Size Fractionation Method Research Articles

Size-resolved distribution of trace elements in lysimeter soil solutions under contrasting long-term agricultural management to assess their bioavailability

The chemical species of trace elements (TEs) in agricultural soils is highly variable under diverse conditions, requiring tools with clear resolution and minimal disturbance for exploration. A novel surgical (316L) stainless steel (SS) lysimeter with a 5 μm pore size was developed to collect field soil solutions. The size-resolved distribution of TEs were characterized into total (nitric acid digestion), particulate (0.45–5 μm), dissolved (<0.45 μm), colloidal (1 kDa to 0.45 μm), and mainly ionic (<1 kDa) fractions in the lysimeter soil solutions. Total concentrations of TEs (dry weight basis) in acid digested Gray Luvisolic soils were analyzed. Most TEs in lysimeter soil solutions were present in particulate phases, relevant to their geochemical affinities and occurrences in soil minerals. Among dissolved fractions, As, Ba, Co, Li, Mn, Tl, and V existed as mainly ionic species in the soil solutions. Copper, Pb, Al, Th, and U showed variable associations with dissolved organic matter (DOM) and/or inorganic colloids among agricultural treatments. Inorganic NPKS or NKS fertilizer applications with lower pH (5.25–5.74) enhanced mobility and potential bioavailability of Ba, Co, Li, Mn, and Pb present in mainly ionic species, compared with other locations (pH 5.82–6.37). Manure application exhibited a dual effect, potentially increasing bioavailability for As, Tl, and V due to probably enhanced cation exchange capacity (CEC), while also facilitating specific adsorption of Cu and U on DOM, potentially reducing their bioavailability depending on DOM molecular weight. Colloidal and ionic Al and Th concentrations were higher in forest soils than agricultural soils, with extremely low potential bioavailability of Th attributed to strong precipitation with inorganic colloids and adsorption on DOM. The lysimeter sampling and size fractionation method provided a clear insight into agricultural effects on TE distributions and enhancing understanding of agricultural soil health in terms of TE bioavailability in situ.

The Relationship of Grain Size to Nickel Grade at Saprolite Zone of Lateritic Nickel Deposite in Moronopo Site, East Halmahera Regency, North Maluku

The research was conducted at the Dinding A and Dinding B, Moronopo Site PT Antam Tbk, East Halmahera, North Maluku which is a block that has been opened for the mining process. Generally the stratigraphy of laterite nickel deposits, from top (young) to bottom (old) consists of overburden, limonite, saprolite and bedrock. The saprolite zone is an economical ore layer for Ni content. This research aims to determine the relationship between grain size of ore and the mineralogy and economical Ni content. The research methods used include the grain size fractionation method with sizes of -5 cm, +5 cm, +10 cm, +15 cm, +20 cm and +25 cm, and XRF analysis to determine the Ni content. The result of this study shows the rocks in the saprolite zone containing minerals such as olivine, serpentine, garnierite and chrysoprase. The XRF analysis result shows the highest Ni content is found in the finest grain fraction (-5 cm) i.e. 2.4% and the lowest Ni content found in the coarsest grain fraction (+25 cm) i.e. 1.87 % but is still classified as economic.

Current Methods and Prospects for Analysis and Characterization of Nanomaterials in the Environment.

Analysis and characterization of naturally occurring and engineered nanomaterials in the environment are critical for understanding their environmental behaviors and defining real exposure scenarios for environmental risk assessment. However, this is challenging primarily due to the low concentration, structural heterogeneity, and dynamic transformation of nanomaterials in complex environmental matrices. In this critical review, we first summarize sample pretreatment methods developed for separation and preconcentration of nanomaterials from environmental samples, including natural waters, wastewater, soils, sediments, and biological media. Then, we review the state-of-the-art microscopic, spectroscopic, mass spectrometric, electrochemical, and size-fractionation methods for determination of mass and number abundance, as well as the morphological, compositional, and structural properties of nanomaterials, with discussion on their advantages and limitations. Despite recent advances in detecting and characterizing nanomaterials in the environment, challenges remain to improve the analytical sensitivity and resolution and to expand the method applications. It is important to develop methods for simultaneous determination of multifaceted nanomaterial properties for in situ analysis and characterization of nanomaterials under dynamic environmental conditions and for detection of nanoscale contaminants of emerging concern (e.g., nanoplastics and biological nanoparticles), which will greatly facilitate the standardization of nanomaterial analysis and characterization methods for environmental samples.

