CORRELATION BETWEEN DROUGHT AND BLACK CARBON SEQUESTRATION IN LAKE BOSUMTWI, GHANA SEDIMENTS

Wildfires frequency may increase in the future as a result of impending global warming. The increased occurrence of these fires may add carbon dioxide (CO2) to the atmosphere. However, we have evidence from the Chesapeake Bay which suggests that over geologic time, such wildfires may have led to carbon sequestration and eventual CO2 burial by formation of pyrogenic black carbon (BC). Furthermore, preliminary data suggest that these fires in the Chesapeake Bay were due to climate forcing (i.e. droughts). Based on this preliminary data, we hypothesized the following: 1) periods of drought in the late Holocene are characterized by relatively greater abundances of sedimentary BC from erosional or Aeolian input and 2) such enrichments of BC in the sedimentary record are examples of climate-driven carbon sequestration. An ideal location to test this hypothesis is in Africa, where climate and drought are inextricably linked.

Black carbon is being isolated in two sediment cores isolated from Lake Bosumtwi, Ghana, Africa. The geochronology of these cores was established using 210Pb and 14C. These cores encompass the late Holocene. The BC isolation process in sediments from these cores involved first demineralization using HCl-HF and then oxidation of non-BC organic carbon using potassium dichromate-sulfuric acid for 400h. The residual carbon is operationally defined as BC. Levels of BC in our cores will be related to other proxies of drought to test the hypothesis noted above. If we see a relationship between climate, specifically drought, and enrichments of BC in sediments, then we will test our hypothesis on a broader spatial context.