Physico-chemical characterization of street dust and re-suspended dust on plant canopies: An approach for finger printing the urban environment

Levels of air pollution can be assessed through passive and active monitoring. However, due to several drawbacks of active monitoring recently much emphasis is being given to the passive monitoring of air-pollution. Street dust and the dusts deposited over the leaves of roadside trees can be considered a valuable indicator of environmental pollution. Present study was undertaken to analyze the size distribution and investigate the elemental and mineralogical components of the street dusts and the dusts deposited on the leaves of roadside trees. Samples were collected from three representative areas of metro-city Kolkata, India, considering the urban characteristics and traffic profile. X-ray powder diffraction (XRD) was selected to detect major mineral components. The size distribution of dust particles was observed under scanning electron microscope (SEM) and the elemental distribution was analyzed using SEM attached to energy dispersive X ray spectrometer (SEM-EDX). X-ray diffraction analysis has revealed the presence of mineral components like quartz and various clay minerals such as calcite, gypsum, albite, microcline, chlorite, muscovite and oxides of iron. Elemental analysis has shown the presence of elements like Na, Mg, Al, Si, Cl, K, Ca, Fe, and Zn. Variations in size, mineral and elemental composition were observed. From the study it is evident that the information on mineralogical and elemental composition of street dusts and dusts deposited on the leave surfaces of roadside trees can act as indicator of air-pollution.