Heavy metal bioaccumulation and risk assessment in fishery resources from the Gulf of Thailand.

The muscle tissues of 19 fish species, two crab species, and one shrimp species collected from the Gulf of Thailand (GoT) were analyzed to determine the levels of heavy metals, including Cu, Zn, Fe, Mn, Ni, Pb, Cd, and Hg. The results revealed that the mean concentrations of the heavy metals, in descending order, were Zn > Cu > Fe > Cd > Hg > Mn > Pb > Ni. Among the examined metals, zinc was found to be the most prevalent in fish tissues. Based on the risk assessment indices, the estimated average daily doses (ADD) of the heavy metals were found to be below the provisional tolerable daily intake (PTDI) recommended by the joint Committee of the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) on food contaminants. The results of the target cancer risk analysis revealed no related cancer risk from the consumption of the fishes considered for the study. However, the target hazard quotient (THQ) values exceeded the threshold of 1 (THQ > 1) specifically for mercury in Gymnothorax spp. and Terapon spp. Furthermore, the calculated hazard index (HI) values for fish muscles were all below 1, indicating that there is no significant health risk for humans at the current consumption rates, except in Terapon species for both normal and habitual consumers. Notably, habitual consumers of Gymnothorax species showed the highest HI value (>1), suggesting potential long-term effects on human health when consuming larger quantities of these fishes.

Seasonal variation and mobility of trace metals in the beach sediments of NW Borneo.

Miri city has a dynamic coastal environment, mainly influenced by intensive sedimentation from the Baram River and excessive trace metal loading by the Miri River, which are significant environmental concerns. As the mobility, bioavailability, and toxicity of the trace metals in the sediments are largely controlled by their particulate speciation, the modified BCR sequential extraction protocol was applied to determine the particulate speciation of trace metals in the coastal sediments of Miri, to unravel the seasonal geochemical processes responsible for known observations, and to identify possible sources of these trace metals. The granulometric analysis results showed that littoral currents aided by the monsoonal winds have influenced the grain size distribution of the sediments, enabling us to divide the study area into north-east and south-west segments where the geochemical composition are distinct. The Cu (>84%) and Zn (82%) concentrations are predominantly associated with the exchangeable fraction, which is readily bioavailable. Pb and Cd are dominant in non-residual fractions and other metals viz., Fe, Mn, Co, Ni, and Cr are dominant in the residual fraction. Using Pearson's correlation and factor analysis, the major mechanisms controlling the chemistry of the sediments are identified as association of Cu and Zn with fine fraction sediments, sulphide oxidation in the SW segment of the study area, atmospheric fallout of Pb and Cd in the river basins, precipitation of dissolved Fe and Mn supplied from the rivers and remobilization of Mn from the coastal sediments. Based on various pollution indices, it is inferred that the coastal sediments of NW Borneo are contaminated with Cu and Zn, and are largely bioavailable, which can be a threat to the local aquatic organisms, coral reefs, and coastal mangroves.

Altered electrochemical properties of iron oxide nanoparticles by carbon enhance molecular biocompatibility through discrepant atomic interaction.

Recent advancement in nanotechnology seeks exploration of new techniques for improvement in the molecular, chemical, and biological properties of nanoparticles. In this study, carbon modification of octahedral-shaped magnetic nanoparticles (MNPs) was done using two-step chemical processes with sucrose as a carbon source for improvement in their electrochemical application and higher molecular biocompatibility. X-ray diffraction analysis and electron microscopy confirmed the alteration in single-phase octahedral morphology and carbon attachment in Fe3O4 structure. The magnetization saturation and BET surface area for Fe3O4, Fe3O4/C, and α-Fe2O3/C were measured as 90, 86, and 27 emu/g and 16, 56, and 89 m2/g with an average pore size less than 7 nm. Cyclic voltammogram and galvanostatic charge/discharge studies showed the highest specific capacitance of carbon-modified Fe3O4 and α-Fe2O3 as 213 F/g and 192 F/g. The in vivo biological effect of altered physicochemical properties of Fe3O4 and α-Fe2O3 was assessed at the cellular and molecular level with embryonic zebrafish. Mechanistic in vivo toxicity analysis showed a reduction in oxidative stress in carbon-modified α-Fe2O3 exposed zebrafish embryos compared to Fe3O4 due to despaired influential atomic interaction with sod1 protein along with significant less morphological abnormalities and apoptosis. The study provided insight into improving the characteristic of MNPs for electrochemical application and higher biological biocompatibility.

Analysis of tebuconazole residues in coconut water, kernel and leaves using LC-MS/MS.

