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This study inspects the concentrations of fine particulate matter (PM2.5) mass and carbonaceous species, including organic carbon (OC) and elemental carbon (EC), as well as their thermal fractions in the Indian Himalayan glacier region at the western Himalayan region (WHR; Thajiwas glacier, 2799 m asl), central Himalayan region (CHR; Gomukh glacier, 3415 m asl), and eastern Himalayan region (EHR; Zemu glacier, 2700 m asl) sites, throughout the summer and winter periods of 2019–2020. Ambient PM2.5 samples were collected on quartz fiber filters using a low-volume sampler, followed by carbon (OC and EC) quantification using the IMPROVE_A thermal/optical reflectance methodology. Different seasonal variations in PM2.5 and carbonaceous species levels were found at all three sites investigated. Averaged PM2.5 mass ranged 55–87 μg m–3 with a mean of 55.45 ± 16.30 μg m–3 at WHR, 86.80 ± 35.73 μg m–3 at CHR, and 72.61 ± 24.45 μg m–3 at EHR. Among the eight carbon fractions, high-temperature OC4 (evolved at 580 °C in the helium atmosphere) was the most prevalent carbon fraction, followed by low-temperature OC2 (280 °C) and EC1 (580 °C at 2% oxygen and 98% helium). Char-EC representing incomplete combustion contributed to 56, 67, and 53% of total EC, whereas soot-EC contributed to 38, 26, and 43% of total EC in WHR, CHR, and EHR, respectively. The measured OC/EC ratios imply the presence of secondary organic carbon, whereas char-EC/soot-EC ratios suggested that biomass burning could be the predominant source of carbon at CHR, whereas coal combustion and vehicular emission might be dominant sources at WHR and EHR sites.

A facile paper-based fluorescence sensing and electrochemical behavior of CdTe/ZnS quantum dots (QDs) for detection of methyl paraoxon has been reported. The hydrolytic activity of alkaline phosphatase (ALP) for methyl paraoxon was observed to produce p-nitrophenol in the presence of QDs. The fluorescence quenching of CdTe/ZnS QDs by p-nitrophenol was measured as a quantitative signal for the detection of methyl paraoxon. A paper chip-based sensor has been developed by deposition of CdTe/ZnS QDs into cellulose paper. The significant increase in oxidation current in the cyclic voltammogram of methyl paraoxon solution in the presence of ALP is observed using a glassy carbon electrode (GCE) modified with CdTe/ZnS QDs. The linear relationship between oxidation and reduction peak currents against concentration of methyl paraoxon is utilized as a quantitative signal of electrochemical detection of methyl paraoxon. Under optimum conditions, both fluorescenceand paper-based methods showed a limit of detection (LOD) ≈ 0.65 nM whereas cyclic voltammetry provided a 2-fold higher LOD (1.72 nM) for sensing of methyl paraoxon. Therefore, the present method is a new insight for the rapid, convenient, and trace amount detection of methyl paraoxon.

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