Measuring impacts of microplastic treatments via image recognition on immobilised particles below 100 μm

The treatment of samples for microplastic (MP) analysis requires purification steps that sufficiently reduce the non-MP content while preserving the targeted particles integrity. Besides their macromolecular structure this also encompasses their in situ numbers and sizes. However, any step of sample manipulation will come at a cost: particle loss, fragmentation, coagulation or degradation may lead to distorted results, predominantly in the smaller fraction of the MP size range. Therefore, the evaluation of MP resistivity against applied methods such as chemical digestions is a vital criterion for obtaining meaningful results on MP content of a sample. We developed a framework to test the applicability of MP purification methods and apply it to four protocols commonly used to prepare environmental samples for MP particle identification. The approach was designed for MP particles being too small to be handled manually (i.e. 10–70 μm). The evaluation consists of a two-tiered assay: a simple particle suspension approach is used to confirm a post-treatment qualitative recognisability of the target polymers by the analysis method of choice (here Raman and FTIR). In a following quantitative part, immobilised particles are used to evaluate the preservation of particle numbers and areas after the treatment on an individual particle level. A Python image analysis package was written that identifies, matches and measures particles on pairs of pre- and post-treatment images, and is available as open source software. Our results show that the chemical digestions using hydrogen peroxide, cooled Fenton’s and a combined alkaline / oxidative treatment using potassium hydroxide and sodium hypochlorite are suitable methods for preparing MP samples for a microspectroscopic analyses. Also acidic sodium polytungstate solution used for MP density separations and a pentane based protocol for lipid removal were found applicable for small sized MP. Certain degradative effects were found when acrylonitrile butadiene styrene is exposed to acidic treatments, as well as for MP from acrylate and epoxy based paint resins in strong oxidative regimes. Several paint resins tested here were spectroscopically not identifiable by polymer attributed bands even before treatment, indicating that these materials might slip through analyses of environmental samples and consequently being underreported. We conclude that evaluating chemical treatment procedures on MP < 100 μm is feasible, despite limitations of the current methodology which we discuss. Our results provide more certainty on the tested methods for MP studies specifically targeting small sizes and should be extended for more protocols used in MP laboratory practises.

Utilizing Rare-Earth-Elements Luminescence and Vibrational-Spectroscopies to Follow High Pressure Densification of Soda–Lime Glass

A new series of soda–lime glass naturally doped with Nd and doped with 0.2 wt% of Eu2O3 was densified in a multi-anvil press up to 21 GPa. The densities of the millimetric samples were precisely measured using a floatation method in a heavy liquid made with sodium polytungstate. The obtained densification curve is significantly different from the calibration previously reported, reaching a maximum densification saturation of 3.55 ± 0.14%. This difference could be due to better hydrostatic conditions realized in this new study. The densified samples were characterized using Raman and Brillouin spectroscopy, as well as the emission of both Eu3+ and Nd3+. The evolution of the spectra was evaluated using integration methods to reduce error bars. The relative precision of the calibration curves is discussed. The evolution of Nd3+ transition was found to be the most sensitive calibration. Linear dependence with the density was found for all observables, with exception for Brillouin spectroscopy showing a divergent behavior. The Brillouin shift shows an unreported minimum for a densification ~0.4%.

Iron and aluminum association with microbially processed organic matter via meso-density aggregate formation across soils: organo-metallic glue hypothesis

