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Unscrambling Contaminant Mixtures to Determine their Chemical Fingerprints

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Many contaminated sites have mixed plumes or contaminants of concern from multiple potential sources. Examples of mixed plumes could include mixed free phase petroleum plumes (e.g. condensate) or polycyclic aromatic hydrocarbons (PAHs) from crude oil spills mixing with upstream or local anthropogenic sources (storm water runoff) of PAHs in sediments.

There are several advanced statistical techniques that can be used to determine the number and different sources of contaminant present on the site. In addition, these statistical tools can also apportion the amount of contaminants in each sample, thereby allowing liability to be distributed according the chemistry of the contaminants and those responsible for the release. Apportionment is important for litigious cases as it allows the calculation of who should pay for what portion of the cleanup.

Tools using positive matrix factorization (PMF) have been developed by US EPA but are no longer being supported are still publicly available to use. These techniques can be applied to many different chemical mixtures such as condensates or mixed petroleum hydrocarbon plumes. We have successfully applied the technique to PAHs from sediment data to allocate the source of the PAHs in the sediments to sources identified by the models. Unfortunately, these models are not definitive and provide multiple conclusions depending on their starting point which can make interpretation difficult and sometimes questionable, especially for litigation proceedings.

This presentation provides a summary of statistical tools used for chemical fingerprinting as well as the use of PMF and Bayesian modelling in order to provide some guidance on model usage for contaminant apportionment. The models need to be applied conservatively and require chemistry interpretation to elucidate what end members have been identified by the model and if those end members make sense. The models will be applied to a real case study scenarios to demonstrate their application.

Lawyers, regulators and environmental professionals involved in spill monitoring and liability determination will find this presentation educational in how these statistical models are able to determine sources and amounts of those sources of contaminants on site.

Published in: Environment
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Unscrambling Contaminant Mixtures to Determine their Chemical Fingerprints

