Search

This study analysed factors influencing the decision to use chemical fertilisers by farmers at the household level, and it included a related assessment of nutrients in nearby water bodies. One focus group discussion was held at each site, and then a total of 198 and 58 households in Lake Phewa and Kulekhani Reservoir, respectively, were surveyed. The results reveal that 90% and 55% of households applied chemical fertilisers in Lake Phewa and Kulekhani Reservoir, respectively. A logistic regression model indicated that the two factors having a significant positive influence on the decision to use chemical fertilisers were higher vegetable yield and the amount of urea available to farmers Water sampling indicated that phosphorous concentrations were relatively high in both these water bodies compared to previous studies in other nearby lakes.

Planktons are the community of pelagic organisms, composed of different groups, which are in suspension in water and hence restricted mobility, often less than that of the water which carries them. The study was carried out during the winter of 2019 to observe the phytoplankton and zooplankton abundance and distribution in Ghodaghodi Lake, Nepal. Temperature, pH, electrical conductivity, dissolved oxygen, Secchi disc transparency, total dissolved solids, and turbidity were analyzed during the study. Collection of plankton samples were made by conical-shaped monofilament nylon plankton net of 90 μm mesh net size from approximately 10 ‐ 12 cm depth from six different sites. A total of 58 individuals of zooplankton were enumerated during the present investigation. The maximum number was counted for Mesocyclops sp (n=18) and minimum for Diaptomus (n=1). The highest zooplanktons were reported from site I (n= 12) and the lowest were reported from site II (n=7). Cladocera was the most dominating zooplankton group. A total of 85 individuals of phytoplankton were enumerated during the present investigation. The maximum number was counted for Spirogyra sp (30) and the minimum for Lamena sp (1). The most leading group of the phytoplankton was Chlorophyceae (30), followed by Cyanophyceae (13), Bacillariophyceae (7) and group Zygnematophyceae (6). Thus, these resources are also favorable for flourishing fish diversity in a lake ecosystem.

This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM2.5 and TSP during pre-monsoon (March–May 2018) from a highly polluted urban Kathmandu Valley (KV) of the Himalayan foothills. The mean mass concentration of PM2.5 (129.8 µg/m3) was only ~25% of TSP mass (558.7 µg/ m3) indicating the dominance of coarser mode aerosols. However, the mean concentration as well as fractional contributions of water-soluble total nitrogen (WSTN) and carbonaceous species reveal their predominance in find-mode aerosols. The mean mass concentration of WSTN was 17.43±4.70 µg/m3 (14%) in PM2.5 and 24.64±8.07 µg/m3 (5%) in TSP. Moreover, the fractional contribution of total carbonaceous aerosols (TCA) is much higher in PM2.5 (~34%) than that in TSP (~20%). The relatively low OC/EC ratio in PM2.5 (3.03 ± 1.47) and TSP (4.64 ± 1.73) suggests fossil fuel combustion as the major sources of carbonaceous aerosols with contributions from secondary organic aerosols. Five-day air mass back trajectories simulated with the HYSPLIT model, together with MODIS fire counts indicate the influence of local emissions as well as transported pollutants from the Indo-Gangetic Plain region to the south of the Himalayan foothills. Principal component analysis (PCA) also suggests a mixed contribution from other local anthropogenic, biomass burning, and crustal sources. Our results highlight that it is necessary to control local emissions as well as regional transport while designing mitigation measures to reduce the KV's air pollution.

This research investigates the heavy metals (Zn, Cd, Cu and Pb) concentration in water, sediments and macrophytes in Ghodaghodi Lake during winter and summer seasons of 2019 to find out the bioaccumulation of metals and phytoremediation potential of locally available macrophytes. Atomic absorption spectrophotometer with acid digestion method was used for analysis of heavy metals. The mean heavy metals concentration during summer and winter season were in the order: Zn > Cu > Pb > Cd in water and sediments. The mean concentrations of Cd, Cu and Pb were significantly higher in winter (0.79±0.71, 12.99±3.16, and 11.39±6.88 mg/g, respectively) than summer season (0.01±0.00, 9.13±5.21, and 2.16±6.64 mg/g, respectively) in sediments which is also supported by geo-accumulation index. Zinc had also higher concentrations in winter (65.29±13.13 mg/g) compared to summer (44.00±21.08 mg/g), though not significant. Ludwigia sp. was more capable of accumulating heavy metals than the Nymphaea sp. in winter season. On the other hand, Nelumbo sp. was more effective of accumulating heavy metals (except Zn) compared to Ludwigia sp. in summer season. The highest bioaccumulation factor (macrophyte/sediment) for Ludwigia sp. (common in both seasons) was observed for Cd in winter and Pb in summer season. Thus, although there were some variations in potentiality of bioaccumulation among the species, these macrophytes are capable of accumulating heavy metals providing scope in bioremediation field.

