WATER REACTIVITY OF A VARIETY OF EARTH MATERIALS

Water-induced leaching of major, minor, and trace elements, acids, bases, organics, pharmaceuticals, and a wide range of other constituents from natural and man-made materials is a global environmental concern. In order to assess and characterize this potential, the U.S. Geological Survey (USGS) developed a fast (5-minute agitation), versatile, and cost-effective leach test that uses deionized water (DI) to reveal the water soluble, water reactive fraction of a sample. As part of development, a comparison study was conducted between the USGS Field Leach Test (FLT) and the EPA Method 1312 (SPLP) leaching test. After leaching, filtrate was analyzed for a variety of parameters and constituents using a wide variety of analytical methods. Results revealed that both tests produce similar leachate geochemical signatures even though the SPLP requires an 18-hour agitation and the FLT only a 5-minute agitation. Further, we determined that for non-regulatory purposes, the FLT can be used as a surrogate for the SPLP. For more than a decade, USGS scientists and others have used the FLT to conduct leach studies to reveal, characterize, and understand the water reactive components of a broad variety of earth materials. The FLT has been an important part of both reconnaissance studies and studies conducted as part of rapid response efforts due to natural and man-made disasters. We provide examples of selected studies that have used the FLT to characterize samples including metal mine-wastes, metal-mining affected wetland sediments, dust produced from the collapse of the World Trade Center towers, dried windblown lake sediments, assorted building materials, treated municipal biosolids, hurricane induced flood sediments, volcanic and wildfire ash, lead contaminated soil produced from artisanal gold mining, and dried flood sediments resulting from the collapse of an aluminum mine tailings impoundment in Hungary. We also performed microscopic characterization of many of these materials which revealed highly reactive surfaces and the presence of readily soluble salts that are effectively taken into solution using the FLT.