Kg Of Sediment Research Articles

A bold new purpose for an old method: Using invertebrate kick‐netting to improve monitoring of microplastic pollution in running waters

AbstractFreshwaters are impacted by many pollutants. Scientists and resource managers need to reliably detect and monitor these pollutants by employing appropriate sampling techniques to quantify and mitigate their impacts. Emerging freshwater contaminants such as microplastics are difficult to monitor as effective sampling techniques have not been fully developed and lack standardization. Here, we propose a novel method, adapted from stream invertebrate kick‐net sampling, which can be employed for long‐term, standardized microplastic monitoring. We hypothesized that invertebrate kick‐net sampling would be effective at collecting microplastics, capturing higher microplastic concentrations than standard microplastic sampling, due to collecting suspended and benthic microplastics simultaneously. We sampled 28 streams for microplastics using standard drift and sediment microplastic collection methods and invertebrate kick‐netting. As predicted, kick‐netting captured microplastics at higher concentrations than conventional sampling, regardless of whether values were expressed per volume of water (as in drift samples), per kg of sediment or per area sampled (as in benthic samples). Consequently, kick‐net sampling has the potential to be a time‐ and cost‐efficient tool for monitoring microplastic pollution. We recommend the employment of invertebrate kick‐netting as a new, standardized means to investigate and routinely monitor microplastic concentrations worldwide. This would generate a more robust dataset of global freshwater microplastic pollution, making it possible to answer unresolved questions pertaining to changes in microplastic pollution profiles. Standardized, long‐term records of microplastic concentrations in freshwaters would also allow a more accurate assessment of the ecological risks of microplastic pollution. Finally, long‐term microplastic data could be used to inform much‐needed regulatory decisions pertaining to microplastic pollution.

Biochar for Improving Growth Performance of Shrimp and Environmental Quality in an Inland Saline Culture System.

The current study, which lasted 45 days, was designed to find a more effective way to use the vast resources of salt-affected land and ground saline water for aquaculture. Biochar made from agrowaste was used as a sediment amendment. The 100 g of biochar was applied to 25 kg of sediment (i.e., 9.0 ton ha-1) in 300L capacity fiber reinforced plastic, and Penaeus vannamei (P. vannamei) (2.74 ± 0.03 g) was stocked at 90 juveniles m-2 in inland ground saline water of salinity 10 ppt fortified with potassium levels that are 50% equivalent to those of seawater. Among different treatments, T1 indicates paddy straw biochar (PSB) application in sediment; T2 indicates sediment amended with KOH-activated PSB; T3 indicates sugar cane bagasse biochar (SBB) application in sediment; and T4 indicates sediment amended with KOH-activated SBB. Compared to the control the potassium (K+), alkalinity, total hardness, calcium/magnesium ratio, and pH of the water increased significantly (P ≤ 0.05) in treatments where biochar was used as an amendment in sediment. The T3 treatment had the best Ca/Mg ratio (1.00:3.12). In water, the magnitude of increase in K+ concentration from high to low followed the order: T2 > T4 > T1 > T3 > control. The concentration of NH4+-N in water was found to be increasing in control, whereas in the rest of the treatments, it decreased significantly from day 1, until the end of the experiment. Compared to control, the bulk density was decreased, and sediment cation exchange capacity and water holding capacity were increased significantly in treatments where biochar was used as an amendment. The soil microbial parameter measured in terms of soil enzyme dehydrogenase was significantly different among treatments at the end of the experiment. Weight gain (%), specific growth rate (SGR), survival (%), and feed conversion ratio of P. vannamei varied significantly in T1, T2, T3, and T4 compared to the control. The SGR (2.38b ± 0.05% day-1) and weight gain (%) in T2, and survival (96.1b ± 2.0%) in T3 treatment were found to be the highest at the end of the experiment. When biochar was mixed with sediment in the inland saline system, an improvement was seen in sediment quality, water quality, and growth characteristics of P. vannamei.

