Neural Network Based Estimation of Service Life of Different Metal Culverts in Arkansas

The Arkansas Department of Transportation (ARDOT) uses different types of metal culverts and cross-drains. Service lives of these culverts are largely influenced by the corrosion of the metals used in these culverts. Corrosion of metallic parts in any soil-water environment is governed by geochemical and electrochemical properties of the soils and waters. Many transportation agencies including ARDOT primarily focus on investigating the physical and mechanical properties of soils rather than their chemical aspects. The main objective of this study is to analyze the geotechnical and geochemical properties of soils in Arkansas to estimate the service lives of different metal pipes in different conditions. Soil resistivity values were predicted after analyzing the United States Department of Agriculture (USDA) soil survey data using neural network (NN) models. The developed NN models were trained and verified by using laboratory test results of soil samples collected from ARDOT, and survey data were obtained from the USDA. The service lives of metal culverts were then estimated based on the predicted soil properties and water quality parameters extracted from the data acquired from the Arkansas Department of Environmental Quality (ADEQ). Finally, Geographic Information System-based corrosion risk maps of three different types of metal pipes were developed based on their estimated service lives. The developed maps will help ARDOT engineers to assess the corrosion potential of the metal pipes before starting the new construction and repair projects and will allow using proper culvert materials to maximize their life spans.

Modelling seabed sediment physical properties and organic matter content in the Firth of Clyde

High-quality quantitative maps of seabed sedimentary physical and geochemical properties have numerous research and conservation applications, including habitat and ecosystem modelling, marine spatial planning, and ecosystem service mapping. However, such maps are lacking for many ecologically and economically important marine areas. Using legacy data supplemented by measurements from recent benthic surveys, modelled hydrodynamic variables, and high-resolution bathymetry, quantitative maps for the top 10 cm of seabed sediment were generated via a combination of statistical and machine-learning techniques for the Firth of Clyde, a semi-enclosed coastal sea on the west coast of Scotland. The maps include sediment fractions of mud, sand, and gravel; whole-sediment median grain size; sediment permeability and porosity; rates of natural seabed abrasion; and sediment particulate organic carbon and nitrogen content. Properties were mapped over an unstructured grid so that very high resolutions were achieved close to the coastlines, where sediments may be expected to be spatially heterogeneous. Overall, the maps reveal extensive areas of very low sediment permeability coupled with low rates of natural seabed disturbance. Moreover, muddy sediments in the inner Firth of Clyde, Inchmarnock Water, and the sea lochs are enriched in organic carbon and nitrogen relative to the sediments of the outer Firth of Clyde. As a demonstration of the value of these maps, the standing stock of organic carbon and nitrogen in the surficial sediments of the Clyde was calculated. The Clyde stores 3.42 and 0.33 million t of organic carbon and nitrogen in the top 10 cm of seabed sediment, respectively, substantially contributing to Scotland's coastal and shelf blue carbon stocks. Data products are available from https://doi.org/10.15129/2003faa2-ee93-4c11-bb16-48485f5f136d (Heath and Pace, 2021).

Geology, Petrology and Amazing Geoforms of the Late Cenozoic Volcanic Province Erusheti Plateau (Lesser Caucasus) Georgia

These Erusheti Plateau is an integral part of the volcanic highland of Southern Georgia. It is located northern part of the Lesser Caucasus in the convergence zone of the Afro-Arabian and Eurasian lithosphere tectonic plates. The territory is almost totally covered with strong volcanic and volcano-sedimentary formations of Goderdzi suite with different lithologies and facies. The suite is formed in the Late Miocene - Early Pliocene Age, about from 11.8±4 to 13.6±3.1 Ma. Erusheti Plateau overall, are not characterized by many centers of eruption; Here we discuss eruption histories of the large polygenic volcanic massive Dokhuz-Puar and a monogenic volcano Datvistskaro are clearly seen among the volcanogenic structures of Erusheti Plateau. The eruption products of Dokhkuz-Puar volcano are dacitic-containing tuff-breccias and lava flows. The activity of Datvistskaro volcano was expressed only by the eruption of pyroclastic deposits containing andesite basalts. The main constituent minerals are: plagi­oclase and hornblende mega-crystals in dacites; augite-olivine and base plagioclase – in andesite basalts. With their geochemical properties, all the rocks of the rocks of a calc-alkali series. Dacites and andesite-basalts do not feed from a common magmatic source and consequently, are not the product of differentiation of the same magma. The work is the first to describe the natural amazing natural geoforms developed in pyroclastolites of Datvistskaro volcano: gigantic stone columns, mushroom-shaped stone caps and stone lances.Should be noted that no detailed mine­ralogical-petrological study of the rocks common in the study area has done to date. The main purpose of the given work is filling this gap.

