Environmental Monitoring and Peat Assessment Using Multivariate Analysis of Regional-Scale Geochemical Data

A compositional multivariate approach was used to analyse regional-scale soil geochemical data obtained as part of the Tellus Project generated by the Geological Survey of Northern Ireland. The multi-element total concentration data presented comprise X-ray fluorescence (XRF) analyses of 6862 rural soil samples collected at 20-cm depth on a non-aligned grid at one site per \(2\,\hbox {km}^{2}\). Censored data were imputed using published detection limits. Each soil sample site was assigned to the regional geology map, resulting in spatial data for one categorical variable and 35 continuous variables comprised of individual and amalgamated elements. This paper examines the extent to which soil geochemistry reflects the underlying geology or superficial deposits. Since the soil geochemistry is compositional, log-ratios were computed to adequately evaluate the data using multivariate statistical methods. Principal component analysis (PCA) and minimum/maximum autocorrelation factors (MAF) were used to carry out linear discriminant analysis (LDA) as a means to discover and validate processes related to the geologic assemblages coded as age bracket. Peat cover was introduced as an additional category to measure the ability to predict and monitor fragile ecosystems. Overall prediction accuracies for the age bracket categories were 68.4 % using PCA and 74.7 % using MAF. With inclusion of peat, the accuracy for LDA classification decreased to 65.0 and 69.9 %, respectively. The increase in misclassification due to the presence of peat may reflect degradation of peat-covered areas since the creation of superficial deposit classification.     

Large wood transport modelling by a coupled Eulerian–Lagrangian approach

The paper discusses a model which predicts the trajectory of floating rigid bodies and may be applied to compute the motion of woody “debris” mobilized during floods. The model couples a Discrete Element (DE) Lagrangian approach for the calculation of motion of rigid bodies with the Eulerian solution of the shallow water equations (SWE), in order to simulate the transport of a cylinder in a two-dimensional stream. It differs from existing models since it is based on a dynamic approach, adapting the Basset–Boussinesq–Oseen equation. In a first step, forces are computed from flow and log velocities; then, the equations of dynamics are solved to model the planar roto-translation of the body. Model results and physical reliability are clearly affected by the values of the drag and side coefficients, especially since logs, modelled as cylinders, are able to change their orientation towards the flow. Experimental studies to evaluate drag and side coefficients can be found in the literature for a submerged cylinder, with various orientations. To extend such results to the case of a floating log, the authors performed a series of laboratory tests on partially submerged cylinders, implementing the outcomes in the proposed DE-SWE model. The coupled model is validated against existing laboratory data concerning spheres and wooden cylinder transport.     

Geochemical constraints on the tectonic setting of the Sonakhan Greenstone Belt,Bastar Craton,Central India

The Neo-Archean Sonakhan Greenstone Belt (SGB) located in the north-eastern fringes of Bastar craton, Central India, is dominated by Basalts, Andesites, Dacites and Rhyolites association. Partial melting modeling on the SGB metabasalts indicates that these rocks were derived by 20% melting of spinel peridotite. Fractional crystallisation modeling with REE reveal that the most evolved samples represent the product of fractional crystallization of least evolved magma with 35% plagioclase, 35% clinopyroxene, 20% olivine, 5% magnetite and 5% ilmenite as fractionating minerals with 40% remaining magma. Depletion of HFSE with reference to the LILE and LREE/HFSE ratios and Nb, Zr anomalies in the multi-element diagram of the mafic rocks of SGB indicate Island arc magmatic setting. The enriched Th/Yb values further substantiate that the mantle arrays were modified by subduction-related fluids or melts. The general conclusions drawn indicate that the metabasalts from the SGB were formed as a result of subduction of an intraoceanic lithosphere in a fore-arc suprasubduction zone environment.     

