Displaying publications 1 - 20 of 22 in total

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  1. Fulltext Diversity of isoprene-degrading bacteria in phyllosphere and soil communities from a high isoprene-emitting environment: a Malaysian oil palm plantation
    Carrión O, Gibson L, Elias DMO, McNamara NP, van Alen TA, Op den Camp HJM, et al.
    Microbiome, 2020 06 03;8(1):81.
    PMID: 32493439 DOI: 10.1186/s40168-020-00860-7
    BACKGROUND: Isoprene is the most abundantly produced biogenic volatile organic compound (BVOC) on Earth, with annual global emissions almost equal to those of methane. Despite its importance in atmospheric chemistry and climate, little is known about the biological degradation of isoprene in the environment. The largest source of isoprene is terrestrial plants, and oil palms, the cultivation of which is expanding rapidly, are among the highest isoprene-producing trees.

    RESULTS: DNA stable isotope probing (DNA-SIP) to study the microbial isoprene-degrading community associated with oil palm trees revealed novel genera of isoprene-utilising bacteria including Novosphingobium, Pelomonas, Rhodoblastus, Sphingomonas and Zoogloea in both oil palm soils and on leaves. Amplicon sequencing of isoA genes, which encode the α-subunit of the isoprene monooxygenase (IsoMO), a key enzyme in isoprene metabolism, confirmed that oil palm trees harbour a novel diversity of isoA sequences. In addition, metagenome-assembled genomes (MAGs) were reconstructed from oil palm soil and leaf metagenomes and putative isoprene degradation genes were identified. Analysis of unenriched metagenomes showed that isoA-containing bacteria are more abundant in soils than in the oil palm phyllosphere.

    CONCLUSION: This study greatly expands the known diversity of bacteria that can metabolise isoprene and contributes to a better understanding of the biological degradation of this important but neglected climate-active gas. Video abstract.

    Matched MeSH terms: Butadienes/metabolism
  2. H(2)O(2)/UV degradation kinetics of isoprene in aqueous solution
    Elkanzi EM, Bee Kheng G
    J Hazard Mater, 2000 Mar 13;73(1):55-62.
    PMID: 10686378
    Hydrogen peroxide and UV radiation have been used in the photochemical degradation of isoprene in aqueous solutions. A kinetic study is carried out taking into account the contribution of the UV radiation reaction and the combined reaction with hydrogen peroxide. An empirical reaction rate expression, which considers the two reactions taking place in parallel, is suggested. Pseudo-first order rate constants are obtained from batch reactor data. As the molar ratio of H(2)O(2):isoprene increases, the rate of reaction increases linearly while the concentration of H(2)O(2) is observed to be nearly constant throughout the reaction; suggesting that the H(2)O(2) acts as a pseudo-catalyst. Nearly complete oxidation of isoprene is achieved. These results indicate that the H(2)O(2)/UV process appears to be a competitive alternative destructive treatment for removing isoprene from water present at low levels.
    Matched MeSH terms: Butadienes/radiation effects; Butadienes/chemistry*
  3. Fluorine-19 magnetic resonance imaging probe for the detection of tau pathology in female rTg4510 mice
    Yanagisawa D, Ibrahim NF, Taguchi H, Morikawa S, Kato T, Hirao K, et al.
    J Neurosci Res, 2018 05;96(5):841-851.
    PMID: 29063641 DOI: 10.1002/jnr.24188
    Aggregation of tau into neurofibrillary tangles (NFTs) is characteristic of tauopathies, including Alzheimer's disease. Recent advances in tau imaging have attracted much attention because of its potential contributions to early diagnosis and monitoring of disease progress. Fluorine-19 magnetic resonance imaging (19 F-MRI) may be extremely useful for tau imaging once a high-quality probe has been formulated. In this investigation, a novel fluorine-19-labeling compound has been developed as a probe for tau imaging using 19 F-MRI. This compound is a buta-1,3-diene derivative with a polyethylene glycol side chain bearing a CF3 group and is known as Shiga-X35. Female rTg4510 mice (a mouse model of tauopathy) and wild-type mice were intravenously injected with Shiga-X35, and magnetic resonance imaging of each mouse's head was conducted in a 7.0-T horizontal-bore magnetic resonance scanner. The 19 F-MRI in rTg4510 mice showed an intense signal in the forebrain region. Analysis of the signal intensity in the forebrain region revealed a significant accumulation of fluorine-19 magnetic resonance signal in the rTg4510 mice compared with the wild-type mice. Histological analysis showed fluorescent signals of Shiga-X35 binding to the NFTs in the brain sections of rTg4510 mice. Data collected as part of this investigation indicate that 19 F-MRI using Shiga-X35 could be a promising tool to evaluate tau pathology in the brain.
