Abstract: In July 2007, an investigation was made on the mollusks, arthropods, and chordates in the Dayan cave of Guangxi Province. A total of 3324 specimens of the cave animals were collected, belonging to 26 families, 30 genera, and 50 species. Among these specimens, Diestrammen, Fruticicolidae, Araneida, and Amphibia occupied 3052 totally, belonging to 42 species. The contents of Fe, Cu, Cd, Pb, Hg and As in these four groups of cave animals and in the water and soil samples from the cave were determined, and the enrichment coefficients of the heavy metals for these four animal groups were calculated. In the water and soil samples, the content of Mn was the highest, being 6.75 mg·L^-1in water and 2112 mg·kg^-1 in soil. Among the four animal groups, Diestrammena, Fruticicolidae and Amphibia had the highest content of Mn (45.3 mg·kg^-1, 858 mg·kg^-1, and 254 mg·kg^-1, respectively), while Araneida had the highest content of Cu (79 mg·kg^-1). Except that the enrichment coefficient of Fe from water for Diestrammena was <1000, the enrichment coefficients of the heavy metals from water for all the four groups were >1000. The four animal groups could also enrich soil Pb, Cd and Hg, with the enrichment coefficients being >1. For the same groups of test animals, the enrichment coefficients of the heavy metals differed; and for the same species of test heavy metals, their enrichment by different groups of the animals also differed. Correlation analysis showed that the accumulation of the heavy metals in the test animals was positively correlated with the contents of the heavy metals in environment. The enrichment of the heavy metals by the cave animals was not only affected by the synergistic and antagonistic effects among the heavy metals, but also closely related to the contents of the heavy metals in the cave water and soil.

Key words: OLAND, Biological nitrogen removal, Dissolved oxygen