Sediment Fractions Research Articles

A randomized study comparing the effect of platelet-rich plasma and platelet-poor plasma for the treatment of plantar fasciitis

Objective: To verify the effectiveness of therapy with platelet-rich plasma (PRP) in patients with plantar fasciitis, this prospective, longitudinal, double-blind study was carried out. Methodology: Twenty-three participants with chronic plantar fasciitis aged > 20 years, already treated with conventional methods were included. Participants were randomly divided into platelet-poor plasma (PPP) and platelet-rich plasma (PRP) groups. Double centrifugation was carried out to prepare the platelets samples and two millilitres of PPP (supernatant fraction) or PRP (sediment fraction) were mixed with 1mL of 2% calcium gluconate solution and injected in the plantar fascia, as a single dose. A follow-up at 15 days and then every 60 days up to 180 days of application was carried out and a visual analogue scale (VAS) for pain assessment and the quality-of-life scale validated by the American Orthopedic Foot and Ankle Society (AOFAS) were used to measure the outcomes. Results: A reduction in pain (VAS 8 to 4), in both groups, was seen in the first 15 days and remained up to the 6th month after the application of plasmas, however, no difference was observed between the groups. No significant improvement was observed in the quality of life of the patients. Conclusion: PPP or PRP were able to reduce the VAS, but the presence of platelets did not have a role in the pain relief. Other factors in the plasma may play a role in reducing the pain caused by plantar fasciitis for a period of up to 180 days.

Evaluating the contribution of hydrothermal fluids and clay minerals to the enrichment of rare earth elements and yttrium (REY) in deep-sea sediments

Deep-sea REY-rich sediments have attracted considerable attention in recent studies because of their extremely high REY resource potential. Previous studies highlighted that hydrothermal precipitates (e.g., Fe-Mn (oxyhydr)oxides) have played an important role in REY enrichment in deep-sea sediments by scavenging REY from seawater. However, the exact extent of the contribution of hydrothermal scavenging to the REY accumulation has not yet been evaluated. In addition, REY enrichment generally occurred in the pelagic clays, and whether the clays have played a role in the REY accumulation is poorly constrained. We studied bulk-sediment geochemistry and mineral fractions of sediments from two sites in the Eastern South Pacific Ocean. The results show that both cores contain REY-rich sediments layers possessing average ΣREY contents of 989 ppm and 1563 ppm, respectively. The calculated REY resource amounts in the 1 km × 1 km × optimal recovery depth (m) of the two sites are summed to 4690 t-REO. Carbonate compensation depth is one of the factors controlling the REY contents in the sediments in our study area. The shale-normalized REY patterns and calculated simulation results suggest that direct input of REY from the hydrothermal sources to the sediments was not significant. The evaluation of the contributions of REY scavenged by hydrothermal Fe-Mn (oxyhydr)oxides suggests that for the metalliferous sediments in which Fe-Mn (oxyhydr)oxides are hydrothermal-dominated, the Fe2O3 and ΣREY contents show a pronounced positive correlation for all cores, implying hydrothermal scavenging of REY significantly contributed to the accumulation of REY. However, with the continuous addition of hydrothermal Fe-Mn (oxyhydr)oxides in the pelagic clay sediments, the ΣREY contents in the REY-rich sediments firstly exhibited an increase, and then when the total Fe2O3 components achieved a certain value (∼25 wt% in this study) they started to decline. This finding suggests the appropriate input of hydrothermal Fe-Mn (oxyhydr)oxides into the sediments certainly increases the ΣREY contents through a scavenging mechanism, but that excessive addition of them would, in turn, decrease the ΣREY contents of the sediments. Additionally, the amount of clay minerals exhibited a significant positive correlation with ΣREY contents, therefore, we inferred that clay minerals probably played an important role in REY accumulation in the sediments.

