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Foraminiferal geochemistry applies geochemical elements embedded in foraminiferal calcites through bioaccumulation to interpret and reconstruct past oceanic climate histories. Due to its extensive variability and abundance, foraminifera is the easiest to retrieve and the best indicator of marine productivity and ocean temporal changes. In this review, we discuss the development of foraminiferal geochemistry studies in Southeast Asia, analyzing its current status and potential areas to be developed, namely, the Sunda Shelf. The Sunda Shelf is one of the world’s largest low-latitude shelves, bordered by marginal seas and sensitive to sea-level changes. The shelf response towards changes in ocean salinity affected the isotopic signals in foraminiferal calcites, which can indicate sea-level changes ideally. The Sunda Shelf has the potential to be developed as a study area for eustatic sea-level changes as it is located far from major glaciation centers; hence through this review, we aim to highlight the potential of exploring the application of geochemical elements in foraminifera as an indicator for sea-level changes. To date, literature on foraminiferal geochemistry in this region is very limited, thus inhibiting progress in such studies. A comprehensive summary of past studies in this region is provided to give a general overview of the direction of foraminiferal geochemistry studies and serve as guidelines for future research.

Fluctuation levels of geochemical elements, sediment texture and nutrients were analysed from five surface sediments taken from the northern Malacca Straits. These samples were obtained during the RV Discovery Scientific cruises in September 2017 and April 2018 to assess pollution sources during monsoon events. The results show a higher output of clay and silt revealing that the monsoonal season and cross-shelf inputs affect textural sediment. On the other hand, fluctuations in geochemical concentrations are due to industrialization and urbanization along the Malacca Straits contributed by the local drainage basin. The presence of the monsoon also affects the diffusivity and absorption at the watersediment interface leading to constant fluctuation along the straits. Principal component analysis of the association between geochemical elements sediment texture and nutrients revealed hydrological factors, mobility and accumulation at the sediment interface.

In this study, we explored the heavy metal elements in 42 surface sediments from the Malacca Strait in terms of distribution, controlling factors, environmental quality, and primary sources. An analysis of grain size revealed finer sediments near the coast of Malaysia, which gradually thickened toward offshore. In addition, heavy metal elements were abundantly distributed near the coastal area of Malaysia, with a gradual decrease toward the sea; their content increased within waters close to the Perak estuary. Source analysis of heavy metals showed that Cr, Hg, Zn, Cd, and Cu were mostly derived from natural weathering, and their distribution was significantly influenced by sediment grain size. As and Pb were affected by human activities. The environmental quality assessment results showed that Cu, Cr, Cd, and Zn in our study regions were pollution-free. Pb elements showed low-to-moderate pollution, and Hg showed a certain degree of ecological risk due to its high toxicity coefficient. The content of As elements in surface sediments increased significantly when compared to the background value, with several evaluation methods indicating a high-risk index. According to these findings, the area near the mouth of the Perak River is the most polluted, followed by the surrounding coastal areas.

Radiochemical separation techniques were applied to measure 210Pb radioactivity in samples to determine spatial distribution of total 210Pb radionuclide in surface sediments and water column for the main waters on the Sunda Shelf. The average 210Pb radioactivity level recorded for the Malacca Strait (MS) is significantly higher than that of the southern South China Sea (sSCS); this is attributed to the supply of input from the Andaman Sea in its northern areas, and massive terrestrial processes from bordering land masses. The results reveal that the decreasing trend of total 210Pb in Peninsular Malaysia’s marine sediment starts with the north maritime zone of Malacca Strait (64.28 ± 5.97 Bq/kg) > south maritime zone of Malacca Strait (50.88 ± 6.15 Bq/kg) > east maritime zone of sSCS (41.01 ± 3.07 Bq/kg) > south maritime zone of sSCS (40.78 ± 3.16 Bq/kg). The Kelantan and Pahang Deltas have been identified as two of the main anthropogenic sources of input for total 210Pb in the sSCS with atmospheric transboundary mobilization affecting total 210Pb in the water column. In the Malacca Strait, however, the distribution of total 210Pb might be influenced mainly by in situ processes of the strait’s seafloor and sources origin of sediment. HIGHLIGHTS The Malacca Strait has a significantly higher level of 210Pb radioactivity compared to the southern South China Sea (sSCS), due to input from the Andaman Sea and terrestrial processes from adjacent land masses The decreasing trend of total 210Pb in Peninsular Malaysia’s marine sediment starts with the north maritime zone of Malacca Strait > south maritime zone of Malacca Strait > east maritime zone of sSCS > south maritime zone of sSCS The Kelantan and Pahang Deltas are identified as two of the main anthropogenic sources of input for total 210Pb in the sSCS, while in the sh Strait, the distribution of total 210Pb may be influenced mainly by in situ processes of the strait’s seafloor and sources origin of sediment GRAPHICAL ABSTRACT