Chloride exchanges between oceanic sediments and seawater: Constraints from chlorine isotopes

We investigate the chlorine isotope disequilibrium between chlorides in pore fluids and chlorides in seawater and infer its consequences for chlorine isotope exchange between ocean sediment pore fluids and seawater. We illustrate our methodology with pore fluids from two IODP drilled to depths of ≈1000 m (U1456 and U1457) in the Indus River fan dominated by clay-detritus sediments of the western Himalayas. At these two sites, the concentrations of chloride and sodium ions do not show significant changes with depth and remain very close to those of seawater. As a function of depth, however, chlorides show a progressive decrease in 37Cl (downto −2.5 and −1.4 ‰ respectively), while Ca2+ increases and Mg2+ decreases, as commonly observed in clay-rich oceanic sediments. The rate of the δ37Cl decrease is correlated to the lithology and sedimentation rate. Examining the chlorine budget on these two sites, we conclude that: (1) Most of the chlorine (≥96% of the total Cl) is contained in the pore fluids as chlorides, while the chlorine stored in the other sinks (minerals or organochlorine) is generally very minor (representing <4% of the total Cl). (2) These other sinks are too small to sequester the lost 37Cl-enriched chlorine, which could compensate for the decreased δ37Cl of the chlorides observed in the pore fluids (assuming that the pore fluids originally had chlorides with the chlorine isotopic composition of seawater, δ37Cl = 0 ‰). (3) This lost 37Cl-enriched chlorine has been released from the sediment into the overlying seawater, with fluxes of about 20 mol of chloride per square metre per kiloyear.In order to evaluate the consequence of this unbalanced on a global scale, we extend this chlorine budget analysis to 22 other oceanic sites drilled by IODP in a variety of tectonic environments. It is estimated that worldwide oceanic sediment pore fluids contain 1 × 1020 mol of chloride with mean δ37Cl at −2.3 ± 0.1 ‰ and mean chlorinity at 0.290 ± 0.055 mol Cl- per kg of sediment. Most of the calculated values of the lost 37Cl-enriched chlorine flux are between 3.5 and 45.6 mol of chloride per square metre per kiloyear (mean value of 18.3 mol Cl.m−2.kyr−1), corresponding to a typical chloride exchange time between sediments and seawater of between 5.5 and 71 Myr with a mean value of 14 Myr. Importantly, in oceanic sediments, a relationship between the δ37Cl of the chlorides in their pore fluids and the nature of the detrital minerals (smectite, illite, kaolinite, carbonate, quartz, …) may exists. This relationship should be modulated by the detrital input from the continents to the oceanic sediments and should therefore be a consequence of the climatic conditions on the continents (mainly rain, temperature). The δ37Cl of the seawater should vary according to these detrital inputs. The expected range of variation would be between −0.3 and +0.3 ‰. This is consistent with the range of δ37Cl in seawater predicted by the study of evaporites deposited since 2 Ga (Eggenkamp et al., 2019).

A marine microvertebrate fauna from a temporary exposure of the Atherfield Clay Formation, Reigate, Surrey

A temporary exposure of the nearshore marine Atherfield Clay (Lower Greensand Formation, Aptian, Early Cretaceous) in the Reigate area (Wonham Mill) of Surrey was sampled for microvertebrate remains in Autumn 2013. Samples amounting to 858 kg of sediment were washed, dried, and sieved to 0.325 mm and the residue searched for all fossil content. This is the first definitive study of the Atherfield Clay chondrichthyan fauna of Surrey. The samples yielded teeth of hybodont sharks (Planohybodus ensis, Lonchidion breve), neoselachian sharks (Heterodontus sulcatus, Cretascyllium hassei, Protospinax sp., Protolamna sokolovi, Lamnid indet., Scyliorhinus muelleri, Scyliorhinus gen. et sp. indet., Protoscyliorhinus sp.) and batoids (Belemnobatis picteti, Squatirhina sp.). The neoselachian sharks and rays all constitute the first confident records for the various genera in the Atherfield Clay of the United Kingdom. Dermal denticles and bony fish teeth are also present in the samples, which also yielded small numbers of invertebrates (ammonite and crustacean), microcoprolites (Tomaculopsis tomaculopsis) and plant remains (fern indusia). The state of preservation of the chondrichthyan material suggests that none of the specimens are derived from older strata; the fauna is indigenous. The Surrey Atherfield Clay fauna is distinct from that recorded from the Atherfield Bone Bed on the Isle of Wight and the roughly coeval boreal fauna of the Speeton Clay.

