Study on Airborne Heavy Metals in Industrialized Urban Area of Delhi, India

This study assessed the concentrations of airborne heavy metals (HMs) in particulate matter with a cutoff size of 10 µm (i.e., PM₁₀) in an industrialized urban area (Naraina Industrial Area) of New Delhi, India. The samples were collected from January to December, 2011. The annual mean concentrations of selected HMs were as follows As (0.002 ± 0.002), Cd (0.030 ± 0.020), Co (0.003 ± 0.002), Cr (0.170 ± 0.081), Cu (0.183 ± 0.120), Fe (4.774 ± 1.889), Mn (0.258 ± 0.145), Ni (0.170 ± 0.146), Pb (0.345 ± 0.207) and Zn (1.806 ± 1.042) µg/m³. The seasonal trend for HMs followed the order postmonsoon > winter > premonsoon > monsoon. Principal component analysis-multiple linear regression (PCA-MLR) suggested the three major emission sources: industrial emission (70 %), mobile and stationary combustion sources (16 %), and suspended/re-suspended dust (14 %). Mean seasonal concentrations of PM₁₀ exceeded both the 24-hour and annual Indian National Ambient Air Quality Standards (NAAQS) of 60 and 100 µg/m³, respectively, in all four seasons. Mean seasonal Ni concentrations in Delhi ambient air also exceeded the 24-h annual NAAQS of 0.020 µg/m³ during all four seasons. Mean Pb concentrations exceeded the annual NAAQS of 0.50 µg/m³ only during the post monsoon season. The high levels of Ni- and Pb-contaminated PM₁₀ would appear to present the possibility of significant health risks.