# Presentation: 209196

## Metals Modeling

- Summary of Process Equations and Model Input Data

## Summary of Significant Heavy Metal Reactions

| Metal | As | Ba | Cd | Cu | Hg | Pb | Se | Zn |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Anion Exchange |  |  |  |  |  |  |  |  |
| Sorption Potential |  |  |  |  |  |  |  |  |
| Acid-Base Hydrolysis |  |  |  |  |  |  |  |  |
| Complexation: 
     with Inorganic Ligands |  |  |  |  |  |  |  |  |
|      with Organic Ligands |  |  |  |  |  |  |  |  |
| Oxidation, Reduction (kinetic) |  |  |  |  |  |  |  |  |
| Methylation (kinetic) |  |  |  |  |  |  |  |  |

- From Schnoor, et al., 1987.

## Speciation of Metals in Aquatic Environment

## Metals Adsorption

- An “adsorption reaction” is a reaction between a solute ion and a functional group (site) on a solid surface.
- Important in attenuating dissolved metal concentration.
- Use MINTEQA2 with adsorption reactions to calculate the distribution coefficient between adsorbed and dissolved phases.

- From Allison and Allison, 2004. MINTEQ course notes.

## Adsorption in MINTEQA2

- Are analogous to coordination reactions in solution.
- Obey mass laws (mass action)
- Include both physical and chemical solute-surface interactions (van der Waals forces, electrostatic attraction, valency forces).
- Can be written as chemical “reactions” regardless of the mechanism.
- Are thermodynamically distinct from solution reactions only when an electrostatic term is computed and applied separately.

***In MINTEQA2, adsorption reactions:***

- From Allison and Allison, 2004. MINTEQ course notes.

## Adsorption Options in MINTEQA2

- Linear Partitioning model
- Freundlich Isotherm
- Langmuir Isotherm
- Surface Complexation models:
- Diffuse layer (i.e., MIT Two-Layer model)
- Constant Capacitance
- Triple Layer
- Ion Exchange model

- From Allison and Allison, 2004. MINTEQ course notes.

## Linear, Freundlich, and Langmuir Equations for: 

- Linear Partitioning:
- Activity Kd Model
- Freundlich Isotherm:
- Activity Freundlich Model
- Langmuir Isotherm:

- From Allison and Allison, 2004. MINTEQ course notes.

## Sorption Model Comparison

- Comparison of Linear, Freundlich, & Langmuir Isotherms
- (after Stumm and Morgan, 1996; Morel, 1983)

- From Allison and Allison, 2004. MINTEQ course notes.

## Lumped Metals Partition Equation

- Cd, mg/L

- Cs, mg/L

- M, kg/L

## WASP Non-Reactive Metals Processes

- From Caruso, 2005. CREM presentation

## Selection of TOXI Module for Simulating Metals

- Non-Reactive Metals: Simple Toxicant Module
- Ag, Ba, Be, Cd, Co, Cu, Mo, Ni, Pb, Sb, Tl, V, Zn
- As, Cr, Se, Sn (if redox kinetics data unavailable)
- Reactive Metals: Non-Ionizing Toxicant Module
- As, Cr, Se, Sn (if redox kinetics data available)
- Mercury: Mercury Module

## Metals Data SpecificationSimple Toxicant Module

- Constants
- Log 10 partition coefficient to DOC, log (L/kg)
- Partition coefficient to silts and fines, L/kg
- Partition coefficient to sands, L/kg
- Partition coefficient to organic solids, L/kg
- Parameters
- Dissolved organic carbon, mg/L
- Partition coefficient to silts and fines, L/kg
- Partition coefficient to sands, L/kg
- Partition coefficient to organic solids, L/kg
- (KD values for constants, if any, take precedence over parameters)

## Metals Data SpecificationNon-Ionizing Toxicant Module

- Constants
- Log 10 partition coefficients to DOC, log (L/kg)
- Partition coefficients (to silts and fines, to sands, and to organic solids), L/kg
- Oxidation rate constants (diss, sorb, DOC), M-1day-1 (or 1.0)
- Oxidation mass yield coefficient (g/g)
- Reduction rate constants (diss, sorb, DOC), M-1day-1 (or 1.0)
- Reduction mass yield coefficient (g/g)
- Parameters
- Dissolved organic carbon, mg/L
- Oxidant concentration, M, (or rate constant, day-1)
- Reductant concentration, M, (or rate constant, day-1)