Fossil micrometeorites from Monte dei Corvi: Searching for dust from the Veritas asteroid family and the utility of micrometeorites as a palaeoclimate proxy

We searched late Miocene sedimentary rocks in an attempt to recover fossil micrometeorites derived from the Veritas asteroid family. This study was motivated by the previous identification of a pronounced 3He peak (4-5x above background) within marine sediments with ages between ∼8.5–6.9 Ma ago (Montanari et al., 2017. GSA Bulletin, 129:1357–1376). We processed 118.9 kg of sediment from the Monte dei Corvi beach section (Italy), the global type-section for the Tortonian epoch (11.6–7.2 Ma). Samples were collected both before and within the 3He peak. Although a small number of iron-rich (I-type) fossil micrometeorites were recovered from each horizon studied (Ntotal = 20), there is no clear difference between the pre- and intra- 3He peak samples. All micrometeorites are compositionally similar, and three out of five horizons yielded similar abundances and particle sizes. Micrometeorites extracted from sediments at the base of the 3He peak were exclusively small (ø <75 µm), while micrometeorites extracted from sediments near the highest 3He values were relatively large (ø <270 µm). The recovered fossil micrometeorites are interpreted as samples of the background dust flux derived from metal-bearing chondritic asteroids. The presence of a 3He signature combined with the absence of fossil micrometeorites or extraterrestrial spinels (Boschi et al., 2019, Spec. Pap. Geol. Soc. Am. 542:383–391) unambiguously related to the Veritas event suggests that the Veritas family is composed of highly friable materials that rarely survive on the sea floor to become preserved in the geological record. Our data supports the existing hypothesis that the Veritas asteroid family is an aqueously altered carbonaceous chondrite parent body, one that contains minimal native metal grains or refractory Cr-spinels. The low yield of fossil micrometeorites at Monte dei Corvi is attributed to loss of particles by dissolution whilst they resided on the sea floor but also due to high sedimentation rates leading to dilution of the extraterrestrial dust flux at this site. As with other fossil micrometeorite collections (e.g. Cretaceous chalk [Suttle and Genge, EPSL, 476:132–142]) the I-type spherules have been altered since deposition. In most particles, both magnetite and wüstite remain intact but have been affected by solid state geochemical exchange, characterised by partial leaching of Ni, Co and Cr and implantation of Mn, Mg, Si and Al. In some particles Mn concentrations reach up to 16.6 wt%. Conversely, in some micrometeorites wüstite has been partially dissolved, or even replaced by calcite or ankerite. Finally, we observe evidence for wüstite recrystallisation, forming a second generation of magnetite. This process is suggested to occur by oxidation during residence on the seafloor and has implications for the use of fossil I-type micrometeorites as a potential proxy for probing Earth’s upper atmospheric composition (oxidative capacity) in the geological past. However, solutions to the limitations of post-depositional recrystallisation are suggested. Fossil I-type spherules remain a potential tool for palaeo-climatic studies.

Integrative Evaluation of the Ecological Hazards by Microplastics and Heavy Metals in Wetland Ecosystem.

This study was performed to evaluate the impact of microplastics and heavy metals (Pb, Cd, Cr, Cu, Zn, Ni) on sediments, water, aquatic plants (Pistia stratiotes, Alternanthera philoxeroides, and Ipomoea carnea), and fish (Labeo rohita) samples collected from five different sites in the Bajwat wetlands in Sialkot, Pakistan. The concentrations of Pb, Cd, and Cr were above the permissible limits devised by WHO in all the ecosystem components (i.e. sediments, water, plants, and fish) at all sites. The maximum amount of microplastic particles (2317 microplastic particles per kg of sediments) was recorded at Site 1. The filaments were the most commonly found type of microplastics. Plants and fish samples also showed considerable concentration of metals. The multivariate statistical analysis revealed anthropogenic sources of elevated concentrations of metal elements which could cause adverse biological effects in the ecosystem.

