2002-07-08_GENERAL DOCUMENTS - M2002004 (3)

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mall WI or liluvial clay and silt in 100- 15) described a few thin clay films on ed in l5'or 20 yr. However, Roberts et on after 4 yr, and Thomas and Jansen :.ation in 5- to 64 -yr -old minesoils in served Bw horizons in minesoils con - ;isting of siltstone but indicated that requirements to be true cambic hori- ;erved in minesoils with at least 25% ed Bw horizons in some 20- to 40 -yr- tures were too coarse to be cambic. zons in 26 of 100 profiles randomly of Columbia, and classified them as e classified as Entisols. All of these fill material from excavations during »'n Washington that began in 1872 ave been described or predicted in ribed in extremely acidic minesoils & Sencindiver, 1990). Gypsum has ig to the speculation that gypsic or Doolittle et al., 1993). In Wisconsin in of gypsum and iron oxides and , ulfuric mine waste. Daniels et al. w horizons in 5- to 15 -yr -old sandy Florida. less with time. In Pennsylvania m estimated to develop at approxi- 3 to 13 yr, the A -AC sequence has as formed in 12 to 28 yr. Varela et ' in lignite minesoils in Spain. On A horizons of 5 or 6 cm thickness seasons (Roberts et al., 1988a). •m) and darker eight growing sea - iolkosz et al., 1983) indicates that s less than 30 yr old, even though vever, higher extractable K levels of other minesoils may be due to rizons (Daniels & Amos, 1981; sd that after initial disturbance on ppi, there was a striking increase Neathering products. Singh et al. )unted for by oxidation of pyrite. X. SULFURICIZATION Sulfuricization is the process by which sulfide minerals, such as pyrite (FeS are oxidized, minerals are weathered by the sulfuric acid produced, and new mineral phases are formed from the dissolution process (Fanning & Fan- ning, 1989; Fanning & Burch, 2000, see Chapter 36). Sulfuricization may be the most important soil- forming process in acid minesoils developing in pyritic materials (McCloy & Sencindiver, 1991). Soils that have undergone this process are called acid sulfate soils. Acid sulfate weathering (sulfuricization) produces an extremely low pH, yellow jarosite [KFe mottles, sul- fate ions, and cations such as Ca', Mg', K +, and Ala +. These ions may accu- mulate faster than they can be leached. This process leads to the development of sulfuric horizons. Pennsylvania minesoils 2 to 3 yr old had electrical conductivities (EC) of 1 to 3 dS m - ' (Ciolkosz et al., 1985). West Virginia minesoils developing in mate- rials exposed by the mining of Kittanning coal and less than 5 yr old had EC val- ues >2 dS - ', and EC increased below the limed surface layer indicating that pyrite oxidation may be more rapid in the nonlimed subsoil (Sencindiver et al., 1989). Electrical conductivity values in topsoil used for reclamation were less than 2 dS m - '. Older minesoils (15 -35 yr old) from the same geologic materials showed EC values below 1 dS m indicating leaching of soluble cations to greater depths (Johnson & Skousen, 1995). Rather high free iron oxide contents, similar to those found in surrounding native soils, also may be related to rapid Fe release during sulfuricization (Ciolkosz et al., 1985; Singh et al., 1982). XI. SODIUM MIGRATION Sodium migration and accumulation is a concern in minesoils of the north- ern Great Plains (Dollhopf et al., 1985; Merrill et al., 1980). When nonsodic top- soils are placed over sodic spoils (sodium adsorption ratio >15), the topsoils may become sodic over time as the salts wick up resulting in decreased plant per- formance. Although water movement may be limited across spoil - topsoil inter- faces because of clayey textures, the soil remains moist because of high water - holding capacity. Under these conditions, unsaturated hydraulic conductivity is very low, so Na may migrate from the subsoil to the topsoil by diffusion (Merrill et al., 1980). Upward migration of Na has been detected after 2 yr (Dollhopf et al., 1985) and may cause the topsoil to become sodic in 18 to 36 yr. Some por- tions of the topsoil may reach EC levels of up to 4 dS m - ' in 10 to 14 yr. Upward migration of salts is largely a function of texture and mineralogy (Dollhopf et al., 1985). If sodic minesoils have <35% clay or >45% sand, upward migration of salts will probably be very slow, and topsoils may never become