Subsurface Samples Research Articles

Changes in particulate and mineral-associated organic carbon with land use in contrasting soils

Soil organic carbon (SOC) is the largest terrestrial carbon (C) stock, and the capacity of soils to preserve organic C (OC) varies with many factors, including land use, soil type, and soil depth. We investigated the effect of land use change on soil particulate organic matter (POM) and mineral-associated organic matter (MOM). Surface (0−10 cm) and subsurface (60−70 cm) samples were collected from paired sites (native and cropped) of four contrasting soils. Bulk soils were separated into POM and MOM fractions, which were analyzed for mineralogy, OC, nitrogen, isotopic signatures, and 14C. The POM fractions of surface soils were relatively unaffected by land use change, possibly because of the continuous input of crop residues, whereas the POM fractions in corresponding subsurface soils lost more OC. In surface soils, MOM fractions dominated by the oxides of iron and aluminum (oxide-OM) lost more OC than those dominated by phyllosilicates and quartz, which was attributed to diverse organic matter (OM) input and the extent of OC saturation limit of soils. In contrast, oxide-OM fractions were less affected than the other two MOM fractions in the subsurface soils, possibly due to OC protection via organo-mineral associations. The deviations in isotopic signature (linked with vegetation) across the fractions suggested that fresh crop residues constituted the bulk of OM in surface soils (supported by greater 14C). Increased isotopic signatures and lower 14C in subsurface MOM fractions suggested the association of more microbially processed, aged OC with oxide-OM fractions than with the other MOM fractions. The results reveal that the quantity and quality of OC after land use change is influenced by the nature of C input in surface soils and by mineral-organic association in subsurface soils.

Measurement of Sub-Surface Microstructures Based on a Developed Ultrasonic Atomic Force Microscopy

Accurate and non-destructive technology for detection of subsurface defect has become a key requirement with the emergence of various ultra-precision machining technologies and the application of ultra-precision components. The combination of acoustic technique for sub-surface detection and atomic force microscopy (AFM) for measurement with high resolution is a potential method for studying the subsurface structure of workpiece. For this purpose, contact-resonance AFM (CR-AFM) is a typical technique. In this paper, a CR-AFM system with a different principle from commercially available instruments is set up and used for the detection of sub-surface Si samples with grating structures and covered by different thickness of highly oriented pyrolytic graphite (HOPG). The influence of subsurface burial depth on the detection capability is studied by simulations and experiments. The thickest HOPG film allowing for sub-surface measurement by the proposed method is verified to be about 30 μm, which is much larger than the feature size of the subsurface microstructure. The manuscript introduces the difference between this subsurface topography measurement principle and the commercially available AFM measurement principle, and analyzes its advantages and disadvantages. The experimental results demonstrates that the technique has the capability to reveal sub-surface microstructures with relatively large buried depth and is potential for engineering application in ultra-precision technologies.

Mapping the possible origin of anomalous saline water occurrence in Agbabu, Eastern Dahomey Basin, Nigeria: insights from geophysical and hydrochemical methods

Many researchers have suspected saltwater occurrence in Agbabu in the eastern Dahomey Basin. However, there is a need to get an insight to the possible origin of saltwater in the area. The aim of this study is to determine the source of saltwater in the inland aquifers of Agbabu, southwestern Nigeria for proper management of scarcely available freshwater resource in the area. 23 vertical electrical sounding, 2D electrical resistivity tomography (ERT), aeromagnetic and hydrochemical data (11 subsurface water samples) analyses were utilized in this study. The results from the magnetic analysis revealed the inland extension of the Chain Fracture Zone (CFZ). This NE-SW trending fracture zone cuts across the entire eastern Dahomey Basin, including Agbabu and its environs. Four (4) geoelectric layers were delineated across Agbabu namely, the topsoil (4 - 2806 Ωm), clayey sand (3 - 1280 Ωm), clayey (3 - 161 Ωm) and bituminous sand (1 - 10390 Ωm) layers. Anomalously low resistivity (1 - 20 Ωm) zones suspected within the bituminous sand correspond to the saltwater intrusion zones. The bituminous sand unit harbouring freshwater exhibits characteristic resistivity values of 33 – 160 Ωm. The interface between the freshwater and saltwater intruded zones in the area was suspected at 10 m depth with resistivity values ranging between 21 Ωm and 33 Ωm. The results from the hydrochemical water analysis also confirmed the presence of saltwater intrusion in the area. The salinity extent chart which was generated from the VES results indicated the mobility of the saltwater into the groundwater system. The fracture connectivity between the complex aquifers of Agbabu and the Atlantic Ocean (CFZ), that was mapped from the aeromagnetic and electrical resistivity results, is suspected to be primarily controlling the localization of saltwater in the study area.