A marine plastic cloud - Global mass balance assessment of oceanic plastic pollution

To improve our understanding and management of marine plastic pollution of the ocean, a total plastic budget is needed which quantifies the sources and sinks, as well as inputs and removal of plastic per unit time. The current state of knowledge indicates that the coastal zone and ocean water column are major locations for plastic pollution, but the fate of much of this must ultimately be the deep ocean floor. We reviewed 23 journal articles that provide 280 observations of deep-sea sediment microplastic concentration across six different off-shelf environments. We calculate the following mean concentrations of microplastic particles (number) per kg of sediment: continental slope 502; submarine canyons 784; submarine fans and continental rise 714; abyssal plains 217; trenches and troughs 2782; and abyssal hills, mountains and other ocean floor 165 particles kg−1. These figures are alarming because several exceed one estimate of ‘safe’ levels of microplastic concentration for benthic marine life (540 particles kg−1). Monitoring of the concentration of plastic particles in sediments of submarine canyons, fans and continental rise environments and in trenches and troughs should be a priority to ensure efficacy of policies and actions taken to curb ocean plastic pollution at both the national and global level. We estimate 3.05 million tonnes of microplastic resides in deep ocean sediments but acknowledge the uncertainties of this figure. If correct, this figure implies that the ocean water column (which may contain as much as 90 million tonnes of microplastic) is a major, transitory sink for MP, forming a suspended, marine plastic cloud. In addition to particle concentrations, further measurements of the size and mass of microplastic in deep-sea sediments and in the water column are needed to advance development of mass balance budgets for marine plastic pollution.

A Method for Detrital Corundum Characterization in Sediments: Case Study of the Gem Mountain Mine Placer Sapphire Deposit (Rock Creek, Montana, USA)

AbstractA new, comprehensive approach to characterizing detrital corundum in sediments and placer deposits is outlined and applied to a sample of poorly sorted, mud-supported colluvium rich in rhyolite tuff clasts from the sapphire-producing layer at Gem Mountain Mine, Rock Creek, Montana. High angularity and the predominance of inherited surface features indicate that corundum was not abraded during transport, consistent with deposition by mass wasting. Corundum grain abundances per 10 kg of sediment (rounded to nearest whole number) are as follows: 4–8 mm (1 grain), 2–4 mm (12 grains), 1.0–2.0 mm (10 grains), 0.5–1.0 mm (43 grains), 0.25–0.50 mm (90 grains), 0.125–0.250 mm (480 grains), and &amp;lt;0.125 mm (55 grains; underrepresentation due to poor recovery). The ∼ 50× abundance of corundum in &amp;lt;2 mm size fractions relative to the &amp;gt;2 mm size fraction of potential economic interest suggests that fine-grained corundum may have potential as a pathfinder for gem corundum deposits in heavy mineral surveys. Corundum grains are transparent and divided into four types by surface texture and extent of crystal face development: (1) rounded with frosted surface, anhedral/subhedral; (2) angular with hillocky/irregular surface, anhedral/subhedral; (3) angular subhedral grains with glassy curved faces; and (4) angular, idiomorphic blue grains (all &amp;lt;1 mm). Surface texture Types 1–3 occur in pastel-colored corundum (green, yellowish-green, yellow, colorless) and are the result of dissolution subsequent to euhedral crystal growth. Mineral inclusions in corundum include: pastel corundum – biotite (variable Fe, Mg, Ti, F contents), plagioclase feldspar (andesine-labradorite), rutile, hercynite; blue corundum – alkali feldspar, rutile, zircon, ilmenite, apatite, spinel. Corundum uncommonly occurs in composite grains with biotite, plagioclase, and K-feldspar. Rhyolite occurs as a partial encrustation on one corundum grain. Rock Creek corundum may have originated from partially melted metapelite in a metamorphic basement, and incorporated and transported to the surface by rhyolitic magmas. Due to scant geologic context and an absence of radiometric age data, the proposed genetic model remains highly speculative.

