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•Systematic investigations of microplastic pollutants in Brisbane River sediments.•Improved method of microplastic separation and extraction.•Distance-based distribution of ...microplastics hotspots occur in river sediments.•Weight is a realistic indicator for evaluating the extent of microplastic pollution.
Plastic pollutants in aquatic ecosystems have received wide attention and research endeavours since early 1970s. However, in comparison to marine environments, the occurrence of microplastics in a tidal river system remains largely unknown, especially in river sediments. Sediment samples taken from twenty-two sampling points along Brisbane River over the four different seasons revealed relatively high concentrations of microplastics in river sediments, with abundance ranging from 0.18 to 129.20 mg kg−1, or 10 to 520 items kg−1. Unfortunately, varied methods and units used for reporting do not allow the accurate comparison between related studies. The spatial distributions of microplastics hotspots indicated that microplastics abundance is distance-dominated caused by flow velocities. Lower and higher concentrations of microplastics abundance mostly occurred in dry and wet seasons, respectively. Significant temporal variations of microplastics concentrations was observed in residential and commercial areas. Polyethylene (PE), polyamide (PA) and polypropylene (PP), were the three main polymer types found in the Brisbane River sediments. Other polymer types such as polyethylene terephthalate (PET) were also detected. The majority of the detected microplastic particles were found to be <3 mm. This study reveals the abundance, spatial and temporal distribution patterns, and characteristics of microplastic pollutants in Brisbane River sediments, and provides systematic data for further research on microplastics in estuarine environments worldwide.
•Despite significant research in ECs removal, significant knowledge gaps remain.•Phase-change, biological, AOP technologies, most common for removal of ECs in water.•Phase-change processes creates a ...challenge due to the concentrated waste streams.•Most research studies are laboratory scale, limited guidance for process scale-up.
In recent years, the presence of a group of contaminants, termed as emerging contaminants (ECs) has been recognized as significant water pollutants that have adverse effects on human and wildlife endocrine systems. Natural attenuation and conventional treatment processes are not capable of removing these micropollutants which are reported to bioaccummulate in macro invertebrates, other organisms in the aquatic food web and humans. An in-depth review of the state-of-the-art technologies available to remove emerging contaminants (ECs) in water was undertaken. The results of the review show that the majority of the research in recent years has focused on using phase-changing processes, including adsorption in different solid matrices and membrane processes, followed by biological treatment and advanced oxidation processes. This paper focuses on the type of EC being removed, the conditions of the process and the outcomes achieved. The main trends in the field are also highlighted along with perceptive comments and recommendations for further developments as well as the identification of the current knowledge gaps and future research directions related to the application of these technologies for water treatment and restoration.
Among the numerous pollutants present in urban road dust, polycyclic aromatic hydrocarbons (PAHs) are among the most toxic chemical pollutants and can pose cancer risk to humans. The primary aim of ...the study was to develop a quantitative model to assess the cancer risk from PAHs in urban road dust based on traffic and land use factors and thereby to characterise the risk posed by PAHs in fine (<150μm) and coarse (>150μm) particles. The risk posed by PAHs was quantified as incremental lifetime cancer risk (ILCR), which was modelled as a function of traffic volume and percentages of different urban land uses. The study outcomes highlighted the fact that cancer risk from PAHs in urban road dust is primarily influenced by PAHs associated with fine solids. Heavy PAHs with 5 to 6 benzene rings, especially dibenzoa,hanthracene (DaA) and benzoapyrene (BaP) in the mixture contribute most to the risk. The quantitative model developed based on traffic and land use factors will contribute to informed decision making in relation to the management of risk posed by PAHs in urban road dust.
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•Quantitative PAHs risk assessment approach in urban road dust was developed.•This assessment approach was based on land use and traffic characteristics.•Hotspots can be identified by using the approach to minimise the risk.