The geomorphological and ecological functioning of the Silala River

AbstractPerennial rivers in desert regions are relevant environments that tend to concentrate most ecosystem services and values, but are not as studied as much as intermittent and ephemeral rivers. This article reports on the main morphological and ecological features of the Silala River, a narrow permanent river in the arid region of Antofagasta, in the north of Chile. The study was motivated by the dispute between Chile and Bolivia concerning the status of the Silala as an international watercourse. Field surveys of sediment transport using traps and marked sediments (colored and tagged clasts) revealed that finer sediments are moved in higher percentages and for longer distances than coarser sediment fractions, which corroborates the size‐selective nature of sediment dynamics in the river. The stream features the typical step/pool‐plane bed morphology that is to be expected in an alluvial river with the given boundary conditions of slope, grain size of sediments, and lateral confinement. Furthermore, the Morphological Quality Index (MQI) classifies the river as featuring overall good morphological conditions and the river hosts an abundant population of rainbow trout (Oncorhynchus mykiss). Although this is a non‐native species, their presence shows that the general conditions of the river (availability of food and presence of aquatic habitats) are able to sustain a population of resident fish. Overall, the morphological forms, geomorphic processes, and ecological features of the Silala River are typical of an alluvial stream with a permanent flow regime.This article is categorized under: Science of Water > Water and Environmental Change Human Water > Rights to Water Science of Water > Hydrological Processes Water and Life > Nature of Freshwater Ecosystems

The response of organic carbon fractions in sediment to rainfall characteristics and slope lengths: Based on four-years on-site monitoring data

The effect of soil erosion processes on the properties of sediment and organic carbon fractions is not well understood under complex erosion environments, such as various rainfall characteristics and transport distances, which leads to a gap in knowledge regarding the role of soil erosion in the global carbon cycle. This study investigated the impact of different rainfall characteristics (patterns and parameters) and slope lengths (5 m ∼ 20 m) on the sediment yield, particle size distribution (PSD) and properties of organic carbon fractions on China’s Loess Plateau. The results show that runoff was highest under rainfall pattern A (extreme rainfall), while the sediment concentration peaked under rainfall pattern B (heavy rainfall), with significant correlation with slope length, rainfall intensity, kinetic energy, rainfall erosivity and precipitation (p less than 0.05). Silt- and clay-sized fractions were transported as primary particles and enriched under rainfall patterns B and C with no differences between slope lengths. The enrichment ratio (ER) of sediment, effective and ultimate particles were primarily influenced by rainfall intensity-related parameters. In contrast, the aggregation ratio (AR) tended to be influenced by rainfall kinetic energy. The content and loss of organic carbon fractions correlated to rainfall parameters and slope length, although no significant difference was observed between different rainfall patterns and slope lengths. Lost organic carbon fractions were predominantly Mineral-associated organic carbon (MOC), with great enrichment under rainfall pattern C and rapid depletion as the slope length increased. Structural equation models (SEM) indicated the effect of rainfall characteristics and slope length on organic carbon loss was mainly due to the regulation of soil loss and particle size distribution of sediment in selective transport erosion processes. We highlighted the need to consider the effect of soil erosion and particle size distribution comprehensively on the carbon cycle from the perspective of organic carbon fractions to describe the potential effects of soil erosion on the carbon budget quantitatively, especially in complex environmental conditions with consideration of scale effect.

ECOLOGICAL RISK ASSESSMENT OF HEAVY METALS ACCUMULATION IN SOIL AND ZYGOPHYLLUM ALBUM ALBUM: A CASE STUDY OF INDUSTRIAL PHOSPHATE VICINITY, TUNISIA

