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

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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
Stefanie Hellweg, Ulrich Fischer, Thomas
Hofstetter, Konrad Hungerbühler
Swiss Federal Institute of Technology Zurich
Safety and Environmental Technology Group
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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 lt 2 m
Infiltration rate ? 400 mm/a lt 400 mm/a
Soil layer
Macropore flow
Large ca-pacity for adsorption
High per-meability at some spots
pH gt 6
? 2 m lt 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
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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
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Application of the method to landfill sites
Cd2, site A
Tons / year / kg waste
Cd2, site B
Tons / year / kg waste
Time (years)
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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.

Safety and Environmental Technology Group
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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)
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BACK-UP SLIDES
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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
50
Soil at site A
High per-meability at some spots
Distance to groundwater gt 2 m
pH gt 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
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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