Occurrence, distribution, potential sources, and risks of organophosphate esters in fresh snow on Urumqi Glacier No. 1, eastern Tien Shan, China.

Organophosphate esters (OPEs), extensively used as flame retardants, are widely detected in various regions and environments. The potential toxicity of OPEs has caused great concern in recent years. Based on the global distillation model, the Tien Shan glaciers, such as Urumqi Glacier No. 1, could be as a potential "sink" for OPEs. However, little is known about the concentration, distribution, potential sources, and ecological risks of OPEs in Tien Shan glaciers. In this study, fresh snow samples were collected at various altitudes on the Urumqi Glacier No. 1, eastern Tien Shan, China. The total concentrations of ten OPEs (Σ10OPEs) ranged from 116 to 152 ng/L. The most abundant OPE was tris-(2-chloroisopropyl) phosphate (TCIPP), contributing to 74 % of the total OPEs. Σ10OPEs, tri-n-butyl phosphate (TnBP), and TCIPP concentrations showed positive correlations with altitude, indicating the effect of cold condensation on OPEs deposition. Based on air mass back-trajectory analysis and principal component analysis, we found that emissions from both traffic and household products in indoor environment were the important sources, and OPEs on the Urumqi Glacier No. 1 might mainly originate from Europe. Our assessment also showed triphenyl phosphate (TPhP) posed a low ecological risk in snow. This is the first systematic study of OPEs on the Tien Shan glaciers.

Abrupt climate fluctuations in Tibet as imprints of multiple meltwater events during the early to mid-Holocene.

Understanding the impact of meltwater discharge during the final stage of the Laurentide Ice Sheet (LIS) has important implications for predicting sea level rise and climate change. Here we present a high-resolution ice-core isotopic record from the central Tibetan Plateau (TP), where the climate is sensitive to the meltwater forcing, and explore possible signals of the climate response to potential LIS meltwater discharges in the early to mid-Holocene. The record shows four abrupt large fluctuations during the 7-9 ka BP (kiloannum before present), reflecting large shifts of the mid-latitude westerlies and the Indian summer monsoon (ISM) over this period, and they corresponded to possible LIS freshwater events documented in other paleoclimate records. Our study suggests that multiple rapid meltwater discharge events might have occurred during the final stage of LIS. The finding implies the possibility of rapid sea level rise and unstable climate in the transition zone between the mid-latitude westerlies and the ISM due to fast polar ice retreat under the anthropogenic global warming.

Middle east warming in spring enhances summer rainfall over Pakistan.

The edge of a monsoon region is usually highly sensitive to climate change. Pakistan, which is located on the northern edge of the Indian monsoon, is highly vulnerable to heavy rainfall and has witnessed several debilitating floods exacerbated by global warming in recent years. However, the mechanisms for the frequent Pakistan floods are yet not fully understood. Here, we show that the Middle East is undergoing an increase in land heating during spring, which is responsible for 46% of the intensified rainfall over Pakistan and northwestern India during 1979-2022. This springtime land warming causes a decline in sea level pressure (SLP), which strengthens the meridional SLP gradient between the Middle East and the southern Arabian Sea and drives the changes of low-level jet (LLJ) subsequently. The impact persists into summer and results in a northward shift of the monsoonal LLJ, accompanied by strong positive vorticity in the atmosphere and enhanced moisture supply to Pakistan. Consequently, the transition region between the summer monsoon in South Asia and the desert climate in West Asia is shifted northwestward, posing significantly enhanced risk of floods over Pakistan and northwestern India.

The first detection of organophosphate esters (OPEs) of a high altitude fresh snowfall in the northeastern Tibetan Plateau.

Due to the gradual phase-out of brominated flame retardants, the consumption of organophosphate esters (OPEs) as suitable alternatives has increased in recent years. These compounds could be trapped and accumulate in the widely developed glaciers such as Laohugou Glacier No. 12 in the Tibetan Plateau (TP), as snow is an effective scavenger of organic pollutants in the atmosphere. However, large gaps in knowledge still exist regarding the occurrence, distribution, and source analysis of OPEs in TP glaciers. In this study, eight surface snow samples collected at different altitudes on Laohugou Glacier No. 12 on the northeastern edge of the TP in order to investigate sources and distribution of OPEs. The results showed that the concentrations of ∑7OPEs varied from 54.53 ng/L to 169.15 ng/L, with a mean of 99.84 ng/L. ∑Chlorinated-OPEs (Cl-OPEs) were dominant in these samples, accounting for 83% of the total OPE concentrations. ∑OPEs concentration increases with altitude on Laohugou Glacier No. 12, implying an altitudinal magnification effect on OPEs deposition. Principal component analysis suggests that OPEs primarily originated from traffic emissions and their variations were largely driven by dust transport. Analyses of backward trajectories of air masses and the wind field indicate that these OPEs might have come from urban emissions northwest of Laohugou Glacier No. 12. This study provides the first valuable insight into the environmental behavior of OPEs in Tibetan glaciers.

