Supramolecular Polymer Frameworks with Controlled and Uniform Pore Apertures.

Porous frameworks with controlled pore structure and tunable aperture are greatly demanded. However, precise synthesis of this kind of materials is a formidable challenge. Herein, we report the fabrication of two-dimensional (2D) supramolecular polymer frameworks using a precisely synthesized rod-like helical polyisocyanide as link. Four three-arm star-shaped polyisocyanides with the degree of the polymerization of 10, 20, 30 and 40, and having 2-ureido-4[1H]-pyrimidinone (UPy) terminals were synthesized. 2D-Crystalline polymer frameworks with apertures of 5.3, 10.1, 13.9, and 19.1 nm were respectively obtained through intermolecular hydrogen bonding interaction between the terminal Upy units. The pore aperture is dependent on the length of polyisocyanide backbone. Thus, well-defined supramolecular polymer frameworks with controlled and uniform hexagonal pores were obtained, as proved by small-angle X-ray scattering (synchrotron radiation facility), atomic force microscopy, and Brunauer-Emmett-Teller analyses. The frameworks with uniform large pore aperture were used to purify nanomaterials and immobilize biomacromolecules. For instance, the membranes of the polymer frameworks could size-fractionation of silver nanoparticles into uniform nanoparticles with very low dispersity. The frameworks with large aperture facilitated the inclusion of myoglobin and enhanced the stability and catalytic activity.

Monodispersed Renewable Particles by Cascade and Density Gradient Size Fractionation to Advance Lignin Nanotechnologies.

Control over particle size and shape heterogeneity is highly relevant to the design of photonic coatings and supracolloidal assemblies. Most developments in the area have relied on mineral and petroleum-derived polymers that achieve well-defined chemical and dimensional characteristics. Unfortunately, it is challenging to attain such control when considering renewable nanoparticles. Herein, a pathway toward selectable biobased particle size and physicochemical profiles is proposed. Specifically, lignin is fractionated, a widely available heterogeneous polymer that can be dissolved in aqueous solution, to obtain a variety of monodispersed particle fractions. A two-stage cascade and density gradient centrifugation that relieves the need for solvent pre-extraction or other pretreatments but achieves particle bins of uniform size (~60 to 860 nm and polydispersity, PDI<0.06, dynamic light scattering) along with characteristic surface chemical features is introduced. It is found that the properties and associated colloidal behavior of the particles are suitably classified in distinctive size populations, namely, i) nanoscale (50-100 nm), ii) photonic (100-300 nm) and iii) near-micron (300-1000 nm). The strong correlation that exists between size and physicochemical characteristics (molar mass, surface charge, bonding and functional groups, among others) is introduced as a powerful pathway to identify nanotechnological uses that benefit from the functionality and cost-effectiveness of biogenic particles.

SOC bioavailability significantly correlated with the microbial activity mediated by size fractionation and soil morphology in agricultural ecosystems.

Despite the fact that physical and chemical processes have been widely proposed to explicate the stabilization mechanisms of soil organic carbon (SOC), thebioavailability of SOC linked to soil physical structure, microbial community structure, and functional genes remains poorly understood. This study aims to investigate the SOC division based on bioavailability differences formed by physical isolation, and to clarify the relationships of SOC bioavailability with soil elements, pore characteristics, and microbial activity. Results revealed that soil element abundances such as SOC, TN, and DOC ranked in the same order as the soil porosity as clay > silt ≥ coarse sand > fine sand in both top and sub soil. In contrast to silt and clay, which had reduced SOC bioavailability, fine sand and coarse sand had dramatically enhanced SOC bioavailability compared to the bulk soil. The bacterial and fungal community structure was significantly influenced by particle size, porosity, and soil elements. Copiotrophic bacteria and functional genes were more prevalent in fine sand than clay, which also contained more oligotrophic bacteria. The SOC bioavailability was positively correlated with abundances of functional genes, C degradation genes, and copiotrophic bacteria, but negatively correlated with abundances of soil elements, porosity, oligotrophic bacteria, and microbial biomass (p < 0.05). This indicated that the soil physical structure divided SOC into pools with varying levels of bioavailability, with sand fractions having more bioavailable organic carbon than finer fractions. Copiotrophic Proteobacteria and oligotrophic Acidobacteria, Firmicutes, and Gemmatimonadetes made up the majority of the bacteria linked to SOC mineralization. Additionally, the fungi Mortierellomycota and Mucoromycota, which are mostly involved in SOC mineralization, may have the potential for oligotrophic metabolism. Our results indicated that particle-size fractionation could influence the SOC bioavailability by restricting SOC accessibility and microbial activity, thus having a significant impact on sustaining soil organic carbon reserves in temperate agricultural ecosystems, and provided a new research direction for organic carbon stability.

