Online quantification and compound‐specific stable isotopic analysis of black carbon in environmental matrices via liquid chromatography‐isotope ratio mass spectrometry

Abstract

Black carbon (BC) is derived from the burning of biomass, a considerable portion of organic matter across terrestrial and marine ecosystems, and a major contributor to global carbon cycles. The benzenepolycarboxylic acid method, which converts condensed aromatic BC structures to molecular markers (BPCAs), has been widely adopted for environmental BC assessments. We present a novel analytical method for the online separation, quantification, and determination of compound‐specific stable carbon isotopes of individual BPCAs via high performance liquid chromatography‐stable carbon isotope ratio mass spectrometry (HPLC‐C‐IRMS). To assess δ13C values of environmental BC, the HPLC‐C‐IRMS method was applied to a variety of samples (soil, char, aerosol, and dissolved organic matter). The method reliably measured amounts and δ13C values of benzenepentacarboxylic acid (B5CA) and mellitic acid (B6CA) over a range of 8.3–130 μmol‐C of organic matter oxidized. BPCA‐specific δ13C values deviated from bulk OC δ13C values for different sample types. However, the stable carbon isotopic composition of B5CA and B6CA was found to be generally correlated with that of bulk organic carbon. The stable isotopic compositions of environmental samples covered a wide dynamic range, indicating BC‐specific δ13C values will be useful for tracking BC sources and processing. For instance, the BPCAs derived from marine dissolved organic matter (DOM) were enriched in 13C relative to BPCAs from riverine DOM, suggesting rivers are not the only source of dissolved black carbon to the oceans.

Hydrological Controls on the Seasonal Variability of Dissolved and Particulate Black Carbon in the Altamaha River, GA

“…Thus, while PBC mobilized during the initial high‐intensity rain events cannot be conclusively linked to fossil fuels alone, sources are likely a mix of both biomass burning and fossil fuel‐derived PBC, similar to that observed in Chinese rivers (Wang et al, ). Thus, the use of stable isotopes in future studies would greatly assist in identifying the hydrological controls on PBC sources in this system (Wagner, Brands, et al, ).…”

“…Thus, a more complete understanding of BC mobilization with seasonal hydrology, and potential linkages between DBC and PBC, is critical for elucidating both short and long‐term contributions of riverine BC and its implications for global carbon cycling. While BPCA ratios have been previously linked to BC source, further incorporation of radio‐ and stable isotopic measurements in characterizing individual BPCA components would provide important information relating seasonality to BC sources and export from fluvial systems (Coppola et al, ; Hanke et al, ; Wagner, Brands, et al, ).…”

Online wet oxidation/isotope ratio mass spectrometry method for determination of stable carbon isotope ratios of water‐soluble organic carbon in particulate matter

“…All the organic compounds are oxidized to CO 2 by thermally activated peroxodisulfate, as shown in Equation for ethanol: The generated CO 2 is separated from the liquid by means of a membrane and is transported by a carrier gas to the IRMS inlet. Recently, this LC/IRMS method has been used to determine δ 13 C values for various compounds, including sugars, amino acids, alcohols, pesticides, and black carbon . However, LC/IRMS has not been widely used to determine δ 13 C values for environmental field samples.…”

“…Recently, this LC/IRMS method has been used to determine δ 13 C values for various compounds, including sugars, [24][25][26] amino acids, 27,28 alcohols, [29][30][31] pesticides, 32 and black carbon. 33 However, LC/IRMS has not been widely used to determine δ 13 C values for environmental field samples.…”

Atomic Spectrometry Update – a review of advances in environmental analysis

“…Usefully, software written in R-code was supplied as supplementary material to the paper for other researchers to generate AVEC plots from their own data. Improvements in techniques for the analysis of carbonaceous particles included: a thermal-optical analyser coupled to a quadrupole mass spectrometer for enhanced PM 2.5 speciation capabilities 55 ; better source apportionment by combining data from aerosol mass spectrometry with radiochemical C measurements 56 ; and the compound-specific IRA of black carbon in source apportionment studies using HPLC-IRMS 57 .…”