Interest in the origin and traceability of agri-food products has led to an increasing number of publications using strontium isotope ratios as a geographic tracer. We used 87Sr/86Sr isotope systematics to authenticate the provenance of wine from different volcanic districts of Italy. Samples of soil, grapes, leaves and bottled wines from 6 different wineries were analysed. A detailed study of the different soil horizons from the Somma-Vesuvio area demonstrates the relationship between the 87Sr/86Sr of the soils and the different parts of the grapevine (root, steam, grape, grape pulp, grape seed, grape skin), and the soil characteristics (soil type, granulometry, root density) that control the 87Sr/86Sr of the end-products. Results showed that the geological characteristics of volcanic terranes of Italy, and in particular the northwest to southeast 87Sr/86Sr gradient, are inherited by the wines of each region, such that the wines can be discriminated and authenticated by their isotope ratios.

Atmospheric phosphorus (P) is essential for nutrient-limited alpine ecosystems, yet its deposition processes over the Tibetan Plateau remain poorly understood. Here, event-based and sequential precipitation data from the southeastern Tibetan Plateau (3326 m a.s.l.) are presented to investigate and discuss the concentration, solubility, and removal dynamics of total phosphorus (TP) and total dissolved phosphorus (TDP). Results reveal volume-weighted mean TP and TDP concentrations of 9.14 mu g/L and 6.97 mu g/L, indicating a high P solubility (similar to 75%, TDP/TP) that may be partly attributed to biomass burning in South Asia. Scavenging analysis showed that below-cloud processes contributed 56-66% of P removal, and that scavenging coefficients for P species (1.50 & times; 10(-5)-6.53 & times; 10(-5) s(-1)) correlated with rainfall intensity, peaking at moderate rainfall intensities (similar to 2.0 mm/h). These findings provide a basis for improving wet deposition models parameterization and enhance insights into P transport dynamics under climate change.

Mass-independent fractionation (MIF) of sulfur (S) isotopes has been reported for tropospheric sulfate aerosols; however, the mechanisms responsible for these anomalies remain poorly constrained. Here, we present delta S-34 and Delta S-33 isotope compositions of sulfate aerosols (PM2.5) collected from two sites on the Himalayan-Tibetan Plateau (HTP) region, encompassing both the forest wildfire period and the nonwildfire period on the southern slopes of the Himalayas. Elevated Delta S-33 values were observed during the wildfire season at both QOMS and SETS, suggesting that forest wildfire emissions are an important contributor to sulfur MIF signals over the HTP. We hypothesize that at least two heterogeneous formation pathways contribute to the generation of S-MIF during the wildfire season: (i) a black carbon (BC)-catalyzed sulfate formation pathway associated with negative Delta S-33 anomalies, and (ii) a pathway linked to (NH4)(2)SO4 formation under NH3-rich conditions, marked by positive Delta S-33 anomalies. In addition, stratospheric intrusions contribute minimally to the observed Delta S-33 variability, with their signatures largely overprinted by wildfire-related processes, particularly in spring. Our results provide new observational constraints on sulfur isotope fractionation mechanisms in the modern troposphere and highlight the important role of wildfire-driven heterogeneous chemistry in modulating the atmospheric sulfur cycle over the HTP.

