bluuebunny/crossref_metadata_2025 huggingface dataset:
Community-based observations help interface Indigenous and local knowledge, scientific research, and education in response to rapid Arctic coastal change
Authors: Eicken Hajo , Danielsen Finn , Druckenmiller Matthew , Fidel Maryann , Hauser Donna , Iversen Lisbeth , Johnson Noor , Jones Joshua , Kaufman Mette , Lee Olivia , Pulsifer Peter , Sam Josephine-Mary
Published: March 2020

Arctic coastal sea-ice environments are undergoing some of the most rapid changes anywhere in the Arctic, with implications for coastal communities’ food security and infrastructure, marine ecosystems, and permafrost. We argue that responses to such rapid change are most effective when informed by Indigenous and local knowledge and local observations to provide understanding of relevant processes, their impacts, and potential adaptation options. Community-based observations in particular can help create an interface across which different forms of knowledge, scientific research, and formal and informal education can co-develop meaningful responses. Through a broader literature review and a series of workshops, we have identified principles that can aid in this process, which include matching observing program and community priorities, creating sufficient organizational support structures, and ensuring sustained community members’ commitment. Drawing on a set of interconnected examples from Arctic Alaska focused on changing sea-ice environments and their impacts on coastal communities, we illustrate how these approaches can be implemented to provide knowledge sharing resources and tools. Specifically, in the context of the Alaska Arctic Observatory and Knowledge Hub (A-OK), a group of Iñupiat ice and coastal marine ecosystem experts is working with sea-ice geophysicists, marine biologists, and others to track changes in coastal environments as well as the services that the ice cover provides to coastal communities. The co-development of an observing framework and a web-based searchable database of observations has provided an interface for exchange and an education resource. An annual survey of hunting trails across the shorefast ice cover in the community of Utqiaġvik serves to further illustrate how different, response-focused activities such as the tracking of ice hazards – increasingly a concern with loss of ice stability and shortening of the ice season – can be embedded within a community-based monitoring framework.
Multiyear variability of atmospheric processes and ice cover in the Laptev Sea since 1942 to 2019
Authors: Timofeeva Anna , Ivanov Vladimir , Yulin Alexander , Khotchenkov Stepan
Published: March 2020

The Laptev Sea is influenced by synoptic regions of the Atlantic-Eurasian sector of the Northern Hemisphere. Types of large-scale processes are consider according to the G. J. Vangengeim typization: West (W) circulation form, with dominating zonal transport of air masses, East (E) and meridional (C) circulation forms with opposite phases of geographic orientation in the troposphere of the anticyclones ridges axes, blocking the Western transfer of air masses and developing the meridional circulation at high and middle latitudes. The Laptev Sea ice extent at the end of the melting season has a strong interannual variability, the oscillations amplitude reaches 86%.

The paper considers analysis of long-term trends of the large-scale atmosphere processes realignment and multiyear variability of the air temperature and ice cover anomalies in the Laptev Sea. According to multiyear course of integral anomalies values four steady periods of homogeneous  tendency of climatic processes revealed and described for data series from 1942 to 2019 (air reconnaissance and satellite data).

The types of ice conditions development (severe, medium, mild) at the end of the melting season were determined for the entire series of observations. More than half of cases during 78 years are distinguished as medium type of ice conditions. The repeatability of severe and mild types is almost the same numerically but varies in time according to revealed periods.

During 1942-1947 years in the Laptev Sea the “warming” period occurred (same for the whole polar region), known as the warming of the Arctic of 30th. At this period positive temperature anomalies and negative anomalies of sea ice extent (mean -2%) were dominated. During subsequent period 1948-1989 years the positive temperature trend has changed to the steady negative. The most dramatic temperature drops were observed in the 60-70th. Positive ice anomalies increased (mean 9%), in August Laptev Sea remained mostly covered by ice. Of the 42 years 28 refer to the medium type of ice conditions, 11 to the severe. During the period 1990-2004 years frequent interannual rearrangements of the atmosphere circulation and multidirectional fluctuations of temperature and ice cover anomalies were observed. On average, the temperature and ice cover during the period are close to the long-term norm. After 2005 temperature regime in the polar climate system has changed. This period is the warmest for the whole observations series in the Laptev Sea. Ice extent at the end of the melting season steady decreases and shows dramatic growth of negative anomalies values and occur of extremely low anomaly for the entire observation period (up to -54-55%). The average negative ice anomaly for the period is -26.4 %. Of the 15 years 9 refer to the mild type of ice conditions.
A comparative study of the adsorption efficiency of typical adsorption materials for wastewater containing cesium
Authors: Du Can , Wang Jinsheng , Liu Xin , Niu Juanting
Published: March 2020

