抄録
Dissolved organic matter (DOM) significantly relates to the speciation of heavy-metal ions in aquatic environments. To evaluate the toxicity changes of heavy-metal ions induced by the existence of DOM or dissolved humic substances (DHS), a microscaled algal growth inhibition (μAGI) test was conducted using a commercially available 96-well micro-plate. The μAGI test was compared with a regular AGI test using an Erlenmeyer flask. A regular AGI test is not very beneficial for accessing the toxicity of chemicals in an aqueous solution containing DOM or DHS because it absorbs visible light, which is required for algal growth. However, in this study, we clarified that the amount of algal growth in the μAGI test is hardly affected even at a high DHS concentration. The changes in the toxicity of copper to Chlamydomonas reinhardtii were evaluated under two conditions of the μAGI test, that is, with and without DOM/DHS. DOM and DHS samples were extracted from freshwater samples from Sakata in Niigata prefecture, Japan. The toxicity mitigation coefficients (TMCs) at 10 mgC · l-1 DOM and DHS were estimated to be 1.4-2.7 and 4.8, respectively. Evidence found in this study shows that DHS strongly reduces the toxicity of copper (II) to algae, as compared with nonhumic components in DOM.