Iron nanoparticles (FeNPs) are an important but analytically challenging component of iron in glacier meltwater due to their low concentrations, high particulate loads, and strong dissolved iron backgrounds. Here, we optimized and validated a single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) method for the size-resolved characterization and quantification of FeNPs in glacier meltwater. By integrating SP-ICP-MS measurements with conventional operational definitions of iron fractions, the <0.45 μm dissolved iron pool is partitioned into nanoparticle iron and baseline dissolved iron. Additionally, when the dissolved Fe background is <0.37 ng mL-1, it provides a coherent framework compatible with established glacial geochemical datasets. Method evaluation demonstrates that both the filtration strategy and dissolved iron background exert first order controls on the detection of FeNPs. Results show that the 0.45 μm filtration offers the most robust balance between removing coarse-particle interference and retaining representative FeNPs populations. In contrast, finer filtration leads to their systematic underestimation, whereas not filtering samples elevates and distorts particle pulse intensities and inflates SP-ICP-MS-derived particle sizes. The application of the proposed optimized method to meltwaters from the Tibetan Plateau’s Kuoqionggangri and Rongbuk glacier systems reveals a consistent iron partitioning scheme, with particulate iron dominating total iron and FeNPs constituting a persistent but quantitatively subordinate fraction of the <0.45 μm pool. Despite variability in iron concentrations and hydrological settings, FeNPs exhibit stable modal particle diameters within the 19.6 to 46.8 nm range, indicating a reproducible nanometer-scale signature of glacially derived iron. Overall, this study establishes SP-ICP-MS as a robust and operationally constrained method for resolving iron nanoparticles in glacier meltwater and provides a practical basis for consistent size-resolved investigations of iron in cryospheric environments.

The climatic challenges faced by Pakistan, such as heat waves, glacier melting, and increased frequency of catastrophic floods, underscore the urgency of addressing climate change. Understanding historical climatic patterns, especially during the Holocene epoch, is crucial. Various proxy archives in Pakistan offer valuable resources for accurately reconstructing paleoclimatic conditions. This paper compiles and reviews available paleoclimate records to comprehensively understand Holocene climate variations in Pakistan, focusing on the Indian Summer Monsoon (ISM) and Westerly variations. While some proxies like tree rings have been well- studied, others, such as ice cores, peat, lake sediments, and speleothems, remain largely unexplored. Our synthesis indicates heightened frequency and intensity of extreme weather events in the past century, centennial- scale variations showing a shift from persistent dry conditions to punctuated wet periods, and notable climatic anomalies like the Medieval Warm Period/Anomaly (MWM) and the Little Ice Age (LIA). Mid-to-late Holocene witnessed decreased precipitation, possibly contributing to the decline of ancient civilizations. Early Holocene was comparatively more humid, with glacier advancements around 8-9 kyr BP (cal). The review advocates for generating high-resolution data and revisiting multiple sites across diverse climatic zones to refine climatic reconstructions.

Urolithiasis is a rather common pathology among the adult population and the biominerals it produces, i.e., urinary stones, may represent a potential proxy to characterize the environmental matrices that surrounded patients before being diagnosed. The objective of the present investigation (recently published in Izzo et al., 2024) was to use 87Sr/86Sr, a peculiar geochemical tracer routinely used for interpreting geological processes, to correlate the characteristics of patients’ urolith and their lifestyle habits, trying to identify correlations with direct or indirect contacts with their geological and environmental surroundings (water, soil, rock, etc.). Analyzed samples consisted of 21 kidney and bladder stones that were collected at the Department of Urology of the San Pio Hospital (Benevento, Italy) from patients living in Campania Region admitted between 2018 and 2020. Investigation was also extended to a vital food for humans such as water. Local tap waters and bottle waters (38 samples) from totally different Italian areas were here analyzed in order to highlight if and how different geological and hydrogeological settings could influence their Sr isotope ratio characterizing the connections existing between humans and their surrounding environment.The 87Sr/86Sr ratios of uroliths ranged from 0.70761 for an uricite sample to 0.70997 for a weddellite one and seem to be partly discriminated based on the mineralogy. The comparison with the isotope characteristics of Italian drinking waters shows a general overlap in 87Sr/86Sr with the biominerals. However, on a smaller geographic area (Campania Region), we observe small 87Sr/86Sr differences between the biominerals and local waters. This may be explained by external Sr inputs for example from agriculture practices, inhaled aerosols (i.e., particulate matter), animal manure and sewage, non-regional foods. Nevertheless, biominerals of patients that stated to drink and eat local water/wines and foods every day exhibited a narrower 87Sr/86Sr range roughly matching the typical isotope ratios of local geological materials and waters, as well as those of archaeological biominerals from the same area. This preliminary study evidences how the strontium isotope ratio of urinary stones records that of the patient's surrounding environmental matrices, although further investigations will be necessary to confirm this hypothesis. Izzo F., Di Renzo V., Langella A., D’Antonio M., Tranfa P., Widory D., Salzano L., Germinario C., Grifa C., Varricchio E., Mercurio M. (2024) Investigating strontium isotope linkage between biominerals (uroliths), drinking water and environmental matrices. Environmental Pollution, https://doi.org/10.1016/j.envpol.2024.123316