Can Woodchip Bioreactors Be Used at a Catchment Scale? Nitrate Performance and Sediment Considerations

Highlights Novel three-bed, cascading-inlet bioreactor treated agricultural drainage from a 249-ha catchment. Nitrate removal rates and load reduction efficiencies were similar to those of traditional single-field bioreactors. Sedimentation problems reduced bed life; a sediment sensing and exclusion system solved them. This scale provides opportunities for centralized management and nutrient reduction verification. Abstract. Denitrifying bioreactors, a structural practice deployed at the field scale to meet water quality goals, have been underutilized and require additional evaluation at the small catchment scale. The objective of this study was to quantify the performance of a large, multi-bed denitrifying bioreactor system sized to treat agricultural drainage runoff (combined drainage discharge and surface runoff) from a 249-ha catchment. Three woodchip bioreactor beds, 7.6 m wide by 41 m long by 1.5 m deep, with cascading inlets, were constructed in 2016 in southern Minnesota, U.S. The beds received runoff for one water year from a catchment area that is 91% tile-drained row crops, primarily maize and soybeans. Initial woodchip quality differed among the three beds, affecting flow and nitrate removal rates. Bioreactor flow was unimpeded by sediment for twelve events from September 2016 to July 2017, during which time 55% of the discharge from the catchment was treated in the bioreactor beds. Average daily nitrate removal rates ranged from 2.5 to 6.5 g-N m-3 d-1 for the three bioreactor beds, with nitrate-N load removal of flow through the beds between 19% and 27%. When accounting for untreated by-pass flow, the overall nitrate-N removal of the multi-bed system was 12.5% (713 kg N). During high-flow events, incoming sediment clogged the reactor beds, decreasing their performance. There was 4,520 kg of sediment trapped in one bed, and evidence suggests the other two trapped a similar load. To solve this problem and prolong the bioreactor’s lifespan, we installed a shutoff gate that activated when inflow turbidity exceeded a threshold value. Finally, the findings indicate that catchment-scale denitrifying bioreactors can successfully remove nitrate load from agricultural runoff, but sediment-prevention measures may be required to extend the bioreactor's lifespan. Keywords: Bioreactor, Denitrification, Nitrate removal, Sedimentation, Subsurface drainage.

Impact of Coastal Sediments of the Northern Dvina River on Microplastics Inputs to the White and Barents Seas

The Northern Dvina River flowing into the White Sea may be one of the main sources of microplastic (MP) pollution in the Arctic region. The coastal sediments of the Northern Dvina River act as an intermediate link in the transport of microplastics to the areas of the White and Barents Seas. The µFT-IR and Py-GC/MS methods were used to determine that up to 200 particles or 120 mg of MP per kg could accumulate in the coastal sediments of the Northern Dvina River. Coastal sediments tend to accumulate ABS and PS plastic particles with a particle size of around 200 µm. The accumulated microplastics (218 particles or 117 mg per kg of sediment per year) are carried away by strong currents, especially during spring flooding, resulting in pollution of the Barents and White Seas. The obtained data play an important role in assessing the MP pollution of the Arctic region, especially the White and Barents Seas.

Biogeography of northeastern Atlantic Neogene chitons (Mollusca, Polyplacophora): New data from the Pliocene of Portugal

AbstractBased on extensive new material, 2088 valves resulting from search sampling of ~500 kg of sediment, the Pliocene chiton biodiversity of the Mondego Basin (Portugal) is reassessed. Twelve species were identified, assigned to seven genera. Eight species are new for the Pliocene of Portugal, as well as two of the genera: Hanleya, Acanthochitona. Two taxa are described as new: Ischnochiton loureiroi n. sp. and Lepidochitona rochae n. sp. Until now, the polyplacophoran European Neogene record was too poorly known to be of help in generating a clear picture of the Miocene to present-day biogeography of the group. This new wealth of data from western Iberia, in conjunction with recent data from the Loire Basin Upper Miocene assemblages (France), allows clarification the Late Miocene to Recent eastern Atlantic and Mediterranean biogeography of the Polyplacophora. The northern range of warm-water northeast Atlantic and Mediterranean Polyplacophora experienced a sharp contraction since, at least, Late Miocene to Early Pliocene times. Warm-water chiton species represented in the Upper Miocene of the Loire Basin of NE France (European-West African Province) and the Pliocene of the Mondego Basin of central-west Portugal (Pliocene French-Iberian Province) are today confined to the southern Mediterranean-Moroccan Molluscan Province.UUID: http://zoobank.org/a2a550c0-caed-449a-aa45-9492c45f882e

High‐frequency monitoring of hydrological and biogeochemical fluxes in forested catchments of southern Chile

AbstractThe variability of rainfall‐dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet‐temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad‐leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old‐growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad‐leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history.

