species yielded different trace element information, thus direct comparisons cannot necessarily be made. Digestion residues were examined by SEM-EDX to determine general compositions. The majority of these residual particles had a high silicon content, with varying amounts of other elements, particularly aluminum and potassium; these minerals were silicates, likely to be quartz, feldspars, olivines, garnets, micas, and/or clay minerals. Differences in concentration (as determined by ICP-MS) were observed in lichen samples collected from the same site in 111 consecutive years. Some elements displayed differences between ICP-MS Runs, likely due to sample inhomogeneity. Other researchers have found that elemental concentrations can differ between species, that some elements (e.g. Cr, Fe, Ni, Cu, Zn) have higher concentrations in more polluted areas, and that the levels of some anthropogenic pollutants decrease with distance from the source; each of these points support the findings of this study. iv ACKNOWLEDGEMENTS I would like to express my sincere thanks to the following people who provided assistance with various aspects of the research and writing for this work: My supervisors, Dr. Henry Longerich and Dr. Moire Wadleigh, for their support, expertise, and helpful advice throughout this project. Lakmali Hewa, Dr. Simon Jackson, and Mike Tubrett for their assistance with laboratory work, ICP-MS analyses, and various problems along the way. Pam King for her helpful advice and her assistance with the use of the puck mill. Carolyn Emerson and Lisa Lee for their help with the SEM-EDX work. Dr. Peter Scott for identifying the Cladonia species. Dr. Paul Sylvester for his advice on aspects of the text. Dr. Jun Abrajano, Helen Gillespie, and Pat Horan for lending me laboratory equipment. Maggie Piranian for assistance with the carbon coater. Martin Blake for his advice and for the use of some of his samples. Nicholle Evans for the use of some of her samples. Karen Wade for her assistance with lichen sampling. Wilfredo (Jiggs) Diegor and Dr. A. Oyet for their help with the statistical analysis. Dave Higdon and Darren Smith for their help with assorted computer problems. Various friends and family members for support and encouragement. My parents for their support throughout my university career. v TABLE OF CONTENTS Page ABSTRACT............................................. ............. ......................... ..... ............... 111 ACKNOWLEDGEMENTS .................. ............ ...... .... ......... ... ....... .. ... ....... ...... v TABLE OF CONTENTS .............. ................................................................... v1 LIST OF PLATES................................... ................ .. .. ..................................... x LIST OF FIGURES .......... .. .. .... ..... ............. ...... .......... ... ..... ... ........... .... .... ..... .. x1 LIST OF TABLES........................................................................................... xv CHAPTER 1: INTRODUCTION .................................................................. 1 1.1 Objectives And Scope ........ ............................................................. 1 1.2 Background Information Concerning Lichens .. .. .. .. .. .. .... .. .. .. .. .. .. .. 2 1.2.1 General Information .. ... ... ... ..... .. .. .... .. ... .. .. .. ... .. .. .. .. .. .. .. .. .. 2 1.2.2 Metal Uptake .. ..... .. .. .. .. .. .... .. .. .. .... .. ...... .. .... .. .. .... .. .. .. ... .. .. .. 4 1.2.2.1 Particulate Entrapment ......... ...... ...... .. ...... .... ... .. 4 1.2.2.2 Ion Exchange .............. .............. ......................... 4 1.2.2.3 Intracellular Uptake .. .................. ........ .......... ..... 5 1.3 An Overview Of Atmospheric Pollution ............. ............... ......... .... 6 1.3 .1 General Information .. .. .. ... .. .. ... .. .... .. .. .. .. ... .. .. .. .. ... .. .. .. .. .. .. 6 1.3 .2 Atmospheric Aerosols .. ... .... .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. ... .. .. 6 1.3 .2.1 Natural Atmospheric Aerosols ........ ... ............... 7 1.3.2.2 Anthropogenic Atmospheric Aerosols.............. 8 1.3.2.3 Composition Of Atmospheric Aerosols............ 9 1.4 Sources OfMetals In The Environment.......................................... 10 1.5 Description OfiCP-MS ................................................................... 12 1.6 Literature Review ............................................................................ 13 1.6.1 Digestion Literature .......................................................... 13 1.6.2 Lichen Literature .............................................. ................ 15 CHAPTER 2: METHOD AND METHOD DEVELOPMENT .... .. ............. 19 2.1 Sample Collection ....... ........... ... ........ .......... ........ ... ... ...................... 19 2.1.1 Sampling Protocol ...... ...................................................... 19 vi 2.1.2 Collection OfLichen From Trees..................................... 20 2.1.3 Collection OfLichen From The Ground ...................... .. .. 21 2.1.4 Lichen Sampling Sites ........ .. .............. .. .......... .............. .. .. 21 2.2 Sample Treatment Prior To Digestion .. .. ................ ............ .......... .. 22 2.2.1 Storage And Drying................................................ .. ........ 22 2.2.2 Cleaning .. .. .... ............. ........ .. .. ... .. ... ... ... ... .. .... ...... .......... ... 22 2.2.3 Crushing ... .... .. .. ... ........ .. ...... .. .. ......... .. ....... ......... .. .. .. ...... .. 23 2.3 Sample Digestion .. .. ...... .. ...... ........ .. .. .. .. ........................................ ... 25 2.3.1 Development Of The Digestion Procedure.... .. .............. .. 25 2.3 .2 Rationale Of Sample Selection .. .......... ............ ...... .... .. .. ... 27 2.3.3 SEM-EDX Analysis.... .. ................................................... 34 2.4 ICP-MS Analysis ............................... .. .. ...................................... ... 35 CHAPTER 3: RESULTS AND DISCUSSION............................ ................. 43 3.1 Results . ............. ................................... ............................. ............... 43 3 .2 Digestion Procedure .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 48 3 .2.1 In General .. .. .. .. .. .. .... .. .. .. .. .. .. ... .. .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 48 3.2.2 SEM-EDX Analysis................................................ .. ....... 49 3 .2.2.1 Residual Particles .. ...... .. ...... ............... .. ............ 49 3.2.2.2 Surface Particles .. .............. ................................ 53 3.3 Evaluation Of Analytical Data............................................... .. ....... 55 3.3.1 ICP-MS Instrument Data Quality..................................... 55 3.3.2 Duplicates ................................................... ...................... 58 3.3.2.1 Waters 120 Run......................... .. ........ .. ............ 58 3.3.2.2 Waters 903 Run........ .. ............................ ........... 59 3.3.3 Evaluation Ofindividual Elements .................................. 59 3.3.3.1 Unsuitable Elements........ .......................... ........ 60 3.3.3.1.1 Silver (Ag) ............................... .. ......... 60 3.3.3.1.2 Bromine (Br), Chlorine (Cl), Iodine (1), and Mercury (Hg) .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 61 3.3.3.1.3 Arsenic (As) and Selenium (Se) ......... 63 3.3 .3 .1.4 Aluminium (Al) .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 64 3.3.3.1.5 Boron (B)............................................ 65 3.3.3.1.6 Lead (Pb) ................ .. ...................... .... 65 3.3.3.2 Suitable Elements.................... .......................... 66 3.3.3.3 Elements That Could Be Deemed Unsuitable ... 68 3.3.3.3.1 Sulphur (S) .......... ........ ........ .... .. .. .. ...... 69 3.3.3 .3.2 Nickel (Ni) .................................. ........ 69 3.3.3 .3.3 Molybdenum (Mo)