Contents and spatial distribution of heavy metals (Zn, Cu, Cd, Ni, As, Pb, Al and Ba) in the fine fraction of surface sediments and in Zygophyllum album shrub of zones influenced by phosphate industry in the region of Gabès, as well as in a control site (Sidi Ejjehmi) were determined. For the assessment of the level of sediment pollution, several parameters were calculated, including enrichment factor (EF), contamination factor (CF), Pollutant Load Index (PLI), Risk factor (Er), potential ecological Risk Index (Ri), Geoaccumulation Index (Igeo), Electrical Conductivity (Ec), Organic Matter (OM) and pH.Whereas, Bio-Concentration Factors (BCF) and Translocation Factors (TF) are calculated for the evaluation of pollution degree in Zygophyllum album. The soils of Gabès are characterized by a high average relative concentration of As, Ba, Cd, Cu, Ni, Pb, Al and Zn in all the study sites, indicating contributions from anthropogenic sources. The Igeo and the PLI of heavy metals show that all study sites are heavily polluted. All the EF values of all trace metals from Gabes sites (above 10), indicate a very significant enrichment in soils. The PCA, AC and correlation matrix suggest that soils are mainly polluted by As, Ba, Cd, Cu, Ni, Pb, Al and Zn. For all studied metals, the values of TF in Z. album from Gabes sites are greater than 1 except for Al at S2. All metals studied, except Cd, are more accumulated in shoots than in roots. Values of BAF are greater than 1, as well as TF values are greater than 1, so Z. album of Gabes can be considered as phytoremediator in the case of those studied metals. For Cd, TF is greater than 1 and BCF is less than 1, Z. album can be considered as a phytostabiliser for this metal.

Primary emissions or environmental persistence contribute to the present DDTs: Evidence from sediment records in Tibetan lakes

Dichlorodiphenyltrichloroethane (DDT) compounds are still circulating the global environment even though the technical DDT has been restricted in agriculture since the last century. The persistent presence of DDTs worldwide remains uncertain, as it is unclear whether their existence is primarily due to ongoing use or the prolonged persistence in soils and sediments that result in continuous reemission into the atmosphere. The present study applied a sequential extraction procedure to determine the DDT concentrations in rapid desorption, slow desorption, and bound residue fractions in the dated sediment cores from distinct regions of Tibet. The temporal variation of total DDTs (sum of three fractions) in sediments from southern and eastern Tibet respectively revealed the different DDT usage histories in India and China mainland. Nevertheless, the current application volumes of DDT-containing products in these regions were found to decrease significantly. The reversible transformations among three fractions of DDTs with aging time was observed along sediment profile, including the back conversion from bound residue. This process may be the key driver to prolong the half-life of sediment p,p'-DDT, resulting in the persistence of secondary sources of this persistent organic pollutant in the global environment for a longer duration than previously expected.

Contaminants of emerging concern fate and fluvial biofilm status as pollution markers in an urban river

Contaminants of emerging concern (CEC) are still under research given the vast diversity of compounds reaching freshwater ecosystems and adverse effects they might cause. In this study, the environmental fate of 73 CEC, comprising sweeteners, stimulants and several pharmaceutical therapeutic classes, and changes in fluvial biofilm photosynthetic parameters were evaluated in a semi-arid urban river receiving diffuse and point sources of pollution (Suquía river, Argentina). Out of the 37 CEC detected, 30 were quantified in surface water (n.d. – 9826 ng/L), 10 in biofilm (n.d. – 204 ng/gd.w.) and 9 in the clay fraction of sediments (n.d. – 64 ng/gd.w.). CEC distribute differently among the 3 matrices: water phase presents the biggest diversity of compounds (14 CEC families), being analgesic/anti-inflammatories the most abundant family. Antibiotics largely predominated in biofilms (7 CEC families), while the stimulant caffeine and some antibiotics where the most abundant in sediments (6 CEC families). Different CEC accumulated in biofilms and sediments upstream and downstream the city, and big shifts of biofilm community occurred downstream WWTP. The shift of biofilm community upstream (F0 > 0) and downstream the WWTP (F0 = 0) shows a sensitive response of F0 to the impact of WWTP. Biofilm photosynthetic parameters responded in less impacted urban sites (sites 1, 2 and 3), where significant correlations were found between ketoprofen and some antibiotics and biofilm parameters. The diversity and amount of CEC found in the urban section of Suquía river alert to the magnitude of point and non-point sources of pollution.

