Spatial Footprint Distribution of Some Heavy Metals in Major Transport Routes in Ramadi City – Iraq

Abstract

The rapid growth of urban areas and industry in cities located in the arid parts of the world has caused the buildup of significant amounts of heavy metals (HMs) in road dust. Industrial activity has produced an excess of HMs in urban areas that results in significant risks to the environment and human health, despite being overlooked by most. This study aims to assess the accumulation of HMs (Zn, Cu, Cr, Pb, and Cd) in roadside dust and the degree of bioaccumulation in native vegetation of Ramadi City, Iraq. Duplicates of roadside dust samples and roadside vegetation were collected from each of the following five sites: highway, industrial, mixed, and residential, along with one control location that had no known industrial activity. The samples were digested with a tri-acid, and the concentrations of the HMs of interest were obtained using flame atomic absorption spectroscopy. The concentration data generated from this study were assessed using a combination of geochemical indices, including the Geo-accumulation Index (Igeo), Pollution Load Index (PLI), Degree of Contamination (CD), Potential Ecological Risk Index (PERI), and Integrated Pollution Index (IPI). The efficiency of plants for absorbing the HMs from roadside dust was estimated using the Bioconcentration Factor (BCF). Statistical analysis has established a pollutant gradient of industrial pollution versus highway pollution versus mixed road and residential area pollution and indicated significant anthropogenic enrichment (P ≥ 0.01). The PERI classification system categorized each road type as “high risk”. The levels of hazardous metals in plant tissue were reported in the following abundance order: Zn > Cr > Cu > Pb > Cd; both Cd and Cr exceeded the maximum safety levels. The BCFs of local vegetation indicated that they served as excluders of hazardous metals rather than hyper-accumulators. The high aridity of the climate in Ramadi city intensifies contamination as it hinders the dilution of hazardous metals and aids in the aeolian travel of metal-laden particulate matter (a halo effect) through industrial areas to residential areas, and highlights the need for immediate source control. This study provides a replicable multi-index method for the assessment of hazardous metals pollution in other rapidly urbanizing and arid cities in the Middle East. Furthermore, roadside plants are actively transferring these road dust contaminants down into lower levels of the food chain. If road dust is not systematically mitigated, long-term health effects from nephrotoxic, neurodevelopmental, and carcinogenic risks will likely occur.