Statistical Interpretation of Weekday/Weekend Differences of Ambient Particulate Matter,Vehicular Traffic and Meteorological Parameters in an Urban Region of Kolkata,India

Abstract

An air quality sampling program was designed and implemented to collect data on ambient PM₁₀, TSP, vehicular traffic and meteorological parameters at weekdays and weekends from November 2003 to November 2004 in Kolkata. Educational institutions and most offices and small-scale industries are closed during weekends. Meteorological parameters were measured by the Indian Meteorological Department, Kolkata. Air quality monitoring was performed weekly for 24-h periods at residential (Kasba) and industrial (Cossipore) sites in an urban region of Kolkata and weekday/weekend differences were compared at both the monitoring sites. Significantly higher weekday values of PM₁₀ and vehicular traffic were observed. The daily average PM₁₀ concentrations on weekdays and at weekends were, respectively, 147.7 and 125.5 g·m 3 at the residential site and 212.3 and 186.3 g·m 3 at the industrial site. Corresponding TSP concentrations were 288.4 and 391.9 g·m 3 and 229.6 and 344.9 g/m³. Average traffic flow for weekdays and weekends were 2.3 10⁴ and 1.9 10⁴ vehicles at the residential site and 2.8 10⁴ and 2.4 10⁴ vehicles at the industrial site. There was a strong linear relationship between PM₁₀ and TSP (R² >0.90) during weekdays at the residential site and at weekends at the industrial site. TSP had moderate (R² >0.50) linear relationship with PM₁₀ during weekends at the residential site and good (R² >0.75) linear relationship during weekdays at the industrial site. The Spearman rank correlation coefficient showed that measured particulate pollutants had an inverse correlation with rainfall, temperature and relative humidity at both sites. Average PM₁₀/TSP ratio was moderately correlated (r>0.50) with average vehicular traffic.