A total of 75 outdoor PM10, PM2.5, and PM1 samples from 14 schools, and 9 samples from potential local emission sources, were collected and analysed for their metallic content and lead (Pb) isotope ratios in 2 seasonal campaigns in Tarragona (Catalonia, Spain) to identify and apportion contamination sources and to assess associated health risks. Lead was predominantly found in PM1, and although its levels were below air quality standards, its Enrichment Factors (EF), along with those of other potentially toxic elements (Cd, Cr, Cu and Sb), indicated extremely severe enrichment in all PM sizes. Seasonal differentiation in Pb enrichment was particularly significant in PM1 during the cold campaign. This suggests an anthropogenic origin, mainly from combustion processes such as road traffic and a municipal solid waste incinerator, as supported by profiles of other metals (Cu, V and Zn) and the spatial distribution of the EFPb, respectively. Non-radiogenic Pb isotope ratios (Pb-208/Pb-204 and Pb-206/Pb-204) indicated a geogenic origin in some PM10 samples, based on their similarity to the geochronology of specific Spanish ore samples. However, radiogenic ratios (Pb-208/Pb-207 and Pb-206/Pb-207) pointed to coal-fired electrical plants (EGUs) and road traffic as the sources of the majority of the samples. These findings were corroborated by EF spatial distribution maps and by our previous study coupling air masses back trajectories with C and N isotopes in the same PM samples. Bayesian mixing models using both Pb-204- and Pb-207-normalised Pb isotope ratios estimated sources' contributions as follows: i) municipal solid waste incinerator (at least 10 % in PM10 and up to 60 % in both PM2.5 and PM1); ii) road traffic (up to 40 % for all size fractions); iii) coal-fired EGUs (around 20 % for all size fractions); and iv) geogenic particles (<10 % for all size fractions). Despite this strong contribution of anthropogenic sources, the potential health impacts of potentially toxic elements exposure were low, i.e., 3 additional cancer cases for adults per million of people due to Pb exposure, which nonetheless is comparable to levels observed in cities with populations 30 or more times larger than that of Tarragona.

In the Exposures in the Peace River Valley (EXPERIVA) study, pregnant individuals living in a region of natural gas exploitation had higher biological concentrations of certain trace elements, including strontium (Sr), than the general population. However, sources remained unidentified. To measure urinary 87Sr/86Sr isotope ratio in EXPERIVA participants, assess its reliability, and explore how its variance fluctuates based on Sr concentrations in biological (urine, hair, nails) and environmental (tap water) samples, as well as the density/proximity of unconventional oil and gas wells around participants’ residence. Participants provided urine daily over seven consecutive days. We measured 87Sr/86Sr in each urine sample from 7 participants and in pooled daily samples for all 75 participants. We used serial measurements to determine the intraclass correlation coefficient (ICC). We calculated the density/proximity of unconventional oil and gas wells around participants’ homes using inverse distance weighting (IDW). We assessed the variance of urinary 87Sr/86Sr based on Sr concentrations in biological/environmental samples and IDW through visual inspection and Levene’s test. We also performed unsupervised clustering to explore whether certain characteristics of the participants may be associated with a specific 87Sr/86Sr signature. Urinary 87Sr/86Sr ranged from 0.70798 to 0.71437. The ICC was 0.797 (95

