Degradation and adsorption of tebuconazole and tribenuron-methyl in wheat soil, alone and in combination

Abstract

In practice, pesticides are usually simultaneously applied or one after another for crop protection. This often leads to a coexistence of pesticide mixtures in soil. One of the most important processes influencing the behavior of a pesticide in the environment is its degradation and adsorption in soil. Thus, the degradation and adsorption behaviors of tebuconazole (TEB) and tribenuron-methyl (TBM) alone and combined application in wheat soil (pH 7.28) were studied. The concentrations of TEB and TBM in soil were determined using a quick, easy, cheap, efficient, rugged and safe method (QuEChERS) with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). Results showed that TEB has longer half-lives compared with TBM in the tested soils when they were applied individually. The degradation of TEB was markedly affected by concentration and soil microorganisms. In the non-sterilized soil, half-lives of 0.8 and 80 mg kg-1 TEB were 16.4 and 69.3 d, respectively, and half-lives of 0.8 and 80 mg kg-1 TEB were 20.4 and 73.5 d in the sterilized soil, respectively. The degradation of TBM was not affected by TEB in both soils; however, TBM could reduce the degradation of TEB. Compared to TEB alone, the rates of degradation of 80 mg kg-1 TEB in presence of 32 mg kg-1 TBM were reduced 15.9% and 18.2% in non-sterilized and sterilized soils, respectively. Soil adsorption affinity of TEB was significantly higher than TBM. When used combined, adsorption capacity of TEB was not affected by TBM. However, the adsorption of TBM was obviously inhibited in presence of TEB.