Temporal variations of the contribution of combustion-derived water vapor to urban humidity during winter in Xi'an, China.

Combustion-derived water vapor (CDV) has significant impacts on urban climate and environment. However, temporal variations of contribution of CDV (CCDV) to urban humidity are unclear due to lack of observations. This study examined the temporal variations of CCDV in Xi'an during winter from 2016 to 2019. We found that the diurnal variation of CCDV is mainly controlled by atmospheric stability, but the peak of CCDV at 9 am is due to the increasing water vapor emission by motor vehicles during the morning rush hour. In addition, the monthly variation of CCDV is related to fossil fuel consumption, but the low values of CCDV in late January and early February is due to substantial decrease of energy utility because of the massive outflow of population during the Spring Festival. Our findings may be helpful for urban pollution control because CDV can play an important role in the secondary conversion of pollutants.

Ice-core based assessment of nitrogen deposition in the central Tibetan Plateau over the last millennium.

Atmospheric nitrogen deposition is a unique source of bioavailable nitrogen for ecosystems in remote regions, and has vital impacts on ecological processes. Understanding variations of atmospheric nitrogen deposition in these regions remains challenging due to a lack of observations. Ice cores contain records of nitrogen species of nitrate (NO3-) and ammonium (NH4+), hence provide valuable long-term data to study past variations of atmospheric nitrogen deposition. In this study, we present an annually resolved record of NH4+ and NO3- over the past millennium, derived from the Zangser Kangri (ZK) ice core in the central Tibetan Plateau. The concentration peaks of NH4+ and NO3- coincide with those of Ca2+ (a dust tracer), indicating that variation of nitrogen species in the ZK ice core is largely driven by dust activities. An EOF analysis for all chemical species (Cl-, SO42-, NO3-, Na+, NH4+, K+, Mg2+, Ca2+) reveals significant but separate loadings of NH4+ and NO3- on EOF 2, suggesting an additional source of nitrogen, likely from biogenic emissions of terrestrial ecosystems. Over the past millennium, the EOF 2 series has relatively high values around 1300 CE and 1600 CE, and has increased significantly since the Industrial Revolution. These variations are likely driven by temperature-dependent biogenic emissions on the Tibetan Plateau. Analyses of seasonal air mass backward trajectories and wind fields find that the chemical concentrations in the ZK ice core are mostly influenced by the westerly, but South Asia summer monsoon plays an important role in the transport of nitrogen species generated from biogenic emissions. This is further confirmed by the significant correlation between EOF 2 series and the South Asian summer monsoon index. This study provides new insight into the preindustrial sources, natural variabilities and major drivers of nitrogen deposition on the Tibetan Plateau.

Assessment of heavy metal contamination in the atmospheric deposition during 1950-2016 A.D. from a snow pit at Dome A, East Antarctica.

Antarctic trace element records could provide important insights into the impact of human activities on the environment over the past few centuries. In this study, we investigated the atmospheric concentrations of 14 representative heavy metals (Al, As, Cd, Co, Cu, Fe, K, Mg, Mn, Pb, Sb, Sr, Tl and V) from 174 samples collected in a 4-m snow pit at Dome Argus (Dome A) on the East Antarctic Plateau, covering the period from 1950 to 2016 A.D. We found great variability in the annual concentration of all metals. The crustal enrichment factors suggest that the concentrations of some heavy metals (Cd, Sb, Cu, As and Pb) were likely influenced by anthropogenic activities in recent decades. An analysis of source regions suggests that heavy metal pollution at Dome A was largely caused by human activities in Australia and South America (e.g. mining production, leaded gasoline). Based on the relationship between the trace elements fluxes and sea ice concentration (SIC), sea surface temperature (SST) and annual mean air temperature at 2 m above the ground (T2m), our analysis shows that deposition and transport of atmospheric aerosol at Dome A were influenced by circum-Antarctic atmospheric circulations.

An increase of ammonia emissions from terrestrial ecosystems on the Tibetan Plateau since 1980 deduced from ice core record.

