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  1. Theng TL, Mohamed CA
    J Environ Radioact, 2005;80(3):273-86.
    PMID: 15725503
    Natural radionuclides, such as (210)Po and (210)Pb were measured in the water samples collected from six stations at Kuala Selangor, Malaysia. Results for (210)Po and (210)Pb in dissolved and particulate phases have showed the difference in distribution and chemical behavior. The fluctuation activities of (210)Po and (210)Pb depend on wave action, geology and degree of fresh water input occurring at study areas and probably due to different sampling dates. The distribution coefficient, K(d), values of (210)Po and (210)Pb ranged from 2.0 x 10(3)lg(-1) to 265.15 x 10(5)lg(-1), and from 3.0 x 10(3)lg(-1) to 558.16 x 10(5)lg(-1), respectively. High K(d) values of (210)Po and (210)Pb indicated that a strong adsorption of (210)Po and (210)Pb onto suspended particles, and the sinking of both nuclides on the seabed at study locations were controlled by the characteristics of suspended particles.
  2. Sabuti AA, Mohamed CA
    Environ Sci Pollut Res Int, 2016 Sep;23(18):18451-65.
    PMID: 27287490 DOI: 10.1007/s11356-016-7023-4
    Concentration activities of (210)Pb and (210)Po in the PM10 were determined to discuss their distribution and chemical behavior in relation to meteorological parameters especially in air mass transport during monsoon events. Marine aerosol samples were collected between January 2009 and December 2010 at the coastal region of Mersing, which is located in the southern South China Sea and is about 160 km northeast of Johor Bahru, as part of the atmosphere-ocean interaction program in Malaysia. About 47 PM10 samples were collected using the Sierra-Andersen model 1200 PM10 sampler over a 2-year sampling campaign between January 2009 and December 2010. Samples were processed using acid digestion sequential extraction techniques to analyze various fractions such as Fe and Mn oxides, organic matter, and residual fractions. While, (210)Pb and (210)Po activities were measured with the Gross Alpha/Beta Counting System model XLB-5 Tennelec® Series 5 and the Alpha Spectrometry (model Alpha Analyst Spectroscopy system with a silicon-surface barrier detector), respectively. The distribution activities of (210)Pb and (210)Po in the PM10 samples were varied from 162 to 881 μBq/m(3) with mean value of 347 ± 170 μBq/m(3) and from 85 to 1009 μBq/m(3) with mean value of 318 ± 202 μBq/m(3), respectively. The analysis showed that (210)Po activity in our samples lies in a border and higher range than global distribution values due to contributions from external sources injected to the atmosphere. The speciation of (210)Pb and (210)Po in marine aerosol corresponds to transboundary haze; e.g., biomass burning especially forest fires and long-range air mass transport of terrestrial dust has enriched concentrations of particle mass in the local atmosphere. The monsoon seems to play an important role in transporting terrestrial dust from Indo-China and northern Asia especially during the northeast monsoon, as well as biogenic pollutants originating from Sumatra and the southern ASEAN region during southwest monsoon events.
  3. Alam L, Mohamed CA
    Environ Health, 2011 May 20;10:43.
    PMID: 21595985 DOI: 10.1186/1476-069X-10-43
    BACKGROUND: Po²¹⁰ can be accumulated in various environmental materials, including marine organisms, and contributes to the dose of natural radiation in seafood. The concentration of this radionuclide in the marine environment can be influenced by the operation of a coal burning power plant but existing studies regarding this issue are not well documented. Therefore, the aim of this study was to estimate the Po²¹⁰ concentration level in marine organisms from the coastal area of Kapar, Malaysia which is very near to a coal burning power plant station and to assess its impact on seafood consumers.

    METHODS: Concentration of Po²¹⁰ was determined in the edible muscle of seafood and water from the coastal area of Kapar, Malaysia using radiochemical separation and the Alpha Spectrometry technique.

    RESULTS: The activities of Po²¹⁰ in the dissolved phase of water samples ranged between 0.51 ± 0.21 and 0.71 ± 0.24 mBql⁻¹ whereas the particulate phase registered a range of 50.34 ± 11.40 to 72.07 ± 21.20 Bqkg⁻¹. The ranges of Po²¹⁰ activities in the organism samples were 4.4 ± 0.12 to 6.4 ± 0.95 Bqkg⁻¹ dry wt in fish (Arius maculatus), 45.7 ± 0.86 to 54.4 ± 1.58 Bqkg⁻¹ dry wt in shrimp (Penaeus merguiensis) and 104.3 ± 3.44 to 293.8 ± 10.04 Bqkg⁻¹ dry wt in cockle (Anadara granosa). The variation of Po²¹⁰ in organisms is dependent on the mode of their life style, ambient water concentration and seasonal changes. The concentration factors calculated for fish and molluscs were higher than the recommended values by the IAEA. An assessment of daily intake and received dose due to the consumption of seafood was also carried out and found to be 2083.85 mBqday⁻¹person⁻¹ and 249.30 μSvyr⁻¹ respectively. These values are comparatively higher than reported values in other countries. Moreover, the transformation of Po²¹⁰ in the human body was calculated and revealed that a considerable amount of Po²¹⁰ can be absorbed in the internal organs. The calculated values of life time mortality and morbidity cancer risks were 24.8 × 10⁻⁴ and 34 × 10⁻⁴ respectively which also exceeded the recommended limits set by the ICRP.