Alkaline rocks of the Peshawar Plain Alkaline Igneous Province (PPAIP) constitute a major magmatic unit within the Indian plate in northwestern Pakistan. However, their tectonic settings, petrogenesis, and potential for associated rare metal mineralization remain poorly constrained. In this study, we present U-Pb zircon ages, mineral and whole-rock geochemical data, and Nd-Hf isotope compositions for the Baru granite and its associated pegmatite, providing new insights into their origin. Zircon U-Pb dating of the Baru granite and the pegmatite yielded crystallization ages of 270.6 +/- 1.7 Ma and 270.3 +/- 1.5 Ma, respectively. Zircon grains exhibit positive epsilon Hf(t) values, ranging from +4.1 to +7.3 for the Baru granite and from +5.2 to +10.0 for the pegmatite. The nearly identical ages and highly similar Hf isotope compositions indicate a co-magmatic origin for the granite and the pegmatite. Geochemically, the Baru granite is characterized by high SiO2, Rb, Nb, U, and Ta contents, low Yb/Ta, Y/Nb ratios, and positive bulk-rock epsilon Nd(t) values (+2.8 to +4.5). These features are consistent with fractionated anorogenic A-type granites derived from an OIB-like mantle source. Trace element compositions of zircons from the granite and the pegmatite exhibit systematic evolutionary trends, including increasing concentrations of HREEs, Hf, U, Y, Nb, and Ta, coupled with decreasing Eu anomalies and Ti concentrations. These trends strongly suggest that prolonged fractional crystallization of an alkaline magma, progressing from the granite to the pegmatite, was responsible for the enrichment of rare metals in the residual pegmatitic melt. The Baru granite shares similar emplacement ages and Hf-Nd isotope compositions with other Permian alkaline rocks in the NW Himalaya, southern Qiangtang, and Tibet. This spatial and temporal correlation implies that these alkaline rocks formed within a large-scale extension regime across the Tethys realm. This early Permian magmatic event was likely triggered by a mantle plume, which played an active role during rifting along the northern margin of Gondwana.

Studies worldwide, particularly in Canada, Italy and Brazil, have demonstrated that the Sr-87/Sr-86 ratio is a reliable indicator of the geographic origin of wines. We present here the first Sr-87/Sr-86 isotope study for the Wines of Altitude of Santa Catarina geographical indication that was recently created in the state of Santa Catarina, southern Brazil. The goal of this study is to evaluate the forensic application of strontium isotope ratios as an indicator of provenance for the wines of S & atilde;o Joaquim, the main wine-growing region in the state of Santa Catarina, which produces wines from European grape varieties (Vitis vinifera L.) grown in soils formed by the weathering of volcanic rocks of the Serra Geral Group (Paran & aacute; Magmatic Province). The Sr-87/Sr-86 of rocks, soils (bulk and labile fractions), vines (leaves and grapes) and wines (Sauvignon Blanc and Cabernet Sauvignon) from three wineries from S & atilde;o Joaquim were determined. Bedrock Sr-87/Sr-86 ratios ranged from 0.705362 for the basaltic-andesitic rocks to 0.724819 for dacites, consistent with reported values for these types of rocks. We identified a strong correlation between the Sr-87/Sr-86 ratios of the grapes and leaves, but in contrast to most previous studies there was no correlation between those of the soil (both bulk and labile fractions) and wine samples. This indicates that although the Sr isotopes in grapes and leaves behaved conservatively, the Sr isotopes in the soils may have been modified by vineyard agricultural practices, such as fertilization and liming. We thus recommend that soil sampling be done at depths >60 cm to avoid external addition of strontium. As the Sr-87/Sr-86 ratios of commercial wines represent the average isotope ratio of a given vineyard, the isotope correlation between wines and the other samples may be challenging. Despite that, it was possible to distinguish the Sr-87/Sr-86 ratios of the wines from S & atilde;o Joaquim, state of Santa Catarina, from the wines from Bento Gon & ccedil;alves, state of Rio Grande do Sul. Even though the wines from both regions are made from grapes cultivated in the same geological unit, i.e., volcanic rocks from Serra Geral Group (Paran & aacute; Magmatic Province), the wines yield different Sr signatures.