Ammonia (NH3) emissions could have significant impacts on both ecosystems and human health. Ice cores from the Tibetan Plateau contain information about past ammonium (NH4+) deposition, which could yield important insights into historical NH3 emissions in the surrounding source regions as well as long-distance NH4+ aerosol transport via atmospheric circulation. In this paper, we present a high-resolution atmospheric NH4+ deposition record for the period, 1951-2008, reconstructed from the Zangser Kangri (ZK) ice core in the northern Tibetan Plateau. An empirical orthogonal function (EOF) analysis of major soluble ions (NH4+, NO3-, SO42-, Cl-, Na+, K+, Mg2+ and Ca2+) reveals that EOF 1 has significant loadings of all ions, therefore representing common transport pathways, while EOF 2 is only significantly loaded by NH4+ (0.86) and NO3- (0.35), suggesting a unique signal possibly representing emissions from the surrounding terrestrial ecosystems on the Tibetan Plateau. Backward trajectory analysis indicates that the air masses over the ZK ice core drilling site primarily come from the northwestern Indian Peninsula. NH3 emissions from agricultural activities in this area likely contribute to the NH4+ deposition of the ZK ice core via the Indian monsoon. Correlations between EOF 2 time series and temperature, normalized difference vegetation index (NDVI) suggest that increasing temperature and vegetation after 1980 likely promoted NH3 emissions from terrestrial ecosystems. Our results provide a reliable and valuable assessment of NH4+ deposition from human activities and terrestrial ecosystems in the ZK ice core, and help in understanding air pollution over the past few decades in the northern Tibetan Plateau.

Uranium record from a 3 m snow pit at Dome Argus, East Antarctica.

Understanding the distribution and transport of Uranium is important because it can lead to both chemical and radiological toxicity. This study presents the Uranium concentrations time series from 1964 to 2009 obtained from a 3 m deep snow pit at Dome Argus, East Antarctic Plateau. The data shows that Uranium concentrations vary from 0.0067 pg g-1 to 0.12 pg g-1, with a mean concentration of 0.044 pg g-1. Its mean concentration is 2-3 folds lower than at West Antarctica study sites, such as the Antarctic Peninsula (mean 0.12 pg g-1), IC-6 (Ice Core-6) (mean 0.11 pg g-1) and a suite of ice cores from the US ITASE traverse. Before the mid-1980s, the varieties of Uranium concentrations are relatively stable, with a very low mean concentration of 0.016 pg g-1and its main source is sea salt deposition, while a small number of anthropogenic sources are likely to be caused by Uranium mining operations in South Africa. A remarkable increase of Uranium concentrations has occurred since the mid-1980s (by a factor of ~ 9) compared with the amount before the mid-1980s. This increase coincides with the Uranium records at IC-6 and Antarctic Peninsula (DP-07-01) during the same period, and are mostly attributed to Uranium mining operations in Australia as a potential primary anthropogenic Uranium source. Our observations suggest that Uranium pollution in the atmosphere might have already become a global phenomenon.

Distribution of ARGs and MGEs among glacial soil, permafrost, and sediment using metagenomic analysis.

Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) can be identified with metagenomic analyses comparing relatively pristine and human-impacted environments. We collected samples from 3 different environments: glacial soil little affected by anthropogenic activity, deep permafrost dated to 5821 BP (before human antibiotics), and sediment from the Pearl River. Sulfonamides, tetracyclines, and fluoroquinolones were common in the sediment samples. Sulfonamides and tetracycline were not found in permafrost; tetracycline was also not found in glacial soil. ARGs from the sediment were more abundant and diverse than those from glacial soil and permafrost. More types of resistance mechanisms were also present in the sediment. The diversity of MGEs was significantly correlated with the abundance and diversity of ARGs. The result will help future workers to better understand the distribution of ARGs among environments more or less impacted by anthropogenic activities.

Corrigendum: Possible recent warming hiatus on the northwestern Tibetan Plateau derived from ice core records.

This corrects the article DOI: 10.1038/srep32813.

Persistent Pb Pollution in Central East Antarctic Snow: A Retrospective Assessment of Sources and Control Policy Implications.

