ScienceAsia 27 (2001) : 157-164 |doi: 10.2306/scienceasia1513-1874.2001.27.157

Effects of Humic Acid and Water Hardness on Acute Toxicity and Accumulation of Cadmium in the Freshwater Fish ( Puntius gonionotus Bleeker )

R Mungkung^a, ES Upatham^b, P Pokethitiyook^{c *}, M Kruatrachue^c and C Panichajakul^a

ABSTRACT: The effects of humic acid and water hardness on acute cadmium toxicity and accumulation were determined, using Puntius gonionotus Bleeker. The toxicities were expressed as the median lethal concentration (LC₅₀) and the 96-h LC₅₀ value of cadmium was 2.30 mg/L. Three different types of water hardness were used: soft, moderately-hard and hard, with total hardness concentrations of 55, 113, and 225 mg/L CaCO₃, respectively. The acute cadmium toxicity and accumulation significantly decreased by increasing water hardness concentration. An increase in humic acid concentrations (0.5, 5.0, and 50 mg/L) also decreased cadmium toxicity and accumulation. Moreover, simultaneous increases in humic acid and water hardness concentrations also resulted in a decrease in cadmium toxicity. However, they were less effective in decreasing cadmium accumulation than the effect of water hardness or humic acid alone.

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a Department of Environmental Science, Faculty of Science, Kasetsart University, Bangkok 10220, Thailand.
b Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, and Faculty of Science, Burapha University, Chonburi 20131, Thailand.
c Department of Biology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.

* Corresponding author, E-mail: grpph@mahidol.ac.th

Received 22 Jan 2001, Accepted 3 May 2001