Contents lists available at ScienceDirect Ecotoxicology and Environmental Safety journal homepage: www.elsevier.com/locate/ecoenv Modelling benzene series pollutants (BTEX) build-up loads on urban roads and their human health risks: Implications for stormwater reuse safety Nian Hong a,b , An Liu a,b,c, ⁎ , Panfeng Zhu a , Xu Zhao d , Yuntao Guan e , Mengting Yang a,b , Hongyang Wang f a College of Chemistry and Environmental Engineering, Shenzhen University, 518060 Shenzhen, China b Shenzhen Key Laboratory of Environmental Chemistry and Ecological Remediation, 518060 Shenzhen, China c Science and Engineering Faculty, Queensland University of Technology (QUT), Brisbane, Australia d Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China e Research Center of Environmental Engineering and Management, Graduate School at Shenzhen, Tsinghua University, 518055 Shenzhen, China f State Key Laboratory of Environmental Criteria and Risk Assessment，Chinese Research Academy of Environmental Sciences，Beijing 100012, China ARTICLE INFO Keywords: Stormwater reuse Benzene series compounds (BTEX) Stormwater quality Stormwater pollutant processes Artificial neural network ABSTRACT Benzene series compounds (BTEX) are toxic pollutants primarily generated by traffic activities in an urban environment. BTEX pollutants can be deposited (build-up) on urban road surfaces during dry periods and then washed-off into stormwater runoff. Since BTEX pollutants can pose high human health risks, they can undermine stormwater reuse safety after they enter stormwater runoff. In this study, the BTEX pollutants build-up loads on urban road surfaces were investigated in Shenzhen, China. An artificial neural network (ANN) approach and two conventional regression modelling approaches were compared in terms of estimating BTEX build-up loads based on land use related parameters. It was found that the ANN approach had a better performance than the two regression modelling approaches. Additionally, the spatial distribution maps and human health risk map of BTEX pollutants build-up created using the ANN approach can provide a robust visualization platform to identify ‘hot- spot’ areas. These areas have a potential to generate highly BTEX polluted stormwater runoff and hence be inappropriate to be reused. These research outcomes are expected to provide an effective approach for ensuring stormwater reuse safety and a useful guidance for decision-making for stormwater management and water environment protection related urban planning. 1. Introduction Stormwater reuse is receiving an increasing attention in the worldwide since stormwater has been seen as an alternative water re- source, mitigating water shortage issues. In a typical urban environ- ment, urban roads can generate a large amount of stormwater and hence road stormwater is usually collected for reuse (Al-Salaymeh et al., 2011; Sa’d A et al., 2014). However, road stormwater generally consists of a range of pollutants, sourced from frequent traffic activities (Brown and Peake, 2006; Liu et al., 2017; Ma et al., 2017; Mahbub et al., 2011a; Zhao et al., 2011) and many pollutants are toxic. This is because these toxic pollutants can be deposited (build-up) on road surfaces during dry periods and then washed-off into stormwater runoff when rainfall events occur, eventually undermining stormwater reuse safety (Liu et al., 2013; Mahbub et al., 2011b, 2011c, 2011d). Ad- ditionally, past researchers have noted that even volatile pollutants such as benzene series pollutants (BTEX) which include benzene, ethylbenzene, toluene and xylene could also accumulate on road sur- faces. For example, Mahbub et al. (2011b) noted the accumulation loads of toluene, ethylbenzene, meta and para-xylene, and ortho-xylene were 0.189–0.757 μg/m 2 , 0.089–0.413 μg/m 2 , 0.167–0.691 μg/m 2 , and 0.064–0.259 μg/m 2 , respectively. Mahbub et al. (2011d) found that BTEX pollutants can be washed-off by stormwater runoff, resulting in stormwater pollution. Pollutants build-up represents the initial availability of pollutants prior to stormwater wash-off and hence it can indicate the possible maximum pollutant amounts which will enter stormwater runoff during wash-off. In this context, understanding pollutants build-up process is essential to assist on characterising stormwater quality and hence im- proving its reuse. Pollutants build-up has a high spatial variability due to a diversity of anthropologic activities such as traffic and land use (Goonetilleke et al., 2005). For example, commercial and industrial https://doi.org/10.1016/j.ecoenv.2018.08.031 Received 23 March 2018; Received in revised form 16 July 2018; Accepted 8 August 2018 ⁎ Corresponding author at: College of Chemistry and Environmental Engineering, Shenzhen University, 518060 Shenzhen, China. E-mail address: liuan@szu.edu.cn (A. Liu). Ecotoxicology and Environmental Safety 164 (2018) 234–242 0147-6513/ © 2018 Elsevier Inc. All rights reserved. T