Investigation of correlation between physiochemical properties of metals and their toxicity to the water flea Daphnia magna Straus.

Twenty-three metal ions were tested and ranked in terms of decrease in immobilization (EC50) of Daphnia magna Straus. The 48-hr EC50 values (mg/liter) of metal ions were Hg2+, 0.0052; Ag1+, 0.01; Cu2+, 0.093; Zn2+, 0.56; Co2+, 1.49; Cr6+, 1.79; Cd2+, 1.88; Be2+, 2.82; Pb2+, 3.61; As3+, 6.23; Fe2+, 7.20; Ni2+, 7.29; Mn2+, 8.28; Sn2+, 21.56; Ba2+, 32.00; Al3+, 59.60; W6+, 89.39; Sr2+, 94.00; K1+, 141.46; Mg2+, 343.56; Na1+, 420.60; and Sb3+, 423.45. The 48-hr EC50 values of 23 metal ions were transformed to their corresponding negative logarithms of molarity (as pM). Correlation coefficients (r) for more than 35 physiochemical properties of metals or metal ions and acute toxicity values (as pM) were examined by linear regression analysis. The negative logarithm of the solubility product constant of metal sulfide (pKsp), equilibrium constants of amino acids and of EDTA, nucleotide base, electronegativity, electrode potential, melting point, thermal properties of metals, and other physiochemical parameters were significantly correlated with toxicity for D. magna. The order of toxicity of metal ions has been presented and discussed. Correlation between toxicity and physiochemical properties of inorganic substances may be useful in predicting toxicity to various biologically important organisms.