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

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

3. pH5.566.577.5 Cd3.544.555.5 Cu,Cr55.566.57 Pb,Hg7891011 RETENTION INDICATOR (excerpt) RI depends on pH, type of metal, content of organic material, … Step 1Step 2 Step 3a Step 3b Step 4 Step 5 Steps Results Retention indicator (matrix flow) and transport rate The retardation of heavy metal cations in the soil matrix was estimated. Safety and Environmental Technology Group 0 1 3 5 7 9 3456789101112.0 Retention indicator Transport rate (mm/year) FIELD STUDIES

4. Cd 2+, site A Cd 2+, site B Tons / year / kg waste Time (years) Tons / year / kg waste Application of the method to landfill sites

5. Safety and Environmental Technology Group Results and conclusions A simplified method was developed for the fate assessment of heavy metals in soil/rock. The method can be used to estimate transport 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.

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

9. Safety and Environmental Technology Group Integration of the method in multimedia fate models. Upper soil layer (top 30 cm) Deep soil layers (below 30 cm) Groundwater Fresh water Sediments Air 1.Description of a hypothetical “typical” European site 2.Calculation of heavy metal transport rates at this site 3.Definition of rate constants (input to multimedia models)