    Matched MeSH terms: Butadienes/chemical synthesis; Butadienes/chemistry*
  4. Fulltext On the Effects of Process Parameters and Optimization of Interlaminate Bond Strength in 3D Printed ABS/CF-PLA Composite
    Ahmed SW, Hussain G, Altaf K, Ali S, Alkahtani M, Abidi MH, et al.
    Polymers (Basel), 2020 Sep 22;12(9).
    PMID: 32971747 DOI: 10.3390/polym12092155
    The scope of additive manufacturing, particularly fused deposition modelling (FDM), can indeed be explored with the fabrication of multi-material composite laminates using this technology. Laminar composite structures made up of two distinct materials, namely acrylonitrile butadiene styrene (ABS) and carbon fiber reinforced polylactic acid (CF-PLA), were produced using the FDM process. The current study analyzes the effect of various printing parameters on the interfacial bond strength (IFBS) of the ABS/CF-PLA laminar composite by employing response surface methodology. The physical examination of the tested specimens revealed two failure modes, where failure mode 1 possessed high IFBS owing to the phenomenon of material patch transfer. Contrarily, failure mode 2 yielded low IFBS, while no patch transfer was observed. The analysis of variance (ANOVA) revealed that printing parameters were highly interactive in nature. After extensive experimentation, it was revealed that good quality of IFBS is attributed to the medium range of printing speed, high infill density, and low layer height. At the same time, a maximum IFBS of 20.5 MPa was achieved. The study presented an empirical relation between printing parameters and IFBS that can help in forecasting IFBS at any given printing parameters. Finally, the optimized printing conditions were also determined with the aim to maximize IFBS.
    Matched MeSH terms: Butadienes
  5. Fulltext Free-Radical Photopolymerization of Acrylonitrile Grafted onto Epoxidized Natural Rubber
    Whba R, Su'ait MS, Tian Khoon L, Ibrahim S, Mohamed NS, Ahmad A
    Polymers (Basel), 2021 Feb 23;13(4).
    PMID: 33672185 DOI: 10.3390/polym13040660
    The exploitation of epoxidized natural rubber (ENR) in electrochemical applications is approaching its limits because of its poor thermo-mechanical properties. These properties could be improved by chemical and/or physical modification, including grafting and/or crosslinking techniques. In this work, acrylonitrile (ACN) has been successfully grafted onto ENR- 25 by a radical photopolymerization technique. The effect of (ACN to ENR) mole ratios on chemical structure and interaction, thermo-mechanical behaviour and that related to the viscoelastic properties of the polymer was investigated. The existence of the -C≡N functional group at the end-product of ACN-g-ENR is confirmed by infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses. An enhanced grafting efficiency (~57%) was obtained after ACN was grafted onto the isoprene unit of ENR- 25 and showing a significant improvement in thermal stability and dielectric properties. The viscoelastic behaviour of the sample analysis showed an increase of storage modulus up to 150 × 103 MPa and the temperature of glass transition (Tg) was between -40 and 10 °C. The loss modulus, relaxation process, and tan delta were also described. Overall, the ACN-g-ENR shows a distinctive improvement in characteristics compared to ENR and can be widely used in many applications where natural rubber is used but improved thermal and mechanical properties are required. Likewise, it may also be used in electronic applications, for example, as a polymer electrolyte in batteries or supercapacitor.
