Norhayati Mohd Tahir

On-line preconcentration and determination of trace metals using a flow injection system coupled to ion chromatography

A flow injection (FI) method with on-line preconcentration using a mini-column loaded with 8-hydroxyquinoline immobilized on controlled pore glass (CPG-8HQ) is described for the determination of trace metals by ion chromatography (IC) with pyridine-2-6-dicarboxylic acid (PDCA) as the eluent. Copper, cadmium, lead, zinc, nickel and iron were determined at ppb level after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). The detection limits (3sigma) for the FI/IC system were 8.27, 0.89, 0.09, 0.06, 0.09 and 0.07 g l(-1) for Pb(2+), Cd(2+), Cu(2+) Ni(2+), Zn(2+) and Fe(3+), respectively, using 5 ml sample volume. The method was applied to the analysis of Malaysian natural waters.

Surfactants in the sea-surface microlayer and atmospheric aerosol around the southern region of Peninsular Malaysia.

This study was conducted to determine the composition of surfactants in the sea-surface microlayer (SML) and atmospheric aerosol around the southern region of the Peninsular Malaysia. Surfactants in samples taken from the SML and atmospheric aerosol were determined using a colorimetric method, as either methylene blue active substances (MBAS) or disulphine blue active substances (DBAS). Principal component analysis with multiple linear regressions (PCA-MLR), using the anion and major element composition of the aerosol samples, was used to determine possible sources of surfactants in atmospheric aerosol. The results showed that the concentrations of surfactants in the SML and atmospheric aerosol were dominated by anionic surfactants and that surfactants in aerosol were not directly correlated (p>0.05) with surfactants in the SML. Further PCA-MLR from anion and major element concentrations showed that combustion of fossil fuel and sea spray were the major contributors to surfactants in aerosol in the study area.

Comprehensive assessment of PM2.5 physicochemical properties during the Southeast Asia dry season (southwest monsoon)

A comprehensive assessment of fine particulate matter (PM2.5) compositions during the Southeast Asia dry season is presented. Samples of PM2.5 were collected between 24 June and 14 September 2014 using a high-volume sampler. Water-soluble ions, trace species, rare earth elements, and a range of elemental carbon (EC) and organic carbon were analyzed. The characterization and source apportionment of PM2.5 were investigated. The results showed that the 24 h PM2.5 concentration ranged from 6.64 to 68.2 µg m−3. Meteorological driving factors strongly governed the diurnal concentration of aerosol, while the traffic in the morning and evening rush hours coincided with higher levels of CO and NO2. The correlation analysis for non sea-salt K+-EC showed that EC is potentially associated with biomass burning events, while the formation of secondary organic carbon had a moderate association with motor vehicle emissions. Positive matrix factorization (PMF) version 5.0 identified the sources of PM2.5: (i) biomass burning coupled with sea salt [I] (7%), (ii) aged sea salt and mixed industrial emissions (5%), (iii) road dust and fuel oil combustion (7%), (iv) coal-fired combustion (25%), (v) mineral dust (8%), (vi) secondary inorganic aerosol (SIA) coupled with F− (15%), and (vii) motor vehicle emissions coupled with sea salt [II] (24%). Motor vehicle emissions, SIA, and coal-fired power plant are the predominant sources contributing to PM2.5. The response of the potential source contribution function and Hybrid Single-Particle Lagrangian Integrated Trajectory backward trajectory model suggest that the outline of source regions were consistent to the sources by PMF 5.0.

Distribution and sources of hydrocarbons in lagoon sediments of Setiu Wetland, Terengganu, Malaysia.

