Hydrogeochemistry of Two Major Mid-hill Lentic Water Bodies for Irrigation of the Central Himalaya, Nepal

The concentration and composition of different salts in natural water bodies determine the water quality for various purposes. This study assesses the water quality of two mid-mountain lentic water bodies, Lake Phewa and Kulekhani Reservoir. For this purpose, selected physico-chemical parameters along with major ions such as HCO3-, SO42-, PO43-, NO3-, Cl-, Ca2+, Mg2+, Na+, K+, and NH4+ were analyzed. Major ions were analyzed using ion chromatography, anions by DX-600 and cations by Dionex ISC-2500 ion chromatographs. The sources of major ions were determined by using the Gibbs diagram, Piper plot, and Scatter plots. Dissolved oxygen, ammonia and phosphate showed seasonal variations in both lakes. The concentrations of cations are in the order of Ca2+ > Na+ > Mg2+ > K+ in both water bodies. However the trend of anions had small variations for Cl- and SO42- in Lake Phewa (HCO3- > Cl- > SO42- > NO3-) and Kulekhani Reservoir (HCO3- > SO42- > Cl- > NO3-). The Piper plot and equiline plots indicated that the water chemistry is dominantly controlled by the dissolution of carbonate minerals and to a limited extent by weathering of silicate minerals. This is further supported by the Gibbs plot showing bedrock geology as the main source of major ions. The overall study indicates that the hydrogeochemistry of these water bodies is controlled by local geology and is suitable for irrigation purposes

Black carbon and organic carbon dataset over the Third Pole

The Tibetan Plateau and its surroundings, also known as the Third Pole, play an important role in the global and regional climate and hydrological cycle. Carbonaceous aerosols (CAs), including black carbon (BC) and organic carbon (OC), can directly or indirectly absorb and scatter solar radiation and change the energy balance on the Earth. CAs, along with the other atmospheric pollutants (e.g., mercury), can be frequently transported over long distances into the inland Tibetan Plateau. During the last decades, a coordinated monitoring network and research program named “Atmospheric Pollution and Cryospheric Changes” (APCC) has been gradually set up and continuously operated within the Third Pole regions to investigate the linkage between atmospheric pollutants and cryospheric changes. This paper presents a systematic dataset of BC, OC, water-soluble organic carbon (WSOC), and water-insoluble organic carbon (WIOC) from aerosols (20 stations), glaciers (17 glaciers, including samples from surface snow and ice, snow pits, and 2 ice cores), snow cover (2 stations continuously observed and 138 locations surveyed once), precipitation (6 stations), and lake sediment cores (7 lakes) collected across the Third Pole, based on the APCC program. These data were created based on online (in situ) and laboratory measurements. High-resolution (daily scale) atmospheric-equivalent BC concentrations were obtained by using an Aethalometer (AE-33) in the Mt. Everest (Qomolangma) region, which can provide new insight into the mechanism of BC transportation over the Himalayas. Spatial distributions of BC, OC, WSOC, and WIOC from aerosols, glaciers, snow cover, and precipitation indicated different features among the different regions of the Third Pole, which were mostly influenced by emission sources, transport pathways, and deposition processes. Historical records of BC from ice cores and lake sediment cores revealed the strength of the impacts of human activity since the Industrial Revolution. BC isotopes from glaciers and aerosols identified the relative contributions of biomass and fossil fuel combustion to BC deposition on the Third Pole. Mass absorption cross sections of BC and WSOC from aerosol, glaciers, snow cover, and precipitation samples were also provided. This updated dataset is released to the scientific communities focusing on atmospheric science, cryospheric science, hydrology, climatology, and environmental science. The related datasets are presented in the form of excel files. BC and OC datasets over the Third Pole are available to download from the National Cryosphere Desert Data Center (10.12072/ncdc.NIEER.db0114.2021; Kang and Zhang, 2021)

Modification and coupled use of technologies are an essential envisioned need for bioaerosol study – An emerging public health concern

The airborne microbiome is one of the relevant topics in ecology, biogeochemistry, environment, and human health. Bioaerosols are ubiquitous air pollutants that play a vital role in the linking of the ecosystem with the biosphere, atmosphere, climate, and public health. However, the sources, abundance, composition, properties, and atmospheric transport mechanisms of bioaerosols are not clearly understood. To screen the effects of climate change on aerosol microbial composition and its consequences for human health, it is first essential to develop standards that recognize the existing microbial components and how they vary naturally. Bioaerosol particles can be considered an information-rich unit comprising diverse cellular and protein materials emitted by humans, animals, and plants. Hence, no single standard technique can satisfactorily extract the required information about bioaerosols. To account for these issues, metagenomics, mass spectrometry, and biological and chemical analyses can be combined with climatic studies to understand the physical and biological relationships among bioaerosols. This can be achieved by strengthening interdisciplinary teamwork in biology, chemistry, earth science, and life sciences and by sharing knowledge and expertise globally. Thus, the coupled use of various advanced analytical approaches is the ultimate key to opening up the biological treasure that lies in the environment

