Plateau Sites Research Articles

A Labeling Intercomparison of Retrogressive Thaw Slumps by a Diverse Group of Domain Experts

ABSTRACTDeep‐learning (DL) models have become increasingly beneficial for the detection of retrogressive thaw slumps (RTS) in the permafrost domain. However, comparing accuracy metrics is challenging due to unstandardized labeling guidelines. To address this, we conducted an experiment with 12 international domain experts from a broad range of scientific backgrounds. Using 3 m PlanetScope multispectral imagery, they digitized RTS footprints in two sites. We evaluated label uncertainty by comparing manually outlined RTS labels using Intersection‐over‐Union (IoU) and F1 metrics. At the Canadian Peel Plateau site, we see good agreement, particularly in the active parts of RTS. Differences were observed in the interpretation of the debris tongue and the stable vegetated sections of RTS. At the Russian Bykovsky site, we observed a larger mismatch. Here, the same differences were documented, but several participants mistakenly identified non‐RTS features. This emphasizes the importance of site‐specific knowledge for reliable label creation. The experiment highlights the need for standardized labeling procedures and definition of their scientific purpose. The most similar expert labels outperformed the accuracy metrics reported in the literature, highlighting human labeling capabilities with proper training, site knowledge, and clear guidelines. These findings lay the groundwork for DL‐based RTS monitoring in the pan‐Arctic.

Aridity shapes distinct biogeographic and assembly patterns of forest soil bacterial and fungal communities at the regional scale

Climate change is exacerbating drought in arid and semi-arid forest ecosystems worldwide. Soil microorganisms play a key role in supporting forest ecosystem services, yet their response to changes in aridity remains poorly understood. We present results from a study of 84 forests at four south-to-north Loess Plateau sites to assess how increases in aridity level (1- precipitation/evapotranspiration) shapes soil bacterial and fungal diversity and community stability by influencing community assembly. We showed that soil bacterial diversity underwent a significant downward trend at aridity levels >0.39, while fungal diversity decreased significantly at aridity levels >0.62. In addition, the relative abundance of Actinobacteria and Ascomycota increased with higher aridity level, while the relative abundance of Acidobacteria and Basidiomycota showed the opposite trend. Bacterial communities also exhibited higher similarity-distance decay rates across geographic and environmental gradients than did fungal communities. Phylogenetic bin-based community assembly analysis revealed homogeneous selection and dispersal limitation as the two dominant processes in bacterial and fungal assembly. Dispersal limitation of bacterial communities monotonically increased with aridity levels, whereas homogeneous selection of fungal communities monotonically decreased. Importantly, aridity also increased the sensitivity of microbial communities to environmental disturbance and potentially decreased community stability, as evidenced by greater community similarity-environmental distance decay rates, narrower habitat niche breadth, and lower microbial network stability. Our study provides new insights into soil microbial drought response, with implications on the sustainability of ecosystems under environmental stress.

Karst landforms as microrefugia for soil Collembola: Open versus forested dolines

Enclosed surficial karst dolines are geomorphologically diverse habitats with the potential to strongly shape community structure and the distribution of functional groups of organisms. Forest habitats in karst landscapes are characterized by lower soil temperatures and microclimatic fluctuations compared to open habitats; therefore, they may provide favorable conditions for cold-adapted/psychrophilic species, which are highly vulnerable to climate warming. We compared the diversity and structure of soil Collembola communities at sites along microclimatic gradients in open and forested karst dolines. The effect of topography and related environmental conditions on the distribution of ecological groups of soil Collembola was analyzed, and the function of the dolines as potential climate refugia for psychrophilic arthropods was assessed. The karst dolines revealed significant habitat heterogeneity, including warm plateaus and S-facing slopes and colder and wetter bottoms and N-facing slopes. The inner sites of the dolines had an overall higher abundance and species richness compared to the plateau sites. Nonmetric multidimensional scaling ordination revealed a clear delimitation of Collembola communities in terms of warmer and cooler sites in the open dolines, while the forested dolines did not reveal such a clear pattern. The studied dolines showed a potential to serve as microrefugia in the context of global climate change. Dolines could support the long-term persistence of at least some species such as cold-adapted species. Karst dolines in the temperate zone play a key role in maintaining biodiversity; therefore, they should be central in biodiversity conservation programs.