The significance of outcrop analog data for reservoir quality assessment: A comparative case study of Lower Triassic Buntsandstein sandstones in the Upper Rhine Graben

Subsurface reservoir quality assessments are among the most important workflows in reservoir geology. The application has been standard practice in the hydrocarbon industry and is also adopted for geothermal reservoir systems hosted in clastic rocks. With the emergence of fluid mining for metals, such as lithium for the energy transition, yet another field may adopt the standard practice. However, as drill cores and hard geological data from the subsurface are expensive commodities they may be substituted by outcrop analog studies to fill in data gaps in the understanding of the deep subsurface. However, reservoir quality controls, such as pore-filling cements or natural fractures may be altered or overprinted during uplift to the surface and exposure to undersaturated meteoric fluids and associated stress release. A complete understanding of geochemical and geomechanical processes affecting the rocks since their deposition is needed to account for that, otherwise data may not be representative of the subsurface. In this case study using petrographic (point-counting) and petrophysical (porosity and permeability) analyses we highlight the possibilities and limitations of outcrop analog data used for the evaluation of subsurface reservoir quality. The focus is on the Triassic Buntsandstein within the Upper Rhine Graben in southwestern Germany and eastern France and exposed outcrop analogs along the western margin of the graben. Here, we show that some data (detrital composition, quartz cement, K-feldspar cement, and clay mineral cement volumes) may directly be applicable to subsurface reservoir quality assessment. However, other data (porosity, permeability, IGV, carbonate cement, and iron hydroxide cement contents) cannot be used analogously to subsurface samples and we outline possible approaches to mitigate some of the mismatches in the frame of a reservoir quality study. In particular, the correction for uplift diagenetic dissolution of carbonate cemented nodules and goethite precipitation will be the key to gain more accurate results in the presented area.

Evaluation of environmental radioactivity in soils around a coal burning power plant and a coal mining area in Barapukuria, Bangladesh: Radiological risks assessment

To study the distributions and potential dispersions of naturally occurring radioactive materials (NORMs: 226Ra, 232Th, and 40K) from coal-based activities (Barapukuria, Bangladesh), we studied a suite of systematically collected surface and sub-surface soil samples by X-ray fluorescence and high purity germanium detector based γ-spectroscopy. The average (range) radioactivities of 226Ra, 232Th, and 40K in the studied soil samples were 80.6 (33.0–118.0), 104.4 (43.0–182.0), and 508.1 (318.3–743.4) Bq.kg−1, respectively, which are significantly higher than the corresponding world average value. No significant fractionations of NORMs were observed between the surface and sub-surface soils, except for 232Th. Along with the anthropogenic origin, several geochemical processes (e.g., weathering, mineralogical dissolution/precipitation, alteration, leaching, differential solubility mediated geochemical mobility etc.) play significant role in NORM distributions. Major-oxide abundances, indices-based calculations, and correlation studies on the measured parameters revealed the natural processes (e.g., geochemical mobility, mineralogical distributions, water logging based differential solubility) responsible for NORM distributions. In terms of mean radium equivalent activity, internal hazard index, and total annual effective dose values, the studied area possesses trivial radiological risks, whereas the values of internal absorbed gamma dose and excess lifetime cancer risk demonstrate significant health hazards. Considering the adverse radiological risks originating from coal-based industrial activities and the long half-lives of NORMs, the present scenario will potentially be deteriorated.

A Comprehensive Network Integrating Signature Microbes and Crucial Soil Properties During Early Biological Soil Crust Formation on Tropical Reef Islands.