Revealing the effects of cerium dioxide nanoparticles through the analysis of morphological changes in Chironomus riparius

Due to their many practical applications, engineered cerium dioxide (CeO2) nanoparticles (NPs) are commonly used today, although there are justified concerns about the environmental risks of their usage. Studies to date have shown that CeO2 NPs do not pose a lethal hazard to hydrobiocenoses at environmentally relevant concentrations, but that they induce significant negative sublethal effects. Therefore, intensive work is being done on the adaptation of standard ecotoxicological tests with the development of new, sublethal biomarkers. The present study aims to examine the sublethal effects of prolonged exposure to CeO2 NPs (2.5; 25; 250 and 2500 mg of CeO2 NPs per 1 kg of sediment) on the morphological features of the non-biting aquatic midge Chironomus riparius. Morphological variation was examined by means of two approaches: (1) Deformity rate analysis (analysis of visible morphological malformations) and (2) Geometric morphometric analysis (analysis of differences in the size and shape of the larval mandibles and mentums, as well as adult male and female wings). Changes in all the morphological structures examined were observed using a geometric morphometric approach at low and very high concentrations of CeO2 NPs (2.5 and 2500 mg of CeO2 NPs per 1 kg of sediment). The potential reduction of sexual dimorphism resulting from downsizing of the wings in females was observed. These results indicate that the sublethal changes observed in chironomids exposed to CeO2 NPs are significant and may potentially lead to further changes in metabolism, diet and behavior, which may lead to repercussions of as yet unexamined proportions. Considering our findings, and the advantages of geometric morphometrics (precision, uniformity, accurate qualification, quantification, and visualization of fine morphological changes), this approach is proven to be an exceptional assessment tool, with great applicative potential in the ecotoxicological testing of nanoparticles.

Direct Mercury Analyzer (DMA) determination of mercury distribution in the sediments of lake Nokoué in Benin Republic-West Africa

Mercury pollution of water bodies constitutes a hazard to both the aquatic life and the populations consuming fishery products. To anticipate the probable eco-toxicological risks that may arise from the largest lake in southern Benin, the present work aims at assessing the mercury status of the sediments of Lake Nokoué, while identifying the areas exposed to anthropogenic mercury contamination. 45 sites were sampled according to a grid plan covering the entire ecosystem of the lake. Employing a Van Veen grab, surface sediments are collected at a depth from 0 to 5 cm in three catches at each site. The composite samples formed at equal mass on the three portions were frozen, lyophilized at - 40 °C, crushed, sieved and homogenized. Fraction less than 63 µm was collected for the mercury content determination by Direct Mercury Analyzer (DMA) operating by atomic absorption according to the US EPA 7473 method. The mercury concentration varies from 1.56 µg/kg to 164.88 µg/kg with an average value of 35.18 µg per kg of sediment. The south-eastern zone of the lake is more concentrated in mercury with a summation of the mercury content of 530.3 µg/kg of sediment. However, the lake has moderate contamination overall (1 ≤ FC ≤ 3).&#x0D; Keywords: Pollution, contamination, mercury, sediment, Lake Nokoué.

Culturable fungi from dredged and marine sediments from six ports studied in the framework of the SEDITERRA Project

Mycological characterisation of marine and dredged sediments consists of the isolation of vital and culturable fungal strains as well as their identification and analysis, in order to increase knowledge of sediment mycobiota and isolated species that can be employed in biotechnological processes. Our study undertook the mycological characterisation of sediments from six different port environments: marine bottom sediments from the ports of Genoa (Liguria, Italy) and Centuri (Corsica, France), dredged sediments (sediments removed from the sea bottom) from landfill sites (contaminated land sites where dredged sediments are deposited) of the ports of Leghorn (Tuscany, Italy) and Cagliari (Sardinia, Italy), bottom muds from the brackish environment of the navigable Navicelli Canal of Pisa (Tuscany, Italy) and dredged marine sediments from a temporary storage site in the port of Toulon (Var, France). At each site, 30 kg of sediment was sampled for physical, chemical and mycological analyses. They were analysed in terms of grain size composition, organic and inorganic content, metal concentration and hydrocarbon and polychlorinated biphenyl concentration. Fungi were then isolated from sediments by a modified dilution plate technique from 1:10 up to 1:100. Fungal identification was carried out using a morphological and molecular polyphasic approach. Forty-six fungal species belonging to 20 genera were isolated. The highest biodiversity was found in Leghorn (14 species), Genoa (11) and Cagliari (11) sediments, while very low numbers of species were isolated from the ports of Centuri (3) and Toulon (4). Similarly, the number of colony-forming units (CFUs), calculated on the dry weight of the sediments, followed this order: Genoa (3,765 CFUs*g-1) > Leghorn (1,370 CFUs*g-1) > Pisa (1,190 CFUs*g-1) > Cagliari (410 CFUs*g-1) > Toulon (380 CFUs*g-1) > Centuri (220 CFUs*g-1). The most represented genera were Penicillium, Aspergillus and Trichoderma. Some halotolerant species known for their biotechnological properties were isolated: Emericellopsis maritima, Cladosporium halotolerans and Aspergillus micronesiensis. A potential marine pathogenic fungus was found: Aspergillus sydowii. This work increased knowledge of fungi from marine and dredged sediments in six Mediterranean ports in the framework of the SEDITERRA Project.

