Elsevier

Chemosphere

Volume 273, June 2021, 129656
Chemosphere

Heavy metal pollution of road dust in a city and its highly polluted suburb; quantitative source apportionment and source-specific ecological and health risk assessment

https://doi.org/10.1016/j.chemosphere.2021.129656Get rights and content

Highlights

  • The level of pollution and risks in suburb was higher than that of urban region.

  • Traffic emission was the main source of pollution in road dust of the suburb.

  • PMF output was integrated into risk indices for source-specific risk assessment.

  • Traffic emission was the main contributor in health risk in the suburb.

  • Contributions of sources in health and ecological risks were different.

Abstract

Sources of heavy metals (As, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in the road dust of Bandar Abbas city, Iran, and its west suburb were apportioned and the related source-specific ecological and health risks were assessed. The level of heavy metal pollution and the related ecological risk for suburban road dust (suburban RD) were far higher than those of urban RD. Accordingly, probabilistic health risk assessment showed no significant health risk in urban region but significant health risk in the suburb, especially for As with cancer risk above 10−4. Source apportionment using positive matrix factorization (PMF) identified lithogenic source (45.9%) and traffic emission (47.6%) as the main sources of heavy metals in urban and suburban regions, respectively. However, the industrial/construction activities showed the main contribution in ecological risk in both regions. On the other hand, the health risks in urban and suburban regions were mainly attributed to lithogenic source (49.7% for non-cancer risk and 36.8% of cancer risk) and traffic emission (69.4% of non-cancer risk and 46.6% of cancer risk), respectively. The sensitivity analysis showed that the Pb and As originated from traffic emission had the most impact on the non-cancer and cancer risks, respectively, in the suburb. Therefore, this study highlighted the concern about traffic emission as a critical heavy metal source in the road dust of Bandar Abbas suburb.

Introduction

Environmental pollution is a matter of great concern worldwide, as the diseases attributed to such pollution are responsible for above 9 million excess deaths worldwide, which is 15 times more than from all wars and other forms of violence combined (Wang et al., 2016; Landrigan et al., 2018). Environment in many urbanized and industrialized areas worldwide suffers from heavy metal pollution. Such pollution is important, because heavy metals are non-biodegradable and toxic, and some of them are classified as carcinogen by the International Agency for Research on Cancer (IARC) (Trujillo-González et al., 2016). Moreover, their concentration may reach critical levels through bioaccumulation along the food chain (Men et al., 2018a).

Among various components of environment, the road dust accumulated on the surfaces of urbanized and industrialized areas may be polluted with high amounts of heavy metals originated from various anthropogenic and natural sources (Liu et al., 2014, 2019; Soltani et al., 2015; Shi and Lu, 2018). Therefore, road dust acts as a sink of heavy metals originated from anthropogenic sources and then could be considered as a good indicator for reflecting the level of environmental pollution in the highly polluted areas. More importantly, human may be exposed to high level of heavy metals through inhalation, ingestion, and dermal contact of road dust and this may result in adverse health effects (Men et al., 2018a; Khademi et al., 2019). Moreover, road runoff may solubilize a large fraction of heavy metals of road dust and transport them toward receiving water bodies, and consequently causing various ecological risks (Liu et al., 2019). Therefore, with respect to the importance of road dust as a sink and carrier of heavy metals, characterizing such pollution and apportioning its sources are essential (Trujillo-González et al., 2016; Men et al., 2019).

To date, most of source apportionment studies on road dust pollution identified the critical sources of pollution just based on the contribution of each source in the pollutant concentration (Pan et al., 2017; Men et al., 2018a, 2019). However, due to different effects or toxic response factors of various heavy metals on ecology and public health, it is essential to identify the most influential sources based on their role in ecological and health risks (Men et al., 2020). Therefore, besides apportioning the sources of heavy metals in road dust, it is essential to assess the contribution of each identified source to the overall ecological and health risks.