Biological soil crusts (BSCs/biocrusts), which are distributed across various climatic zones and well-studied in terrestrial drylands, harbor polyextremotolerant microbial topsoil communities and provide ecological service for local and global ecosystem. Here, we evaluated BSCs in the tropical reef islands of the South China Sea. Specifically, we collected 41 BSCs, subsurface, and bare soil samples from the Xisha and Nansha Archipelagos. High-throughput amplicon sequencing was performed to analyze the bacterial, fungal, and archaeal compositions of these samples. Physicochemical measurement and enzyme activity assays were conducted to characterize the soil properties. Advanced computational analysis revealed 47 biocrust-specific microbes and 10 biocrust-specific soil properties, as well as their correlations in BSC microbial community. We highlighted the previously underestimated impact of manganese on fungal community regulation and BSC formation. We provide comprehensive insight into BSC formation networks on tropical reef islands and established a foundation for BSC-directed environmental restoration.

Bacteria Community Vertical Distribution and Its Response Characteristics to Waste Degradation Degree in a Closed Landfill

The diversity, community structure and vertical distribution characteristics of bacteria in the surface and subsurface soil and water samples of a closed landfill in Shanghai Jiading District were investigated to reveal the relationships between natural waste degradation degree and the succession of bacterial community composition. High-throughput sequencing of bacteria 16S rDNA genes was used to analyze the bacterial community structure and diversity. The results showed that the diversity of bacteria in the surface samples was higher than that in the deep samples. Proteobacteria was the dominant phylum in all the samples, and the percentage increased with depth. At the genus level, Thiobacillus, Pseudomonas, Aquabacterium, and Hydrogenophaga were the dominant genera in surface, medium, deep and ultra-deep soils, respectively. The Bray–Curtis dissimilarity of the soil bacterial communities in the same layer was small, indicating that the community composition of the samples in the same layer was similar. The RDA result showed that ammonium, nitrate, pH and C/N significantly influenced the community structure of soil bacteria. This is of great relevance to understand the effect of natural waste degradation on bacterial communities in closed landfills.

Bacterial sources and cycling dynamics of amino acids in high and low molecular weight dissolved organic nitrogen in the ocean

Amino acids (AA) represent the most abundant identifiable biomolecule class in marine dissolved organic nitrogen (DON) and provide powerful proxies for DON degradation state. In particular, the D-enantiomers of AA (D-AA) are known to be derived mainly from bacteria, making them ideal tracers for bacterially derived N. However, despite the widespread use of D-AA tracers, it remains unclear if the accumulation of different D-AA species in the ocean indicates that most DON arises from direct bacterial sources or from continual bacterial alteration of eukaryotic algal material. This difference has major implications for our understanding of sources and cycling mechanisms of DON in the ocean. Here, we present the most extensive D-AA suite ever reported in younger, high molecular weight (HMW) DON contrasted with older, low molecular weight (LMW) solid phase extracted (SPE) DON from the central Atlantic and Pacific Oceans. We evaluate D-AA in these two contrasted MW fractions in the context of multiple common AA-based proxies and bulk DOM radiocarbon (Δ14C) data. Specifically, we assess if D-AA in HMW and LMW SPE-DON are most consistent with 1) preformed bacterial source signals, 2) progressive bacterial degradation/alteration of eukaryotic algal sources, or 3) gradual, continued resynthesis/addition of new bacterial biomolecules during ocean circulation. Our results suggest that AA-containing molecules in HMW and LMW SPE-DON fractions are almost entirely distinct, with independent bacterial sources and degradation mechanisms. In HMW DON, all measured indices support a surface-produced, semi-labile component which is progressively altered in the mesopelagic with increasing radiocarbon age. In contrast, for LMW SPE-DON, AA-based proxies showed conflicting results. Some proxies (D/L ratios of most D-AA, non-protein AA, mol% Gly, and %C-AA) indicated LMW SPE-DON was less labile and more degraded than HMW DON. However other proxies (D/L-Ala, the N isotope based ΣV parameter, and the commonly used DI index) indicated equivalent or even less degradation and resynthesis in the isolated LMW material compared to HMW material, suggesting a disconnect in the underlying mechanisms reflected by different proxies. Finally, AA composition and degradation state in the subsurface samples of both HMW and LMW DON varied little with increasing radiocarbon age, suggesting that HMW and LMW pools may cycle independently. Together, our results suggest that AA DON sources, while almost entirely bacterial, may be more diverse than previously believed, and that much of the hydrolysable AA pool in the ocean may not be derived from proteinaceous material. Overall, these observations support the microbial nitrogen pump idea, but with compositionally unique refractory components in both HMW and LMW material which resist degradation over millennial timescales.

