# Ship Route Oil Spill Modeling: A Case Study of the Northeast Brazil Event, 2019
## 3 Results  
Figure 3 displays the latitudinal distribution of oil arrival on the coast at the end of the simulation in each of the 31 experiments representing spillage from ships en route. These experiments consider the volume of two internal tanks and the duration of emptying based on an oil pumping rate of 4000 m\({}^{3}\) h\({}^{-1}\). The latitudinal distribution of oil arrival on the coast showed that none of the VLCC-type vessels (experiments 23 to 31) exhibited a spatial pattern like the one observed, where the maximum (75 th) and minimum (25 th) percentiles did not coincide with the oil arrival according to IBAMA data, presenting a predominant dispersion toward the northern coast; thus, in these scenarios, the major concentration of oil touch occurred between 12\({}^{\circ}\) S and 5\({}^{\circ}\) S, unlike what was observed (between 16\({}^{\circ}\) S and 10\({}^{\circ}\) S). However, some experiments showed this similarity between the percentiles and the distribution deviation, e.g., experiments 2 (Panamax), 9 and 11 (Aframax), and 17 and 21 (Suezmax). Therefore, we chose these experiments for more detailed analysis. The results of the minimum oil arrival time on the coast, the date of arrival, and the maximum quantity of oil on the coast in each experiment are shown in Table 5. As highlighted, the experiments conducted on the VLCC ship routes do not resemble the oil arrival on the coast, dispersing mainly toward the northern coast, and they have a low total oil arrival quantity (average of 416.4 tons), which is inconsistent with the observed data. The experiments highlighted with similarity in the latitudinal distribution of arrival on the coast (2, 9, 11, 17, and 21, bold in Table 5) do not correspond to the total quantity, location, and arrival date from the IBAMA observations, demonstrating that the analysis of the latitudinal distribution of oil arrival on the coast in isolation cannot serve as a reference for choosing an experiment that more faithfully represents the actual event. Additionally, we also sought correspondence between the total oil arrival on the coast (approximately 5000 tons) and a temporal window of the first arrival near the end of August and the beginning of September in the region south of the state of Paraiba. Experiment 22 (dashed green line in Figure 1) stood out as the only one with a high total quantity of oil on the coast (1458.5 tons) and the first touch day between late August and early September (29/08), although the latitudinal oil distribution is not consistent. In this experiment, the latitude of the first touch on the coast was 7\({}^{\circ}\)25\({}^{\prime}\) S, consistent with the latitude of the first sighting location (7\({}^{\circ}\)33\({}^{\prime}\) S); however, the total quantity on the coast does not match the oil collected in situ in early December 2019. In this experiment, the considered vessel was of the Suezmax type, and the total volume spilled was increased to three internal tanks (42,753 m\({}^{3}\)), resulting in a maximum total quantity of oil on the coast of 4686.1 tons, a value closer to the observed data, but without a significant increase in the latitudinal oil distribution. Figure 3: Results of the boxplot experiments for Panamax, Aframax, Suezmax, and VLCC ships. The boxplot of the observed scenario of ashore oil is highlighted in cyan. Figure 4 displays the outcome of experiment 22 regarding the total oil concentration in the water column (<100 m) on 29 August and its arrival on the coast (cyan dots), as well as the main dispersion directions to the north and south and the coastal arrival locations after the simulation period on 2 December 2019 (black dots). The behavior of the oil and weathering processes is highlighted in Figure 5. It was observed that, after the sixth day, the oil exhibited a higher concentration in the water column than on the surface, indicating a sinking process possibly related to the physicochemical transformation of the oil in seawater, while coastal arrival and oil sedimentation began on the seventeenth day.