Assessment of trace metals contamination in stream sediments and soils in Abuja leather mining,southwestern Nigeria

This study is aimed at determining the level of environmental degradation as well as the concentration of trace elements in soil and stream sediments in order to evaluate the environmental impact of the mining operation. Twenty-five (25) soils and ten (10) stream sediment samples were collected from the study area. The physicochemical parameters were determined using appropriate instrumentation with the aid of a digital pH meter (Milwaukee meter) to measure the pH and electrical conductivity, total dissolved solids, moisture content and loss on ignition of the soil and stream sediment samples. The pH of the soil sample ranged from (6.10 to 7.19); Electrical conductivity ranged from (21.3 to 279.4 µS/cm), moisture content varied from (0.60% to 7.20%), and the LOI ranged from (2.03% to 18.62%). The results of the analysis showed that the concentrations of the trace elements in the soils and stream sediment samples were slightly higher than the background values. Plots of the trace elements in stream sediment samples show moderate, consistent decrease downstream except at points where there was mine water discharge into the main river. The pollution levels of heavy metals were examined in stream sediment and soil samples using different assessable indices, such as the enrichment factor, which showed significant-moderate enrichment for Cr, Th, Nb, Zn, Pb, Y and Zr and the geo-accumulation index, which showed practically moderate contamination with Cr, Ni and Sr based on regional background reference values. Geo-accumulation index and contamination index for soils and stream sediment revealed uncontaminated to moderate contamination. Likewise, elements with moderate contamination were Cr, Ni and Sr. The Pearson correlation showed that there were significant positive associations among selected metals in soil and stream sediment samples.     

Distribution and geochemical significance of trace elements in shale rocks and their residual kerogens

There is a dearth of information about the distribution of trace elements in kerogen from shale rocks despite several reports on trace element composition in many shale samples. In this study, trace elements in shale rocks and their residual kerogens were determined by inductively coupled plasma–mass spectrometry. The results from this study show redox-sensitive elements relatively concentrated in the kerogens as compared to the shales. This may be primarily due to the adsorption and complexation ability of kerogen, which enables enrichment in Ni, Co, Cu, and Zn. For the rare earth elements (REEs), distinct distribution characteristics were observed for shales dominated by terrigenous minerals and their kerogen counterparts. However, shales with less input of terrigenous minerals showed similar REE distribution patterns to their residual kerogen. It is speculated that the distribution patterns of the REEs in shales and kerogens may be source-related.     

Stability at high-pressure,elastic behaviour and pressure-induced structural evolution of CsAlSi<Subscript>5</Subscript>O<Subscript>12</Subscript>, a potential host for nuclear waste

The elastic and structural behaviour of the synthetic zeolite CsAlSi₅O₁₂ (a = 16.753(4), b = 13.797(3) and c = 5.0235(17) Å, space group Ama2, Z = 2) were investigated up to 8.5 GPa by in situ single-crystal X-ray diffraction with a diamond anvil cell under hydrostatic conditions. No phase-transition occurs within the P-range investigated. Fitting the volume data with a third-order Birch–Murnaghan equation-of-state gives: V ₀ = 1,155(4) ų, K _T0 = 20(1) GPa and K′ = 6.5(7). The “axial moduli” were calculated with a third-order “linearized” BM-EoS, substituting the cube of the individual lattice parameter (a ³, b ³, c ³) for the volume. The refined axial-EoS parameters are: a ₀ = 16.701(44) Å, K _T0a = 14(2) GPa (β_a = 0.024(3) GPa^?1), K′ _a = 6.2(8) for the a-axis; b ₀ = 13.778(20) Å, K _T0b = 21(3) GPa (β_b = 0.016(2) GPa^?1), K′ _b = 10(2) for the b-axis; c ₀ = 5.018(7) Å, K _T0c = 33(3) GPa (β_c = 0.010(1) GPa^?1), K′ _c = 3.2(8) for the c-axis (K _T0a:K _T0b:K _T0c = 1:1.50:2.36). The HP-crystal structure evolution was studied on the basis of several structural refinements at different pressures: 0.0001 GPa (with crystal in DAC without any pressure medium), 1.58(3), 1.75(4), 1.94(6), 3.25(4), 4.69(5), 7.36(6), 8.45(5) and 0.0001 GPa (after decompression). The main deformation mechanisms at high-pressure are basically driven by tetrahedral tilting, the tetrahedra behaving as rigid-units. A change in the compressional mechanisms was observed at P ≤ 2 GPa. The P-induced structural rearrangement up to 8.5 GPa is completely reversible. The high thermo-elastic stability of CsAlSi₅O_12, the immobility of Cs at HT/HP-conditions, the preservation of crystallinity at least up to 8.5 GPa and 1,000°C in elastic regime and the extremely low leaching rate of Cs from CsAlSi₅O₁₂ allow to consider this open-framework silicate as functional material potentially usable for fixation and deposition of Cs radioisotopes.     