    CONCLUSIONS: The findings of this present study can be used to evaluate the safety dose uptake level of seafood as well as to monitor environmental health. However, as the calculated dose and cancer risks were found to cross the limit of safety, finding a realistic way to moderate the risk is imperative.

  4. Sarimin AS, Ghaffar MA, Mohamed CA
    Pak J Biol Sci, 2009 Feb 01;12(3):231-8.
    PMID: 19579951
    A study on elemental composition in the otolith of giant mudskipper, Periophthalmodon schlosseri, was done from June to October 2003. Specimens were obtained from the mangrove areas of Kuala Selangor, Sepang and Melaka in the west coast of Peninsular Malaysia. A total of 70 sagitta otoliths were analyzed to detect variation of Sr, Ba and Mg, replacing the natural chemical composition of the otolith, which is the calcium carbonate (CaCO3). The average ratio of Sr:Ca was 0.11 x 10(-4), Ba:Ca was 5.7 x 10(-3) and Mg:Ca was 0.2 x 10(-3). Strong correlation (R > 0.8) between fish body size and otolith weight ofmudskipper (p < 0.01) also found during this study.
  5. Chandru K, Zakaria MP, Anita S, Shahbazi A, Sakari M, Bahry PS, et al.
    Mar Pollut Bull, 2008 May;56(5):950-62.
    PMID: 18328505 DOI: 10.1016/j.marpolbul.2008.01.028
    The East Coast of Peninsular Malaysia faces the South China Sea and is vulnerable to oil pollution because of intense petroleum production activities in the area. The South China Sea is also a favored route for supertankers carrying crude oil to the Far East. Consequently, oil spills can occur, causing pollution and contamination in the surrounding areas. Residual oil spills stranded on coastal beaches usually end up as tar-balls. Elucidating the sources of tar-balls using a molecular marker approach is essential in assessing environmental impacts and perhaps settling legal liabilities for affected parties. This study utilizes a multimodal molecular marker approach through the use of diagnostic ratios of alkanes, hopanes, and polycyclic aromatic hydrocarbons (PAHs) to determine the source, distribution and weathering of tar-balls. Hopane ratios (e.g., C29/C30, and summation C31-C35/C30 ratios) were used to identify the sources of tar-balls. The weathering effects were distinguished by using alkanes, namely the unresolved complex mixture (UCM) and low molecular weight/high molecular weight (L/H) ratios. Similarly, PAHs were also used for the determination of weathering processes undergone by the tar-balls. This multimodal molecular marker gave a very strong indication of the sources of tar-balls in this study. For example, 16 out of 17 samples originated from South East Asian Crude Oil (SEACO) with one sample from Merang, Terengganu originating from North Sea Oil (Troll). The TRME-2 sample may have come from a supertanker's ballast water discharge. The second possibility is that the tar-ball may have been transported via oceanographic currents. All 'weathered' sample characterizations were based on the presence of UCM and other ratios. The multimodal molecular marker approach applied in this study has enabled us to partially understand the transport behavior of tar-balls in the marine environment and has revealed insights into the weathering process of tar-balls.
  6. Roslan RN, Hanif NM, Othman MR, Azmi WN, Yan XX, Ali MM, et al.
    Mar Pollut Bull, 2010 Sep;60(9):1584-90.
    PMID: 20451220 DOI: 10.1016/j.marpolbul.2010.04.004
    A study was done to determine the concentrations of surfactants on the sea-surface microlayer and in atmospheric aerosols in several coastal areas around the Malaysian peninsula. The concentrations of surfactants from the sea-surface microlayer (collected using rotation drum) and from aerosols (collected using HVS) were analyzed as methylene blue active substances and disulphine blue active substances through the colorimetric method using a UV-vis spectrophotometer. The results of this study showed that the average concentrations of surfactants in the sea-surface microlayer ranged between undetected and 0.36+/-0.34 micromol L(-1) for MBAS and between 0.11+/-0.02 and 0.21+/-0.13 micromol L(-1) for DBAS. The contribution of surfactants from the sea-surface microlayer to the composition of surfactants in atmospheric aerosols appears to be very minimal and more dominant in fine mode aerosols.
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