No abstract

No abstract

No abstract

No abstract

The PM 10 and particles of greater than 10 µm aerodynamic diameter (hence forth referred as PM >10 ) collected over Delhi exceeded the National Ambient Air Quality Standards (100 µg m -3 ) with an annual average of 215 µg m -3 and 495 µg m -3 , respectively. The water soluble inorganic ions (WSII) were higher throughout the year in PM 10 (13.5%) than in PM >10 (5%). SO 4 2-dominated over NO 3 -ions and contributed 54% to the total WSII in PM 10 . NO 3 -and Ca 2+ were dominant ions in PM >10 . NH 4 + during winter and autumn, and Ca 2+ in summer PM 10 samples were the major acid neutralizing species. The WSII showed monthly and seasonal changes. The total carbon (TC = EC + OC) constituted 8.8%-47.8% of total PM 10 mass, and OC and EC varied from 9.91 to 37.06 µg m -3 and 5.42 to 22.23 µg m -3 during the year long sampling period. The SOC contributed more to OC in summers and the char (EC1) dominated over soot (EC2 + EC3) in EC fractions throughout the year. In summer samples, secondary OC (SOC) contributed 81% to OC and the OC/EC ratio was 3.61 suggesting the possible role of mineral dust and high photochemical activity in SOC production. For the eight different fractions, three dominant sources were identified, coal combustion, biomass burning, and motor vehicle exhaust for OC1, OC2 and OC3; vehicle exhaust for OC4, OP, EC2 and EC3; and biomass and coal combustion for EC1. The seasonal changes in the WSII and carbon concentrations in PM 10 and PM >10 are attributed to both the sources and the meteorological conditions in and around the study area.

No abstract

Size distribution, water-soluble inorganic ions (WSII), and organic carbon (OC) and elemental carbon (EC) in size-segregated aerosols were investigated during a year-long sampling in 2010 over New Delhi. Among different size fractions of PM, PM was the dominant fraction (45%) followed by PM (20%), PM (15%), PM (10%), and PM (10%). All size fractions exceeded the ambient air quality standards of India for PM. Annual average mass size distributions of ions were specific to size and ion(s); Ca, Mg, K, NO, and Cl followed bimodal distribution while SO and NH ions showed one mode in PM. The concentrations of secondary WSII (NO, SO, and NH) increased in winters due to closed and moist atmosphere whereas open atmospheric conditions in summers lead to dispersal of pollutants. NHand Cawere dominant neutralization ions but in different size fractions. The summer-time dust transport from upwind region by S SW winds resulted in significantly high concentrations of PM and PM and PM. This indicted influence of dust generation in Thar Desert and its transport is size selective in nature in downwind direction. The mixing of different sources (geogenic, coal combustions, biomass burning, plastic burning, incinerators, and vehicular emissions sources) for soluble ions in different size fractions was noticed in principle component analysis. Total carbon (TC = EC + OC) constituted 8-31% of the total PM mass, and OC dominated over EC. Among EC, char (EC1) dominated over soot (EC2 + EC3). High SOC contribution (82%) to OC and OC/EC ratio of 2.7 suggested possible role of mineral dust and high photochemical activity in SOC production. Mass concentrations of aerosols and WSII and their contributions to each size fraction of PM are governed by nature of sources, emission strength of source(s), and seasonality in meteorological parameters.

No abstract