Phytotoxicity of single and combined polycyclic aromatic hydrocarbons toward economic crops

Toxicity of anthracene, fluoranthene, fluorene, phenanthrene, and the mixtures of these polycyclic aromatic hydrocarbons (PAHs) to three economic crops in Thailand was compared. Seeds of sweet corn, waxy corn, and rice were planted in soils contaminated with each PAH alone, binary mixtures, and total four PAH mixture. Rice seedlings were most sensitive to PAHs. Germination of sweet corn, waxy corn, and rice seeds was delayed by single PAH and their mixtures, especially at their high concentrations. More than 20 mg/kg of anthracene and 2 mg/kg of phenanthrene significantly retarded the seed germination rate in waxy corn. Root and shoot elongation were more sensitive to toxic PAHs than other growth indices. Fluorene was more toxic to all the tested plants than other PAHs. (Anthracene + fluoranthene) was most toxic to plants when compared with other PAH mixtures. There was synergistic combine effect of PAHs on corn root length, but there were antagonistic combine effects on fresh weights of both plants and rice root length. PAH mixtures did not affect dry weights of all plants.