Process integration of sulphuric acid leach and particle size fractionation for cleaner copper concentrate production by enhancing the radionuclide mobility

• A process integration of selective H 2 SO 4 leach and particle size fractionation. • Mobility of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) in process. • The underlying mechanism of radionuclide mobility is unveiled. • A conceptual process is proposed for the cleaner Cu production from IOCGU ores. The growing demand of copper metal in the world continues to push the limit of utilization of complex copper resources, among which the iron oxide associated with copper–gold-uranium ore deposits (IOCG-U) contain economic copper and abundant gangues including uranium-bearing minerals that carry naturally occurring radionuclides and pose a challenge for public health and environment. To support the removal of radionuclides from copper flotation concentrate, the particle size fractionation method is integrated into the H 2 SO 4 leach process to illustrate the deportment of long-life radionuclides ( 238 U, 230 Th, 226 Ra, 210 Pb, 210 Po) and other non-copper elements during the process. H 2 SO 4 leach treatment largely dissolved non-copper elements (Fe, Ca, Mg, Al, K, F, U, Th, etc) from the gangue minerals and promoting the further copper phase transformation from the primary chalcopyrite and bornite towards covellite and copper sulphates. In the leach process, over 98% of 238 U and 230 Th were dissolved into H 2 SO 4 leach solution due to the decomposition of uranium-bearing minerals, while the released 226 Ra, 210 Pb and 210 Po from uranium-bearing minerals were largely remobilized, precipitated as insoluble sulphate salts, and accumulated in the small particle size fractions of the H 2 SO 4 leach residue. The underlying mechanism of this deportment is attributed to the mineralogical changes as an increased amount of covellite, digenite and copper sulphate are associated with the small particle size fractions, and serve as preferential hosts for 226 Ra, 210 Pb and 210 Po. Therefore, a conceptual flowsheet which facilitates further removal of 226 Ra, 210 Pb and 210 Po from the H 2 SO 4 leach residue is discussed based on particle size fractionation of the copper concentrate leach residue where radionuclides have been selectively leached or re-distributed.

Towards enriching and isolation of uncultivated archaea from marine sediments using a refined combination of conventional microbial cultivation methods

The archaea that can be readily cultivated in the laboratory are only a small fraction of the total diversity that exists in nature. Although molecular ecology methods, such as metagenomic sequencing, can provide valuable information independent of cell cultivation, it is only through cultivation-based experiments that they may be fully characterized, both for their physiological and ecological properties. Here, we report our efforts towards enriching and isolation of uncultivated archaea from marine sediments using a refined combination of conventional microbial cultivation methods. Initially, cells were retrieved from the sediment samples through a cell extraction procedure and the sediment-free mixed cells were then divided into different size-range fractions by successive filtration through 0.8 µm, 0.6 µm and 0.2 µm membranes. Archaeal 16S rRNA gene analyses indicated noticeable retention of different archaeal groups in different fractions. For each fraction, supplementation with a variety of defined substrates (e.g., methane, sulfate, and lignin) and stepwise dilutions led to highly active enrichment cultures of several archaeal groups with Bathyarchaeota most prominently enriched. Finally, using a roll-bottle technique, three co-cultures consisting of Bathyarchaeota (subgroup-8) and a bacterial species affiliated with either Pseudomonas or Glutamicibacter were obtained. Our results demonstrate that a combination of cell extraction, size fractionation, and roll-bottle isolation methods could be a useful protocol for the successful enrichment and isolation of numerous slow-growing archaeal groups from marine sediments.