Well-defined variations in the enrichments and isotopic compositions of Pb have been observed in snow from Dome Fuji and Dome A in the central East Antarctic Plateau (EAP) over the past few decades. The Pb isotopic fingerprints indicate that the rapid increase in Pb enrichments from the mid-1970s, reaching a peak in ∼1980, is due to the massive use of leaded gasoline in northern South America, especially Brazil. Since then, they show a continuous decline, mostly due to the significant removal of the Pb additives from gasoline in Brazil in the 1980s and, subsequently, in Argentina and Chile in the 1990s. After the phase-out of Pb in gasoline, Cu smelting in Chile has become the major source of Pb, contributing ∼90% to the total Pb emissions in northern South America in 2005. Nevertheless, Pb pollution in the central EAP declined substantially until recently as a result of the regulatory efforts to curb toxic trace metal emissions from the Cu industry in Chile. However, more than 90% of the Pb in the most remote places on Earth are still of anthropogenic origin, highlighting the need for the continuation of environmental regulations for the further reduction of Pb emissions.

Possible recent warming hiatus on the northwestern Tibetan Plateau derived from ice core records.

Many studies have reported enhanced warming trend on the Tibetan Plateau (TP), even during the warming hiatus period. However, most of these studies are based on instrumental data largely collected from the eastern TP, whereas the temperature trend over the extensive northwestern TP remains uncertain due to few meteorological stations. Here we combined the stable isotopic δ(18)O record of an ice core recovered in 2012 from the Chongce glacier with the δ(18)O records of two other ice cores (i.e., Muztagata and Zangser Kangri) in the same region to establish a regional temperature series for the northwestern TP. The reconstruction shows a significant warming trend with a rate of 0.74 ± 0.12 °C/decade for the period 1970-2000, but a decreasing trend from 2001 to 2012. This is consistent with the reduction of warming rates during the recent decade observed at the only two meteorological stations on the northwestern TP, even though most stations on the eastern TP have shown persistent warming during the same period. Our results suggest a possible recent warming hiatus on the northwestern TP. This could have contributed to the relatively stable status of glaciers in this region.

[Difference of community structure among culturable bacteria in different glacial samples on Chongce Ice Cap].

Objective: We studied the difference of bacterial community composition among glacial snow, moraine deposits and glacial soil on Chongce Ice Cap of West Kunlun Mountains. Methods: Based on traditional culturedependent and 16S rRNA sequence analysis, we analyzed the community structure of bacteria on the level of genus and phylum. Results: Results show that glacial bacteria were composed of Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes on the phylum level. Glacial snow was dominated by Proteobacteria, whereas glacial soil and moraine deposits were dominated by Actinobacteria. On the genus level, glacial soil was dominated by Arthrobacter, while glacial snow was dominated by Methylobacterium, Modestobacter, Hymenobacter, Brevundimonas and Bacillus. Bacterial composition was similar between glacial soil and moraine deposits, but different from glacial snow. Skermanella may be unique on Chongce Ice Cap. Conclusion: Our study indicated the vulnerability of bacterial diversity in glacial snow with glacial retreat, and the importance of bacterial resources preservation on glacial snow environments.

Seasonal variations in the sources of natural and anthropogenic lead deposited at the East Rongbuk Glacier in the high-altitude Himalayas.

Lead (Pb) isotopic compositions and concentrations, and barium (Ba) and indium (In) concentrations have been analysed at sub-annual resolution in three sections from a <110 m ice core dated to the 18th and 20th centuries, as well as snow pit samples dated to 2004/2005, recovered from the East Rongbuk Glacier in the high-altitude Himalayas. Ice core sections indicate that atmospheric chemistry prior to ~1,953 was controlled by mineral dust inputs, with no discernible volcanic or anthropogenic contributions. Eighteenth century monsoon ice core chemistry is indicative of dominant contributions from local Himalayan sources; non-monsoon ice core chemistry is linked to contributions from local (Himalayan), regional (Indian/Thar Desert) and long-range (North Africa, Central Asia) sources. Twentieth century monsoon and non-monsoon ice core data demonstrate similar seasonal sources of mineral dust, however with a transition to less-radiogenic isotopic signatures that suggests local and regional climate/environmental change. The snow pit record demonstrates natural and anthropogenic contributions during both seasons, with increased anthropogenic influence during non-monsoon times. Monsoon anthropogenic inputs are most likely sourced to South/South-East Asia and/or India, whereas non-monsoon anthropogenic inputs are most likely sourced to India and Central Asia.

Culturable bacteria isolated from snow cores along the 1300 km traverse from Zhongshan Station to Dome A, East Antarctica.