In this paper, six typical adsorption materials (activated carbon, kaolin, montmorillonite, bentonite, zeolite, and attapulgite) were used to investigate the effects of adsorption time, initial concentration, pH, and temperature on the adsorption of cesium (Cs) contained in wastewater. A combination of kinetics and isotherms was used. The results revealed that, for the same adsorption time, the adsorption efficiencies of the six materials for Cs were as follows: zeolite>attapulgite>bentonite>montmorillonite>activated carbon>kaolin. The adsorption rate of zeolite to Cs ions was almost independent of the initial concentration and temperature. The removal effect of other materials improved in alkaline environments at 30℃. Attapulgite, montmorillonite, activated carbon, and kaolin could be used for the removal of Cs at low initial concentrations. The adsorptive processes utilized by the six adsorption materials were the result of a combination of various adsorption mechanisms. Among the six typical adsorption materials, zeolite, attapulgite, and bentonite had clear removal effects and could be used in practical application in which radioactive wastewater containing Cs needs to be disposed of. Our results suggest that zeolite is the best adsorption material for this purpose.
Thermal dissociation cavity enhanced absorption spectrometer for detecting ANs and PNs in the atmosphere
Authors: Li Chunmeng , Lu Keding , Wang Haichao , Chen Xiaorui , Zhai Tianyu , Chen Shiyi , Li Xin , Zeng Limin
Published: March 2020

We have developed a thermal dissociation cavity enhanced absorption spectroscopy (TD-CEAS) for in situ measurement of NO2, total peroxy nitrates (PNs) and total alkyl nitrates (ANs) in the atmosphere. The instrument uses one optical cavity for measuring NO2 absorption at 435 - 455 nm. Three channels with heating modules are set before the detecting cell in parallel, for measuring ANs, PNs and NO2 by stabilizing the temperature of 653 K, 453 K and normal, respectively. Three-channel cycle measurement is realized by dynamic switching design with the cycle time of 3 min, by assuming the air mass change is negligible when measuring on adjacent channels in each cycle. Therefore, the instrument is feasible in relative stable air masses, such as the chamber studies or field campaigns away from the emission source regions. The limit of detection (LOD) is estimated to be 97 pptv (1σ) at 6 s intervals for NO2. The measurement uncertainty of NO2 is estimated to be 8%, which mainly originates from effective cavity length, mirror reflectivity, and NO2 absorption cross section. The uncertainty of PNs and ANs measurement should be enlarged due to the sampling loss and the thermal dissociation efficiency. This instrument had been successfully applied in a field observation in China. Up to 3 ppbv PNs and ANs were observed during ozone pollution episodes. The inter-comparison of NO2 with that measured by PL-CLD, as well as PNs with that measured by GC-ECD will be presented. 
Atmospheric Dynamics Footprint on the January 2016 Ice Sheet Melting in West Antarctica
Authors: Hu Xiaoming , Sejas Sergio , Cai Ming , Li Zhenning , Yang Song
Published: March 2020

In January of 2016, the Ross Sea sector of the West Antarctic Ice Sheet experienced a three-week long melting episode. Here we quantify the association of the large-extent and long-lasting melting event with the enhancement of the downward longwave (LW) radiative fluxes at the surface due to water vapor, cloud, and atmospheric dynamic feedbacks using the ERA-Interim dataset. The abnormally long-lasting temporal surges of atmospheric moisture, warm air, and low clouds increase the downward LW radiative energy flux at the surface during the massive ice-melting period. The concurrent timing and spatial overlap between poleward wind anomalies and positive downward LW radiative surface energy flux anomalies due to warmer air temperature provides direct evidence that warm air advection from lower latitudes to West Antarctica causes the rapid long-lasting warming and vast ice mass loss in January of 2016.
Temporal heterogeneity affects the process of succession but not its direction in abandoned croplands in a semi-arid area of northwest China
Authors: Hou Fujiang , Hu An , Chang Shenghua , Chen Xianjiang
Published: March 2020

Spatial heterogeneity has been widely used in the study of succession in abandoned croplands worldwide, and it is often accompanied by time heterogeneity. However, the effect of temporal heterogeneity on succession dynamics over decades is not well understood. Here, we used croplands with same history in northwest China that were abandoned in 1998, 1999, and 2000 and continuously monitored vegetation characteristics for ten years. Croplands were left undisturbed throughout the study. Non-metric multidimensional scaling was used to interpret changes in the plant community, and taxonomic and functional diversity measures were compared in three treatment over time. Our results show that the directions of succession in all three croplands were similar, from single superior community (Salsolacollina Pall.) with higher aboveground biomass to multi-superior community (Artemisia capillaris Thunb., Stipa bungeana Trin., Lespedeza davurica (Laxm.) Schindl, Heteropappus altaicus (Willd.) Novopokr) with lower aboveground biomass. Taxonomic and functional diversity increased rapidly in the first 4–6 years, followed by a slow increase, decrease or stabilization. Temporal heterogeneity had no effect on species richness after the 7th year, on the Shannon-Wiener index, species evenness, modified functional attribute diversity, or functional divergence after the 8th year, or functional evenness after 5th year. We conclude that temporal heterogeneity can affect the process of secondary succession but has no effect on the direction of community succession. Our findings provide evidence for using temporal heterogeneity to study succession in abandoned croplands in semi-arid areas. 
Hydroacoustic measurements of the 2004 submarine eruption near Nightingale Island, Tristan da Cunha
Authors: Metz Dirk , Grevemeyer Ingo , Jegen Marion , Geissler Wolfram , Vergoz Julien
Published: March 2020

