Radiocarbon Content of Black Carbon Using the Benzene Polycarboxylic Acid (BPCA) Method.

Black carbon (BC), a bi-product of combustion processes, is ubiquitous in the environment due to the burning of biomass and fossil fuels. Defined by a continuum from char to soot, the structure of BC is unknown. Soot is composed mostly of condensed aromatic rings whereas char has an abundance of oxidized functional groups. We investigate whether the radiocarbon signatures of the various components of the BC structure differ from that of the bulk BC.
Using the benzene polycarboxylic acid (BPCA) method, a chemical oxidation method, we quantify BC as BPCAs and measure the Δ¹⁴C values of the resulting BPCAs. The distribution of BPCAs formed provides information about the chemical structure of the bulk BC material.  BPCA distributions and their Δ¹⁴C values, along with the bulk BC and Δ¹⁴C values will be presented for NIST 1649a, a well-studied urban dust of anthropogenic origin, wood char prepared for the BC Ring Trial, of modern origin and a sample of marine organic matter. Methodological issues related to compound specific radiocarbon analysis of BPCAs will also be discussed.