Fate of Heavy Metals in an Abandoned Lead-Zinc Tailings Pond: II. Sediment
- Roy C. Sidle *,
- Jeanne C. Chambers and
- Michael C. Amacher
Distribution of Cu, Zn, Cd, and Pb in sediments within a 14-ha-abandoned, Pb-Zn tailings pond in north central New Mexico was investigated. Tailings were higher in heavy metals and fines in the south portion of the pond largely related to depositional patterns. Metals concentrations in surface deposits (above tailings) decreased across the pond from east to west, probably due to fluvial processes, surface disturbance by offroad vehicles, and surface erosion deposits. The two wet meadow soil/vegetation types at the south end of the pond had higher levels of heavy metals in surface soil and subsoil than the more xeric soil/vegetation types in the mid- to upper (north) portions of the pond. Ratios of total Cu, Zn, Cd, and Pb concentrations in surface soils to underlying and surface tailings, and ratios comparing the south and north portions of the pond, indicate that the relative order of mobility is Cd > Zn > Cu > Pb. Although chemical processes are partly controlling the distribution of metals within the pond, fluvial processes are at least as important. The amount and distribution of extractable metals in surface deposits overlying tailings can be used to determine topsoiling requirements for revegetation of the south end of the pond. The distribution of total metals in the upper 1.5 m of the pond suggests that surface water should be routed around the east side of the pond to prevent erosion of contaminated deposits and pollution of groundwater.
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