Abstract

The atmospheric concentration of SO2 was monitored in two different locations, Khulna and Savar by using passive samplers. The work was carried out as a part of the RAINS-ASIA Project funded by the World Bank and the Asian Development Bank. The sulphur dioxide monitoring program was funded by the Asian Development Bank. Sulphur dioxide was monitored at the surface for a twelve month period in 45 locations of 11 different countries of Asia under this project including two stations in Bangladesh. Sulphur dioxide was monitored using passive samplers which were developed at the Swedish Environmental Research Institute by Dr. Mertin Ferm. This samplers offer a low-cost means of obtaining long term ambient average sulphur dioxide concentration. A sampler cost about 35 US Dollar. This can be used to obtain weekly to monthly average sulphur dioxide levels. This technique has been used extensively in Asia and Europe and has proven to be accurate and reliable.

The annual mean value in different locations of Asia ranged from less than 0.3 mg/m3 (Malaysia) to more than 20 mg/m3 (China). The results from two sampling locations of Bangladesh show that the annual mean value is higher than some countries of Asia. The results were found to display a distinct seasonal cycle which is strongly influenced by the wind and precipitation patterns. It has been observed that the winter concentrations of S02 in Khulna is 3 -to 4 times higher than the summer concentrations. The winter S02 concentrations of Khulna is also higher compared to Savar. Based on these facts and seasonal wind flow pattern, trans-boundary air pollution with respect to sulphur dioxide has been suggested. Khulna is in the south-western part of Bangladesh and this area harbours the Sunderbans, largest mangrove forest of the world where sundari trees are the main tree species. For the last few years, thousand of this trees, which are quite susceptible of pH stress, are dying from the top. The unusual winter increase of sulphur dioxide has been assigned to be one of the reasons for the top-dying of Sundaris. Other factors might be the increase of salinity and diminished water flow.