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This study proposes a standardization process for the monitoring the level of tar mat contamination in the Arabian Gulf. In the study, we selected target gastropod species and evaluated the ecological and ecotoxicological effects of tar mats on their populations, the bioaccumulation of heavy metals, and these species’ potential as bioindicator taxa for tar mat-associated heavy metals. The study was carried out at two sites on the Qatar coast on shoreline rocks, both of which have areas of tar mat coverage and areas without tar mats. The species selected as representative species for the ecoregion were the endemic Clypeomorus bifasciata persica (Houbrick, 1985) in the intertidal zone and the Echinolittorina arabica (El Assal, 1990) in the supratidal zone. Both are grazers and are niche restricted to hard substrates and daily scraping/grazing on the tar mat deposition zone of the shorelines. The key heavy metal indicators chosen were As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn, and the gastropod species were divided into classes according to their size. Tar mat presence was found to negatively affect both the overall population size of Clypeomorus and different size classes, and lead to high levels of assimilation of heavy metals. Tar mat presence also negatively affected different size classes of Echinolittorina where large sizes were found to be most significantly affected. The results also demonstrated that Cu and Ni are the heavy metals most associated with tar mat contamination of this kind. Overall, our results confirmed that grazer gastropods are good bioindicators of tar mat-associated contaminants in shoreline ecosystems. Our study provides the database on the heavy metal contamination of the proposed target gastropods, and offers information that will be relevant for further monitoring and comparisons among threatened coastal areas in the Arabian Gulf. This research was supported by the Qatar Petroleum through the project of QU (QUEX-ESC-QP-TM-18/19).

The current study aimed to gauge total mercury (THg) concentration and the environmental geochemical indices in tarmat contaminated sediments and test their presence in targeted coastal species. Layers of hard asphalt-like tarmats and sediment samples were collected from 34 sites along the coast of Qatar. The mean concentration of THg in tarmat-sediment mixture is 89 ± 20 ng·g−1. THg concentration varies significantly between the northern and eastern coasts. Geographically, sampling area were divided into four zones according to the relative closeness with low to serious potential ecological risk index (Er), moderate pollution load index (PLI), moderate Geoaccumulation index (Igeo), and no toxic risk (TRI) trending as Northern (Zones 4, 3) > North-Eastern (Zone 1) > Western (Zone 2) coasts. Three biota classes (Gastropoda, Bivalvia, and Crustacea) were sampled on the tarmat which the hermit crab (Clibanarius signatus) from Ras Rakan island obtained the highest THg (977 ng·g−1) and BSAF (29.70).

Oil residue in the form of tarmat (TM) deposited on the coast of Arabian Gulf countries is a major environmental concern. In this study, the current TM pollution trend along the west coast of Qatar has been assessed and compared with historical deposition trend. The range of TM distribution is 0–104 g m-1 with an average value of 9.25 g m-1. Though the current TM level is thirty-fold lesser than that was found during 1993–1997 (average 290 g m-1), the distribution pattern is similar. The chemical composition and structural characterization of TMs were studied using an ATR-FTIR spectroscopy, which indicated the presence of higher aromatic compounds in the north (N) coast TMs than those found in the northwest (NW) and southwest (SW) coasts. TM of NW coast is highly weathered compared to those found in the N and SW coasts. We found that the ATR-FTIR spectroscopic method is a rapid approach to characterize and study the weathering of TMs without any tedious sample preparation or solvent extraction.

One of the pollutants that affects the coastal environment of Qatar is the vast expanse of oil residue ‘tarmats’ deposited on its beaches. The current study is aimed at gauging the concentration levels of total mercury (THg) in tarmat contaminated sediments and test their presence in selected coastal species. Three biota classes (Gastropoda, Bivalvia, and Crustacea) have been found on the tarmat of Ras Rakan and Umm Tais islands. Layers of hard asphalt-like tarmats and sediments samples were collected from 34 sites, along the coast of Qatar. Moreover, the Biota Sediment Accumulation Factor (BSAF) was calculated for THg through sentinel species. The mean concentrations of THg is 0.089 ± 0.02 μg.g-1. Compared to earlier studies, a relatively higher concentration of THg (0.463 μg.g-1) had been observed.

Oil pollution resulting from natural and anthropogenic activities in the Arabian Gulf as well as oil residue in the form of tarmat (TM) deposited on the coast is a major environmental concern. The spatial distribution, chemical composition and weathering pattern of tarmat along the west coast of Qatar has been assessed based on the TM samples collected from 12 coastal regions. The range of TM distribution is 0–104 g m−1 with an average value of 9.25 g m−1. Though the current TM level is thirty-fold lesser than that was found during 1993–1997 (average 290 g m−1), the distribution pattern is similar. The results of ATR-FTIR spectroscopy indicate that aromatic compounds are higher in the north (N) coast TMs than those found in the northwest (NW) and southwest (SW) coasts, and Carbonyl Index values indicate that TM of NW coast is highly weathered compared to those found in the N and SW coasts. ORS, QU Project (QUEX-ESC-QP-TM-18/19), funded by the Qatar Petroleum.

Tarmat/Oil residue (hereafter ‘TM’) is one of the serious threats to the marine ecosystem due to their toxicity, persistence and bioaccumulation problems. To assess the level of TM contamination and to determine the primary differences in the chemical composition, a sampling campaign was conducted in 12 beaches along the west coast of Qatar. TM contamination ranged from 0 to 104 gm-1 with an average value of 9.25 gm-1. Moreover, all the TM samples were found to be highly weathered, blackish and asphalt-like material. Though the current TM pollution level is thirty-fold lesser than those found during 1993 to 1997, the contamination pattern was similar (i.e. northwestern part was highly contaminated). The distribution of TM along the Qatar coast is as follows: Low tide> high tide> berm line. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to examine the bulk chemical characteristics of the TMs. These bulk chemical characteristics have revealed several features unique to different types of TM samples.

© 2018 Elsevier B.V. Beaches of Ras Rakan Island, located off the northern tip of Qatar, are extensively contaminated by highly weathered tarmat deposits. The focus of this study is to determine the possible source of the contamination and complete a preliminary assessment of its potential environmental impacts. The field data collected at this site indicated that the tarmat residues contained highly weathered, black, asphalt-like material and the contamination problem was widespread. Based on these field observations, the following two hypotheses were formulated: (1) the tarmats must have formed from the residual oil deposited by a relatively large, regional-scale oil spill event, and (2) the oil spill must be relatively old. As part of this study, we collected tarmat residues from several beaches located along the northern region of Qatar Peninsula. We found the hopane fingerprints of these tarmat samples were identical to the fingerprints of the samples collected from Ras Rakan Island. These results together with our physical field observational data validated our hypothesis that the oil spill should have been a regional-scale event. Furthermore, we compared the measured hopane fingerprints of our field samples with fingerprints of reference crude oils from Qatar, Saudi Arabia, and Basrah (located close to Kuwait border), and with the literature-derived hopane fingerprints of Kuwaiti and Iranian crude oils. This analysis indicated that the hopane fingerprints of the tarmat samples closely matched the Kuwaiti and Basrah crude oil fingerprints. Since there were no known oil spills of Basrah crude in this region, the highly weathered, asphalt-looking tarmats should have most likely formed from the 1991 Gulf War oil spill, an old oil spill. The concentrations of parent and alkylated PAHs in the tarmat samples were also quantified to provide a preliminary assessment of potential environmental risks posed by these tarmats to Qatar's coastal ecosystem.