Agent-based simulations of Agent-based simulations of biocomplexity: Effects of biocomplexity: Effects of

adsorption to natural organic adsorption to natural organic mobility through soilsmobility through soils

Leilani Arthurs and Patricia Leilani Arthurs and Patricia MauriceMauriceCivil Engineering and Geological Civil Engineering and Geological SciencesSciences

Gregory Madey, Xiaorong Xiang, Gregory Madey, Xiaorong Xiang, Yingping Huang, and Ryan Yingping Huang, and Ryan KennedyKennedyComputer Science and Computer Science and Engineering Engineering

University of Notre DameUniversity of Notre Dame

Natural Organic Matter Natural Organic Matter (NOM)(NOM)

Ubiquitous in aqueous and terrestrial Ubiquitous in aqueous and terrestrial environmentsenvironments

Breakdown product of decaying plant Breakdown product of decaying plant materialmaterial

Controls many biogeochemical Controls many biogeochemical processesprocesses

Polydisperse mixturePolydisperse mixture Molecular weight controls NOM reactivityMolecular weight controls NOM reactivity

Figure from Cabaniss et al. (2000)

Development of NOM Development of NOM SimulatorSimulator

Complex interactions of NOM through Complex interactions of NOM through porous media results in emergent behaviors porous media results in emergent behaviors amenable to a “biocomplexity” approach.amenable to a “biocomplexity” approach.

Design and use an agent-based stochastic Design and use an agent-based stochastic model for NOM interactions.model for NOM interactions.

We focus specifically on how NOM molecular We focus specifically on how NOM molecular weight affects adsorption to mineral weight affects adsorption to mineral surfaces and mobility through soil.surfaces and mobility through soil.

Additional research by Cabaniss et al. Additional research by Cabaniss et al. focuses on higher order biogeochemical focuses on higher order biogeochemical reactions.reactions.

The NOM Simulator DesignThe NOM Simulator Design• Java language, J2EE architecture• Swarm and Repast software• WEB interface

•Can be used interactively as part of a collaboratory•Allows for data mining

• Low surface coverages: adsorbed fraction mimics initial• Higher surface coverages: preferential adsorption of

intermediate to high molecular weight components• Kinetic data show that smaller molecules adsorb fast,

gradually replaced by larger molecules

Zhou et al. (2001)

01.089.0 2000 +×=−

ePx

desorb

• High MW adsorbs slowly and desorbs slowly.

• Low MW adsorbs fast and desorbs fast.

)(MWeightMolecularWx =

Adsorption & Desorption Probabilities to Fit Batch Data

NOM Input DistributionNOM Input Distribution1. Example of WEB interface:

2. Initial Molecular Distribution:

ef M ii

σμσ

22 2/)log(21 −−×

Π=

(Equation Cabaniss et al. 2000)

• Zhou et al. showed that average MW in solution decreased over time, indicating replacement of fast adsorbing small molecules by larger molecules. • The NOM Simulator captures this behavior for batch adsorption example.

Probability equations optimized from Probability equations optimized from batch experiments applied to flow batch experiments applied to flow model (column experiment).model (column experiment).

Flow simulation will be compared to future laboratory column experiments.

Visualization of SimulationVisualization of Simulation

Settings

Legend

Visualization Capture 1Visualization Capture 1

Visualization Capture 2Visualization Capture 2

Visualization Capture 3Visualization Capture 3

Visualization Capture 4Visualization Capture 4

Results and ConclusionsResults and Conclusions Developed an agent-based stochastic Developed an agent-based stochastic

model for NOM adsorption.model for NOM adsorption. The simulator is accessible through The simulator is accessible through

the WEB.the WEB. Promotes the use of a Promotes the use of a

“collaboratory” for geographically “collaboratory” for geographically separated interdisciplinary scientists.separated interdisciplinary scientists.

Allows users to set/refine parameters Allows users to set/refine parameters and equations.and equations.

AcknowledgementsAcknowledgements

Dr. Steve Cabaniss Dr. Steve Cabaniss (University of New (University of New Mexico)Mexico)

Center for Center for Environmental Science Environmental Science and Technology and and Technology and Environmental Environmental Molecular Science Molecular Science Institute at the Institute at the University of Notre University of Notre DameDame

National Science National Science Foundation (EMSI, ITR)Foundation (EMSI, ITR)

PPG IndustriesPPG Industries