Little is known about active volcanism in the remote regions of the global ocean. Here, we resort to long‐range acoustic measurements to study the July/August 2004 eruption at Isolde, a submarine volcanic cone in the Tristan da Cunha archipelago, South Atlantic Ocean. Underwater sound phases associated with the event were recorded as far as Cape Leeuwin, Western Australia, where a bottom-moored hydrophone array is operated as part of the International Monitoring System (IMS). IMS hydrophone data in combination with local seismic observations suggest that the center of activity is located east of Nightingale Island, where a recent seafloor mapping campaign aboard R/V Maria S Merian (MSM20/2) has revealed a previously unknown, potentially newly formed stratocone. Transmission loss modeling via the parabolic equation approach indicates that low-frequency sound phases travel at shallow depths near and within the Antarctic Circumpolar Current, thereby avoiding bathymetric interference along the 10,265 km source-receiver path. Our study highlights the potential of the IMS network for the detection and study of future eruptions both at Isolde and elsewhere. Implications for test-ban treaty monitoring and volcano early warning will be discussed.
Interannual variability of the Eastern Indian Ocean with focus on the Ningaloo Niño and negative Indian Ocean Dipole event in 2010/2011
Authors: Ryan Svenja , Ummenhofer Caroline , Gawarkiewicz Glen , Wagner Patrick , Scheinert Markus , Biastoch Arne , Böning Claus
Published: March 2020

The dominant mode of sea surface temperature (SST) variability in the southeast Indian Ocean off the coast of Western Australia is called Ningaloo Niño/Niña. An unprecedented Ningaloo Niño, or marine heatwave, occurred during the austral summer of 2010/2011 with mean SSTs at 3°C above the long-term mean and had drastic impacts on the ecosystem. This event was attributed to a combination of an anomalous strong Leeuwin Current and high local air-sea heat fluxes. A number of local and remote forcing mechanisms have been investigated in recent years, however, little is known about the depth-structure of these ocean extremes and their general connections to large-scale ocean interannual to decadal variability. Using a suite of simulations with a high-resolution global Ocean General Circulation Model from 1958-2016, we investigate eastern Indian Ocean variability with focus on Ningaloo Niño and corresponding cold Ningaloo Niña events. In particular, we are interested in the impacts of large-scale ocean and climate variability, such as the Indonesian Throughflow, El Niño - Southern Oscillation and the Indian Ocean Dipole (IOD), on the study region. Spatial composites reveal large-scale surface and subsurface anomalies that extend from the western Pacific across the Indonesian Archipelago into the tropical eastern Indian Ocean. In particular, strong anomalies in temperature, salinity and mixed layer depth are found to the west of Sumatra and Java, a region that is generally strongly impacted by the IOD. We therefore investigate the connection with Ningaloo Niño/Niña events, at surface and subsurface, with a focus on 2010/2011 where a strong negative IOD event occurred prior to the unprecedented Ningaloo Niño. Furthermore, we find that major heatwaves in 2000 and 2011 are associated with pronounced fresh anomalies. Sensitivity experiments allow us to assess the relative role of buoyancy and wind-forcing as drivers of the observed patterns. Our work can provide valuable contributions for advancing the understanding of Ningaloo Niño/Niña drivers from surface to depth and regional to large scales.
Population aging might mask the health benefit from China’s 2013 Clean Air Action
Authors: Liu Yifan , He Xiaojing , Zhao Zixiao , Zhu Ge , Sabel Clive , Ma Zongwei , Jiao Ziheng , Zhao Jing , Wang Haikun
Published: March 2020

Ambient PM2.5 (fine particulate matter) pollution in China has been greatly reduced in recent years, especially since the implementation of Clean Air Action in 2013. Analysis of variations in the pollution related health burden and the driving factors has important implications for the policymakers to further improve the health benefit of air pollution controls. Here we adopted an annual population distribution estimate, disaggregated by age structure, together with PM2.5 concentration and incidence data, to better estimate total PM2.5 attributable mortality considering the effect of changing population size and age structure. We then quantified the contribution of each factor to the total variation of PM2.5 attributable mortality both nationally and regionally. Our analysis showed that national PM2.5 attributable mortality generally increased from 861,140 (95% confidence interval: 525,860~1,161,550) in 2004 to 932,500 (546,590~1,300,160) in 2017. In most 2nd- and higher-tier cities in China, which stand for highly developed cities like Beijing, Shanghai, Guangzhou, etc., the PM2.5 health burden increased. Meanwhile, the decrease in city-level PM2.5 health burden mainly happened in 3rd- and lower-tier cities, where local developments were relatively smaller. The effect of exposure to PM2.5 on air pollution-related mortality has altered from aggravating to mitigating since 2012, and the abated PM2.5 exposure resulted in a reduction of 19.7% of PM2.5 attributable mortality between 2012 and 2017. However, such benefit was almost masked by the effect of the population aging, which brought an increase of 18.4% to the health burden. Our results implied that the increasing trend in China’s PM2.5 health burden since 2006 was halted after 2012 due to the pollution control policies, and population aging impeded it from declining further. For future air pollution control and public health affairs, growing cities in China should focus attention on old-age care, where the growth of attributable mortality might occur.
Structure of the crust and upper mantle beneath the Bransfield Strait (Antarctica) using P-wave Receiver Functions
Authors: Parera-Portell Joan Antoni , Mancilla Flor de Lis , Morales José , Almendros Javier
Published: March 2020

