Latitudinal Study of the Geochemical and Lipid Biomarkers in Alaskan Arctic Soils

Warming of the Arctic has the potential for immense climatic feedbacks due to impacts on microbial respiration affecting soil carbon storage and consumption. The chemical composition of soil carries the signature of the source material and the subsequent processes that it underwent to their point of analysis. Therefore, by reading the molecular messages of the soil, we can glean more information about the fate of Arctic soils. In August 2013, we collected a series of active layer soil cores along a north-south transect from Deadhorse to just south of the Brooks Range to study the carbon accumulation and composition during the Holocene. Previously, this transect was shown to have different accumulation rates during the Holocene (Marion and Oechel, 1993). We applied geochemical parameters (total organic carbon and nitrogen, stable carbon and nitrogen isotopes, radiocarbon of bulk soil organic matter) as well as analyzed the lipid biomarkers (alkanes and other markers of degradation). For most cores along the north-south transect, there was a distinct and expected decrease in carbon, nitrogen and alkane concentration with depth. However, with depth there were systematic trends of a series of compounds typically used as biomarkers of organic matter maturity in the ancient rocks. While it is unlikely that these organic matter maturity compounds reflect ancient organic carbon in Arctic soils, we will discuss the compounds that reflect organic matter maturity further as they may be diagnostic of microbial degradation and/or other soil processes.