Surface‐Facilitated Chemical Degradation of Tetraphenylboron in Soil

Laboratory studies were conducted to examine the surface‐promoted degradation of tetraphenylboron (TPB) in soil. The results indicated that TPB degrades rapidly in soil and that the processes involved are predominately abiotic reactions. The initial products of degradation of TPB are diphenylborinic acid (DPBA) and biphenyl. A portion of the DPBA produced subsequently degrades to produce boric acid. However, only about 20% of the total B added initially to the soil as TPB was accounted for by the measured species at the end of the experiment. Most of the remaining B appears to be present in moderately stable organic compounds. Comparison of the degradation rates in different soils indicated that the rates in the surface soil were somewhat higher than in the subsoil. The only measured characteristic of these soils that follows a corresponding trend is soil organic matter content. Additional experiments indicated that rates of the initial reaction are inversely related to soil moisture content. Observed reaction products indicate that the initial step in the degradation process is a two‐step oxidation at Lewis acid sites associated with soil component surfaces.