Atmospheric deposition of ~(210)Po and ~(210)Pb in Malaysian waters during haze events

摘要

Biogenic burning as forest fire phenomena occurring from April to August each year in the Sumatra and Borneo islands are major sources of biogenic uranium-thorium decay series in marine systems. 30 samples were collected during the Ekspedisi Pelayaran Saintifik Perdana 2009 cruise (EPSP 2009 cruise) between 12th June and 1st August 2009 from the Straits of Malacca to the Sulu and Sulawesi Seas to study the effect of haze and the monsoon season on the deposition rate of ~(210)Po and ~(210)Pb in Malaysian waters. All samples were spiked with 1 ml of lead [Pb(NO_3)_2; 25 mg ml~(-1)] and 0.05 ml of Polonium-209 tracer (26.08 dpm ml ~(-1)). ~(210)Po activity was determined by auto plating onto silver foil and counting using an alpha spectrometry system (Canberra model Alpha Analyst with a silicon-surface barrier detector). Lead that was collected via electrodeposition, formed lead sulphate (PbSO_4) precipitation. This precipitate was wrapped onto plastic discs and counted for ~(210)Pb beta activity using a gross alpha-beta counting system (Tennelec model LB-5100 low background gas-flowing anti-coincidence alpha/beta counter) after 1 month to allow bismuth ingrowths. The range of ~(210)Po activities varied between 51.08 ± 15.1 and 742.08 ± 220.34 Bq/kg, whereas the activity of ~(210)Pb ranged from 31.10 ± 4.20 to 880.23 ± 123.86 Bq/kg and ~(210)Po/~(210)Pb ratio value varied between sampling stations from 0.19 to 13.77. The contents of ~(210)Po were also statistically positively correlated with the amount of total suspended particulate especially those recorded during heavy haze period events.