Toxicity tests of aquatic pollutants by using common duckweed

The objective of this study was to develop a phytoassay procedure using common duckweed. The results suggest that the assay is simple, sensitive and very economical.

Those substances evaluated for relative toxicity by the phytoassay included most of the constituents listed in Illinois' general standards for water quality. Based on the duckweed assay, the maximum permissible concentrations of Ba(II), Cd(II), Fe(III), Ni(II), and Se(IV) are lower than the water quality standards. On the other hand, similar limits for B(III), Cr(VI), Cu(II), F(I), Pb(II), Mn(II), SO₄(II) and phenol are higher than those concentrations stipulated in the water quality standards. For Cl(I) and Zn(II) the limits developed by the phytoassay are equal to the standards.

The results suggest that duckweed is a promising indicator of aquatic toxicity. Duckweed assay should be further explored so that its value can be evaluated when more data are available.