602 SENCIND[VER & AMNIONS
<br />29 yr (Ciolkosz et al., 1983), 17 of 24 pedons had an AC and /or a B2 (Bw) hori-
<br />zon described. Five of these pedons had weakly developed cambic horizons.
<br />Hallberg et al. (1978) observed an accumulation of illuvial clay and silt in 100 -
<br />yr -old minesoils, and Ciolkosz et al. (1985) described a few thin clay films on
<br />ped faces or in pores that apparently formed in 15 or 20 yr. However, Roberts et
<br />al. (1988b) found no evidence of illuviation after 4 yr, and Thomas and Jansen
<br />(1985) found no evidence of clay translocation in 5- to 64 -yr -old minesoils in
<br />Illinois. After 8 yr, Haering et al. (1993) observed Bw horizons in minesoils con-
<br />structed from coal overburden strata consisting of siltstone but indicated that
<br />these horizons did not meet the alteration requirements to be true cambic hori-
<br />zons. Only A, AC and C horizons were observed in minesoils with at least 25%
<br />sandstone. Strain and Evans (1994) described Bw horizons in some 20- to 40 -yr-
<br />old sand- and gravel -pit soils, but the textures were too coarse to be cambic.
<br />Short et al. (1986b) described cambic horizons in 26 of 100 profiles randomly
<br />located on the Mall in Washington, District of Columbia, and classified them as
<br />Inceptisols. The remaining 74 profiles were classified as Entisols. All of these
<br />soils formed in about 6 m of miscellaneous fill material from excavations during
<br />construction of federal buildings in downtown Washington that began in 1872
<br />(Short et al., 1986a).
<br />Other types of subsurface horizons have been described or predicted in
<br />minesoils. Sulfuric horizons have been described in extremely acidic minesoils
<br />exhibiting active pyrite oxidation (McCloy & Sencindiver, 1990). Gypsum has
<br />accumulated in some Texas minesoils leading to the speculation that gypsic or
<br />petrogypsic horizons could eventually form (Doolittle et al., 1993). In Wisconsin
<br />(McSweeney & Madison, 1988), precipitation of gypsum and iron oxides and
<br />hydroxides has formed a Bm horizon in a sulfuric mine waste. Daniels et al.
<br />(1992) observed the presence of thin Bh and Bw horizons in 5- to 15 -yr -old sandy
<br />tailings derived from mineral sand mining in Florida.
<br />Minesoil horizons increase in thickness with time. In Pennsylvania
<br />(Ciolkosz et al., 1985), minesoil sola have been estimated to develop at approxi-
<br />mately 1.6 cm yr'. A horizons have formed in 3 to 13 yr, the A -AC sequence has
<br />formed in 6 to 20 yr, and the A -Bw sequence has formed in 12 to 28 yr. Varela et
<br />al. (1993) reported soil formation of 2.4 cm yr' in lignite minesoils in Spain. On
<br />constructed minesoil plots in Virginia, distinct A horizons of 5 or 6 cm thickness
<br />developed on the minesoils after four growing seasons (Roberts et al., 1988a).
<br />These A horizons were slightly thicker (5 -11 cm) and darker eight growing sea-
<br />sons after construction (Haering et al., 1993).
<br />Mineralogy of Pennsylvania minesoils (Ciolkosz et al., 1983) indicates that
<br />clay minerals have not been altered in minesoils less than 30 yr old, even though
<br />some of the minesoils are extremely acidic. However, higher extractable K levels
<br />in surface horizons than in subsurface horizons of other minesoils may be due to
<br />accelerated weathering of mica in surface horizons (Daniels & Amos, 1981;
<br />Singh et al., 1982). Ammons et al. (1991) reported that after initial disturbance on
<br />a pyritic disposal area spoil in northeast Mississippi, there was a striking increase
<br />in pyrite oxidation, which released Fe and K as weathering products. Singh et al.
<br />(1982) observed more total Fe than could be accounted for by oxidation of pyrite.
<br />MINESOIL GENESIS AND CLASSIFI(
<br />They suggested this additional Fe
<br />biotite or siderite.
<br />X. SUI
<br />Sulfuricization is the proce
<br />(FeS,), are oxidized, minerals are
<br />new mineral phases are formed fi
<br />ning, 1989; Fanning & Burch, 2(
<br />the most important soil - forming p
<br />materials (McCloy & Sencindi‘
<br />process are called acid sulfate so
<br />produces an extremely low pH, ye
<br />fate ions, and cations such as Ca:
<br />mulate faster than they can be let
<br />of sulfuric horizons.
<br />Pennsylvania minesoils 2 to
<br />to 3 dS m' (Ciolkosz et al., 1985)
<br />rials exposed by the mining of Kitt
<br />ues >2 dS -1 , and EC increased belo
<br />oxidation may be more rapid in th
<br />Electrical conductivity values in to
<br />m Older minesoils (15 -35 yr old
<br />values below 1 dS In - ' indicating
<br />(Johnson & Skousen, 1995). Rathe
<br />found in surrounding native soils,
<br />sulfuricization (Ciolkosz et al., 19
<br />XI. SOD
<br />Sodium migration and accun
<br />ern Great Plains (Dollhopf et al., 1
<br />soils are placed over sodic spoils (<
<br />become sodic over time as the sa
<br />formance. Although water movem
<br />faces because of clayey textures,t
<br />holding capacity. Under these con
<br />very low, so Na may migrate from
<br />et al., 1980). Upward migration of
<br />al., 1985) and may cause the tops(
<br />tions of the topsoil may reach EC ;
<br />Upward migration of salts is
<br />(Dollhopf et al., 1985). If sodic mil
<br />migration of salts will probably b
<br />
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