Improved protocols for large-volume injection and liquid chromatography–mass spectrometry analyses enable determination of various glycerol dialkyl glycerol tetraethers in a small amount of sediment and suspended particulate matter

Glycerol dialkyl glycerol tetraethers (GDGTs) have received considerable attention because they are useful indicators for paleoenvironment, organic matter source, and microbial community. In this study, a new simple method was developed for the analysis of GDGTs by using direct large-volume injection (LVI)–liquid chromatography (LC)–atmospheric pressure chemical ionization–mass spectrometry (APCI–MS) to reduce the usage of sediment or seawater suspended particulate matter (SPM) samples. The parameters of accelerated solvent extraction and LVI of target GDGTs were optimized. Under optimal conditions, the LVI approach (500 μL injection) coupled with LC–APCI–MS could determine various GDGTs even with 0.02–0.10 g of sediment samples or SPM samples collected from 0.2–1.0 L of marginal sea water or 10–20 L of open ocean seawater with satisfactory method precision (relative standard deviations ≤10.2%) and linearity (R2 ≥ 0.991). Compared with the classical method, the LVI–LC–APCI–MS required significantly reduced amount of sediment or SPM sample. Finally, the proposed method was applied to determine GDGTs in real sediment samples collected from hydrothermal vent sites at the Southwest Indian Ridges. Four groups of GDGTs, namely, isoprenoid GDGTs (isoGDGTs), branched GDGTs, H-GDGTs and OH-GDGTs, and archaeol, glycerol dialkanol diethers (GDDs) and glycerol monoalkanediol diethers (GMDs) were detected with only 0.02 g of sediment sample collected from Longqi and Tianzuo hydrothermal fields. The organic matter in the sediment sample from Tianzuo was significantly affected by hydrothermal activity. In addition, isoGDGTs in seawater SPM from the open area of Eastern Indian Ocean were investigated for the first time. Six common isoGDGTs were all detected in surface and subsurface SPM samples (filtering 10 L of seawater), which indicated that the LVI approach could noticeably reduce the workload of collecting seawater SPM on board and could be used to investigate conveniently the distribution of GDGTs in water column especially in open oceans and deep seas.

Spatial patterns of soil salinity in the central Argentinean Dry Chaco

The Dry Chaco is a semi-arid ecoregion in South America that hosts one of the largest dry forests in the world, but expansion of dryland agriculture and cattle ranching led to gradual conversion of native vegetation to anthropogenic land cover. The potential impact of these newly established agricultural lands on the surrounding environment is of great concern. Local studies have shown that deforestation leads to changes in the soil-water balance, and can expedite groundwater rise and mobilization of water-soluble salts to the surface affecting plant growth and crop productivity. This study is a regional assessment of soil salinity and salinization processes in the central Argentinean Dry Chaco. It is based on extensive dataset of 492 surface and 142 subsurface samples taken along east-west transects across the Dry Chaco. Soil electrical conductivity (EC) was used as an indicator of salinity, and supplementary information on salt crusts was derived from Google Earth imagery. Subsurface salinity (i.e., measured at 100 cm depth) showed clear regional patterns in natural soil salinity that are related to the annual water budget and topography. Besides primary salinization due to arrested drainage and landscape stagnation, anthropogenic activities increased secondary salinization, especially in the agricultural areas with shallow groundwater tables and irrigated croplands. In addition, the study demonstrated that remotely-sensed vegetation indices such as the seasonal variation in the density of green vegetation are particularly suitable to monitor regional variation in soil salinity. Our results show that the extent of future dryland salinization in the Dry Chaco will mainly depend on whether areas prone to natural soil salinity are further protected from deforestation, and the magnitude and rate of groundwater rise after deforestation as conditioned by local climate and geomorphology. This better understanding of soil salinity patterns and how they are affected as a result of anthropogenic activities is important for the implementation of appropriate and effective measures to prevent severe salinization.

