The Waste Research Unit has developed several laboratory tests to investigate the attenuation of toxic species disposed to landfill, to provide pragmatic guidance for environmentally acceptable codisposal of industrial and municipal wastes. Sevencolumn experiments were set up to investigate the fate of eight metals (cadmium, chromium, copper, iron, lead, mercury, nickel, and zinc) released in solution onto pulverized municipal waste. Leachate and destructive analysis revealed that only nickel migrated through 0.5 m of waste, giving typical leachate concentrations of 20 mg/dm3, although upwards of 80% of the nickel was removed from solution. The other metals were precipitated or absorbed very rapidly and were mainly found in the top 0.2 m. Fatty acid production was completely inhibited by the immobilized metals, leading to near-neutral pHs in these areas. Penetration of the dissolved metals was greater with a continuously applied dilute solution than with a brief dose of comparable loading.