Abstract
Emissions of SO2 from smelters can promote formation of acid rain, which can dissolve siliceous minerals on exposed rock surfaces and promote the formation of silica gel layers within which detrital and smelter-derived particulates can become trapped. These processes of dissolution and entrapment can result in the formation of rock coatings that contain elevated levels of heavy metals. Between 1927 and 1976, the Horne smelter processed sulfide ore derived from the Rouyn-Noranda region and became one of the largest emitters of particulates and sulfur dioxide in North America, promoting the formation of coatings on nearby rock surfaces. The reflectance spectra of these coatings are relatively flat, with typical reflectance values ranging between ~5% at visible wavelengths and ~16% in the shortwave infrared. Absorption troughs in coating spectra are consistent with the presence of materials including opaline silica, olivine, pyroxene, hydrous phyllosilicates, and sulfates. Classification of Landsat 8 Operational Land Imager data indicates that rock coatings near Rouyn-Noranda comprise a total surface area of ~1.5 km2, nearly all of which is located within ~6 km of the Horne smelter. Remote sensing techniques can used to delineate the geographic extents of coatings near smelters, highlighting areas previously subjected to severe environmental degradation.
Highlights
This study extended the scope of earlier work at Sudbury, Ontario, to the Rouyn-Noranda region of Quebec (Fig. 1), in order to further evaluate remote sensing techniques in the detection, mapping, and characterization www.nature.com/scientificreports/
A reflectance database derived from Landsat 8 Operational Land Imager (OLI) data for this region was classified in order to determine the spatial distribution of rock coatings produced by the Horne smelter, and to further evaluate the utility of remote sensing techniques in the study of environmental degradation caused by smelters
Results generated in this study, including those related to both the spectral characterization of Rouyn-Noranda rock coatings and the generation of a map of prominent rock coatings in the study area, are given below
Summary
This study extended the scope of earlier work at Sudbury, Ontario, to the Rouyn-Noranda region of Quebec (Fig. 1), in order to further evaluate remote sensing techniques in the detection, mapping, and characterization www.nature.com/scientificreports/. A reflectance database derived from Landsat 8 Operational Land Imager (OLI) data for this region was classified in order to determine the spatial distribution of rock coatings produced by the Horne smelter, and to further evaluate the utility of remote sensing techniques in the study of environmental degradation caused by smelters. Bedrock of the northern and central parts of the study area is dominated by Archean igneous materials of the Blake River Group, a southern unit of the Superior Province’s Abitibi greenstone belt[21,22]. Cobalt Group materials within Quebec have been subjected to low-grade metamorphism[27], but the Pontiac Subprovince is of medium metamorphic grade near its northern boundary with the Abitibi greenstone belt[28]. Volcanic units of the Blake River Group were intruded by several generations of plutons, dikes, and sills[26], with the most prominent intrusions including the Flavrian and Powell tonalites and the Lac Dufault granodiorite[29,31] (Fig. 2)
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