Chemical Characteristics of Fine and Coarse Particles during Wintertime over Two Urban Cities in North India

Received: February 8, 2018
Revised: March 29, 2018
Accepted: March 30, 2018
Download Citation: RIS|BibTeX|https://doi.org/10.4209/aaqr.2018.02.0051  

Cite this article:
Kumar, S., Nath, S., Bhatti, M.S. and Yadav, S. (2018). Chemical Characteristics of Fine and Coarse Particles during Wintertime over Two Urban Cities in North India. Aerosol Air Qual. Res. 18: 1573-1590. https://doi.org/10.4209/aaqr.2018.02.0051

HIGHLIGHTS

• PM_2.5/PM_2.5-10 mass ratios were 2.9 and 3.6 over AMS and DEL.
• PM_2.5 had more ∑WSIIs than PM_2.5-10, SSI dominates among all ions at both sites.
• ERs for Pb, Cu and Zn in PM_2.5 were 63, 18 and 13 over DEL and 2, 11 and 31 over AMS.
• CD value of > 0.5 indicated spatial heterogeneity in PM_2.5 and PM_2.5-10 chemistry.
• Sources differ among PM_2.5 & PM_2.5-10 and among the sampling sites.

ABSTRACT

ABSTRACT

Water-soluble inorganic ions (WSII), organic carbon (OC) and elemental carbon (EC), and metals in the residue of the water-soluble fraction were studied in fine (PM_2.5) and coarse (PM_2.5-10) particles during winter over two urban cities, Amritsar (AMS) and New Delhi (DEL), in northern India. The PM_2.5/PM_2.5-10 mass ratios at DEL and AMS were 3.6 and 2.79, respectively. ∑WSIIs was nearly 25% of the total mass in two size fractions and was higher in PM_2.5 than PM_2.5-10 at both sites. The secondary ions SO₄²⁻ and NH₄⁺ were dominant at both sites. The adsorption of fine particles onto larger ones may be a possible source of soluble ions in PM_2.5-10. SO₄²⁻ and NO₃⁻ were neutralized by NH4+, and the formation of (NH₄)₂SO₄ dominated over NH₄NO₃ in PM_2.5, and by Ca²⁺ in PM_2.5-10 over DEL. Coal burning, and agricultural and livestock emissions were potential sources of precursor gases of SO₄²⁻ and NH₄⁺. Plastic burning and the brick kiln industry contributed Cl⁻ in the PM_2.5. OC dominated over EC above both sites, and the total carbon (OC + EC) was higher over AMS than DEL. Emissions from low-temperature rather than high temperature combustion processes were dominant, as indicated by the higher quantity of char-EC than soot-EC. OC, EC, and K⁺ resulted from biomass burning over AMS, whereas they originated in multiple sources over DEL. The Al normalized ratios of elements in the samples compared to the crust were higher in PM_2.5 than PM_2.5-10. Fe, Ti, and Mn ratios of < 1 were attributed to the silica dilution effect. The Pb, Cu, and Zn ratios in PM_2.5 were 63, 18, and 13 over DEL and 2, 11, and 31 over AMS, respectively. Ba and Zn were contributed by vehicular emissions. A coefficient of divergence of > 0.5 indicated the spatial heterogeneity in the particle chemistry between the two sites. To improve the air quality and safeguard human health, biomass burning and the re-suspension of dust must be restricted.

Keywords: Aerosols; Sources; Processes; Transport; Biomass burning.