Abiotic factors affecting the toxicity of lead to fungi.

The toxicity of lead (Pb) to fungi in pure culture was influenced by several abiotic factors: pH, inorganic anions, clay minerals, and particulate (humic acid) and soluble organic matter. The toxicity of Pb was potentiated under acidic conditions (pH 5 and 6), and phosphate or carbonate anions reduced the toxicity, apparently as a result of the formation of sparingly soluble Pb salts. Clay minerals (montmorillonite greater than attapulgite greater than kaolinite) and particulate humic acid protected against the toxicity of Pb, presumably as the result of sorption, by cation exchange of the Pb to the exchange complexes, which reduced its availability for uptake by the fungi. Soluble organics, such as tryptone, yeast extract, cysteine, succinic acid, and increasing concentrations of neopeptone, also reduced the toxicity of Pb.