Sampling of surface water at seven stations along the Sungai Balok, Pahang was conducted from 2013 to 2015 to investigate the distribution of dissolved rare earth elements (REE) in river systems. The whole concentration of ΣREE in the dissolved phase recorded during this study ranged from 368 to 9121 pmol•L−1 with a mean of 2328 ± 1442 pmol•L−1 that was dominantly influenced by the concentration of Ce ranging from 84 to 3237 pmol•L−1. Similarly, the large ranged value of La/YbN (0.69 - 11.57) might be due to the fluctuating rainfall events during samplings as well as input from lithogenic sources that suggests the influence of monsoon events. The highly significant statistical correlation of Al and Fe (R2 = 0.65; p < 0.01) also suggests the resuspension and mixing of REEs in the water column. However, the lower ratio of Y/Ho < 55 might be due to the large volume of freshwater input especially during the Northeast monsoon (November to March). Therefore, the highest inventories of Ce were during 15th January 2014 and 1st November 2014 with 586.5 pmol•cm−2 and 643.4 pmol•cm−2, accordingly. Subsequently, results showed an increasing flux of Ce occurring in the dissolved phase from November 2013 to January 2014 and November 2014 to January 2015, with 39.14 nmol•cm−2•yr−1 and 59.78 nmol•cm−2•yr−1, respectively.

The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (Igeo), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities.

Prolonged persistence of toxic cadmium (Cd), chromium (Cr) and lead (Pb) in the aquatic environment are due to its nonbiodegradable characteristic. A few studies have reported higher concentrations of these metals in the transboundary Langat River, Malaysia. This study determined the spatial and temporal distributions of Cd, Cr and Pb concentrations (2005&ndash, 2015) in the Langat River along with assessing the status of these metals in the drinking water supply chain at the basin. Water samples were collected once in 2015 from the drinking water supply chain, i.e., from the river, treated water at plants, taps and filtration water at households. Determined mean concentrations of Cd, Cr and Pb by inductively coupled plasma mass spectrometry in the Langat River were within the drinking water quality standard of Malaysia and the WHO, except for the Pb (9.99 &plusmn, 1.40 &micro, g/L) concentration, which was at the maximum limit, 10 &micro, g/L. The spatial and temporal distribution of these metals&rsquo, concentrations indicate dilution of it downstream, along with the increasing trend in rainfall and water flow, especially during the northeast monsoon. Significant correlation and regression analysis of the Cd, Cr and Pb concentrations also indicate that the sources of this metal pollution are mainly the natural weathering of minerals along with anthropogenic activities in the basin. The determined overall water quality of the Langat River is categorized Class IIA (i.e., clean), which requires conventional treatment before drinking, however, the maximum removal efficiency of these metals by the plants at the basin was about 90.17%. Therefore, the proactive leadership roles of the local authorities will be appropriate to reduce the pollution of this river as well as introducing a two-layer water filtration system at the Langat River Basin to accelerate the achievement of a sustainable drinking water supply.