The Bransfield Strait is a tectonically active region located between the South Shetland archipelago (SSI) and the Antarctic Peninsula (AP), characterised by the presence of an incipient back-arc spreading ridge driven by on-going slab rollback of the Phoenix plate under the Antarctic and Shetland plates. Twelve broad-band seismic stations deployed in the region are used to obtain P-wave receiver functions from teleseismic earthquakes to improve the current understanding of the crust and upper mantle structures. This includes the depth and spatial variability of the Moho discontinuity, the average crustal Vp/Vs ratio and the thickness of the Mantle Transition Zone (MTZ). Results reveal a highly variable crustal thickness in the South Shetland block, ranging from ~30 km near the SW and NE ends of the South Shetland Trench to ~15 km in the central Bransfield Basin (Deception Island), where the highest Vp ⁄ Vs ratios in the region are reached (> 2). In contrast, the AP displays typical and homogeneous continental crust characteristics with an average crustal thickness of ~34 km and Vp/Vs ~1.77. A low velocity zone (LVZ) is identified under all stations suggesting partial melting in the upper mantle beneath the lithosphere, which is widespread throughout the region and not only confined to the mantle wedge above the subducted Phoenix oceanic slab. There is evidence of magmatic underplating under the SSB in accordance with the LVZ together with the active volcanism and the high crustal Vp/Vs ratio in the area. The Phoenix oceanic slab is inferred to subduct steeply, as the MTZ appears already thickened under the AP.
From Rodinia to Pangea: an extroversion process driven first by plume push followed by downwelling pull, absorption and merging
Authors: Li Zheng-Xiang , Collins William , Wu Lei , Pisarevsky Sergei
Published: March 2020

Numerous works also suggested that mantle plumes or mantle upwellings associated with LLSVPs in a degree-2 mantle state play a major role in driving the break-up of a supercontinent. However, subduction and mantle downwelling may play an increasing role in the leadup to the assembly of the next supercontinent. Anderson (1994) noticed that continents tend to gather at mantle downwelling zones, which was later developed into the hypothesis of orthoversion assembly of supercontinents by Mitchell (2012). Zhong et al. (2007) conceptualised the assembly of supercontinents through the merger or absorption of mantle downwellings, leading to the assembly of supercontinents over a superdownwelling in a degree-1 mantle. Here we present a revised global paleogeographic reconstruction featuring an extroversion assembly of Pangea (i.e. through the closure of the Mirovoi superocean) over a pre-existing yet dynamic mantle downwelling zone (Li et al., 2019). In particular, we show that the Paleozoic world was dominated by two major subduction (dowelling) cells, one associated with the newly assembled Gondwana, and the other associated with the assembly of Laurasia. The two cells gradually merged together by the Carboniferous time, forming the supercontinent Pangea over a mantle superdownwelling (Zhang et al., 2010). It was during the merger of the two dowelling cells that continental and arc terranes was successively transported from Gondwana margin to future Laurasia.

References:

Anderson, D.L., 1994. Superplume or supercontinents? Geology 22, 39-42.

Huang, C., Zhang, N., Li, Z.-X., Ding, M., Dang, Z., Pourteau, A., Zhong, S., 2019. Modeling the Inception of Supercontinent Breakup: Stress State and the Importance of Orogens. Geochemistry, Geophysics, Geosystems 20, 4830-4848.

Li, Z.X., Mitchell, R.N., Spencer, C.J., Ernst, R., Pisarevsky, S., Kirscher, U., Murphy, J.B., 2019. Decoding Earth’s rhythms: Modulation of supercontinent cycles by longer superocean episodes. Precambrian Research 323, 1-5.

Mitchell, R.N., Kilian, T.M., Evans, D.A.D., 2012. Supercontinent cycles and the calculation of absolute palaeolongitude in deep time. Nature 482, 208-211.

Zhang, N., Zhong, S., Leng, W., Li, Z.-X., 2010. A model for the evolution of the Earth's mantle structure since the Early Paleozoic. Journal of Geophysical Research: Solid Earth 115, B06401.

Zhong, S., Zhang, N., Li, Z.-X., Roberts, J.H., 2007. Supercontinent cycles, true polar wander, and very long-wavelength mantle convection. Earth and Planetary Science Letters 261, 551-564.
Characterising hydrodynamic controls on groundwater in a coastal urban aquifer using time and frequency domain responses at multiple spatiotemporal scales
Authors: Patton Ashley M , Rau Gabriel C , Abesser Corinna , James David R , Cleall Peter J , Cuthbert Mark O
Published: March 2020

Urban environments often have highly variable and evolving hydrogeology. Coastal cities present even greater challenges to hydraulic and thermal conceptualisation and parameter estimation due to their complex dynamics and the heterogeneity of ocean-influenced hydraulic processes. Traditional methods of investigation (e.g. pump tests, invasive sampling) are time consuming, expensive, represent a snapshot in time and are difficult to conduct in built-up areas, yet properties derived from them are crucial for constructing models and forecasting urban groundwater evolution.

