Local Source Areas Research Articles

New insights into the sources of atmospheric lead reaching the Arctic by isotopic analysis of PM10 atmospheric particles and resuspended soils

Lead concentration, crustal enrichment factor, and isotope ratios (including those with the less abundant 204Pb) have been measured in PM10 samples collected at Ny-Ålesund (Svalbard Islands) from October 2018 to November 2020, including, for the first time, the autumn and winter seasons. In addition, resuspended soil samples from Svalbard Islands, Iceland, and Alaska were prepared and analysed to provide reference values for local and short-range potential source areas, and back-trajectory analysis was applied to corroborate the findings based on the Pb isotopic signatures.Results showed that the atmospheric Pb concentration reached its maximum in January, progressively decreased until August, remained low until November, and increased again in December. The Pb isotopic composition also showed a clear temporal variation, indicating a shift in the Pb sources with the changing seasons, in agreement with the back-trajectory analysis results. Lead in PM10 samples collected from November to May was entirely (>99%) anthropogenic, and it likely derived from the mining activities in East Kazakhstan and the Altai region, specifically at Leninogorsk (now Ridder). In contrast, the Pb isotopic composition of particulate samples collected from June to October reflected mixed anthropogenic contributions from the North-East USA and Canada, with a significant contribution from natural sources.

Modern periglacial eolian deposits and landforms in the Søndre Strømfjord area, West Greenland and their palaeoenvironmental implications

Modern fluvio glacial sediments in two east-west oriented valleys between Søndre Strømfjord Air Base and the Inland Ice (West Greenland) are partly redeposited by eolian activity. Topographic barriers have induced an areal distinction between sandy and silty eolian sediments. Morphological and sedimentological investigations enable a facies analysis of these rare, active cold-climate eolian deposits and a comparison with the extensive Pleistocene sand sheets and loess deposits of Europe.
 Eolian processes are active throughout the year in a dry cold-climate environment. Accumulation of eolian material on the eolian sand sheets and silt covers mainly takes place in summer, whereas deflation and redeposition is dominant in winter. Meteorological conditions (especially thickness of snow cover) may prevent eolian activity.
 The vegetation on the sand sheets adapts itself to the intensity of the eolian activity. Vegetation is scarce in the low areas near the active flood plains where deflation is intensive, whereas the downwind depositional areas are more densely vegetated. Only a few species play an active role in the formation of small phytogenic dunes, which are characterized by a low preservation potential. Similar conditions are envisaged for the extensive Pleistocene sand seas of northwestern Europe.
 A characteristic sedimentary sequence occurs in downwind, upslope direction. Fluvio-eolian deposits on and near the active flood plain are characterized by horizontally bedded eolian sand interbedded with fluvial deposits. The latter are partly winnowed by eolian activity leading to inversely graded lamination. Horizontal bedding of fine-medium grained sand interbedded with thin coarse-grained strata is the proximal facies of cold-climate eolian sand sheets. Within-bed structures are dominated by plane bed lamination. A more homogeneous (fine-medium grained) horizontally bedded sediment, comparable to that dominating in the extensive Pleistocene sand sheets, represents the distal facies of these sand sheets.
 The uplands are covered by eolian silt deposits. These are coarser than 'typical' loess and lack other loess characteristics. This is explained by the local source area and the short transport distance. These 'proximal loess' deposits are mainly deposited on the windward side of the valley walls due to blocking of dust-laden airflows by these topographic barriers. The primary micro-lamination in these deposits may also have been present in the Pleistocene loess deposits.

