BITS Faculty Publications
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Item Prediction model of the buildup of volatile organic compounds on urban roads(ACS, 2011-04) Goonetilleke, AshanthaA model to predict the buildup of mainly traffic-generated volatile organic compounds or VOCs (toluene, ethylbenzene, ortho-xylene, meta-xylene, and para-xylene) on urban road surfaces is presented. The model required three traffic parameters, namely average daily traffic (ADT), volume to capacity ratio (V/C), and surface texture depth (STD), and two chemical parameters, namely total suspended solid (TSS) and total organic carbon (TOC), as predictor variables. Principal component analysis and two phase factor analysis were performed to characterize the model calibration parameters. Traffic congestion was found to be the underlying cause of traffic-related VOC buildup on urban roads. The model calibration was optimized using orthogonal experimental design. Partial least squares regression was used for model prediction. It was found that a better optimized orthogonal design could be achieved by including the latent factors of the data matrix into the design. The model performed fairly accurately for three different land uses as well as five different particle size fractions. The relative prediction errors were 10–40% for the different size fractions and 28–40% for the different land uses while the coefficients of variation of the predicted intersite VOC concentrations were in the range of 25–45% for the different size fractions. Considering the sizes of the data matrices, these coefficients of variation were within the acceptable interlaboratory range for analytes at ppb concentration levels.Item Sources of hydrocarbons in urban road dust: Identification, quantification and prediction(Elsevier, 2016-09) Goonetilleke, AshanthaAmong urban stormwater pollutants, hydrocarbons are a significant environmental concern due to their toxicity and relatively stable chemical structure. This study focused on the identification of hydrocarbon contributing sources to urban road dust and approaches for the quantification of pollutant loads to enhance the design of source control measures. The study confirmed the validity of the use of mathematical techniques of principal component analysis (PCA) and hierarchical cluster analysis (HCA) for source identification and principal component analysis/absolute principal component scores (PCA/APCS) receptor model for pollutant load quantification. Study outcomes identified non-combusted lubrication oils, non-combusted diesel fuels and tyre and asphalt wear as the three most critical urban hydrocarbon sources. The site specific variabilities of contributions from sources were replicated using three mathematical models. The models employed predictor variables of daily traffic volume (DTV), road surface texture depth (TD), slope of the road section (SLP), effective population (EPOP) and effective impervious fraction (EIF), which can be considered as the five governing parameters of pollutant generation, deposition and redistribution. Models were developed such that they can be applicable in determining hydrocarbon contributions from urban sites enabling effective design of source control measures.Item Rethinking hydrocarbons build-up on urban roads: a perspective on volatilisation under global warming scenarios(Elsevier, 2019-09) Goonetilleke, AshanthaStormwater is viewed as an alternative resource to mitigate water shortages. However, stormwater reuse is constrained due to the presence of many toxic pollutants such as hydrocarbons. Effective mitigation requires robust mathematical models for stormwater quality prediction based on an understanding of pollutant processes. However, the rise in global temperatures will impose changes to pollutant processes. This study has proposed a new perspective on modelling the build-up process of hydrocarbons, with a focus on volatile organic compounds (VOCs). Among organic compounds, VOCs are the most susceptible to changes as a result of global warming due to their volatility. Seven VOCs, namely, benzene, toluene, ethylbenzene, para-xylene, meta-xylene, ortho-xylene and styrene in road dust were investigated. The outcomes are expected to lay the foundation to overcoming the limitations in current modelling approaches such as not considering the influence of temperature and volatility, on the build-up process. A new conceptualisation is proposed for the classical build-up model by mathematically defining the volatility of VOCs in terms of temperature. Uncertainty in the re-conceptualised build-up model was quantified and was used to understand the build-up patterns in the future scenarios of global warming. Results indicated that for the likely scenarios, the variability in VOCs build-up gradually increases at the beginning of the dry period and then rapidly increases after around seven days, while the build-up reaches a near-constant value in a shorter dry period, limiting the variability. These initial research outcomes need to be