A review of microplastic distribution in sediment profiles

The growing use of plastic and their indiscriminate disposal into the environment has resulted in the accumulation of huge quantities of microplastic (MP) in the marine environment. Several studies have investigated the pathways of MPs reaching marine environments and a few have begun looking at their inventories in sediment profiles. Recent estimates suggest between 70 and 90% of the MP particles are accumulated into sediment profiles. This paper reviews MPs in sediment cores, and the methods used for chronological reconstruction to provide evidence to link the plastic usage and MP inventories over time. In one example, a 210Pb dated sediment core from Kuwait Bay revealed 0.1 MPs g−1 of sediment deposited in approximately 1951 and 0.5 MPs g−1 in sediment from 2009 indicating a progressively increasing presence in recent sediments. The review also highlights the issue of very large spatio-temporal variation in MP concentrations, indicating the limitation of a snapshot study especially when dealing with the surface sediments; and it demonstrates the relevance of using sediment cores for a better assessment of MP input and inventories in the marine environment. It is proposed that MP sediment data should be reported as N m−2 year−1 or g m−2 year−1, and cores preferably dated using 210Pb, and supported by at least one other stratigraphic marker to enhance the usefulness of these datasets, since 210Pb can reliably date sediments as old as 100 years, a time-span which extends well beyond the time plastic production began. The anomalies in data processing and reporting in terms of number per kg of sediment or per cm2/m2 should be addressed essentially by adopting a standardized protocol.

Long-term measurements of aeolian transport directional variations over a zibar surface in the northern Kumtagh Sand Sea

Zibars are aeolian bedforms created by armoring of the surface by coarse grains. The existence and movement of these grains strongly influence zibar morphodynamics. Although aeolian sediment transport has been investigated for arid surface processes with a range of grain sizes, the measurement durations were short, making it difficult to establish the relationship between microscopic aeolian transport processes and macroscopic geomorphological processes. In the present study, we conducted field observations of aeolian sediment transport above a zibar in northern China's Kumtagh Sand Sea with a segmented sand trap. During six measurement periods throughout 2014, the sampler collected 314.76 kg of sediments within 1 m above the ground. The directional variation indicated that about 52.5% of the sediments came from the north, northeast, and northwest; the southeast provided the least sediments. The strongest aeolian transport occurred between August and October; the weakest was in winter. The aeolian sediment flux decreased with height, and 54% of particles were transported within 0.1 m above the ground. The transport profiles fit an exponential decay function. The flux's directional variation resulted from the combined effects of sediment availability and wind regime, so the calculated net transport differed from the drift potential. The seasonal and directional variations of aeolian transport significantly affect the morphodynamic process of zibars. The trend and the internal sedimentary structure of zibars were closely related to the aeolian transport process.