Microscale pollen release and dispersal patterns in flowering grass populations

Characterizing pollen release and dispersion processes is fundamental for knowledge advancement in ecological, agricultural and public health disciplines. Understanding pollen dispersion from grass communities is especially relevant due to their high species-specific allergenicity and heterogeneously distributed source areas. Here, we aimed to address questions concerning fine level heterogeneity in grass pollen release and dispersion processes, with a focus on characterizing the taxonomic composition of airborne grass pollen over the grass flowering season using eDNA and molecular ecology methods. High resolution grass pollen concentrations were compared between three microscale sites (<300 m apart) in a rural area in Worcestershire, UK. The grass pollen was modelled with local meteorology in a MANOVA (Multivariate ANOVA) approach to investigate factors relevant to pollen release and dispersion. Simultaneously, airborne pollen was sequenced using Illumina MySeq for metabarcoding, analysed against a reference database with all UK grasses using the R packages DADA2 and phyloseq to calculate Shannon's Diversity Index (α-diversity). The flowering phenology of a local Festuca rubra population was observed. We found that grass pollen concentrations varied on a microscale level, likely attributed to local topography and the dispersion distance of pollen from flowering grasses in local source areas. Six genera (Agrostis, Alopecurus, Arrhenatherum, Holcus, Lolium and Poa) dominated the pollen season, comprising on average 77 % of the relative abundance of grass species reads. Temperature, solar radiation, relative humidity, turbulence and wind speeds were found to be relevant for grass pollen release and dispersion processes. An isolated flowering Festuca rubra population contributed almost 40 % of the relative pollen abundance adjacent to the nearby sampler, but only contributed 1 % to samplers situated 300 m away. This suggests that most emitted grass pollen has limited dispersion distance and our results show substantial variation in airborne grass species composition over short geographical scales.

Dominant source areas shift seasonally from longitudinal to lateral contributions in a montane headwater stream

Montane ecoregions are important vehicles for downstream hydrologic function, but their dynamics are relatively understudied compared to alpine and subalpine catchments in the western United States. Montane catchments experience shifts in precipitation inputs seasonally, which results in spatiotemporal differences in source area contributions to the stream. We collected hydrometric and geochemical data between 2018 and 2021 from a 2.65 km2 semi-arid headwater catchment in the Front Range of Colorado, USA. Using a combined approach of hydrometric monitoring, geochemical characterization, and end-member mixing analysis (EMMA), we assess hydrologic connectivity between areas with high upslope accumulation and the stream. Within our study area, high upslope accumulation area corresponded to alluvial/ colluvial fans wherein we focused instrumentation and water sample collection. Using observed rainfall, and multiyear measurements of groundwater levels, soil moisture, and streamflow, we observed distinct hydrologic seasons within our catchment characterized by snowmelt during the spring, rainstorms during the summer, and a return to baseflow during the fall. Within this framework, we found that source areas to streamflow shift with longitudinal distance downstream, and among hydrologic seasons. Notably, our EMMA results indicate that contributions from upstream source areas become less important than lateral inputs from spring snowmelt into the fall return to baseflow. This was most pronounced at the upper catchment where upstream contributions to streamflow decreased up to 33.3% between spring and fall. These results suggest that streamflow is maintained by local source areas contributing laterally and vertically. Our results reflect dynamic shifts in hydrologic connectivity in space and in time, which are increasingly important to land and water resource management given rapid climate changes within the western United States.

Heavy and Light Mineral Association of Late Quaternary Permafrost Deposits in Northeastern Siberia

We studied heavy and light mineral associations from two grain-size fractions (63–125 μm, 125–250 µm) from 18 permafrost sites in the northern Siberian Arctic in order to differentiate local versus regional source areas of permafrost aggradation on the late Quaternary time scale. The stratigraphic context of the studied profiles spans about 200 ka covering the Marine Isotope Stage (MIS) 7 to MIS 1. Heavy and light mineral grains are mostly angular, subangular or slightly rounded in the studied permafrost sediments. Only grains from sediments with significantly longer transport distances show higher degrees of rounding. Differences in the varying heavy and light mineral associations represent varying sediment sources, frost weathering processes, transport mechanisms, and post-sedimentary soil formation processes of the deposits of distinct cryostratigraphic units. We summarized the results of 1141 microscopic mineral analyses of 486 samples in mean values for the respective cryostratigraphic units. We compared the mineral associations of all 18 sites along the Laptev Sea coast, in the Lena Delta, and on the New Siberian Archipelago to each other and used analysis of variance and cluster analysis to characterize the differences and similarities among mineral associations. The mineral associations of distinct cryostratigraphic units within several studied profiles differ significantly, while others do not. Significant differences between sites as well as between single cryostratigraphic units at an individual site exist in mineral associations, heavy mineral contents, and mineral coefficients. Thus, each study site shows individual, location-specific mineral association. The mineral records originate from multiple locations covering a large spatial range and show that ratios of heavy and light mineral loads remained rather stable over time, including glacial and interglacial periods. This suggests mostly local sediment sources and highlights the importance of sediment reworking under periglacial regimes through time, including for example the formation of MIS 1 thermokarst and thermo-erosional deposits based on remobilized MIS 3 and 2 Yedoma Ice Complex deposits. Based on the diverse mineralogical results our study supports the viewpoint that Yedoma Ice Complex deposits are mainly results of local and polygenetic formations (including local aeolian relocation) superimposed by cryogenic weathering and varying climate conditions rather than exclusive long distance aeolian transport of loess, which would have highly homogenized the deposits across large regions.