  1. 1. © 2018 Chemistry Matters Inc. Making chemistry data meaningful Unscrambling Contaminant Mixtures to Determine their Chemical Fingerprints and Sources • Court D Sandau1,2, Lacey Harbicht1, Phil Richards1, Khalid Lemouji2 • 1 Chemistry Matters Inc., Calgary, AB • 2 Statvis Analytics Inc., Edmonton, AB
  2. 2. © 2018 Chemistry Matters Inc. Copyright Statement All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of Chemistry Matters Inc. 2Envirotech 2018 - Calgary, Alberta
  3. 3. © 2018 Chemistry Matters Inc. Topics of Presentation • Environmental forensics and chemical patterns • What is source apportionment? • What is Positive Matrix Factorization? • Case Study – Natural vs. Oil Spill PAHs Envirotech 2018 - Calgary, Alberta 3
  4. 4. © 2018 Chemistry Matters Inc. Progression of Environmental Forensics 4Envirotech 2018 - Calgary, Alberta Background Sample 1 PCA HCA Individual Sample Pattern Analysis Double Ratio Plots / Diagnostic Ratios Chromatogram Analysis Next Step: Source Apportionment 0.00% 10.0% 50% 35% 2.5% 3.0% 2014_OctNov_AMS09 Source_1 Source_2 Source_3 Oil Sands Source_5 Forest Fire Sample A
  5. 5. © 2018 Chemistry Matters Inc. Chemical Patterns Are Everywhere 5Envirotech 2018 - Calgary, Alberta 0 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146. 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 Percent (%) Aroclor 1248: G3.5 0 2 4 6 8 10 12 14 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146. 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 Percent (%) Aroclor 1254: A4 0 -4 -8 -120.0% 2.0% 4.0% 6.0% 8.0% 10.0% 12.0% 12 13 14 15 16 17 18 19 20 21 -Z number Carbon number Naphthenic Acids in Weathered Oil 0 -2 -4 -6 -8 -10 -12 PCBs PAHs Naphthenic Acids
  6. 6. © 2018 Chemistry Matters Inc. Chemical Fingerprints 6Envirotech 2018 - Calgary, Alberta Esso Shell
  7. 7. © 2018 Chemistry Matters Inc. Chemical Patterns • All contamination has a potential chemical signature • If the chemical signature is unique to the contamination, then it will be the fingerprint of the contamination • There are environmental weathering processes that can alter a fingerprint over time that must be considered – BUT - weathering is predictable and is determined by the physical-chemical properties of the compounds • Like chemicals – move together in the environment Envirotech 2018 - Calgary, Alberta 7
  8. 8. © 2018 Chemistry Matters Inc. Source Apportionment • Determining the proportion of the source(s) of the contamination in a sample and at a contaminated site • Also known as receptor modelling 8Envirotech 2018 - Calgary, Alberta 0.00% 10.0% 50% 35% 2.5% 3.0% 2014_OctNov_AMS09 Source_1 Source_2 Source_3 Oil Sands Source_5 Forest Fire Sample A Source of PAHs Based on Toxicity
  9. 9. © 2018 Chemistry Matters Inc. Where can source apportionment be used? • Air pollution – PAHs, metals on particulate matter, VOCs • Mixing condensate and gasoline plumes • Contaminated sites with multiple sources – Superfund sites – PCBs, PAHs, Dioxins/Furans • Crude oil spills in rivers and ocean 9Envirotech 2018 - Calgary, Alberta
  10. 10. © 2018 Chemistry Matters Inc. Positive Matrix Factorization (PMF) • Developed by Paatero (UofHelsinki) for air pollution • Multivariate technique decomposes a matrix of analytical results into two matrices: – factor contributions (how much) and factor profiles (fingerprint) • Factor profiles still require interpretation to determine sources 10Envirotech 2018 - Calgary, Alberta
  11. 11. © 2018 Chemistry Matters Inc. Keys to Successful PMF • Consistent analytical data for all sampling points • End-members (sources) well represented in sampling points included in PMF analysis • Models are not definitive, multiple conclusions 11Envirotech 2018 - Calgary, Alberta
  12. 12. © 2018 Chemistry Matters Inc. Case Study 12Envirotech 2018 - Calgary, Alberta PAHs in river after an oil spill
  13. 13. © 2018 Chemistry Matters Inc. Why are PAHs the focus – post oil spill? • Not very volatile • Not soluble in water/bind to organic carbon in sediment • Resist biodegradation • Potential to bioaccumulate (very minimal) • Known toxicity (mediated through Ah receptor) • Percentage (<1-10%) quantities in crude oil – High enough concentrations to see in environment 13Envirotech 2018 - Calgary, Alberta toluene 3800 Pa 470 mg/L 2.69 10.4 Pa naphthalene 31 mg/L 3.37 0.0161 Pa phenanthrene 1.1 mg/L 4.46 0.0006 Pa pyrene 0.13 mg/L 8.8 Volatility Solubility KOC
