Effects of temperature on sorption-desorption processes of imidacloprid in soils of Croatian coastal regions

J Environ Sci Health B. 2012 Sep;47(8):779-94. doi: 10.1080/03601234.2012.676413.

Abstract

Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equations, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were non-linear and may be classified as L-type, suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the K( sor ) ( F ) values decreased for all the tested soils as the temperature increased, indicating that the temperature strongly influences the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous processes. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and partitioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature-dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature treatments existed, and it was more pronounced at 20°C in the soils with higher OC content. The study results emphasize the importance of thermodynamic parameters in controlling soil pesticide mobility in different geographical locations, seasons and greenhouse conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Croatia
  • Herbicides / chemistry*
  • Imidazoles / chemistry*
  • Kinetics
  • Neonicotinoids
  • Nitro Compounds / chemistry*
  • Soil Pollutants / chemistry*
  • Temperature

Substances

  • Herbicides
  • Imidazoles
  • Neonicotinoids
  • Nitro Compounds
  • Soil Pollutants
  • imidacloprid