| Title |
Effect of Water Hardness on Toxicity of Cadmium and Zinc |
| Authors |
윤성호 ( Sung Ho Yoon ) ; 하홍주 ( Hong Joo Ha ) ; 이성종 ( Sung Jong Lee ) ; 조은혜 ( Eun Hea Jho ) |
| DOI |
https://doi.org/10.15681/KSWE.2017.33.5.556 |
| Keywords |
Cadmium; Daphnia magna; Hardness; Toxicity; Zinc |
| Abstract |
Heavy metals in water systems are being managed on the concentration-based guidelines in Korea. However, various chemicals present in water can interact with heavy metals affecting their toxicity. Such interactions are not considered in the concentration-based guidelines. This study investigated the effect of hardness and coexisting heavy metals on heavy metal toxicity to emphasize the importance of having the effect-based guidelines together with the concentration-based guidelines in water management. The toxic effects of Cd, Zn, or mixtures of Cd and Zn were studied with Daphnia magna as a test species following the standard test method at different hardness conditions (100, 200, and 300 mg L-1 as CaCO3). The toxicities of single metal solutions and mixtures showed a decreasing trend with increasing hardness, and this can be attributed to the competition between heavy metals and cations such as calcium ions (Ca2+) that cause hardness. The predicted toxicities of the heavy metal mixtures from the single metal toxicity deviated from the measured toxicities, and the predicted toxic effects tend to be greater than the measured toxic effects suggesting that Cd and Zn are in competition. This shows the limitations of using predicted toxic effects and the needs for further studies on mixture toxicities. Overall, this study shows that the management of heavy metals in waters needs to employ the effect-based guidelines together with the concentration-based guidelines. |