Regional patterns of zoning hypergenic transformations of sedimentary rocks of the middle Permian age of the Eastern Zakamye

The article is devoted to the study of eluvial deposits in the territory of the Eastern Zakamye. Due to the activity of river erosion, a highly dissected and rugged terrain has formed in this area. Its characteristic elements are erosion-denudation watersheds spaces separated by narrow river valleys and terraced slopes. According to the results of the research, it was revealed that the difference in the structure of weathering profiles in carbonate and terrigenous soil massifs is due to the structural and mineralogical features of rocks acquired at the stage of sedimentation and subsequent diagenesis. In the central part, at the upper plateau site, the rocks underwent mainly physical weathering processes, at the middle plateau site – chemical weathering processes, at the lower plateau site – physical and chemical weathering processes. Such selectivity in the manifestation of hypergenic processes is due to the predominant lithotypes of sedimentary rocks composing the upper, middle and lower plateau surfaces of the plateau of the studied territory. Based on the completed study, the zoning of the territory of the Eastern Zakamye was carried out and an engineering and geological map was built. The results obtained make it possible to understand the mechanism of weathering in carbonate and terrigenous rocks, and, consequently, to assess the potential change in the physical and mechanical properties of rocks, both during construction and during the operation of buildings and structures.

Multi-decadal degradation and fragmentation of palsas and peat plateaus in coastal Labrador, northeastern Canada

Peatland permafrost landforms, such as palsas and peat plateaus, often represent the most southern lowland permafrost occurrences in the Northern Hemisphere. While peatland permafrost is often found in continental conditions, over a thousand permafrost peatlands were recently identified along the previously understudied coastline of the Labrador Sea in northeastern Canada. The vulnerability of these landscapes to thaw is unknown but is expected to have hydrological and ecological impacts on important caribou habitat, the abundance of culturally relevant berries, and permafrost carbon storage. Using a combination of aerial photography (from 1948, 1985, 1992, 1994, and 2021) and high-resolution satellite imagery (from 2017, 2020, and 2021), we assess multi-decadal areal changes to peatland permafrost landforms at seven peatlands along the Labrador Sea coastline spanning from Red Bay (51.7° N) to north of Hopedale (55.7° N). Analyses reveal declines in permafrost extent of 33%–93% at individual sites, occurring at mean rates of 0.8%–1.5%/a. Permafrost loss was found to occur most rapidly at mixed palsa and peat plateau sites (mean rate of 1.4%/a), followed by palsa sites (mean rate of 1.2%/a) and peat plateau sites (mean rate of 0.9%/a). Patterns of permafrost loss also differed between landform types, with more complete loss of individual landforms at palsa sites and more lateral and internal loss of existing landforms at peat plateau and mixed sites. This widespread degradation of peatland permafrost over the past 28–73 years is attributed to regional warming and peatland greening. Understanding recent change to permafrost peatlands in coastal Labrador is an important step towards predicting future habitat change in northeastern Canada and will inform regional land management in areas dominated by these culturally important landforms.

Molecular characterization of organic aerosols over the Tibetan Plateau: Spatiotemporal variations, sources, and potential implications