Tropical mangrove swamps are commonly characterized by dense networks of tidal channels that may show pronounced meandering and dendritic patterns. Channel meanders are sometimes accompanied by cut offs, and, like classical fluvial meanders, record changes in hydrology and sedimentation over time. Channel meandering can, thus, be an important process that contributes to spatial and temporal variability in the preserved record of the sedimentology and geochemistry of mangrove sediments. The aim of this study is to highlight changes in channel meander sedimentation in response to a meander cut-off in a tropical mangrove swamp. Two short sediment cores were sampled, respectively from a point bar (core KR1, 122 cm) at the junction with the neck cut-off and inside the cut-off (core KR2, 98 cm) in the Sungai Kerteh mangroves of Peninsular Malaysia. The profile comparison was based on sediment characteristics, total organic carbon (TOC) and selected elements (Fe, Na, Mg, Mn, Ba and Sr). Sedimentation rates at both sites were determined from 210 Pb. A smaller standard deviation of mean grain size (MGS) was found at the point bar (4.37±0.51 ϕ) than in the cut-off (4.43 ±1.76 ϕ), indicating a difference in flow velocity between the two settings. A small difference in sedimentation rate between the upper (0.41 cm.yr -1 ) and bottom (0.50 cm.yr -1 ) parts of core KR1 suggests that water velocity at the point bar area has been rather uniform over the timescale of sedimentation. On the other hand, a higher sedimentation rate in the bottom (0.60 cm.yr -1 ), compared to the upper (0.39 cm.yr -1 ) part of core KR2 may reflect a reduction in sediment supply following cut-off. This change also resulted in increased accumulation of selected elements and TOC at the cut-off site from a depth of ~ 60 cm to the core-top segment probably associated with a slowing down of sediment settling. A higher TOC recorded in the cut-off (2.74±1.42%) compared to the point bar (1.14±0.46%) suggests a propensity for prolonged in-situ accumulation of organic matter in the abandoned meander bend. This study provides grain-size and sediment geochemical information that is consistent with patterns of long-term active and inactive sedimentation in the meander bends of mangrove channels.

Exposure to aluminium (Al) is inevitable in the daily life because of its abundance in the environmental media through natural processes. Meanwhile, several studies have reported a positive association between Alzheimer’s disease and a higher level of Al ingestion through drinking water. The present study is the first of its kind in Malaysia which predicts the human health risk of Al ingestion via drinking water at the Langat River Basin, Malaysia. Water samples were collected during 2015–2016 from the four stages of drinking water supply chain at the basin to determine the concentrations of Al by the Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The determined mean concentration of Al in river 2.50E−01 ± 1.89E−01 mg/L crossed the Malaysian drinking water quality standard of 0.2 mg/L. The higher concentration of Al in the Langat River might be due to natural weathering of Al-bearing minerals. The mean Al concentrations in the treated water by the treatment plants, household’s tap and after filtration water, respectively, were found to be within the Malaysian drinking water quality standard. This study suggests that there is no potential human health risk of Al ingestion through drinking water (HQ = 3.81E−03 ± 1.82E−03) at 95% confidence level in the basin because the hazard quotient (HQ) value is less than 1. However, the authorities need to be careful of excessive ingestion of Al via drinking water because the water treatment plants in the basin follow the conventional method to treat raw water. The turbidity in the tropical Langat River changes very frequently; thus, the doses of Al2(SO4)3 for water disinfection are very crucial. Therefore, reverse osmosis technology can be introduced in the treatment plants because the United States Environmental Protection Agency has recommended that it can remove all types of metal > 90% from treated water.

Atmospheric particles in the surface air including aerosol and dust were collected using high volume air sampler (HVAS) for obtaining the activity levels of 210Pb and 210Po over Malaysian waters during the EPSP’09 Scientific Expedition. The average mass concentration of total suspended particles (TSP) in maritime air was 33 ± 2 µg/m3 (ranged from 13 ± 1 to 74 ± 4 µg/m3). Based on previous literatures, it has been suspected that the haze episodes were mainly due to forest and peat bog fires as well as vehicle and industrial emissions during dry period, especially during southwest monsoon. Consequently, the activity levels of 210Pb and 210Po in maritime particles were relatively in proportion with the TSP concentrations. Meanwhile, the temporal variation of 210Po/210Pb activity ratios in the aerosol samples perhaps related to the difference of residence time airborne particles and contribution from different sources of radionuclides in which 210Pb and 210Po are not in secular equilibrium. The highest TSP concentrations and 210Pb and 210Po activities were closely related to warm and dry period during southwest monsoon.