Here we present a novel approach to use passive sampling of groundwater head data to understand subsurface processes and derive hydraulic and geotechnical properties in an urban-coastal setting. This is illustrated using twenty years of high frequency (hourly) time-series data from an existing groundwater monitoring network comprising 234 boreholes distributed across Cardiff, the capital city of Wales, UK. We have applied Tidal Subsurface Analysis (TSA) to Earth, Atmospheric and Oceanic signals in groundwater time-series in the frequency domain, and also generated Barometric Response Functions in the time domain. By also observing the damping and attenuation of the response to ocean tides with distance from the coast and tidal rivers, this combination of analyses has enabled us to disentangle the influence of the different tidal components and estimate spatially distributed aquifer processes and parameters.

The data cover a period pre and post construction of a barrage across the coastline, impounding the city’s rivers. We were therefore able to observe a huge decrease in the subsurface ocean tide signal propagation following this human intervention, through the coastal and tidal river boundaries. These changes reveal variations in hydraulic responses and values of hydraulic diffusivity between different lithologies, notably with made-ground deposits being much less sensitive to ocean tides than the underlying sand and gravel aquifer. By being able to map the spatial variations in hydraulic response and barometric efficiency for the first time (and therefore formation compressibility and extent of aquifer confinement) we have been able to refine interpretations (and in some cases overcome misconceptions) derived from previous inferences made solely from borehole logs. We anticipate that linking the improved hydraulic characterisation, enabled by the new methodology, will also help better characterisation of the subsurface thermal regime, and management of shallow geothermal energy resources in coastal urban aquifers.
Ice nucleation by black carbon particles in the cirrus regime: dominated by pore condensation and freezing or deposition ice nucleation?
Authors: Zhang Cuiqi , Zhang Yue , Wolf Martin , Chen Longfei , Cziczo Daniel
Published: March 2020

Deposition ice nucleation (IN) is a heterogeneous pathway by which water vapor deposits directly onto a solid surface and forms ice. Deposition IN happens below water saturation. However, the pore condensation and freezing (PCF) mechanism offers another explanation to ice formation on porous particles at low ice supersaturation. A single black carbon (BC) aggregate consists of several primary particles, forming crevices between primary particles. Whether BC IN happens via deposition or PCF remains uncertain due to the fractal nature of BC particles.

We estimated aggregate surface area, morphology, and primary particle size distribution directly from scanning electron microscopy (SEM) images of size-selected (200 nm, 300 nm, and 400 nm) commercial BC particles. Correlations between surface area data obtained from SEM image estimation and traditional BET tests were explored. Several shape parameters were chosen to characterize particle morphology. The IN ability of aerosolized BC particles was determined with the Spectrometer for Ice Nuclei (SPIN) in the cirrus regime (-46 to -38°C). Particle number concentration and chemical composition were monitored online by a Condensation Particle Counter (CPC) and the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument, respectively.

Preliminary experimental results suggest that larger (400 nm) BC particles are more fractal and branching compared with smaller (200-300 nm) particles. Larger, more fractal BC particles are superior ice nucleating particles (INP) when compared with smaller, more spherical ones. The primary particle size distribution of all samples peaks around 30-45 nm. To understand the relevance of the PCF mechanism with our experimental IN results, we established Young-Laplace equations for the potential liquid-vapor interfaces within inter-primary particle crevices and pores and inter-aggregate pores. Solutions of the Young-Laplace equation on a saddle surface was deducted. Whether ice nucleation happens via PCF mechanism or deposition still requires further investigation, since particle surface chemistry can also affect both ice formation pathways.
Influence of Check Dams on Flood and Erosion Dynamic Processes of a Small Watershed in the Loss Plateau
Authors: Yuan Shuilong , Xu Guoce , Shi Peng , Lu Kexin
Published: March 2020

As an important soil and water conservation engineering measure, check dams have been constructed on a large scale in the Loess Plateau of China. However, their effects on runoff and sediment processes in the basin are still unclear. In this study, the hydrodynamic processes of the Wangmaogou watershed located in the Loess Plateau were simulated, and the influence of check dams on the flood and erosion dynamic processes in this watershed were also evaluated. The results showed that the check dams obviously reduced the flood peak and flood volume and mitigated the flood process. After the dam system was completed, the flood peak and flood volume were reduced by 65.34% and 58.67%, respectively. The erosion dynamic distribution of the main channel in the small watershed was changed to different extents by the different dam type combinations, and the erosion dynamic parameters of the channel decreased most after the dam system was completed, when the velocity and runoff shear stress of the outlet section were reduced by 10.69% and 31.08%, respectively. Additionally, the benefits of sediment reduction were most obvious after the check dam system was completed, with the sediment discharge in the watershed being reduced by 83.92%. The results of this study would provide specific implications for construction and management of check dams in the Loess plateau.
Feasibility of using environmental covariates and machine learning to predict the spatial variability of selected heavy metals in soils
Authors: Zeraatpisheh Mojtaba , Mirzaei Rouhollah , Garosi Younes , Xu Ming , Heuvelink Gerard B.M. , Scholten Thomas , Taghizadeh-Mehrjardi Ruhollah
Published: March 2020