## Partition Coefficients by Media

| Metal | Soil* | Suspended Matter* | Sediment* | DOC* |
| --- | --- | --- | --- | --- |
| Ag(I) | 1.0 / 2.6 / 4.5 | 4.4 / 4.9 / 6.3 | 2.1 / 3.6 / 5.8 |  |
| As(III,V) | 0.3 / 3.4 / 4.3 | 2.0 / 4.0 / 6.0 | 1.6 / 2.5 / 4.3 |  |
| Ba(II) | 0.7 / - / 3.4 | 2.9 / 4.0 / 4.5 |  |  |
| Be(II) | 1.7 / 3.1 / 4.1 | 2.8 / 4.1 / 6.8 |  |  |
| Cd(II) | 0.1 / 2.9 / 5.0 | 2.8 / 4.7 / 6.3 | 0.5 / 3.6 / 7.3 | 3.4 / 5.2 / 5.5 |
| Co(II) | -1.2 / 2.1 / 4.1 | 3.2 / 4.7 / 6.3 | 2.9 / 3.3 / 3.6 | 2.9 / 4.5 / 4.8 |

- (log KD in L/kg)

- * Low / **Median** / High

- From Allison and Allison, 2005

## Partition Coefficients by Media

| Metal | Soil* | Suspended Matter* | Sediment* | DOC* |
| --- | --- | --- | --- | --- |
| Cr (III) | 1.0 / 3.9 / 4.7 | 3.9 / 5.1 / 6.0 | - / 4.5 / - |  |
| Cr (VI) | -0.7 / 1.1 / 3.3 |  |  |  |
| Cu(II) | 0.1 / 2.7 / 3.6  | 3.1 / 4.7 / 6.1 | 0.7 / 4.2 / 6.2 | 2.5 / 5.5 / 7.0 |
| Hg(II) | 2.2 / 3.8 / 5.8 | 4.2 / 5.3 / 6.9 | 3.8 / 4.9 / 6.0 | 5.3 / 5.3 / 5.6 |
| CH3Hg+ | 1.3 / 2.8 / 4.8 | 4.2 / 5.4 / 6.2 | 2.8 / 3.6 / 5.0 |  |
| Mo(VI) | -0.2 / 1.1 / 2.7 |  | - / 2.5 / - |  |

- * Low / **Median** / High

- (log KD in L/kg)

- From Allison and Allison, 2005

## Partition Coefficients by Media

| Metal | Soil* | Suspended Matter* | Sediment* | DOC* |
| --- | --- | --- | --- | --- |
| Ni(II) | 1.0 / 3.1 / 3.8 | 3.5 / 4.6 / 5.7 | - / 4.0 / - | 4.7 / 5.1 / 5.4 |
| Pb(II) | 0.7 / 4.2 / 5.0 | 3.4 / 5.6 / 6.5 | 2.0 / 5.1 / 7.0 | 3.8 / 5.0 / 5.6 |
| Sb(III,V) | 0.1 / 2.4 / 2.7 |  | 2.5 / 4.0 / 4.8 | 2.7 / - / 4.3 |
| Se(VI) | -0.3 / 1.0 / 2.4 | 3.1 / - / 4.7 | - / 3.6 / - |  |
| Sn(II) | 2.1 / 2.9 / 4.0 | 4.9 / 5.6 / 6.3 | - / 4.7 / - |  |
| Tl(I) |  |  | 3.0 / 3.2 / 3.5 |  |

- * Low / **Median** / High

- (log KD in L/kg)

- From Allison and Allison, 2005

## Partition Coefficients by Media

| Metal | Soil* | Suspended Matter* | Sediment* | DOC* |
| --- | --- | --- | --- | --- |
| V(V) | 1.1 / - / 2.7 |  |  |  |
| Zn(II) | -1.0 / 3.1 / 5.0 | 3.5 / 5.1 / 6.9 | 1.5 / 3.7 / 6.2 | 4.6 / 4.9 / 6.4 |
| CN- | 0.7 / 3.0 / 3.6 |  |  |  |

- * Low / **Median** / High

- (log KD in L/kg)

- From Allison and Allison, 2005

## References

- Allison, J.D., and Allison, T.L. 2004., MINTEQA2 Geochemial Speciation Workshop.  Allison Geoscience Consultants, Inc., Buford, GA.
- Allison, J.D., and Allison, T.L., 2005. Partition Coefficients for Metals in Surface Water, Soil, and Waste.  U.S. EPA, Athens, GA.  EPA/600/R-05-074.
- Caruso, B. S., 2005.  Modeling Metals Fate and Transport in the Upper Tenmile Creek Watershed Mining Area, Montana.  CREM Presentation.
- Felmy, A. et al., 1985.  MINTEQ – A Computer Program for Calculating Aqueous Geochemical Equilibria. U.S. EPA, Athens, GA.  EPA/600/3-84-032.
- Schnoor, J.L., et al., 1987. Processes, Coefficients, and Models for Simulating Toxic Organics and Heavy Metals in Surface Waters. U.S. EPA, Athens, GA.  EPA/600/3-87-015.