Variability in the pollutant wash-off process is a concept which needs to be understood in-depth in order to better assess the outcomes of stormwater quality models, and thereby strengthen stormwater ...pollution mitigation strategies. Current knowledge about the wash-off process does not extend to a clear understanding of the influence of the initially available pollutant build-up on the variability of the pollutant wash-off load and composition. Consequently, pollutant wash-off process variability is poorly characterised in stormwater quality models, which can result in inaccurate stormwater quality predictions. Mathematical simulation of particulate wash-off from three urban road surfaces confirmed that the wash-off load of particle size fractions <150μm and >150μm after a storm event vary with the build-up of the respective particle size fractions available at the beginning of the storm event. Furthermore, pollutant load and composition associated with the initially available build-up of <150μm particles predominantly influence the variability in washed-off pollutant load and composition. The influence of the build-up of pollutants associated with >150μm particles on wash-off process variability is significant only for relatively shorter duration storm events.
•Key characteristics of pollutant wash-off process variability are identified.•Variability of pollutant build-up process influences pollutant wash-off process.•Pollutant wash-off is a function of the build-up of particles <150μm and >150μm.•Particles <150μm generate significant variability in pollutant wash-off process.
This research study which was undertaken in a congested city environment in a developing country provides a robust approach for the assessment and management of human health risk associated with ...atmospheric heavy metals. The case study area was Kandy City, which is the second largest city in Sri Lanka and bears the characteristics of a typical city in the developing world such as the urban footprint, high population density and traffic congestion. Atmospheric deposition samples were collected on a weekly basis and analyzed for nine heavy metals common to urban environments, namely, Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb. Health risk was assessed using hazard quotient (HQ) and hazard index (HI), while the cancer risk was evaluated based on life time daily cancer risk. Al and Fe were found to be in relatively high concentrations due to the influence of both, natural and anthropogenic sources. High Zn loads were attributed to vehicular emissions and the wide use of Zn coated building materials. Contamination factor and geo-accumulation index showed that currently, Al and Fe are at uncontaminated levels and other metals are in the range of uncontaminated to contaminated levels, but with the potential to exacerbate in the long-term. The health risk assessment showed that the influence of the three exposure pathways were in the order of ingestion > dermal contact > inhalation. The HQ and HI values for children for the nine heavy metals were higher than that for adults, indicating that children may be subjected to potentially higher health risk than adults. The study methodology and outcomes provide fundamental knowledge to regulatory authorities to determine appropriate mitigation measures in relation to HM pollution in city environments in the developing world, where to-date only very limited research has been undertaken.
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•Heavy metals in atmospheric deposition in a congested environment were investigated.•Traffic and land use influences atmospheric metal concentrations.•The health risk assessed based on Hazard quotient (HQ) and Hazard index (HI).•Study area is still safe from atmospheric metal pollution, but risk is increasing.•Children are at higher health risk compared to adults.
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•Role of biochar hydrophilicity in the removal of emerging contaminants investigated.•Changes to thermally treated biochar surfaces increased adsorption performance.•Thermal treatment ...resulted in changes to biochar surface and crystalline structure.•Rate-limiting steps in removal process were adsorbate monolayer and chemisorption.•Anions in aqueous solution exert significant influence on the adsorption process.
This study investigated the removal of Acetaminophen (ACT) using biochars having different physicochemical characteristics. Biochars subjected to post-pyrolysis heat-treatment at 300 °C for different treatment times (0, 3.5, 8 and 24 h) were used. The resulting biochars were characterized using FTIR and X-ray diffraction spectroscopy. Experiments for ACT adsorption with different biochars loads (0.0, 0.05, 1, and 2 g L−1) were performed. Using the best performing material, ACT adsorption was investigated for additional biochar loads (4.0, and 6.0 g L−1) and experiments to test the effect of ionic strength were undertaken for different ions (chloride, carbonate, and nitrate) at three different concentrations (0.0, 1.0, 5.0 mM). The results showed that the changes to the surface of the thermally treated biochars increased the adsorption of ACT. The changes in the amount of oxygen-containing functional groups on the surface of the modified biochars (e.g., CO from 47.8 a.u. to 152 a.u. in the untreated and thermally treated biochars, respectively), as well as modifications to their crystalline structure are considered to be the reason for the observed improvement. Adsorption isotherms and kinetic models suggest the generation of an adsorbate monolayer and chemisorption as the rate-limiting step. The different anions tested were found to have a significant influence on ACT adsorption, related to their electronegativity and steric effect, as confirmed by the multivariate analysis.
