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Title:	Perubahan aktiviti 210pb dan 210po dalam atmosfera-permukaan laut di Malaysia: suatu penjelasan mengenai status struktur biogeokimia dan produktiviti marin
Authors:	Asnor Azrin Sabuti (P54874)
Supervisor:	Che Abd Rahim Mohamed, Prof. Dr.
Keywords:	Biogeokimia Produktiviti marin Biogeochemistry
Issue Date:	6-Jan-2013
Description:	Pengukuran kepekatan aktiviti radionuklid semulajadi (210Pb dan 210Po) dan unsur surih telah dilakukan terhadap sampel aerosol (partikel terampai berdiameter kurang daripada 10 μm atau PM10 dan jumlah partikel terampai atau TSP) dan air hujan di sekitaran maritim, serta air laut yang diperolehi semasa Ekspedisi Pelayaran Saintifik Perdana 2009 (EPSP'09) dan di Stesen Meteorologi Mersing pada tahun 2009 hingga 2010. Analisis terhadap sampel adalah menggunakan kaedah penghadaman, pemisahan dan penulenan, sebelum diukur dengan alat spektrometri alfa buatan Canberra Inc., model Alpha Analyst dan pembilang gros alfa/beta buatan Canberra Inc., model XLB-5 Tennelec® Series 5 bagi pengukuran radionuklid semulajadi dan alat inductively coupled plasma-mass spectrometry (ICP-MS) buatan PerkinElmer model ELAN® 9000 bagi pengukuran unsur surih. Hasil daripada aktiviti radionuklid semulajadi yang diperoleh mendapati, nisbah aktiviti 210Po/210Pb di dalam air laut adalah tinggi (antara 3.48 ± 1.06 hingga 13.08 ± 3.78). Ini dijelaskan oleh input 210Po daripada atmosfera yang tinggi, terutamanya apabila berlakunya fenomena jerebu yang dicirikan dengan nisbah fluks endapan 210Po/210Pb yang tinggi di dalam TSP (antara 0.48 ± 0.23 hingga 6.65 ± 0.93). Variasi mengikut masa bagi aktiviti 210Pb dan 210Po dan kepekatan unsur surih (Al, Ca, Fe, Mn, K, Ba, Na, Mg, Cr, Co, Pb, Cu, Ni, Cd dan Cr) di dalam atmosfera berkemungkinan terhasil daripada kepelbagaian kandungan bahan-bahan semulajadi dan antropogenik yang dibawa melalui jasad udara yang tentunya dikawal oleh sistem monsun. Kitaran tahunan bagi kepekatan PM10 dan aktiviti 210Pb dan 210Po di Mersing dapat dicirikan dengan profil naik-turun secara dwi-mod dengan peningkatan pada kedua-dua monsun ketika Januari-Mac dan Mei-September. Ciri dwi-mod ini dikenalpasti berpunca daripada bawaan jasad udara ke sekitar perairan Malaysia daripada arah utara melalui angin timuran dan timur laut semasa monsun timur laut dan jasad udara dari arah selatan melalui angin selatan dan barat daya semasa monsun barat daya. Pengaplikasian kaedah statistik multivariat melalui Positive Matrix Factorization (PMF) menggunakan perisian EPA PMF 3.0 terhadap data unsur surih yang diperolehi telah berjaya mengesahkan empat sumber penting yang utama di dalam PM10; kebakaran biojisim seperti hutan dan tanah gambut, emisi minyak dan gas daripada industri dan kenderaan, debuan daripada daratan, dan sebahagian kecil sumber tambahan yang tidak dapat dikenalpasti. Sumber endapan atmosfera ini merupakan komponen penting bagi pencirian komposisi 210Pb dan 210Po di permukaan laut yang telah merekodkan purata fluks yang lebih tinggi (330 ± 161 dan 605 ± 384 mBq/m2/hari, masing-masing) berbanding lautan utama yang lain. Namun begitu, lebihan-210Po (210Poex) dalam air laut yang direkodkan bagi kajian ini berbanding penyusutan-210Po (210Podef) bagi kajian di lautan yang lain mungkin disebabkan kadar penghasilan baharu (new production rate) yang rendah di Laut China Selatan. Hasil ini juga disokong dengan hasil eksport karbon yang rendah bagi Laut China Selatan yang dianggar menggunakan 210Po sebagai proksi di dalam kajian ini dengan julat antara 72 ± 59 mgC/m2/hari hingga 309 ± 66 mgC/m2/hari dengan purata 161 ± 93 mgC/m2/hari,Measurements of natural radionuclide (210Pb and 210Po) activity and trace element concentrations have been made to the maritime aerosol (particulate matter with diameter less than 10 μm or PM10 and total suspended particles or TSP) and rainwater, together with the seawater samples that were collected during Prime Marine Scientific Expedition 2009 (EPSP'09) and at Mersing Meteorological Station between 2009 to 2010. Samples were analyzed using digestion, separation and purification methods prior to measurements via alpha spectrometry made by Canberra Inc., model Alpha Analyst and gross alpha/beta counter made by Canberra Inc., model XLB-5 Tennelec® Series 5 for the radionuclides and inductively coupled plasma-mass spectrometry (ICP-MS) made by Perkin Elmer model ELAN® 9000 for trace elements. The collected radionuclide activities were resulting high 210Po/210Pb activity ratios in seawater (between 3.48 ± 1.06 to 13.08 ± 3.78). This could be explained by considerably high 210Po atmospheric input, especially during haze events signalled with high 210Po/210Pb depositional flux ratios in TSP (between 0.48 ± 0.23 to 6.65 ± 0.93). The temporal variations of 210Pb and 210Po activities, and trace element (Al, Ca, Fe, Mn, K, Ba, Na, Mg, Cr, Co, Pb, Cu, Ni, Cd and Cr) concentrations in the atmosphere may have resulted from the variability of natural and anthropogenic substances brought by air mass transport which mainly controlled by monsoon systems. The annual cycle of PM10 concentrations in Mersing was marked with bimodal temporal fluctuations with peaks during both monsoons in January-March and in May-September. The bimodal characteristic was identified by the air mass brought to the Malaysian seas from the northern source by predominantly easterly and northeasterly winds during northeast monsoon and the southern source brought by predominantly southerly and southwesterly winds during southwest monsoon. Application of multivariate statistical methods via Positive Matrix Factorization (PMF) using EPA PMF 3.0 software to the collected trace elements data has yielded four physically meaningful PM10 sources: biomass fires from forest and peat bog, oil and gas emissions from industries and vehicles, continental soil dust, and considerable amounts of additional/unidentified input. The atmospheric deposition source is one important component for characterizing the 210Pb and 210Po at surface seawater composition which has recorded higher mean atmospheric flux (330 ± 161 dan 605 ± 384 mBq/m2/day, respectively) compared to other major oceans. However, the 210Po excess (210Poex) in seawater exhibited in this study compared to 210Po deficiency (210Podef) in the other oceans studies are probably due to low new production in the South China Sea. This finding is also supported by low carbon export production in South China Sea estimated by 210Po proxy in this study that lies between 72 ± 59 mgC/m2/day to 309 ± 66 mgC/m2/day with average 161 ± 93 mgC/m2/day mgC/m2/day.
Pages:	223
Call Number:	QC795.34.A847 2014 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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