Organic aerosols have profound and far-reaching influences on the Earth's climate, ecosystems, environmental quality, and public health. Elucidating the precise composition and sources of these aerosols over the Tibetan Plateau, a region highly sensitive to climate change and vulnerable to ecosystems, is critically important. Sixteen organic molecular tracers in aerosols were quantified using solvent extraction-BSTFA derivatization, and GC/MS analysis at six sites over the Tibetan Plateau during 2014 and 2016. Average total tracer concentration was 32.5 ± 20.1 ng m−3. The highest levels of biomass burning tracers (anhydrosugars and aromatic acids) were found at southeastern Tibetan Plateau site Yulong (20.8 ± 21.3 ng m−3) followed by the western site Ngari (13.3 ± 10.6 ng m−3). Biomass burning tracers decreased from southern sites like Everest (9.50 ± 10.5 ng m−3) to northern aeras such as Laohugou (2.59 ± 2.19 ng m−3). Biomass burning tracers peaked in non-monsoon seasons while primary saccharides and sugar alcohols predominated during monsoon months. Using tracer-based methods, biomass burning contributed 0.4%–8.4% of organic carbon over the plateau, with higher non-monsoon contributions (3.6% ± 3.7%). Backward air mass trajectories and fire spots indicated South Asian biomass burning impacts on organic aerosols at western, southern, and southeastern Tibetan Plateau sites, particularly in non-monsoon periods. Fungal spores and plant debris comprised 0.6%–6.3% and 0.3%–1.2% of organic carbon respectively, with higher monsoon contributions (4.2% ± 4.7%) of fungal spores. Secondary organic carbon was estimated to contribute substantially (45.5%–73.5%) over the plateau but requires further investigation. These results provide insights into pollution mitigation and the assessments of climate and ecology changes for the Tibetan Plateau.

High Spatial Variability of Biomass Burning Emissions Observed at Three Tibetan Plateau Sites

AbstractAerosol from biomass burning (BB) can affect regional and global climate by changing radiation balance and cloud properties, especially over the high altitude environ‐vulnerable region. To investigate the contributions of BB on atmospheric particulate matter trans‐the Tibetan Plateau (TP), the total suspended particle samples were collected at three high altitude sites over the northeastern (Qinghai lake, 3,200 m a.s.l.), central (Beiluhe, 4,659 m a.s.l.), and southwestern TP (Ngari, 4,360 m a.s.l.), respectively. Highly spatial variations of BB tracers (including levoglucosan, mannosan, and galactosan) were obtained. Elevated BB tracer concentrations were observed in the northeastern and southwestern sites compared to the central TP site. The heighten concentrations of particulate matter from biomass burning and organic carbon from biomass burning were obtained at Ngari (with 5260.3 and 2257.7 ng m−3) and Qinghai lake (with 1508.8 and 647.6 ng m−3) compared with those at Beiluhe (with 18.8 and 8.1 ng m−3), respectively. The results indicated that the BB contributions to aerosol were significant on the margin of the TP. In addition to the long‐range transport of BB pollutant, the local emissions may be an important contributor in the northeastern and southwestern TP. The present study can improve the understanding of BB characteristics and effects in the TP.

Bulbs and Biographies, Pine Nuts and Palimpsests: Exploring Plant Diversity and Earth Oven Reuse at a Late Period Plateau Site

Bulbs and Biographies, Pine Nuts and Palimpsests: Exploring Plant Diversity and Earth Oven Reuse at a Late Period Plateau Site

A comparison of the spatial heterogeneities of surface fluxes simulated by INLAND model with observations at a valley and a nearby plateau stations in Central Amazon Forest

An improved version of the Integrated Land Surface Model (INLAND), incorporating the physical, ecological and hydrological parameters and processes pertaining to two subclasses of tropical forest in the central Amazon basin, a poorly drained flat plateau and a well-drained adjacent broad valley, is used to simulate the hydrological, energy and CO2 fluxes. The model is forced with observed meteorological data. The experimental output data from the model runs are compared with observational data at the two locations. The seasonal variabilities of water table depth at the valley site and the soil moisture at the plateau site are satisfactorily simulated. The two locations exhibit large differences in energy, carbon and water fluxes, both in the simulations and in the observations. Results validate the INLAND model and indicate the need for incorporating sub-grid scale variability in the relief, soil type and vegetation type attributes to improve the representation of the Amazonian ecosystems in land-surface models.