Flint sources and mobility at the Chalcolithic (3500–2200 BCE) settlement of Zambujal (Portugal)

AbstractProvenance studies of the siliceous sedimentary raw material used by ancient communities are essential to understanding the mobility and exchange networks of these communities. The establishment of the direct procurement territory is the first step to understanding the role of the ‘imported’ artefacts. In this study, flint cores, flakes, bladelets and debitage from the Chalcolithic settlement of Zambujal (Estremadura, Portugal), recovered in excavations between 1964 and 1979, are analysed. We attempt to identify the local and regional source areas of these stone materials and compare their petrography (facies and microfacies textures). This study demonstrates the importance of employing three scales of analysis in petrographic studies (the macro‐, meso‐ and micro‐) to structure and determine flint provenance. Analysis of cortical material shows the relevance of secondary detrital outcrops during the Chalcolithic of the Portuguese Estremadura. Small cobbles were directly collected in both local and regional formations dated to the Palaeogene and Cenomanian, in a large (approx. 40 km) exploration territory, to produce expedient and specialized artefacts (i.e., bladelets). However, a large portion of stone tools from Zambujal made from Cenomanian flint cannot be assigned to local or regional procurement. The unclear provenance of these materials suggests directions for future research.

Selected Grain-Size and Geochemical Analyses of the Loess-Paleosol Sequence of Pécel (Northern Hungary): An Attempt to Determine Sediment Accumulation Conditions and the Source Area Location

The loess-paleosol profile near the settlement of Pécel has a notable size among the loess-paleosol sequences of the Northern Carpathian territories. Therefore, comprehensive sedimentological examinations were performed to understand the profile and the information preserved in it. The past periodicity and intensity of winds were showed by particle composition studies (GSI, U-ratio). At least two source areas can be presumed based on geochemical indices (CIA, CIW, Rb/Sr, Zr/Rb). Based on the characteristics of the chemical composition of sulphide minerals (P, S, Pb, Ni, As sulphides), the lower 10 m of the profile was supposed to be transported from the NW direction (Buda Thermal Karst, Börzsöny, Cserhát). Sufficient information is not yet available in order to determine the source area of the upper 10 m. By using the mentioned indexes, major developing and weathering horizons also could be identified.

Paleogeographic constraints on source area and depositional systems in the Neoproterozoic Irecê Basin, São Francisco Craton

