Antarctic Lakes Preserve Dissolved Remnants Of Black Carbon From Ancient Forest Fires

The researchers have discovered that the ice-covered lakes in Antarctica's McMurdo Dry Valley uphold the thawed fragments of black carbon from ancient wildfires.

The study was published in the American Geophysical Union journal Geophysical Research Letters on June 8, 2016. The study was led by Alia Khan, a lead author of the study and a graduate researcher at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado Boulder and Diane McKnight, the co-author of the study and a professor of Civil, Environmental and Architectural Engineering at CU-Boulder. It was also co-authored by Yan Ding and Rudolf Jaffe of Florida International University.

Khan explained that they go through the long-term history of those lakes and that there are no local forest fires burning in the neighboring areas. With this, they can be more certain that those woody signatures have come over from Africa, South America or Australia, for instance. She further explained that overall, there have been relatively limited direct measurements of dissolved black carbon in the cryosphere due to the problems of sample collection from these remote environments. She added that these are the first they know of from freshwater lakes in Antarctica, according to the American Geophysical Union.

In the study, it reveals that the dissolved black carbon can stay in freshwater and saline surface waters for thousands of years, while conserving the chemical signature of the original source materials. The prehistoric seawaters of the lake bottom waters have preserved the dissolved black carbon with a woody chemical signature. In contrast, the waters are supplemented in black carbon from fossil fuel combustion. The enrichment in anthropogenic black carbon just exists recently based on the samples collected. The distinctions in the chemical composition of dissolved black carbon among the lakes are possible due to biogeochemical processing that includes the sorption on metal oxides and the photochemical degradation.

This study may release information and conclusion on how the black carbon signatures have moved over time and how the dissolved black carbon is carried to the world's oceans and lakes.