Aerosol optical properties calculated from size distributions, filter samples and absorption photometer data at Dome C, Antarctica, and their relationships with seasonal cycles of sources

Abstract. Optical properties of surface aerosols at Dome C, Antarctica, in 2007–2013 and their potential source areas are presented. Scattering coefficients (σsp) were calculated from measured particle number size distributions with a Mie code and from filter samples using mass scattering efficiencies. Absorption coefficients (σap) were determined with a three-wavelength Particle Soot Absorption Photometer (PSAP) and corrected for scattering by using two different algorithms. The scattering coefficients were also compared with σsp measured with a nephelometer at the South Pole Station (SPO). The minimum σap was observed in the austral autumn and the maximum in the austral spring, similar to other Antarctic sites. The darkest aerosol, i.e., the lowest single-scattering albedo ωo≈0.91, was observed in September and October and the highest ωo≈0.99 in February and March. The uncertainty of the absorption Ångström exponent αap is high. The lowest αap monthly medians were observed in March and the highest in August–October. The equivalent black carbon (eBC) mass concentrations were compared with eBC measured at three other Antarctic sites: the SPO and two coastal sites, Neumayer and Syowa. The maximum monthly median eBC concentrations are almost the same (∼3±1 ng m−3) at all these sites in October–November. This suggests that there is no significant difference in eBC concentrations between the coastal and plateau sites. The seasonal cycle of the eBC mass fraction exhibits a minimum f(eBC) ≈0.1 % in February–March and a maximum ∼4 %–5 % in August–October. Source areas were calculated using 50 d FLEXPART footprints. The highest eBC concentrations and the lowest ωo were associated with air masses coming from South America, Australia and Africa. Vertical simulations that take BC particle removal processes into account show that there would be essentially no BC particles arriving at Dome C from north of latitude 10∘ S at altitudes <1600 m. The main biomass-burning regions Africa, Australia and Brazil are more to the south, and their smoke plumes have been observed at higher altitudes than that, so they can get transported to Antarctica. The seasonal cycle of BC emissions from wildfires and agricultural burning and other fires in South America, Africa and Australia was calculated from data downloaded from the Global Fire Emissions Database (GFED). The maximum total emissions were in August–September, but the peak of monthly average eBC concentrations is observed 2–3 months later in November, not only at Dome C, but also at the SPO and the coastal stations. The air-mass residence-time-weighted BC emissions from South America are approximately an order of magnitude larger than from Africa and Oceania, suggesting that South American BC emissions are the largest contributors to eBC at Dome C. At Dome C the maximum and minimum scattering coefficients were observed in austral summer and winter, respectively. At the SPO σsp was similar to that observed at Dome C in the austral summer, but there was a large difference in winter, suggesting that in winter the SPO is more influenced by sea-spray emissions than Dome C. The seasonal cycles of σsp at Dome C and at the SPO were compared with the seasonal cycles of secondary and primary marine aerosol emissions. The σsp measured at the SPO correlated much better with the sea-spray aerosol emission fluxes in the Southern Ocean than σsp at Dome C. The seasonal cycles of biogenic secondary aerosols were estimated from monthly average phytoplankton biomass concentrations obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite sensor data. The analysis suggests that a large fraction of the biogenic scattering aerosol observed at Dome C has been formed in the polar zone, but it may take a month for the aerosol to be formed, be grown and get transported from the sea level to Dome C.

Formation Mechanisms and Source Apportionments of Airborne Nitrate Aerosols at a Himalayan-Tibetan Plateau Site: Insights from Nitrogen and Oxygen Isotopic Compositions.

Formation pathways and sources of atmosphere nitrate (NO3-) have attracted much attention as NO3- had detrimental effects on Earth's ecosystem and climate change. Here, we measured nitrogen (δ15N-NO3-) and oxygen (δ18O-NO3- and Δ17O-NO3-) isotope compositions in nitrate aerosols at the Qomolangma station (QOMS) over the Himalayan-Tibetan Plateau (HTP) to quantify the formation mechanisms and emission sources of nitrate at the background site. At QOMS, the enhanced NO3- concentrations were observed in the springtime. The average δ15N-NO3-, δ18O-NO3-, and Δ17O-NO3- values were 0.4 ± 4.9, 64.7 ± 11.5 and 27.6 ± 6.9‰, respectively. Seasonal variations of isotope ratios at QOMS can be explained by the different emissions and formation pathways to nitrate. The average fractions of NO2 + OH and N2O5 + H2O to nitrate production were estimated to be 43 and 52%, respectively, when the NO3 + hydrocarbon (HC)/dimethyl sulfide (DMS) (NO3 + HC/DMS) pathway was assumed to be 5%. Using stable isotope analysis in the R (SIAR) model, the relative contributions of biomass burning (BB), biogenic soil emission, traffic, and coal combustion to nitrate were estimated to be 28, 25, 24, and 23%, respectively, on yearly basis. By FLEXible PARTicle (FLEXPART) dispersion model, we highlighted that NOx from BB emission over South Asia that had undergone N2O5 + H2O processes enhanced the nitrate concentrations in the springtime over the HTP region.

