University of Illinois at Urbana-Champaign. Water Resources Center
Abstract
Individual toxicant concentrations in the Illinois River were expressed as fractions of their 96-hr LC50 values to bluegills, yielding their component toxicities in bluegill toxic units (BGTU’s). A solution having a toxicity of 1.0 BGTU was defined as being lethal to 50 percent of the bluegills exposed to it for 96 hr. River toxicants included aldrin, undissociated ammonia (ammonia₍ᵤ₎), arsenic, cadmium, hexavalent and trivalent chromium, copper, cyanide, fluoride, linear alkylate sulfonate (LAS), lead, mercury, phenols, and zinc. Component toxicities at different locations on the river were summed to produce the toxicity index, or total toxicity, of the river. Preliminary mean toxicity indices developed from previously published data during 1972 and 1973 ranged from 0.045 to 0.168 BGTU's, on the Illinois and Des Plaines rivers. However, maximum component toxicities of ammonia₍ᵤ₎ and cyanide during this period reached 0.630 and 0.467 BGTU's, respectively. LAS, copper, fluoride, and zinc also contributed to the preliminary river toxicity indices. Mean toxicity indices developed during field tests, in which bluegills were exposed directly to river water, and the lack of mortality at these tests, indicated that the Illinois River is not normally acutely toxic to fish. The 96-hr LC50 values of ammonia₍ᵤ₎ and LAS to bluegills were found to be 1.65 and 6.5 mg/liter, respectively, using continuous-flow bioassays with dilution water similar in hardness, alkalinity and pH to Illinois River water.U.S. Department of the InteriorU.S. Geological SurveyOpe