Neoproterozoic carbonate sequences overlying the Middle Cryogenian glacial deposits in the Sao Francisco Craton are included in the Salitre Formation within the Irecê Basin. Stratigraphic, elemental, and stable isotope geochemistry, and SHRIMP U–Pb detrital zircon analyzes of the Salitre Formation's Unit B are presented. The lower and intermediate sections of Unit B register three different depositional zones: basin, outer ramp, and middle ramp settings. The carbon isotope record is close to 0.0‰ to slightly negative for δ13C, suggesting an ocean isotopic signature. Detrital zircon grains occur in two different age distributions: (a) zircon grains from lower Unit B have ages of ca. 3.38, 2.56, and 2.07 Ga; and (b) zircon grains from the middle Unit B have the same ages plus 1.78 and 1.50 Ga. The Archean and Paleoproterozoic detrital zircon age distribution resembles the age distribution of the Gavião Block within the São Francisco Craton, which is the substratum for the Irecê Basin deposition. This implies a local source area, which includes granite–gneiss and greenstone belt associations. The Mesoproterozoic zircon grains in the São Francisco Craton are chrono-correlated to volcanic rocks preserved in the Espinhaço Group. The change in the detrital zircon age distribution is followed by a change in the carbonate facies, suggesting a possible unconformity from lower to middle Unit B. The youngest detrital zircon grain indicates the maximum depositional age of Salitre Formation of ca. 670 Ma. Results demonstrate that the Irecê Basin formed in a gulf-like basin as an extension of the Neoproterozoic passive margin at the end of the Sturtian or Marinoan glaciation.

Revealing Sediment Transport Pathways and Geomorphic Change in Washover Fans by Combining Drone‐Derived Digital Elevation Models and Single Grain Luminescence Data

AbstractChronostratigraphic investigations on coastal sedimentary records such as washover fans or beach‐ridge sequences may be used to reconstruct storm chronologies on centennial to millennial time scales. However, modern analogs are pivotal in interpreting depositional processes and reducing uncertainty in evaluating the complex chronostratigraphic architecture of these landforms. Such a modern analog was provided by category 3 tropical cyclone (TC) Olwyn in 2015, which caused a significant storm surge in the Exmouth Gulf (Western Australia). Pre‐ and post‐TC Olwyn geomorphological surveys and high‐resolution drone‐derived topographical data of a large washover fan document a detailed history of erosion and deposition during the event. The modern analog deposits provided an excellent opportunity to evaluate the use of luminescence‐based proxies (luminescence inventories) for tracing event‐related sediment source environments and understanding transport processes. Sediments deposited during Olwyn show a systematic relationship between luminescence characteristics and washover fan position. Seaward and central washover sections are indicated by well‐bleached deposits due to the beach as the dominant source and/or long transport distances. Lateral washover deposits are characterized by rather local source areas and short transport distances, resulting in higher remnant ages of 70–140 a. Our data show that the combination of sediment source environments and sediment transport length across the fan represents the main control in resetting the luminescence signal and enabling reliable depositional ages to be calculated. It documents the benefit of investigating luminescence inventories when establishing chronologies from complex sedimentary records, thereby demanding a careful consideration of local processes and source areas when interpreting sedimentary TC records.

Aeolian Remobilisation of Volcanic Ash: Outcomes of a Workshop in the Argentinian Patagonia

During explosive volcanic eruptions, large quantities of tephra can be dispersed and deposited over wide areas. Following deposition, subsequent aeolian remobilisation of ash can potentially exacerbate primary impacts on timescales of months to millennia. Recent ash remobilisation events (e.g., following eruptions of Cordón Caulle 2011; Chile, and Eyjafjallajökull 2010, Iceland) have highlighted this to be a recurring phenomenon with consequences for human health, economic sectors, and critical infrastructure. Consequently, scientists from observatories and Volcanic Ash Advisory Centers (VAACs), as well as researchers from fields including volcanology, aeolian processes and soil sciences, convened at the San Carlos de Bariloche headquarters of the Argentinian National Institute of Agricultural Technology to discuss the “state of the art” for field studies of remobilised deposits as well as monitoring, modeling and understanding ash remobilisation. In this article, we identify practices for field characterisation of deposits and active processes, including mapping, particle characterisation and sediment traps. Furthermore, since forecast models currently rely on poorly-constrained dust emission schemes, we call for laboratory and field measurements to better parameterise the flux of volcanic ash as a function of friction velocity. While source area location and extent are currently the primary inputs for dispersion models, once emission schemes become more sophisticated and better constrained, other parameters will also become important (e.g., source material volume and properties, effective precipitation, type and distribution of vegetation cover, friction velocity). Thus, aeolian ash remobilisation hazard and associated impact assessment require systematic monitoring, including the development of a regularly-updated spatial database of resuspension source areas.

