Evaluation of - PowerPoint Presentation

Slide1

Evaluation of a multisurface complexation reactive transport model on field data.

Bert-Jan Groenenberg1, Joris Dijkstra2, Rob Comans2,3

1

Alterra

Wageningen UR;

2

ECN;

3

Wageningen UniversitySlide2

IntroductionUse

of reactive transport models in risk assessment of transport of metals to ground- and surface waters:Site applicationsGeneric risk assessment e.g. derivation of maximum leaching of metals from building materials to groundwater in the Netherlands#Need for validation

#

Verschoor et al. 2008,

9th

International Symposium on

EnvironmentalGeotechnology

and Global Sustainable

Development,

Hong

KongSlide3

Outline

Outline of the modelDescription of the field siteEvaluation of the geochemical modelEvaluation of the reactive transport model by hindcast simulation of measured profilesSlide4

Process based Multisurface model

Multisurface models describe the various processes by combining separate models for the distinguished reactive surfaces (SOM, Al/Fe-oxides, clay, …)

Intrinsic model parameters derived from lab experiments on purified or synthetic model systems (Humic Acid, HFO, Goethite…)Slide5

Models: (2) Multisurface Model

1)

Meeussen., ES&T 2003Slide6

Multisurface Model (1)

Models in Framework ORCHESTRABinding to SOM and DOM: NICA-Donnan*Binding to clay: Donnan modelBinding hydrous oxides of Fe and Al: GTML Mineral equilibria and inorganic ion pair formation MINTEQ database

*)

Kinniburgh et al. ,Colloids Surf. 1999Slide7

Multisurface Model (2)

Models in Framework ORCHESTRABinding to SOM and DOM: NICA-DonnanBinding to clay: Donnan modelBinding hydrous oxides of Fe and Al: GTML Mineral equilibria and inorganic ion pair formation MINTEQ databaseSlide8

Multisurface Model (3)

Models in Framework ORCHESTRABinding to SOM and DOM: NICA-DonnanBinding to clay: Donnan modelBinding hydrous oxides of Fe and Al: GTLM *

Mineral equilibria and inorganic ion pair formation MINTEQ database

*)

Dzombak and Morel, 1990Slide9

Multisurface Model (4)

Models in Framework ORCHESTRABinding to SOM and DOM: NICA-DonnanBinding to clay: Donnan modelBinding hydrous oxides of Fe and Al: GTML Mineral equilibria and inorganic ion pair formation MINTEQ database *

*

Allison et al., US-EPA 1991Slide10

Transport Model

Soil column 0-150 cmDiscretisized in layers of 10 cm thicknessContinuous flowEvery timestep:TransportEquilibration between solution and solid phase (chemical model)Slide11

Field site

Waste water infiltration field 1930- 1970/1980 Used to clean sewage water from the city Tilburg before disposal to surface water

Contaminated with Cr and other metals. Cr from leather tanning industry

Used for cattle (1930-2000)

2000 plantation of forestSlide12

MeasurementsProfile 0-150 cm

Soil solid phase:Metal contents total (AR) and reactive (0.43 M HNO3)Soil organic matter: total and HA, FAAl and Fe (hydr)-oxides oxalate, dithionite and ascorbic acidClay contentSolution: 0.002 M CaCl2 extracts and centrifugation:pH, macro ions (Al, Fe, Ca, P, S,....)DOC and FA and HA thereinmetalsSlide13

Evaluation geochemical modelPrediction of total solution concentrations from:

Total reactive metal in soil (0.43 M HNO3)SOMAl/Fe-(hydr)oxidesClay contentpHDOC / FA and HASlide14

Evaluation geochemical modelSlide15

Evaluation geochemical modelSlide16

Evaluation geochemical modelSlide17

Hindcast simulation

Start in 1930 (start use as infiltration fields) background levels estimated Loading with metals 1930-1980: total load = reactive metal in profile – background 19301980-2000 use as pastry pH maintained at 62000 plantation of forest (pH decreases)2003 experimental acidification field plot2009 measurement soil profileSlide18

Hindcast simulation

Period 1Period 2Period 3acidified

time

50 years

20 years

10/ 3 years

7 years

Precipitation excess

2700 mm/y

300 mm/y

300 mm/y

300 mm/y

DOC

150-20 mg/L

150-20 mg/L

150-20 mg/L

150-20 mg/L

pH

6

6

5

4Slide19

Hindcast simulationSlide20

Hindcast simulationSlide21

Hindcast simulationSlide22

Hindcast simulationSlide23

SensitivitySlide24

Conclusions / further research

Geochemical model predicts solution concentrations satisfactorily except for PbModel is able to “predict” present concentration profiles for most cationic metalsSolubilization by acidification is reproduced well by the modelSlide25

Conclusions / further research

Sensitivity analysis shows that DOC is a critical input parameterPb needs further attentionColloidal transport / agingEvaluation can be improved for better defined systems (known inputs, water fluxes etc.)Slide26

Thank you for your attention!© Wageningen UR