Award: OCE-2000127

Wildfires represent one of the defining processes in Earth?s environmental system, with profound implications that extend from local to global scales. One of the by-products left behind after wildfires is pyrogenic (i.e., fire-derived) carbon (PyC). PyC has distinct chemical properties that are different from most of the other carbon in the environment. As a result, PyC may play an important role in the carbon cycle; for example, it may be more likely to survive transport in rivers to the ocean, where it can be buried in sediments for long periods of time (from thousands to millions of years). If PyC is well preserved on its journey from the land to the oceans, the PyC in sediments may provide a record of fire activity in the past. These records could provide unique information to test potential links between fires and environmental change, for example associated with changing climate or human activities. Yet the transport of PyC through rivers to the oceans remains to be fully understood, especially whether increases in PyC fire activity on land can be directly connected to increased PyC in ocean sediments. This grant provided rapid response funding with the goal of using the dramatic increase in fire activity in the Amazon Basin in 2019 as a natural experiment to assess how river transport of PyC, and its ultimate burial in offshore sediments, responded to a continental-scale increase in burning. Specifically, the work sought to test the hypothesis that increased fire activity in the Amazon in 2019 and 2020 led to enhanced delivery of PyC to and through the Amazon River system. Key to this research plan was the observation that the area of the Amazon burned in both 2019 and 2020 was over twice the 2009-2018 average. The rapid response funding from this award was critical in enabling the collection of a unique set of samples from the Amazon River beginning in late 2019, to test for the immediate response to the increased burning by also taking advantage of baseline samples collected during the 2010s. The award supported (1) the purchase and installation of new instrumentation (specifically a Ion Chromatography PAD detector) for measurement of levoglucosan, one of the important and chemically distinct components of pyrogenic carbon, at the University of Southern California, (2) the training of a graduate student in the use of this instrumentation and in the science behind PyC, and (3) the collection of samples from the Amazon River in coordination with collaborators in Brazil. Further fieldwork to collect samples from additional sites along the Amazon River was proposed but did not prove possible to implement on the timeframe of the award because of travel restrictions imposed by the COVID-19 pandemic. Nonetheless, the availability of rapid response funding made it possible to collect unique and time-critical samples, and together with the instrumentation supported by this grant, these samples provide the opportunity to use this natural experiment to test for observable delivery of PyC from the land to the oceans following changes in burn area. The grant directly supported one graduate student and led to a new collaboration that is enabling the participation of another PhD student on an upcoming cruise the Amazon mud banks, as part of linking river fluxes to the ocean. Last Modified: 07/08/2022 Submitted by: A Joshua West