Characterisation of road-dust sediment in urban systems: a review of a global challenge

PurposeThe proportion of people living in urbanised areas is predicted to rise to > 65% by 2050, and therefore, more humans than ever will be exposed to urban environmental pollution. Accumulation of organic and inorganic substances on street and road surfaces is a major global challenge requiring scientifically robust methods of establishing risk that inform management strategies. This aim of this contribution is to critically review the global literature on urban road–deposited sediment contamination with a specific focus on variability in sampling and analytical methods.Materials and methodsIn order to assess the concentration of contaminants in global road-deposited sediment (RDS), a comprehensive search of published RDS studies was completed. We review methodological approaches used in RDS studies to highlight the variability in datasets as a result of sampling technique, grain size fractionation, geochemical and mineralogical characterisation methods and establishing the influence of local geology on contaminant concentrations. We also consider emerging contaminants in RDS, and we provide a workflow diagram which promotes a standardised sampling and analysis regime that we believe can reduce data variability and promote collaboration when it comes to tackling the important issue of RDS contamination.Results and discussionAcross the literature, Asia (except China) and Africa are underrepresented in RDS studies despite these continents having the largest and fastest growing populations, respectively. The removal of tetraethyl lead from gasoline produced a noticeable decrease in lead concentrations in global RDS, and platinum group element (PGE) concentrations in RDS were consistent with catalytic converter usage. Research into the impact of electric vehicles on non-exhaust emissions suggests other contaminants such as zinc may become more prominent in the future. Most RDS studies consider grain size fractions larger than > 20 μm due to sampling constraints despite RDS < 20 μm being most relevant to human health. The use of chemical extraction methods to establish contaminant geochemistry is popular; however, most extraction procedures are not relevant or specific to minerals identified in RDS through microscopic and spectroscopic investigations.ConclusionsThis review highlights considerable variability in sampling and analytical approach which makes it difficult to identify broad global patterns in RDS contamination. To remove this variability from future RDS research, this review suggests a workflow plan which attempts to improve the comparability between RDS studies. Such comparability is crucial in identifying more discrete RDS trends and informing future emission policy.

Bioaccessibility of metals in soils surrounding two dismissed mining sites in Northern Italy

Mining activities are one of the main contributors to metals contamination of soils, most often due to the inappropriate management of the mining residues. In Italy, hundreds of small mining sites are scattered around the mountainous areas, near small villages with fragile environments. Here, wastes and residues may have polluted the surrounding soils and become a threat to living organisms. We investigated two dismissed sites in Northern Italy with extractive wastes in unmanaged areas close to villages using bioaccessibility and size fractionation methods, focussing on particles that can potentially be eroded and/or ingested (< 10 µm and < 200 µm). In the Campello Monti site, Co, Cu and Ni showed high values in soils near the landfills, with the highest concentrations in the < 10 µm particles around the landfills and along the valley bottom. Lead and Ni were the most bioaccessible metals. In the Plassa site, Cd and Zn were the most important contaminants, with an average content of 118 and 34,000 mg/kg. They originated from mining wastes scattered through the slope and had a particularly high bioaccessible fractions, close to the 100% for Zn and above 80% for Cd in the fine particles. The study of the fine, more reactive and mobile particles offered a close insight into the lability of contaminants, as in both sites, a dispersion of metal contaminants through very fine particles in surrounding and downhill areas was observed, resulting in an increased risk to all living organism and for the environment.

Protein Complex Identification and quantitative complexome by CN-PAGE

The majority of cellular processes are carried out by protein complexes. Various size fractionation methods have previously been combined with mass spectrometry to identify protein complexes. However, most of these approaches lack the quantitative information which is required to understand how changes of protein complex abundance and composition affect metabolic fluxes. In this paper we present a proof of concept approach to quantitatively study the complexome in the model plant Arabidopsis thaliana at the end of the day (ED) and the end of the night (EN). We show that size-fractionation of native protein complexes by Clear-Native-PAGE (CN-PAGE), coupled with mass spectrometry can be used to establish abundance profiles along the molecular weight gradient. Furthermore, by deconvoluting complex protein abundance profiles, we were able to drastically improve the clustering of protein profiles. To identify putative interaction partners, and ultimately protein complexes, our approach calculates the Euclidian distance between protein profile pairs. Acceptable threshold values are based on a cut-off that is optimized by a receiver-operator characteristic (ROC) curve analysis. Our approach shows low technical variation and can easily be adapted to study in the complexome in any biological system.