Delhi, the capital city of India, experiences severe air pollution and suffers from its adverse effects on human health and ecosystems. This pollution is characterized by high levels of pollutants, including atmospheric nitrogen in both the gaseous and particulate phases. However, there is a lack of simultaneous measurement of chemical composition, tracers and N-15 data in aerosols to understand the influence of different sources on N aerosols over Delhi. Here, we measured total nitrogen (TN), water-soluble total nitrogen (WSTN), water-soluble inorganic nitrogen (WSIN), and N stable isotope compositions (delta N-15) in PM2.5 samples covering the postmonsoon, winter, and summer periods of the year 2018-19. NH4+-N was the major N species, accounting for an average 58% of TN and 68% of WSIN. The temporal variations of TN, WSTN, NH4+-N, NO3--N, and WSON showed peaks in the post-monsoon and winter seasons, exhibiting seasonality similar to PM2.5 and levoglucosan (a biomass-burning tracer) indicating their co-genetic sources. Based on the correlation analysis between delta N-15 and N-species, we identified two distinct secondary chemical processes: i) in an NH4+-poor atmosphere, the gasto-particle (NH3 -> NH4+) conversion and subsequent formation of NH4HSO4 was the main process controlling the delta N-15 and nitrogen enrichments in PM2.5; whereas ii) under NH4+-rich conditions, the formation and dissociation of NH4NO3 dominated. The coupled HYSPLIT and PSCF analyses highlighted the transport and contributions of open biomass burning emissions under a northwesterly atmospheric flow during post-monsoon as well as from local biomass combustion (from cooking and heating) during winter in the city and its vicinity. Our results suggested that i) both NH4+-N and NO3--N were mainly impacted by biomass combustion during post-monsoon and winter seasons, and ii) NO3--N resulted of dust transport from the Thar Desert in the summer season, but not NH4+-N. Finally, we recommend that future research focuses on the study of the seasonality of atmospheric nitrogen composition using N-15 data from their different sources to design tailor-made measures and policies regarding the different potential sources, combining them within a comprehensive framework to ultimately improve air quality and the living environment in Delhi.

We characterized the elemental and C and N stable isotope compositions of Tillandsia fasciculata Sw., Tillandsia balbisiana Schult. & Schult.f. and Tillandsia recurvata (L.) L. samples collected in Cienfuegos (Cuba). Results showed high enrichment factors for S, Hg, Cd, Pb, P, Zn, Cu, Mo, Sb and Ca in all Tillandsia species, indicating inputs from local anthropogenic activities (road traffic, industries and cement production). Carbon concentrations and delta C-13 varied from 38.3-47.7 % and -20.4 to -13.4 parts per thousand within the three species, respectively. delta C-13 showed seasonal dependence with the dry and wet periods and more C-13-depleted values in urban/industrial areas, coherent with the input of anthropogenic emissions. Nitrogen concentrations (0.4-1.3 %) and delta N-15 values (-9.9-4.4 parts per thousand ) exhibit larger variations and are positively correlated in the three species. The most positive delta N-15 in T. recurvata (-0.2-4.4 parts per thousand ) are attributed to contributions from industrial activities and road traffic. In fact, both delta N-15 and total nitrogen (TN) values increase in sites with higher road traffic and show significant correlations with typical road traffic and industrial tracers. Finally, we calculate an average total nitrogen deposition rate of 4.4 +/- 2.3 kg ha(-1) a(-1) from N content in T. recurvata, similar to the existing values determined in the region by field measurements, but higher than the global terrestrial average.