Combining Optical and Acoustic Backscatter Measurements for Monitoring of Fine Suspended‐Sediment Concentration Under Changes in Particle Size and Density

AbstractOptical and acoustic backscatter measurements are routinely utilized to monitor suspended‐sediment concentration (M); however, both measurements are affected by changes in particle size and density. In this study, optical and acoustic backscatter measurements are combined to a single parameter, the sediment composition index (SCI), to quantify M, mean particle radius by number (ao), the fraction of sediment <20 μm by diameter (), and particle bulk apparent density (ρbulk). Data are analyzed from Chesapeake Bay and five rivers of Queensland, Australia. SCI is utilized to predict the ratio of M to acoustic backscatter under changes in ao and ρbulk (R2 ranged from 0.6 to 0.98 across all data sets) and combined with acoustic backscatter to predict estimates of M that are independent of changes in ao and ρbulk. SCI is proportional to log10(ao) and for SCI from acoustic backscatter measured at 6 MHz (R2 = 0.8 and 0.74, respectively, p‐value < 0.001, n = 133), while SCI(log10(ao)) and SCI() from acoustic backscatter measured at 2 MHz or lower are sensitive to changes in floc fractal dimension. Estimates of ρbulk from SCI are biased by changes in particle size (R2 is 0.1–0.5 across all datasets). This study builds upon recent work that derived SCI to quantify composition of sand and mud in suspension and demonstrates the utility of the approach in systems transporting flocculated silt and clay. Future research directions are discussed.

The Igarapé Weir decelerated transport of contaminated sediment in the Paraopeba River after the failure of the B1 tailings dam (Brumadinho)

The B1 dam of Córrego do Feijão Mine, owned by Vale, S.A. mining company and located on the Ferro-Carvão stream, collapsed and injected 2.8 Mm3 of clayey, silty, and sandy iron- and manganese-rich tailings into the Paraopeba River (Minas Gerais state, Brazil). The accident occurred on 25 January 2019 and the tailings have been co-transported with coarser natural sediment since then, being partly trapped in the Igarapé Weir reservoir located on the Paraopeba River nearly 45 km downstream the injection point. The general purpose of the current study was to model suspended sediment transport in the vicinity of the Igarapé Weir aiming to assess the concomitant barrier effect imposed by this structure. Specifically, the spatial distributions of suspended clay, silt, and very fine-grained sand fractions (CSS) of sediment were mapped around the Igarapé Weir under low-flow (16 m3/s) and high-flow (5 to 10,000 years return period stream discharge; 699–2,699 m3/s) regimes, using RiverFlow2D as the modelling tool. The concentrations of the various grain materials in the upstream and downstream sectors were quantified linking the barrier effect to concentration reductions in the direction of stream flow. It was also a study goal to calculate differences of iron and manganese concentrations in the sediment + tailings mixtures along the Paraopeba River. The study results showed reductions in the CSS between 6.6% and 18%, from upstream to downstream of the Igarapé Weir, related with backwater effects, free and submerged hydraulic jumps, bank sedimentation in periods of high flow, and streambed sedimentation controlled by channel sinuosity and tailings density. These reductions were accompanied by drops in the concentrations of iron and manganese present in the clay and silt fractions, which varied between 6% and 42% under low flows and between 16% and 44% under high flows. Bank sedimentation was viewed as a potential threat to the riparian vegetation in the long-term. Dredging is the potentially most effective mitigation measure to help lead the Paraopeba River to a pre-rupture condition. The retention of sediment + tailings transported in suspension is less effective than the trapping of bedload sediment + tailings behind the Igarapé weir. The efficacy of sediment trapping is expected to be larger for natural sediment because it is much coarser than the tailings. In that context, the simulations revealed for the low-flow period that 33.6% of the sediment deposition comprised suspended transport of natural sediment (thus, was comprised 66.4% of bedload transport), this proportion rose to 86.9% for mixtures of natural sediment + tailings, a result that did not differ much for the high-flow periods.

