14 DAY TRIAL // In the majority of climate models, soot – the impure carbon particles that result from the incomplete combustion of a hydrocarbon, such as those in fuel – is considered to be a chemically inert substance that does not react with other compounds in the atmosphere. However, a recent investigation disproves this belief and shows that soot can, in fact, act as an electron “shuttle,” and, in some instances, even as a catalyst. Black carbon (BC) can also be found in soils and sediments, and comes from both human activities and natural causes, such as volcanic eruptions, PhysOrg reports.
The new study was co-authored by University of Delaware scientist Pei Chiu, a Department of Civil and Environmental Engineering professor, and former PhD student Seok-Young Oh, now a postdoctoral research and an assistant professor at the University of Ulsan, in South Korea. The paper, entitled “Graphite and Soot-Mediated Reduction of 2,4-Dinitrotoluene and Hexahydro-1,2,5-trinitro-1,3,5-triazine,” was published in the August 14th online issue of the publication Environmental Science & Technology (ES&T), which publishes papers ahead of print.
“It's commonly assumed that when an organic molecule is bound to a geosorbent such as black carbon, it becomes sequestered and inaccessible. But what we've found, in studying explosives such as DNT and RDX, is that black carbon such as soot and graphite has dual roles, serving as both a sorbent and an electron shuttle,” Chiu explains. Between 10 to the 12th power and 10 to the 13th power grams of soot are emitted into the atmosphere each year, global estimates show, therefore its action is relevant. Its evolution has to be especially analyzed from the standpoint of its interactions with hydrophobic pollutants.
These reactions occur in both aquatic and terrestrial systems, experts say, therefore they have the ability to influence ecosystems virtually anywhere on the planet. “This process needs to be taken into account when the fate of nitro compounds in groundwater and sediment is modeled and when we try to understand their impact on human health and ecology. On the other hand, we can exploit the process in the remediation of sites contaminated with explosives and related chemicals,” the scientist says.
“Additional studies are needed to identify other classes of compounds that can undergo black carbon-mediated transformation, as well as the reductants and medium conditions that are conducive to this process in complex environmental systems,” Chiu concludes. He admits that, until now, only a narrow range of materials has been tested for soot action, but says that the team plans to move ahead with its research in this field.