Landfill operations and waste processing facilities are important and highly heterogeneous sources of both greenhouse gases (GHGs) and non-GHG air pollutants in the atmosphere. This arises the need for detailed apportionment of waste sources in order to locate and subsequently reduce emissions from landfills. Here, a time series of in situ measurements of atmospheric trace gases and spatial allocation of specific emission source types under different processing phases and environmental conditions were conducted in and in the surroundings of a Municipal Solid Waste Treatment Plant (MSWTP) in south-western Poland. Results revealed that several individual GHG sources dominated across the waste processing facility and that GHGs concentrations displayed spatial seasonality. An increase in the ground-level CH4 concentrations, from similar to 30.3 to 56.3 ppmv, was observed close (similar to 5 - 10 m) to the major emission sources within the MSWTP. While hotspot areas generally yielded elevated CH4 concentrations near the soil surface, these were relatively low (2.4 to 8.9 ppmv) along the facility's fence line. The study of the corresponding delta C-13 delineated the extent of dispersion plumes downwind emission hotspots, characterized by a C-13 depletion (around 4.0 parts per thousand) in the atmospheric CH4 and CO2. For CH4, emissions were isotopically discriminated between the extraction wells at active quarters/cells (delta C-13 = -58.3 +/- 1.1 parts per thousand) and biogas produced in the biological waste treatment installation (delta C-13 = -62.7 +/- 0.7 parts per thousand). Most of the trace compounds (non-methane hydrocarbons, halocarbons, oxygen-bearing organic gases, ketones, nitrogenous and sulphurous gases, and other admixture compounds) detected at the ground surface were linked to the CH4- and CO2-rich spots. Despite the relatively high variability in the concentrations of organic and inorganic compounds observed at the MSWTP active zones, our results suggest that they do not have a meaningful impact on the surrounding air quality.

The chemistry of atmospheric precipitation serves as an important proxy for discriminating the source(s) of air contaminants in urban environments as well as to discuss the dynamic of atmospheric chemistry exchanges. This approach can be undertaken at time scales varying from single events to seasonal and yearly time frames. Here, we characterized the chemical composition of two single rain episodes (18 July 2018 and 21 February 2019) collected in Wrocław (SW Poland). Our results demonstrated inner variations and seasonality (within the rain event as well as between summer and winter), both in ion concentrations as well as in their potential relations with local air contaminants and scavenging processes. Coupling statistical analysis of chemical parameters with meteorological/synoptic conditions and HYSPLIT back trajectories allowed us to identify three main factors (i.e., principal components; PC) controlling the chemical composition of precipitation, and that these fluctuated during each event: (i) PC1 (40%) was interpreted as reflecting the long-range transport and/or anthropogenic influences of emission sources that included biomass burning, fossil fuel combustion, industrial processes, and inputs of crustal origin; (ii) PC2 (20%) represents the dissolution of atmospheric CO2 and HF into ionic forms; and (iii) PC3 (20%) originates from agricultural activities and/or biomass burning. Time variations during the rain events showed that each factor was more important at the start of the event. The study of both SO42− and Ca2+ concentrations showed that while sea spray inputs fluctuated during both rain events, their overall impact was relatively low. Finally, below-cloud particle scavenging processes were only observed for PM10 at the start of the winter rain episode, which was probably explained by the corresponding low rain intensity and an overlap from local aerosol emissions. Our study demonstrates the importance of multi-time scale approaches to explain the chemical variability in rainwater and both its relation to emission sources and the atmosphere operating processes.

This study presents the mineralogy and strontium isotope ratio (87Sr/86Sr) of 21 pathological biominerals (bladder and kidney stones) collected from patients admitted between 2018 and 2020 at the Department of Urology of the San Pio Hospital (Benevento, southern Italy). Urinary stones belong to the calcium oxalate, purine or calcium phosphate mineralogy types. Their corresponding 87Sr/86Sr range from 0.707607 for an uricite sample to 0.709970 for a weddellite one, and seem to be partly discriminated based on the mineralogy. The comparison with the isotope characteristics of 38 representative Italian bottled and tap drinking waters show a general overlap in 87Sr/86Sr with the biominerals. However, on a smaller geographic area (Campania Region), we observe small 87Sr/86Sr differences between the biominerals and local waters. This may be explained by external Sr inputs for example from agriculture practices, inhaled aerosols (i.e., particulate matter), animal manure and sewage, non -regional foods. Nevertheless, biominerals of patients that stated to drink and eat local water/wines and foods every day exhibited a narrower 87Sr/86Sr range roughly matching the typical isotope ratios of local geological materials and waters, as well as those of archaeological biominerals from the same area. Finally, we conclude that the strontium isotope signature of urinary stones may reflect that of the environmental matrices surrounding patients, but future investigations are recommended to ultimately establish the potential for pathological biominerals as reliable biomonitoring proxies, taking into the account the contribution of the external sources of Sr.

