Study of the influence of temperature and precipitations on the levels of BTEX in natural waters

Aromatic hydrocarbons extracted by headspace and microextraction methods in water-soluble fractions from crude oil, fuels and lubricants

Two extraction protocols were developed for the determination of mono- and poly-aromatic hydrocarbons in water-soluble fractions from gasoline, diesel, crude, mineral insulating, and lubricant oils. Development of the procedures was based on clean miniaturized strategies, such as headspace extraction and vortex-assisted dispersive liquid micro-extraction, together with quantification by gas chromatography-mass spectrometry. The mono-aromatic hydrocarbons were extracted using the headspace extraction method. The linear range obtained was 10-500 µg L^-1, with r² > 0.99. Based on the parameters of the analytical curves, detection and quantification limits of 2.56-3.20 and 7.76-9.71 µg L^-1 were estimated. In addition, the method showed adequate recoveries of 69.4-83.5%, with a satisfactory precision of 4.7-17.1% (n = 5). Micro-extraction was applied for the poly-aromatics and the most favorable variables were sample volume (5.00 mL) in sodium chloride medium (1%, w/v), trichloromethane as extractor solvent (75 µL), acetone as disperser (925 µL) and vortexing for 1 min. Under these conditions, analytical curves of 0.15-4.00 µg L^-1 were obtained and limits of determination and quantification were 0.03-0.15 and 0.09-0.46 µg L^-1, respectively. Recovery values of 87.6-124.5% and a maximum relative standard deviation of 18.9% (n = 5) verify satisfactory accuracy and precision. This led to the achievement of enrichment factors for poly-aromatic hydrocarbons of 41-89 times. Finally, the methods were employed in samples of water-soluble fractions for the determination of analytes. The values followed the order: gasoline > diesel > crude > lubricant > mineral insulating oil. These results indicate an increase in lighter fractions, followed by poly-aromatics in more refined products.

Characterizing benzene series (BTEX) pollutants build-up process on urban roads: Implication for the importance of temperature

Benzene series (BTEX) pollutants which are generated by traffic can deposit (build-up) on urban road surfaces. When they are washed-off by stormwater runoff, BTEX are toxic to ecological and human health if the stormwater is reused. To understand the risk posed by BTEX, it is essential to have an in-depth investigation on BTEX build-up, one of the most important stormwater pollutant processes. This study analysed the relationship between BTEX build-up and BTEX build-up's influential factors. The outcomes confirmed an important role of climatic factors (particularly temperature) on influencing BTEX build-up. This has not been considered in previous stormwater studies although this has been widely focused in atmospheric pollution. BTEX build-up loads were generally higher and the variability was low in dry seasons with low temperature such as winter and spring. Additionally, the influence of temperature on BTEX build-up on urban road surfaces is more important in the case of larger particles (such as >75 μm) than smaller particles. The study also showed that petrol station areas have a potential to export stormwater runoff with high BTEX concentrations, compared to typical urban roads. This is particularly applicable in winter and spring. These outcomes can provide useful guidance to improving stormwater quality modelling approaches, especially relevant to estimation of BTEX concentrations in the stormwater.

Three-dimensional Pd/Pt bimetallic nanodendrites on a highly porous copper foam fiber for headspace solid-phase microextraction of BTEX prior to their quantification by GC-FID

The preparation of bimetallic Pd/Pt nanofoam for use in fiber based solid-phase microextraction (SPME) is described. First, a highly porous copper foam was prepared on the surface of an unbreakable copper wire by an electrochemical method. Then, the substrate was covered with metallic Pd and Pt using galvanic replacement of the Cu nanofoam substrate by applying a mixture of Pd(II) and Pt(IV) ions. The procedure provided an efficient route to modify Pd/Pt nanofoams with large specific surface and low loading with expensive noble metals. The fiber was applied to headspace SPME of benzene, toluene, ethylbenzene and xylene (BTEX) (as the model compounds) in various spiked water and wastewater samples. It was followed by gas chromatography-flame ionization detection (GC-FID). A Plackett-Burman design was performed for screening the experimental factors prior to Box-Behnken design. Compared with the commercial PDMS SPME fiber (100 μm), it had higher extraction efficiency for BTEX. Under the optimum conditions, the method has low limits of detection (0.16-0.35 μg L^-1), a wide linear range (1-200 μg L^-1), relative standard deviations between 5.8 and 10.5%, and good recoveries (>85% from spiked samples). Graphical abstract Schematic presentation of a three-dimensional Pd/Pt bimetallic nanodendrites supported on a highly porous copper foam fiber for use in headspace solid phase microextraction of BTEX. They were then quantified by gas chromatography-flame ionization detector.

