Mapping and Interpretation of Background Levels of Lead Concentrations in Natural Soils A case study of Ale municipality Master of Science Thesis in the Master’s Programme Infrastructure and Environmental Engineering PETRA ALMQVIST, ROBERT ANDERSON Department of Civil and Environmental Engineering Division of GeoEngineering CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2014 Master’s Thesis 2014:41 MASTER’S THESIS 2014:41 Mapping and Interpretation of Background Levels of Lead Concentrations in Natural Soils A case study of Ale municipality Master of Science Thesis in the Master’s Programme Infrastructure and Environmental Engineering PETRA ALMQVIST, ROBERT ANDERSON Department of Civil and Environmental Engineering Division of GeoEngineering CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2014 Mapping and Interpretation of Background Levels of Lead Concentrations in Natural Soils - A case study of Ale municipality Master of Science Thesis in the Master’s Programme Infrastructure and Environmental Engineering P. ALMQVIST, R. ANDERSON © P. ALMQVIST, R. ANDERSON, 2014 Examensarbete / Institutionen för bygg- och miljöteknik, Chalmers tekniska högskola 2014:41 Department of Civil and Environmental Engineering Division of GeoEngineering Chalmers University of Technology SE-412 96 Göteborg Sweden Telephone: + 46 (0)31-772 1000 Cover: Interpolation map for the Nödinge profile and characteristic forest of Ale. Photo: Petra Almqvist Name of the printers / Department of Civil and Environmental Engineering Göteborg, Sweden 2014 Mapping and Interpretation of Background Levels of Lead Concentrations in Natural Soils - A case study of Ale municipality Master of Science Thesis in the Master’s Programme Infrastructure and Environmental Engineering PETRA ALMQVIST, ROBERT ANDERSON Department of Civil and Environmental Engineering Division of GeoEngineering Chalmers University of Technology ABSTRACT Based on unexpectedly high background lead levels measured in peat soil in Ale municipality in 2011, a further, more comprehensive investigation of lead concentrations in Ale forests was required. Ale municipality, bordering the Göta River and the E6 and E45 highways to the east, has a long industrial history, but is currently undergoing residential growth and development. Much of Ale is characterized by large north-south ridges with outcropping metamorphic rocks of the fennoscandian shield and very little soil cover. Most of the natural soil studied could be classified as peat or mor forest soil, which is highly organic, and known to retain metals. Three west-east profiles of 2km in length were studied in the municipality, along with a small reference area in the furthest, most remote corner of Ale. A total of 104 soil samples, taken at a depth of 10cm, were sent to laboratory for metal analysis. The mean concentrations of total lead in each profile, including the reference area, were found to far exceed the Swedish EPA's generic guideline value (KM), with very few samples below this 50 mg/kg TS level. Cadmium and arsenic levels were also found to exceed guideline values in all three profiles. A correlation analysis was conducted to investigate the effect of elevation, distance to the E45 highway, northing, dry content, and soil type on the concentration of lead, arsenic and cadmium. Generally weak correlations were observed, except for dry content, which showed some stronger correlation for arsenic and cadmium. The spatial correlation of the data was modeled using ordinary kriging, and interpolation of the data was achieved using the SADA software. The resulting semi-variogram and profile mapping shows fairly good spatial correlation and some localized pattern of the lead deposition. As a result of the investigation, it can be said that the lead deposition pathways for the area studied are quite unclear, and it is likely that much of it could be attributed to long range sources, given the lack of correlation with distance to the highway and industry. An assessment of the risk of the lead concentrations to human health is difficult, since it depends on several unanswered questions, such as the potential exposure and bioavailability of lead from the organic soil. Key words: Contaminated land/soil, Lead, Natural soil, Kriging, Mapping, Peat, Background levels I II Table of Contents 1 INTRODUCTION 1 1.1 Problem description 1 1.2 Aim 2 1.3 Disposition 2 2 THEORETICAL BACKGROUND 3 2.1 Natural soils 3 2.1.1 Peat 4 2.1.2 Lithosol 5 2.2 Lead 6 2.2.1 Natural and background contents of lead 6 2.2.2 Lead sources 10 2.3 Guideline values 12 2.3.1 Generic 12 2.3.2 Site-Specific 12 2.4 Statistics 12 2.4.1 Statistical parameters 13 2.4.2 Random sampling 13 2.4.3 Correlation 13 2.4.4 ANOVA 14 2.4.5 Kriging 14 3 STUDY AREA 17 3.1 Previous study