Prospects of green roof technology as a sustainable solution to urban pollution index

This study was conducted to explore the impact of rooftop plantations on local air quality under agro-ecological conditions of Lahore and Faisalabad. An optoelectronic sensing device was used to capture particulate matter concentration, while heavy metal detection was carried out from dust samples collected randomly from different sites with no or varying levels of vegetation cover in comparison to bare roofs. It was revealed that the average particulate suspension rate was 13–24% lower on roof gardens as compared to bare roofs while a higher amounts of heavy metals were detected from bare roof dust samples. Lead was maximum in midtown and baseline areas in both cities, while it was most ubiquitous heavy metal in all locations than zinc, copper and nickel combined. The pollution load index revealed that Lahore has a higher level of pollution load as compared to Faisalabad. Moreover, pollution load index for Lahore is generalized as maximum in midtown (1.64) followed by baseline (1.48), typical roof (0.98), roof garden (0.78) while standard garden has least (0.75). In Faisalabad high pollution load index was recorded in midtown (1.48), baseline line (1.36) and typical roof (1.08) while standard garden and roof garden were scaled under low pollution level with pollution load index of 0.69 and 0.60. Results confirmed that plantation in form of big trees only or plantations with small trees, shrubs, and ground covers were effective in capturing dust and heavy metal compared to areas with no vegetation at all. Conversely, plantation on rooftop was as effective as plantation on ground compared to bare roofs for mitigating pollution load in urban areas. The present study suggested that utilizing roofs in residential and commercial areas of Faisalabad and Lahore could be an efficient strategy to counter air pollution in near future. [Display omitted] •Rooftop vegetation is an effective way to cater poor air quality and vegetation index crisis in living spaces compared to bare roof.•Particulate matter count and heavy metal deposition decreases with increase in elevation.•On elevated surfaces particulate count was 17–61% low than ground areas while vegetation on top showed significant decline in particulate matter count than bare surfaces.•Time of the year and season has prominent impact on suspension of particulate matter in air.