Adsorption, degradation and mobility of carbendazim in profiles of Polish mineral soils

Abstract

Herein, we report the results of a study aimed at estimating the potential of carbendazim for translocation into groundwater and its retention in 27 profiles of the most common Polish arable soils, including Arenosols (AR) formed from sand, Luvisols (LV) formed from loamy sand or loam and Luvisols or Cambisols (LV&CM) formed from loess or loess-like formations. The adsorption of carbendazim was characterized by very high variability because the distribution coefficients were in the range of 0.86–16.71mLg−1 for AR, 1.92–184.41mLg−1 for LV and 0.65–57.11mLg−1 for the LV&CM profiles. The effectiveness of desorption from the soil using 0.01M CaCl2 was in the range of 35.7–87.0%, 9.5–76.7% and 22.5–75.5% for the AR, LV and LV&CM profiles, respectively. The obtained half-lives for the selected soil profiles, which were recalculated at 10kPa and 20°C, were in the range of 13.3–39.7d in the Ap horizon and increased to 368d down the soil profile. A comparison of the horizons from the same depth indicated that the degradation rate was the highest in soils with the highest microbial activity and pH. The simulations using FOCUS PELMO indicated that carbendazim was retained in the Ap horizon, and its concentration in groundwater at a depth of 1m was not expected to exceed the European Union contamination limit. The nonlinear regression modeling studies of the pH-dependent adsorption of this fungicide have shown that it is well described in typical arable soils assuming that the protonated form of carbendazim adsorbs on clay and the neutral form adsorbs onto organic matter. In sandy soils with a low pH and low content of organic matter, the adsorption of carbendazim cations onto the sand should also be incorporated into the model.