A NALYSIS AND SIMULATION OF REACTIVE TRANSPORT OF METAL CONTAMINANTS IN GROUND WATER IN THE P INAL C REEK B ASIN, A RIZONA Dan Portlock Environmental Engineering NDSU Geol 628 Geochemistry 12/1/10

Introduction Background information on Pinal Creek mining Background information on Advection and Transport Modeling Advection and Transport Modeling using Phreeqc Compare current and present modeling Conclusion

I NTRODUCTION Large scale mining activities generated a plume of acidic ground water more than 15 km long in the aquifer of the Pinal Creek Basin In 1984, the acidic part of the plume had a pH as low as 3.4 and contained milligram-per- liter concentrations of iron, copper, aluminum and other metals. Contaminant sources include mine tailings, heap-leach areas, surface impoundments of water associated with mining processes and occasional spills of contaminated water into streambeds.

P INAL C REEK W ELLS

P INAL C REEK F LOW D IAGRAM

P INAL C REEK W ELLS ConstituentWells PCID Sample date pH Calcium Magnesium Sodium Potassium Alkalinity —————— TIC — ——— Sulfate Chloride Fluoride Silica — Iron Manganese < Aluminum < — Cadmium < Copper < Cobalt < < < 0.003— Nickel < < 0.008— Strontium — Zinc < < Table 1 Measured water chemistry of wells along simulated flow path, Pinal Creek Basin, 1984–1990 Values are in mmol/l except for pH. Dashes indicate no data; PCID, Pinal Creek at Inspiration Dam; TIC, total inorganic carbon.

A DVECTION (

A DVECTION M ODEL Number of cells or sample points Solutions that needs to be output

T RANSPORT ( ADVECTION AND DISPERSION ) Distance between sample points Dispersivity between sample points Number of shifts (pore volumes) Time step Boundary conditions Direction of flow

A DVECTION ( ONE PORE VOLUME )

T RANSPORT (O NE P ORE V OLUME )

T WO P ORE V OLUMES

T HREE P ORE V OLUMES

T RANSPORT AND A DVECTION P H

C OMPARED M ODELING R ESULTS

C ONCLUSIONS The advection model is a quick and simple method for analyzing the transport of metals or other contaminants in a system -It does not account for the distance traveled or the reaction that occurs which could lead to problems when analyzing a more complex system. The transport model includes dispersion and reaction time which will provide a more detailed analysis of a system. -The parameters in the transport model are sometimes hard to estimate which could lead to errors.

R EFERENCES Brown, James., Analysis and simulation of reactive transport of metal contaminants in ground water in Pinal Creek Basin, Arizona Journal of Hydrology 209, Brown, J.G., Eychaner, J.H., Research of acidic contamination of ground water and surface water, Pinal Creek Basin, Arizona. In: J.G. Brown and B.O. Favor, (Editors), Hydrology and geochemistry of aquifer and stream contamination related to acidic water in Pinal Creek Basin near Globe, Arizona. US Geological Survey Water-Supply Paper 2466, pp. 1–20.

Q UESTIONS Thank you