Chemical Characterization and Source Identification of Beached Oil from Two Areas Along the North-Western Coast of Qatar

Over the years there have been several reports of oil spills affecting particularly the northern coast of Qatar. In most cases, the source of oil spills is not identified. The spilled oils are very resistant to degradation and can affect the coastal ecosystem over many years. Even today, after 24 years, some of the oil that was spilled during the 1991 Gulf War can be found in sand, close to the Al Zubahra UNESCO site. The Maersk Oil Research and Technology Center in Doha (MO-RTC) has established the Oil Fingerprint project in collaboration with the University of Qatar and the University of Copenhagen. One of the objectives of the collaboration is to identify the potential source and origin of oil spills based on their chemical composition. A total of 38 samples were collected. During the sampling campaign it was discovered that the coast was contaminated with highly weathered oil that could originate from the Gulf War era but also with more fresh oil that most likely originates from recent oil spills in the Arabian Gulf. We therefore collected polluted soil samples and contaminated sediments from two main areas along the beach in North-western Qatar. The samples were analysed using gas chromatography - mass spectrometry in selected ion monitoring mode (GC-MS/SIM) and the oil composition was characterized. The likely source of the beached oil was identified by a comparison of diagnostic source ratios by comparing petroleum hydrocarbon fingerprints of steranes and hopanes of the spills against an oil database. The initial chemical fingerprinting based on selected ion chromatograms (SICs) of steranes (m/z 217) and hopanes (m/z 191), were remarkable similar as were the C29-/C30-Hopane ratios between sampling sites. However, a more detailed pixel-based analysis showed significant differences between samples. The process also included an assessment of the physical and biological weathering effects on the oil spills. Petroleum biomarker patterns (steranes and hopanes) are identical for all 14 samples included in this pilot study. The only differences observed were in the relative concentration of LMW and HMW steranes. This could be due to real source oil differences, however, the general weathering patterns indicate that these differences are more likely due to extensive weathering of especially two samples (9-02, 3-02) but also 8-01 and 10-01 shows severe weathering effects. Analysis of alkyl-PAHs provided an overall evaporative weathering degree for the samples. Distinct differences in the isomer patterns were observed for 3- to 4-ring alkyl-PAHs and this cannot be immediately explained as biodegradation. The largest fraction of the samples seems to originate from the same source but other sources are clearly present. A more detailed analysis with normalization to Euclidean norms within six selected SICs revealed more source specific information. In conclusion, the results indicate at least 2-3 different sources on the basis of differences in PAH isomer patterns. This was confirmed by visual inspection of SICs of C1-C3 alkyl-substituted phenanthrene, dibenzothophene, chrysene and pyrene isomers. Apart from the finding that the spills originate from several sources, the evaporation profiles indicated that not all of the spills are crude oils but that some are also heavy fuels. This suggests ongoing bunker flush off the coast of Qatar. These findings are of importance in further bioremediation processes in which, different approaches should be investigated to achieve high efficiency strategies if removal of oil pollutants from AlZubaraa area.qscienc

Solvent Extraction Of Total Petroleum Hydrocarbons From Contaminated Soils In Qatar

The increase of soil and water contamination, caused by oil leakages during transportation and storage of petroleum components, present serious threat to human health and the environment. Total petroleum hydrocarbons (TPH) is a commonly used gross parameter for quantifying environmental contamination that is originated by various petroleum hydrocarbons. The characterization of the petroleum contaminated soils will enable the selection of the most appropriate methods for bioremediation and rehabilitation of theses soils. Qatar's economic boom, based on the hydrocarbon industry, is putting a strain on other scarce resources. Due to the increase of industrial activates; several environmental issues arose in the recent years, putting at risk the natural and cultural resources of Qatar. Soil in Qatar is in general shallow sandy calcareous, overlying rocky bedrock. The available nutrition is poor with salty soil; they are adapted and tolerate different physical and chemical factors. In areas with long history of oil spells, it's important to conduct large-scale study in which oil weathering in the sediments is evaluated in terms of toxicity to the environment. Rehabilitation of lands should be further developed to preserve agricultural soils, and to prevent the spread of harmful molecules and their infiltration into the groundwater and in the food chain. Solvent extraction is a promising technology for degrading polluted soil. Consequently, several solvent has been researched; namely methanol, hexane, dichloromethane and acetone. The solvent mixture [hexane: dichloromethane (50:50)] efficiently extracts the polycyclic aromatic hydrocarbons (PAHs) compounds. The solvent extraction methods are useful to identify the composition of soil contamination which would assist in the treatment and remediation. Accelerated solvent extraction has been applied to extract of wide range of petroleum hydrocarbons, including aliphatic, polycyclic aromatic hydrocarbons (PAHs), phenols, and polychlorinated biphenyls (PCBs), while gas chromatography-mass spectrometry (GC-MS) is used to quantify the hydrocarbon compound in environmental samples. In this study, Total petroleum hydrocarbons was extracted and quantified in several samples collected from aged contaminated sites. The analytical results, indicated that the quantitative determination of the PAH was depended strongly on the sample preparation, and solvents The data collected in this baseline study should be further validated and incorporated with other studies that would guide the future remediation strategies.qscienc

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7