Dew water chemical composition and source characterization in the IGP outflow location (coastal Bhola, Bangladesh)

Abstract

Dew water samples were collected during the winter season (December, 2014 to January, 2015) at an outflow location from the Indo-Gangetic Plain (IGP) to the Bay of Bengal (Coastal Bhola, Bangladesh). Physical properties of the dew water, including pH and electrical conductivity (EC), were measured. The concentrations of water soluble ions (Cl−, SO4 2−, NO3 −, HCO3 −, Na+, K+, Ca2+, and Mg2+) and trace metals (Zn, Fe, Mn, Cu, Cr, Pd, and Ni) were also measured. Source characterization of the chemical species was done by correlation analysis, enrichment factor analysis, percent source contribution calculation, and air mass trajectory analysis. The average pH and EC of the collected dew water were 6.81 and 154.80 μS cm−1, respectively. The average concentration of SO4 2− and NO3 − was 264.10 and 222.20 μeq L−1, respectively. The concentrations of water soluble ions followed the sequence: Ca2+ > Cl−> SO4 2 > Na+ > NO3 −> Mg2+ > K+ > HCO3 −. The concentrations of trace metals ranged in order with Zn > Fe > Mn > Cu, while the concentrations of Cr, Pb, and Ni were below detection limit in dew water. Regression analysis showed significant correlations among sea, soil, and anthropogenic species. High enrichment factors of SO4 2−, NO3 −, Zn, Mn, and Cu indicates anthropogenic sources. Percent source contribution of different species showed significant anthropogenic contribution for Cl−(1.80%), SO4 2−(83.5%), and NO3 −(99.3%). Air mass trajectory analysis supported that the regional urban pollutions have significant influence on the dew water chemistry at the coastal Bhola, Bangladesh.