A method was validated for determining tebuconazole residues in coconut water, kernel and leaves using Liquid chromatography-Mass spectrometry/Mass spectrometry (LC-MS/MS) with electro spray ionization in positive ion mode. Samples were extracted with acetonitrile and subsequent clean-up was done using dispersive solid phase extraction. Recovery ranged between 70 and 114.39 % and the RSD was between 0.64 and 10.24 %. Root feeding studies with tebuconazole @ 5 and 10 mL/100 mL of water/tree revealed the presence of tebuconazole residues in coconut leaves until three days after treatment but dissipated to below quantifiable limit on 5th day at single dose while the residues went below quantifiable limit after 10 days at double the dose. Residues were below quantifiable limit in coconut water and kernel until three days. Data obtained from the study were used for estimating the risks associated with the exposures to tebuconazole residues in coconut.

Geochemical behaviour and risk assessment of trace elements in a tropical river, Northwest Borneo.

By convention, dissolved trace elements in the river water are considered to be the fraction that passes through a 0.45 µm filter. However, several researchers have considered filtration cut-off other than 0.45 µm for the separation of dissolved trace elements from particulate fraction. Recent research indicated that trace elements could exist in particulate form as colloids and natural nanoparticles. Moreover, the trace elements in the continental dust (aerosols) constitute a significant component in their geochemical cycling. Due to their high mobility, the trace elements in the micron and sub-micron scale have biogeochemical significance in the coastal zone. In this context, this study focuses on the highly mobile fraction of trace elements in particulates (<11 µm) and dissolved form in the Lower Baram River. A factor model utilizing trace elements in the dissolved and mobile phase in the particulates (<11 µm) along with water column characteristics and the partition coefficient (Kd) of the trace elements indicated a more significant role for manganese oxyhydroxides in trace element transport. Perhaps, iron oxyhydroxides play a secondary role. The factor model further illustrated the dissolution of aluminium and authigenic clay formation. Except for Fe and Al, the contamination risk of mobile trace elements in particulates (<11 µm) together with dissolved form are within the permissible limits of the Malaysian water quality standards during monsoon (MON) and postmonsoon (POM) seasons.

Bioaccumulation of trace metals in the coastal Borneo (Malaysia) and health risk assessment.

The concentration of nine trace elements were analyzed in the different tissue organs of commonly available crabs (Portunus sanguinolentus, Portunus pelagicus and Scylla serrate) and bivalve (Polymesoda erosa) species collected from the Miri coast, Borneo in order to evaluate the potential health risk by consumption of these aquatic organisms. Among the analyzed organs, metal accumulation was higher in the gill tissues. The essential (Cu and Zn) and non-essential (Pb and Cd) elements showed the highest (i.e. Zn) and lowest concentrations (i.e. Cd) in their tissue organs, respectively. The estimated daily intake and hazard indices of all metals in the muscle indicate that the measured values were below the provisional tolerable daily intake suggested by the joint FAO/WHO Expert Committee on Food Additives. Compared to Malaysian and international seafood guideline values the results obtained from the present study are lower than the permissible limits and safe for consumption.

Environmental significance and geochemical speciation of trace elements in Lower Baram River sediments.

The geochemistry and distribution of major, trace and rare earth elements (REE's) was studied in the surface sediments of the Lower Baram River during two seasons: the Monsoon (MON) and Post - monsoon (POM). The major geochemical processes controlling the distribution and mobility of major, trace and REE's in the Lower Baram River surface sediments was revealed through factor analysis. The risk assessment of major and trace element levels was studied at three specific levels; i.e. the enrichment level [Contamination Factor (Cf), with the geo-accumulation index (Igeo)], the availability level [metals bound to different fractions, risk assessment code (RAC)], and the biological toxicity level [effect range low (ERL) and effect range medium (ERM)]. The results of all the indices indicate that Cu is the element of concern in the Lower Baram River sediments. The geochemical fractionation of major and trace elements were studied through sequential extraction and the results indicated a higher concentration of Mn in the exchangeable fraction. The element of concern, Cu, was found to be highly associated in the organic bound (F4) fraction during both seasons and a change in the redox, possibly due to storms or dredging activities may stimulate the release of Cu into the overlying waters of the Lower Baram River.

Distribution of isopod parasites in commercially important marine fishes of the Miri coast, East Malaysia.

Isopods occur very commonly as parasites in food fishes. Parasitic isopods are typically marine and usually inhabit the warmer seas. They are blood-feeding; several species settle in the buccal cavity of fish, others live in the gill chamber or on the body surface including the fins. Isopods can cause morbidity and mortality in captive fish populations. The infestation usually pressure atrophy often accompanies the presence of larger parasites. The present study was aimed at collecting information on the neglected group of isopod parasites of the marine fishes from the Miri coastal environment, East Malaysia. A very little information available regarding the distribution of isopod parasites of Malaysian coastal environment. In the present study, nine isopod parasites were  oberved from ten marine fish species. The maximum number of parasites were observed in the months of June and October, 2013. Maximum prevalence was observed in October (50 %) and the minimum was observed in June (7.14 %). The parasitic infestation may lead to an economic loss in commercial fish species.