Electrochemical Properties of Latosols with Different Mineralogies

ABSTRACT Studying the electrochemical behavior of colloidal particles is important for fertility management and soil conservation, since it enables the understanding of several physicochemical phenomena that occur in soils. The objective of this study was to determine the point of zero charge (PZC) and the electrochemical behavior of surface and subsurface samples of three Red-Yellow Latosols (Oxisols), with different mineralogical and textural characteristics, through potentiometric titration and ionic adsorption. The point of zero charge (PZC) and the electrochemical behavior were determined in samples from the A and B horizons of three Red-Yellow Latosols: very clayey kaolinitic (LVAcr), very clayey gibbsitic (LVAgr) and sandy loam kaolinitic (LVAcm). The analyses were conducted in soil samples with particle size smaller than 0.7 mm, with desaturation of aluminum (Al3+), and smaller than 2 mm, without desaturation. Solutions containing sodium (Na+) and nitrate (NO3 −) as indifferent electrolytes were used in all methods. The LVAgr, even with higher organic matter contents, had higher PZC, indicating the importance of mineralogical composition for this characteristic. Among the two kaolinitic soils, there was higher PZC in LVAcm, with lower organic matter content; however, both soils had higher PZC in the B horizon than in the A horizon. The net electrical charge estimated by the potentiometric titration method was equivalent to the net charge estimated by the ionic adsorption method for horizons A and B of LVAgr and LVAcm. At the same time, there was underestimation of the net negative charge by the potentiometric titration method for the A and B horizons of LVAcr.

Microfacies analysis and reservoir discrimination of channelized carbonate platform systems: An example from the Turonian Wata Formation, Gulf of Suez, Egypt

The channelized carbonate reservoirs played important role in the global hydrocarbon production. This study presents a new contribution to the carbonate platform system of the Turonian sediments in the Gulf of Suez. The siliciclastic fluvial channelized system incised the carbonate platform in October Field to deposit excellent reservoir unit. Also, the study interprets the facies change, depositional environment, and petrophysical characteristics of the Turonian Wata sequence, to figure out the fluvial channel reservoir distribution and discrimination using surface outcrops in addition to five cored wells. The petrographic analysis and depositional settings interpretations were conducted to the subsurface and outcrop samples. Then, the conventional core analysis measurements were combined with borehole logs for optimum reservoir discrimination, rock typing, and flow units interpretation. Besides, we studied the reservoir heterogeneity and predict permeability and reservoir rock typing in the un-cored intervals. Our finding revealed that the Wata Formation is subdivided into three main lithological units characterized by 16 microfacies. The lower and upper ones are carbonate dominated, composed of wackestones, packstones, and grainstones which is deposited in platform setting belong to lower/middle shelf and mid/outer shelf to outer ramp setting respectively. The middle unit is classified into lower and upper zones, where the lower clastic zone is composed of vari-sized sandstones, siltstone, and mudstone with some plant remains deposited in a point bar of fluvial channel and flood plains. The upper zone is composed of clastic/carbonate intercalations deposited in intertidal/shelf settings. The integration between the petrography and petrophysics enables discriminating the Wata sandstone reservoir into four static rock types (PSRT 1–4), which are controlling its reservoir quality and heterogeneity. The PSRT1 and PSRT2 have the best reservoir quality in the channelized unit and are recommended to be tracked along with October Field. The HFU2 and HFU3 are the main flow capacity in the Wata reservoir, composed of PSRT1 and PSRT2, and represented by the calcareous and ferruginous quartz arenite microfacies. This study presented a secondary dolomitized microfacies with 85% oil potentiality resulted from the incision of the fluvial channel above the aerially exposed carbonate lower unit. The research addressed the optimized petrophysical properties and reservoir heterogeneity of the channelized Wata sequences. In addition, it highlights a guidelines for further exploration and production of these reservoirs in the basin.

