TRACE-METAL GEOCHEMISTRY IN DRAINAGE FROM DAVIS PYRITE MINE, ROWE MA

Davis Pyrite Mine in Rowe, Massachusetts collapsed in 1910 after 28 years of operation. Since that time, acidic drainage has been transporting iron and other trace metals into a local stream and into groundwater. The streambed is coated with variegated red, ochre, and yellow iron precipitates that also suggest the

	SC ms	pH	Fe mg/l	Mn mg/l	Zn mg/l	Cu mg/l	Al mg/l
Average Mine Creek (n=34)	284	3.10	22.45	0.83	4.51	0.80	3.10
Average Groundwater (n=158)	340	3.30	22.94	1.24	6.75	1.34	5.29

existence of a complex microbial community. Preliminary evidence indicates that the geochemistry of the environment has remained stable for decades. Metal concentrations increase in the stream as it traverses the mine tailings piles. Shallow groundwater shows similar increases, even greater in magnitude, suggesting that slower groundwater flow permits enhanced dissolution of sulfides in the tailings. Concentrations during the spring are commonly higher than during other seasons, but different patterns occur in several wells. Lead concentrations in the water are generally below detection limits (20 mg/l). Dissolved Fe precipitates as Fe-oxyhydroxide (mostly goethite), but dissolved Zn and Cu are adsorbed primarily as exchangeable ions rather than as co-precipitates. Variability in dissolved Zn/Cu ratios in groundwater throughout the site indicate that microbially induced reduction of sulfate and Fe(III) is occurring locally. Concentrations of trace elements decrease rapidly downstream in the brook that receives the mine discharge, although levels remain higher than background 500m downstream from the confluence with the discharge. The extent and mechanisms of natural remediation are being investigated as the centerpiece of current research at the site.