ENVIRONMENTAL CHEMISTRY FOR A SURFACTANT ECOTOXICOLOGY STUDY SUPPORTSRAPID DEGRADATION OF C-12-ALKYL SULFATE IN A CONTINUOUS-FLOW STREAM MESOCOSM

Environmental chemistry is a vital part of ecotoxicology studies condu cted in mesocosms. Quantification of exposure can be particularly chal lenging for biodegradable surfactants in once-through stream mesocosms like the Procter & Gamble Experimental Stream Facility (ESF). In the fall of 1991, a study was conducted with the anionic surfactant C-12-a lkyl sulfate (C-12-AS). Analysis of chemical feed tank concentrates in dicated that the in-stream concentrations should be very close to the nominal concentrations (26, 78, 233, 700, 2,100 mu g/L). However, meas ured concentrations were lower than expected. The concentrations at th e head of the streams were 4 to 23% below nominal concentrations and t here was an additional 14 to 33% decline in head to tail C-12-AS conce ntrations. Total residence time in the streams is about 4.3 min. Becau se analytical losses had been minimized using individual sample recove ry factors, it was concluded that these losses were due to rapid C-12- AS biodegradation. The results of this analytical program are used to define the in-stream C-12-AS concentrations to express subsequent comm unity- and ecosystem-level no-observed-effect concentrations. In addit ion, the environmental chemistry program described will serve as the m odel for future programs in support of surfactant ecotoxicology studie s conducted at the ESF.