A total of 97 surficial sediment samples were collected from the Kelantan River, Pahang River and offshore water of Peninsular Malaysia located in the east coast mainly in to investigate the sources and sinks of 210Pb in the southern South China Sea region. At the locations studied, the concentration activity of 210Pb was recorded from the Kelantan River (n = 28), Pahang River (n = 44) and offshore waters (n = 25), ranging from 2.7 ± 0.46 Bq/kg to 52.07 ± 5.23 Bq/kg, 8.65 ± 3.56 Bq/kg to 83.04 ± 6.71 Bq/kg, and 6.72 ± 2.92 Bq/kg to 42.2 ± 3.94 Bq/kg, respectively. Both riverine systems received huge amounts of 210Pb concentrations via mobilised particulate matter, where erosional igneous rocks and weathered sedimentary layers were prominent in elevating the amount of 210Pb from the source towards the sinks. In the offshore margins, the concentrations differed according to the source. As both rivers move towards the sinks in the coastal territories, boundary scavenging becomes prominent. In the offshore territories, a deficiency of 210Pb leads to excess 226Ra in the water column. Scavenged nuclide imported from several sources may increase the total concentrations lingering in the offshore waters of Peninsular Malaysia. Particulate matter mobilised from several sources via upwelling or downwelling in the bottom current through lateral transport further enhances the removal of particle-reactive nuclides from the water column. At the same time, atmospheric deposition via precipitation and transboundary mobilisation of aerosol by mineral dust may increase the total flux on the offshore waters of Peninsular Malaysia.

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.

To understand the modern sedimentation and land-sea interaction processes in the Sunda Shelf, we evaluated the rare earth element (REE) compositions, the total organic carbon (TOC) contents, grain sizes, and detrital minerals of 39 surface sediments, collected from the western Sunda Shelf. All of the sampled sediments are characterised by a higher content of light REEs (LREEs) relative to the content of heavy REEs (HREEs) with negative Eu anomalies. The total content of REE (ΣREE) in the sediments ranges from 7 μg/g to 193 μg/g, with an average of 119 μg/g. Due to the uneven spatial distribution of REEs in the study area, a Q-cluster analysis is applied to the mean grain size (Mz), ∑REE, δEu, δCe, (La/Yb)N, and (Gd/Yb)N data. On this basis, the study area can be classified into three geochemical provinces. The north to central zone in the study area is designated as province I, which has the highest REE content among the three provinces. This is a result of the finer grain size, dominance of siderite, and higher TOC contents of the sediments in province I. The REE content of province II in the southwest coastal zone is lower than that of province I due primarily to a coarser grain size and high quartz, biodetritus, and plagioclase contents. Covering the central coastal zone, province III has the lowest REE content among the three provinces because of the extremely coarse grain size and very high quartz and biodetritus contents. The upper continental crust (UCC)-normalised REE patterns differ markedly among the three provinces, thereby indicating different provenances and transport mechanisms. Based on the provenance discrimination plot and the UCC-normalised REE patterns of these three provinces and adjacent rivers, we infer that province I is largely fed by the Mekong and Kelantan rivers. The fine-grained sediments from these rivers are transported to north and central zone by the northeast monsoon current. The Pahang River is identified as the main sediment source of province II. The coarse-grained sediments from this river mostly accumulate near the estuary via hydrodynamic sorting, while finer-grained sediments are transported to the south by the southward coastal currents. The sediments in province III are inferred as being primarily the result of coastal erosion due to the strong wave energy in this area, as well as offshore and longshore sediment transport acting, in parallel to the coast line. Our study can serve as a reference for studying the diffusion and transport processes of mountainous river sediment and the evolution of the paleoclimate and paleoenvironment in tropical low-latitude regions.

Sedimentation rate at Kuantan and Kemaman harbours were determined by applying the 210Pb profiles. The activities of natural radionuclide 210Pb in sediment core were measured by gross alpha/beta spectrometry. This investigation of sedimentation rate is a part of an overall study to examine and quantify past and present patterns of sedimentation, revealing how deposition of sediments occurs in active physical activities areas such as marine harbours. This is the first report of sedimentation rates in Kuantan and Kemaman harbour, Malaysia which show the sedimentation rate at Kemaman (0.45±0.08) is higher compared to Kuantan harbour (0.16±0.02) which might be due to high physical activities (e.g., shipping activities) at the harbour area. By assuming the constant sedimentation rate; we can consider the sediment age at Kemaman is younger than Kuantan harbour. The age of upper 18 cm sediment core at Kemaman harbour and Kuantan harbour is around 113 and 40 years, respectively. Well dated sediment core can be used in forthcoming research to investigate the historical profile of anthropogenic activities affecting the Kuantan and Kemaman harbours.

