Lin Chin Yik

University of Malaya

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Haris Hafizal Abd Hamid

National University of Malaysia

Mohd Shahrul Mohd Nadzir

National University of Malaysia

Mohd Talib Latif

National University of Malaysia

Md Firoz Khan

North South University

Mazrura Sahani

National University of Malaysia

Khairul Nizam Abdul Maulud

National University of Malaysia

Muhammad Ikram A. Wahab

National University of Malaysia

Hossain Mohammad Syedul Hoque

Mohd Fadzil Firdzaus Mohd Nor

University of Malaya

Wan Shafrina Wan Mohd Jaafar

National University of Malaysia

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National University of Malaysia

University of Malaya

National Institutes of Biotechnology Malaysia

Universiti Malaysia Terengganu

University of Technology Malaysia

Malaysian Palm Oil Board

University Kebangsaan Malaysia Medical Centre

Universiti Putra Malaysia

Universiti Teknologi MARA

Sultan Zainal Abidin University

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Volatile Organic Compound Analysis by Sorbent Tube-Thermal Desorption-Gas Chromatography: A Review

International Journal of Engineering & Technology (2018)

Md Firoz Khan Mazrura Sahani Mohd Shahrul Mohd Nadzir Lin Chin Yik Hossain Mohammad Syedul Hoque

Volatile organic compounds (VOCs) play an important role in the generation of ground level ozone and secondary organic aerosol. Most tropical countries such as Malaysia, Singapore, Indonesia, Brunei experience high ozone pollution. Beside ozone, oxides of nitrogen (NOx) from vehicular emissions also play an important role in photochemical pollution. NOx, particularly nitric oxide (NO), helps to ‘clean up’ ozone concentrations close to traffic in the ambient air of urban areas. Thus, knowledge of the chemistry of ozone-VOCs-NOx and finding the sources of VOCs are crucial to proceed with an appropriate mitigation strategy. Thus, the detection of ozone precursors and related VOCs is thoroughly discussed. This review finds that the inertness, hydrophobicity, and the effect of the artefact materials are very significant factors to be explored in the selection of the sorbent materials. In the SEA region, relative humidity is relatively high and exceeds 90% during the northeast monsoon. Thus, the hydrophobic properties of the sampling material need careful consideration. Further to the effect of relative humidity (RH), the artefact effect of the material itself is a challenge to be optimized and multi-sorbent material in a single tube could be a viable choice to minimize the effect of the unwanted signal in the spectrum.

Thermal desorption

10.14419/ijet.v7i3.14.16878

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Driving Factors for Isoprene-Surface Ozone and Carbon Dioxide Chemistry Over an Oil Palm plantation in Malaysia

Research Square (Research Square) (2020)

Mohd Shahrul Mohd Nadzir Maggie Chel Gee Ooi Neil RP Harris Conor G. Bolas Sherin Hassan Bran

Abstract Background: Biogenic Volatile Organic Compounds (BVOCs) such as isoprene (C 5 H 8 ) are ozone (O 3 ) precursors that can be emitted at significant concentrations from the oil palm tree ( Elaeis guineensis ). Reactions involving BVOCs can lead to increased levels of surface O 3 which can signiﬁcantly impair air quality and cause crop damage. This study focuses on the link between isoprene, surface O 3 and carbon dioxide (CO 2 ) over an oil palm plantation and the effects of meteorological factors such as temperature and irradiance on the gas concentrations. The mixing ratios of isoprene, surface O 3 and CO 2 were measured using a portable gas chromatograph with a photoionization detector called ‘ iDirac ’, an EcoTech O 3 analyser, and LI-COR, respectively. Atmospheric models were used for measured selected gases estimation and validation purposes. Results: Results showed that isoprene and surface O 3 had maximum daytime mixing ratios of ~25 ppb and ~57 ppb, respectively. CO 2 mixing ratios were high during the night compared to the day, with a maximum night-time ratio of ~883 ppm. It is also showed that suppression of isoprene emissions from plants by high CO 2 concentrations during the night was due to the reduction of dimethylallyl diphosphate (DMADP) in the leaf cells. The meteorological parameters temperature and light intensity were significantly correlated with isoprene and surface O 3 , with r 2 =0.91 and p<0.01 and r 2 =0.87 and p<0.01, respectively. The Model of Emissions of Gases and Aerosol from Nature (MEGAN) estimated emission rates of isoprene from the oil palm plantation are in the range ~5000 to ~7000 μgm -2 h -1 which are higher than previous studies on pristine forest. This information together with the the in-situ measurement information on isoprene emission flux is then fed into the WRF-CMAQ atmospheric chemistry model to study the effect of oil palm plantation expansion over the years (2000 – 2016) on the local atmospheric chemistry. Conclusions: The in-situ of isoprene measurement in oil palm plantation has provided the variations of atmospheric concentration at different time scale which is important in giving information of surface O 3 production. The relationship between isoprene-surface O 3 and CO 2 -isoprene were interconnected at different time and influenced by meteorological factors. The model has discovered regions that are converted into oil palm plantation has experienced rise in isoprene concentration in region that are converted into oil palm plantation, and it even can be carried downwind up to 100 km inland of the emission source.

Isoprene

Mixing ratio

Elaeis guineensis

Atmospheric chemistry

10.21203/rs.3.rs-56420/v1

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Particulate matter (PM2.5) as a potential SARS-CoV-2 carrier

Research Square (Research Square) (2020)

Norefrina Shafinaz Yip Chee Wai Nazlina Ibrahim Zetti Zainol Rashid Norlaila Mustafa

Abstract The rapid spread of the SARS-CoV-2 in the COVID-19 pandemic had raised questions on the route of transmission of this disease. Initial understanding was that transmission originated from respiratory droplet from an infected host to a susceptible host. However, indirect contact transmission of viable virus by fomites and through aerosols has also been suggested. Herein, we report the involvement of fine indoor air particulate with the diameter of ≤ 2.5 µm (PM 2.5 ) as the transport agent of the virus. PM 2.5 was collected over four weeks during a 48 hours measurement intervals in four separate wards containing different infected clusters in a teaching hospital in Kuala Lumpur, Malaysia. Our results indicated highest SARS-CoV-2 RNA on PM 2.5 in the ward associated with a lavatory. We suggest a link between the virus-laden PM 2.5 and the ward’s design. Patients’ symptoms and numbers that govern the magnitude of viral shedding may also influence the number of airborne SARS-CoV-2 RNA on PM 2.5 in an enclosed environment.

Airborne Transmission

Viral Shedding

Pandemic

10.21203/rs.3.rs-33354/v1

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Citations (7)