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IDENTIFYING DISCHARGE ZONES OF ARSENIC IN THE GOOSE RIVER BASIN, MAINE
Citation:
Sidle*, W C. IDENTIFYING DISCHARGE ZONES OF ARSENIC IN THE GOOSE RIVER BASIN, MAINE. Warwick, J.J. (ed.), JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION. American Water Resources Association, Middleburg, VA, 39(5):1-11, (2003).
Description:
Groundwater discharge areas are simulated from water balance modeling and kriging of oxygen isotopes in groundwater within the Goose River basin. Groundwater fluxes of discharge range from -10 cm yr-1 to < -25 cm yr-1 and are associated with areas of elevated arsenic in wells. Delineation of the discharge zones is broad for the water balance model employing a transient-state storage-discharge function in the fractured migmatitic phreatic aquifer. These model discharge zones may indicate potential arsenic release areas into the groundwater. Refinement of the simulated hydraulic discharge areas is best delineated by 18OH2O. Arsenic anomalies are associated with 18O values ranging from -11.5 o/oo to -9.5 o/oo Vienna Standard Mean Ocean Water (VSMOW). This naturally-occurring isotope tracer provides evidence of deeper groundwater flowing into specific fracture zones aligned northeastward across the basin. Transit times of these discharges from source regions are presently unknown from this research. However, estimates of the modeled mean residence times of shallow groundwater - surface water interactions near riparian zones suggest the turnover of flows in the uppermost phreatic aquifer to be about 8 months in the upper basin and about 20 months in the lower parts of the basin.