| Summary: | Mixture of fly ash (FA) and sewage sludge (SS) has been used as substrates to plant vegetables and turf grasses. Most studies chemically analyzed physiochemical properties of leachates from FA/SS mixtures, but did not considered the effects of plants growing on leaching properties, and the toxicity of leachates on aquatic animals were not well understood. In the present study, FA and SS were mixed in different ratios and then used to cultivate Zoysia matrella and Cynodon dactylon. After one month, these artificial soils were irrigated with water and leachates were collected for three months. Chemical analyses revealed that, although the heavy metal concentrations of FA and SS almost conformed to the relevant national standards, the levels of Cr, Zn, Cd, Pb and Cu in leachates still exceeded the limits in the Chinese Standard of Surface Water Quality, displaying potential environmental hazards. The effects of leachates on reproduction of Daphnia magna were evaluated and the results showed that leachates from high proportion of FA or SS would both negatively affect D. magna, demonstrating an environmental risk. However, leachates from mixture with FA: SS ratio from 1: 2 to 1: 6 did not significantly affect D. magna. Overall, the present results suggested that applications of FA/SS mixtures as artificial soil potentially contaminated aquatic environments and should be monitored carefully.
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