This study investigates the concentrations and spatial distribution of toxic heavy metals (Cd, Cu, Pb and Zn) through chemical analysis of rainwater samples, characterized by different land use, emission sources, tra c conditions and population density. The average concentrations at the ve sites were 52.9, 11.8, 14.6 and 0.93 µg l − 1 for Zn, Pb, Cu and Cd, respectively. The concentrations for all heavy metals were signi cantly higher (p < 0.05) at the central and south Tehran areas compared to the west and north, due to different urban characteristics, higher pollution emission rates from tra c and domestic sectors, and local winds patterns developed within the city. High tra c load in the central part of Tehran also escalates the heavy metal concentrations in this region. The signi cant correlations between the studied heavy metals at the ve sites indicate common, local anthropogenic sources. The heavy metal concentrations were higher in spring than in winter, likely associated with dilution processes in winter and the restriction measures due to COVID-19 pandemic. During the lockdown period, a drastic decrease in tra c load was observed in Tehran, con rming that motor vehicles is the main regulatory factor for air pollution and potential toxic elements in the city. be high, indicating common origin from local anthropogenic sources, mainly from the tra c and industrial sectors.Analysis of heavy metals not only in street (road) and airborne dust samples, but also in rainwater (wet deposition) is very important for identi cation of their sources, distribution, solubility and bio-availability characteristics, which determine ecological and human health risks. Current results provided essential preliminary knowledge of rainwater chemistry in Tehran, helping in establishing regulation and mitigation strategies for better control of air pollution and toxic heavy metals. More systematic analysis of wet deposition in Tehran, Iran and in the Middle East is needed for better assessment of rain chemistry, as a way to investigate atmospheric composition.
Declarations AcknowledgementThis article was supported by the University of Zabol (Iran) with grant code (IR-UOZ-GR-0088).