Question 13 OSE01 - Chief Engineer - OSV

The Correct Answer is C **Explanation for Option C (Sulfur):** Sulfur is a soluble contaminant naturally present in crude oil, and thus in diesel fuels (such as Marine Gas Oil - MGO, or Marine Diesel Oil - MDO) used in offshore supply vessels. When sulfur-containing fuel is burned, it forms sulfur oxides ($\text{SO}_\text{x}$), which are major air pollutants contributing to acid rain and respiratory issues. To limit these atmospheric emissions to acceptable levels, international regulations (like those set by the IMO Marpol Annex VI) and regional/local rules strictly mandate maximum permissible sulfur content (expressed as % mass/mass) in marine fuels, especially when operating in designated Emission Control Areas (ECAs). Therefore, sulfur content is a critical specification directly linked to limiting atmospheric emissions. **Why the other options are incorrect:** * **A) Total sediment:** Total sediment refers to insoluble, non-combustible material (such as rust, dirt, and degradation products) that can cause engine wear, filter blockage, and poor combustion, but it is not typically regulated as a major atmospheric contaminant (like $\text{SO}_\text{x}$ or $\text{NO}_\text{x}$) contributing to widespread air quality issues. * **B) Asphaltenes:** Asphaltenes are large hydrocarbon molecules present in residual and heavier distillate fuels. While they contribute to the fuel's physical properties and can affect combustion efficiency, they are primarily measured to ensure fuel stability and adequate burning characteristics (i.e., avoiding excessive carbonaceous deposits), not primarily as a regulated atmospheric emission contaminant like sulfur. * **D) Water:** Water is an undesirable contaminant because it reduces the fuel's energy content, can cause microbial growth, and may lead to damage in fuel injection systems, but it does not produce regulated atmospheric emissions (like $\text{SO}_\text{x}$ or $\text{NO}_\text{x}$) upon combustion in the manner sulfur does.