The presence of toxic polonium-210 (Po-210) in the environment is due to the decay of primordial uranium-238. Meanwhile, several studies have reported elevated Po-210 radioactivity in the rivers around the world due to both natural and anthropogenic factors. However, the primary source of Po-210 in Langat River, Malaysia might be the natural weathering of granite rock along with mining, agriculture and industrial activities. Hence, this is the first study to determine the Po-210 activity in the drinking water supply chain in the Langat River Basin to simultaneously predict the human health risks of Po-210 ingestion. Therefore, water samples were collected in 2015&ndash, 2016 from the four stages of the water supply chain to analyze by Alpha Spectrometry. Determined Po-210 activity, along with the influence of environmental parameters such as time-series rainfall, flood incidents and water flow data (2005&ndash, 2015), was well within the maximum limit for drinking water quality standard proposed by the Ministry of Health Malaysia and World Health Organization. Moreover, the annual effective dose of Po-210 ingestion via drinking water supply chain indicates an acceptable carcinogenic risk for the populations in the Langat Basin at 95% confidence level, however, the estimated annual effective dose at the basin is higher than in many countries. Although several studies assume the carcinogenic risk of Po-210 ingestion to humans for a long time even at low activity, however, there is no significant causal study which links Po-210 ingestion via drinking water and cancer risk of the human. Since the conventional coagulation method is unable to remove Po-210 entirely from the treated water, introducing a two-layer water filtration system at the basin can be useful to achieve SDG target 6.1 of achieving safe drinking water supplies well before 2030, which might also be significant for other countries.

Sediment cores collected from three Malaysian marine ports, namely, Kota Kinabalu, Labuan and Klang were analyzed to determine the radioactivities of 234U, 238U, 230Th, 232Th and total organic carbon (TOC) content. The objectives of this study were to determine the factors that control the activity of uranium isotopes and identify the possible origin of uranium and thorium in these areas. The activities of 234U and 238U show high positive correlation with TOC at the middle of sediment core from Kota Kinabalu port. This result suggests that activity of uranium at Kota Kinabalu port was influenced by organic carbon. The 234U/238U value at the upper layer of Kota Kinabalu port was ≥1.14 while the ratio value at Labuan and Klang port was ≤ 1.14. These results suggest a reduction process occurred at Kota Kinabalu port where mobile U(VI) was converted to immobile U(IV) by organic carbon. Therefore, it can be concluded that the major input of uranium at Kota Kinabalu port is by sorptive uptake of authigenic uranium from the water column whereas the major inputs of uranium to Labuan and Klang port are of detrital origin. The ratio of 230Th/232Th was used to estimate the origin of thorium. Low ratio value (lt; 1.5) at Labuan and Klang ports support the suggestion that thorium from both areas were come from detrital input while the high ratio (> 1.5) of 230Th/232Th at Kota Kinabalu port suggest the anthropogenic input of 230Th to this area. The source of 230Th is probably from phosphate fertilizers used in the oil-palm cultivation in Kota Kinabalu that is adjacent to the Kota Kinabalu port.

Sediment core collected from Tanjung Pelepas harbour was analyzed to determine the concentrations of trace metals e.g., Al, Fe, Ti, Pb, Zn, Cu and natural radionuclide 210Pb. The aim of this study was to predict the origin of trace metals and date the deposition of sediment that occurred at Tanjung Pelepas harbour using the vertical profile of 210Pb. The estimated sedimentation rate derived from 210Pb profile was 0.57cm/year. The entire datasets of trace metals were analyzed statistically using the Pearson correlation coefficient and principal component analysis (PCA) to predict their origins. The results showed that Al, Fe and Ti originated from natural sources while Zn and Cu came mainly from anthropogenic sources. Pb was dominated with both anthropogenic and natural sources. The enrichment factors (EF) were also calculated to estimate the level of contamination. The EF indicated that Tanjung Pelepas harbour is considered to have minor enrichment (EF