Benthic fluxes and mineralization processes at the scale of a coastal lagoon: Permeable versus fine-grained sediment contribution

Benthic fluxes of biogenic compounds play a major role in the biogeochemistry of shallow aquatic environments. Quantifying these fluxes at the scale of a lagoon is a challenge, especially when sediments are heterogeneous and fluxes at the sediment-water interface combine diffusive and advective transport processes. Diagenetic processes and associated benthic fluxes were quantified across different seasons in a lagoon of the French Mediterranean coast (La Palme lagoon) from vertical profiles of pore water and sedimentary solid fraction carried out at many representative stations of the lagoon. The northwestern part of the lagoon is covered with fine-grained sediment with low permeability and the rest of the lagoon contains permeable sandy sediment. We obtained vertical profiles with centimetre-scale resolution of water content, salinity, and major particulate and dissolved biogenic compounds of C, N, P, Si, S, Fe and Mn. This study allowed us to refine the sedimentary mapping of the lagoon, to specify the spatio-temporal evolution of biogeochemical processes, and to determine more precisely the part of the diffusive fluxes of nutrient compared to advective fluxes. Comparison of the vertical profiles with a molecular diffusion transport model shows that molecular diffusion is the dominant process in fine-grained sediments, while sandy sediments are dominated by advection due to circulation of lagoon water in shallow sediments. Benthic respiration renders fine-grained and sandy sediments anoxic from the first few mm below the sediment-water interface, particularly due to the availability of labile organic matter. Benthic dissolved inorganic nitrogen fluxes are of the same order of magnitude in both sediment types, despite the different flux mechanisms. This suggests that the intensity of organic matter mineralization processes is the same in fine and sandy sediments. Benthic phosphate fluxes are greater in sandy than in fine sediments because phosphorus is more efficiently retained in the solid fraction of fine sediments. Thus, sandy sediments play a dominant role in the pelagic-benthic coupling of the lagoon.

Potential linkage between WWTPs-river-integrated area pollution risk assessment and dissolved organic matter spectral index.

The direct discharge of wastewater can cause severe damage to the water environment of the surface water. However, the influence of dissolved organic matter (DOM) present in wastewater on the allocation of DOM, nitrogen (N), and phosphorus (P) in rivers remains largely unexplored. Addressing the urgent need to monitor areas affected by direct wastewater discharge in a long-term and systematic manner is crucial. In this paper, the DOM of overlying water and sediment in the WWTPs-river-integrated area was characterized by ultraviolet-visible absorption spectroscopy (UV-vis), three-dimensional excitation-emission matrix combined with parallel factor (PARAFAC) method. The effects of WWTPs on receiving waters were investigated, and the potential link between DOM and N, P pollution was explored. The pollution risk was fitted and predicted using a spectral index. The results indicate that the improved water quality index (IWQI) is more suitable for the WWTPs-river integration zone. The DOM fraction in this region is dominated by humic-like matter, which is mainly influenced by WWTPs drainage as well as microbial activities. The DOM fractions in sediment and overlying water were extremely similar, but fluorescence intensity possessed more significant spatial differences. The increase in humic-like matter facilitates the production and preservation of P and also inhibits nitrification, thus affecting the N cycle. There is a significant correlation between DOM fraction, fluorescence index, and N, P. Fluorescence index (FI) fitting of overlying water DOM predicted IWQI and trophic level index, and a(254) fitting of sediment DOM predicted nitrogen and phosphorus pollution risk (FF) with good results. These results contribute to a better understanding of the impact of WWTPs on receiving waters and the potential link between DOM and N and P pollution and provide new ideas for monitoring the water environment in highly polluted areas.

Harmful algae diversity from a coastal upwelling system detected by high-throughput sequencing