    Matched MeSH terms: Butadienes
  6. Fulltext Warpage Optimisation on the Moulded Part with Straight Drilled and Conformal Cooling Channels Using Response Surface Methodology (RSM), Glowworm Swarm Optimisation (GSO) and Genetic Algorithm (GA) Optimisation Approaches
    Mohd Hanid MH, Abd Rahim SZ, Gondro J, Sharif S, Al Bakri Abdullah MM, Zain AM, et al.
    Materials (Basel), 2021 Mar 10;14(6).
    PMID: 33802032 DOI: 10.3390/ma14061326
    It is quite challenging to control both quality and productivity of products produced using injection molding process. Although many previous researchers have used different types of optimisation approaches to obtain the best configuration of parameters setting to control the quality of the molded part, optimisation approaches in maximising the performance of cooling channels to enhance the process productivity by decreasing the mould cycle time remain lacking. In this study, optimisation approaches namely Response Surface Methodology (RSM), Genetic Algorithm (GA) and Glowworm Swarm Optimisation (GSO) were employed on front panel housing moulded using Acrylonitrile Butadiene Styrene (ABS). Each optimisation method was analysed for both straight drilled and Milled Groove Square Shape (MGSS) conformal cooling channel moulds. Results from experimental works showed that, the performance of MGSS conformal cooling channels could be enhanced by employing the optimisation approach. Therefore, this research provides useful scientific knowledge and an alternative solution for the plastic injection moulding industry to improve the quality of moulded parts in terms of deformation using the proposed optimisation approaches in the used of conformal cooling channels mould.
    Matched MeSH terms: Butadienes
  7. Fulltext The effects of printing orientation on the electrochemical behaviour of 3D printed acrylonitrile butadiene styrene (ABS)/carbon black electrodes
    Bin Hamzah HH, Keattch O, Covill D, Patel BA
    Sci Rep, 2018 Jun 14;8(1):9135.
    PMID: 29904165 DOI: 10.1038/s41598-018-27188-5
    Additive manufacturing also known as 3D printing is being utilised in electrochemistry to reproducibly develop complex geometries with conductive properties. In this study, we explored if the electrochemical behavior of 3D printed acrylonitrile butadiene styrene (ABS)/carbon black electrodes was influenced by printing direction. The electrodes were printed in both horizontal and vertical directions. The horizsontal direction resulted in a smooth surface (HPSS electrode) and a comparatively rougher surface (HPRS electrode) surface. Electrodes were characterized using cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. For various redox couples, the vertical printed (VP) electrode showed enhanced current response when compared the two electrode surfaces generated by horizontal print direction. No differences in the capacitive response was observed, indicating that the conductive surface area of all types of electrodes were identical. The VP electrode had reduced charge transfer resistance and uncompensated solution resistance when compared to the HPSS and HPRS electrodes. Overall, electrodes printed in a vertical direction provide enhanced electrochemical performance and our study indicates that print orientation is a key factor that can be used to enhance sensor performance.
    Matched MeSH terms: Butadienes
  8. Computational evaluation of unsaturated carbonitriles as neutral receptor model for beryllium(II) recognition
    Rosli AN, Ahmad MR, Alias Y, Zain SM, Lee VS, Woi PM
    J Mol Model, 2014 Dec;20(12):2533.
    PMID: 25433601 DOI: 10.1007/s00894-014-2533-9
    Design of neutral receptor molecules (ionophores) for beryllium(II) using unsaturated carbonitrile models has been carried out via density functional theory, G3, and G4 calculations. The first part of this work focuses on gas phase binding energies between beryllium(II) and 2-cyano butadiene (2-CN BD), 3-cyano propene (3-CN P), and simpler models with two separate fragments; acrylonitrile and ethylene. Interactions between beryllium(II) and cyano nitrogen and terminal olefin in the models have been examined in terms of geometrical changes, distribution of charge over the entire π-system, and rehybridization of vinyl carbon orbitals. NMR shieldings and vibrational frequencies probed charge centers and strength of interactions. The six-membered cyclic complexes have planar structures with the rehybridized carbon slightly out of plane (16° in 2-CN BD). G3 results show that in 2-CN BD complex participation of vinyl carbon further stabilizes the cyclic adduct by 16.3 kcal mol(-1), whereas, in simpler models, interaction between beryllium(II) and acetonitrile is favorable by 46.4 kcal mol(-1) compared with that of ethylene. The terminal vinyl carbon in 2-CN BD rehybridizes to sp (3) with an increase of 7 % of s character to allow interaction with beryllium(II). G4 calculations show that the Be(II) and 2-CN BD complex is more strongly bound than those with Mg(II) and Ca(II) by 98.5 and 139.2 kcal mol(-1) (-1), respectively. QST2 method shows that the cyclic and acyclic forms of Be(II)-2-CN BD complexes are separated by 12.3 kcal mol(-1) barrier height. Overlap population analysis reveals that Ca(II) can be discriminated based on its tendency to form ionic interaction with the receptor models.