Integrated assessment of the impact of land use types on soil pollution by potentially toxic elements and the associated ecological and human health risk

The impact of land use type on the content of potentially toxic elements (PTEs) in the soils of the Qinghai-Tibet Plateau (QTP) and the associated ecological and human health risks has drawn great attention. Consequently, in this study, top- and subsurface soil samples were collected from areas with four different land uses (i.e., cropland, forest, grassland, and developed area) and the total contents of Cr, Cd, Cu, Pb and Zn were determined. Geostatistical analysis, self-organizing map (SOM), and positive matrix factorization (PMF), ecological risk assessment (ERA) and human health risk assessment (HRA) were applied and used to classify and identify the contamination sources and assess the potential risk. Partial least squares path modeling (PLS-PM) was applied to clarify the relationship of land use with PTE contents and risk. The PTE contents in all topsoil samples surpassed the respective background concentrations of China and corresponding subsurface concentrations. However, the ecological risk of all soil samples remained at a moderate or considerable level across the four land use types. Developed area and cropland showed a higher ecological risk than the other two land use types. Industrial discharges (32.8%), agricultural inputs (22.6%), natural sources (23.7%), and traffic emissions (20.9%) were the primary PTE sources in the tested soils, which indicate that anthropogenic activities have significantly affected soil PTE contents to a greater extent than other sources. Industrial discharge was the most prominent source of non-carcinogenic health risk, contributing 37.7% for adults and 35.2% for children of the total risk. The results of PLS-PM revealed that land use change associated with intensive human activities such as industrial activities and agricultural practices distinctly affected the PTE contents in soils of the Qinghai-Tibet Plateau.

Key factors controlling colloids–bulk soil distribution of polybrominated diphenyl ethers (PBDEs) at an e-waste recycling site: Implications for PBDE mobility in subsurface environment

Accumulation of polybrominated diphenyl ethers (PBDEs) in surface soils at elevated concentrations is common at e-waste recycling sites. Even though highly insoluble, migration of PBDEs into the vadose zone and groundwater is possible, due to their association with soil colloids. Here, we show that upon equilibration with artificial rainwater surface and subsurface soil samples collected at an e-waste recycling site release significant quantities of colloids, with the total concentrations of 14 PBDE congeners as high as 990 ng/g dw. The concentrations of different congeners vary markedly in the colloids, and that of BDE-209 is the highest in all the samples. Notably, even the colloids released from the soil collected at a depth of 95–105 cm contain high concentrations of PBDEs. Preferential binding of PBDEs to soil colloids is observed, with the colloids-soil distribution coefficients above 10 in certain cases. The extent of preferential binding displays no apparent correlation with the relative hydrophobicity of the PBDEs, nor can it be explained simply by considering the higher specific surface area, pore volume, and clay content of the soil colloids than the respective bulk soil. Principal component analysis shows that multiple soil properties are collectively responsible for the preferential distribution of PBDEs. Specifically, the differences in pore volume, soil organic carbon content, and pore size between colloids and soils are likely the major factors affecting the distribution of high-concentration PBDEs, whereas the differences in clay content, pore volume and specific surface area are the key factors affecting the distribution of low-concentration PBDEs. The findings clearly show that colloids are an important medium with which PBDEs are associated at contaminated sites, and underline the need of understanding colloid-facilitated transport of PBDEs at e-waste sites.

In situ disposal of crushed concrete waste as void fill material at UK nuclear sites: Leaching behavior and effect of pH on trace element release

The leaching behavior of stockpiled crushed concrete waste is important in determining its suitability for in situ disposal at UK nuclear sites. Sand sized particles from surface (0–0.1 m) and subsurface (2.5–2.7 m) samples were composed of silica and calcite grains in a matrix of calcium alumina-silicate hydrate (C-(A)-S-H) with Ca/Si ratios of 0.5 ±0.3 and 0.9 ±0.3 respectively. Calcite content was also higher in surface samples indicating a greater degree of weathering and carbonation. This resulted in lower leachate pH for the surface samples (pH 8–9.6) compared to subsurface samples (pH 10–11.3). The waste displayed a high acid buffering capacity but low alkaline buffering capacity. Element release as a function of pH was similar for surface and sub-surface samples and between different size fractions. Leaching of contaminant metals was close to minimum values at the pH values produced by the crushed concrete but increased by several orders of magnitude at pH <5 (for Al, Pb, Cr and V) and pH >12 (for Al and Pb). Weathering and carbonation during long-term stockpiling, therefore, has a positive impact by producing a waste with stable pH and low metal leaching potential suitable for in-situ disposal as a void fill material.