Eutrophication is one of the growing environmental concerns and is affecting and compromising freshwater bodies across the world making the trophic status assessment of water bodies crucial for their restoration and sustainable use. This paper describes the trophic status of Lake Phewa and Kulekhani Reservoir from Nepal. Sampling was conducted during October 2017 (post-monsoon), April 2018 (Pre-monsoon), July 2018 (Monsoon) and February 2019 (Winter). Trophic State Index (TSI) as given by Carlson (1977) and Trophic State Index Deviation given by Carlson (1991) were estimated to assess trophic status and deviations between the Trophic State Indices. One-way analysis of variance showed significant seasonal variation (p < 0.05) in Secchi depth, total phosphorus (TP), TSI in both the water bodies. Both the water bodies were classified as eutrophic during pre-monsoon and post-monsoon, and hypereutrophic during the monsoon indicating the increased flow of allochthonous inputs from their respective catchments. Non-algal turbidity was found to be the limiting factor for productivity. There is a need for sustainable watershed management in order to reduce the nutrients runoff and accumulation in the water bodies.

In this work, samples of surface snow, surface ice, snow pit and meltwater from the Laohugou Glacier No. 12 on the northern edge of Tibetan Plateau (TP) were collected during the summer of 2015. The average concentration of Hg in surface snow/ice was 22.41 ng L−1, while the percentage of dissolved mercury (HgD) was observed to be around 26%. An altitudinal magnification of Hg was not observed for surface snow; however, in contrast, a significant positive magnification of Hg with altitude was observed in the surface ice. A higher concentration of Hg corresponded with the dust layer of the snow pit. It was observed that about 42% of Hg was lost from the surface snow when the glacier was exposed to sunlight within the first 24 h indicating some Hg was emitted back to the atmosphere while some were percolated downwards. The result from the principal component analysis (PCA) showed that the sources of Hg in Laohugou Glacier No. 12 were from crustal and biomass burning. Finally, it was estimated that total export of Hg from the outlet river of Laohugou glacier No. 12 in the year 2015 was about 1439.46 g yr−1 with yield of 22.77 μg m2 yr−1. This study provides valuable insights for understanding the behavior of Hg in the glacier of the northern Tibetan Plateau.

This study investigates the bathymetry of three major lakes and the water quality of nine lakes at Ramaroshan Lake Complex Area (RLCA), Far-Western Nepal. Lakes were surveyed based on line transects using Echosounder (depth measuring gauge) and GPS to collect the data for bathymetry. Water samples were collected from 43 sites of nine lakes, considering the land use patterns, anthropogenic activities, inlets, and outlets. Twenty physico-chemical parameters were analyzed to know the water characteristics and pollution level. The bathymetry map showed that Jingale is the deepest lake (44 m), followed by Batula (15 m) and Mathillo Dhaune (9.5 m). There was no significant spatial variability in the concentration of physicochemical parameters among the sampling sites. The mean concentrations of cations and anions were in the order of Ca2+> Mg2+> Na+> K+, and HCO3-> Cl-> SO42-> PO42-> NO3-, respectively. Principal component analysis (PCA) and cluster analysis (CA) techniques were applied to assess the influence of pollution levels and their controlling mechanism. PCA showed 79.89 % of the cumulative variance with > 1.26 Eigenvalue. Similarly, CA showed that Jingale Lake (in cluster 2) sites were less polluted than other sampling sites. Piper diagram concluded that there was a dominance of mixed water type belonging to Ca-Mg-Cl compared to Ca-HCO3. Furthermore, the Water Quality Index (WQI) value of the lakes in the study area was 27 indicating good water quality (slightly polluted).