Global significance of iron (Fe) and aluminum (Al) for the storage of organic matter (OM) in soils and surface sediments is increasingly recognized. Yet specific metal phases involved or the mechanism behind metal–OM correlations frequently shown across soils remain unclear. We identified the allocation of major metal phases and OM to density fractions using 23 soil samples from five climate zones and five soil orders (Andisols, Spodosols, Inceptisols, Mollisols, Ultisols) from Asia and North America, including several subsurface horizons and both natural and managed soils. Each soil was separated into four to seven density fractions using sodium polytungstate with mechanical shaking, followed by the sequential extraction of each fraction with pyrophosphate (PP), acid oxalate (OX), and finally dithionite–citrate (DC) to estimate pedogenic metal phases of different solubility and crystallinity. The concentrations of Fe and Al (per fraction) extracted by each of the three reagents were generally higher in meso-density fractions (1.8–2.4 g cm−3) than in the lower- or higher-density fractions, showing a unique unimodal pattern along the particle density gradient for each soil. Across the studied soils, the maximum metal concentrations were always at the meso-density range within which PP-extractable metals peaked at 0.3–0.4 g cm−3 lower-density range relative to OX- and DC-extractable metals. Meso-density fractions, consisting largely of aggregated clusters based on SEM observation, accounted for on average 56 %–70 % of total extractable metals and OM present in these soils. The OM in meso-density fractions showed a 2–23 unit lower C : N ratio than the lowest-density fraction of the respective soil and thus appeared microbially processed relative to the original plant material. The amounts of PP- and OX-extractable metals correlated positively with co-dissolved C across the soils and, to some extent, across the density fractions within each soil. These results led to a hypothesis which involves two distinct levels of organo-metal interaction: (1) the formation of OM-rich, mixed metal phases with fixed OM : metal stoichiometry followed by (2) the development of meso-density microaggregates via “gluing” action of these organo-metallic phases by entraining other organic and mineral particles such as phyllosilicate clays. Given that OM is mainly located in meso-density fractions, a soil's capacity to protect OM may be controlled by the balance of three processes: (i) microbial processing of plant-derived OM, (ii) dissolution of metals, and (iii) the synthesis of organo-metallic phases and their association with clays to form meso-density microaggregates. The current hypothesis may help to fill the gap between well-studied molecular-scale interaction (e.g., OM adsorption on mineral surface, coprecipitation) and larger-scale processes such as aggregation, C accrual, and pedogenesis.

The yield values of densimetric fractions from typical chernozems of different land use types

One of the most justified and applied approaches to isolating pools of soil organic matter is fractionation in heavy liquids. The main problem with this approach is rather large losses in the separation of fractions at the stage of washing fractions from heavy liquids. The paper presents a densimetric fractionation protocol that can significantly reduce these losses. It is suggested to use 0.001 M HCl for washing. This approach, in comparison with distilled water, allows reducing losses of weight from 15 to 5% and of carbon from 7.5 to 2.5%. The paper provides a detailed protocol, used by the Laboratory of Soil Biochemistry of V.V. Dokuchaev Soil Science Institute, to isolate four densimetric fractions using sodium polytungstate solutions: free and occluded SOM with a density of <1.6 g/cm3, occluded SOM – of 1.6–2.0 g/cm3, and a mineral residue with a density >2.0 g/cm3. In the work we used samples of typical chernozems of different land use types. It was shown that the processes of soil restoration and degradation significantly affect the content of light occluded soil organic matter.

Iron and aluminum association with microbially processed organic matter via meso-density aggregate formation across soils: organo-metallic glue hypothesis

Global significance of iron (Fe) and aluminum (Al) for the storage of organic matter (OM) in soils and surface sediments is increasingly recognized. Yet specific metal phases involved or the mechanism behind metal-OM correlations frequently shown across soils remain unclear. We identified density fraction locations of major metal phases and OM using 23 soil samples from 5 climate zones and 5 soil orders (Andisols, Spodosols, Inceptisols, Mollisols, Ultisols), including several subsurface horizons and both natural and managed soils. Each soil was separated to 4 to 7 density fractions using sodium polytungstate with mechanical shaking, followed by the sequential extraction of each fraction with pyrophosphate (PP), acid oxalate (OX), and finally with dithionite-citrate (DC) to estimate pedogenic metal phases of different solubility and crystallinity. The extractable Fe and Al concentrations (per fraction) generally showed unique unimodal distribution along particle density gradient for each soil and each extractable metal phase. Across the studied soils, the maximum metal concentrations were always at meso-density range (1.8–2.4 g cm−3) within which PP-extractable metals peaked at 0.3–0.4 g cm−3 lower density range relative to OX- and DC-extractable metals. Meso-density fractions, consisted largely of microaggregates based on SEM observation, accounted for on average 56–70 % of total extractable metals and OM present in these soils. The OM in meso-density fractions appeared microbially processed from the original plant material. The amounts of PP- and OX-extractable metals correlated positively with co-dissolved C among the soils and, to some extent, across the density fractions within each soil. These results led to a hypothesis which involves two distinct levels of organo-metal interaction – the formation of OM-rich, mixed metal phases having relatively fixed OM : metal stoichiometry and subsequent development of meso-density microaggregates via gluing properties of these organo-metallic phases by incorporating other organic and mineral particles such as phyllosilicate clays. Given that stable OM is mainly located in meso-density fractions, soil's capacity to protect OM may be controlled by the balance of following three processes: (i) microbial processing of plant-derived OM, (ii) dissolution of metals, and (iii) the synthesis of organo-metallic phases and their association with clays to form meso-density microaggregates. The current hypothesis may help to fill the gap between well-studied molecular scales interaction (e.g., OM adsorption on mineral surface, coprecipitation) and larger-scale processes such as aggregation, C accrual, and pedogenesis.

