| Remnants of extensive mining operations in the Highlands Province have undergone natural attenuation for the past century or more but still pose an environmental threat to this critical watershed in some cases. The Highlands watershed supplies water to over 15 million people in the 4-state area (Pennsylvania to Connecticut). This study shows the degree and extent of metal contamination from two worst-case scenarios, the Phillips sulfide mine and the Sterling Lake magnetite mines.;Acid mine drainage (AMD) at Phillips Mine was identified as the point source of metal contamination with a pH < 3, (minimum pH 1.78). Metal contamination upstream exceeded local water standards: Al by 1.7, Fe 2.3, Cu 1.2, Co 2.0 and Ni 1.2 orders of magnitude. Efflorescent salts temporarily immobilized Fe2+, SO42-, metals and acidity during dry periods. During wet season, the melanterite salts dissolved completely and acidity remained at pH < 3 at the point source. Sharp declines in Fe, Co, Cu, Ni and Zn occurred at pH 2.58 and 2.71 and at 3.07 and 4.06 with sediments showing an increase in these metals downstream.;Phillips Mine soils contained trace metals, pH < 4 and organic matter (OM) < 2.5%. Mn-oxides are the major sinks for Co, Cr and Ni (r = 0.72, r = 0.89, r = 0.80, respectively), and Fe-oxides for Cu and Pb (r = 0.76, r = 0.83, respectively). Copper was determined as the major contaminant. Metal reduction is occurring through suspension of fines and dissolution in AMD, leaving behind substantial contaminants << 0.5km from the source, suggesting contamination is localized.;Sterling mine soils with pHCaCl2 3.65--5.91 contain two soil types: disturbed metal-rich soils and undisturbed OM-rich soils. Cr and Ni were the main contaminants. OM retained Cr closer to the surface (r = 0.96). With increasing depth, sesquioxides (Fe2O3 = r = 0.74; Al2O3 = r = 0.92) sorbed Cr. Ni-Cr (r = 0.98) and V-Cr (r = 0.78) correlations suggest similar retention mechanisms for these elements. Metals in water were below regulated levels, suggesting soils are acting like a natural filtering system. Slag and ash (Cr = 100 and 200 mg/kg, respectively) mixed into the soils enhanced metal contamination that otherwise were within background levels. |