Water quality analysis of the Himalayan rivers for irrigation was carried out in 2013 that include the Dudh Koshi, Indrawati, Gandaki and Bagmati rivers from Nepal. Former three rivers originate at high altitudes and are glacier-fed rivers, whereas the Bagmati River originates at the high hill and flows through the capital city of Nepal. The river water samples were collected at 93 sites representing river from lowlands, mid-hills and high mountains of the Himalayas. Nine major ions (Na+, K+, Mg2+, Ca2+, F−, Cl−, $${\text{SO}}_{4}^{2 - }$$ , $${\text{HCO}}_{3}^{ - }$$ and $${\text{NO}}_{3}^{ - }$$ ), pH, EC and TDS were analyzed so as to assess the water quality for irrigation. Irrigation water quality was assessed by calculating sodium adsorption ration (SAR), soluble sodium percentage (SSP or %Na) and water quality index (WQI). Although SAR indicated that all the water samples were having low values and could be suitable for the irrigation purpose, some sites from the Bagmati River were having high class of EC, rendering it not good for irrigation. Similar results were indicated by %Na as well as WQI results where low water qualities were observed from some highly contaminated sites in the city area. This clearly indicates the impacts of urbanization (anthropogenic) in river water quality for the irrigation in the Himalayan rivers of Nepal.

This study explores an understanding of human-wildlife conflict (HWC) focused on tiger, particularly the status and trend of human-tiger conflict (HTC), in three major areas of Chitwan National Park (CNP); Ayodhyapuri, Patihani and Meghauli VDCs. A set of questionnaire survey was conducted in 98 households [Ayodhyapuri (38), Patihani (30) and Meghauli (30)]. Additionally, key informant interviews were conducted and official records of CNP, National Trust for Nature Conservation (NTNC) and Department of National Park and Wildlife Conservation (DNPWC) during month of June- July, 2017 were referred. Records from 2003 to 2015 at CNP shows that highest HTC was recorded in the year 2003-2004 (235 cases), out of which human casualties were 22 (4 injured and 18 killed). The trend has declined thereafter with the lowest conflict recorded in the year 2013-2014 (17 cases), out of which human casualties were 6 (4 injured and 2 killed). A significantly higher human-tiger interaction was recorded in Ayodhypuri compared to other two study sites (χ2 = 7.88; d.f. = 2; p = 0.02). However, a contradictory trend was obtained based on our survey owing to the long compensation procedure (51.02%), less compensation (30.61%) and weak information flow (18.36%). Besides, the development of dense community forest lured the tigers to the nearby buffer zone causing conflicts with tigers. Nevertheless, the perception of respondent relative to tiger conservation was found to be positive. Conservation education, awareness programs along with adequate and prompt compensation against damages coupled with regular/timely monitoring of tigers may help to reduce human-tiger conflicts. Keywords: Human-tiger conflict; Compensation; Livestock depredation; Retaliation

Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury (PBM) and the corresponding seasonality, sources, and influencing factors. The PBM concentration in total suspended particulate (TSP) matter ranged from 6.8 pg m−3 to 351.7 pg m−3 (mean of 99.7 ± 92.6 pg m−3), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content (PBM/TSP) ranged from 68.2 ng g−1 to 1744.8 ng g−1 (mean of 446.9 ± 312.7 ng g−1), indicating anthropogenic enrichment. The PBM levels were higher in the dry season (i.e., winter and the pre-monsoon period) than in the wet season (i.e., the monsoon period). In addition, the δ202Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ199Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 μg m−2 yr−1. This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.

Stable isotope ratios of nitrogen (δ15N, ‰) and carbon (δ13C, ‰), accompanied by stomach contents were used to assess the food chain and trophic transfer of mercury in fifty-three marketable sized fish belonging to five species (Channa punctatus, Mystus vittatus, Nandus nandus, Puntius sophore and Xenentodon cancila) from the Jagadishpur Reservoir, Nepal. The highest total Hg concentration was found in X. cancila with an average of 800.42(±279.36) µg/kg exceeding the international marketing limit (500 mg/kg), a carnivorous species. However, except for some individuals of N. nandus, total Hg concentrations in other fish species in the present study were significantly lower than that limit. The fish community had at least two trophic levels (Δ15N > 5.6), C. punctatus with the highest and M. vittatus the lowest signatures of δ15N, which was also supported by the stomach content analysis. There was neither correlation between total Hg and δ15N nor connectivity in food resource utilization (based on δ13C), indicating no biomagnification among these fish species. In addition, Hg concentrations were not significantly correlated to total fish length in any of the species. Fish species in the present study have low Hg content accompanied by low biomagnification through the studied fish community.