Surface seawater was collected using a high-volume water pump in Malaysian waters during the first Prime Scientific Sailing Expedition in 2009 to obtain activity levels of lead-210 (210Pb) and polonium-210 (210Po). The 210Pb activity in surface water obtained from this sampling ranged from 0.22 ± 0.06 to 0.96 ± 0.31 mBq/L, averaging 0.58 ± 0.28 mBq/L, whereas the 210Po activity was between 1.52 ± 0.11 and 8.98 ± 0.96 mBq/L, averaging 4.19 ± 0.58 mBq/L. The 210Po/210Pb activity ratios in the surface water at the studied sites were between 3.48 ± 1.06 and 13.08 ± 3.78, with an average of 7.27 ± 3.73, which is distinctly higher than the range of 0.1 to 2.8 in the whole southern South China Sea and western Pacific regions. The relatively high activities of dissolved 210Po in Malaysian waters can be attributed to high depositional fluxes of the radionuclides from enhanced dry precipitations caused by haze events. The higher 210Po fractions found in this study compared with those found in the major oceans were due to terrestrial fires with estimated 210Po residence times between 0.15 and 0.51 years, slightly less than the 0.2- to 0.8-year residence times found in oceans with higher productivities. Higher residence times have also been observed more often offshore than near the shoreline. This phenomenon results in a slower rate of removal of 210Po from offshore surface water.

Grain size is an important controlling factor of the chemical composition of sediments. To understand the role of grain size in the content of rare earth elements (REE) in tropical mountainous river sediments and to establish suitable provenance proxies, sediments collected from Pahang River and Kelantan River, Peninsular Malaysia, were determined for REE contents in six size fractions (

Biogenic burning as forest fire phenomena occurring from April to August each year in the Sumatra and Borneo islands are major sources of biogenic uranium–thorium decay series in marine systems. 30 samples were collected during the Ekspedisi Pelayaran Saintifik Perdana 2009 cruise (EPSP 2009 cruise) between 12th June and 1st August 2009 from the Straits of Malacca to the Sulu and Sulawesi Seas to study the effect of haze and the monsoon season on the deposition rate of 210Po and 210Pb in Malaysian waters. All samples were spiked with 1 ml of lead [Pb(NO3)2; 25 mg ml−1] and 0.05 ml of Polonium-209 tracer (26.08 dpm ml−1). 210Po activity was determined by auto plating onto silver foil and counting using an alpha spectrometry system (Canberra model Alpha Analyst with a silicon-surface barrier detector). Lead that was collected via electrodeposition, formed lead sulphate (PbSO4) precipitation. This precipitate was wrapped onto plastic discs and counted for 210Pb beta activity using a gross alpha–beta counting system (Tennelec model LB-5100 low background gas-flowing anti-coincidence alpha/beta counter) after 1 month to allow bismuth ingrowths. The range of 210Po activities varied between 51.08 ± 15.1 and 742.08 ± 220.34 Bq/kg, whereas the activity of 210Pb ranged from 31.10 ± 4.20 to 880.23 ± 123.86 Bq/kg and 210Po/210Pb ratio value varied between sampling stations from 0.19 to 13.77. The contents of 210Po were also statistically positively correlated with the amount of total suspended particulate especially those recorded during heavy haze period events.

In the last century, application of fossil fuel as the primary source of energy caused environmental pollution in many countries including Malaysia. Polycyclic Aromatic Hydrocarbons (PAHs) are an important class of petroleum contamination. Two sediment cores were collected from the Tebrau Strait at the southern part of Peninsular Malaysia near the border line to Singapore, where entering into the South China Sea. The samples were sliced in certain intervals, extracted with Dichloromethane in Soxhlet apparatus, cleaned and fractionated in 2-steps column chromatography, and analyzed in Gas Chromatography – Mass Spectrometry. The results showed that PAHs input were started soon after World War II and exponentially increased from 1980 onward by 310 ng/g d. w., in comparison it was negligible and probably nature derived during 18th and 19th century. The application of compound-specific ratios and pentacyclic teriterpanes suggested the vicinity of sources that atmospherically transported to the sampling locatio...

