Monitoring chemical compositional changes of simulated spilled Brazilian oils under tropical climate conditions by multiple analytical techniques

To comprehensively understand the chemical changes over time of spilled oils subject to tropical climate conditions and the active weathering processes, a spill simulation experiment was conducted along 210 days with two distinct Brazilian oils (19 and 24 API) under irradiation and non-irradiation of sunlight. Isoprenoids and nalkanes showed a great loss after 40 days for both oils under the two conditions due to evaporation. Diagnostic ratios of saturated biomarkers showed no changes, whereas the polycyclic aromatic hydrocarbons had a decreasing concentration under both conditions mainly due to evaporation. Furthermore, oxygenated polar compounds produced by photooxidation were investigated by ESI(-) FT-ICR MS and showed changes only for the oils exposed to sunlight irradiation. Based on the observed polar compositional changes, new parameters are suggested using heteroatom classes to estimate oil spill time under tropical conditions: NO3/NO2; NO3/(NO + NO2); Sigma NOx/N-1; (O-4 + O-3)/(O-2 + O-1); O-4/(O-2 + O-1); and O-3/O-2.

Automated summary

In a spill simulation experiment lasting 210 days using two Brazilian oils subjected to tropical conditions, it was found that isoprenoids and nalkanes experienced significant loss due to evaporation after 40 days. Polycyclic aromatic hydrocarbons also showed a decrease in concentration, mainly attributed to evaporation. Additionally, exposure to sunlight led to the production of oxygenated polar compounds, prompting the suggestion of new parameters for estimating oil spill time under tropical conditions.