The unique geographic location of Mt. Yulong in the Tibetan Plateau (TP) makes it a favorable site for mercury (Hg) study. Various snow samples, such as surface snow, snow pit, and snowmelt water were collected from Mt. Yulong in the southeastern TP. The average concentration of Hg was found to be 37 ± 26 ng L−1 (mean ± SD), comparable to Hg concentration from other parts of TP in the same year, though it was comparatively higher than those from previous years, suggesting a possible increase of Hg concentration over the TP. The concentration of Hg was higher in the lower elevation of the glaciers possibly due to the surface melting concentration of particulates. Higher concentration of Hg was observed in the fresh snow, suggesting the possibility of long-range transportation. The average concentration of Hg from the snow pit was 1.49 ± 0.78 ng L−1, and the concentration of Hg in the vertical profile of the snow pit co-varied with calcium ion (Ca2+) supporting the fact that the portion of Hg is from the crustal origin. In addition, the principal component analysis (PCA) confirmed that the source of Hg is from the crustal origin; however, the presence of anthropogenic source in the Mt. Yulong was also observed. In surface water around Mt. Yulong, the concentration of HgT was found in the order of Lashihai Lake > Reservoirs > Rivers > Swamps > Luguhu Lake. In lake water, the concentration of HgT showed an increasing trend with depth. Overall, the increased concentration of Hg in recent years from the TP can be of concern and may have an adverse impact on the downstream ecosystem, wildlife, and human health.

This study reports on the sources of atmospheric particle-bound mercury (HgP) in less studied regions of Nepal based on the analysis of stable mercury (Hg) isotopes in aerosol samples from two neighboring areas with high and low anthropogenic emissions (Kathmandu and Dhulikhel, respectively) during 2018. Although the Indian monsoon and westerlies are generally regarded as the primary carriers of pollutants to this region via the heavily industrialized Indo-Gangetic Plain, the concentrations of total suspended particles (TSP) and HgP in Kathmandu were higher than those in Dhulikhel, thus suggesting a substantial contribution from local sources. Both isotopic (δ200Hg and Δ199Hg) and non-isotopic evidence indicated that dust, waste burning, and industrial byproducts (without Hg amalgamation) were the major sources of Hg in Kathmandu during the study period. Mercury may have been transported via air masses from Kathmandu to Dhulikhel, as indicated by the similar organic carbon/elemental carbon ratios and seasonal trends of TSP and HgP in these two locations. Local anthropogenic sources were found to contribute significantly to atmospheric Hg pollution through dust resuspension. Therefore, dust resuspension should be considered when evaluating the long-range transport of air pollutants such as Hg, particularly in anthropogenically stressed areas.

This study reports for the first time a comprehensive analysis of nitrogenous and carbonaceous aerosols in simultaneously collected PM

In this work, samples of surface snow, surface ice, snow pit and meltwater from the Laohugou Glacier No. 12 on the northern edge of Tibetan Plateau (TP) were collected during the summer of 2015. The average concentration of Hg in surface snow/ice was 22.41 ng L

Precipitation represents an important phenomenon for carbon and nitrogen deposition. Here, the concentrations and fluxes of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) with their potential sources were analyzed in wet precipitation during summer monsoon from the Northern Indo-Gangetic Plain (IGP), important but neglected area. The volume-weighted mean (VWM) concentration of DOC and TDN were 687.04 and 1210.23 µg/L, respectively. Similarly, the VWM concentration of major ions were in a sequence of NH4+ > Ca2+ > SO42- > Na+ > K+ > NO3− > Cl− > Mg2+ > F− > NO2−, suggesting NH4+ and Ca2+ from agricultural activities and crustal dust played a vital role in precipitation chemistry. Moreover, the wet deposition flux of DOC and TDN were 9.95 and 17.06 kg/(ha⋅year), respectively. The wet deposition flux of inorganic nitrogen species such as NH4+-N and NO3−-N were 14.31 and 0.47 kg/(ha⋅year), respectively, demonstrating the strong influence of emission sources and precipitation volume. Source attribution from different analysis suggested the influence of biomass burning on DOC and anthropogenic activities (agriculture, animal husbandry) on nitrogenous species. The air-mass back trajectory analysis indicated the influence of air masses originating from the Bay of Bengal, which possibly carried marine and anthropogenic pollutants along with the biomass burning emissions to the sampling site. This study bridges the data gap in the less studied part of the northern IGP region and provides new information for policy makers to deal with pollution control.