Heavy metal contamination in soil is a major environmental issue intensified by rapid industrial and population growth. Understanding the spatial distribution of soil contamination by heavy metals in the ecosystem is a necessary precondition to monitor soil health and to assess the ecological risks. The main sources of heavy metals in soil are natural and anthropogenic sources. Natural sources are typically released of heavy metals from rock by weathering and atmospheric precipitation. Anthropogenic sources are related to industrialization, rapid urbanization, agricultural practices, and military activities. We analyzed a total of 358 topsoil samples (0–30 cm) collected in Golestan province in the northeast of Iran based on a regular square grid networks with 1,700 squares each sized 2.5 km²(random sampling within the grid). From these samples, we determined the spatial distribution of Cd, Cu, Ni, Zn, and Pb using random forest (RF). A multi-spectral image (Landsat 8), and environmental derivatives calculated from terrain attributes, climatic parameters, parent material, land use maps, distances to mine sectors, main roads, industrial sites, and rivers were used as covariates to predict the spatial distribution of concentrations of heavy metals. The multi-collinearity of the predictors was examined by the variance inflation factor (VIF), and a feature selection process (genetic algorithm) was applied to avoid noise and optimize the selected input variables for the final model. The predictive accuracy of RF model was assessed by the mean prediction error (ME), root mean squared error (RMSE), and coefficient of determination (R2) using 5-fold cross-validation technique. The results showed that the concentration levels (mg kg-1) of Cd, Cu, Pb, Ni, and Zn varied from 0.02 to 2.75, 9.70 to 93.70, 6.80 to 114.20, 9.50 to 93.20, and 25.10 to 417.4, respectively. The best prediction performance was for Ni (RMSE=9.9 mg kg-1 and R2=56.6%), and the lowest prediction performance for Cd (RMSE=0.4 mg kg-1 and R2=28.0%). Environmental covariates that control soil moisture and water flow along with climatic factors were the most important variables to define the spatial distribution of soil heavy metals. We conclude that the RF model using easily accessible environmental covariates is a promising, cost-effective and fast approach to monitor the spatial distribution of heavy metal contamination in soils.

Keywords: Heavy metals; digital soil mapping; machine learning; random forest; spatial variation; soil pollution.
Long-term (1870-2018) drought reconstruction in India
Authors: Mishra Vimal
Published: March 2020

Droughts in India affect food production, gross domestic product (GDP), livelihood, and socio-economic condition of a large population associated with agriculture. Recent drought (2015-2018) caused groundwater depletion and affected about one-fourth of the Indian population. However, it remains unclear if the drought of 2015-2018 was among the most severe droughts that occurred in India. Here we use a long-term (1870-2018) data to identify the top five ("deadly") meteorological/hydrological droughts based on overall severity score in the last century and half period. Out of a total of 18 meteorological droughts, the deadly droughts occurred in 1899, 1876, 2000, 1918, and 1965. Similarly, the deadly hydrological droughts occurred in 1899, 2000, 1876, 1965, and 1918 during 1870-2018. All the five deadly droughts were associated with the positive phase of El Nino Southern Oscillations (ENSO). Results show that the relationship between ENSO and monsoon (June to September) precipitation in India has weakened while the role of Indian and Atlantic Oceans has strengthened during the recent decades. Notwithstanding the longest (41 months) duration, the 2015-2018 drought did not feature among the deadly droughts. The 2015-2018 drought affected surface (reservoir storage) and groundwater availability in both southern and northern parts of India and was linked to El-Nino and Indian Ocean Dipole. Droughts and rapidly declining groundwater together can pose serious challenge to ensure fresh water security in India.
GAGE Facility Geodetic Data Archive: Discoverability, Accessibility, Interoperability & Attribution
Authors: Riley James , Meertens Charles , Mencin David , Hodgkinson Kathleen , Ertz Douglas , Maggert David , Reiner Dan , Crosby Christopher , Baker Scott
Published: March 2020

The U.S. National Science Foundation’s Geodesy Advancing Geosciences (GAGE) Facility, operated by UNAVCO, is building systems and adopting practices in support of more comprehensive data discovery, search and access capabilities across our various geodetic data holdings. As a World Data Center, the GAGE Facility recognizes the need for interoperability of its Earth data holdings in its archives, as represented by the FAIR Data Principles. To this end, web services, both as back-end and front-end resources, are being developed to provide new and enhanced capabilities. 

UNAVCO is exploring international standards such as ISO Geographic information Metadata and the Open Geospatial Consortium’s (OGC) web services that have been in development for decades to help facilitate interoperability. Through various collaborations, UNAVCO seeks to develop and promote infrastructure, metadata, and interoperability standards for the community. We are participating in the development of the next version of GeodesyML, being led by Geoscience Australia, which will leverage standards and help codify metadata practices for the geodetic community. New web technologies like Linked Data, are arising to augment these standards and provide greater connectivity and interoperability of structured data and UNAVCO has implemented Schema.org metadata for its datasets and partnered with EarthCube’s Project 418/419 and Google Dataset Search. Persistent identifiers are being adopted with DOI’s for datasets and exploration into RORs for organizational affiliation, and ORCID iDs for identity and access management and usage metrics are being explored. As UNAVCO investigates these various technologies and practices, they remain in various states of acceptance and implementation, we share our experiences to date.
Reference Scenarios for Bioproduct Assessments: soil carbon and standardized reference scenarios
Authors: Davis Maggie
Published: March 2020