IntroductionIn recent years, environmental DNA (eDNA) amplicon sequencing has been used to unveil plankton diversity in the field. Nevertheless, molecular methods, such as this, are rarely used in harmful algal bloom (HAB) monitoring programs, which mainly rely on morphological identification by conventional light microscopy.MethodsThe present study focused on a shallow marine environment (Ría de Vigo, Northwest Spain), where sediment and plankton samples were collected from 2016 to 2018.ResultsThe application of eDNA amplicon sequencing allowed us to simultaneously detect 25 potential harmful species (mainly diatoms and dinoflagellates) included in the IOC-UNESCO Taxonomic Reference List of Harmful Microalgae. Among these, causative agents of amnesic shellfish poisoning (Pseudo-nitzschia spp.) paralytic shellfish poisoning (Gymnodinium catenatum and Alexandrium minutum), azaspiracid producers (Azadinium poporum) and ichthyotoxic haptophytes (Chrysochromulina leadbeateri), were identified. Some toxic microalgae were better represented in sediment (e.g., Pseudo-nitzschia pungens, Gymnodinium catenatum) or planktonic fractions (e.g., Pseudo-nitzschia, Gymnodinium smaydae), confirming the importance of including both sediment and plankton fractions in eDNA monitoring studies. Despite the limitations of sequencing short amplicons, it was possible to discern in this study six Pseudo-nitzschia species and associate each of them with each seasonal peak produced in summer periods. Furthermore, several species previously unreported in Ría de Vigo (Pseudo-nitzschia turgidula, Chrysochromulina leadbeateri, Azadinium poporum) could be detected.DiscusionThese results point out the application of eDNA amplicon sequencing to expand our knowledge about harmful species in HAB monitoring programs and early warning systems for low abundant and rare taxa.

Fractionation, bioavailability and risk evaluation of phosphorus in lagoons surface sediments, Red Sea, Saudi Arabia

ABSTRACT In this study, eighteen surficial sediments were collected from two shallow lagoons of the Red Sea, King Saudi Arabia (Al-Shaibah and Al-Budhia lagoons), and analyzed for their grain size, CaCO3, and organic matter (O.M.) contents. The concentration of total phosphorus (TP), Organic-P (OP), and Inorganic-P (IP) were determined. In addition, Phosphorus bioavailability was also investigated by a sequential extraction procedure. The results of the current study showed variation in the levels of total phosphorus and the organic and inorganic form (TP, IP, OP). Al-Shaibah lagoon showed higher TP contents (274.78–389.24 and 265.91 ± 29.03 µgg-1) more than Al-Budhia lagoon (227.25–318.55 and 265.91 ± 29.03 µgg-1). The distribution of phosphorus bioavailability concentrations in the studied fractions in Al-Shaibah lagoon sediments was increased in the following order: hot H2O-P (0.10–0.25µgg−1) < NaHCO3-P (1.85–3.11 µgg−1) < exchangeable fraction (NH4Cl-P; 2.64–10.64 µgg−1) < Fe and Al-associated phosphorus (NaOH-P; 29.67–7.32 µgg−1). A similar order was observed in the Al-Budhia lagoon with slight differences in its content. The different fractions of the contribution of phosphorous bioavailability from the Total-P concentration were recorded as: NaOH-P (14.63–18.62%) >> NH4Cl-P (2.11–1.99%) > NaHCO3-P (0.75–1.04%) >H2O-P (0.05–0.09%). The phosphorus concentrations in the HCl-P fraction (calcium-associated phosphate/apatite) represent 32.67–59.60% of the total phosphorus in lagoon sediments.

Distribution and fractionation of metals in tropical estuarine sediments, NW Borneo: Implication for ecological risk assessment

Sediments were collected from 36 sites along the estuary of the Sibuti River in Sarawak, Malaysia, during the South-west and North-east monsoons, and then subjected to metal fractionation for Pb, Cd, Mn, Ba, Zn, Se, Co, Fe, Cu, Al and Cr. Metal concentrations were analyzed for 5 different fractions using the sequential extraction method. Pb, Mn and Cd possessed the greatest mobility, while major percentage of metals found were associated with residual fraction of sediments. Cd, Se and Cr, Fe were found dominantly associated with the carbonate and reducible fractions respectively, whereas Zn was found highly associated with oxidizable fraction of sediments. The factor analysis showed that the absorption of Mn in the upper part of estuary and most of the transition of metals in both seasons was regulated by the synthesis of Mn-oxyhydroxides catalyzed by microorganisms. On the other hand, association of organic matter with Fe and Al-oxyhydroxides work as major mechanism for absorption and settlement in intermediate and lower part of the estuary. Despite being associated with exchangeable fraction, Mn was found to be from geogenic sources along with all other metals except Cd, which is believed to be sourcing from agricultural lands. Ecological risk indices suggest that estuarine sediment is highly contaminated with Se, Co, Cu, Cd and pose considerable to very high risk at 90 % of the stations. Such enrichment is mainly resulting from the oxidation of metals from pyrite concretions and shale beds found in Sibuti and Lambir formations of the river basin. ERL and ERM values suggest Cu and Cr pose maximum threat towards the sediment dwelling living organisms. RAC reported Cd, Mn, Ba and Se in high risk category due to their potential to mobilize frequently, whereas Al, Fe and Cr present no risk towards benthic community.