The abundance and community composition of culturable bacteria in four snow cores along the 1300 km traverse from Zhongshan Station to Dome A, East Antarctica, were investigated through the combination of liquid and solid media and small subunit 16S rRNA sequences. Under aerobic cultivation conditions, the average concentrations of bacterial colonies from each snow core varied from 0.008 to 0.32 CFU mL(-1). A total of 37 and 15 isolates with different morphologic characteristics were recovered from solid and liquid media PYGV, respectively. The phylogenetic analysis of 14 representatives with different ARDRA patterns from RFLP showed that all the isolates were affiliated with five phylogenetic groups: Firmicutes, Actinobacteria, Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes. Actinobacteria represented the largest cluster with 43% of strains, and these strains exhibited unique phenotypic properties. The community compositions of culturable bacteria in the four snow cores were distinctly different from each other and the concentrations and community sizes of culturable bacteria along the traverse decreased with increases of latitude, altitude and distance from coast, which likely reflected the different bacterial sources and biogeographies under the different regional climate conditions in the snow cover of East Antarctica.

Isotopic signatures for natural versus anthropogenic Pb in high-altitude Mt. Everest ice cores during the past 800 years.

A long-term record, extending back 800 years (1205 to 2002 AD), of the Pb isotopic composition ((206)Pb/(207)Pb and (208)Pb/(207)Pb) as well as Pb concentrations from high altitude Mt. Everest ice cores has the potential to identify sources and source regions affecting natural and anthropogenic Pb deposition in central Asia. The results show that the regional natural background Pb isotope signature (~1.20 for (206)Pb/(207)Pb and ~2.50 for (208)Pb/(207)Pb) in the central Himalayas was dominated by mineral dust over the last ~750 years from 1205 to 1960s, mostly originating from local sources with occasional contributions of long-range transported dust probably from Sahara desert and northwestern India. Since the 1970s, the Pb isotope ratios are characterized by a continuous decline toward less radiogenic ratios with the least mean ratios of 1.178 for (206)Pb/(207)Pb and 2.471 for (208)Pb/(207)Pb in the period 1990-1996. The depression of the (206)Pb/(207)Pb and (208)Pb/(207)Pb values during the corresponding periods is most likely due to an increasing influence of less radiogenic Pb of anthropogenic origin mainly from leaded gasoline used in South Asia (India as well as possibly Bangladesh and Nepal). From 1997 to 2002, isotopic composition tends to show a shift to slightly more radiogenic signature. This is likely attributed to reducing Pb emissions from leaded gasoline in source regions, coinciding with the nationwide reduction of Pb in gasoline and subsequent phase-out of leaded gasoline in South Asia since 1997. An interesting feature is the relatively high levels of Pb concentrations and enrichment factors (EF) between 1997 and 2002. Although the reason for this feature remains uncertain, it would be probably linked with an increasing influence of anthropogenic Pb emitted from other sources such as fossil fuel combustion and non-ferrous metal production.

Abundance and community of snow bacteria from three glaciers in the Tibetan Plateau.

Bacterial abundance and diversity in snow of East Rongbuk, Laohugou and Hailuogou glaciers on the Tibetan Plateau were investigated through epifluorescence microscope and denaturing gradient gel electrophoresis. Cell abundance ranged from 4.0 x 10(3) to 290.2 x 10(3) cells/mL. The phylogenetic trees placed the 16S rRNA sequences in four major groups: Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Brevundimonas, Flavobacterium, Hymenobacter, Bacillus, Polaromonas, Rhodoferax and Streptomyces were widely distributed bacteria in glaciers from different cold regions. The remaining five genera of Hylemonella, Delftia, Zoogloea, Blastococcus and Rhodococcus were endemism, only recovered from our investigated glaciers. It is proposed that the three glaciers on the Tibetan Plateau provide a specific ecological niche for prolonging survival of diverse microbial lineages.

An 800-year record of atmospheric As, Mo, Sn, and Sb in central Asia in high-altitude ice cores from Mt. Qomolangma (Everest), Himalayas.

As, Mo, Sn, and Sb have been determined by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) in 143 depth intervals of high-altitude ice cores from Mt. Everest, covering an 800-year time period from 1205 to 2002 AD. The results clearly demonstrate the long-term historical record of atmospheric transport and deposition of As, Mo, Sn, and Sb that has prevailed at high altitudes in the central Himalayas. Natural contributions, mainly from mineral dust, have dominated the atmospheric cycles of As, Mo, Sn, and to some extent Sb during the 700 years prior to the 20th century. Compared to those of the pre-1900 period, pronounced increases of both concentrations and crustal enrichment factors are observed since the 1970s, with the highest increase factor for Sn and the lowest for As. Such increases are attributed to anthropogenic emissions of these elements, largely from stationary fossil fuel combustion and nonferrous metals production, particularly in India. Our central Himalayan ice core record provides an explicit recognition of rising atmospheric As, Mo, Sn, and Sb pollution in response to rapid economic growth in central Asia.