Diatoms were investigated in the littoral of Rara Lake, Nepal, to investigate the impact of land use, substratum type and season. Species composition and diversity differed between areas, seasons and between stones, sediment and macrophytes. Both communities on stones and on sediment differed between the settlement and forested areas, but communities on stones showed the greatest differentiation between land use types.

Mercury (Hg) and lead (Pb) accumulation since the Industrial Revolution has been generally observed to increase concurrently in lake sedimentary records around the world. Located downwind during the monsoon season from the rapidly developing South Asia, the Himalayas and the Tibetan Plateau are expected to receive direct anthropogenic Hg and Pb loadings, yet the source, pathway, and effects of such transport remain poorly known due to logistic challenges in accessing this region. When studying the sediment record from Lake Gokyo (4750 m above sea level (a.s.l.)) in the Himalayas, we find remarkably different Hg and Pb accumulation trends over the past 260 years. Although Hg accumulation has continued to increase since the Industrial Revolution, Pb accumulation peaked during that time and has been decreasing since then. Stable isotope analysis reveals that the decoupling trends between these two elements are due to different sources and pathways of Hg and Pb in the region. Both δ

During the first study of the diverse diatom assemblages in Rara Lake, the largest lake in Nepal, 11 species of Gomphonema, belonging to six morphological groups, and Gomphoneis qii could be invest...

The fragile Himalayan region could be regarded as the sink for various pollutants transported from urbanized and polluted areas of South Asia. Therefore, in order to understand the concentrations, spatial distribution, pollution, and risk assessments of toxic heavy metal, mercury (Hg), surface soil samples were taken from the central Himalayas in the Langtang region. The average THg concentration in the Langtang Himalayas was 35.75 ± 24.41(ngg⁻¹), which is comparable to the Tibetan top soil values and slightly lower than world average soil values. In addition, an inverse relationship of THg with elevation were observed (i.e. decrease in concentration with increase in elevation) in the Langtang Himalayan soils. Meanwhile, THg concentrations and TOC% were significantly positively correlated at both the depths (0–10 and 10–20 cm), inferring the sorption capacity of organic carbon for Hg. The results of the geo-accumulation index (Igₑₒ), enrichment factor (EF), and pollution index (PI) indicated limited or no pollution by Hg in the Himalayan soils. Further, surface soils had a low potential ecological risk in the region. Therefore, the Hg value from this study could be used for the further evaluation and calculation of Igₑₒ, EF, and PI for water, soil, and aerosol in the Himalayan region as background reference value. However, Hg pollution from long-range transport and atmospheric deposition (wet/dry) in future could not be ignored in the Himalayan region.

The study was conducted to assess the impacts of trout farming on water quality using macro invertebrates as bio-indicators. Two trout farms were selected for the study, viz., Gandaki Trout Farm (GTF) in Kaski district and Fall & Trout Fish Farm (FTF) in Nuwakot district. Reference and impacted sites were selected in each trout farms from where macro invertebrates were collected and physico-chemical parameters were measured. Sorensen’s Index and Multiple Site Similarity Index were calculated to compare the macro-invertebrate assemblages between the impact and the reference sites. Water quality classes were also calculated using macro invertebrate-based tool, NEPBIOS/ASPT scores. Altogether 24 families of macro invertebrates were observed at GTF and 12 families at FTF. The Sorensen’s Similarity Index was greater than 0.5 between reference and impacted sites at GTF; whereas it was only 0.28 at FTF indicating comparatively low level of similarity. In addition, Multiple Site Similarity Index (0.64) at GTF also indicated high similarity between the macro invertebrate assemblages. Reference sites showed higher scores with higher diversity of macro invertebrates. Both farms had suitable water quality for trout (dissolved oxygen and temperature) and most of the physico-chemical parameters did not show significant differences except pH and turbidity at GTF probably due to small scale operation and production. Journal of Institute of Science and TechnologyVolume 22, Issue 2, January 2018, Page: 175-182

Carcinogenic risk assessments of polycyclic aromatic hydrocarbons (PAHs) in four sites from the Central Himalayas (Bode, Lumbini, Pokhara, and Dhunche) were performed. Lifetime Average Daily Dose (...