    Matched MeSH terms: Butadienes/chemistry
  9. High temperature liquid chromatography of triazole fungicides on polybutadiene-coated zirconia stationary phase
    Sanagi MM, See HH, Ibrahim WA, Naim AA
    J Chromatogr A, 2004 Dec 03;1059(1-2):95-101.
    PMID: 15628129
    High temperature liquid chromatography using water-rich and superheated water eluent is evaluated as a new approach for the separation of selected triazole fungicides, hexaconazole, tebuconazole, propiconazole, and difenoconazole. Using a polybutadiene-coated zirconia column at temperatures of 100-150 degrees C, clear separations were achieved when 100% purified water was utilized as organic-free eluent. Excellent limits of detection down to pg level were obtained for the separation of the triazole fungicides under optimum conditions. Van't Hoff plots for the separations were linear suggesting that no changes occurred in the retention mechanism over the temperature range studied.
    Matched MeSH terms: Butadienes/chemistry*
  10. Structure-activity relationship of polyisoprenyl benzophenones from Garcinia pyrifera on the tubulin/microtubule system
    Roux D, Hadi HA, Thoret S, Guénard D, Thoison O, Païs M, et al.
    J Nat Prod, 2000 Aug;63(8):1070-6.
    PMID: 10978200
    Microtubule disassembly inhibitory properties have been established for the known polyisoprenylated benzophenones xanthochymol (1a) and guttiferone E (1b). The compounds were isolated from the fruits of Garcinia pyrifera collected in Malaysia. A structure-activity relationship study, including natural and semisynthetic derivatives, delineated some structural features necessary for the interaction with tubulin within this compound class.
    Matched MeSH terms: Butadienes/pharmacology*; Butadienes/chemistry
  11. Fulltext Aerogel Poly(butylene succinate) Biomaterial Substrate for RF and Microwave Applications
    Habib Ullah M, Mahadi WN, Latef TA
    Sci Rep, 2015;5:12868.
    PMID: 26238975 DOI: 10.1038/srep12868
    Polybutylene succinate (PBS) has become a potential candidate, similar to polypropylene (PP) and acrylonitrile butadiene styrene (ABS), for use as an organic plastic material due to its outstanding mechanical properties as well as high thermal deformation characteristics. A new composition of silica aerogel nanoparticles extracted from rice waste with PBS is proposed for use as a dielectric (εr = 4.5) substrate for microwave applications. A microstrip patch antenna was fabricated on the proposed dielectric substrate for multi-resonant ultra-wideband (UWB) applications. The performance characteristics of the proposed biomaterial-based antenna were investigated in a far-field measurement environment. The results indicate that the proposed biocompatible material-based antenna covered a bandwidth of 9.4 (2.3-11.7) GHz with stop bands from 5.5 GHz to 5.8 GHz and 7.0 GHz to 8.3 GHz. Peak gains of 9.82 dBi, 7.59 dBi, 8.0 dBi and 7.68 dBi were measured at resonant frequencies of 2.7 GHz, 4.6 GHz, 6.3 GHz and 9.5 GHz, respectively.
    Matched MeSH terms: Butadienes
  12. Fulltext Evaluation of the Performance of Helmet Prototypes Fabricated from Acrylonitrile Butadiene Styrene Composites Filled with Natural Resource
    Nikmatin S, Hermawan B, Irmansyah I, Indro MN, Kueh ABH, Syafiuddin A
    Materials (Basel), 2018 Dec 22;12(1).