Microplastic variability in subsurface water from the Arctic to Antarctica

Comparative investigations of microplastic (MP) occurrence in the global ocean are often hampered by the application of different methods. In this study, the same sampling and analytical approach was applied during five different cruises to investigate MP covering a route from the East-Siberian Sea in the Arctic, through the Atlantic, and into the Antarctic Peninsula. A total of 121 subsurface water samples were collected using underway pump-through system on two different vessels. This approach allowed subsurface MP (100 μm–5 mm) to be evaluated in five regions of the World Ocean (Antarctic, Central Atlantic, North Atlantic, Barents Sea and Siberian Arctic) and to assess regional differences in MP characteristics. The average abundance of MP for whole studied area was 0.7 ± 0.6 items/m3 (ranging from 0 to 2.6 items/m3), with an equal average abundance for both fragments and fibers (0.34 items/m3). Although no statistical difference was found for MP abundance between the studied regions. Differences were found between the size, morphology, polymer types and weight concentrations. The Central Atlantic and Barents Sea appeared to have more MP in terms of weight concentration (7–7.5 μg/m3) than the North Atlantic and Siberian Arctic (0.6 μg/m3). A comparison of MP characteristics between the two Hemispheres appears to indicate that MP in the Northern Hemisphere mostly originate from terrestrial input, while offshore industries play an important role as a source of MP in the Southern Hemisphere. The waters of the Northern Hemisphere were found to be more polluted by fibers than those of the Southern Hemisphere. The results presented here suggest that fibers can be transported by air and water over long distances from the source, while distribution of fragments is limited mainly to the water mass where the source is located.

Hydrogeochemical Characterization of Groundwater Quality in Parts of Amroha District, Western Uttar Pradesh, India

The present work attempts to characterize groundwater quality and ascertain its suitability for drinking and agricultural practices using different indices. A total of 122 sub-surface water samples were collected from the Amroha district of Uttar Pradesh, India, in the pre and post-monsoon season 2018 (61 samples of each season). The quality of groundwater observed from the study region has a slightly acidic to alkaline character with moderately hard type water. The order of the dominant ions is Na+ > Ca2+ > Mg+ > K+ and HCO−3 > Cl− > SO42− > NO−3 > F− in the pre-monsoon season while Na+ > Mg+ > Ca2+ > K+ and HCO−3 > SO42− > Cl− > NO−3 > F− in the post-monsoon season. A few samples show a higher concentration of Nitrate and Fluoride. The correlation coefficient shows that EC is positively correlated with TDS, Cl−, Ca2+, Mg+, and Total Hardness. The WQI studies revealed that about 52.45%, 36.07%, and 11.48% samples denoted excellent, good, and poor water quality, respectively, in the pre-monsoon season. About 52.45%, 45.9%, 1.63% of groundwater samples fell under excellent, good, and poor water quality in the post-monsoon season. The Piper diagram depicts Ca–HCO3, mixed Ca-Na-HCO3, Na–Cl, and mixed Ca-Mg-Cl facies in the water samples. Chloro-alkaline indices show negative values, which indicates that most parts of the study area exist in the discharge zone and base ion exchange processes occurred in the area. The position of the sample on the Gibbs diagram revealed that the rock-water interaction and evaporation of dissolved formation are the major governing process of water chemistry. Irrigation water quality indices revealed that the water quality for irrigation uses is mainly excellent to permissible type. The result of the Corrosivity ratio shows that about 24.5% of groundwater of the study area can be transported only through PVC pipes.

