Mercury (HgT) and Methylmercury (MeHg) contents were determined in the soft edible tissue of the pearl oyster Pinctada radiata (family Pteriidae) collected by scuba diving from the coastal waters of Qatar during April-May 2011. Samples were gathered from Doha and Al-Edd Al-Gharbi representing highly productive sites. Samples were immediately transferred to a closed laboratory on board the research vessel and/or semi-closed section of the speed boat and processed without encountering sample contamination. Oysters were carefully placed in clean plastic zip-lock bags, and stored at -18 °C until freeze dried at QU and/or MoE labs. Trace metal clean techniques were applied for all steps in the sampling, preparation, preservation and analysis. Duplicate samples, spiked samples and Certified Reference Materials (TORT-2, DORM-2) were digested and analyzed multiple times with each batch of samples. The prepared samples were then analyzed in accordance with US-EPA Method 1630 and 1631 within 48 hours of digestion via ethylation, purge and trap (Tenax) pre-concentration, GC separation and AFS detection. HgT analyses were conducted by AULA 254 Automatic Mercury Analyzer (Gold Trap System) with Automatic Sample Digester in QU-ESC laboratories. MeHg analysis was conducted utilizing the BROOKS RAND MERX System with Hg Speciation GC & Pyrolysis. The maximum MeHg concentration detected was 0.284 μg/kg with the average of 0.016 μg/kg showing a 93% recovery for 80 individuals. The maximum HgT concentration was 0.014 μg/g with an average of 0.008 µg/g for the same set of samples with 87% spike recovery. These values were lower than those reported by FDA (average of 0.02 mg/kg) for oysters and mussels for MeHg contents and within the safe chronic exposure limits of 0.3 μg/kg/day for MeHg via oral ingestion. Values of MeHg and HgT concentrations were correlated with the biometric body parameters (length, width, thickness, total and wet weight) of oysters to detect the relation between mercury bioaccumulation in soft edible tissue and organisms age using its size as a proxy. Correlations between Hg concentrations in predator (e.g. Fish) and prey (e.g. Oyster) is useful in determining pathways of mercury transfer in coastal waters. Long-term monitoring of mercury tissue residue in Qatar’s coastal water is crucial in ecological risk assessment. It is recommended that monitoring for Hg should be extended to cover more stations especially near industrial activities. Acknowledgement This study was made possible by a grant from the Qatar National Research Fund under its National Priorities Research Program award number NPRP 09-505-1-081. The abstract contents are solely the responsibility of the authors and do not necessarily represent the official views of the Qatar National Research Fund.


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  • Received: 07 December 2015
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