Lindane sorption and desorption behaviour on sediment organic matter

Abstract

The work is concerned with the sorption and desorption behaviours of lindane on four humic acid fractions (HAs) and two humin fractions, sequentially extracted from Ludas Lake sediment. All sorption isotherms fitted to the Freundlich model were nonlinear. The isotherm linearity increased from 0.757 for the first extracted HA to 0.944 for the ninth HA, showing a positive correlation with the atomic H/C ratio, while a negative correlation between the sorption coefficient and aliphaticity of the isolated HAs was observed. It was shown that the sorption processes may be strongly influenced by the physical conformation of and accessibility to sediment organic matter (SOM), as demonstrated by the high K oc and low n values of the humin samples. Despite exhibiting the most nonlinear sorption isotherms, humin samples did not show a pronounced sorption-desorption hysteresis, while the most significant hysteresis was observed for the three HA samples. These results support the hypothesis that the aromatic domains in SOM influence strongly the sorption and desorption behaviour of lindane. The findings obtained in this study may be helpful in understanding the distribution, transport and fate of lindane in soils and sediments.