Impact of northern and southern air mass transport on the temporal distribution of atmospheric 210Po and 210Pb in the east coast of Johor, Malaysia

Concentration activities of ²¹⁰Pb and ²¹⁰Po in the PM₁₀ were determined to discuss their distribution and chemical behavior in relation to meteorological parameters especially in air mass transport during monsoon events. Marine aerosol samples were collected between January 2009 and December 2010 at the coastal region of Mersing, which is located in the southern South China Sea and is about 160 km northeast of Johor Bahru, as part of the atmosphere–ocean interaction program in Malaysia. About 47 PM₁₀ samples were collected using the Sierra-Andersen model 1200 PM₁₀ sampler over a 2-year sampling campaign between January 2009 and December 2010. Samples were processed using acid digestion sequential extraction techniques to analyze various fractions such as Fe and Mn oxides, organic matter, and residual fractions. While, ²¹⁰Pb and ²¹⁰Po activities were measured with the Gross Alpha/Beta Counting System model XLB-5 Tennelec® Series 5 and the Alpha Spectrometry (model Alpha Analyst Spectroscopy system with a silicon-surface barrier detector), respectively. The distribution activities of ²¹⁰Pb and ²¹⁰Po in the PM₁₀ samples were varied from 162 to 881 μBq/m³ with mean value of 347 ± 170 μBq/m³ and from 85 to 1009 μBq/m³ with mean value of 318 ± 202 μBq/m³, respectively. The analysis showed that ²¹⁰Po activity in our samples lies in a border and higher range than global distribution values due to contributions from external sources injected to the atmosphere. The speciation of ²¹⁰Pb and ²¹⁰Po in marine aerosol corresponds to transboundary haze; e.g., biomass burning especially forest fires and long-range air mass transport of terrestrial dust has enriched concentrations of particle mass in the local atmosphere. The monsoon seems to play an important role in transporting terrestrial dust from Indo-China and northern Asia especially during the northeast monsoon, as well as biogenic pollutants originating from Sumatra and the southern ASEAN region during southwest monsoon events.