A 2800-year Siberian ice core record of vanillic acid and p-hydroxybenzoic acid

Abstract:

Biomass burning plays an important role in atmospheric chemistry, the global carbon cycle, and climate. The relationship between burning and climate, and the factors that influence burning emissions over long timescales are not well understood. Therefore, well-dated records are needed to establish a history of biomass burning. In this study we examine the distribution of vanillic (VA) and p-hydroxybenzoic (p-HBA) acids in a Siberian Arctic ice core (Akademii Nauk) covering the past 2800 years. These molecules are produced by the incomplete combustion of lignin, incorporated into atmospheric aerosols, and transported/deposited on ice sheets. VA and p-HBA are generated from the combustion of conifers and grasses, respectively, but are not uniquely derived from these sources. These records should be considered qualitative because a wide range of aerosols is generated from various plant materials under different combustion conditions. The records may also reflect changes in source region locations, transport efficiency, and atmospheric removal prior to deposition.

Ice core samples were analyzed using ion chromatography with electrospray MS/MS detection. VA and p-HBA levels were markedly elevated during three time periods. The most recent of these periods occurred from AD 1450-1720 (140-220 m). The timing of two earlier peaks is less well constrained. They are estimated to be from 300-700 AD (400-500 m) and from 800-400 BC (610-670 m). The similarity between VA and p-HBA suggests that the two compounds are derived from a common source. These three periods of elevated VA and p-HBA are not evident in nitrate, ammonium, or black carbon measurements from the same ice core or with high latitude sedimentary charcoal records from North America, Europe, or eastern Siberia.