Size dependence of metabolism within marine picoplankton populations

AbstractCell size is broadly applied as a convenient parameterization of ecosystem models and is widely applicable to constrain the activities of organisms spanning large size ranges. However, the size structure of the majority of the marine picoplankton assemblage is narrow and beneath the lower size limit of the empirical allometric relationships established so far (typically &gt;1 μm). We applied a fine‐resolution (0.05 μm increments) size fractionation method to estimate the size dependence of metabolic activities of picoplankton populations in the 0.10–1.00 μm size interval within the surface North Pacific Subtropical Gyre microbial assemblage. Group‐specific carbon retained on each filter was quantified by flow cytometric conversion of light scatter to cellular carbon quotas. Median carbon quotas were 25.7, 22.6, and 5.9 fg C cell−1 for populations of the picocyanobacterium Prochlorococcus, high‐scatter heterotrophs, and low‐scatter heterotrophs, respectively. Carbon‐specific rates of primary production as a function of cell size, using the 14C method, and phosphate transport, using 33P radiotracers, resulted in negative power scalings (b) within populations of Prochlorococcus and heterotrophs of b = −1.3 and b = −1.1, respectively. These findings are in contrast to the positive empirical power scaling comprising the broader and larger prokaryote category (b = 0.7) and point to within‐population variability in cell physiology and metabolism for these important microbial groups.

Combined Size and Density Fractionation of Soils for Investigations of Organo-Mineral Interactions.

Combined size and density fractionation (CSDF) is a method used to physically separate soil into fractions differing in particle size and mineralogy. CSDF relies on sequential density separation and sedimentation steps to isolate (1) the free light fraction (uncomplexed organic matter), (2) the occluded light fraction (uncomplexed organic matter trapped in soil aggregates) and (3) a variable number of heavy fractions (soil minerals and their associated organic matter) differing in composition. Provided that the parameters of the CSDF (dispersion energy, density cut-offs, sedimentation time) are properly selected, the method yields heavy fractions of relatively homogeneous mineral composition. Each of these fractions is expected to have a different complexing ability towards organic matter, rendering this a useful method to isolate and study the nature of organo-mineral interactions. Combining density and particle size separation brings an improved resolution compared to simple size or density fractionation methods, allowing the separation of heavy components according to both mineralogy and size (related to surface area) criteria. As is the case for all physical fractionation methods, it may be considered as less disruptive or aggressive than chemically-based extraction methods. However, CSDF is a time-consuming method and furthermore, the quantity of material obtained in some fractions can be limiting for subsequent analysis. Following CSDF, the fractions may be analyzed for mineralogical composition, soil organic carbon concentration and organic matter chemistry. The method provides quantitative information about organic carbon distribution within a soil sample and brings light to the sorptive capacity of the different, naturally-occurring mineral phases, thus providing mechanistic information about the preferential nature of organo-mineral interactions in soils (i.e., which minerals, what type of organic matter).

Fractionation of graphene oxides by size-selective adhesion with spherical particles

Preparation of graphene has suffered from poor controllability of its lateral dimensions and the lack of sufficient fractionation technologies-the main barriers to its large-scale commercialization. This situation requires the development of an effective size fractionation strategy. Herein, the size-selective adsorption of graphene oxide (GO) onto positively charged spheres was developed as a novel size fractionation method. A critical lateral size of GO existed, above which physical adsorption was not stable, possibly because of the mechanical deformation involved. This scalable fractionation process easily produces well-dispersed GO sheets of relatively large lateral sizes, apart from the relatively small-sized GO sheets that are stably anchored onto the spherical particles. Moreover, this process is energy efficient and does not require any special equipment. This fractionation principle, size-selective adsorption, can be generalized to other various 2D nanomaterials.

Physical soil architectural traits are functionally linked to carbon decomposition and bacterial diversity.

Aggregates play a key role in protecting soil organic carbon (SOC) from microbial decomposition. The objectives of this study were to investigate the influence of pore geometry on the organic carbon decomposition rate and bacterial diversity in both macro- (250–2000 μm) and micro-aggregates (53–250 μm) using field samples. Four sites of contrasting land use on Alfisols (i.e. native pasture, crop/pasture rotation, woodland) were investigated. 3D Pore geometry of the micro-aggregates and macro-aggregates were examined by X-ray computed tomography (μCT). The occluded particulate organic carbon (oPOC) of aggregates was measured by size and density fractionation methods. Micro-aggregates had 54% less μCT observed porosity but 64% more oPOC compared with macro-aggregates. In addition, the pore connectivity in micro-aggregates was lower than macro-aggregates. Despite both lower μCT observed porosity and pore connectivity in micro-aggregates, the organic carbon decomposition rate constant (Ksoc) was similar in both aggregate size ranges. Structural equation modelling showed a strong positive relationship of the concentration of oPOC with bacterial diversity in aggregates. We use these findings to propose a conceptual model that illustrates the dynamic links between substrate, bacterial diversity, and pore geometry that suggests a structural explanation for differences in bacterial diversity across aggregate sizes.