further investigated given the expected impacts of global warming into the future.Item Uncertainties in the assessment of volatile hydrocarbon pollution of urban stormwater(IAHR, 2019) Goonetilleke, AshanthaAssessing the risk to human health posed by stormwater pollutants is critical, because stormwater is considered as an alternative water resource to mitigate water deficiencies, which is becoming increasingly common around the world. In this context, hydrocarbons with different volatility that are common in the urban environments pose significant human and ecosystems health risks resulting from wash-off into receiving waters during rainfall events. Effective mitigation strategies require reliable stormwater quality modelling approaches incorporated with accurate assessment of uncertainty in stormwater quality predictions. This study employed Bayesian Network modelling to investigate how anthropogenic and climatic factors influence the build-up of particle-bound hydrocarbons, with specific focus on volatile hydrocarbons, and thereby assessed the uncertainty inherent to their build-up process. The study found that volatile hydrocarbons build-up rapidly in the early stage of the antecedent dry period, and volatility plays a key role in the build-up of these pollutants. Significant differences in the temporal variations in build-up could be observed between different seasons. Further, season specific conditions and physico-chemical characteristics of particulates were found to influence the behaviour of volatile hydrocarbons during build-up.Item Influence of physicochemical properties of road dust on the build-up of hydrocarbons(Elsevier, 2019-12) Goonetilleke, AshanthaUnderstanding the factors influencing the build-up behaviour of different pollutants accumulated on urban roads is essential for the implementation of effective stormwater pollution mitigation strategies. Even though a significant knowledge base exists on different factors influencing hydrocarbon build-up, there is a dearth of evidence on how physicochemical properties of road dust influence hydrocarbon build-up. Accordingly, this study investigated the relationships between physicochemical properties of road dust and hydrocarbons associated with different particle size fractions of road dust. Hydrocarbons with different sources of origin in all size fractions showed a significant correlation with different soil constituents of road dust, predominantly with organic matter, amorphous matter, clay minerals and clay forming minerals of feldspars. However, the physicochemical properties influencing the hydrocarbon build-up is different among different particle size fractions. The interactions identified between hydrocarbon compounds and different minerals associated with road dust will contribute to the development of effective stormwater pollution mitigation strategies.Item Creating a hierarchy of hazard control for urban stormwater management(Elsiever, 2019-12) Goonetilleke, AshanthaUrban stormwater reuse is becoming increasingly prevalent to overcome the serious urban water scarcity being experienced around the world. Therefore, the adoption of reliable approaches to minimise the human health risk posed by pollutants commonly present in urban stormwater such as heavy metals and polycyclic aromatic hydrocarbons (PAHs) is critical for safe stormwater reuse. This study collected a total of 40 pollutant build-up samples and analysed the concentrations of nine heavy metals and 15 PAH species. Based on pollutant build-up data, pollutant concentrations in stormwater were estimated through modelling. Risk assessment was conducted using an existing model developed by previous studies. The study outcomes confirmed that simply evaluating the individual pollutant concentrations based on guideline threshold values cannot comprehensively estimate the overall human health risk posed by these pollutants. Accordingly, it is recommended that the assessment of the overall human health risk should be based on the pollutant mix present as provided by the models discussed in this paper. The study also demonstrated the practical application of a robust risk assessment model to derive the hierarchy of hazard control to provide a reliable underpinning to urban stormwater risk management. The outcomes suggest that decentralised hazard control methods such as the provision of custom designed Water Sensitive Urban Design (WSUD) measures can be implemented in priority areas with high risk from stormwater pollution based on the risk assessment undertaken. Distributed hazard control methods can be applied to reduce the generation of primary toxic pollutants, especially chromium (Cr) and heavy PAHs, through elimination and substitution measures. The percentage reduction in traffic volume required to mitigate the human health risk can be quantified through the risk models presented. The study outcomes will contribute to the development of efficient, targeted and reliable stormwater management strategies and to identify viable opportunities for stormwater reuse.