Evaluation and implementation of methods for quantifying organic and inorganic components of biochar alkalinity.

摘要

When used as a soil amendment, biochar has the potential to increase soil pH and provide several other benefits to soil quality, but scientific understanding of the mechanisms by which biochar influences the acid-base chemistry of soil is incomplete. Integral to this understanding is knowledge of the components of biochar alkalinity. However, methods for quantifying the components of biochar alkalinity vary greatly among biochar studies. Components of biochar alkalinity have been shown to include organic functional groups, carbonates, and other inorganic alkalis. Unfortunately, studies quantifying all three of these components are lacking, and of the studies that quantify at least one component, different methods are used from study to study. One method of particular concern is the Boehm titration, which was originally developed for quantifying reactive organic functional groups of carbon blacks and activated carbons in discrete pKa ranges (Boehm, 1994; Boehm, 2002). Given that the Boehm titration has only been standardized for use with carbon black and that the differences between biochar and carbon blacks are numerous, the Boehm titration may require modification before it can be relied upon to quantify reactive organic functional groups in biochars (Goertzen et al., 2010). Therefore, three modifications of the Boehm titration method for measuring functional group concentrations were evaluated, and a suite of methods was used to quantify the organic and inorganic components of biochar's alkalinity.