Middle Miocene Temperature and Productivity Evolution at a Northeast Atlantic Shelf Site (IODP U1318, Porcupine Basin): Global and Regional Changes

AbstractWe present a high‐resolution multiproxy middle Miocene sea surface temperature (SST) and productivity (SSP) reconstruction of Integrated Ocean Drilling Program Site U1318, from the upper slope edge (∼400 m water depth) of the Porcupine Basin continental margin, eastern North Atlantic Ocean. Biomarker and dinoflagellate cyst proxies reveal warm and mostly stratified waters during the Miocene Climatic Optimum (MCO) that cooled ∼3°C across the Miocene Climate Transition (MCT). The organic biomarker (TEX86 and ) paleothermometers document a series of 11 transient cooling events (CEs), superimposed on the long‐term climate evolution. These CEs are associated with increases in cold‐water dinocysts and correlate to global benthic δ18O shifts, including the Mi‐2, Mi‐3, and Mi‐4 events. Most CEs are also associated with increases in primary productivity. A prolonged interval of high SSP between ∼13.8 and 13.6 Ma supports the idea that carbon production (and burial) in shallow areas represents a feedback mechanism contributing to long‐term atmospheric CO2 decline and cooling during the MCT. SST comparison in three North Atlantic sites (Azores Site 608, Porcupine Basin Site U1318, and Rockall Plateau Site 982) reveals that MCO SSTs are much warmer at Site 608 than at the other two sites. The low‐resolution SST record of Site 982 shows no decrease in temperature around the MCT. This may be linked to contemporaneous tectonic changes in the Tethys, Central American, and Arctic Seaways impacting local ocean circulation, superimposed on global drivers of climate change.

Managing climate change microrefugia for vascular plants in forested karst landscapes

Microrefugia are small areas that support favourable climate and allow species to persist during regional and global climate changes. Dolines in karst landscapes may provide such areas for many climate change-vulnerable species. Here we provide a better understanding on how plant species indicate changes in their environment (temperature, soil moisture and light availability) after a few years of partial canopy removal from dolines and their close surroundings (logged areas: >1 ha). We place our results in the context of the most widely used forest management practices within the study area (Mecsek Mts, Hungary), in addition to presenting a general framework for the maintenance of doline microrefugia in forested karst landscapes. Three types of habitats were investigated: dolines before logging, dolines after logging, and the forested plateau. Three large dolines and three sites on the plateau were selected for vegetation sampling. All dolines were sampled before logging and 5–10 years after partial canopy removal. Logging resulted in a 50–80% reduction of canopy cover in the dolines and their close surroundings. We established a transect across each doline from north to south passing through doline bottoms, and across each plateau site. We estimated the percentage cover of vascular plant species (tree saplings – up to 1 m in height, shrubs and herbs) along the transects using 1 m × 1 m vegetation plots, determined the diagnostic species of the doline and plateau habitats, and used multivariate methods and linear mixed-effects models during analyses. Plant species indicated clear gradients of the main microclimatic factors within the dolines and that significant changes took place after logging. Canopy removal caused substantial changes in the main microclimatic factors of most doline microhabitats (e.g., south-facing slopes). The vegetation of the dolines before logging indicated moister conditions than that of the plateau and cooler and shadier conditions than that of the dolines after logging. These and our previous results suggest that logging may directly and indirectly influence dolines to be microrefugia under global warming. By applying our framework to refugia conservation and management for the karst landscape in the Mecsek Mts, we can conclude that the protection of old forests and natural forest dynamics in as many large dolines as possible and the implementation of close-to-nature forestry practices may be essential to maintain regional biodiversity in the long run.

