Pollution of riverine ecosystems through the multidimensional impact of human footprints around the world poses a serious challenge. Research studies that communicate potential repercussions of landscape structure metrics on snowmelt riverine water quality particularly, in climatically fragile Himalayan watersheds are very scarce. Though, worldwide, grasping the influence of land-use practices on water quality (WQ) has received renewed attention yet, the relevance of spatial scale linked to landscape pattern is still elusive due to its heterogenic nature across diverse geomorphic regions. In this work, therefore, we tried to capture the insights on landscape-aquascape interface by juxtapositioning the impacts of landscape structure pattern on snowmelt stream WQ of the whole Jhelum River Basin (JRB) under three varying spatial scales viz., watershed scale, riparian corridor (1000 m wide) and reach buffer (500 m wide). The percentage of landscape pattern composition and configuration metrics in the JRB were computed in GIS utilizing Landsat-8 OLI/TIRS satellite image having 30 m resolution. To better explicate the influence of land-use metrics on riverine WQ with space and time, we used Redundancy analysis (RDA) and multilinear regression (MLR) modeling. MLR selected land-use structure metrics revealed the varied response of WQ parameters to multi-scale factors except for total faecal coliform bacteria (TC) which showed perpetual presence. The reach-scale explained slightly better (76%) variations in WQ than riparian (75%) and watershed (70%) scales. Likewise, across seasonal scale, autumn (75%), winter (83%), and summer (77%) captured the most WQ variation at catchment, riparian, and reach scales respectively. We observed impairing WQ linkages with agriculture, built-up and barren rocky areas across watersheds, besides, pastures in riparian buffer areas, and fragmentation of landscape patches at the reach scale. Due to little appearance of spatial scale differences, a multi scale perspective landscape planning is emphasized to ensure future sustainability of Kashmir Himalayan water resources.

Atmospheric aerosols play a crucial role in climate change, especially in the Himalayas and Tibetan Plateau. Here, we present the seasonal and diurnal characteristics of aerosol vertical profiles measured using a Mie lidar, along with surface black carbon (BC) measurements, at Mt. Qomolangma (QOMS), in the central Himalayas, in 2018–2019. Lidar-retrieved profiles of aerosols showed a distinct seasonal pattern of aerosol loading (aerosol extinction coefficient, AEC), with a maximum in the pre-monsoon (19.8 ± 22.7 Mm⁻¹ of AEC) and minimum in the summer monsoon (7.0 ± 11.2 Mm⁻¹ of AEC) seasons. The diurnal variation characteristics of AEC and BC were quite different in the non-monsoon seasons with enriched aerosols being maintained from 00:00 to 10:00 in the pre-monsoon season. The major aerosol types at QOMS were identified as background, pollution, and dust aerosols, especially during the pre-monsoon season. The occurrence of pollution events influenced the vertical distribution, seasonal/diurnal patterns, and types of aerosols. Source contribution of BC based on the weather research and forecasting chemical model showed that approximately 64.2% ± 17.0% of BC at the QOMS originated from India and Nepal in South Asia during the non-monsoon seasons, whereas approximately 47.7% was from local emission sources in monsoon season. In particular, the high abundance of BC at the QOMS in the pre-monsoon season was attributed to biomass burning, whereas anthropogenic emissions were the likely sources during the other seasons. The maximum aerosol concentration appeared in the near-surface layer (approximately 4.3 km ASL), and high concentrations of transported aerosols were mainly found at 4.98, 4.58, 4.74, and 4.88 km ASL in the pre-monsoon, monsoon, post-monsoon, and winter seasons, respectively. The investigation of the vertical profiles of aerosols at the QOMS can help verify the representation of aerosols in the air quality model and satellite products and regulate the anthropogenic disturbance over the Tibetan Plateau.