Marine sediment cores were collected from two stations at East Malaysia coastal waters on June 2004. Activity concentrations of 210Pb in sediment core were ranged from 11 Bqkg−1 to 84 Bqkg−1 dry wt. for SR 01 and 4 Bqkg−1 to 66 Bqkg−1 dry wt. for SB 03. Meanwhile, activity concentrations of 226Ra in sediment core were varied significantly depending on the sampling location of SR 01 and SB 03 with ranged 17–26 Bqkg−1 dry wt. and 8–11 Bqkg−1 dry wt., respectively. The activity ratios of 210Pb/226Ra were no significantly different at all sampling stations with an average of 1.78. Refer to the entire results; the activities of 210Pb and 226Ra were higher at station SR 01 than station SB 03, but contrast with ratio of 210Pb/226Ra. The reasons of different 210Pb and 226Ra activity concentration and distribution of their ratios were strictly related to their half lives, environment origin, potential sources and behavior.

Protactinium and thorium activities were measured in eight surface sediment taken in 2004 to determine effectiveness scavenging of 231Pa at Sabah–Sarawak coastal waters. The result found that activity ratios of 231Paex/230Thex were ranged from 0.07 to 0.13 at all sampling stations. The high 231Paex/230Thex activity ratio than the production ratio of 0.093 in seawater at station SR 01, SR 02, SR 04, SB 02 and SB 05, revealed that 231Pa is effectively removed from the water column into the sediment in comparison with 230Th at those stations. Low percentage of 230Thex (90–95%) in comparison with 231Paex at all stations can be attributed to less efficiently scavenged of 230Th onto particles prior deposited at the marine sediment bed.

Massive development over the past century has led to environmental oil-related pollution around the Malaysian city of Malacca. To characterize the concentration, sources, and origins of polycyclic aromatic hydrocarbons in Malacca’s coastal water in the Strait of Malacca, sediment cores from near shore and offshore were collected and analyzed. The highest concentration of total polycyclic aromatic hydrocarbons (PAHs) in the Near Shore station core was 4447 ng/g dry weight (dw) (1963–1969), and the lowest was 177 ng/g dw (1949–1955). The lowest concentration of PAHs in the Near Shore sample was 452 ng/g dw (1991 to 1997). In general, the Offshore core showed lower concentrations of total PAHs than did the Near Shore core, ranging from 1.71 (1914–1920) to 714.37 ng/g dw (1963–1969). Diagnostic tools such as specific compound, isomer ratio, and hopane characteristics indicate pollution by petroleum and combustion of oils from Southeast Asia and the Middle East in the study area since the1940s.

A method for determination of 226Ra and 228Ra in environmental samples using the α-β coincidence liquid scintillation counting (LSC) has been developed. Radium were preconcentrated from environmental samples by coprecipitation with BaSO4, then purified from others radionuclide interferences using the cation column exchange (Bio-Rad AG 50 W-X4 resin with 200-400 mesh size and H+ form) and operating in warm temperature which is between 70-80oC. Then, the Ba(Ra)SO4 precipitate was filtered through the Millipore filter paper, dried and weighed to calculate chemical yield. The activity concentration of radium isotopes in mixture of liquid scintillation cocktails were measured using LSC after being stored for over 21 days to allow the growth of the progeny nuclides. The method has been validated with a certi-fied reference material supplied by the International Atomic Energy Agency and reliable results were obtained. The radiochemical yields for radium were 59% - 90% and recovery was 97% and 80% for 226Ra and 228Ra, respectively. Sixteen seawater and fish flesh samples collected in Kapar coastal water have been analyzed with the developed method. The obtained radium activity concentrations in seawater were in the range of 02.08 ± 0.82 mBq/L to 3.69 ± 1.29 mBq/L for 226Ra and 6.01 ± 3.05 mBq/L to 17.07 ± 6.62 mBq/L for 228Ra. Meanwhile, the activity concentrations of 226Ra and 228Ra in fish flesh were in the range of 11.82 ± 5.23 – 16.53 ± 6.53 Bq/kg dry wt. and 43.52 ± 16.34 – 53.57 ± 19.86 Bq/kg dry wt., respectively.