Biochar-supported nanomaterials for environmental applications Rodriguez-Narvaez, Oscar M.; Peralta-Hernandez, Juan Manuel; Goonetilleke, Ashantha ...
Journal of industrial and engineering chemistry (Seoul, Korea),
10/2019, Volume:
78
Journal Article
Peer reviewed
Open access
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Immobilizing nanomaterials in highly porous, surface active, structurally stable biochar creates novel nanocomposites that combines the well-known advantages of both materials. The ...exceptional contaminant adsorption and/or catalytic degradation capabilities of these nanocomposites have attracted the attention of the scientific community for possible use in environmental applications. This paper reviews the different methodologies for synthesizing biochar-supported nanomaterials, the key physical and chemical characteristics of these nanomaterials, and their performance in environmental applications, as well as identifies current knowledge gaps and potential directions for further research and development.
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•Surface hydrophobicity/hydrophilicity influence pollutant leaching of biochar.•Biochar with hydrophilic surface leached more nutrients/organic matter.•Biochar with hydrophilic ...surface leached less metals.•Results provide essential guidance on appropriate use of biochar in water treatment.
This study investigated the role of surface hydrophobicity/hydrophilicity of biochar on its pollutant leaching potential (pollutants originally in biomass feedstock), including nutrients, organic matter and metals, in water treatment applications. The study outcomes confirmed that biochar with greater hydrophilic surface leached comparatively higher loads of nutrients and organic matter compared to biochar with mostly hydrophobic surface, while biochar with greater hydrophilic surface leached lower metal loads. This trend is attributed to the changes to the physical and chemical properties of biochar including specific surface area and surface functional groups, as well as being related to the binding forces between the biochar surface and the different compounds. Further, the study results substantiated the significant influence of surface characteristics of biochar, and its preparation process on pollutant leaching potential. The study outcomes provide essential guidance on the appropriate use of biochar as an adsorbent in water treatment, including raw biomass selection and the production processes to be adopted.
An in-depth understanding of polycyclic aromatic hydrocarbons (PAHs) build-up on urban roads is essential for effective stormwater treatment design. Past research studies have pointed out the ...relationship between influential factors and PAHs build-up individually. However, these studies do not provide a comprehensive analysis of the relationships and the hierarchy of factors in terms of their importance in influencing PAHs build-up. This paper presents the outcomes of an in-depth investigation into the range of influential factors, including traffic volume, land use, distance to highway and roughness of road surfaces by ranking them in terms of their influence on PAHs build-up. A number of data analysis techniques including forward stepwise linear regression (FSWLR), principal component analysis (PCA) and multiple linear regression (MLR) were employed for the analyses undertaken. The outcomes confirmed that traffic volume is ranked first while land use and roughness of road surfaces are second and the third, respectively. Distance to highway did not show a significant influence on PAHs build-up. Additionally, it was noted that a high traffic volume tended to produce high loads of PAHs with more than 4 rings and the spatial variability of PAHs build-up were relatively higher in high traffic volume areas. These outcomes contributed to the formulation of a robust stormwater treatment strategy and generation of priority area maps focusing on the removal of PAHs.
•Factors influencing polycyclic aromatic hydrocarbons (PAHs) build-up were ranked.•Traffic volume was ranked first while land use was ranked second.•PAHs build-up load and variability increase with increasing traffic volume.•A stormwater treatment strategy and priority area maps were created.
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