Growth rates of common pelagic ciliates in a highly eutrophic lake measured with a modified dilution method

Abstract The growth rates of ciliates estimated under natural conditions with the widely used size fractionation method are much lower than those observed in cultures. However, recent studies performed with a modified dilution method demonstrated that the size fractionation method underestimates the ciliate growth, because it does not remove predators of the same size as the organisms studied. Thus, it is still unresolved whether ciliates are food-limited in different systems and whether their growth rates are indeed lower than those in cultures. This study was conducted in highly eutrophic Lake Gardno using a modified dilution method. Each time, two dilution experiments were performed (around noon and around midnight). Four small, common ciliates from the genera Rimostrombidium, Tintinnidium, Cyclidium, and Urotricha were studied. The first three ciliates demonstrated very high mean diel growth rates exceeding 0.1 h-1, which corresponded well to the highest values reported in the literature for the ciliate growth in cultures at similar temperatures. Tintinnidium sp. demonstrated a diel growth rhythm. Urotricha sp. was sensitive to the experimental procedure, and measurements of its growth were unsuccessful. Concentrations of food particles were analyzed to check whether organisms studied were food satiated.

Heterotrophic Bacteria Show Weak Competition for Nitrogen in Mediterranean Coastal Waters (Thau Lagoon) in Autumn.

The importance of heterotrophic bacteria relative to phytoplankton in the uptake of ammonium and nitrate was studied in Mediterranean coastal waters (Thau Lagoon) during autumn, when the Mediterranean Sea received the greatest allochthonous nutrient loads. Specific inhibitors and size-fractionation methods were used in combination with isotopic (15)N tracers. NO3 (-) and NH4 (+) uptake was dominated by phytoplankton (60 % on average) during the study period, which included a flood event. Despite lower biomass specific NH4 (+) and NO3 uptake rates, free-living heterotrophic bacteria contributed significantly (>30 %) to total microbial NH4 (+) and NO3 (-) uptake rates in low chlorophyll waters. Under these conditions, heterotrophic bacteria may be responsible for more than 50 % of primary production, using very little freshly produced phytoplankton exudates. In low chlorophyll coastal waters as reported during the present 3-month study, the heterotrophic bacteria seemed to depend to a greater extent on allochthonous N and C substrates than on autochthonous substrates derived from phytoplankton.

Growth rates of dinoflagellates along the Karachi coast assessed by the size fractionation method

Abstract The in situ growth rates of dinoflagellates along the Karachi coast off Pakistan was studied by the size fractionated method during winter (February 2006) and summer (May 2007). The growth rate per day ranged from -2.87 to 2.3 d-1 (20 species) in winter and from 1.20 to 1.95 d-1 (13 species) in summer. Growth rates (μmax d-1) of the dominant species were as follows: Prorocentrum gracile, Prorocentrum minimum, Prorocentrum arcuatum (1.0-1.10), Protoperidinium steinii (0.92), Gonyaulax spinifera (0.69), Dinophysis acuminata (2.3), Dinophysis caudata (0.92), Ceratium lineatum, Prorocentrum micans (1.95), Gyrodinium sp. (1.88), Ceratium furca (1.70), and Alexandrium ostenfeldii (1.34). The declining growth rates were observed for Pyrophacus stein (-1.10), Scrippsiella trochoidea (-1.61 to -0.82), Prorocentrum donghaiense (-1.94) and Karenia mikimotoi (-2.48). Our results suggest that a higher temperature induce an increase in dinoflagellate growth rates.