Retrieval of Lunar Surface Dielectric Constant Using Chandrayaan-2 Full-Polarimetric SAR Data

For more than four decades, it has been known that the dielectric constant of the lunar surface can be retrieved from the Fresnel reflection coefficients. However, theoretical models have met with limited success in validating laboratory test results from the Apollo missions to date. This paper is the first study to focus on the use of high-resolution full-polarimetric synthetic aperture radar datasets for the retrieval of the dielectric constant of the lunar surface from the Fresnel reflection coefficients. We initially show that it is possible to retrieve the lunar dielectric constant via the classical Freeman-Durden Decomposition (FDD). The performance of the FDD algorithm is found to be unacceptable over regions with surface slopes and craters, and for sub-surface soil samples. Accurate estimation is not possible by simply replacing the volume scattering model in the FDD with popular and widely used volume scattering models. Therefore, a model-based three-component decomposition (TCD) algorithm for a robust retrieval of the lunar dielectric constant is proposed. The proposed TCD algorithm implements an efficient branching condition combined with double unitary matrix rotations and provides exceptionally accurate dielectric constant estimation. The proposed TCD algorithm is validated by using L band full-polarimetric datasets acquired by the Chandrayaan-2 mission over Apollo 12, Apollo 15, and Apollo 17 landing sites. Comparisons are also made with other three-component decomposition algorithms. Excellent agreement between the estimated values by the proposed TCD algorithm and the reference values for the dielectric constant, available from the literature, has been observed.

Optimizing mangrove conservation efforts with improved understanding of phytosociology-ecology synergy in Sri Lanka

The study aimed to understand the forest structure and ecological factors influencing mangrove distribution in eight mangrove forests across three climatic zones in Sri Lanka. We studied mangrove diversity and vegetation structure with 10m wide belt transects laid of different lengths (n=96) across the land-water gradient. Mangroves along the transect were identified, enumerated, and measured diameter at breast height (DBH). Subsurface water samples were taken in the adjoining lagoon/estuary to assess the environmental parameters (n=144), and water quality parameters were measured. Site-dependent spatial changes in the community structure were depicted through cluster analysis (CA). The forest survey revealed a heterogeneous mixture of 20 true mangrove species across the sites dominated by Avicennia, Rhizophora, and Sonneratia spp. Among the several environmental parameters analyzed by the distance-based redundancy ordination analysis (dbRDA), salinity, dissolved oxygen, and precipitation were found to be controlling factors in mangrove community structure. In addition, discriminant analysis confirmed the presence of ecological-phytosociological influence on mangrove assemblages identified through CA. The significant structural parameters tree density, and taxonomic diversity when tested using the canonical analysis of principal coordinates (CAP), altered the species abundance across the sites surveyed. The results suggest that there is a strong linkage between phytosociology and ecology with the mangrove forest distribution and this relationship needs to be considered wisely to fortify successful restoration practices.

Particle shape trends across experimental cohesive and non‐cohesive sediment gravity flow deposits: Implications for particle fractionation and discrimination of depositional settings

AbstractFractionation of particles in deep‐water sediment gravity flows is an important factor in the resulting deposit and for discriminating sedimentary environments, but remains poorly understood. Quantitative characterization of particle shape was performed for more than ten‐thousand particles of experimental gravity flow experiments (both of cohesive and non‐cohesive nature) made using coal and kaolin particles. Eleven particle shape parameters were calculated and their distribution and trends within the experimental basin were evaluated. Results indicate the existence of non‐normal distributions and observable correlations between particle shape parameters. Shape parameters such as circularity and roundness are dominant controls on shape variation. Strong correlations exist between mean shape parameters and along‐flow distance from the source for particles in non‐cohesive flow experiments. Important differences were observed between shape parameter distributions of particles sampled at different areas within the experimental basin, which can be grouped based on their depositional setting (proximal or distal) using multivariate statistical analysis, especially for the non‐cohesive flow experiments. A tendency for more elongated and irregularly‐shaped particles at the more distal and marginal areas of the studied experimental basin was observed and validated by previous field studies in real‐world deep‐marine deposits. Besides, fractionation of particles is less‐pronounced in cohesive flows compared with non‐cohesive ones suggesting the soundness of discrimination of depositional settings based solely on particle shape characteristics is strongly dependent on parent flow characteristics. Yet, results highlight the potential of particle shape analysis in revealing spatial particle shape trends due to hydrodynamic fractionation and discriminating different depositional settings within submarine fans. This methodology may be applied to seafloor and subsurface samples to help identify the flow process and depositional environment.