Polycyclic aromatic hydrocarbons (PAHs) constitute a class of organic pollutants in the environment that come from combustion of organic matter and petroleum products and from natural sources. Reconstruction of PAH history from two sedimentary cores of the Strait of Johor in peninsular Malaysia showed predominance of urban over marine-based sources of oil pollution. Laboratory analysis of the cores found oil pollution from city-sourced material since 1910 and 1940 in the near-shore and offshore samples, respectively. Using hopane as molecular biomarker of petroleum pollution, this study found a predominance of Southeast Asian-originated oil and its derivatives. This study concludes that crankcase oil, asphalt, street dust and urban sediments considerably contribute to oil pollution of the study area.

For the first time, in May 2007, the distributions of polycyclic aromatic hydrocarbons (PAHs) were studied in the soft tissues (STs) (mantle, gills, foot, gonad, muscle, byssus, and remaining soft tissues) of the green-lipped mussel Perna viridis, collected from eight geographic locations along the coastal waters of peninsular Malaysia. The STs of the mussels collected from the eastern part of the Johore Straits indicated higher bioavailability of and contamination by PAHs than from other areas. The results also indicated a significantly higher concentration of the lower molecular weight (LMW) PAHs in tissues compared to that of the higher molecular weight (HMW) PAHs, perhaps due to the greater bioavailability of the more water-soluble LMW PAHs or related to a partial biotransformation of the higher molecular weight PAHs. The results also suggest that the differences found in the contents of PAHs in various STs of P. viridis were mainly due to differences between individual PAHs volatility and solubility ...

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.

A total of eight sediment cores with 50 cm length were taken in the Sabah and Sarawak coastal waters using a gravity corer in 2004 to estimate sedimentation rates using four mathematical models of CIC, Shukla-CIC, CRS and ADE. The average of sedimentation rate ranged from 0.24 to 0.48 cm year−1, which is calculated based on the vertical profile of 210Pbex in sediment core. The finding also showed that the sedimentation rates derived from four models were generally shown in good agreement with similar or comparable value at some stations. However, based on statistical analysis of paired sample t-test indicated that CIC model was the most accurate, reliable and suitable technique to determine the sedimentation rate in the coastal area.

Inventories and fluxes of 210Pb, 228Ra and 226Ra were determined in sediment cores collected at nine stations covering of the southern South China Sea and Malacca Straits with the thickness of water column between 42 and 83 m depth. The inventories of 210Pb, 228Ra and 226Ra were calculated range from 0.15–2.55 Bq cm−2, 0.05–0.40 Bq cm−2 and 6.83–83.63 Bq cm−2, meanwhile the fluxes ranged from 0.005–0.079 Bq cm−2 yr−1, 0.009–0.048 Bq cm−2 yr−1 and 0.003–0.037 Bq cm−2 yr−1, respectively. The results show that the highest inventories and fluxes for 210Pb, 228Ra and 226Ra were found at station WC 01 and EC 05. Because there are additional sources of 210Pb, 228Ra and 226Ra, where water transport will brings more dissolved isotopes, influence of the transportation and deposition of suspended particles, fast rate of regeneration and greater production of those radionuclides and others.

Thorium activity concentrations were measured in seven marine sediment cores taken from Sabah-Sarawak coast on 2004 by using a gravity box corer. Collected sediments were generally homogenous mud which contained much more mixture of silt and clay compared to sand and relatively low content of organic carbon (i.e. less than 5% at all sampling stations). The results found that activity concentrations of 230Th, 232Th and ratios of 230Th/232Th were ranged from 6.5–20.4 Bq/kg dry wt., 6.8–27.8 Bq/kg dry wt. and 0.69–0.92, respectively. It seem that, 232Th activity concentrations are slightly higher than 230Th at all sampling stations and both radionuclides were generally high at Sabah compared to Sarawak coastal waters. 230Th activity concentrations in sediment core appear to be correlated with the activity concentrations of 232Th at some sampling station. These indicating both radionuclides were supplied from the same of environment and source origin of detrital from terrestrial and shallower water. The low 230Th/232Th activity ratio which is less than unity suggesting that 232Th was actively and rapidly regenerated compared to 230Th from 234U. It also can be attributed to less efficiently scavenge of 230Th onto particles prior deposited at the marine sediment bed.

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.

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