After decades of imposed regulations about reducing the primary emissions of persistent organic pollutants (POPs), these pollutants are still present in the environment. Soils are important repositories of such persistent semivolatile organic contaminants (SVOCs), and it is assumed that SVOCs sequestered in these reservoirs are being re-mobilized due to anthropogenic influence. In this study, concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in soil and air, their fugacities, fluxes and the soil-air partition coefficient (KSA) were determined for three different land cover types (glacial, remote/mountainous and urban) of the Lesser Himalayan Region (LHR). The concentrations of OCPs, PCBs and PBDEs in soils and air ranged between 0.01 and 2.8, 0.81–4.8, 0.089–0.75 ng g⁻¹; 0.2–106, 0.027–182, and 0.011–7.26 pg m⁻³, respectively. The levels of SVOCs in the soil were correlated with soil organic matter (SOM) indicating that SOM is a substrate for the organic pollutants in soils. The Clausius-Clapeyron plots between ln P and inverse of temperature (1000/T) suggested that long range atmospheric transport was the major input source of PBDEs and higher chlorinated PCBs over the LHR. The uneven and wide distribution of local sources in LHR and up-slope enrichment of SVOCs explained the spatial variability and altitudinal patterns. The soils near mountain and urban lakes act as local sinks of SVOCs such as β-HCH, pp΄-DDT, CB-28, -118, −153, BDE-47, -99, and −154, with soil-air exchange fluxes tending more toward deposition. However, the soils near glacial lakes acted as local sources of more volatile congeners of α-HCH, γ-HCH, op′-DDT, pp′-DDE and lower to medium chlorinated PCBs such as CB-18, -28, −53, −42 and BDE-47, -99, with soil-air exchange tending more toward volatilization flux.

The concentration and isotopic composition of mercury (Hg) were studied in frozen soils along a southwest-northeast transect over the Himalaya-Tibet. Soil total Hg (HgT) concentrations were significantly higher in the southern slopes (72 ± 54 ng g−1, 2SD, n = 21) than those in the northern slopes (43 ± 26 ng g−1, 2SD, n = 10) of Himalaya-Tibet. No significant relationship was observed between HgT concentrations and soil organic carbon (SOC), indicating that the HgT variation was not governed by SOC. Soil from the southern slopes showed significantly negative mean δ202Hg (−0.53 ± 0.50‰, 2SD, n = 21) relative to those from the northern slopes (−0.12 ± 0.40‰, 2SD, n = 10). The δ202Hg values of the southern slopes are more similar to South Asian anthropogenic Hg emissions. A significant correlation between 1/HgT and δ202Hg was observed in all the soil samples, further suggesting a mixing of Hg from South Asian anthropogenic emissions and natural geochemical background. Large ranges of Δ199Hg (−0.45 and 0.24‰) were observed in frozen soils. Most of soil samples displayed negative Δ199Hg values, implying they mainly received Hg from gaseous Hg(0) deposition. A few samples had slightly positive odd-MIF, indicating precipitation-sourced Hg was more prevalent than gaseous Hg(0) in certain areas. The spatial distribution patterns of HgT concentrations and Hg isotopes indicated that Himalaya-Tibet, even its northern part, may have been influenced by transboundary atmospheric Hg pollution from South Asia.

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause.The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Continuous measurements of Black Carbon (BC) aerosol mass concentrations were carried at Dehradun (30.33°N, 78.04°E, 700 m amsl), a semi-urban site in the foothills of north-westHimalayas, India during January 2011–December 2017. We reported both the BC seasonal variations as well as mass concentrations from fossil fuel combustion (BCff) and biomass burning (BCbb) sources. Annual mean BC exhibited a strong seasonal variability with maxima during winter (4.86 ± 0.78 μg m⁻³) followed by autumn (4.18 ± 0.54 μg m⁻³), spring (3.93 ± 0.75 μg m⁻³) and minima during summer (2.41 ± 0.66 μg m⁻³). Annual averaged BC mass concentrations were 3.85 ± 1.16 μg m⁻³ varying from 3.29 to 4.37 μg m⁻³ whereas BCff and BCbb ranged from 0.11 to 7.12 μg m⁻³ and 0.13–3.6 μg m⁻³. The percentage contributions from BCff and BCbb to total BC are 66% and 34% respectively, indicating relatively higher contribution from biomass burning as compared to other locations in India. This is explained using potential source contribution function (PSCF) and concentration weighted trajectories (CWT) analysis which reveals the potential sources of BC originating from the north-west and eastern parts of IGP and the western part of the Himalayas that are mostly crop residue burning and forest fire regions in India. The annual mean ARF at top-of-atmosphere (TOA), at surface (SUR), and within the atmosphere (ATM) were found to be −14.84 Wm⁻², −43.41 Wm⁻², and +28.57 Wm⁻² respectively. To understand the impact of columnar aerosol burden on ARF, the radiative forcing efficiency (ARFE) was estimated and averaged values were −31.81, −91.63 and 59.82 Wm⁻² τ⁻¹ for TOA, SUR and ATM respectively. The high ARFE within the atmosphere indicates the dominance of absorbing aerosol (BC and dust) over Northwest Himalayas.