The researches on the source-risk apportionment of environmental pollutants have been considered in recent years, but most of them have focused on the source-specific risk of various pollutants in airborne particulate matter (Taghvaee et al., 2018a; Xie et al., 2020; Sun et al., 2021). Lately, the source-specific risk assessment of heavy metals in road dust has also begun and the studies in this field integrated the output of a quantitative source apportionment model like PMF into deterministic risk assessment method (Guo et al., 2020; Men et al., 2020). However, in order to evaluate the influence of various input parameters and source-specific pollutant concentrations on the risk profile, it is essential to perform probabilistic health risk assessment. Accordingly, in a recent study, the probabilistic procedure was applied for the assessment of health risk attributed to various sources of heavy metal in road dust of Beijing. In this study, it was revealed that the carcinogenic risk from each source was significantly sensitive to ingestion rate and skin adherence factor (Men et al., 2021). However, more research is needed to determine the most influential source-specific pollutant concentration and toxicity on the health risk profile through probabilistic health risk assessment.

In recent years, Bandar Abbas, a coastal city in south of Iran, has experienced accelerated urban growth because of its proximity to main commercial seaports and the existence of several industrial zones near it (Dadras et al., 2015). In the west of this city, the largest container seaport of Iran is located and surrounded with some main industries. Such conditions resulted in high heavy-duty diesel traffic in the west suburb road, which runs along the north shore of Persian Gulf. Therefore, the road dust in this region may be loaded with very high levels of heavy metals. This is important in public health and ecological viewpoints, because such pollution may i) be carried towards urban region by prevailing wind which is mainly from west to east, ii) affect the local residences, and iii) be carried toward seawater by stormwater (Carrero et al., 2013) during torrential rains, which is characteristic of this region.

Since the level of heavy metal pollution in the road dust of urban and highly polluted suburban regions may be different, quantitative apportioning the sources and assessing the source-specific ecological and health risks are essential. In this regard, the main aims of this study were the following: i) to assess the heavy metal pollution of road dust in Bandar Abbas and its west suburb and related ecological and health risks, ii) to apportion the overall sources of heavy metals in urban and suburban road dusts using PMF model, iii) to assess the source-specific ecological risk by integrating the PMF model output into a recently developed ecological risk index (NIRI) (Men et al., 2020), and iv) to assess the source-specific health risk by integrating PMF model output into Monte Carlo simulation-based health risk assessment models.

Section snippets

Study area

Bandar Abbas city, with 530 thousand people, and its west suburb, with ∼25 thousand people (local residents and workers), are laid on the north shore of Persian Gulf (27° 07′ to 27° 14′ N and 56° 12′ to 56° 22′ E). This region is an important economic center of Iran, because it involves internationally important seaports and several major nationwide industries. One of these seaports is Shahid Rajaee port complex, which is the sixty-eighth largest port in the world, as 90% of international

General characteristics of heavy metal pollution in road dust

The level of heavy metal pollution of road dust in Bandar Abbas (urban RD) and its west suburb (suburban RD) is summarized in Table 1. The highest concentration of heavy metals in urban and suburban road dusts were assigned to Cu and Mn, respectively, and Zn ranked second in both regions. However, in opposite to Zn, the concentration of Mn in urban region was lower than background, showing the natural origin of this metal in this region. Among the studied metals, the concentrations of Cu and Zn

Conclusion

In this study, the heavy metal pollution of road dust was investigated in Bandar Abbas and its west suburb. It was found that the level of heavy metal pollution in the suburb was far higher than that of urban region. PMF model was used for quantitative source apportioning of heavy metals in road dust of these regions. The main sources of heavy metals in the urban and suburban regions were lithogenic source and traffic emission, respectively. By combining the PMF model output and NIRI, it was

Credit author statement

Mohsen Heidari: Project Administration, Conceptualization, Methodology, Formal analysis, Software, Writing – review & editing, Funding acquisition. Tooba Darijani: Conceptualization, Methodology, Investigation. Vali Alipour: Project administration

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The authors would like to thank the vice Chancellor for Research in Hormozgan University of Medical Sciences (HUMS) for funding this research (Grant No. 960318). Corresponding author is also grateful to the Tarbiat Modares University for providing research support to work on this paper.

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