Depositional architectures and sedimentation processes in strike-slip extensional basins: Examples from the Oligocene of the Liaodong Bay Sub-basin, Bohai Bay Basin, China

The tectonic histories of continental rift basins tend to be complex, with several episodes of subsidence, extensional and strike-slip tectonic activity and diverse paleogeographic characteristics. Intrabasinal and extrabasinal source areas influence deposition resulting in several sedimentary episodes and depositional architectures. In this study, we use 3D seismic data covering Liaodong Bay and well-logging data to analyze sediment source area, paleo-valleys, and slopes to determine the characteristics, distribution and relationships between the source, transport, and sedimentary systems in the Liaodong Bay Sub-basin, which is an Oligocene strike-slip extensional basin with two regional extrabasinal source areas and a local intrabasinal source area in the basin fill succession. Four types of basin-marginal fluvial paleo-valleys are identified in the Liaodong Bay Sub-basin including incised V-, bifurcate V-, wide V- and shallow V- types. The energy of current decreased successively from incised V-, to bifurcate V-, to wide V-type valleys, which ultimately evolved to become shallow V- type during the late stages of a rift lake basin. These sedimentary systems are grouped into five extrabasinal and two intrabasinal types with diverse depositional architectures, based on their slope shapes. The sedimentation processes of the Liaodong Bay Sub-basin were influenced by the tectonic activity, paleogeomorphology and climate condition during the different stages of the strike-slip extensional basin and controlled the accumulation of sandy sediments.

A tale of two cities: The influence of urban meteorological network design on the nocturnal surface versus canopy heat island relationship in Oklahoma City, OK, and Birmingham, UK

AbstractInterest in the investigation of the relationship between surface heat island intensity (sUHII) and canopy heat island intensity (aUHII) (sUHII‐aUHII relationship) is growing mainly because of the global availability of satellite‐sensed land surface temperature (Ts). It is hoped that if such a universal relationship can be found, it could compensate for the spatial discontinuity of air temperature (Ta) measurements that currently exist due to a paucity of weather stations in urban areas. In an attempt to investigate differences in the relationship in different urban environments, this study attempts to compare the linear sUHII‐aUHII relationship between Oklahoma City, OK, and Birmingham, UK, based on the observations from Moderate Resolution Imaging Spectroradiometer and two dense urban meteorological networks (UMNs). Regression models and confidence ellipse, with two statistical tests, are applied in the comparison analysis under different climatic conditions with respect to specific ranges of wind speed (WS) and daily‐accumulated solar radiation (DASR). Some general patterns of the linear sUHII‐aUHII relationship are found across the two cities, such as the reduced rate of change of aUHII with respect to sUHII with increasing WS and the non‐negligible advection effect in this relationship. Meanwhile, the differences of the linear sUHII‐aUHII relationship across two cities are reduced under ideal conditions (clear skies, calm and large input of solar radiation from previous day into urban system). More importantly, the results emphasize the influence of the configuration of UMNs on the sUHII‐aUHII relationship. By removing the climatic element in the relationship (i.e., WS and DASR), the impacts of the different local environments, source areas, and general configurations of the UMN become evident, indicating that a standardized protocol for the designs of UMN is the prerequisite for the generalization of the sUHII‐aUHII relationship across cities.

Planning and prioritizing forest landscape restoration within megacities using the ordered weighted averaging operator