Experimental study on the deterioration and natural remediation of the Ariake Sea tidal mud caused by the sea laver treatment acid practice and the upward seepage of pore water liquid

This study presents a laboratory study of the following two aspects: (1) the influence of sea laver treatment acid on the geoenvironmental properties of Ariake Sea tidal mud, and (2) the natural remediation effect on the sea laver treatment acid contaminated Ariake Sea tidal mud caused by the upward seepage of pore water liquid in the mud. Firstly, the mechanisms of the transport of sea laver treatment acid in the Ariake Sea tidal mud and the generation mechanisms of the upward seepage flow in the Ariake Sea tidal mud are discussed. Secondly, a series of one-dimensional laboratory infiltration tests were carried out to investigate the deterioration of the Ariake Sea tidal mud caused by the sea laver acid treatment practice. Test results reveal that the acid treatment practice caused considerable change in the geochemical properties of the mud in terms of increase in sulfide content and decrease in pH value. After the treatment by the sea laver treatment acid, the sulfide content of the mud even exceeded the safe limit value for the benthos, which represents undesirable living condition for benthos. Thirdly, series of laboratory fresh seawater infiltration tests for the deteriorated Iida site mud were conducted to illustrate this natural remediation efficiency. It is found that with the infiltration of the fresh seawater, the sulfide content of the Iida site mud was considerably reduced and pH value increased to an acceptable range for benthos living in the tidal flat mud. With the increase in the infiltration time and the hydraulic gradient, the remediation efficiency could be increased.     

Do Spur-Throated Grasshoppers, <Emphasis Type="Italic">Melanoplus</Emphasis> spp. (Orthoptera: Acrididae), Exert Top-Down Control on Smooth Cordgrass <Emphasis Type="Italic">Spartina alterniflora</Emphasis> in Northern New England?

Recently, strong top-down (consumer) control of cordgrass (Spartina alterniflora) has been demonstrated. Here, we manipulated the densities of cordgrass consumers, acridid grasshoppers (Melanoplus bivittatus and Melanoplus femurrubrum), to examine their impact on cordgrass in the Plum Island Estuary (PIE), MA, USA. After 1 month, there was no detectable effect of grasshopper density on S. alterniflora biomass and grasshoppers at the highest densities (34 individuals per square meter) consumed only ~14% of the standing stock biomass. However, significant impacts of grasshopper density on grazing damage were seen. For example, plant damage and scarring length increased by 160% and 6,156%, respectively, at the highest grasshopper densities relative to exclusion (zero grasshoppers) densities. Plant height was significantly reduced with increasing grasshopper densities, although this may be a function of leaf tip removal instead of reduced plant growth. No other strong consumers of cordgrass (e.g., Littoraria irrorata, Prokelisia marginata) were observed in PIE and we suggest that consumer regulation of cordgrass is weak in this system.     

Water and Boating Activity as Dispersal Vectors for <Emphasis Type="Italic">Schinus terebinthifolius</Emphasis> (Brazilian pepper) Seeds in Freshwater and Estuarine Habitats

Schinus terebinthifolius (Brazilian pepper), a native of South America, is currently naturalized in 20 countries worldwide and can alter native systems by displacing flora and forming monotypic stands. The primary described mechanism of seed dispersal is through consumption of fruits by birds and mammals. We evaluated an alternative dispersal method by evaluating the potential for S. terebinthifolius growing in freshwater and estuarine environments to disperse via water currents. Specifically, we: (1) determined the duration fruits remained buoyant in three salinities, (2) estimated the viability of seeds after 7 days in water, (3) estimated the dispersal rate of floating solitary fruits, and (4) examined the role of boat wakes in moving seeds above mean high water at the shoreline. The length of time fruits floated in 0 ppt water (4.9 days) was significantly less than 15 ppt saltwater (6.2 days), and 30 ppt saltwater (6.9 days). After 7 days, over 13% of seeds remained viable in 0 ppt, 15 ppt, and 30 ppt water. By combining mean dispersal rates and the mean number of days fruits floated, we calculated individual fruits could be transported 16.9 km in 0 ppt and over 22 km in 15 and 30 ppt water. To increase germination, seeds must be stranded above the intertidal zone. Wind wakes alone never achieved this result; however, boat wakes plus wind wakes significantly increased the movement of fruits above the intertidal region into drier soils. The use of both vertebrate dispersal vectors and water dispersal may potentially increase the rate of invasion, establishment, and survival of S. terebinthifolius in freshwater and estuarine environments.