Synthesis of new colori/fluorimetric chemosensor for selective sensing of biologically important Fe³âº, Cu²âº and Zn²âº metal ions.

New Schiff base chemosensors (1 and 2) based on aryl ether amine were synthesized and demonstrated positional isomer and functional group dependent colori/fluorimetric sensing of Fe(3+), Cu(2+) and Zn(2+) at ppm level. Methoxy salicylaldehyde based chemosensor 1 exhibited selective colorimetric sensing of Fe(3+) whereas 2-hydroxy naphthaldehyde based chemosensor 2 showed selective disappearance of yellow color for Cu(2+) ions. Interestingly, both 1 and 2 exhibited a highly selective strong turn-on fluorescence for Zn(2+). The significance of COOH group in 1 and 2 for Zn(2+) turn-on fluorescence sensing has been confirmed by structure-property studies. Concentration dependent studies of 1 and 2 indicate that Fe(3+), Cu(2+) and Zn(2+) can be detected up to 10 µM. The formation of 1:1 Zn(2+) and chemosensor (1 and 2) confirmed by NMR studies. High selectivity of 1 and 2 was demonstrated by interference studies in presence of different metal ions.

Generation of sub wavelength super-long dark channel using high NA lens axicon.

We investigate the focusing properties of a double-ring-shaped azimuthally polarized beam by a high numerical aperture (NA) lens axicon based on vector diffraction theory. We observe that our proposed system generates a sub wavelength focal hole of 0.5λ having large uniform focal depth of 48λ without any annular aperture. We also observed that the distribution of the total intensity near the focus has little variation with the degree of truncation ß of the incident beam by the pupil. The authors expect such a super-long dark channel may find applications in optical, biological, and atmospheric sciences.

6-Methyl-2,3,4,9-tetra-hydro-1H-carbazole-1-thione.

In the title mol-ecule, C(13)H(13)NS, the dihedral angle between the benzene ring and the fused pyrrole ring is 0.71 (8)° and the cyclo-hexene ring is in an envelope form. The (CH(2))(3) atoms of the cyclo-hexene ring are disordered over two positions; the site-occupancy factor for the major component refined to 0.862 (4). In the crystal, inter-molecular N-H⋯S hydrogen bonds lead to the formation of centrosymmetric aggregates via an R(2) (2)(10) ring.

5-(4-Chloro-phen-yl)-3-(2,4-dimethyl-thiazol-5-yl)-1,2,4-triazolo[3,4-a]isoquinoline.

In the title mol-ecule, C(21)H(15)ClN(4)S, the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.054 (2) Šand a maximum deviation of 0.098 (2) Šfrom the mean plane for the triazole ring C atom that is bonded to the thia-zole ring. The thia-zole and benzene rings are twisted by 66.36 (7) and 56.32 (7)°, respectively, with respect to the mean plane of the triazoloisoquinoline ring system. In the crystal structure, mol-ecules are linked by inter-molecular C-H⋯N inter-actions along the a axis. The mol-ecular conformation is stabilized by a weak intra-molecular π-π inter-action involving the thia-zole and benzene rings, with a centroid-centroid distance of 3.6546 (11) Å. In addition, two other intermolecular π-π stacking inter-actions are observed, between the triazole and benzene rings and between the dihydro-pyridine and benzene rings [centroid-centroid distances = 3.6489 (11) and 3.5967 (10) Å, respectively].

4-(5-Phenyl-1,2,4-triazolo[3,4-a]isoquinolin-3-yl)benzonitrile.

In the title mol-ecule, C(23)H(14)N(4), the triazoloisoquinoline ring system is nearly planar, with an r.m.s. deviation of 0.038 (2) Šand a maximum deviation of -0.030 (2) Šfrom the mean plane of the triazole ring C atom which is bonded to the benzene ring. The benzene and phenyl rings are twisted by 57.65 (8) and 53.60 (9)°, respectively, with respect to the mean plane of the triazoloisoquinoline ring system. In the crystal structure, mol-ecules are linked by weak aromatic π-π inter-actions [centroid-centroid distance = 3.8074 (12) Å]. In addition, the crystal structure exhibits a nonclassical inter-molecular C-H⋯N hydrogen bond.

3-(4-Chloro-phen-yl)-5-phenyl-1,2,4-triazolo[3,4-a]isoquinoline.