Abstract Forest landscape restoration (FLR) is an efficient approach to address the challenge of megacities’ forest landscape degradation. However, a holistic FLR planning framework economically reconciling human development needs with the integrity of our environment is still lacking. Using the ordered weighted averaging operator, one of the multicriteria evaluation methods, integrated with geographic information system and participatory techniques, this study aims to explore the FLR planning and prioritizing issues for the Miyun Reservoir Catchment, the local strategic surface water source area of Beijing City. A set of planning frameworks was established to flexibly and visually plan the priority areas (subwatersheds) using aggregation operators for weighted biophysical and socioeconomic criteria. As such, a complete spectrum of alternative FLR plans represents the different tradeoffs among criteria and further indicates the complicated interactions between conservation and development objectives. The optimal FLR plans fully considering the local environmental challenges led by severe water crisis should focus more on conservation rather than development with the available resources. The resulting spatial distribution of priority subwatersheds suggests that future FLR activities should be extended more to upstream Hebei Province. Both the conservation plans and sensitivity analysis indicate that the biophysical criteria regarding catchment conservation, particularly the water purification service, should be further emphasized in future FLR planning. Finally, to better balance the objectives of conservation and development, local well-functioning markets of Payment for Ecosystem Services should be fostered step-by-step based on the view of natural capital to achieve the desired “win-win” outcomes.

Backward Probability Model for Identifying Multiple Contaminant Source Zones Under Transient Variably Saturated Flow Conditions

AbstractGroundwater contamination is one of the major concerns to public health and water resource management. Identification of contamination sources is essential for designing cost‐effective groundwater remediation systems and minimizing risks of further contamination. Various numerical approaches have been applied to reconstruct spatiotemporal distributions of contaminant sources. Due to difficulties in obtaining source information, the backward probability model is computationally efficient; however, its applications have largely been limited to relatively simple problems such as two‐dimensional or simplified three‐dimensional steady‐state saturated flow conditions with a single contaminant source. More importantly, the traditional backward probability model requires some a priori knowledge on the suspected source locations or source release times to quantify source area location probabilities. Here we improve the capability of the backward probability model for solving real‐world problems by implementing it into a three‐dimensional transient variably saturated flow model. To evaluate the applicability of the model, we apply it combined with the shift‐average method to a field‐scale problem for identifying multiple contaminant sources occurring in the vadose zone that release contaminants to the saturated zone through infiltration. Compared with the suspected potential sources reported through a site characterization study, the enhanced backward probability model reasonably captures most of the reported potential sources under various hydrologic/hydrogeological/dispersion conditions, which demonstrates that the approach developed here can overcome limitations of the backward probability theory previously reported in the literature.

Quartzite–Schist Sequences of the Aktau–Mointy Massif (Central Kazakhstan): Structural Position, Provenance, and Formation Stages of the Earth Crust in the Precambrian

Detrital zircons from quartzite–schist sequences of the Aktau–Mointy Massif (Central Kazakhstan), which occur in various structural positions relative to the Early Neoproterozoic felsic volcanics, were studied. The obtained U–Pb zircon dating results suggest similarity of detrital zircon age populations with a lower limiting depositional age of 1220 Ma in all quartzite–schist sequences. The different positions of quartzite–schist sequences relative to the felsic volcanics are due to subsequent deformations. The ages of detrital zircons studied fall mostly within the intervals of 1149–2105 and 2354–3159 Ma with major peaks at 1218, 1338, 1468, 1581, 1628, 1743, 1851, and 2520 Ma and minor peaks at 2016, 2619, 2696, 2791, 2823, and 3114 Ma. The structural features of quartzite–schist sequences and the presence of heavy minerals that are unstable during long-term transport indicate the predominance of local source areas, which either form the buried part of the basement of the Aktau–Mointy Massif or have been eroded completely. Within the Aktau–Mointy Massif, it enables us to use the U–Pb ages and Lu–Hf isotope compositions of detrital zircons from quartzite–schist sequences to reconstruct the history of Precambrian continental crust formation. Results suggest that the production of juvenile continental crust prevailed only during Middle Mesoproterozoic, while formation during the Mesoarchean–Neoproterozoic time accompanied magmatic reworking of the older crustal complexes.

