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Fate modeling: Soil transport of heavy metal emissions from landfills to the groundwater 

International Waste Management and LCA Session C Prague, April 15-16, 2004. Fate modeling: Soil transport of heavy metal emissions from landfills to the groundwater . Stefanie Hellweg , Ulrich Fischer, Thomas Hofstetter, Konrad Hungerbühler.

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Fate modeling: Soil transport of heavy metal emissions from landfills to the groundwater 

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  1. International Waste Management and LCA Session C Prague, April 15-16, 2004 Fate modeling:Soil transport of heavy metal emissions from landfills to the groundwater  Stefanie Hellweg, Ulrich Fischer, Thomas Hofstetter, Konrad Hungerbühler Swiss Federal Institute of Technology Zurich Safety and Environmental Technology Group

  2. The goal was to provide a method for assessing the fate of heavy metals in soil. Small ca-pacity for adsorption Homogeneously low permeability Distance to water:  2 m < 2 m Infiltration rate:  400 mm/a < 400 mm/a Soil layer Macropore flow Large ca-pacity for adsorption High per-meability at some spots pH > 6  2 m < 2 m Matrix flow Small ca-pacity for adsorption pH  6 Large ca-pacity for adsorption Steps Step 1 Step 2 Step 3a Step 3b Step 4 Step 5 Safety and Environmental Technology Group

  3. FIELD STUDIES 9 7 Transport rate (mm/year) 5 3 1 0 3 4 5 6 7 8 9 10 11 12.0 Retention indicator The retardation of heavy metal cations in the soil matrix was estimated. Steps Results Step 1 Step 2 Step 3a Step 3b Step 4 Step 5 Retention indicator (matrix flow) and transport rate RETENTION INDICATOR (excerpt) RI depends on pH, type of metal, content of organic material, … Safety and Environmental Technology Group

  4. Application of the method to landfill sites Cd2+, site A Tons / year / kg waste Cd2+, site B Tons / year / kg waste Time (years)

  5. Results and conclusions • A simplified method was developed for the fate assessment of heavy metals in soil/rock. • The method can be used to estimatetransport rates/times or to define partition rate constants for multimedia fate models. • The influence of spatial variablity was large in case studies. • The uncertainties of the model calculations are high. Safety and Environmental Technology Group

  6. Hellweg, S, Fischer, U, Hofstetter, TB, Hungerbühler, K: Site-dependent fate assessment in LCA: transport of heavy metals in soil, Journal of Cleaner Production, in press (2004)

  7. BACK-UP SLIDES

  8. Application of the method to landfill sites Example Evapotranspiration (40%) Surface run-off (35%) Leaching (25%) Gravel/sand ~ 10 m ~ 2 m Moraine Limestone 0% Macropore flow Soil at site A 50% High per-meability at some spots Distance to groundwater: > 2 m pH > 7, small capacity for adsorption 0% 100% 100% 100% Infiltration rate: 125 mm / y Matrix flow 50% 100% 0% 125 mm/y macropore flow Retention indicator Cd: 5.5 Transport rate Cd: 7 mm/y Transport time Cd: 900-1400 y Safety and Environmental Technology Group

  9. Air Upper soil layer (top 30 cm) Deep soil layers (below 30 cm) Fresh water Groundwater Sediments Integration of the method in multimedia fate models. • Description of a hypothetical “typical” European site • Calculation of heavy metal transport rates at this site • Definition of rate constants (input to multimedia models) Safety and Environmental Technology Group

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