This study quantified concentrations of mercury (Hg) and its trophic transfer along the fish community in the Indrawati River, Nepal. Stable isotope ratios of nitrogen (δ15N) and carbon (δ13C), complemented by stomach contents data were used to assess the food web structure and trophic transfer of Hg in 54 fishes; 43 Shizothorax richardsonii and 11 Barilius spp. [B. bendelisis (1), B. vagra (3) and B. barila (7)]. Sixty-one muscle samples (including six replicates) were used for the analysis of total mercury (THg) and stable isotopes. Mean THg concentrations in B. spp. and the more common species S. richardsonii was observed to be 218.23 (ng/g, ww) and 90.82 (ng/g, ww), respectively. THg versus total length in both S. richardsonii and B. spp. showed a decreasing tendency with an increase in age. Regression of logTHg versus δ15N among the fish species showed a significant positive correlation only in S. richardsonii indicating biomagnification along the trophic level in this species.

The concentration of 13 metals (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Pb, and Hg) and their associated health risk assessment was performed for two Himalayan lakes, urban Phewa and remote Gosainkunda, from Nepal. Water Quality Index (WQI), Metal Index (MI), Hazard Quotient (HQ), Hazard Index, and Cancer Risk were calculated in order to evaluate the water quality of these lakes. Correlation analysis revealed that Mn and Fe were derived from natural geological weathering processes and Pb, V, Cr, Co, Ni, Cu, Zn, and Cd might have originated from anthropogenic sources. The results revealed that WQI of the remote lake fell into excellent water quality and urban lake fell into poor water quality, which is also supported by the MI calculation. Moreover, the HQ of Mn in urban lake showed values greater than unity suggesting its health risk to the local inhabitants. The cancer index values indicated “high” risk due to Cr, whereas Cd possesses “very low” cancer risk on local population residing nearby ...

The water quality of the river basins in the Third Pole has a direct impact on the well-being of millions of people. Rivers are critical bonds for nutrients, such as organic carbon and nitrogen cycles, in the aquatic, terrestrial, and atmospheric environments. In this chapter, riverine organic carbon and nitrogen exports in nine large rivers on the Tibetan Plateau (TP)—the “water tower of Asia”—are introduced. Compared with the world average, the concentrations of dissolved organic carbon (DOC, 1.16 mg L−1) are at the low end, which is likely because of the low temperature and unproductive land vegetation environments. However, the average concentrations of dissolved organic nitrogen (DON 0.35 mg L−1) in this region are close to the world average. It is noticeable that, despite its dominant pristine environment, discharge from agricultural activities and urban areas has raised riverine N export. In addition, the DOC/DON ratio (C/N, ~6.5) was much lower than the global average, indicating that DOC in the rivers of the TP might be more bioavailable. Only a few studies on persistent organic pollutants (POPs) have been carried out in rivers of the Third Pole region. Nevertheless, there are few datasets to understand the levels and spatial distribution of these pollutants over the region. The concentration of POPs in the Koshi River basin was much higher than that in the remote areas and it was comparable to rivers in remote parts of India, however, much lower levels were observed than in the rivers in polluted areas of India. Furthermore, total suspended/insoluble particles in rivers are an emerging area of interest in river system monitoring as carriers of water pollutants. However, there is scant information on this matter in the Third Pole region. Insufficient measuring systems and lack of attention to total suspended solids and water turbidity has rendered inadequate information about pollution loads and water quality, and hence this has caused a severe impact on health, environment, and ecosystem.

The “Third Pole,” centered on the Tibetan Plateau, is also known as the “Water Tower of Asia.” The Third Pole region feeds more than 10 large rivers (e.g., the Yellow River, the Yangtze River, the Yarlung Tsangpo, the Indus, the Amu Darya, etc.) in Asia and there are more than one billion people dependent on the water resources provided by these river basins. In this chapter, an overview of the water chemistry and the geochemical mechanisms that govern the characteristics of major ions and trace elements in rivers of the Third Pole are presented. In general, most rivers of the Third Pole have an alkaline water environment with an average pH of 8.7. As a result of intensive rock weathering within the catchments, the averaged total dissolved solids (~380 mg L−1) in the rivers of the Third Pole are much higher than the global median level. It was found that the dissolved contents in rivers of the Third Pole are dominated by Ca2+, Mg2+, HCO3−, Cl−, and SO42− with a spatial heterogeneity due to the different climates, hydrography, and geology conditions over the region. The main mechanisms that control the water chemistry in the rivers of the Third Pole are natural processes, such as rock weathering, ground discharge, and evaporation-crystallization, and most of the rivers remain pristine. However, it should be noted that due to human factors, such as urbanization and mining operations, toxic elements such as As, Cd, Hg, Mn, and Pb concentrations in some of the rivers in the Third Pole are higher than the permissible limits for drinking water as established by the WHO. With increasing anthropogenic activities and changes within the river basins of the Third Pole, further monitoring of the hydrochemical compositions in rivers over this eco-fragile region is warranted.

