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A method for correlation of gravestone weathering and air quality (SO2), West Midlands, UK A Thesis SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY Michael John Carlson IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Howard D. Mooers, Adviser May 2017 © Michael Carlson 2017 i Acknowledgements I would like to give thanks to my advisor Howard Mooers and my committee members Erik Brown and Laure Charleux for helping see me through to the finish on this thesis. Their guidance and knowledge was invaluable. I also want to thank my wife for being along for the ride. ii Dedication This Thesis is dedicated to my loving grandmother Patricia Carlson. Her support through my education career was endless. iii Abstract From the beginning of the Industrial Revolution through the environmental revolution of the 1970s Britain suffered the effects of poor air quality primarily from particulate matter and acid in the form of NOx and SOx compounds. Air quality stations across the region recorded SO2 beginning in the 1960s however the direct measurement of air quality prior to 1960 is lacking and only anecdotal notations exist. Proxy records including lung tissue samples, particulates in sediments cores, lake acidification studies and gravestone weathering have all been used to reconstruct the history of air quality. A 120-year record of acid deposition reconstructed from lead-lettered marble gravestone weathering combined with SO2 measurements from the air monitoring network across the West Midlands, UK region beginning in the 1960s form the framework for this study. The study seeks to create a spatial and temporal correlation between the gravestone weathering and measured SO2. Successful correlation of the dataset from 1960s to the 2000s would allow a paleo-air quality record to be generated from the 120-year record of gravestone weathering. Decadal gravestone weathering rates can be estimated by non-linear regression analysis of stone loss at individual cemeteries. Gravestone weathering rates are interpolated across the region through Empirical Bayesian Kriging (EBK) methods performed through ArcGIS® and through a land use based approach based on digitized maps of land use. Both methods of interpolation allow for the direct correlation of gravestone weathering and measured SO2 to be made. Decadal scale correlations of gravestone weathering rates and measured SO2 are very weak and non-existent for both EBK and the land use based approach. Decadal results combined together on a larger scale for each respective method display a better visual correlation. However, the relative clustering of data at lower SO2 concentrations and the lack of data at higher SO2 concentrations make the confidence in the correlations made too weak to rely on. The relation between surrounding land use and gravestone weathering rates was very strong for the 1960s-1980s with diminishing correlations approaching the 2000s. Gravestone weathering of cemeteries is highly influenced by the iv amount of industrial sources of pollution within a 7km radius. Reduced correlation of land use and weathering beyond the 1980s is solid grounds for the success of environmental regulation and control put in place across the UK during later parts of the 20th century. v Table of Contents Acknowledgments ................................................................................................. i Dedication ............................................................................................................ ii Abstract ............................................................................................................... iii Table of Contents ................................................................................................. v List of Tables ...................................................................................................... vii List of Figures ................................................................................................... viii 1. Introduction ...................................................................................................... 1 2. Study Area ........................................................................................................ 3 2.1 Environmental Monitoring ................................................................ 5 2.1.1 Marble gravestones and acid deposition ............................. 5 2.1.2 History of air quality monitoring ........................................ 6 3. Methods ............................................................................................................ 7 3.1 The Dataset........................................................................................ 7 3.1.1 Gravestone Dataset ............................................................. 7 3.1.2 Air Quality Data.................................................................. 9 3.2 Generating Weathering Rates.......................................................... 12 3.2.1 Integrative Rate Calculation ............................................. 13 3.2.2 Moving Average ............................................................... 14 3.2.3 Regression Analysis .......................................................... 15 3.3 Interpolation of Gravestone Weathering ......................................... 16 3.3.1 Empirical Bayesian Kriging .............................................. 16 3.3.2 Land use based approach .................................................. 17 3.4 Optimizing IDW Parameters ........................................................... 19 3.4.1 Optimizing Land Use Type Indicator Values ................... 19 3.4.2 Optimizing IDW Power .................................................... 19 3.4.3 Optimizing Radius ............................................................ 20 3.5 Correlation of gravestone weathering rates and measured S02 ....... 21 4. Results/Discussion ......................................................................................... 21 vi 4.1 Decadal weathering rates ................................................................ 21 4.2 Correlation using Empirical Bayesian Kriging (EBK) .................... 24 4.3 Land use based approach ................................................................ 27 4.3.1 Optimum land use indicator values .................................. 30 4.3.2 Optimum IDW power ....................................................... 31 4.3.3 Optimum radius ................................................................ 32 4.3.4 Addressing later decade correlation issues ....................... 33 4.3.5 Gravestone Weathering and SO2 Correlation ................... 35 5. Conclusions .................................................................................................... 41 Bibliography ....................................................................................................... 46 vii List of Tables Table 1. Cemetery Names, Locations and Three Letter Code ............................. 8 Table 2. Air Monitoring Names, Locations and SO2 Measured ......................... 11 Table 3. Monitoring stations available for each decade ..................................... 11 Table 4. Decadal weathering rates calculated using regression analysis ........... 24 Table 5. Estimated weathering rates using EBK ................................................ 26 Table 6. Weathering rates using land use based approach ................................. 38 viii List of Figures Figure 1. Study area and cemetery and monitoring station locations................... 4 Figure 2. Measured SO2 from West Midlands monitoring network .................. 10 Figure 3. Non-linear regression analysis of Mooers et al. (2016) ...................... 12 Figure 4. Typical signal of gravestone weathering ............................................ 14 Figure 5. Inkpen method of calculating weathering rates .................................. 15 Figure 6. Polynomial fitted to cemetery data to generate weathering rates ....... 16 Figure 7. Land use map digitized from aerial imagery ...................................... 18 Figure 8. Assigned weight based on IDW Power .............................................. 20 Figure 9. Plotted rates using Inkpen method ...................................................... 23 Figure 10. Plotted rates using moving average .................................................. 23 Figure 11. Spatial and temporal distribution of rates estimated with EBK ........ 25 Figure 12. Correlation of rates and SO2 using EBK ........................................... 28 Figure 13. Correlation of rates and SO2 for 1960s-1990s (EBK) ....................... 29 Figure 14. Optimizing land use indicator values ................................................ 30 Figure 15. Optimizing the power for the IDW function ..................................... 31 Figure 16. Optimizing radius ............................................................................. 33 Figure 17. Correlation of predicted land use values and weathering rates ......... 36 Figure 18. Correlation of rates and SO2 using land use based approach ............ 39 Figure 19. Correlation of rates and SO2 for 1960s-1980s (land use approach) . 40 1 1. Introduction From the onset of the Industrial Revolution until the environmental revolution of the 1970s (Sale, 1993; McCormick, 2013), Britain was plagued by air pollution from industrial, urban, and residential sources. The largest contributors to air