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During the monsoon season in 2011 (July to August), 33 rainwater samples were collected at Gongabu, Kathmandu Valley, Nepal. The major ions and stable isotopic compositions of nitrogen and oxygen of NO 3 -were measured to identify the NO 3 -sources in rainwater. Temporal variation in the major ions in rainfall shows that higher concentration corresponds to low rainfall, but a high volume of rainfall also shows the same pattern, indicating an atmosphere polluted with dust. Rainwater chemistry was analyzed using correlation and principal component analysis to identify the possible sources of the measured ions. Two components were identified, which accounted for 85.5% of total variance: (1)

The limited availability, accessibility and deterioration of the water quality in Kathmandu valley have led to the high demand of ground water. This study aims to evaluate ground water quality of the Kathmandu valley. In this study, the physio-chemical parameters of water samples were performed using standard procedures. Also, total coliforms were enumerated using standard membrane filtration technique to quantify the bacterial contamination. Water samples were collected from July 2017 to July 2018. The results revealed that 56% and 73% of well and boring water samples, respectively exceeded standard value of iron recommended by National Drinking Water Quality Standards, 2005. Likewise, ammonia content was higher in 41% of well water and 35% of boring water samples than standard. However, few numbers of water samples were contaminated with arsenic (0.27% and 2.6% of well and boring water samples, respectively) and nitrate (3% and 8% of well and boring water samples, respectively). Besides, 96% of well water samples and 88% of boring water samples were contaminated with total coliform bacteria. Our data indicated that groundwater quality of Kathmandu valley was poor, which was not suitable for direct drinking purposes. Therefore, regular monitoring and treatment of groundwater is recommended before using accordingly.

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We measured submicron aerosols (PM1) at a beachfront site in Texas in Spring 2021 to characterize the “background” aerosol chemical composition advecting into Texas and the factors controlling this composition. Observations show that marine “background” aerosols from the Gulf of Mexico were highly processed and acidic; sulfate was the most abundant component (on average 57% of total PM1 mass), followed by organic material (26%). These chemical characteristics are similar to those observed at other marine locations globally. However, Gulf “background” aerosols were much more polluted; the average non-refractory (NR-) PM1 mass concentration was 3–70 times higher than that observed in other clean marine atmospheres. Anthropogenic shipping emissions over the Gulf of Mexico explain 78.3% of the total measured “background” sulfate in the Gulf air. We frequently observed haze pollution in the air mass from the Gulf, with significantly elevated concentrations of sulfate, organosulfates, and secondary organic aerosol associated with sulfuric acid. Analysis suggests that aqueous oxidation of shipping emissions over the Gulf of Mexico by peroxides in the particles might potentially be an important pathway for the rapid production of acidic sulfate and organosulfates during the haze episodes under acidic conditions.

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