Aragonite Fraction Dating of Vermetids in the Context of Paleo Sea-Level Curves Reconstruction

ABSTRACTIdentifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating.

Beneficiation of Sugarcane Bagasse Boiler Ash via Production of Syntactic Foams and Thermal Refractory Materials

Aqueous solutions of sodium polytungstate were used to fractionate samples of sugarcane bagasse ash by heavy media separation. Practically no cenospheres were recovered from the ash samples. The method was successful in separating fibrous carbonaceous particles with a uniform surface from particles containing more silica and having a less uniform surface. A geopolymer refractory brick having satisfactory durability was produced from sugarcane bagasse ash with metakaolin and ball clay fillers and a sodium metasilicate/hydroxide activator liquor. Drying and firing shrinkage, bulk density and ultimate compressive strength tests were performed to determine the most feasible combination of ingredients. Geopolymer samples produced using aluminium powder instead of ball clay were found to be very brittle and unsuitable for refractory service.

Hasil Analisis Mikrofosil Tumbuhan (phytolith) Situs Wineki dan Padang Hadoa, di Kawasan Lembah Besoa, Sulawesi Tengah.

Phytoliths are plant microfossil made of silica that varies in shape and size. Variations of form happen when silica in soil is absorbed by plants then transported and deposited in various parts of plant cells. When the plant dies, the plant's organic matter decomposes and leaves the inorganic material of silica, which we know by the name of phytoliths. Silica can survive in various environmental conditions, That’s make phytoliths are important data for scientific research including archeology. Phytoliths analysis on soil samples from prehistoric Besoa Valley’s site aimed to reveal past environmental conditions and also find out the possibility of an economical plant utilization. Extraction performed on 18 soil samples from Wineki (box K1) and the Padang Hadoa sites (box K2 and K3). Techniques were performed using Sodium Polytungstate heavy flotation. Phytoliths identification results reveal palmae plants dominate the entire site, other phytolith derived from sample are Poaeceae, Cyperaceae and also two types of economic plants Oryza and Musaceae. Difference vegetation on past (dominated by palm) and current conditions (dominated by grasses)can indicate their changing environmental conditions either due to natural or due to human intervention. The existence of Oryza and Musaceae in Padang Hadoa sites can be an indication of the use by Padang Hadoa’s prehistoric occupant.Keyword : phytolith, Besoa Valley, Oryza, Musaceae Phytoliths merupakan mikrofosil tumbuhan berbahan silica yang bervariasi secara bentuk dan ukuran. Variasi bentuk phytolith terjadi ketika silica dalam tanah terserap oleh tumbuhan kemudian terangkut dan terdeposisi pada bermacam bagian sel tumbuhan. Ketika tumbuhan mati, material organic tumbuhan membusuk dan meninggalkan material anorganik berupa silica yang kemudian kita kenal dengan nama phytoliths. Sifat silica yang dapat terawetkan diberbagai kondisi lingkungan menjadikan phytoliths data penting bagi penelitian ilmiah termasuk bagi arkeologi. Analisis phytoliths pada sampel tanah dari kawasan prasejarah Lembah Besoa ini bertujuan untuk mengungkapkan kondisi lingkungan masa lalu dan juga mengetahui kemungkinan adanya pemanfaatan tumbuhan. Ekstraksi dilakukan pada 18 sampel tanah dari Wineki ( kotak K1 ) dan situs Padang Hadoa ( kotak K2 dan K3 ). Teknik yang dilakukan yakni dengan pengambangan menggunakan mineral berat Sodium Polytungstate. Hasil identifikasi mengungkapkan tumbuhan jenis palem mendominasi seluruh situs dibandingkan dengan jenis tumbuhan lain. Jenis tumbuhan lain yang dapat diidentifikasi dari sampel yaitu jenis Poaeceae, Cyperaceae dan juga dua jenis tumbuhan ekonomis Oryza dan Musaceae. Perbedaan vegetasi di masa lalu (yang didominasi oleh palem) dan kondisi saat ini (didominasi oleh rumput ) dapat menunjukkan adanya perubahan kondisi lingkungan baik karena alam atau karena campur tangan manusia. Keberadaan Oryza dan Musaceae di situs Padang Hadoa dapat menjadi indikasi adanya pemanfaatan jenis tumbuhan tersebut oleh manusia pendukung situs Padang Hadoa ini.Kata kunci: phytolith, Lembah Besoa, Oryza, Musaceae