    PMID: 30583516 DOI: 10.3390/ma12010034
    The performance of helmet prototypes fabricated from acrylonitrile butadiene styrene composites filled with oil palm empty fruit bunch fibers was evaluated. The fibers were produced using a milling procedure, while the composites were fabricated using a single-screw extrusion. The physical characteristics of the produced fibers, which are water content, size, and density, were investigated. In addition, the mechanical properties of the produced helmets, including shock absorption, yield stress, frequency, and head injury criterion (HIC), were examined. The impact strength of the produced helmets increases with the rise of filler content. In addition, the helmets were also able to withstand a considerable pressure such that the transmitted pressure was far under the maximum value acceptable by the human skull. The present work also found that HICs exhibited by the investigated helmet prototypes fulfill all the practical guidelines as permitted by the Indonesian government. In terms of novelty, such innovation can be considered the first invention in Indonesia since the endorsement of the use of motorcycle helmets.
    Matched MeSH terms: Butadienes
  13. Fulltext Physicomechanical Properties of Rice Husk/Coco Peat Reinforced Acrylonitrile Butadiene Styrene Blend Composites
    Norhasnan NHA, Hassan MZ, Nor AFM, Zaki SA, Dolah R, Jamaludin KR, et al.
    Polymers (Basel), 2021 Apr 06;13(7).
    PMID: 33917337 DOI: 10.3390/polym13071171
    Utilizing agro-waste material such as rice husk (RH) and coco peat (CP) reinforced with thermoplastic resin to produce low-cost green composites is a fascinating discovery. In this study, the effectiveness of these blended biocomposites was evaluated for their physical, mechanical, and thermal properties. Initially, the samples were fabricated by using a combination of melt blend internal mixer and injection molding techniques. Increasing in RH content increased the coupons density. However, it reduced the water vapor kinetics sorption of the biocomposite. Moisture absorption studies disclosed that water uptake was significantly increased with the increase of coco peat (CP) filler. It showed that the mechanical properties, including tensile modulus, flexural modulus, and impact strength of the 15% RH-5% CP reinforced acrylonitrile-butadiene-styrene (ABS), gave the highest value. Results also revealed that all RH/CP filled composites exhibited a brittle fracture manner. Observation on the tensile morphology surfaces by using a scanning electron microscope (SEM) affirmed the above finding to be satisfactory. Therefore, it can be concluded that blend-agriculture waste reinforced ABS biocomposite can be exploited as a biodegradable material for short life engineering application where good mechanical and thermal properties are paramount.
    Matched MeSH terms: Butadienes
  14. Fulltext The effect of polypropylene maleic anhydride (ppmah) on properties of polypropylene (pp)/recycled acrylonitrile butadiene rubber (nbrr)/ rice husk powder (rhp) composites
    Santiagoo, Ragunathan, Hanafi Ismail, Kamarudin Hussin
    Pertanika Journal of Science & Technology, 2010;18(2):-.
    MyJurnal
    The effect of polypropylene maleic anhydride (PPMAH) on tensile properties and morphology of polypropylene (PP)/recycled acrylonitrile butadiene rubber (NBRr)/ rice husk powder (RHP) composites has been studied. The composites were prepared through melt mixing at 180ºC for 9 minutes using 50 rpm rotor speed. The specimens were analyzed using different techniques, namely tensile test and Scanning Electron Microscopy (SEM). The results obtained showed that the tensile strength and Young’s modulus of the modified composites were increased, while the elongation at break showed the opposite trend as compared with the unmodified composites. The morphology results support the tensile properties and these indicated a better interaction between the filler and matrix with the presence of PPMAH as a compatibilizer.
    Matched MeSH terms: Butadienes
  15. Fulltext A simple design for microwave assisted digestion vessel with low reagent consumption suitable for food and environmental samples
    Gholami M, Behkami S, Zain SM, Bakirdere S
    Sci Rep, 2016 11 17;6:37186.
