Characterizations and comparison of low sulfur fuel oils compliant with 2020 global sulfur cap regulation for international shipping

Do distributions of diamondoid hydrocarbons accumulated in oil-contaminated fish tissues help to identify the sources of oil?

Identifying the sources of environmental oil contamination can be challenging, especially for oil in motile organisms such as fish. Lipophilic hydrocarbons from oil can bioaccumulate in fish adipose tissue and potentially provide a forensic "fingerprint" of the original oil. Herein, diamondoid hydrocarbon distributions were employed to provide such fingerprints. Indices produced from diamondoids were used to compare extracts from fish adipose tissues and the crude and fuel oils to which the fish were exposed under laboratory conditions. A suite of 20 diamondoids was found to have bioaccumulated in the dietary-exposed fish. Cross-plots of indices between fish and exposure oils were close to the ideal 1:1 relationship. Comparisons with diamondoid distributions of non-exposure oils produced overall, but not exclusively, weaker correlations. Linear Discriminatory Analysis on a combined set of 15 diamondoid and bicyclane molecular ratios was able to identify the exposure oils, so a use of both compound classes is preferable.

Emission characteristics of naphthalene from ship exhausts under global sulfur cap

The global sulfur limit regulation mandates the use of 0.5 % low sulfur fuel oil (LSFO) to reduce emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and particulate matter (PM). However, the addition of naphthalene (Nap) to LSFO to stabilize its quality has led to an increase in polycyclic aromatic hydrocarbons (PAHs), with Nap being the main pollutant. This study investigates the effects of Nap in ship exhaust by analyzing the emission concentrations of volatile organic compounds (VOCs) and Nap in the exhaust of 16 ships, including 2 container ships, 6 bulk carriers, 1 tanker, 2 ferries, 3 fishing vessels, and 2 harbor crafts, based on USEPA method TO-15A. The results show that the percentage of Nap emissions in the exhaust gases of the 16 ship engines ranged from 77 % to 97 % of the total volatile organic compound (TVOC). The Nap concentration in the exhaust of fishing vessels, tanker, and harbor craft exceeded the occupational exposure limit of 50,000 μg/m3, with fishing vessels having the highest TVOC and Nap concentrations. The enhanced Nap emission in the air degrades air quality in port cities and poses an obvious potential public health risk. While the benefits of the global sulfur cap are being secured, additional efforts should be made to reduce the undetected side effects. Alternative stabilizers of LSFO should be considered, or Nap emission control should be boosted to mitigate the potential negative impact on harbor air quality.

Applicability of oil adsorption pads based on properties of very-low sulfur fuel oil: Implications for oil spill remediation in a marine environment

Given the urgent need for continuous and diverse research on marine fuel oils, this study investigated the effects of the properties of fuel oil on its adsorption to adsorbent materials. Very low-sulfur fuel oil (VLSFO), which is increasingly being utilized in vessels, was tested to simulate adsorption from seawater at temperatures of 1, 15, and 25 °C. Temperature minimally affected the adsorbed amount of low-viscosity VLSFOs and high-sulfur fuel oils. Conversely, the amount of high-viscosity VLSFO adsorbed decreased sharply at 1 and 15 °C. The viscosity, pour point, aromatics, asphaltenes, and wax contents of fuel oils determined the amounts adsorbed on an adsorbent. Therefore, at low sea surface temperatures associated with VLSFO spills, adsorption may be challenging. These findings highlight the need to improve fuel oil quality to accommodate spills in the marine environment.

Analysis of sulfur compounds for crude oil fingerprinting using gas chromatography with sulfur chemiluminescence detector

Oil spills are a severe problem worldwide due to the resulting damage to marine and coastal ecosystems and to local economies. Identification of the source of spilled oils can be challenging, especially if the oils have undergone severe weathering. Due to their high durability, biomarker compounds (e.g. hopanes, steranes) are widely used for oil fingerprinting. Some sulfur-containing heterocyclic compounds e.g. alkylated dibenzothiophenes are also considered to be highly resistant. In this study, the use of Gas Chromatography with Sulfur Chemiluminescence Detection was investigated as a means of oil fingerprinting using the distribution the sulfur compounds in five different fresh and weathered crude oils. Chemometric analysis was also performed. The results indicate that the sulfur compounds distribution is unique for each crude oil. The distributions of the heavy sulfur compounds (i.e., C2DBTs and C3DBTs) are unchanged after weathering. Therefore, the GC-SCD technique can be considered to support the oil spill identification.

Fish Fingerprinting: Identifying Crude Oil Pollutants using Bicyclic Sesquiterpanes (Bicyclanes) in the Tissues of Exposed Fish

In the present study, we investigated the possibility of identifying the source oils of exposed fish using ratios of bicyclic sesquiterpane (bicyclane) chemical biomarkers. In the event of an oil spill, identification of source oil(s) for assessment, or for litigation purposes, typically uses diagnostic ratios of chemical biomarkers to produce characteristic oil "fingerprints." Although this has been applied in identifying oil residues in sediments, water, and sessile filtering organisms, so far as we are aware this has never been successfully demonstrated for oil-exposed fish. In a 35-day laboratory trial, juvenile Lates calcarifer (barramundi or Asian seabass) were exposed, via the diet (1% w/w), to either a heavy fuel oil or to Montara, an Australian medium crude oil. Two-dimensional gas chromatography with high-resolution mass spectrometry and gas chromatography-mass spectrometry were then used to measure selected ratios of the bicyclanes to examine whether the ratios were statistically reproducibly conserved in the fish tissues. Six diagnostic bicyclane ratios showed high correlation (r²  > 0.98) with those of each of the two source oils. A linear discriminatory analysis model showed that nine different petroleum products could be reproducibly discriminated using these bicyclane ratios. The model was then used to correctly identify the bicyclane profiles of each of the two exposure oils in the adipose tissue extracts of each of the 18 fish fed oil-enriched diets. From our initial study, bicyclane biomarkers appear to show good potential for providing reliable forensic fingerprints of the sources of oil contamination of exposed fish. Further research is needed to investigate the minimum exposure times required for bicyclane bioaccumulation to achieve detectable concentrations in fish adipose tissues and to determine bicyclane depuration rates once exposure to oil has ceased. Environ Toxicol Chem 2023;42:7-18. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.