Environmental Stress Tolerance and Antioxidant Response of Palisada perforata (Rhodophyta) from a Tropical Reef1.

In this study, we analyzed the antioxidant activity and total phenolic content of the intertidal seaweed Palisada perforata collected from different reef microhabitats (sheltered site, tide pool, plateau, and exposed site) along the coast of Pernambuco (Brazil). Both parameters were compared with the same parameters of this species grown in the laboratory under two experiments simulating temperature, salinity, and desiccation conditions found in the reef. After both experiments (temperature x salinity and desiccation), the algal photosynthetic performance was measured through chlorophyll fluorescence parameters using a pulse-amplitude modulation fluorometer to test their stress response. Palisada perforata likely underwent stress by desiccation due to tidal fluctuations rather than to temperature or salinity changes. This conclusion agrees with our observations of the plateau site´s specimens, which were exposed to both air and UV radiation during low tides and exhibited higher antioxidant activity to avoid oxidative damage. However, despite the environmental stress, the antioxidant activity remained low, suggesting that photoinhibition is a crucial protection mechanism against oxidative damage.

Determination of Cd, Pb, and Cu in the Atmospheric Aerosol of Central East Antarctica at Dome C (Concordia Station).

Trace heavy metals Cd, Pb, and Cu were determined (by square wave anodic stripping voltammetry) in aerosol samples collected at Dome C (the Italo-French Station Concordia), a remote site of the Central East Antarctic plateau, for which no data are available until now. During the Austral Summer 2005–2006, three PM10 high-volume impactors were installed in two locations nearby of Concordia station: the first one very close and downwind of the station (about 50 m north), the other two (very close to each other) in a ‘distant’ site, upwind of the station and close to the astrophysics tent (not used in that expedition) at ~800 m south of Station Concordia. For each sample, the availability of the mass of the aerosol collected (obtained by differential weighing carried out on site), in addition to the volume of the filtered air, allowed us to express results both in terms of metal mass fractions in the aerosol and in the usual way of metal atmospheric concentrations. Metal contents increased in the order Cd < Pb < Cu with the following ranges of values: Cd 1.0–8.4 µg g−1 (0.09–3.1 pg m−3), Pb 96–470 µg g−1 (12–62 pg m−3), and Cu 0.17–20 mg g−1 (0.027–2.4 ng m−3). From the metal temporal profiles obtained we estimated the following background values for the area of Dome C, expressed both in mass fractions and in atmospheric concentrations: Cd 1.2 ± 0.2 µg g−1 (0.24 ± 0.13 pg m−3), Pb (here fixed as upper limit) 113 ± 13 µg g−1 (21 ± 8 pg m−3), and Cu 0.91 ± 0.48 mg g−1 (0.12 ± 0.07 ng m−3). The highest values were observed in the first part of the season, and particularly for the site close to the station, possibly related to sample contamination linked to intense activity at the Concordia station connected with the beginning of the expedition, including aircraft arrivals/departures. Increments of up to 10 times (and even 20 times for Cu) were recorded with respect to the background values. The metal excesses of the contaminated over background samples were found approximately, except for Cu, in the same proportion of the metal contents of the special Antarctic blend (SAB) diesel fuel, which is used almost exclusively at Concordia Station. The effect of the wind direction was also observed. Thus in the intermediate period of the campaign, when the wind direction reversed for several days with respect to the prevailing one, Cd and Pb metal contents decreased at the sampling point installed close to the station, now upwind of Concordia station, and increased at the ‘clean’ site astrophysics tent, turned downwind at the main station. No simple and easily interpretable effect of the wind direction was observed for Cu, which suggests that some other extemporaneous and not clearly identified factor may have intervened in this case. These results suggest that the human impact at Dome C influences mainly the zone very close to the station, but also the area in the neighborhood, including the supposed clean site of the astrophysics tent (about 800 m far from the station), when the wind direction reverses with respect to the prevailing one, leaving the site downwind of the station Concordia. Since no other data are reported for the Dome C area, our results are compared with literature data referred to the South Pole Station (the only other plateau site for which data are available) and several other coastal Antarctic sites, observing that our results (excluding Cu) are the lowest ever observed for Antarctic aerosol.