Bioavailability and migration features of metals in “bottom sediments – water” system under the action of different environmental factors

This review considers and summarizes findings of the studies on metals’ coexisting forms in bottom sediments of surface water bodies. This makes it possible to assess metals’ migration ability in the “bottom sediments – water” system and their potential bioavailability for hydrobionts. The coexisting forms of metals in bottom sediments depend on their chemical properties and the component composition of the solid phase. Metals are distributed among exchangeable, carbonate, oxide, organic and residual fractions of bottom sediments. The highest migration ability is observed for metals contained in the first three fractions. Metals migration from organic and residual fractions hardly ever takes place. The oxygen regime, pH and redox potential, total dissolved solids and water temperature, concentration and component composition of organic substances affect the exchange of metals between bottom sediments and overlying water. The metal mobility in the “bottom sediments – water” system will increase under conditions of climate change. This is because cases of dissolved oxygen deficiency become more common, the total dissolved solids get higher in concentration, and pH and redox potential is reduced. Therefore, the development of methods to reduce metals migration from bottom sediments is a relevant task, which is discussed in the present paper.

Determination and evaluation of the ecological risk of mercury in different granulometric fractions of sediments from a public supply river in Brazil

This work reports the quantification of total mercury in sediments collected in periods with and without rain from the Joanes River, Bahia, Brazil. Determinations were made using Direct Mercury Analysis (DMA), the accuracy of which was confirmed with two certified reference materials. The highest total mercury concentrations were found at the sampling point close to commercial areas and large residential condominiums. On the other hand, the lowest levels were found in the site close to a mangrove region. The geoaccumulation index was applied to the total mercury results, evidencing low contamination in the region studied. The contamination factor showed that of the seven stations investigated, four samples collected in the rainy season showed moderate contamination. The results of the ecological risk assessment were utterly consistent with the contamination factor data. This study showed that the smaller sediment particles concentrate more mercury, corroborating what has been predicted by the adsorption processes.

Application of Persimmon Pectin with Promising Emulsification Properties as an Acidified Milk Drinks Stabilizer.

The present study aimed to evaluate the capability of persimmon pectin (PP) as a stabilizer for acid milk drinks (AMDs) compared with commercial high-methoxyl pectin (HMP) and sugar beet pectin (SBP). The effectiveness of pectin stabilizers was assessed by analyzing particle size, micromorphology, zeta potential, sedimentation fraction, storage, and physical stability. Results of CLSM images and particle size measurements showed that PP-stabilized AMDs had smaller droplet sizes and more uniform distributions, indicating better stabilization potential compared with the HMP- and SBP-stabilized AMDs. Zeta potential measurements revealed that the addition of PP significantly increased the electrostatic repulsion between particles and prevented aggregation. Moreover, based on the results of Turbiscan and storage stability determination, PP exhibited better physical and storage stability compared with HMP and SBP. The combination of steric repulsion and electrostatic repulsion mechanisms exerted a stabilizing effect on the AMDs prepared from PP. Overall, these findings suggest that PP has promising potential as an AMD stabilizer in the food and beverage industry.

