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 shoots of the macrophytes. The results for the herbicides atrazine and linuron were described by nonlinear Freundlich equations, with Freundlich exponents ranging from 0.53 to 0.60. The results for the other compounds showed almost linear sorption isotherms, with Freundlich exponents ranging from 0.9 to 1.1. The highest sorption was measured for chlorpyrifos, with sorption coefficients ranging from 1,660 to 2,150 L/kg. Sorption coefficients for C. globularis tended to be lower than those for the other two macrophytes. Correlation (R2 = 0.80) was found for the relation between the sorption coefficient (K(d)) of six pesticides and their solubility in water (S). The equation log 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