SOIL COLOR VARIATIONS ALONG AN IRON-OXIDE GRADIENT IN A MINE DRAINAGETREATMENT WETLAND

The relationship between soil color and iron oxide content in a surfac e-flow constructed wetland that successfully treats acid mine drainage (AMD) is examined with regard to its potential importance to wetland treatment of AMD. Twenty-one oxidized surficial soil samples (<5 cm de pth) were collected along a 100-meter wetland transect and were charac terized for Munsell color and iron oxide content. Soil color, expresse d in terms of both a redness index as well as dominant wavelength, was found to be significantly correlated (p < 0.001) with iron oxide cont ent. In addition, an apparent red-shift in soil color was observed fro m the wetland effluent toward the influent in response to increasing c oncentrations of iron in both the soil and the drainage water. If this relationship between soil color-iron oxide content-iron removal is sh own to exist for other surface-flow AMD wetlands, evaluation of soil c olor can give a relatively quick and inexpensive estimate of iron rete ntion for a given influent iron concentration entering a wetland.