Persistent Impacts of Trace Metals from Mining on Floodplain Grass Communities Along Soda Butte Creek, Yellowstone National Park.
ABSTRACT / In Yellowstone National Park, tailings and associated trace metals from past mining have been deposited along 28 km of Soda Butte Creek by large flood events. This study documents grass species diversity, density, and biomass; trace metal concentrations in soils; and soil pH, salinity, and clay content in four selected floodplain meadows contaminated by these tailings. Trace metal levels frequently exceed acceptable concentrations for agricultural soils at sampling points within the meadows. pH levels within flood-deposited tailings are strongly to moderately acid, while pH levels outside of tailings deposits are neutral. The data analysis: (1) shows that metals and acidity associated with tailings affect plant biomass, density, and diversity; (2) documents that the vegetation/metal and vegetation/pH associations are more of a threshold than a linear relationship; and (3) suggests that other factors may be involved in structuring the community. Vegetation diversity, density, and biomass decrease at threshold levels of trace metal concentrations and soil pH in all four meadows. CuSum plots of diversity in relation to trace metal levels show a decrease in mean diversity at 315 ppm copper, 22 ppm arsenic, 4.2% iron, 65 ppm lead, and 170 ppm zinc. Densities of Phleum pratense and Poa pratensis were significantly lower (P </= 0.001) on plots with more than 250 ppm copper. Above-ground biomass of Phleum pratense was also significantly lower on plots with copper levels above 250 ppm. Decreased mean grass density was found on plots with pH < 6.4, but the only statistically significant difference was for Juncus balticus, which had increased density on plots with pH < 6.4. In contrast to the clear impacts of trace metals and pH on vegetation, other site characteristics did not alter measured vegetation characteristics.
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ABSTRACT: Many reservoirs currently in operation trap most or all of the sediment entering the reservoir, creating sediment-depleted conditions downstream. This may cause channel adjustment in the form of bank erosion, bed erosion, substrate coarsening, and channel planform change. Channel adjustment may also result from episodic sediment releases during reservoir operation, or from sediment evacuation following dam removal. Channel adjustment to increased sediment influx depends on the magnitude, frequency, duration and grain-size distribution of the sediment releases, and on the downstream channel characteristics. Channel adjustment may occur as a change in substrate size- distribution, filling of pools, general bed aggradation, lateral instability, change in channel planform, and/or floodplain aggradation. The increased sediment availability may alter aquatic and riparian habitat, reduce water quality, distribute adsorbed contaminants along the river corridor, and provide germination sites for exotic vegetation. Mitigation of these sedimentation hazards requires: (1) mapping grain-size distribution within the reservoir and estimating the grain-size distributions of sediment that will be mobilized through time; (2) mapping shear stress and sediment transport capacity as a function of discharge on the basis of channel units for the length of the river likely to be affected; (3) mapping potential depositional zones, and aquatic habitat and "acceptable losses," along the downstream channel, and comparing these volumes to the total sediment volume stored in the reservoir as a means of estimating total transport capacity required to mobilize reservoir sediment delivered to the channel; (4) designing discharge and sediment release regime (magnitude, frequency, duration) to minimize adverse downstream impacts; and (5) developing plans to remove, treat, contain, or track contaminants, and to restrict establishment of exotic vegetation. The North Fork Poudre River in Colorado is used to illustrate this approach to mitigating sediment hazards downstream from reservoirs.01/2003;
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ABSTRACT: Extensive anthropogenic terrestrial sedimentary deposits are well recognized in the geologic literature and are increasingly being referred to as legacy sediment (LS). Definitions of LS are reviewed and a broad but explicit definition is recommended based on episodically produced anthropogenic sediment. The phrase is being used in a variety of ways, but primarily in North America to describe post-settlement alluvium overlying older surfaces. The role of humans may be implied by current usage, but this is not always clear. The definition of LS should include alluvium and colluvium resulting to a substantial degree from a range of human-induced disturbances; e.g., vegetation clearance, logging, agriculture, mining, grazing, or urbanization. Moreover, LS should apply to sediment resulting from anthropogenic episodes on other continents and to sediment deposited by earlier episodes of human activities. Given a broad definition of LS, various types of LS deposits are described followed by a qualitative description of processes governing deposition, preservation, and recruitment. LS is deposited and preserved where sediment delivery (DS) exceeds sediment transport capacity (TC). This can be expressed as a storage potential ratio that varies within and between basins and through time. When DS/TC < 1, recruitment and transport of LS dominate, but if DS/TC > 1, deposition and preservation are likely. When DS/TC ≫ 1, abundant deposition and graded deposits are likely even without barriers or sinks. Thus, spatial patterns of LS deposits may reveal information about past land-use history and hydrodynamics in a catchment.Anthropocene. 10/2013;
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ABSTRACT: Porphyry Cu-Mo deposits have influenced surface water quality in high-Andes of north-central Chile since the Miocene. Water anomalies may reduce species abundance and diversity in alpine meadows as acidic and metal-rich waters are highly toxic to plants The study assessed the importance of surface water quality on plant abundance and diversity in high-alpine meadows at the Yerba Loca Natural Santuary (YLNS), central Chile (33°15' S, 70°18' W). Hydrochemical and plant prospecting were carried out on Piedra Carvajal, Chorrillos del Plomo and La Lata meadows the growing seasons of 2006 and 2007. Direct gradient analysis was performed through canonical correspondence analysis (CCA) to look for relationships among water chemistry and plant factors. High variability in water chemistry was found inside and among meadows, particularly for pH, sulphate, electric conductivity, hardness, and total dissolved Cu, Zn, Cd, Pb and Fe. Data on species abundance and water chemical factors suggests that pH and total dissolved Cu are very important factor determining changes in plant abundance and diversity in study meadows. For instance, Festuca purpurascens, Colobanthus quitensis, and Arenaria rivularis are abundant in habitals with Cu-rich waters while Festuca magellanica, Patosia clandestina, Plantago barbata, Werneria pygmea, and Erigeron andícola are abundant in habitals with dilute waters.Revista chilena de historia natural 12/2008; 81(4):469-488. · 0.93 Impact Factor