Muddying the Picture? Forecasting Particulate Sources and Dispersal Patterns in Managed Catchments

Satellite imagery and climate change projections improve our ability to map and forecast sediment sources and transport pathways at high resolution, which is vital for catchment management. Detailed assessment of temporal and spatial changes in erosion risk are key to forecasting pollutant dispersal, which affects water treatment costs and ecology. Outputs from scenario modeling of the River Derwent catchment, Yorkshire, indicate clear spatial and temporal trends in erosion risk. These trends are not picked up by using traditional methods, which rely on static land use maps. Using satellite-derived maps show that lower resolution traditional land-use maps relatively underestimate erosion risk in terms of location of source areas and seasonal variation in erosion risk. Seasonal variation in agricultural practices can be assessed by incorporating bare land variation into models, which show that erosion risk is relatively overestimated if all agricultural land is assumed to have the same character. Producing seasonal land use maps also allows the assessment of temporal variation in rainfall, which in combination with climate change projections allows for adaptable management plans. The bias in gradient in modeling, which assumes that high gradients result in greater sediment erosion risk, show that traditional models underestimate the contribution of erosion risk in lowland areas. This is compounded by the absence of artificial drainages in topographic rasters, which increases connectivity in lowland areas. By producing end member scenarios, model outputs help to inform where catchment management should be targeted, and whether seasonal interventions should be implemented. This information is vital to communicate with landowners when they implement catchment management practices, such as sediment traps and earth bunds. Adaption of erosion risk modeling practices is urgently needed in order to quantify the impact of artificial interference in which human activity disrupts ‘natural’ sediment source-to sink configurations, such as integrating new pathways and stores due to land use change and management. Furthermore, integrating higher resolution catchment modeling and improved seasonal forecasts of pollutant flux to oceans will permit more effective interventions. This paper highlights single output erosion risk maps are not effective to inform catchment management.

Arctic shrub colonization lagged peak postglacial warmth: Molecular evidence in lake sediment from Arctic Canada.

Arctic shrubification is an observable consequence of climate change, already resulting in ecological shifts and global-scale climate feedbacks including changes in land surface albedo and enhanced evapotranspiration. However, the rate at which shrubs can colonize previously glaciated terrain in a warming world is largely unknown. Reconstructions of past vegetation dynamics in conjunction with climate records can provide critical insights into shrubification rates and controls on plant migration, but paleoenvironmental reconstructions based on pollen may be biased by the influx of exotic pollen to tundra settings. Here, we reconstruct past plant communities using sedimentary ancient DNA (sedaDNA), which has a more local source area than pollen. We additionally reconstruct past temperature variability using bacterial cell membrane lipids (branched glycerol dialkyl glycerol tetraethers) and an aquatic productivity indicator (biogenic silica) to evaluate the relative timing of postglacial ecological and climate changes at a lake on southern Baffin Island, Arctic Canada. The sedaDNA record tightly constrains the colonization of dwarf birch (Betula, a thermophilous shrub) to 5.9±0.1ka, ~3ka after local deglaciation as determined by cosmogenic 10 Be moraine dating and >2ka later than Betula pollen is recorded in nearby lake sediment. We then assess the paleovegetation history within the context of summer temperature and find that paleotemperatures were highest prior to 6.3ka, followed by cooling in the centuries preceding Betula establishment. Together, these molecular proxies reveal that Betula colonization lagged peak summer temperatures, suggesting that inefficient dispersal, rather than climate, may have limited Arctic shrub migration in this region. In addition, these data suggest that pollen-based climate reconstructions from high latitudes, which rely heavily on the presence and abundance of pollen from thermophilous taxa like Betula, can be compromised by both exotic pollen fluxes and vegetation migration lags.

Examining spatiotemporal variability of urban particulate matter and application of high-time resolution data from a network of low-cost air pollution sensors