Assumed effects on land attributes have important implications for nearly all aspects of social, environmental and economic sustainability as well as policy designed to enhance sustainable agriculture. Life-cycle assessments, technical-economic assessments, and sustainability assessments of agriculture and bioproduct industries often use computational models to contribute to an understanding of complex processes. However, because the impacts attributed to a specific process or product must be interpreted in terms of a “business as usual” case, the reference scenario is a key factor in interpreting assessment results. Further, predictions of change are not equivalent to knowledge or data from empirical studies and instead can reflect underlying assumptions and embedded uncertainty from large input datasets. For example, in estimating soil organic carbon (SOC) dynamics, there is no internationally agreed SOC measurement protocol. This complicates the establishment of baseline scenarios for comparison across industries and continents (e.g. Brazil and the US: two of the largest bioproduct producers who often trade in equivalent products). If these models are used to accurately predict change and to justify the sustainability of a product, the reference scenario assumptions need to be realistic, measurable, and clearly documented. Justification for assumptions or simplifications should be based on published data and research that employs scientific principles and best available practices for measurement. We will present the results of a systematic literature review to determine the degree to which reference scenarios are explicitly defined when the effects of bioproducts are assessed; and to identify any published guidelines or rules for defining appropriate reference scenarios when assessing bioproducts. We will also present a summary of key aspects of a reference scenario and show the application of these principles to develop a SOC baseline for bioproduct assessments.
On the role of flocculation, hindered settling and sediment-induced damping of turbulence in trapping sediment in estuaries, with focus on the North Passage, Yangtze Estuary
Authors: Jiang Chenjuan , de Swart Huib E. , Zhou Jianan , Li Jiufa
Published: March 2020

Many estuaries are characterized by one or more locations where the concentration of fine sediment attains a maximum. The locations and intensities of these estuarine turbidity maxima (ETM) are sensitive to river discharge, tides, depth and sediment properties. In this contribution, results are presented of a width-averaged process-based model that describes tides, residual currents and sediment transport in an estuarine channel. The aim is to quantify the sensitivity of location and intensity of ETM to 1) flocculation and hindered settling of fine sediment and 2) sediment-induced damping of turbulence. The model is applied to the North Passage of the Yangtze Estuary, which is a prototype estuary that undergoes strong variations in environmental conditions. The sediment settling velocity is allowed to vary along the channel due to the effects of flocculation and hindered settling, by parametrizing settling velocity as the function of the subtidal near-bed sediment concentration according to results obtained from laboratory experiments. Sediment-induced turbulence damping is taken into account by parametrizing eddy viscosity and eddy diffusivity coefficients as functions of bulk Richardson number.

In the flocculation (low concentration) regime, where the settling velocity increases with sediment concentration, the rapid settling of flocs induces larger landward sediment transport due to upstream flow in the lower layer of density-driven flow, leading to a landward shift and intensification of the ETM (with respect to the case of a constant settling velocity). In the hindered settling (high concentration) regime, the settling velocity decreases with bottom concentration. This induces a decrease in upstream sediment transport due to density-driven flow and an increase in seaward sediment transport due to river flow, leading to seaward migration and attenuation of the ETM. In both regimes, sediment-induced damping of turbulence results in stronger upstream flow in the bottom layer of density-driven flow and more vertically stratified sediment distribution, which significantly intensifies the landward sediment transport due to density driven flow, and hence causes a landward shift and intensification of the ETM.
U-Th Dating of Syntectonic Calcite Veins Reveals the Dynamic Nature of Fracture Cementation and Healing in Faults
Authors: Williams Randolph , Mozley Peter , Sharp Warren , Goodwin Laurel
Published: March 2020

Fracture cementation is an important control on the recovery of prefailure levels of permeability and strength in faults and reservoir rock. The timescales of this process, however, are almost entirely unknown from direct analysis of the rock record. We report U‐Th dating results that quantify rates of fracture cementation in syntectonic calcite veins from the Loma Blanca fault, New Mexico, USA. Measured cementation rates vary from ~0.05 to 0.80 mm/ka and exhibit a power function correlation with minimum fracture apertures. We argue that this correlation is the result of crystal growth in a transport‐limited system, where cementation rates were proportional to rates of fluid flow in individual fractures. We argue that such transport‐limited growth necessarily leads to a heterogeneous distribution of cementation rates as fluids migrate through fracture networks of variable and changing aperture. For this reason, individual fractures are not expected to seal at monotonic rates through time but could instead experience order‐of‐magnitude increases or decreases in sealing rate depending on their geometric properties (e.g., aperture, length/width, and orientation) and position within a continually evolving fracture network. We further argue that such transport‐limited, flux‐dependent cementation necessarily leads to a heterogeneous distribution of permeability and strength recovery as fluids migrate through fault‐zone fracture networks. These heterogeneities may influence rupture propagations pathways and the continual development of fault‐zone architecture/complexity.
Cooling and freshening of the eastern equatorial Pacific over the last 2000 years
Authors: Rustic Gerald , Koutavas Athanasios , Marchitto Thomas
Published: March 2020