Variations of the Physicochemical Parameters and Metal Levels and Their Risk Assessment in Urbanized Bagmati River, Kathmandu, Nepal

During post-monsoon 2013, surface water samples were collected form 34 sites from the Bagmati River and its tributaries within the Kathmandu Valley to assess the river water quality. The physical parameters were measured on site and major ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, SO42-, and NO3-) and 17 elements in water were analyzed in the laboratory. Conductivity ranged from 21.92 to 846 μS/cm, while turbidity ranged from 2.52 to 223 NTU and dissolved oxygen (DO) ranged from 0.04 to 8.98 mg/L. The ionic and elemental concentrations were higher in the lower section where the population density is high compared to the headwaters. The large input of wastewater and organic load created anoxic condition by consuming dissolved oxygen along the lower belt of the river. The concentration of the elements was found to be in the order of Mn > Zn > Ti > Rb > Cr > Cu > Sc > Ni > V > Li > Co > Mo > Cd > Y > Ga > Be > Nb. The concentration of Mn, Cd, Cr, Co, and Zn was particularly higher in urban and semiurban sections. Enrichment factor (EF) calculations for Cd, Co, and Zn showed their highly enriched values indicating that these elements originated from anthropogenic sources. Preliminary risk assessments were determined by the hazard quotient (HQ) calculations in order to evaluate the health risk of the metals. The HQingestion values of elements were found to be in the order Sb > Mn > Cr > V > Co > Cd > Cu > Zn > Ni > Li > Mo with all averaged HQ values less than 1, indicating no or limited health risk of metals from the river to the local residence. However the values of Sb in some parts of the Bagmati were close to unity indicating its possible threat. Anthropogenic activities like industrial activities, municipal waste water, and road construction besides the river appear to control the chemical constituent of the river water. Overall the river was highly polluted with elevated concentrations of major ions and elements and there is a need for restoration projects

Isotopic Evolution in Snowpacks from a Typical Temperate Glacier in the South-Asia Monsoon Region

In this study, snow samples collected from nine snowpacks from Mt. Yulong are measured to examine the monthly and annual isotopic variation. The results indicate that the late autumn and winter snow sampled in 2008/2009 show a similar high–low–high δ18O variation. In spring, the high–low–high curve still exists in the lower layers (<1.5 m), while relatively high values are witnessed in the upper layers (>1.5 m). Isotopic homogenization, smoothing the vertical variation of δ18O in snow, is observed in June and July when snow melting occurs. Samples collected in April of 2009, 2012 and 2017 show significant differences, suggesting annual changes of isotope contents in snow. This study suggests that the isotope contents in the snow profile can reflect meteorological information. At the monthly scale, we can distinguish the information on snow accumulation and melting by determining the monthly variation of vertical isotope contents in snow. At the annual scale, we can analyze the annual difference of corresponding meteorological factors. Collectively, observing the stable isotopes in snow could provide evidence for climate change, particularly when climatic data are lacking or are challenging to obtain in cold glacierized regions

Water-Soluble Ionic Composition of Aerosols at Urban Location in the Foothills of Himalaya, Pokhara Valley, Nepal

The total suspended particulate (TSP) samples were collected from April 2013 to April 2014 at the urban location of Pokhara valley in western Nepal. The major aims were to study, quantify, and understand the concentrations and variations of TSP and major water-soluble inorganic ions (WSIIs) in the valley with limited data. The annual average TSP mass concentration was 135.50 ± 62.91 µg/m3. The average analyzed total WSIIs accounted for 14.4% of total TSP mass. Major anions and cations in TSP samples were SO42− and Ca2+, respectively. Seasonal differences in atmospheric conditions explain the clear seasonal variations of ions, with higher concentrations during pre-monsoon and winter and lower concentrations during the monsoon period. Neutralization factor calculations suggested that Ca2+ in the Pokhara valley mostly neutralizes the acidity in the atmosphere. Principle component analysis, NO3−/SO42− ratio, and non-sea salt fraction calculations suggested that the WSIIs in the valley were mostly derived from anthropogenic activities and crustal mineral dust, which was also supported by the results from precipitation chemistry over the central Himalayas, Nepal. In addition, back trajectories analysis has suggested that the air pollution transported from and through Indo-Gangetic Plains (IGP) during the dry periods, which has resulted in high ionic loadings during this period. Average NO3−/SO42− ratio was found to be 0.69, indicating the dominance of stationary sources of TSP in Pokhara valley. Secondary inorganic aerosols can have an adverse health impact on the human population in the valley. The data set from this one-year study provides new insights into the composition of WSIIs in the foothills of the Himalayas, which can be of great importance for understanding the atmospheric environment in the region