Lamination Texture and Its Effects on Reservoir and Geochemical Properties of the Palaeogene Kongdian Formation in the Cangdong Sag, Bohai Bay Basin, China

The characteristics of laminae are critical to lacustrine shale strata. They are the keys to the quality of source rocks and reservoirs, as well as engineering operations in shale plays. This study uses organic geochemistry, thin section identification, X-ray diffraction, field emission scanning electron microscopy, and other analytical methods, to reveal the detailed lamination texture and vertical distribution of laminae in the second Member of the Kongdian Formation in Cangdong Sag. The principal results are as follows: (1) A classification of laminae is proposed to characterize reservoir and geochemical properties. The five types of laminae are as follows: feldspar-quartz laminae (FQL), clay laminae (CLL), carbonate laminae (CAL), organic matter laminae (OML), and bioclastic laminae (BCL). There are also four significant lamina combinations (with the increasing TOC values): FQL-CLL combination, FQL-CLL-BCL combination, FQL-CLL-OML combination, and FQL-CAL-CLL-OML combination; (2) differences between laminae occur because of the variability in pore types and structures. There appears to be a greater abundance of intercrystalline pores of clay minerals in the FQL, CAL, BCL, and OML, and well-developed organic pores in the CAL and CLL, and the counterparts of intragranular pores of bioclastic material in the BCL. This detailed characterization provides the following comparative quantification of the thin section porosity of laminae in the second Member of the Kongdian Formation can be differentiated: CAL > FQL > OML > BCL > CLL; (3) differentiation between vertical distributions of laminae is carried out in a single well. The FQL and CLL are widely distributed in all the samples, while the BCL is concentrated in the upper part of the second Member of the Kongdian Formation, and CAL is concentrated in the lower part. This detailed classification method, using geochemical analysis and vertical distribution descriptions, offers a detailed understanding of lamination texture and its effects on reservoir and geochemical properties, which will provide a scientific guidance and technical support to better estimate reservoir quality and to identify new sweet spots in the second Member of the Kongdian Formation in the Cangdong Sag.

Influence of leachates on geotehnical and geochemical properties of termite mound soils

This study investigated the influence of leachate prepared from Telfairia occidentalis on the geotechnical and geochemical properties of termite mound soil obtained from the premises of the federal university of agriculture, Abeokuta, south-western Nigeria. The termite mound soil samples were collected from three different locations and each sample collected was contaminated by mixing with leachates in percentage increments of 0% 10%, 15% and 20% of dry weight of the air-dried soil. The soil samples were subjected to Atterberg limits and hydraulic conductivity tests for geotechnical observation and X-ray fluorescence tests for geochemical tests. The range of values for the geotechnical analyses were obtained as; plastic limit (9.1% – 14.2%), liquid limit (28.6 % – 61%), plasticity index ((18.2% – 49.5%) and hydraulic conductivity (1.85 – 4.1 x 10-8) cm/sec) with a resultant reduction in the plastic limit, liquid limit and plasticity index values but an increase in the hydraulic conductivity of the samples as the leachate concentration increased. The results from X-ray fluorescence analyses after 20% leachate contamination showed that the major elemental chemical composition for the three samples were comprised of SiO2 (56.25 – 56.5%), Al2O3 (28.42 – 28.50%), Fe2O3 (4.46 – 6.5%), TiO2 (1.08 – 1.23%), CaO (1.45 – 1.60%), P2O5 (0 – 0.04%), K2O (0.9 – 6.1%) and MnO (0.02 – 4.7%). There was a marginal alteration of the indices with the values inferring the presence of a minimum composition of feldspar and a major composition of quartz-rich minerals and thus lending more credence to the presence of silicates as shown from the X-ray fluorescence results. It also infers that the termite mounds are predominantly made from sand materials. The termite soil samples obtained from the aforementioned locations may not be suitable for engineering works unless stabilization procedure is adopted.

Geodiversity primarily shapes large-scale limnology and aquatic species distribution in the northern Neotropics

Geodiversity is recognized as one of the most important drivers of ecosystems characteristics and biodiversity globally. However, in the northern Neotropics, the contribution of highly diverse landscapes and geological history in structuring large-scale patterns of limnology and aquatic species associations remain poorly understood. We evaluate the interaction between geodiversity, limnology and freshwater ostracode assemblages to explore drivers of aquatic ecosystem structure from southern Mexico to Nicaragua. Cluster analysis based on geological, limnological, sedimentological and mineralogical characteristics of 76 aquatic ecosystems (karst, volcanic, tectonic) reveal two main limnological regions: (1) Karst terraces from the Yucatán Peninsula and northern Guatemala, and (2) volcanic terrains of the Guatemalan highlands, El Salvador and Honduras mid-elevations, and Nicaraguan lowlands. In addition, seven limnological subregions were recognized, attesting high limnological heterogeneity. Principal Component Analysis identifies water ionic and sediment composition as most influential for aquatic ecosystem classification and given their source of formation, we recognized geology as the fundamental determinant for large-scale limnological patterns. Multiparametric analyses based on biological data revealed that species association represent disjunct faunas. For instance, five species associations are closely related to limnological regions. Structural equation modelling reveals a strong influence of limnology and elevation on the biological composition, but geodiversity resulted in the most important driver. The confinement of species associations is attributed to regional lake geochemistry. We deduce a linear, continuous and primary influence of geodiversity for limnological structure, geochemical properties and aquatic biological composition in Lakes of the northern Neotropical region.

