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Title:	Isoprene and monoterpenes flux in the tropical air-sea interface
Authors:	Royston Uning (P83537)
Supervisor:	Mohd Talib Latif, Prof. Dr.
Keywords:	Ocean-atmosphere interaction Ocean-atmosphere interaction -- Computer simulation Ocean-atmosphere interaction -- Mathematical models Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	2-Jul-2020
Description:	Photochemistry of the sea surface microlayer (SML) as the air-sea interface releases biogenic volatile organic compounds (BVOC) and potentially modifies oxidative capacity, tropospheric ozone, and secondary organic aerosol formation in the atmosphere. However, little is known about the BVOC sea-to-air fluxes at the air-sea interface and next to no substantial data on the potential controlling factor under in situ condition. The aim of this study was to measure BVOC (isoprene and monoterpenes) sea-to-air fluxes at the air-sea interface. The relationship betwen BVOC sea-to-air fluxes and the SML in association with bulk surface water (BSW), underlying waters (ULW) biological and chemical compositions was also investigated. The measurements of daytime BVOC sea-to-air fluxes were conducted in the southern waters of South China Sea (SCS) in representing tropical region. Newly developed technique consists of a floating flux chamber coupled with sorbent tubes was applied for the fluxes determination. Thermal desorption unit coupled with gas chromatography mass spectrometry (TD-GCMS) was used to analysed BVOC in the laboratory. SML, BSW and ULW were sampled using glass plate technique with the dimension of 3600 cm2, 1 L high-density polyethylene bottle and 10 L Nansen bottle, respectively. The samples were analysed for bacterial abundance (CBC) using spread plate and dissolved organic carbon (DOC) through high-temperature catalytic oxidation method. The enrichment factor (EF) of a substance in SML was expressed by the ratio between the concentrations in SML to the BSW and ULW. This study showed that the mean BVOC sea-to-air fluxes at the air-sea interface in the tropical region were spatially variable and dominated by isoprene with the magnitude of 19.8 ± 7.3 × 107 molec cm-2 s-1 followed by β-pinene: 5.6 ± 2.9 × 107 molec cm-2 s-1, α- pinene: 3.6 ± 2.6 × 107 molec cm-2 s-1 and limonene: 1.9 ± 0.9 × 107 molec cm-2 s-1, respectively. There was a strong and significant positive correlation observed between isoprene and monoterpenes sea-to-air fluxes (r = 0.73, p < 0.01). The mean concentration of CBC CBC concentrations in the SML, BSW and ULW was 1.3 ± 0.4 × 107 CFU L-1, 1.1 ± 0.4 × 107 CFU L-1, and 0.6 ± 0.3 × 107 CFU L-1, respectively. The mean concentration of DOC in the SML, BSW and ULW was 31 ± 2 μmol L-1, 28 ± 2 μmol L-1, and 30 ±3 μmol L-1, respectively. The mean CBC EF for SML/BSW and SML/ULW was 1.4 ±0.8 and 3.2 ± 2.8, respectively. In contrary, the mean DOC EF for SML/BSW and SML/ULW was 1.1 ± 0.21 and 1.1 ± 0.2, respectively. The EF for both CBC and DOC was found to be low and might be due to weak accumulation or mixing dynamic from the BSW and ULW to the SML in this region. Further analysis showed that, there was only weak correlation observed between isoprene and monoterpenes air-sea interface flux and studied SML composition. This suggests substantial amount of released BVOC in this region may happen due to the abiotic processes at the air-sea interface. Overall, this study has provided a new understanding on the level and characteristics of BVOC fluxes at the air-sea interface as well as no potential control based on monitored seawater compositions in this study region.,Certification of Masters/Doctoral Thesis is not available,Ph.D.
Pages:	121
Call Number:	GC190.2.R639 2020 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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