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Abstract: Seasonal and spatial variations in metal concentrations and pH were found in a stream at a restored copper mine site located near a massive sulfide deposit in the Foothill copper-zinc belt of the Sierra Nevada, California. At the mouth of the stream, copper concentrations increased and pH decreased with increased streamflow after the onset of winter rain and, unexpectedly, reached extreme values 1 or 2months after peaks in the seasonal hydrographs. In contrast, aqueous zinc and sulfate concentrations were highest during low-flow periods. Spatial variation was assessed in 400m of reach encompassing an acidic, metal-laden seep. At this seep, pH remained low (2−3) throughout the year, and copper concentrations were highest. In contrast, the zinc concentrations increased with downstream distance. These spatial patterns were caused by immobilization of copper by hydrous ferric oxides in benthic sediments, coupled with increasing downstream supply of zinc from groundwater seepage. [Copyright &y& Elsevier]

Abstract: Soil and plants were sampled throughout winter and spring near a perennial stream traversing a restored mine site in a winter–rainy climate. Within 1m of an acidic reach of the stream, soil had pH 3–5 and 50–100μg/g “bioavailable” copper (extractable with 0.01M CaCl2). Soil 2–3m from the stream had pH 5–8 and lower (less than 3μg/g) bioavailable copper. “Oxide-bound” copper (extractable with 2N HCl) was 50–100μg/g at most locations. Copper concentrations in the shoots of field-collected Bromus carinatus declined from 20μg/g in winter to 2μg/g in spring at all sampling sites. A similar temporal pattern was found in plants grown under controlled conditions. Thus B. carinatus has a developmental program for control of shoot copper concentration, causing a seasonally-varying pattern of copper phytoaccumulation over a large range of copper availability in the soil. [Copyright &y& Elsevier]