1999 Progress Report: Application of Sediment Quality Criteria for Metals to a Montane Lotic Ecosystem: Field Validation During Reclamation of a Copper Mine Causing Acid Mine DrainageEPA Grant Number: R826199
Title: Application of Sediment Quality Criteria for Metals to a Montane Lotic Ecosystem: Field Validation During Reclamation of a Copper Mine Causing Acid Mine Drainage
Investigators: Meyer, Joseph S. , Lockwood, Jeffrey A. , Rockwell, Richard W.
Institution: University of Wyoming
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 1998 through March 31, 2001 (Extended to September 30, 2002)
Project Period Covered by this Report: April 1, 1998 through March 31, 1999
Project Amount: $449,558
RFA: Contaminated Sediments (1997) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Hazardous Waste/Remediation , Land and Waste Management
We are testing whether a method for deriving sediment quality guidelines (SQG) for metals, which was proposed recently by the U.S. Environmental Protection Agency and developed primarily in lowland rivers, lakes, and estuaries, can be applied to the relatively dynamic and heterogeneous hydrological and biogeochemical conditions typical of high-elevation Rocky Mountain streams receiving acid mine drainage.
Our study stream is Haggarty Creek, which originates at the Continental Divide in Carbon County, Wyoming. During three seasons (spring-July, summer-August-September, and fall-October) in 1998, we sampled four stations, including a noncontaminated reference station on Bachelor Creek, and three metal-contaminated stations on Haggarty Creek at increasing distances downstream from its confluence with copper-laden effluent from the Rudefeha Mine. Concentrations of acid volatile sulfide (AVS), simultaneously-extracted metals (SEM), and organic carbon (OC) in sediments, and concentrations of dissolved metals and OC in interstitial (pore), sediment-water interface, and column waters at each station were compared with results from 7-day, in situ sediment and water toxicity tests and measurements of metals in benthic macroinvertebrates at the same stations. Sediment and water toxicity tests separately incorporated three invertebrate species (Chironomus tentans, Hyalella azteca, and Hesperoperla pacifica) at each station. For each species, we also conducted laboratory toxicity tests to determine LC50s for each of the five metals (Cd, Cu, Ni, Pb, and Zn) measured in this study.
AVS was not detected in sediments collected from any station in the spring (July), was only detected in sediments from our reference station in the summer (0.01 µmol/g dw), and was measured at slightly higher concentrations in sediments from our reference and our most effluent-distal stations in the fall (0.5 and 1.8 µmol/g dw, respectively), demonstrating an anticipated paucity of AVS in the montane, lotic ecosystem. Concentrations of sediment OC (10-90 mg/g dw) generally suggest an expected trend of seasonal increase related to deposition of allochthonous detritus. Dissolved OC (DOC) concentrations in samples of interstitial (0.25-6.50 mg/L), interface (0.25-2.75 mg/L), and column (0.10-2.00 mg/L) waters suggest seasonal decreases in DOC from spring to fall, and general DOC increases with distance downstream from the mine.
Copper was the only metal contaminant measured at toxicologically-relevant concentrations in Haggarty Creek. Sediment concentrations (0.2-2.1 mg Cu/g dw) decreased with distance from the mine, but no significant seasonal trends were observed within stations. However, dissolved concentrations (10-380 µg Cu/L) from all three water compartments demonstrated spatial and seasonal trends in which aqueous Cu decreased with distance from the mine, and decreased within stations throughout the year. Simultaneously-extracted Cu was always present in excess of the AVS at all study sites, with the excess usually >1 µmoL/g dw at the contaminated sites, but always <0.5 mmol/g dw at the reference site. However, considerable in situ toxicity was only observed at the site closest to the mine effluent, where high aqueous concentrations of Cu appeared also to contribute to the observed toxicity. Copper accumulation in survivors of the in situ toxicity tests also decreased with distance from the mine, as did Cu accumulation in native benthos. Thus, toxicity of sediment Cu at the more downstream sites might have been ameliorated by the presence of OC in the sediments or determined primarily by aqueous Cu.
For several reasons, deployment of in situ toxicity chambers was challenging. First, despite multiple attempts to improve our protocol for the acclimation of laboratory invertebrates to physico-chemical conditions (low water temperature, alkalinity, and hardness) in the field, 100 percent of the H. azteca died in all in situ chambers at all stations, including our reference station, during all seasonal bouts. Second, chamber placement relative to silt deposits and streamflow was critical for in situ toxicity tests. Third, seasonal differences in Haggarty Creek's flow regime varied the locations of and our access to deposition zones for deployment of sediment toxicity chambers.
During 1999 (Year 2), we will attempt to use the native flatworm Polycelis coronata as a metals-sensitive species replacing H. azteca, and we will condense the field season to improve the consistency of placement of the in situ chambers. In Year 3, full-scale remediation of the Rudefeha Mine will allow us to compare results prior to and during mine reclamation.