Organic matter in the oceans in the form of dissolved black carbon can provide clues about long-term marine carbon cycle patterns, but not much data is available on the geochemical behavior of dissolved black carbon. To unlock more information, a group of scientists processed 86 seawater samples from South China Sea waters during the prevailing southwest monsoon season in southern Asia.

Their study involved isolating dissolved black carbon content and turning it into benzene-polycarboxylic acid in order to measure concentrations of the material at different depths. They discovered a particularly high increase of dissolved black carbon in the Mekong River plume, and they were able to compare carbon input from the Mekong River and atmospheric deposition. The study also helped them understand ocean carbon processing such as photodegradation and to gauge the effectiveness of the benzene-polycarboxylic acid method for measuring dissolved black carbon in ocean water.

Read more: AGU (paywall) / Eos.org | Image credit: NASA Earth Observatory