Sea surface temperatures in the eastern equatorial Pacific exert powerful influence on the climate beyond the tropics through strong atmosphere-ocean coupling. Records of eastern Pacific sea surface temperatures are of vital importance for identifying the linkages between short-term climate variability and long-term climate trends. Here we reconstruct eastern equatorial Pacific sea surface temperature and salinity from paired trace metal and stable isotope analyses in foraminifera from a sediment core near the Galápagos Islands. Sea surface temperatures are correlated with reconstructed Northern and Southern hemisphere temperature records suggesting a common origin. We propose that this temperature signal originates in the extra-tropics and is transmitted to the eastern Pacific surface via its source waters. We find exceptions to this cooling during the Little Ice Age and during the last century, where notable sea surface temperature increases are observed. We calculate δ18Osw from paired stable isotope and trace element analyses and derive salinity, which reveals a significant trend toward fresher surface waters in the eastern equatorial Pacific. The overall trend toward cooler and fresher sea surface conditions is consistent with longer-term trends from both the Eastern and Western Pacific.
Plot-scale wash-off of Cesium-137 and Strontium-90 after three decades since the Chernobyl accident
Authors: Wakiyama Yoshifumi , Igarashi Yasunori , Onda Yuichi , Samoilov Dmitry , Lisovy Hlib , Demianovych Volodymyr , Laptev Gennady , Konoplev Alexei , Nanba Kenji , Kirieiev Serhii
Published: March 2020

Long-term behaviors of Cesium-137 (137Cs) and Strontium-90 (90Sr) have been of great interest in Chernobyl and its downstream area. This study presents plot-scale observations of 137Cs and 90Sr wash-off in the Chernobyl exclusion zone since 2018 to date. Runoff plots were established on a pine forest in the Kopachi area (PF-KP), an abandoned farmland in the Korogod area (AF-KR) and a post wild fire territory in the Red Forest (WF-RF) in December 2017. Each runoff plot consists of eroding surface of 22.13 m length and 5 m width, a 30° V-notch weir with water level sensor for monitoring surface runoff and tanks for collecting runoff water and sediments. Since February 2018, runoff water and sediment samples trapped in the weir and tanks have been collected after rainfall events and analyzed for particulate 137Cs concentration, dissolved 137Cs concentration, and dissolved 90Sr concentration. Analyses of samples in 2, 4, and 3 wash-off events were completed for PF-KP, AF-KR, and WF-RF, respectively. The ash/litter on soil surface, soil of 0-1 cm depth, soil of 1-2 cm depth, and soil of 2-3 cm depth were sampled with a scraper plate and subject to measurements of 137Cs and 90Sr concentrations.  Total volume of surface runoff from PF-KP, AF-KR, and WF-RF were 0.97, 0.73, and 3.2 mm, respectively. Total sediment discharge from PF-KP, AF-KR, and WF-RF were 0.29, 0.015, 1.7 g m-2, respectively. The runoff and sediment discharge from PF-KP and WF-RF were mainly observed in summer and attributed to severe water repellency of the surface soils. Total particulate 137Cs wash-off from PF-KP, AF-KR, and WF-RF were 51, 0.082, 270 Bq m-2, respectively. Total dissolved 137Cs wash-off from PF-KP, AF-KR, and WF-RF were 7.4, 0.024, 9.8 Bq m-2, respectively. Total dissolved 90Sr wash-off from PF-KP, AF-KR, and WF-RF were 55, 0.31, 230 Bq m-2, respectively.  These results indicate that wild fire enhances surface runoff and sediment yield and result in greater wash-off of 137Cs and 90Sr. In comparisons between PF-KP and WF-RF, apparent Kd value for 137Cs at WF-RF was higher than at PF-KP. Ratio of dissolved 137Cs and 90Sr concentration to those in ash/litter layer at PF-KP was lower than those of WF-RF. The dissolution of these radionuclides into runoff water appeared to be restrained in the post wild-fire site.
Scaling up the assessment of the SWOT discharge inversion algorithm to thousands of gauges globall
Authors: Lin Peirong , Pan Ming , Wood Eric , Feng Dongmei , Gleason Colin , Brinkerhoff Craig , Yang Xiao , Pavelsky Tamlin
Published: March 2020

One important goal of the Surface Water and Ocean Topography (SWOT) satellite mission is to estimate global river discharges from observations of river width, height, and slope. While a range of algorithms have been developed and intercompared for SWOT (e.g., Durand et al. 2016), our understanding of the algorithm accuracy has been confined to tens of rivers globally, due to the limited SWOT-like observations currently collected from hydraulic model outputs.

To scale up the assessment of SWOT discharge algorithms, this study will first collect discharge observations at thousands of global gauges whose river widths are wider than 50 m (i.e., observable by SWOT), to provide the most comprehensive observations to evaluate discharge estimations. Then at those gauges, all available Landsat images from 2010 to 2017 (8 years) will be collected to extract river widths with an automatic Google Earth Engine tool called RivWidthCloud (Yang et al. 2019). The extracted river width time series (temporally intermittent) will provide SWOT-like observations, which can be used to derive discharge using the Bayesian AMHG-Manning (BAM) algorithm (Hagemann et al. 2017; Feng et al. 2019). The prior discharge information needed by the BAM algorithm will come from an updated global discharge modeling database (Lin et al. 2019). These datasets, collectively, will provide a critical assessment of the SWOT discharge algorithms.

This study is expected to provide the first geographically explicit assessment of the BAM algorithm at thousands of global locations, and the insights gained may also help the global hydrologic modeling community with their data assimilation efforts.