  14. 14. © 2018 Chemistry Matters Inc. Organic carbon drives sediment concentrations • Once equilibrium is reached, organic carbon drives PAH concentrations in sediments • Equilibrium is reached quite quickly 14 1979 Publication describes contaminants sorption to organic carbon Envirotech 2018 - Calgary, Alberta
  15. 15. © 2018 Chemistry Matters Inc. PAHs in Rivers 15 • Rivers are catchment areas, sinks for sediments, especially reservoirs • PAHs have long half-lives • PAHs are ubiquitous All rivers in Alberta have PAHs – In sediment – In organic rich phases – Most are petrogenic origin – Above Tier 1 guidelines http://www.ec.gc.ca/doc/publications/pollution/COM1396/index-eng.htm 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 N aphthalene C1 naphthalene C2 naphthalene C3 naphthalene C4 naphthalene Fluorene C1 fluorene C2 fluorene C3 fluorene Phenanthrene/Anthracene C1 phenanthrene/anthracene C2 phenanthrene/anth. C3 phenanthrene/anth. C4 phenanthrene/anth. D ibenzothiophene C1 dibenzothiophene C2 dibenzothiophene C3 dibenzothiophene C4 dibenzothiophene Fluoranthene/Pyrene C1 fluoranthene/pyrene C2 fluoranthene/pyrene C3 fluoranthene/pyrene C4 fluoranthene/pyrene Benz(a)anthracene/Chrysene C1 B(a)A/chrysene C2 B(a)A/chrysene C3 B(a)A/chrysene C4 B(a)A/chrysene CTRL S/C-1 Background PAH Pattern Envirotech 2018 - Calgary, Alberta
  16. 16. © 2018 Chemistry Matters Inc. PAHs on Sediments • Lots of PAHs in sediments 16Envirotech 2018 - Calgary, Alberta
  17. 17. © 2018 Chemistry Matters Inc. What has more PAHs? Oil Spill or Yearly Sediment Load? • Back of the envelope calculation: is a rough calculation, typically jotted down on any available scrap of paper such as an envelope. It is more than a guess but less than an accurate calculation or mathematical proof. (Wikipedia) 17Envirotech 2018 - Calgary, Alberta
  18. 18. © 2018 Chemistry Matters Inc. 18Envirotech 2018 - Calgary, Alberta • Oil spill of 225 m3 which is ~198,000kg • ∑PAH16 measured concentration of 165 mg/kg • ∑PAH16 released: 33 kg • Sediment in large river over 1 year (mostly during freshet) is 3,000,000 tons • Average ∑PAH16 measured in upstream locations was 0.211 mg/kg • ∑PAH16 in river sediment flowing by breakpoint each year is 6,330 kg• Oil spill contributes less than 1% to the yearly PAHs passing by breakpoint Back of the Envelope Calculation Source apportion that!
  19. 19. © 2018 Chemistry Matters Inc. Setting Up Data for PMF • CSV files with sample IDs and GPS locations • CSV file with sample IDs, compound concentrations • Compound data needs imputations for missing values – Zero to maximum for missing values – Kaplan-Meyer substitution for NDs • Data normalization completed in PMF 19Envirotech 2018 - Calgary, Alberta
  20. 20. © 2018 Chemistry Matters Inc. Geospatial Analysis and Selection • Selection tool for selecting specific data points to look at 20Envirotech 2018 - Calgary, Alberta
  21. 21. © 2018 Chemistry Matters Inc. Correlation/Heatmap Analysis • Heatmap shows what compounds are related 21Envirotech 2018 - Calgary, Alberta
  22. 22. © 2018 Chemistry Matters Inc. Principal Component Analysis • Explore the samples driving variability of your dataset 22Envirotech 2018 - Calgary, Alberta Oil Related Samples Upstream of POE Background Signal
  23. 23. © 2018 Chemistry Matters Inc. PMF 23Envirotech 2018 - Calgary, Alberta
  24. 24. © 2018 Chemistry Matters Inc. PMF - Sources • Identified two background sources and the spilled oil 24Envirotech 2018 - Calgary, Alberta Petrogenic Background Petrogenic Background Source Oil
  25. 25. © 2018 Chemistry Matters Inc. PMF Results 25Envirotech 2018 - Calgary, Alberta PCA Page PMF Page No Source Oil. Good! Upstream of POE
  26. 26. © 2018 Chemistry Matters Inc. PMF Results 26Envirotech 2018 - Calgary, Alberta 65% of PAHs from Source Oil Indicator DBTs of Source Oil
  27. 27. © 2018 Chemistry Matters Inc. Conclusions • Provides client (and stakeholders) confidence in where oil was found • Allows client to focus on those areas in follow up cleanup and monitoring • Clarity in source of PAHs in the samples as well as provides perspective on the risk associated with PAHs from the spill 27Envirotech 2018 - Calgary, Alberta
  28. 28. © 2018 Chemistry Matters Inc. Thank you for your attention Contact Info: Chemistry Matters Inc. Court Sandau Cell: 403.669.8566 Email: csandau@chemistry-matters.com www.chemistry-matters.com Visit my website and sign up for email for automatic receipt of my blogs. Envirotech 2018 - Calgary, Alberta 28

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