Hydrocarbon compounds viz. aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), sterols, long chain fatty acids, alkanones and alkanals in surface sediment of Setiu Wetland were analysed and characterized using GCMS. The concentration of total identified resolved n-alkanes (TIRNA) in sediment ranged from 2.99–11.6 μ g g− 1 dry weight. The distribution of the aliphatic fraction showed the presence of n-alkanes ranging from C 12 to C 36 with high predominance for long chain homologues (C 25 -C 31 ) and a carbon maximum at C 29 and C 31 with CPI > 3; these observations provide evidence for the presence of biogenic terrigenous input corresponding to epicuticular plant waxes into the lagoon sediments. Positive and strong correlation between n-alkanes associated with terrigenous input (ALK TER) and TIRNA suggest terrestrial input is the main sources of TIRNA in this study area. The absence of unresolved complex mixture (UCM) in the chromatogram and the absence of hopanes, steranes and PAHs compounds are indicative of uncontaminated sediment by petrogenic and pyrogenic hydrocarbons. The concentration of total identified sterols (TIS) ranged from 1.41 μ g g− 1 dry weight to 3.11 μ g g− 1 dry weight with cholesterol, β -Sitosterol and stigmasterol were generally the most dominant and abundant components detected at almost all stations. A positive and strong correlation was observed between B-Sitosterol and TIS and the distribution of long chain n-alkan-2-ones in the range of C 21 to C 27 with odd to even predominance and n-alkanals (C 20 to C 28 ), n-alkanols (C 22 –C 30 ) and n-alkanoic acids (C 22 –C 30 ) with even to odd predominance provide further evidence for biogenic sources of hydrocarbons with terrestrial plant input as the predominant source. It was noted that a minor contribution associated with marine phytoplankton (algae) as well as bacteria were also observed in some of the sediment samples superimposing with the terrigenous plant wax input. In general results from this study clearly showed the lagoon sediment of Setiu Wetland is still in uncontaminated condition where terrestrial plants input are the dominant contributor of organic compounds in the sediments with a minor input from marine organisms.

A green solvent holder in electro-mediated microextraction for the extraction of phenols in water

Electro-mediated microextraction (EMM) combined with micro-high performance liquid chromatography-ultraviolet detection was successfully developed for the determination of selected phenols, namely 4-chlorophenol (4CP), 2-nitrophenol (2NP) and 2,4-dichlorophenols (2,4 DCP) in water. A solvent-impregnated agarose gel disc was utilized as a solvent holder in this study. Under optimum extraction conditions, the method showed good linearity in the range of 0.1-250µgL-1, 0.3-250µgL-1 and 0.2-500µgL-1 for 4CP, 2NP and 2,4 DCP, respectively with correlation coefficients of ≥ 0.9975, ultra-trace LODs (0.03-0.1µgL-1) and satisfactory relative recovery average (85.0-114.1%) for the analysis of selected phenols. The proposed method was rapid and eco-friendly as the solvent holder was constructed using minute amounts of extraction solvent immobilized within the biodegradable agarose gel disc. A comparative microextraction technique termed solvent-impregnated agarose gel liquid phase microextraction (AG-LPME) was re-optimized and validated for the extraction of phenols in water. The method offered good linearity, ultra-trace LODs ranging 0.1-0.5µgL-1 and satisfactory average of relative recovery (86.1-114.1%). The EMM was superior in terms of sensitivity and time-effectiveness compared to AG-LPME. Both techniques combine extraction and pre-concentration in mini-scaled approaches using an eco-friendly solvent holder that fulfil the green chemistry concept.

Sandbar-regulated hydrodynamic influences on river hydrochemistry at Mengabang Telipot River, Peninsular Malaysia

Influences of river hydrodynamic behaviours on hydrochemistry (salinity, pH, dissolved oxygen saturations and dissolved phosphorus) were evaluated through high spatial and temporal resolution study of a sandbar-regulated coastal river. River hydrodynamic during sandbar-closed event was characterized by minor dependency on tidal fluctuations, very gradual increase of water level and continual low flow velocity. These hydrodynamic behaviours established a hydrochemistry equilibrium, in which water properties generally were characterized by virtual absence of horizontal gradients while vertical stratifications were significant. In addition, the river was in high trophic status as algae blooms were visible. Conversely, river hydrodynamic in sandbar-opened event was tidal-controlled and showed higher flow velocity. Horizontal gradients of water properties became significant while vertically more homogenised and with lower trophic status. In essence, this study reveals that estuarine sandbar directly regulates river hydrodynamic behaviours which in turn influences river hydrochemistry.