In the title mol-ecule, C(22)H(14)ClN(3), the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.033 (2) Šand a maximum departure from the mean plane of 0.062 (1) Šfor the triazole ring C atom, bonded to the benzene ring. The benzene and phenyl rings are twisted by 57.02 (6) and 62.16 (6)°, respectively, to the mean plane of the triazoloisoquinoline ring system. The mol-ecule is stabilized by a weak intra-molecular π-π inter-action [centroid-centroid distance = 3.7089 (10) Å] between the benzene and phenyl rings. In the crystal structure, weak inter-molecular C-H⋯N hydrogen bonds and C-H⋯π inter-actions link the mol-ecules.

Methyl 1-methyl-1H-1,2,3-triazole-4-carboxyl-ate.

The title mol-ecule, C(5)H(7)N(3)O(2), has an almost planar conformation, with a maximum deviation of 0.043 (3) Å, except for the methyl H atoms. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into layers parallel to the bc plane. Inter-molecular π-π stacking inter-actions [centroid-centroid distances = 3.685 (2) and 3.697 (2) Å] are observed between the parallel triazole rings.

1-[3-(4-Chloro-phen-yl)isoquinolin-1-yl]-3,5-diethyl-1H-pyrazole.

The title compound, C(22)H(20)ClN(3), is composed of a dialkyl-substituted pyrazole ring connected to an aryl-substituted isoquinoline ring system with a dihedral angle of 55.8 (1)° between the pyrazole ring and and the isoquinoline ring system. The dihedral angle between the chloro-phenyl ring and the isoquinoline ring system is 28.3 (1)°.

5-Phenyl-3-(2-thien-yl)-1,2,4-triazolo[3,4-a]isoquinoline.

In the title mol-ecule, C(20)H(13)N(3)S, the triazoloisoquinoline ring system is approximately planar, with an r.m.s. deviation of 0.045 Šand a maximum deviation of 0.090 (2) Šfrom the mean plane for the triazole ring C atom which is bonded to the thio-phene ring. The phenyl ring is twisted by 52.0 (1)° with respect to the mean plane of the triazoloisoquinoline ring system. The thio-phene ring is rotationally disordered by approximately 180° over two sites, the ratio of refined occupancies being 0.73 (1):0.27 (1).

2-(2,3,4,9-Tetra-hydro-1H-carbazol-1-ylidene)propane-dinitrile.

In the title mol-ecule, C(15)H(11)N(3), the dihedral angle between the benzene ring and the fused pyrrole ring is 1.07 (5)°. The cyclo-hexene ring adopts an envelope conformation: the dicyano-methyl-ene group at position 1 has a coplanar orientation. An intra-molecular N-H⋯N hydrogen bond generates an S(7) ring motif. Inter-molecular N-H⋯N hydrogen bonds form an R(2) (2)(14) ring in the crystal. A C-H⋯π inter-action involving the benzene ring is also found in the structure.

1-(1-Hy-droxy-8-methyl-9H-carbazol-2-yl)ethanone.

The title compound, C(15)H(13)NO(2), crystallizes with four independent mol-ecules (A, B, C and D) in the asymmetric unit. The carbazole units are almost planar [maximum deviations = 0.015 (3) for A, 0.024 (3) for B, 0.026 (3) for C and 0.046 (3) Šfor D]. In all four mol-ecules, there is an O-H⋯O hydrogen bond involving the hy-droxy substituent and the carbonyl O atom of the adjacent acetyl group, which forms a six-membered ring. In the crystal, the four independent mol-ecules are linked via N-H⋯O and C-H⋯O inter-actions.

Spectroscopic investigations on the synthesis of nano-hydroxyapatite from calcined eggshell by hydrothermal method using cationic surfactant as template.

The present work reports the successful synthesis of nano-hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2) (denoted HAP) from calcined eggshell by hydrothermal method using cationic surfactant (CTAB) as regulator of nucleation and crystal growth. The reaction involved in the synthesis was studied elaborately. The influence of reaction temperature, ageing time and CTAB concentration on the synthesis of nano-HAP are also studied in addition to the effect of sintering temperature on the crystal growth. Spectral characterization involving Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were performed for functional group analysis and phase identification of the materials, respectively. Thermal stability of nano-HAP was investigated by thermal analysis (TG/DTA). The physical characteristics, such as morphology and particle size of the synthesized nano-HAP were assessed thoroughly by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The results have revealed that well-crystallized nano-HAP was synthesized by hydrothermal treatment at 160 degrees C for 10 h with the addition of CTAB at critical micelle concentration (CMC). It was also found that the synthesized nano-HAP was thermally stable up to 1100 degrees C.