PRODUCTION, COMPOSITION AND STABILITY OF DISSOLVED BLACK CARBON

Pyrogenic organic matter, also referred to as black carbon (BC), is the product of the incomplete combustion of biomass, occurring under oxygen-limited conditions. Much of past research has examined the characteristics of solid BC, as it represents a significant and long-lived portion of the C cycle and might, when produced from waste biomass and added to soils, be used to mitigate climate change. Some recent research has focused on the export of dissolved black carbon (DBC) from terrestrial to aquatic C pools, as this may impact C cycling as well as environmental and public health. One means of quantifying DBC relies on the use of benzenepolycarboxylic acid (BPCA) molecular markers. However, it is unclear whether BPCA is an accurate and quantitative marker for all BC types. The goal of this study was to understand how DBC quantity and composition, as well as BPCA marker compound production, varied among different types of laboratory-generated BC solids. The composition of series of laboratory-produced pyrogenic solids (biochars) and their respective leachates were examined using a number of bulk and molecular techniques including FTIR, Fourier transform ion cyclotron resonance mass spectrometry (FTICR–MS) and 1– and 2–dimensional NMR. In initial leaching trials, non-charred parent materials released 33–35 mg C/g biomass while low temperature biochars (250–400 ºC) produced only 1.7–7 mg C/g biochar and high temperature BC (525–900 ºC) produced even less at 0.9–2.5 mg C/g biochar. In addition, abiotic and microbially-amended incubations of DBC will be used to better understand its stability in the environment. These experiments shed light on the processes likely to control py-DOM production and export from terrestrial environments as well as the accuracy of methods used to quantify BC and DBC.