Carbonaceous aerosol transport from the Indo-Gangetic Plain to the Himalayas: Carbon isotope evidence and light absorption characteristics

The Indo-Gangetic Plain (IGP) is a major regional and global emitter of atmospheric pollutants, which adversely affect surrounding areas such as the Himalayas. We present a comprehensive dataset on carbonaceous aerosol (CA) composition, radiocarbon (Δ14C) -based source apportionment, and light absorption of total suspended particle (TSP) samples collected over a 3-year period from high-altitude Jomsom in the central Himalayas. The 3-year mean TSP, organic carbon (OC), and elemental carbon (EC) concentrations were 92.0 ± 28.6, 9.74 ± 6.31, and 2.02 ± 1.35 μg m−3, respectively, with the highest concentrations observed during the pre-monsoon season, followed by the post-monsoon, winter, and monsoon seasons. The Δ14C analysis revealed that the contribution of fossil fuel combustion (ffossil) to EC was 47.9% ± 11.5%, which is consistent with observations in urban and remote regions in South Asia and attests that EC likely arrives in Jomsom from upwind IGP sources via long-range transport. In addition, the lowest ffossil (38.7% ± 13.3%) was observed in winter, indicating large contributions in this season from local biomass burning. The mass absorption cross-section of EC (MACEC: 8.27 ± 1.76 m2/g) and water-soluble organic carbon (MACWSOC: 0.98 ± 0.45 m2/g) were slightly higher and lower than those reported in urban regions, respectively, indicating that CA undergo an aging process. Organic aerosol coating during transport and variation of biomass burning probably led to the seasonal variation in MAC of two components. Overall, WSOC contributed considerably to the light absorption (11.1% ± 4.23%) of EC. The findings suggest that to protect glaciers of the Himalayas from pollution-related melting, it is essential to mitigate emissions from the IGP

Investigation of Aerosol Climatology and Long-Range Transport of Aerosols over Pokhara, Nepal

This study presents the spectral monthly and seasonal variation of aerosol optical depth (τAOD), single scattering albedo (SSA), and aerosol absorption optical depth (AAOD) between 2010 and 2018 obtained from the Aerosol Robotic Network (AERONET) over Pokhara, Nepal. The analysis of these column-integrated aerosol optical data suggests significant monthly and seasonal variability of aerosol physical and optical properties. The pre-monsoon season (March to May) has the highest observed τAOD(0.75 ± 0.15), followed by winter (December to February, 0.47 ± 0.12), post-monsoon (October and November, 0.39 ± 0.08), and monsoon seasons (June to September, 0.27 ± 0.13), indicating seasonal aerosol loading over Pokhara. The variability of Ångström parameters, α, and β, were computed from the linear fit line in the logarithmic scale of spectral τAOD, and used to analyze the aerosol physical characteristics such as particle size and aerosol loading. The curvature of spectral τAOD, α’, computed from the second-order polynomial fit, reveals the domination by fine mode aerosol particles in the post-monsoon and winter seasons, with coarse mode dominating in monsoon, and both modes contributing in the pre-monsoon. Analysis of air mass back trajectories and observation of fire spots along with aerosol optical data and aerosol size spectra suggest the presence of mixed types of transboundary aerosols, such as biomass, urban-industrial, and dust aerosols in the atmospheric column over Pokhara

Recycled moisture in an enclosed basin, Guanzhong Basin of Northern China, in the summer: Contribution to precipitation based on a stable isotope approach

Recycled moisture, mainly originated from evapotranspiration (surface evaporation and transpiration), is the main sources of precipitation. Influenced on the different regional/local environments, the contributions of recycled moisture to precipitation present as different proportions. Recycled moisture has an important impact on the hydrological cycle, further occurred a series of environmental effect for regional/local. Aimed to estimate the contribution of recycled moisture to precipitation in an enclosed basin, Guanzhong Basin of northern China, precipitation and lake/reservoir samples were collected. The isotope ratio analysis was done for the summer season, and a three-component mixing model based on the stable hydrogen and oxygen isotopes was applied. The results indicated that the averaged contribution of recycled moisture to precipitation was 17.44% in Guanzhong Basin of northern China, while the mean proportions of surface evaporation moisture and transpiration moisture were found to be 0.38% and 16.97%, respectively. Comparatively, most of the recycled moisture mainly comes from transpiration moisture rather than evaporation moisture, suggesting that transpiration moisture from cropland, vegetation, and plants instead of evaporation is dominant in moisture recycling of the Guanzhong Basin