Sorption of nine pesticides to three aquatic macrophytes

The sorption of nine pesticides to the aquatic macrophytes Chara globularis , Elodea nuttallii, and Lemna gibba was studied. A batch equilibrium method was used to study the sorption at five concentration levels to fresh shoot s of the macrophytes. The results for the herbicides atrazine and linuron w ere described by nonlinear Freundlich equations, with Freundlich exponents ranging from 0.53 to 0.60. The results for the other compounds showed almos t linear sorption isotherms, with Freundlich exponents ranging from 0.9 to 1.1. The highest sorption was measured for chlorpyrifos, with sorption coef ficients ranging from 1,660 to 2,150 L/kg. Sorption coefficients for C. glo bularis tended to be lower than those for the other two macrophytes. Correl ation (R-2=0.80) was found for the relation between the sorption coefficien t (K-d) of six pesticides and their solubility in water (S). The equation l og K-d = 3.20 - 0.65 log S can be used for a first estimate of the sorption coefficient of a pesticide to aquatic macrophytes.