Traditional air monitoring approaches using regulatory monitors have historically been used to assess regional-scale trends in air pollutants across large geographical areas. Recent advances in air pollution sensor technologies could provide additional information about nearby sources, support the siting of regulatory monitoring stations, and improve our knowledge of finer-scale spatiotemporal variation of ambient air pollutants and their associated health effects. Sensors are now being developed that are much smaller and lower cost than traditional ambient air monitoring systems and are capable of being deployed as a network to provide greater coverage of a given area. The CitySpace project conducted by the US EPA and the Shelby County Health Department included the deployment of a network of 17 sensor pods using Alphasense OPC-N2 particulate matter (PM) sensors integrated with meteorological sensors in Memphis, TN for six months. Sensor pods were collocated with a federal equivalent method (FEM) tapered element oscillating microbalance (TEOM) monitor both before and after the primary study period. Six of the sensor pods were found to meet the data quality objective (DQO) of coefficient of determination (R2) greater than 0.5 when collocated with the TEOM. Seven pods were decommissioned before the end of the study due to mechanical failure. The six pods meeting the DQO were used to examine the spatiotemporal variability of fine PM (PM2.5) across the Memphis area. One site was found to have higher relative PM2.5 concentrations when compared to the other sites in the network. The 1-min data from this sensor pod were evaluated to quantify the regional urban background and local-scale contributions to PM2.5 at that monitoring location. This method found that approximately 20% of the PM2.5 was attributed to local sources at this location, compared to 9% at a local regulatory monitoring site. Additionally, the 1-min data were combined with 1-min wind speed and wind direction data to examine potential sources in the area using the nonparametric trajectory analysis (NTA) technique. This method geographically identified local source areas that contributed to the measured concentrations at the high reading sensor location throughout the course of the study.

High-elevation shrub-ring δ18O on the northern slope of the central Himalayas records summer (May–July) temperatures

The potential of shrub-ring oxygen isotopes (SRO) as a paleoclimatic proxy is not well demonstrated. In this study we explored the climate signals embedded in an SRO chronology from Saga, on the northern slope of the central Himalayas by correlation analysis with climate variables and comparison with tree-ring and/or ice-core δ18O records. The Saga SRO had significant and positive correlations with May–July temperatures in both local (r = 0.43) and moisture source areas (r = 0.49) during the period 1955–2015 (CE), while no significant correlations were found with hydroclimatic variables. It is also in good agreement with two tree-ring δ18O series from the southern slope of the central Himalayas, the source of moisture to the site. The temperature signals are further verified by an ice core δ18O record from the Tanggula Mountains on the central Tibetan Plateau. However, it shows little similarity with the nearest Himalayan ice core δ18O record from Dasuopu, demonstrating temperature signals of different seasons. This study suggests that SRO could be used as an acceptable climate proxy, like tree-ring and ice-core δ18O, to broaden the spatial extent of the paleoclimatic records network. However, we should be cautious when combining different proxies with climate signals of different seasons in paleoclimate studies.

Mineralogical Studies of Kerur Formation Badami Group, Kaladgi Basin, Karnataka

Abstract Heavy and clay mineral analysis is a significant tool to interpret the provenance and paleoclimate of sandstone in proterozoic intracratonic Kaladgi-Badami basin, southern India. The distributions of heavy minerals are more in lower conglomerate; at the depth of 162.35m, zircon is 9.01%, magnetite is 74.18% and ilmenite is 24.61%. The ZTR index is 97.02%. The lower part of the upper unit of core quartz arenite, at the depth of 70.55m shows the following distribution of heavy minerals; zircon 2.94%, magnetite 50.84% and ilmenite 35.71%. The ZTR index of the quartz arenite is 65.52%; moderately abundant heavy minerals are tourmaline, rutile, and garnet; less abundant mineral is zircon in the core. The clay deposits in the basal arenite unit starts from 187 to 171.45m. The X-ray diffraction patterns shows 75% of Illite at the depth of 187m and 181.4m, 40% of chlorite at the depth of 181.7m, 36.36% of monmorillonite and 25% of kaolinite at the depth of 183m but 36.36% at the depth of 177.1m. kaolinite peaks are identified only in two samples. The study reveals that intense weathering in humid climate was responsible for alteration of granitic source rocks in the formation of kaolinitic clays in an acidic environment. The ZTR index reflects that the Badami sediments have attained moderate to high mineralogical maturity. The inference made out of the assemblage of heavy minerals point out that the Badami sediments have been sourced mainly from granitic and metamorphic terrain with a broad drainage basin. In most sandstone and conglomerate, the average ZTR index is moderate but varies widely among samples; apparently local lithologic source area variations largely control these relatively unmodified heavy mineral assemblages.