Distribution and Sources of Perylene and other Polycyclic Aromatic Hydrocarbons (PAHs) in South China Sea Sediments off Southern Terengganu Coast, Malaysia

Sediment cores from the South China Sea off Southern Terengganu were collected during May (post-Northeast monsoon) and September (pre-Northeast monsoon) 2007. The core sediments were cut into 2 cm sections, freeze-dried and then Soxhlet extracted. Extracts were fractionated using column chromatography and the aromatic hydrocarbon fractions were determined using gas chromatography mass spectrometry. The concentration of perylene varied between 0.43–5.01 ng/g and 0.42–9.79 ng/g in May and September, while the total 16 USEPA listed priority polycyclic aromatic hydrocarbon (TPAHs) ranged from 6.01–20.2 ng/g and 4.89–34.7 ng/g during the same respective periods. The PAH cross plots showed that pyrogenic PAHs dominated during May, whereas pyrogenic and lesser petrogenic PAHs dominated during September. Total organic carbon (TOC) showed strong correlation with TPAH and perylene near land, suggesting transport of terrestrially derived PAHs (biogenic or anthropogenic) into coastal sediments via surface runoff into rivers.

A Preliminary Assessment of Water Quality Status in Tasik Kenyir, Malaysia

The preliminary study of water quality which involved the measurement of physical, chemical and microbiological parameters was conducted in Tasik Kenyir, Malaysia from August until October 2010. Results showed that the water quality of the surface water was in ‘clean’ status based on Malaysian Water Quality Index. However, the bottom water was in ‘slightly polluted’. According to National Water Quality Standard, all stations was in Class I which is suitable for conservation of natural environment, water supply with practically no treatment and fishery activity for very sensitive aquatic species.

A Baseline Assesment on the Distributions and Sources of Aliphatic and Polycyclic Aromatic Hydrocarbons in Abiotic Environment of Terengganu National Park

A baseline study to assess the distributions of aliphatic and polycyclic aromatic hydrocarbons in abiotic environment consisting of soil, sediment and atmospheric particulate samples was carried in Terengganu National Park. Aliphatic hydrocarbons were found in all three media studied whilst polycyclic aromatic hydrocarbon (PAH) compounds were detected, only in the atmospheric particulate samples, at trace levels. The 24 hr-PM10 and Total Suspended Particulate (TSP) concentrations is still below the recommended Malaysian Air Quality Guidelines for the respective parameter. Analyses of the results suggest that terrestrial plant waxes is the main source of aliphatic hydrocarbons in the study area whereas sources for PAHs in the particulate samples are most likely derived from combustion sources. The detection of PAHs in the aerosol samples also suggest possible anthropogenic input of particulate matter to the study area; however the levels are still well below the values reported for other locations in Malaysia.

Spatial and Temporal Distributions of Dissolved Organic Carbon in the Setiu River, Malaysia

In general, higher concentrations of dissolved organic carbon (DOC) were measured at the downstream area of Setiu River basin, which associated with urban location. The high molecular weight (HMW, <100 kDa) DOC fraction generally was dominant consisting of 55–85 % of total DOC, within the DOC pool. Overall, HMW DOC dominance was associated with agricultural, aquaculture and urban areas, and was therefore likely to be a result of anthropogenic inputs. Re-suspension of bottom sediment in the river may have also played an important role in controlling the HMW DOC distribution in present study. The low molecular weight (LMW, <30 kDa) DOC, which constituted 34–70 % of total DOC, was generally showed the significant correlation with chlorophyll-a (chl-a), suggesting phytoplankton related processes may influence the LMW DOC in water column. DOC concentrations were climatological related with high values during the monsoon season and decreased significantly during non-monsoon season.