IN-SITU RESPONSE OF NATURAL PERIPHYTON TO AN ANIONIC SURFACTANT AND AN ENVIRONMENTAL RISK ASSESSMENT FOR PHYTOTOXIC EFFECTS

In situ toxicity tests were conducted to determine the toxicity of lin ear alkyl- (dodecyl-) benzenesulfonate (LAS) on a natural periphyton c ommunity. Colonized periphyton were exposed to C-11.9-LAS in 21-d cont inuous-flow toxicity studies conducted in the Little Miami River (Ohio ) above and below a wastewater treatment plant outfall. The lowest mea sured first-effect levels were 3.3 and 16.6 mg/L, respectively, in the two locations, based on reductions in structural and functional commu nity characteristics. The presence of 20 to 30% effluent did not incre ase the toxicity of LAS. The field-derived effect levels confirmed the low phytotoxicity observed in most previously conducted laboratory to xicity studies with cultured algae. In addition, the field-derived eff ect levels exceeded measured environmental concentrations, which suppo rts the environmental safety of LAS to periphyton.