Alan W. Maki

Estimating the hazard of chemical substances to aquatic life

The assessment of the hazard associated with the introduction of chemical substances into the environment is receiving considerable attention in current ecological, political, and public forums. The purpose of this paper is to identify and evaluate the basic concepts involved in assessing the hazard of chemical substances to aquatic life. A conceptual framework for conducting a hazard assessment is elaborated. In addition, several proposed procedures for conducting aquatic hazard assessment are compared and contrasted. A discussion of the decision criteria currently utilized in hazard assessment procedures is included. The use of safety factors or ‘uncertainty factors’ as a central concept in a sequential testing approach is presented. An assessment of the ‘state-of-the-art’ in aquatic hazard assessment and recommendations for suceeding stpes in the development of procedures constitute the conclusion of the paper.

Acute toxicity studies of surfactants toDaphnia magna andDaphnia pulex

AbstractSeveral experiments were designed to examine the acute toxicity of surfactants toDaphnia. Specific tests were designed to develop comparisons between existing acute toxicity data for fish and similar data forDaphnia, and to provide data on the effects of various environmental factors on resultant toxicity of surfactants toDaphnia. Acute toxicity data for a series of homologous linear alkyl benzene sulfonates (LAS) demonstrate increases of up to one order of magnitude in toxicity for each increase of two alkyl carbons. LC 50s obtained withDaphnia magna are similar to those obtained with bluegills,L. Macrochirus. Comparative tests withD. magna andD. pulex indicate no statistical differences in 48-hr LC 50 values for three anionic and two nonionic surfactants. A 50 mg/L concentration of suspended, naturally-occurring kaolin significantly reduced the toxicity of longer chain length LAS homologs and had no effect on nonionic surfactant toxicity.In tests with variable hardness concentrations, the acute toxicity of LAS toD. magna is a combined function of both culture and test water hardness. The toxicity of a nonionic surfactant toD. magna was higher in soft water and was not affected by culture water hardness levels.Unlike previously published data for fish, the results of acute toxicity tests withD. magna cultures previously exposed to 0.4 mg/L LAS for periods up to seven generations indicated no significant difference in LAS susceptibility compared to simultaneously tested unexposed controls.

The impact of detergent phosphorus bans on receiving water quality

Abstract One of the chemicals most clearly exemplifying scientific and political controversy concerning efforts to control its discharge to surface waters is phosphorus and its complexes. These materials are discharged as natural components of domestic wastewaters and include phosphorus from human waste and food waste as well as residual detergent phosphorus. Significant amounts of phosphorus also reach surface waters from non-point sources such as agricultural and urban runoff. This paper presents results of several field and laboratory investigations designed to position the impact of detergent phosphorus contributions to surface water quality. In a number of areas where legislation banned the sale of phosphorus detergents, limnological investigations were carried out to assess the impact of the ban upon receiving water quality. Field studies in natural lakes demonstrate that reductions of phosphorus in wastewaters, even up to 50%, may not substantially improve the trophic status of lakes. The consistent conclusion emerging from these studies is that the elimination of detergent phosphorus has not measurably improved lake water quality.

Effects of water hardness and diet on productivity of Daphnia magna Straus. in laboratory culture

The effects of diet and water hardness, alone and in combination, on life history characteristics of Daphnia magna were determined in two laboratory tests. Number of young on the first day of reproduction, total young and the number of generations were greater with increasing hardness. At the maximum test hardness of 350 mg/l (as CaC03), approximately 65% more young were produced than at the lowest hardness of 50 mg/l (as CaCO3). Furthermore, time to sexual maturity was about one day shorter in the harder culture water. Daphnids fed the combination of a green alga, trout chow and dehydrated alfalfa were over three times more productive than daphnids fed only the alga or only trout chow and alfalfa. The combination of the algae-reinforced diet with hard culture water provided for optimal productivity.

Modifications of Continuous-Flow Toxicity Test Methods for Small Aquatic Organisms

Abstract Modifications of the standard proportional diluter are described for the continuous-flow toxicity testing of small aquatic organisms; the modifications provide for a 95% water volume replacement time of 2.5 h or less, with no perceptible current-induced effects on the test individuals. The system permits the automatic introduction of known concentrations of food at each diluter cycle and has application to the testing of pelagic invertebrates or larval fish.