Chemistry of size-segregated particles: study of sources and processes in N-NW India

Özet

PM0.95,PM0.95-1.5,PM1.5-3.0,PM3.0-7.2and PM7.2-10particles were collected simultaneously during summer seasonfrom Bikaner (BKR), Jhunjhunu (JHJ) and New Delhi (DEL) located in windward direction of south-westerlywinds in north-northwestern, India and studied for mass concentrations and water-soluble inorganic ions(WSIIs). Organic carbon (OC) and elemental carbon (EC) were analyzed only for PM0.95. Particle mass con-centrations, size distribution of WSIIs/elements suggested that winds selectively picked PM0.95and PM3.0-7.2from BKR and transported them downwind (DEL). Variations in WSIIs and elements were specific to ion/ele-ment, particle size and location(s). Secondary inorganic ions (SIN; NO3−,SO42−,NH4+) and Ca2+weredominant ions compared to other ions and PM0.95carried high WSIIs compared to other particles at all locations,due to more SIN formation in PM0.95. OC and EC increased significantly from BKR to DEL due to increasingcombustion sources. Char-EC was more than soot-EC at all locations. Re-suspension of roadside/surface dust, andbiomass burning were potentials sources of OC. Volatile organic compounds at DEL have resulted in formation ofhigh secondary organic carbon. Major elements (MEs; Al, Ca, Fe, Mn, Ti) and trace elements (TEs; Ba, Sr, Zn, Cu,Cr, Pb, Co, Cd) were enriched in PM0.95compared to other particles. Silica dilution effect resulted in lowerenrichment ratios (ERs) of MEs with respect to Upper Continental Crust (UCC) whereas anthropogenic con-tributions for TEs, more in PM0.95, resulted in higher ERs. Homogenization effects on particle loading andcomposition were observed at BKR whereas lowering of wind speed and anthropogenic sources introducedheterogeneity at DEL.