SEDIMENTAZIONE PLEISTOCENICA DELL'ATLANTICO ORIENTALE FRA 30° E 10° LATITUDINE NORD E 37° E 13° LONGITUDINE OVEST

Planktonic foraminiferal microfaunas contained in Pleistocene samples from 60 cores of the L-DGO collection, recovered during several VEMA cruises in che castern North Atlantic Ocean are considered. Cores range in depth from -958 meters to -5755 meters. These samples have been divided into homogeneous groups according to location and bathymetry. Three areas could be recognized with different sedimentological characters. 1) The northern area, between 30° and 21° latitude N, contains samples which are not very disturbed by displacement, so that dissolution of foraminiferal tests is directly correlated to depth. A comparison with the dissolution facies previously defined has been attempted for these samples, where the eolytic and the mesolytic facies can be distinguished, while the alytic facies is absent. 2) The area encompassing the Cape Verde-Madeira and Gambia abyssal plains includes samples from depths in excess of 5000 meters: the pleistolytic and the hololytic facies are represented here. E-W transects of progressively deeper cores point out the relation between depth and dissolution. SEM photo­graphs of the sediment fraction greater than 63 microns document the various dissolution facies identified. 3) The southern area, ranging from 21° to 10° latitude N, is characterized by sediments in which the effects of volcanism, intense displacement and deep cold water upwelling coexist, expecially near Cape Verde, with an increase of siliccous organisms. Dissolution is hidden by resedimentation, which seems to be one of the dominane aspects of this area.

Titanium transport and isotopic fractionation in the Critical Zone

Stable Ti isotopes have been applied in the detrital sediment record to reconstruct the bulk composition of Earth’s continental crust due to the relationship between magmatic differentiation and Ti isotopic compositions. However, no study has systematically evaluated the influence of provenance, physical, and chemical weathering on the composition of sediments relative to the protolith they originated from. To test the influence of these processes on Ti isotopic compositions we investigate the Ti isotope composition of 82 surface samples including loess, volcaniclastic rocks, river sediment, and two separate weathering profiles through igneous rocks, collected from a broad geographical area and a range of environmental conditions. Limited but significant Ti isotope fractionation exists in samples subjected to extreme chemical weathering processes, potentially as a result of elemental mobilization. For example, the δ49Ti isotopic composition of bauxites developed on Columbia River basalt varies by up to 0.1‰, becoming isotopically heavier with increasing weathering intensity. However, negligible variation in δ49Ti was found in a second profile of saprolites developed on weathered diabase. Titanium isotope variations in loess do not correlate with chemical weathering intensity or size sorting, but may instead be related to the provenance of the sediment. We find that the δ49Ti of Amazon River sediments is correlated with the Al/Zr ratio, indicating that δ49Ti is impacted by sediment sorting. At our study sites, the river averaged offset between the isotopic composition of the bedload and the suspended sediment fraction is 0.051‰, with the largest offset being + 0.116‰. Our data suggest that during chemical weathering, heavy Ti isotopes are preferentially incorporated into secondary minerals producing higher δ49Ti in intensely weathered soils. During fluvial transport, the Ti isotopic composition of fine-grained sediment is heavier than that of its coarser counterpart. Crustal protolith composition and sorting during transport and sedimentation have a stronger effect on the Ti isotopic composition than chemical weathering. Our results have implications for studies that utilize the Ti elemental concentration to calculate relative enrichment or depletion during chemical weathering and physical transport processes in the Critical Zone and for studies using Ti isotopes in terrigenous sediments to infer the composition of their provenance.

Effective thermal conductivity of a gypsum mortar using harbor sediments

For sustainable use of natural resources, marine sediments areregularly dredged. One of the valorization ways of thesesediments is to reuse them as raw materials for the formulation of civil engineering products.This paper presents a thermal homogenization methodology for the optimization of heat transfer in Gypsum Plaster Boards formulation using dredged marine sediments. An up-scaling or homogenization technique that links macro- to micro thermal conductivity is given. Effective homogenized thermal conductivity formulation could be presented for a composite material on which a periodic micro-scale heat flux was subjected. For that purpose, steady state balance equations and Fourier heat law were used. Then, a thorough characterization of grain size distributions of dredged sediments were carried out. This showed that the dredged sediments are mainly sandy. Finally, ANSYS Finite Element Code is used to numerically compute the effective homogenized thermal conductivity of Gypsum-sediment composite incorporating different volume fractions of sediments. These simulations, performed on the Representative Volume Element, allowed studying the influence of the sediment grain size. The numerical simulations results, compared to classical theoretical models, have demonstrated the reuse feasibility of investigated sediment in Gypsum Plaster applications.