This chapter highlights important findings on precipitation chemistry including spatial distribution, seasonality and possible sources of major ions, trace elements, toxic heavy metal (e.g., mercury), and carbonaceous species in wet deposition over the Third Pole (TP) region. In general, similar seasonal variations were observed for all the components in precipitation with higher concentrations in nonmonsoon and lower concentrations during monsoon seasons. The influence of a recent increase in anthropogenic activities can be clearly observed in the enhanced concentrations of certain ions (e.g., SO42−, NO3−, and NH4+), trace metals, mercury, and dissolved organic carbon (DOC) in atmospheric wet precipitation. Moreover, the light absorption characteristic of precipitation DOC and its role on climate forcing are presented. The transport pathways of inorganic and carbonaceous species in wet precipitation indicate that DOC in precipitation over the TP was mainly influenced by combustion emissions in South Asia and local Tibetan residents. This chapter could act as the base for precipitation chemistry over the TP and direct for future needs of studies into this fragile region.

Black carbon (BC) is one of the major drivers of climate change, and its measurement in different environment is crucial for the better understanding of long-term trends in the Himalayan–Tibetan Plateau (HTP) as climate warming has intensified in the region. We present the measurement of BC concentration from six lake sediments in the HTP to reconstruct historical BC deposition since the pre-industrial era. Our results show an increasing trend of BC concurrent with increased anthropogenic emission patterns after the commencement of the industrialization era during the 1950s. Also, sedimentation rates and glacier melt strengthening influenced the total input of BC into the lake. Source identification, based on the char and soot composition of BC, suggests biomass-burning emissions as a major contributor to BC, which is further corroborated by open-fire occurrence events in the region. The increasing BC trend continues to recent years, indicating increasing BC emissions, mainly from South Asia.

Glaciochemical records serve as one of the best archives and as good proxies to indicate regional and global anthropogenic influences. The Himalayas, with fragile ecosystems and pristine environments, hold the third largest reservoir of glacier ice and represent an ideal region to investigate trace metal pollution using glacier records. Limited studies on glacially recorded trace metals in the Himalayas usually collect samples from individual glaciers and report a few trace metals in different seasons. We provide a comprehensive and in-depth understanding of the glacially recorded trace metals in the central Himalayas regarding their spatial distribution, seasonal variability, and anthropogenic signals. We analyzed six representative metals (Cu, Zn, Cd, Cr, Pb, Co) and found that the trace metal concentration range largely varied between the studied metals and sampling sites. The Zn metal concentration is higher, attributed to the contribution of natural sources (e.g., forest fires, dust storms) and anthropogenic sources, including industrial and traffic-related emissions. The Pb concentration showed striking seasonality due to the relatively natural input of local material during the monsoon season and the regional and long-range transport of anthropogenic sources during the non-monsoon season. There was a clear spatial variation in certain trace metals, such as Cu, Zn, and Pb, showing decreasing trends with increasing elevation. The enrichment factor (EF) results showed that Zn metal was highly enriched, followed by Cu and Cd, indicating that Zn metal was relatively highly susceptible to intensified human activities. The seasonal paradox between the enrichment factor and metal concentration revealed that the EF of the monsoon season was usually higher than that of the non-monsoon season, and vice versa regarding metal concentrations primarily associated with metal deposition in regional climate regimes, particularly atmospheric circulation. We suggest that the analytical method can influence the trace metal concentration and EF calculation, resulting in a previously unrecognized bias in the seasonality of trace metals. Future research should prioritize stable isotopes of trace elements (e.g., Pb, Cu) in glaciers that would provide valuable information in identifying the potential source of anthropogenic inputs and the degree of extent affecting the glaciochemistry of the Himalayas.