Quantifying sediment mass redistribution from joint time-lapse gravimetry and photogrammetry surveys

Abstract. The accurate quantification of sediment mass redistribution is central to the study of surface processes, yet it remains a challenging task. Here we test a new combination of terrestrial gravity and drone photogrammetry methods to quantify sediment mass redistribution over a 1 km2 area. Gravity and photogrammetry are complementary methods. Indeed, gravity changes are sensitive to mass changes and to their location. Thus, by using photogrammetry data to constrain this location, the sediment mass can be properly estimated from the gravity data. We carried out three joint gravimetry–photogrammetry surveys, once a year in 2015, 2016 and 2017, over a 1 km2 area in southern Taiwan, featuring both a wide meander of the Laonong River and a slow landslide. We first removed the gravity changes from non-sediment effects, such as tides, groundwater, surface displacements and air pressure variations. Then, we inverted the density of the sediment with an attempt to distinguish the density of the landslide from the density of the river sediments. We eventually estimate an average loss of 3.7 ± 0.4 × 109 kg of sediment from 2015 to 2017 mostly due to the slow landslide. Although the gravity devices used in this study are expensive and need week-long surveys, new instrumentation currently being developed will enable dense and continuous measurements at lower cost, making the method that has been developed and tested in this study well-suited for the estimation of erosion, sediment transfer and deposition in landscapes.

Bioenergetic characterization of a shallow-sea hydrothermal vent system: Milos Island, Greece.

Shallow-sea hydrothermal systems, like their deep-sea and terrestrial counterparts, can serve as relatively accessible portals into the microbial ecology of subsurface environments. In this study, we determined the chemical composition of 47 sediment porewater samples along a transect from a diffuse shallow-sea hydrothermal vent to a non-thermal background area in Paleochori Bay, Milos Island, Greece. These geochemical data were combined with thermodynamic calculations to quantify potential sources of energy that may support in situ chemolithotrophy. The Gibbs energies (ΔGr) of 730 redox reactions involving 23 inorganic H-, O-, C-, N-, S-, Fe-, Mn-, and As-bearing compounds were calculated. Of these reactions, 379 were exergonic at one or more sampling locations. The greatest energy yields were from anaerobic CO oxidation with NO2- (-136 to -162 kJ/mol e-), followed by reactions in which the electron acceptor/donor pairs were O2/CO, NO3-/CO, and NO2-/H2S. When expressed as energy densities (where the concentration of the limiting reactant is taken into account), a different set of redox reactions are the most exergonic: in sediments affected by hydrothermal input, sulfide oxidation with a range of electron acceptors or nitrite reduction with different electron donors provide 85~245 J per kg of sediment, whereas in sediments less affected or unaffected by hydrothermal input, various S0 oxidation reactions and aerobic respiration reactions with several different electron donors are most energy-yielding (80~95 J per kg of sediment). A model that considers seawater mixing with hydrothermal fluids revealed that there is up to ~50 times more energy available for microorganisms that can use S0 or H2S as electron donors and NO2- or O2 as electron acceptors compared to other reactions. In addition to revealing likely metabolic pathways in the near-surface and subsurface mixing zones, thermodynamic calculations like these can help guide novel microbial cultivation efforts to isolate new species.

Recycling contaminated marine sediments as filling materials by pilot scale stabilization/solidification with lime, organoclay and activated carbon

Nowadays, stabilization/solidification (S/S) applied to the treatment of contaminated marine sediments (CMSs) represents a key technology for the production of new materials for civil engineering. Literature has shown the feasibility of CMSs recycling, although sediment needs pre-treatments for the removal of organic matter and to improve the mechanical properties of the product post S/S. In view of the full-scale applicability where it is essential to reduce any additional phase (i.e., pre-treatments), this study is aimed at demonstrating the technical feasibility of recycling CMSs as filling materials by S/S treatments with lime, organoclay and activated carbon. The original sediments are contaminated with heavy metals, PCBs, and PAHs, exceeding limits values prescribed by law. Different mixtures were tested on the STABSOL-P pilot scale plant. The absence of specific CMSs pre-treatments resulted in failure to comply with the 28-days leaching test only for copper; greater air curing with 56-days allowed it to be complied with for all the investigated metals. The organic contamination, while slowing down the process of chemical stabilization, allowed in any case to get a product environmentally compatible. The unconfined compression strength tests showed values (>28 kPa) that would allow potential CMSs recycling for environmental enhancement. The mass balance of the case study of the Mar Piccolo of Taranto (Southern Italy) showed potential recycling of marine sediments (the production of 974 kg filling materials per 1000 kg of dredged sediment) with a consequent missed disposal in landfills of 0.65 m3/1000 kg of sediment.