Comparison of light absorption and oxidative potential of biodiesel/diesel and chemicals/diesel blends soot particles

Soot particles, mainly coming from fuel combustion, affect climate forcing through absorbing light and also result in adverse human health outcomes. Though biodiesel or additives blending with diesel was considered environmentally friendly, the understanding on absorbing and oxidative capacity of soot emitted from them are still unclear. The water-soluble organic carbon (WSOC) content, surface chemical structure, light absorption and oxidative potential (OPDTT) of soot from biodiesel/diesel and chemicals/diesel blends were investigated utilizing total organic carbon analyzer, X-ray photoelectron spectrometer, ultraviolet–visible spectrophotometry and dithiothreitol (DTT) assay. The differences and correlations between soot properties were statistically analyzed. Chemicals/diesel blends soot owned significantly higher WSOC content, ratio of mass absorbing efficiency (MAE) in 250 and 365 nm (E2/E3), OPDTT, and higher surface carbonyl content. Coconut biodiesel/diesel blends soot contained evidently higher aromatic carbon–oxygen single bond (Ar_C–O) content, and higher MAE365. The individual comparison of biodiesel/diesel blends showed 20% coconut biodiesel blend owned the lowest WSOC, E2/E3 and OPDTT, while highest Ar_C–O and MAE365, representing strongest absorbing properties. Association analysis showed OPDTT was significantly positively correlated with WSOC. Further, the evident negative correlation between MAE365 and OPDTT was observed. Our results showed coconut biodiesel/diesel blends soot induced lower levels of oxidative potential, whereas absorption of light was higher, which have far reaching consequences on climate forcing. Therefore, it is important to evaluate the balance point between light-absorbing properties and oxidative potential, under the wide use of biodiesel.