    PMID: 27853264 DOI: 10.1038/srep37186
    The objective of this work is to prepare a cost-effective, low reagent consumption and high performance polytetrafluoroethylene (PTFE) vessel that is capable to work in domestic microwave for digesting food and environmental samples. The designed vessel has a relatively thicker wall compared to that of commercial vessels. In this design, eight vessels are placed in an acrylonitrile butadiene styrene (ABS) holder to keep them safe and stable. This vessel needs only 2.0 mL of HNO3 and 1.0 mL H2O2 to digest 100 mg of biological sample. The performance of this design is then evaluated with an ICP-MS instrument in the analysis of the several NIST standard reference material of milk 1849a, rice flour 1568b, spinach leave 1570a and Peach Leaves 1547 in a domestic microwave oven with inverter technology. Outstanding agreement to (SRM) values are observed by using the suggested power to time microwave program, which simulates the reflux action occurring in this closed vessel. Taking into account the high cost of commercial microwave vessels and the volume of chemicals needed for various experiments (8-10 mL), this simple vessel is cost effective and suitable for digesting food and environmental samples.
    Matched MeSH terms: Butadienes
  16. ENR-50 compatibilized natural rubber/recycled acrylonitrile-butadiene rubber blends
    Hazwani Syaza Ahmad, Hanafi Ismail, Azura Abd Rashid
    Sains Malaysiana, 2015;44:835-842.
    Epoxidized natural rubber (ENR-50) has been used as a compatibilizer for natural rubber-recycled acrylonitrile-butadiene
    rubber (NR/NBRr) blends, vulcanized by sulfur. NBR gloves have excellent resistance to punctures, tear and many types
    of chemicals, while NR has good physical and mechanical properties. Incorporation of ENR-50 into the rubber blends
    has improved processability, stiffness, resilience and excellent oil resistance. NR/NBRr blends were prepared by two-roll
    mill with five different compositions with the ENR-50 content fixed at 10 phr. Cure characteristics, mechanical properties
    and morphology (SEM) studies were performed to determine the compatibility of NR/NBRr blends in the presence of ENR-
    50. The cure characteristics showed that NR/NBRr blends with the presence of ENR-50 have lower scorch time (ts2) and
    cure time (t90) than NR/NBRr blends without ENR-50. However, the NR/NBRr blends with ENR-50 exhibited higher minimum
    torque (ML
    ) and maximum torque (MH) which indicated difficult processability of the blends after compatibilization.
    Incorporation of ENR-50 into NR/NBRr blends improved all the tensile properties (tensile strength, tensile modulus and
    elongation at break) compared with NR/NBRr blends without ENR-50. The improvement in hardness upon compatibilization
    is due to an increase in crosslink density. Scanning electron microscopy (SEM images) of the fracture surfaces indicates
    that, with the addition of ENR-50 in NR/NBRr blends, better adhesion between NR and NBRr was obtained, thus improving
    the compatibility of NR/NBRr blends.
    Matched MeSH terms: Butadienes
  17. Fulltext Effect of Printing Parameters on Tensile, Dynamic Mechanical, and Thermoelectric Properties of FDM 3D Printed CABS/ZnO Composites
    Aw YY, Yeoh CK, Idris MA, Teh PL, Hamzah KA, Sazali SA
    Materials (Basel), 2018 Mar 22;11(4).
    PMID: 29565286 DOI: 10.3390/ma11040466
    Fused deposition modelling (FDM) has been widely used in medical appliances, automobile, aircraft and aerospace, household appliances, toys, and many other fields. The ease of processing, low cost and high flexibility of FDM technique are strong advantages compared to other techniques for thermoelectric polymer composite fabrication. This research work focuses on the effect of two crucial printing parameters (infill density and printing pattern) on the tensile, dynamic mechanical, and thermoelectric properties of conductive acrylonitrile butadiene styrene/zinc oxide (CABS/ZnO composites fabricated by FDM technique. Results revealed significant improvement in tensile strength and Young's modulus, with a decrease in elongation at break with infill density. Improvement in dynamic storage modulus was observed when infill density changed from 50% to 100%. However, the loss modulus and damping factor reduced gradually. The increase of thermal conductivity was relatively smaller compared to the improvement of electrical conductivity and Seebeck coefficient, therefore, the calculated figure of merit (ZT) value increased with infill density. Line pattern performed better than rectilinear, especially in tensile properties and electrical conductivity. From the results obtained, FDM-fabricated CABS/ZnO showed much potential as a promising candidate for thermoelectric application.