Unexpected High Absorption of Atmospheric Aerosols Over a Western Tibetan Plateau Site in Summer

AbstractThe assessment of atmospheric aerosol radiative effects in the Tibetan Plateau (TP) suffers from large uncertainties due to limited understanding of aerosol physicochemical properties. To quantify aerosol optical properties, size distributions, and chemical compositions in the western TP, an intensive field campaign was carried out at Shiquanhe National Reference Climatological Station from July 8 to August 2, 2019. Unexpected low single scattering albedo (SSA) at 870 nm was found for the fine aerosols with an average value of 0.73 ± 0.18. SSA was even lower than 0.60 in the morning when fine aerosols peaked, indicating high absorption of the fine aerosols induced by anthropogenic activities. Coarse mode aerosols accounted for 70.58% ± 14.98% of the total volume concentration and mineral dust was the most abundant species in total suspended particles with a mass fraction of 48.7%. Fine mode aerosol concentrations showed little dependence on wind speed while coarse mode aerosols and metallic element concentrations exhibited strong positive correlations with wind speed, indicating the importance of wind‐blown dust particles. The present study for the first time quantified key aerosol parameters in the western TP and unexpected high absorption of atmospheric aerosols were found over the site in summer. Our results suggest the need to carefully consider the radiative effects caused by aerosol absorption in the TP region.

The vertical profiles of carbonaceous aerosols and key influencing factors during wintertime over western Sichuan Basin, China

With Tibetan Plateau higher than 4 km to the west, the location of Sichuan Basin is unique all around the world and provides a good platform to study air pollution in the urban agglomerations over the complex terrain. To fill in the blanks on vertical distributions of PM1 (the particles smaller than 1 μm) and carbonaceous aerosols within the basin, by means of high topographic relief, PM1 were off-line sampled during 20 January to 2 February 2018 at eight sites with increasing altitudes from the basin to southeastern margins of the Tibetan Plateau. The regional potential sources for each site were revealed by HYbrid-Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and concentration-weighted trajectory (CWT) method. The lowest carbonaceous aerosol levels occurred at Lixian, while the highest OC (organic carbon) (EC, elemental carbon) was at Hongyuan (the altitude of 3500 m) (Ande, a rural site) due to more primary emissions. The pollutants inside the basin can be transported the altitudes from 2 km to 3 km by vertical dispersion, but they cannot be dispersed to higher altitudes. The vertical stratification of the pollutants was obvious and easily formed “high-low-high” pattern from Sichuan Basin to southeastern Tibetan Plateau, especially during highly polluted episodes. The regional potential sources significantly varied as the increased altitudes. Regional pollution was significant inside the basin. The sources at the altitudes from 2 km to 3 km originated from southeastern margins of the Plateau and surrounding cities, while those at higher altitudes were transported from southeastern margins of the Plateau. The impact of basic meteorological variables (temperature, wind speed and vapor pressure) on carbonaceous aerosols was opposite between the basin and Plateau sites. This study was essential to understanding formation mechanisms of severe pollution episodes and thus to making control measures for the urban agglomerations inside the mountainous terrain.

Using Age Tracers and Decadal Sampling to Discern Trends in Nitrate, Arsenic, and Uranium in Groundwater Beneath Irrigated Cropland.

