ANALYSIS AND SIMULATION OF REACTIVE TRANSPORT OF METAL CONTAMINANTS IN GROUND WATER IN THE PINAL CREEK BASIN, ARIZONA

Dan PortlockEnvironmental Engineering

NDSU Geol 628 Geochemistry12/1/10

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

INTRODUCTION 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.

PINAL CREEK WELLS

PINAL CREEK FLOW DIAGRAM

PINAL CREEK WELLSConstituent Wells  

  51 101 202 302 402 451 503 702 PCID

Sample date

11-84 11-84 3-85 11-84 11-84 3-89 7-86 5-90 1-93

pH 3.62 3.64 9.19 3.54 4.10 4.94 6.15 7.00 7.7

Calcium 12.2 11.5 1.2 16.7 13.0 14.7 15.2 13.8 1.4

Magnesium 16.0 12.3 0.37 11.9 5.76 5.47 5.76 5.06 0.31

Sodium 10.0 8.26 0.96 6.96 3.48 3.59 3.39 3.03 0.33

Potassium 0.24 0.25 0.036 0.21 0.19 0.28 0.11 0.16 0.087

Alkalinity — — — — — — 2.05 3.52 0.93

TIC 4.00 4.42 — 4.91 4.08 4.67 — — —

Sulfate 104 73.9 0.7 71.8 27.1 24.8 20.8 18.22 1.46

Chloride 11.0 10.4 0.48 8.74 3.95 5.13 3.66 2.34 0.107

Fluoride 2.1 1.4 0.002 1.4 0.35 0.53 0.021 0.013 0.02

Silica 1.66 1.65 0.36 1.83 1.45 1.14 1.01 0.458 —

Iron 57.3 39.4 0.00073 32.2 6.27 2.47 0.0032 0.019 0.00013

Manganese 1.33 1.04 < 0.00056 1.09 0.91 1.89 0.819 0.052 0.00098

Aluminum 11.1 8.54 < 0.003 6.69 0.409 0.153 0.0007 0.186 —

Cadmium 0.0035 0.0018 < 0.00045 0.002 0.0004 0.0001 0.00004 0.00003 0.000009

Copper 2.36 1.89 0.00016 1.53 0.30 0.177 0.0005 < 0.002 0.00047

Cobalt 0.18 0.14 < 0.00034 0.12 0.030 0.031 < 0.00020 < 0.003 —

Nickel 0.065 0.054 < 0.0085 0.051 0.019 0.020 0.007 < 0.008 —

Strontium 0.017 0.018 0.0023 0.034 0.020 0.018 0.240 0.027 —

Zinc 0.29 0.18 < 0.00023 0.14 0.046 0.53 0.0029 0.002 < 0.00005

Table 1Measured water chemistry of wells along simulated flow path, Pinal Creek Basin, 1984–1990Values are in mmol/l except for pH. Dashes indicate no data; PCID, Pinal Creek at Inspiration Dam; TIC, total inorganic carbon.

ADVECTION

(http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc)

ADVECTION MODEL

Number of cells or sample points

Solutions that needs to be output

TRANSPORT (ADVECTION AND DISPERSION)

Distance between sample points

Dispersivity between sample points

Number of shifts (pore volumes)

Time step Boundary conditions Direction of flow

ADVECTION (ONE PORE VOLUME)

TRANSPORT (ONE PORE VOLUME)

TWO PORE VOLUMES

THREE PORE VOLUMES

TRANSPORT AND ADVECTION PH

COMPARED MODELING RESULTS

CONCLUSIONS 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.

REFERENCES Brown, James., Analysis and simulation of reactive

transport of metal contaminants in ground water in Pinal Creek Basin, Arizona 1997. Journal of Hydrology 209, 225-250.

Brown, J.G., Eychaner, J.H., 1996. 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.

QUESTIONS

Thank you