    Matched MeSH terms: Butadienes
  18. Fulltext The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land-use change and air quality
    Pyle JA, Warwick NJ, Harris NR, Abas MR, Archibald AT, Ashfold MJ, et al.
    Philos Trans R Soc Lond B Biol Sci, 2011 Nov 27;366(1582):3210-24.
    PMID: 22006963 DOI: 10.1098/rstb.2011.0060
    We present results from the OP3 campaign in Sabah during 2008 that allow us to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NO(x) emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere.
    Matched MeSH terms: Butadienes/chemistry
  19. Fulltext Effects of land use on surface-atmosphere exchanges of trace gases and energy in Borneo: comparing fluxes over oil palm plantations and a rainforest
    Fowler D, Nemitz E, Misztal P, Di Marco C, Skiba U, Ryder J, et al.
    Philos Trans R Soc Lond B Biol Sci, 2011 Nov 27;366(1582):3196-209.
    PMID: 22006962 DOI: 10.1098/rstb.2011.0055
    This paper reports measurements of land-atmosphere fluxes of sensible and latent heat, momentum, CO(2), volatile organic compounds (VOCs), NO, NO(2), N(2)O and O(3) over a 30 m high rainforest canopy and a 12 m high oil palm plantation in the same region of Sabah in Borneo between April and July 2008. The daytime maximum CO(2) flux to the two canopies differs by approximately a factor of 2, 1200 mg C m(-2) h(-1) for the oil palm and 700 mg C m(-2) h(-1) for the rainforest, with the oil palm plantation showing a substantially greater quantum efficiency. Total VOC emissions are also larger over the oil palm than over the rainforest by a factor of 3. Emissions of isoprene from the oil palm canopy represented 80 per cent of the VOC emissions and exceeded those over the rainforest in similar light and temperature conditions by on average a factor of 5. Substantial emissions of estragole (1-allyl-4-methoxybenzene) from the oil palm plantation were detected and no trace of this VOC was detected in or above the rainforest. Deposition velocities for O(3) to the rainforest were a factor of 2 larger than over oil palm. Emissions of nitrous oxide were larger from the soils of the oil palm plantation than from the soils of the rainforest by approximately 25 per cent. It is clear from the measurements that the large change in the species composition generated by replacing rainforest with oil palm leads to profound changes in the net exchange of most of the trace gases measured, and thus on the chemical composition of the boundary layer over these surfaces.
    Matched MeSH terms: Butadienes/chemistry
  20. Fulltext The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo
    MacKenzie AR, Langford B, Pugh TA, Robinson N, Misztal PK, Heard DE, et al.
    Philos Trans R Soc Lond B Biol Sci, 2011 Nov 27;366(1582):3177-95.
    PMID: 22006961 DOI: 10.1098/rstb.2011.0053
    We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are dominated by isoprene and its oxidation products, with a significant additional contribution from monoterpenes. Rather than consuming the main atmospheric oxidant, OH, these high concentrations of VOCs appear to maintain OH, as has been observed previously over Amazonia. The boundary-layer characteristics and mixing ratios of VOCs observed over the Borneo rainforest are different to those measured previously over Amazonia. Compared with the Bornean rainforest, air over the oil palm plantation contains much more isoprene, monoterpenes are relatively less important, and the flower scent, estragole, is prominent. Concentrations of nitrogen oxides are greater above the agro-industrial oil palm landscape than over the rainforest, and this leads to changes in some secondary pollutant mixing ratios (but not, currently, differences in ozone). Secondary organic aerosol over both landscapes shows a significant contribution from isoprene. Primary biological aerosol dominates the super-micrometre aerosol over the rainforest and is likely to be sensitive to land-use change, since the fungal source of the bioaerosol is closely linked to above-ground biodiversity.
    Matched MeSH terms: Butadienes/chemistry
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