Repeat sampling and age tracers were used to examine trends in nitrate, arsenic, and uranium concentrations in groundwater beneath irrigated cropland. Much higher nitrate concentrations in shallow modern groundwater were observed at both the Columbia Plateau and High Plains sites (median values of 10.2 and 15.4 mg/L as N, respectively) than in groundwater that recharged prior to the onset of intensive irrigation (median values of <1 and <4 mg/L as N, respectively). Repeat sampling of these well networks indicates that high nitrate concentrations in modern, shallow groundwater have been sustained for decades, posing a future risk to older, deeper groundwater used for drinking water. In fact, nitrate concentrations in older modern water (30-60 years since recharge) at the High Plains site have increased in the past decade. Groundwater irrigated areas in the Columbia Plateau tend to have higher nitrate concentrations in groundwater than surface water irrigated areas,suggesting repeated dissolution of land applied fertilizer during recirculation may be an important factorcausing high nitrate concentrationsin groundwater. Mobilization of uranium and arsenic by land surface activities is suggested by the higher concentrations of these constituents in modern, shallow groundwater than in older, deeper groundwater at the Columbia Plateau site. Bicarbonate concentrations in modern groundwater are positively correlated with uranium (r = 0.72, p < 0.01), suggesting bicarbonate may mobilize uranium in this system. A positive correlation between arsenic and phosphorus concentrations in modern groundwater (r = 0.55, p < 0.01) suggests that phosphate from fertilizer outcompetes arsenate for sorption sites, mobilizing sorbed arsenic derived from past pesticide use or other sources.

Multivariate analysis of elements from the microhabitats of selected plateaus in the Western Ghats, Maharashtra, India

The Western Ghats represents a small part of the Deccan Traps continental flood basalt province that erupted about 65 million years ago. It is an area of outstanding scenic beauty and has attracted the attention of geologists, naturalists and geomorphologists for over a century. One of the unique habitats in the Western Ghats are the rocky plateaus. Previous studies have covered plant species composition, geological and geomorphological status of the rocky plateaus. An analytical study of microhabitats and associated therophytes of four rocky plateau sites was conducted. The study sites were Durgawadi Plateau, Naneghat Plateau which are basalt outcrops and Zenda plateau and Amba Plateau, which are laterite outcrops on the escarpment of the northern Western Ghats. The results revealed a correlation between basalt and lateritic rock outcrops as well as ephemeral plant elements. All four outcrops are similar in their nutrient status but the microhabitats of these plateaus are extremely different from each other.&#x0D;

Spatial and seasonal variations of sugars (alcohol) in China: Emerging results from the CARE-China network

The “Campaign on Atmospheric Aerosol Research” network of China (CARE-China) is a long-term project for the study of the spatio-temporal distributions of physical aerosol characteristics as well as the chemical components and optical properties of aerosols over China. This study presents the size-segregated sugars from the CARE-China network. Sugars associated with size-segregated particulate matter at 8 regions (North China (NC), East China (EC), Northeast China (NE), and Central China (CC), South China (SC), Northwest China (NE), Southwest China (SW) and the Tibetan Plateau (TP)) including 14 sites over China from January 2013 to December 2014 were analyzed via gas chromatography mass spectrometry. Mass concentrations of measured sugars varied considerably with location and season, ranging from 0.20 to 5588 ng m−3, with the majority from levoglucosan (170 ± 207 ngm−3, accounting for 48% of total sugars), followed by sucrose (44.6 ± 39.6 ngm−3, accounting for 11.3% of sugar), and sorbitol (35.5 ± 42.2 ng m−3, accounting for 10.0% of sugars). The highest levels of sugars were observed in urban sites in Central and Southwest China, whereas the lowest concentrations occurred in background and Tibetan Plateau sites. A distinct seasonal variability of sugars was observed, with higher in the winter or autumn and lower during the summer at urban sites. Inconsistent seasonal trends were observed at the background sites located in the higher latitudes, which were characteristic with the highest concentration occurred in spring. Levoglucosan, galactosan and mannosan were found to be dominant in fine size range <1.1 μm, accounting approximately 59% of all size-segregated sugars. Sucrose was enriched in the size range of 3.3–9.0 μm for almost all sampling sites. Concentrations of trehalose and sorbitol in the three size particles were similar. The OC from biomass burning was estimated to be in the range of 0.93–58.7 μg C m−3, with the highest level OCBB% were observed in urban sites in summer and winter. The contributions of biomass burning to OC in the rest of sites were higher in autumn and winter than in spring and summer. Higher OCBB% was observed in spring at the background sites located in Northwest and Northeast China.