Chemical Composition and Source Characterization of Hailstones in Dhaka, Bangladesh

A comprehensive analysis on the chemical composition and source apportionment of hailstone samples were conducted in Dhaka, Bangladesh. pH, electrical conductivity (EC), total dissolved solids (TDS), water soluble ions (Na+, K+, Ca2+, Mg2+, Cl-, SO42-, NO3-, HCO3-) and trace metals (Zn, Fe, Cu, Mn) of hailstone were determined. The result revealed that the average pH, EC, TDS were 6.95 ± 0.54, 356.3 ± 150.6 μS·cm-1 and 17.5 ± 2.89 mg·L-1, respectively. The water soluble ions followed the order: Ca2+ > Cl-1 > SO42- > HCO3- > Na+ > Mg2+ > K+ > NO3-. The concentrations of trace metals ranged in order with Zn > Fe > Cu, while the concentration of Mn was below detection limit. Sodium adsorption ratio (SAR) was 0.20 ± 0.09 meqL-1 which indicates it is benign to plants and safe for irrigation. The order of neutralization factor (calculated with average concentrations) found in hailstone was NFCa(1.16) > NFMg (0.36) > NFK(0.32) which were originated from earth crust. Notable correlation was found in between soil tracers Ca2+ and Mg2+ (r = 0.87), indicating their common source dust. Enrichment factor analysis revealed that Ca2+, Mg2+ and K+ are mainly from crust, whereas NO3- and SO42- are mainly attributable to anthropogenic origins. Further source contribution analysis revealed that anthropogenic actions accounted for 99.2% of total NO3- and 89.6% of total SO42-, while 99.2% of total Ca2+ and 95% Mg2+ were from crustal source.

Emission of Carbonaceous Species from Biomass Burning in the Traditional Rural Cooking Stove in Bangladesh

Characterization of carbonaceous species from the particulate matters (PM) after combustion of seven commonly used biomass species, albizia tree (Albizia julibrissin), dry leaves (mahogany tree), jackfruit tree (Artocarpus heterophyllus), rain tree (Samanea saman), mahogany tree (Swietenia mahogany), cow dung and mango tree (Mangifer aindica) was done. PM samples were collected on quartz fiber filters emitted from biomass burning in a typical rural cooking stove. PM loaded filters were characterized with scanning electron microscope (SEM) for surface morphology, fourier transform infrared (FTIR) to determine the functional group of organic compounds. Black carbon (BC) and brown carbon (BrC) concentrations were determined with Aethalometer. A TOC analyzer was used to determine the total organic carbon (TOC) present in the biomass samples. The surface morphology was almost similar for all biomass burning PM samples. The average concentrations of BC and BrC were 5.85 ± 4.40 and 13.0 ± 8.80 μg·m&#453, respectively. The emission factors of BC and BrC were 1.08 ± 0.89 and 2.35 ± 1.67 mg·g&#451, respectively. Concentration of BC was the highest in dry leaves and the lowest in mango tree. The emission factors of the determined biomass followed the sequence-dry leaves of mahogany > albizia tree > jackfruit tree > rain tree > cow dung > mahogany tree > mango tree. PM from mango tree had lower emissions compared to the other biomass species used in this study.