Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates
The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH.
David J. Williamsa, Jerry M. Bighama, Charles A. Cravotta IIIb, Sam J. Trainaa, John E. Andersonc and John G. Lyond
a School of Natural Resources, The Ohio State University, Columbus, OH 43210, USA
b US Geological Survey, Water Resources Division, New Cumberland, PA 17070, USA
c School of Marine Science, Virginia Institute of Marine Science, The College of William and Mary, Gloucester Point, VA 23062, USA
d Department of Civil and Environmental Engineering and Geodetic Science, The Ohio State University, Columbus, OH 43210, USA
Received 11 January 2001;
accepted 13 November 2001
Editorial handling by B. Kimball
Available online 16 February 2002.
Abstract
The pH of mine impacted waters was estimated from the spectral reflectance of resident sediments composed mostly of chemical precipitates. Mine drainage sediments were collected from sites in the Anthracite Region of eastern Pennsylvania, representing acid to near neutral pH. Sediments occurring in acidic waters contained primarily schwertmannite and goethite while near neutral waters produced ferrihydrite. The minerals comprising the sediments occurring at each pH mode were spectrally separable. Spectral angle difference mapping was used to correlate sediment color with stream water pH (r2=0.76). Band-center and band-depth analysis of spectral absorption features were also used to discriminate ferrihydrite and goethite and/or schwertmannite by analyzing the 4T1←6A1 crystal field transition (900–1000 nm). The presence of these minerals accurately predicted stream water pH (r2=0.87) and provided a qualitative estimate of dissolved SO4 concentrations. Spectral analysis results were used to analyze airborne digital multispectral video (DMSV) imagery for several sites in the region. The high spatial resolution of the DMSV sensor allowed for precise mapping of the mine drainage sediments. The results from this study indicate that airborne and space-borne imaging spectrometers may be used to accurately classify streams impacted by acid vs. neutral-to-alkaline mine drainage after appropriate spectral libraries are developed.
Assessing mine drainage pH from the color and spectral reflectance of chemical precipitates (full article)