Geo-environmental approach to assess heavy metals around auto-body refinishing shops using bio-monitors

The vehicular industry is looking for continuous challenges to develop the sustainability of its manufacturing, maintenance processes, and vehicle emissions due to marketability, environmental, economic, and policy concerns. The present study focuses on the impact of these processes on the environment. In Pakistan, most of the auto-body refinishing processes are carried out in an open atmosphere. The shades of Azadirachta indica (Neem Tree) are generally used for the outdoor practice of scrapping, grinding, and painting in auto-body refinishing shops of Pakistan. Azadirachta indica leaves were selected as bio-indicator. For the present work, 26 affected sites and 10 control sites were selected from Karachi city, which is the financial hub and biggest city of Pakistan. Concentrations of different metals (Fe, Co, Cd, Cr, Cu, Mn, Mo, Ni, Pb, and Zn) were determined by atomic absorption spectrophotometer. A geographic information system (GIS) is used to present the variation in concentrations within Karachi city. The only positive correlation was observed in Pb and Mn (0.750). Principal component analysis (PCA) is applied to identify the anthropogenic effect between auto-body refinishing areas and control areas. Almost all analyzed metals show higher concentration at affected sites but Pb (87.14 mg/kg), Mn (46.47 mg/kg) and Fe (146.95 mg/kg) were leading the values, as compared to their concentration at control sites, Pb (48.83 mg/kg), Mn (15.23 mg/kg) and Fe (43.07 mg/kg). All analyzed metals are frequently present in different color pigments, whereas Pb, Mn, and Fe may also come from other sources, like the anti-knocking agent, vehicular exhaust, and scraping of car surface.