Speciation Analysis of Chromium in Environmental Waters in Niigata Prefecture by Applying Size Fractionation and Ion-Exchange Methods

Speciation Analysis of Chromium in Environmental Waters in Niigata Prefecture by Applying Size Fractionation and Ion-Exchange Methods

Variation in humic and fulvic acids during thermal sludge treatment assessed by size fractionation, elementary analysis, and spectroscopic methods

Thermal pretreatment can be applied to sludge anaerobic digestion or dewatering. To analyze the variation in humic substances during thermal sludge treatment, sludge humic and fulvic acids were extracted before and after 30-min thermal treatment at 180°C, and then their contents, molecular weight distributions, elementary compositions, and spectral characteristics were compared. The results showed that the total contents of humic and fulvic acids in the sludge almost remained constant during thermal treatment, but 35% of humic and fulvic acids were dissolved from the sludge solids. Moreover, both humic and fulvic acids were partly decomposed and 32% of humic acids were converted to fulvic acids. The median value of the molecular weights of humic acids decreased from 81 to 41 kDa and that of fulvic acids decreased from 15 to 2 kDa. Besides the reduction in molecular size, the chemical structures of humic and fulvic acids also exhibited a slight change, i.e. some oxygen functional groups disappeared and aromatic structures increased after thermal sludge treatment.

Mineral-associated organic carbon and black carbon in restored wetlands

Stable soil organic carbon (SSOC) has a vital influence on soil's capacity for resisting disturbance and sequestering carbon. However, studies of the SSOC in restored wetlands are incomplete. We studied mineral-associated organic carbon (MOC) and black carbon (BC), two representatives of SSOC, in a wetland restoration chronosequence in Caizi Lake, East China. MOC was analyzed by both a physical method, involving dividing soil into size-fractions POM (>53 μm) and MOM (0.45–53 μm) and detecting OC in MOM (MOCP), and a chemical method, acidifying soil with hydrofluoric acid (HF) and detecting OC loss (MOCC). BC was analyzed by methods using dichromate (BCCr) and chemothermal oxidation (BCCTO). MOCC, BCCr, and BCCTO were further determined in MOM for comparing results from different fractions and methods. We found an elevation of soil ecological function in wetlands restored from farmlands in Caizi Lake, which was supported by a general increase of MOC and BC with time after restoration at surface soil (0–6 cm). Comparison of methods showed that size fractionation method overestimated MOC by identifying all OC in MOM as MOC, since HF-soluble OC accounted for no more than 23.5% of the whole OC in MOM. As it may separate more components, e.g. charcoal, from BC continuum, the dichromate method was recommended as more meaningful in the study of BC recovery in restored wetlands with biomass-burning history. We presented the possible use of ratio (BCCr–BCCTO):BCCTO for BC source identification which produced a reasonable result similar to that of a commonly used method. The combination of physical and chemical fractionation methods revealed that the proportion of BC to TOC in POM was considerable, which indicated that POM was not invariably labile as was commonly understood. Finally, a detailed list of soil organic carbon components including MOC, BC and labile OC in each size fraction was represented by using sequential analysis and combination of fractionation methods.

A modified dilution method reveals higher protozoan growth rates than the size fractionation method

Protozoan growth rates are typically estimated with the size fractionation method in which the organisms studied are separated from the larger grazers. This method was compared with a specially modified dilution method which removed not only the grazing pressure of larger grazers but also that of predators of the same size as the organisms studied. Five comparisons were performed under natural conditions with the following marine protozoa: Balanion comatum (3 sets of data), Ebria tripartita, and Strombidium sp. The dilution method revealed significantly higher growth rates (Wilcoxon's signed-rank test, p=0.04), which underscores the importance of predation between organisms of the same size. It directly demonstrated that the size fractionation method may significantly underestimate protozoan growth rates.

Size Fractionation of Graphene Oxide Sheets by pH-Assisted Selective Sedimentation

Graphene oxide (GO) sheets prepared by Hummers' method have been separated into two portions with large (f1) or small (f2) lateral dimensions from their aqueous dispersion. This method is based on the selective precipitation of GO sheets with lateral dimensions mostly (>90%) larger than 40 μm(2) at a pH value of 4.0 because of their larger hydrophobic planes and fewer hydrophilic oxygenated groups. The hydrazine reduced Langmuir-Blodgett (LB) films of f1 showed much higher conductivities than those of f2. Furthermore, the thin film of f1 prepared by filtration exhibited a smaller d-space and much higher tensile strength and modulus than those of f2 films. The one-step size fractionation method reported here is simple, cheap, efficient, and environmentally friendly, which can be used for the size fractionation of GO sheets in large scale.