Black carbon and total organic carbon (TOC) along with organochlorines (OCs) were analyzed in soils from four sampling zones of Lesser Himalayan Region based on source proximity/anthropogenic influences along the altitude. CTO-375 method was used for BC analysis while OCs were analyzed by GC-MS/MS system. BC and TOC ranged between 0.16–1.77 and 6.8–41.3 mg g−1 while those of OCPs and PCBs ranged between 0.69 and 5.77 and 0.12–2.55 ng g−1, respectively. ∑DDTs were the dominant (87.9%) among OCPs while tri- and tetra- (65.5%) homologue groups among PCBs. Hexa-PCBs, however also showed higher contribution (20.4%) in the region. Source diagnostic ratios of DDE + DDD/DDT (0.1–1.53) indicated both fresh and old input while α-HCH/γ-HCH (0.19–2.49) showed presence of lindane in the region. Higher concentration of OCs were observed in Zone C at altitudinal range of 737–975 masl that are close to the human influences and potential sources of POPs. The results of linear regression analysis revealed potential input of BC in soil distribution of OC concentrations in the region.

This study aims to assess the spatial patterns of selected dust-borne trace elements alongside the river Indus Pakistan, their relation with anthropogenic and natural sources, and the potential risk posed to human health. The studied elements were found in descending concentrations: Mn, Zn, Pb, Cu, Ni, Cr, Co, and Cd. The Index of Geo-accumulation indicated that pollution of trace metals were higher in lower Indus plains than on mountain areas. In general, the toxic elements Cr, Mn, Co and Ni exhibited altitudinal trends (P < 0.05). The few exceptions to this trend were the higher values for all studied elements from the northern wet mountainous zone (low lying Himalaya). Spatial PCA/FA highlighted that the sources of different trace elements were zone specific, thus pointing to both geological influences and anthropogenic activities. The Hazard Index for Co and for Mn in children exceeded the value of 1 only in the riverine delta zone and in the southern low lying zone, whereas the Hazard Index for Pb was above the bench mark for both children and adults (with few exceptions) in all regions, thus indicating potential non-carcinogenic health risks. These results will contribute towards the environmental management of trace metal(s) with potential risk for human health throughout Pakistan.

Mercury (Hg), as a global pollutant, its contamination has been documented in environmental compartments of the Himalayan region. However, little research exists regarding to Hg accumulation in terrestrial wildlife, as well as its driving factors. In this study, surface soil and small mammals were collected in the Lebu Valley, East Himalayas of China, in order to measure the uptake of the long-distance transported Hg along an elevational gradient approximately from 2300 to 5000 m a.s.l. The soil Hg concentrations were measured and predicted mostly by vegetation type as well as soil organic matter, while the Hg in hair of small mammals (Muridae and Cricetidae) showed deeply influenced by soil Hg. Notably, combined with the field survey data, soil and hair Hg were both enhanced in low and mid-elevations, which overlapped the distribution ranges of a majority of mammals. Overall, this indicates that Hg contamination in low- and mid-elevations poses a potential threat to the top predators that consuming small mammals directly or indirectly. Furthermore, our data advances the understanding of Hg dynamics in remote, high mountain ecosystems and provides baseline data for biomonitoring for reduction of Hg emission globally.

Studies of microplastics (MPs) in remote, trans-boundary and alpine rivers are currently lacking. To understand the sinks and transport mechanisms of MPs, this study investigated the distributions and sources of MPs in the surface waters and sediments of five tributaries of the Koshi River (KR), a typical alpine river in the Himalayas between China and Nepal. Mean abundances of MPs in water and sediment were 202 ± 100 items/m³ and 58 ± 27 items/kg, dry weight, respectively. The upstream tributary, Pum Qu in China, had the smallest abundance of MPs, while the middle tributary, Sun Koshi in Nepal, had the greatest abundance. Compared to international values in rivers, contamination of the KR with MPs was low to moderate. Fibers represented 98% of all MP particles observed, which consisted of polyethylene, polyethyleneterephthalate, polyamide, polypropylene, and polystyrene. Blue and black MPs were prevalent, and small MPs (<1 mm) accounted for approximately 60% of all MPs. Atmospheric transmission and deposition were considered to be the principal sources of MPs in the upstream tributary. The results imply that point sources associated with mostly untreated sewage effluents and solid wastes from households, major settlements, towns, and cities were most important sources of MPs in the KR. Non-point sources from agricultural runoff and atmospheric transport and deposition in the middle stream tributaries also contribute a part of microplastics, while the least amount was from fishing in the downstream tributary. Urbanization, agriculture, traffic, and tourism contributed to pollution in the KR by MPs. Equations to predict abundances of MPs based on river altitudes revealed that different trends were affected by both natural and human factors within the KR basin. This study presents new insights into the magnitude of MP pollution of a remote alpine river and provides valuable data for developing MP monitoring and mitigation strategies in similar environments worldwide.