Understanding re-distribution of road deposited particle-bound pollutants using a Bayesian Network (BN) approach

Road deposited pollutants (build-up) are continuously re-distributed by external factors such as traffic and wind turbulence, influencing stormwater runoff quality. However, current stormwater quality modelling approaches do not account for the re-distribution of pollutants. This undermines the accuracy of stormwater quality predictions, constraining the design of effective stormwater treatment measures. This study, using over 1000 data points, developed a Bayesian Network modelling approach to investigate the re-distribution of pollutant build-up on urban road surfaces. BTEX, which are a group of highly toxic pollutants, was the case study pollutants. Build-up sampling was undertaken in Shenzhen, China, using a dry and wet vacuuming method. The research outcomes confirmed that the vehicle type and particle size significantly influence the re-distribution of particle-bound BTEX. Compared to heavy-duty traffic in commercial areas, light-duty traffic dominates the re-distribution of particles of all size ranges. In industrial areas, heavy-duty traffic re-distributes particles >75 μm, and light-duty traffic re-distributes particles <75 μm. In residential areas, light-duty traffic re-distributes particles >300 μm and <75 μm and heavy-duty traffic re-distributes particles in the 300-150 μm range. The study results provide important insights to improve stormwater quality modelling and the interpretation of modelling outcomes, contributing to safeguard the urban water environment.

Understanding benzene series (BTEX) pollutant load characteristics in the urban environment

Benzene series (BTEX) pollutants are toxic and can pose high ecological and human health risk. BTEX pollutants can accumulate on urban road surfaces during dry periods and then be washed-off by stormwater runoff into receiving waters, degrading water quality. In this context, designing effective stormwater treatment systems to remove BTEX pollutants before entering urban water bodies is essential to safeguard urban water environment and this is closely dependent on an in-depth understanding of characteristics of pollutant loads accumulated on urban catchment surfaces. This study investigated BTEX pollutant load characteristics through collecting samples on 17 urban roads and three petrol station sites using dry and wet vacuuming method. The research outcomes showed that petrol station sites had the highest BTEX pollutant loads (mean value was 8.41μg/g) than common urban roads (6.61μg/g, 4.38μg/g and 4.60μg/g for industrial, commercial and residential roads). This highlighted a high potential of petrol station areas to export BTEX pollutants to stormwater runoff. It is also noted that industrial development plays the more important role in influencing BTEX pollutant loads than other factors including total daily traffic volume, daily heavy-duty vehicle volume, daily light-duty vehicle volume, residential development, commercial development and road texture depth. Higher industrial land use fraction led to higher BTEX pollutant loads while the spatial variability of BTEX pollutant loads generally decreased with increasing industrial land use fraction. These outcomes can assist on improving stormwater quality modelling approaches and adequately understanding the modelling results.

Contamination levels and potential sources of organic pollution in an Asian river

The Houjing River has long been an environmental victim of economic development. Industries that have settled along the bank of this river may have largely contributed to severe organic wastes pollution. This study collected water and sediment samples at various points along the river and measured concentrations of 61 volatile organic compounds (VOCs) and 128 semi-volatile organic compounds (SVOCs) for a period of 16 months (Feb 2014-June 2015). Our analyses show that elevated levels of VOCs were observed near two industrial areas, Dashe and Renwu industrial parks. High SVOC concentrations were found in the vicinities of the Nanzih Export Processing Zone (NEPZ) and CingPu station, possibly due to considerable effluent discharges of adjacent industrial and residential areas. Comparing this study's findings with the standard values of different governmental agencies and studies similar to this one, the ecosystem of the Houjing River was seriously contaminated. This study could be used by the government as a basis for future and urgent pollution prevention actions aimed at protecting this ecosystem and reducing the negative impacts of these contaminants on the health and well-being of the local residents and the environment.

Environmental effects of crude oil spill on the physicochemical and hydrobiological characteristics of the Nun River, Niger Delta

Oil spill pollution has remained a source of several international litigations in the Niger Delta region of Nigeria. In this paper, we examined the impacts of small recurrent crude oil spills on the physicochemical, microbial and hydrobiological properties of the Nun River, a primary source of drinking water, food and recreational activities for communities in the region. Samples were collected from six sampling points along the stretch of the lower Nun River over a 3-week period. Temperature, pH salinity, turbidity, total suspended solids, total dissolved solids, dissolved oxygen, phosphate, nitrate, heavy metals, BTEX, PAHs and microbial and plankton contents were assessed to ascertain the quality and level of deterioration of the river. The results obtained were compared with the baseline data from studies, national and international standards. The results of the physicochemical parameters indicated a significant deterioration of the river quality due to oil production activities. Turbidity, TDS, TSS, DO, conductivity and heavy metals (Cd, Cr, Cu, Pb, Ni and Zn) were in breach of the national and international limits for drinking water aquatic health. They were also significantly higher than the initial baseline conditions of the river. Also, there were noticeable changes in the phytoplankton, zooplankton and microbial diversities due to oil pollution across the sampling zones.