of Skårdal Skans 18 3.2 Local sources of lead 20 4 METHOD 23 4.1 Sampling Plan 23 4.2 Sampling 26 4.2.1 Procedure 26 4.2.2 Soil Type 26 4.2.3 GPS Correction 27 4.2.4 Elevation 29 4.3 Analysis 30 4.3.1 Laboratory Analysis 30 4.3.2 Software 30 4.4 Human health risk assessment 31 4.5 Mapping and Interpolation 31 5 RESULTS 33 CHALMERS Civil and Environmental Engineering, Master’s Thesis 2014:41 III 5.1 Lab results 33 5.1.1 Surte 36 5.1.2 Bohus 37 5.1.3 Nödinge 37 5.1.4 Reference area 38 5.2 Correlation 39 5.2.1 Distance to E45 39 5.2.2 To % dry substance 40 5.2.3 To northing 41 5.2.4 To elevation 42 5.2.5 To soil type 43 5.3 ANOVA 44 5.3.1 Lead 44 5.3.2 Arsenic 44 5.4 Mapping and Interpolation 45 5.4.1 Correlation Modeling 46 5.4.2 Surte 47 5.4.3 Bohus 48 5.4.4 Nödinge 48 5.5 Human health risk assessment 49 5.6 Comparison with Previous Study in Skårdal Skans 49 6 DISCUSSION 51 6.1 Methodology 51 6.2 Results 51 6.2.1 Elevation , Northing and Distance to E45 52 6.2.2 Soil Type and % Dry Substance 53 6.2.3 ANOVA 53 6.2.4 Spatial Correlation and Interpolation 53 6.2.5 Human health 54 6.2.6 Comparison to Previous Study 55 7 CONCLUSIONS AND RECOMMENDATIONS 57 8 REFERENCES 59 APPENDIX I - MAP OF LEAD LEVELS, ALE 63 APPENDIX II - LAB ANALYSIS REPORTS 65 CHALMERS, Civil and Environmental Engineering, Master’s Thesis 2014:41 IV Figures and Tables Figure 1.1: Disposition of the thesis .............................................................................. 2 Figure 2.1: Schematic figure of soil layer order ............................................................ 3 Figure 2.2: Dominating top soil layers of Sweden (SLU, 2006) ................................... 4 Figure 2.3: Levels of lead in the mor layer to the left, and in glacial till to the right (Johansson et al., 2001) (SGU, n.d a). ........................................................................... 8 Figure 2.4: Lead emissions to air in Sweden between 1990-2011 (SEPA, 2013) ....... 11 Figure 2.5: Empirical semi-variogram (ArcGIS, 2012) ............................................... 15 Figure 2.6: Spherical modeled semi-variogram (ArcGIS, 2012) ................................. 15 Figure 2.7: Fitted semi-variogram (ArcGIS, 2012) ..................................................... 16 Figure 3.1: Map of Ale municipality. The Göta River and E45 mark the western boundary (Ale Kommun, 2013) ................................................................................... 17 Figure 4.1: Profiles of initial interest. (Google, 2013) (SGU, 2013) ........................... 23 Figure 4.2: Overview map of the three profiles ........................................................... 24 Figure 4.3: Stratified random sampling plan over 60m grid. ....................................... 25 Figure 4.4: Reference sampling plan east of Skepplanda (Google, 2013) ................... 26 Figure 4.5: Sample extraction and bagging from peat soil (left) and mor soil (right). Photo: Petra Almqvist .................................................................................................. 27 Figure 4.6: Actual sampled locations (green) vs. intended sampling points (pink). ... 28 Figure 4.7: GPS Route overlays. A-Nödinge, B-Bohus, C-Surte ................................ 29 Figure 4.8: GPS Overlay with Elevation ..................................................................... 30 Figure 4.9: Correlation modelling inputs (SADA, 2013) ............................................ 32 Figure 5.1: Distribution of lab results for lead, Surte profile. ...................................... 34 Figure 5.2: Distribution of lab results for lead, profile Bohus ..................................... 34 Figure 5.3: Distribution of lab results for lead, profile Nödinge ................................. 35 Figure 5.4: Distribution of lab results for lead, reference area .................................... 35 Figure 5.5: Results summary for the three profiles and reference area, mg/kg TS ..... 36 Figure 5.6: Lead levels found in the three profiles plotted against their distance to the road E45. ...................................................................................................................... 40 Figure 5.7: Lead level correlation to %dry substance, for the three profiles and the reference area. .............................................................................................................. 41 Figure 5.8: Lead levels correlation to Northing coordinates, the three profiles and the reference area. .............................................................................................................. 42 Figure 5.9: Lead levels vs. Elevation ........................................................................... 43 Figure 5.10: Comparison of lead