Populations are constantly exposed to airborne metals, in particular in urban areas. Despite their proven links to health issues, their origin and fate are still subject to debate. Bioindicators, by taking up and cumulating atmospheric metals over time, have been widely used to proxy environmental quality over large areas, at various time scales. Using the example of the Paris region, we investigated the potential for the Grimmia pulvinata moss species to both characterize air metal contamination and to identify its main sources. To this end, we coupled metal/metalloid (Al, As, Cd, Cr, Cu, Fe, Ni, Pb, Sb, Sr, V and Zn) concentrations and Pb isotope ratios from samples collected in cemeteries in the city and its suburbs. Metal enrichment factors ranged between 2 and 10 for As, Cr, Fe, Ni, Sr, V, between 50 and 100 for Cu, Pb and Zn and > 100 for Cd and Sb, indicating a dominant anthropogenic origin. Principal component analysis showed that 3 principal components explained 89

The emissions of sulfur dioxide (SO2), a harmful atmospheric pollutant, are on the rise in South Asia. Sulfate, formed from the oxidation of SO2, often comprises 10%–67% of aerosol mass and has a profound impact on climate, air quality/human health, and the environment. The potential drivers of sulfate-linked urban air pollution in South Asian megacities─facing a choking air pollution crisis─remain poorly understood due to a lack of systematic observations. Here, we conducted stable S-isotope (δ34S) fingerprinting of sulfate aerosols in summertime megacity Delhi in South Asia to evaluate the potential drivers. With newly developed region-specific isotopic endmembers in this study, a statistical source apportionment of urban atmospheric sulfate was feasible. Results show that coal combustion (80 ± 12%) and oil combustion (14 ± 11%), followed by road dust (4 ± 3%) and biomass burning (2 ± 2%), were major contributors to atmospheric sulfate in summertime Delhi. Retrospective analysis showed a marked isotopic shift in stable sulfate isotopic composition in summertime megacity Delhi wherein the average δ34S value was 4 ± 1‰ in 2015 and 2 ± 1‰ in 2021, respectively. This was evidently linked to changes in the dominant fuel type as sulfate sourced from coal combustion (oil combustion) significantly increased ∼ 20% (decreased ∼ 20%) during this period. With no clear increase in the number of thermal power plants in and around Delhi, we speculate that the substantial increase in coal-derived sulfate could plausibly be linked to a rise in the informal industries such as brick production and food and agricultural product processing operations, whose SO2 emissions remain challenging to estimate. While further observations from the region are warranted, the findings here suggest that the continued dependence on coal in developing nations of South Asia could be one of the reasons for rising SO2 levels.

Himalayas and Tibetan Plateau (HTP) is important for global biodiversity and regional sustainable development. While numerous studies have revealed that the ecosystem in this unique and pristine region is changing, their exact causes are still poorly understood. Here, we present a year-round (23 March 2017 to 19 March 2018) ground- and satellite-based atmospheric observation at the Qomolangma monitoring station (QOMS, 4276 m a.s.l.). Based on a comprehensive chemical and stable isotope (15N) analysis of nitrogen compounds and satellite observations, we provide unequivocal evidence that wildfire emissions in South Asia can come across the Himalayas and threaten the HTP's ecosystem. Such wildfire episodes, mostly occurring in spring (March-April), not only substantially enhanced the aerosol nitrogen concentration but also altered its composition (i.e., rendering it more bioavailable). We estimated a nitrogen deposition flux at QOMS of ∼10 kg N ha-1 yr-1, which is approximately twice the lower value of the critical load range reported for the Alpine ecosystem. Such adverse impact is particularly concerning, given the anticipated increase of wildfire activities in the future under climate change.