Effect of enhanced manganese oxidation in the hyporheic zone on basin‐scale geochemical mass balance

Abstract

Abstract. We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheicflow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/As, of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/X h '-2.6 hours), and in laboratory batch experiments using streambed sediment (1/X = 2.

Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ

“…The 5-to 7-km perennial reach of Pinal Creek relevant to this study is a sand-and gravel-bed stream with an average slope of 1%, an average width of 2.3 m, and an average depth of 15 cm. Pools are almost nonexistent and riffles or cascades are fairly unusual (Harvey and Fuller, 1998). Perennial flow begins about 5-to 7 km upstream of Inspiration Dam ( Fig.…”

“…At least three studies have investigated the processes responsible for Mn oxide formation in the hyporheic zone of Pinal Creek. Harvey and Fuller (1998) studied Mn(II) oxidation by hyporheic zone sediments in batch experiments using natural and artificial stream water (pH 7, $0.7 mM Mn 2+ ) in the presence and absence of microbial poisons (NaN 3 , tetracycline, and penicillin). They found that Mn(II) oxidation was strongly enhanced in the presence of microbial activity.…”

A physicochemical model for colloid exchange between a stream and a sand streambed with bed forms

“…A comparison of transient storage model parameters (obtained from a tracer injection) and observed subsurface flows indicated that the model does not always adequately represent actual stream-subsurface exchange [Harvey et al, 1996]. While existing models employ a single exchange coefficient, in reality, exchange is driven by multiple processes that operate at several spatial scales [Harvey and Bencala, 1993;Harvey and Fuller, 1998;Wroblicky et al, 1998]. Prediction of hyporheic exchange will require improved understanding of the processes that drive transport across the stream-subsurface interface.…”

Transient storage and hyporheic flow along the Willamette River, Oregon: Field measurements and model estimates

“…It provides conditions within streams for heterotrophic primary production [Mulholland et ] to locations far from the stream channel [Stanford and Ward, 1993], hyporheic flow provides habitat for aquatic macroinvertebrates. Hyporheic flow changes surface water quality characteristics through physical and biogeochemical processes: physical mixing with groundwater [Constantz, 1998], chemical reactions Harvey and Fuller, 1998], microbially mediated chemical transformations [Duff and Triska, 1990;McMahon and Bohlke, 1996], and transport of nutrients to streams through groundwater-surface water interactions [Wondzell and Swanson, 1996;Valett et al, 1997].…”