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Air pollution is the leading environmental hazard that has devastating health effects on human health. Identification of trends and patterns of air pollution is crucial in a specific geographic area to inform and implement effective control and mitigation measurements. Standard air pollution monitoring networks are costly for most low-and middle-income countries. The aim of this study was to investigate the variations in the mean concentrations of air pollutants that occur at various times of the day, days of the week, months of the year, and seasons during the period of January 2019 to December 2019 in Kandy, Sri Lanka using low-cost sensors. A regression analysis with dummy variables was used to model the relationship between the concentrations of air pollutants and categorical independent variables, the time of day and day of the week. Considering temporal variations, the study found that pollution is highest in the early morning and evening, and lowest in the afternoon. The worst days for the air quality were Wednesdays and Thursdays, while Sundays had the lowest PM2.5 pollution. The analysis of air quality variations by month showed that December had the lowest air pollution of the examined months. The variation in PM2.5 was greatly influenced by wind speed, wind direction, and rainfall patterns. The study emphasized the importance of long-term consistently management and monitoring of air pollution levels. [ABSTRACT FROM AUTHOR]

The development of rapid methods for in situ chromium determination in natural water is important. A new nanocomposite was fabricated by impregnating gold nanoparticles onto archetypical UiO-66 metal organic frameworks and modifying glassy carbon electrodes (Au/UiO-66/GCE) for rapid Cr(VI) determination in water by linear scanning voltammetry (LSV). The Au/UiO-66/GCE showed excellent linearity in the 100 to 1200 ppb Cr(VI) concentration range, with 0.07132 µA/ppb·cm2 sensitivity and a 11.73 ppb detection limit. When potential interfering metals were added, including Cr(III) and Fe(III), the electrochemical detection signal of Cr(VI) did not meaningfully change, suggesting that Au/UiO-66/GCE has good selectivity. A Au/UiO-66/screen printing sensor was also developed for Cr(VI) and used with a portable, handheld electro-analyzer. The Au/UiO-66 nanocomposite—used as an active substrate for electrode modification—was stable, interference-free, and fast, showing promise for the practical determination of Cr(VI) species. [ABSTRACT FROM AUTHOR]

This research specifically focused on the development of a novel methodology to reduce excess nitrate in drinking water utilizing zerovalent iron nanoparticles (nZVI)-stabilized radiation-grafted copolymer matrix. nZVI was synthesized by borohydrate reduction of FeCl3 and stabilized on acrylic acid (AAc)-grafted non-woven polyethylene/polypropylene (NWPE/PP-g-AAc) copolymer matrix, which was grafted using gamma radiation. The use of nZVI for environmental applications is challenging because of the formation of an oxide layer rapidly in the presence of oxygen. Therefore, radiation-grafted NWPE/PP synthetic fabric was used as the functional carrier to anchor nZVI and enhance its spreading and stability. The chemical reduction of nitrate by nZVI-adsorbed NWPE/PP-g-AAc (nZVI-Ads-NWP) fabric was examined in batch experiments at different pH values. At low pH values, the protective layers on nZVI particles can be readily dissolved, exposing the pure iron particles for efficient chemical reduction of nitrate. After about 24 h, at pH 3, almost 96% of nitrate was degraded, suggesting that this reduction process is an acid-driven, surface-mediated process. The nZVI-water interface has been characterized by the 1-pK Basic Stern Model (BSM). An Eley-Rideal like mechanism well described the nitrate reduction kinetics. In accordance with green technology, the newly synthesized nZVI-Ads-NWP has great potential for improving nitrate reduction processes required for the drinking water industry.

In this study, the iron-based carbon composite (hereafter FCN-x, x = 0, 400, 500, and 600 calcination) was synthesized by a simple high-temperature pyrolysis method using iron-containing sludge coagulant generated from wastewater treatment settling ponds in chemical plants. The FCN-x was used for the adsorptive reduction of aqueous phase Cr(VI) effectively. The FCN-x was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and Brunauer-Emmett-Teller theory (BET). FCN-x adsorption of Cr(VI) was examined in batch experiments using CrO42− as a function of physicochemical parameters. The chemical kinetics of Cr(VI) adsorption by FCN-500 were modeled by 1st and 2nd order empirical pseudo kinetics. Based on these experiments, FCN-500 has been selected for further studies on Cr(VI) adsorptive reduction. The maximum Cr(VI) adsorption by FCN-500 was 52.63 mg/g showing the highest removal efficiency. The Cr(VI) adsorption by the FCN-500 was quantified by the Langmuir isotherm. XPS result confirmed the reduction of Cr(VI) to Cr(III) by the FCN-500. The iron-based carbon composites have high reusability and application potential in water treatment. The electroplating wastewater with 117 mg/L Cr(VI) was treated with FCN-500, and 99.93% Cr(VI) was removed within 120 min, which is lower than the national chromium emission standard of the People's Republic of China. This work illustrates the value-added role of sludge generated from dye chemical plants to ensure environmental sustainability. [ABSTRACT FROM AUTHOR]