Combining colour parameters and geochemical tracers to improve sediment source discrimination in a mining catchment (New Caledonia, South Pacific Islands)

Tracing the origin of sediment is needed to improve our knowledge of hydro-sedimentary dynamics at the catchment scale. Several fingerprinting approaches have been developed to provide this crucial information. In particular, spectroscopy provides a rapid, inexpensive and non-destructive alternative technique to the conventional analysis of the geochemical properties. Here, we investigated the performance of four multi-proxy approaches based on (1) colour parameters, (2) geochemical properties, (3) colour parameters coupled with geochemical properties and (4) the entire visible spectrum to discriminate sediment source contributions in a mining catchment of New Caledonia. This French archipelago located in the south-west Pacific Ocean is the world's sixth largest producer of nickel. Open-cast nickel mining increases soil degradation and the downstream transfer of sediments in river systems, leading to the river system siltation. The sediment sources considered in the current research were therefore sediment eroded from mining sub-catchments and non-mining sub-catchments. To this end, sediment deposited during two cyclonic events (i.e. 2015 and 2017) was collected following a tributary design approach in one of the first areas exploited for nickel mining on the archipelago, the Thio River catchment (397 km2). Source (n=24) and river sediment (n=19) samples were analysed by X-ray fluorescence and spectroscopy in the visible spectra (i.e. 365–735 nm). The results demonstrated that the individual sediment tracing methods based on spectroscopy measurements (i.e. (1) and (4)) were not able to discriminate sources. In contrast, the geochemical approach (2) did discriminate sources, with 83.1 % of variance in sources explained. However, it is the inclusion of colour properties in addition to geochemical parameters (3) which provides the strongest discrimination between sources, with 92.6 % of source variance explained. For each of these approaches ((2) and (3)), the associated fingerprinting properties were used in an optimized mixing model. The predictive performance of the models was validated through tests with artificial mixture samples, i.e. where the proportions of the sources were known beforehand. Although with a slightly lower discrimination potential, the “geochemistry” model (2) provided similar predictions of sediment contributions to those obtained with the coupled “colour + geochemistry” model (3). Indeed, the geochemistry model (2) showed that mining tributary contributions dominated the sediments inputs, with a mean contribution of 68 ± 25 % for the 2015 flood event, whereas the colour + geochemistry model (3) estimated that the mining tributaries contributed 65 ± 27 %. In a similar way, the contributions of mining tributaries were evaluated to 83 ± 8 % by the geochemistry model (2) versus 88 ± 8 % by the colour + geochemistry model (3) for the 2017 flood event. Therefore, the use of these approaches based on geochemical properties only (2) or of those coupled to colour parameters (3) was shown to improve source discrimination and to reduce uncertainties associated with sediment source apportionment. These techniques could be extended to other mining catchments of New Caledonia but also to other similar nickel mining areas around the world.

Biological Abundance and Diversity in Organic-Rich Sediments From a Florida Barrier Island Lagoon

Organic-rich sediments in estuaries and the coastal ocean are often a product of land clearing, runoff of excess nutrients and other human activities. They can harbor pollutants, oxygen-consuming microbes and toxic hydrogen sulfide (H2S), thereby creating a hostile environment for infauna. In one barrier island lagoon, the Indian River Lagoon (IRL), Florida, layers of organic-rich sediments have increased substantially in thickness and areal extent over the past 60 years. Geochemical properties of these muddy sediments have been described; however, less is known about their habitability. We analyzed infauna and geochemical properties of 102 samples taken during wet and dry seasons at 17 locations spanning 60 km of the lagoon. We quantified infaunal abundance and diversity (Shannon-Wiener, H′) and determined Pearson’s correlation coefficients for effective number of species (ENS = eH′) vs. sediment porosity (ϕ = 0.69–0.95), organic carbon (1–8%), nitrogen (0.1–0.7%), silt + clay (16–99%), porewater H2S (5–3,600 μM), and other environmental variables. Small bivalves accounted for 70% of the organisms collected, followed by gastropods, polychaetes and other biota. The bivalves were predominantly Macoma spp., Mulinia lateralis and Parastarte triquetra with average abundances of 3,896, 2,049, and 926 individuals per m2, respectively. High abundance of some species, such as Macoma, showed that these opportunists had adapted to poor quality sediments. More than two-thirds of the 35 species collected were present at <100 individuals per m2 of sediment. Cluster analysis identified four groups of stations with significantly different geochemical properties. Permutation analyses of variance indicated that the four groups also represented statistically different infaunal communities. Diversity decreased with increasing sediment concentrations of organic carbon, nitrogen and silt + clay; however, community richness at our most prolific station along the perimeter of muddy deposits was ∼7 times lower than found previously in sandy sediments from the IRL. The results identified areas where infaunal communities have experienced the greatest stress due to accumulation of organic-rich sediments. Results from this study help support management plans for remediation of organic-rich mud and improvement of sediment and water quality, especially in areas identified with low ENS.