Nitrogen transformations and nitrate leaching in mine soils reclaimed with sewage sludge and coal combustion residues.

Nitrogen mineralization and nitrate leaching were investigated in an acid mine soil reclaimed with sewage sludge (SS) and coal combustion residues (CCR). In the field experiments mine soil was amended with three rates of SS (0, 1200, and 2400 kg N ha{dollar}\\sp{lcub}-1{rcub}){dollar} and two types of CCR, i.e. fly ash (FA) and fluidized bed waste (FBW) applied at rates equivalent to once and twice the lime requirement of the soil. Laboratory incubation experiments using two procedures (leached and nonleached) were also conducted for 46 weeks to investigate N mineralization in an acid mine soil with or without liming agents (agricultural lime and FBW), and in two fly ashes (one alkaline and the other near neutral) used as top soil substitutes. Sewage sludge was added to supply 0, 600, 1200, and 2400 kg N ha{dollar}\\sp{lcub}-1{rcub}.{dollar} Application of SS alone or along with CCR resulted in a soil solution NO{dollar}\\sb3\\sp{lcub}-{rcub}{dollar}-N concentration in excess of drinking water standard limit of 10 mg L{dollar}\\sp{lcub}-1{rcub}{dollar} for the initial six to seven months of the experiment. Both mineral N and NO{dollar}\\sb3\\sp{lcub}-{rcub}{dollar}-N in soil solution decreased with time and remained below 10 mg L{dollar}\\sp{lcub}-1{rcub}{dollar} after seven months. Laboratory incubation studies demonstrated that cumulative N mineralized after 46 weeks expressed as percentage of organic N added was inversely related to the rate of SS applied in both leached and nonleached procedures. Less N was mineralized when SS was added to fly ashes than to the topsoil. Addition of SS resulted in gaseous losses of nitrogen. The losses were mainly due to NH{dollar}\\sb3{dollar} volatilization in alkaline FA and by denitrification in the mine soil and neutral FA. The results of the field study showed that FA amended with SS can serve as an acceptable growth media for revegetation