Atmospheric nitrogen is ubiquitous in the environment and hence plays an essential role in the nutrient balance over the whole ecosystem. However, its abundance and characteristics, particularly in the Himalayas, are not well understood. Therefore, to understand the abundance, sources, and seasonality of soluble nitrogenous species in the middle hills of the central Himalayas, aerosol samples were collected at Dhulikhel in Nepal from January to December 2018. The results of this study revealed that water-soluble inorganic nitrogen (WSIN) contributed the most to water-soluble total nitrogen with an abundance of ammonium nitrogen (NH4+–N). Moreover, water-soluble organic nitrogen (WSON) contributed approximately 18% to aerosol total water-soluble nitrogen. The aerosol mass and WSIN species exhibited strong seasonality with considerably higher concentrations during dry periods and lower concentrations during the wet period. Furthermore, for dry periods, the HYSPLIT model revealed that nitrogen aerosols mainly originated from the Indo-Gangetic Plain region and were transported and deposited in the Himalayas through long-range atmospheric transport. The strong correlations of WSON with nss K+ (biomass burning) and nss Ca2+ (crustal sources) and lack of a significant correlation with SO42− indicated that primary sources are responsible for generating WSON rather than secondary processes in the Himalayas. The estimated dry deposition fluxes for NO3−–N, NH4+–N, and WSON were 1.56, 8.35, and 4.06 kg ha−1 y−1, respectively. This study also shows that increasing air contaminants and emissions over South Asia can enter the Himalayas and affect the human health and ecology of this fragile area.

This study investigates the contamination levels and risk assessments of 14 elements (Ba, Cd, Co, Cr, Cu, Pb, Li, Mn, Mo, Ni, Sb, Sr, V and Zn) in three sub-basins of Himalayan rivers. Water samples were collected and the hazard quotient (HQ), hazard index (HI), and water quality index (WQI) were calculated. Total average concentrations of the metals were 135.03, 80.10 and 98.34 µg/L in Gandaki, Indrawati and Dudh Koshi rivers, respectively. The results of HQ and HI were less than unity, suggesting a low risk of metals in the region. However, HQ for antimony (Sb) was found to be 4.4 × 10-1, 2.1 × 10-1 and 5.4 × 10-1 in three river basins and HI near unity, suggesting its potential risk. Additionally, HI for Cd in Indrawati was 5.4 × 10-1 also close to unity, suggesting that Cd could have a potential risk to the local residents and aquatic ecosystems. Further, WQI suggested that the rivers Gandaki and Indrawati fell into the excellent water quality and river Dudh Koshi fell into good water quality.

Lake water and fish livers and gills of sahar (Tor putitora), spiny eel (Mastacembelus armatus), African magur (Clarias gariepinus), and tilapia (Oreochromis niloticus) from Lake Phewa, Nepal, were assessed for the concentrations of trace metals/elements and persistent organic pollutants. The lake water was neutral with low ionic and metallic concentrations as compared to high-altitude lakes of Nepal. The four elements Cu, Zn, Se, and Cd had highest concentrations in livers, indicating uptake from diet, whereas four other metallic elements Cr, Mn, Ni, and Pb had highest concentrations in gills, indicating uptake from lake water. O. niloticus tended to have most of trace metals in the liver at higher concentrations than the other species but significant differences among the different species were found only for Mn, Ni, and Zn in the gills. A pilot study on the concentrations of persistent organic pollutants in muscle revealed that dichlorodiphenyltrichloroethane and related compounds were the domi...

The fragile Himalayan region could be regarded as the sink for various pollutants transported from urbanized and polluted areas of South Asia. Therefore, in order to understand the concentrations, spatial distribution, pollution, and risk assessments of toxic heavy metal, mercury (Hg), surface soil samples were taken from the central Himalayas in the Langtang region. The average THg concentration in the Langtang Himalayas was 35.75 ± 24.41(ngg−1), which is comparable to the Tibetan top soil values and slightly lower than world average soil values. In addition, an inverse relationship of THg with elevation were observed (i.e. decrease in concentration with increase in elevation) in the Langtang Himalayan soils. Meanwhile, THg concentrations and TOC% were significantly positively correlated at both the depths (0–10 and 10–20 cm), inferring the sorption capacity of organic carbon for Hg. The results of the geo-accumulation index (Igeo), enrichment factor (EF), and pollution index (PI) indicated limited or no pollution by Hg in the Himalayan soils. Further, surface soils had a low potential ecological risk in the region. Therefore, the Hg value from this study could be used for the further evaluation and calculation of Igeo, EF, and PI for water, soil, and aerosol in the Himalayan region as background reference value. However, Hg pollution from long-range transport and atmospheric deposition (wet/dry) in future could not be ignored in the Himalayan region.