In a laboratory incubation study, the effect of select heavy metals on meth
ane (CH4) production in three rice soils was investigated under flooded con
ditions. Heavy metals behaved differently in their effect on methanogenesis
in different soils and methane-producing bacteria. Cd, Cu, and Pb inhibite
d CH4 production in all the soils. Zn stimulated CH4 production in the allu
vial soil, but inhibited it in laterite and acid sulfate soils. Cr effectiv
ely inhibited CH4 production in the alluvial soil, but stimulated it in lat
erite and acid sulfate soils. The stimulatory effect of Zn and the inhibito
ry effect of Cr on methanogenesis in alluvial soil were attributed to their
stimulation or inhibition of methanogenic bacterial population. (C) 1999 A
cademic Press.