Polycyclic aromatic hydrocarbons in 55-120 µm phytoplankton.

A baseline study was undertaken on polycyclic aromatic hydrocarbons (PAHs) in phytoplankton. Plankton samples from six stations (duplicates) in Kaohsiung Harbor (KH), Taiwan along with a phytoplankton control sample afar from the harbor, were collected. We applied size-fractionation to isolate phytoplankton (55-120 µm), followed by sedimentation and centrifugation to remove abiogenic particulates. The phytoplankton was freeze-dried, extracted with acetone: n-hexane (1:1, v/v), and analyzed using GC-MS. ΣPAHs in phytoplankton ranged between 5204 and 28,903 ng/g dry weight (mean: 12,150 ng/g). The ΣPAHs in KH were >7 times than the control site (C1: 3972 ng/g). Cluster analysis showed spatial gradients (northern < southern KH). Accumulated PAHs in phytoplankton were from petrogenic (fishing ports and ships) and pyrogenic (river outflows), dominated by lower-ring PAHs, likely due to their higher bioavailability in the dissolved phase. We present a practical phytoplankton isolation technique for more accurate phytoplankton PAH concentrations with insights into their distribution and sources.

Size-fractionated distribution of glycerol dialkyl glycerol tetraether core lipids in surface sediments of a large-river delta-front estuary.

Glycerol dialkyl glycerol tetraether core lipids (GDGTs) are microbial biomarkers ubiquitously distributed in terrestrial and marine environments. Dispersal and fate of GDGTs in an estuary largely depends on sediment grain size, however, their size distribution patterns remain poorly understood. Here, surface sediments collected from the Changjiang Estuary were separated into <20, 20-32, 32-63, 63-125 and >125 µm fractions, and analyzed for GDGTs as well as total organic carbon (TOC), stable isotopic composition (δ13C) of TOC and lignin phenols, to investigate the size and spatial distributions of GDGTs and the particle size effects on GDGTs proxies in this large river delta-front estuary. The concentrations of isoprenoidal GDGTs (isoGDGTs) were higher in the finest fractions and in off-estuary sites. On the contrary, branched GDGTs (brGDGTs) were high not only in the finest fractions but in coarser fractions (>32 µm fractions), and thus at both near- and off-estuary sites. The branched and isoprenoid tetraether (BIT) index increased with increasing grain size, and decreased sharply from the estuary (~0.52) to the shelf (~0.16). BrGDGTs were positively correlated with crenarcheaol in both high and low BIT regions. The brGDGTIIIa/IIa ratios in all size fractions were <0.59, further indicating that the brGDGTs were mainly derived from terrestrial input with minimum in-situ production. Fractional TOC source assignments derived from the BIT index was significantly positively correlated with the fractions of terrestrial OC from a mixing model based on δ13C-TOC and lignin contents, indicating that BIT may track a broader pool of terrestrial OC than just soil OC. This work provides novel, yet preliminary insights into the size fractionated distribution characteristics of GDGTs and the applicability of BIT as a proxy for OC sources in estuarine sediments. More work is needed to further clarify the particle size effects on other GDGTs proxies in estuarine systems.

Novel insights into the mechanisms for Sb mobilization in groundwater in a mining area: A colloid field study.

Colloids may play an important role in the geochemical cycle of antimony (Sb). However, the controlling behaviors of colloids on Sb fate in contaminated groundwater are not available. To investigate the effects of colloids on Sb mobility, groundwater samples from Xikuangshan Sb Mine's two main aquifers (the D3s2 aquifer and the D3x4 aquifer) were successively (ultra)filtered through progressively decreasing pore sizes (0.45 µm, 100 kDa, 50 kDa and 5 kDa). The results showed that 0.1-84.1% of Sb was adsorbed or carried by colloids, which corresponded to Sb concentration ranging between 0 and 2973 µg/L in the colloids (0.45 µm - 5 kDa). In both aquifers, Sb was closely associated with organic colloids (r = 0.72 p < 0.05 for the D3x4 aquifer, r = 0.94 p < 0.01 for the D3s2 aquifer). Parallel factor analysis of the three-dimensional fluorescence spectra determined that the protein-like substances in the D3x4 aquifer and the humus-like substances in the D3s2 aquifer controlled Sb behavior. X-ray absorption spectroscopy confirmed Sb complexing with organic substances. Competitive adsorption of As and Sb suppressed the complexation of colloids with Sb, particularly in the D3x4 aquifer (r = -0.71, p < 0.05). Sb mobility was also influenced by the redox of the groundwater system. As the oxidation-reduction potential and dissolved oxygen increased, Sb in the colloidal fractions decreased. These findings provide new insights into the mechanisms involved in Sb fate affected by colloids, establishing the theoretical basis for developing effective Sb and even metalloid pollution remediation strategies.

Response to: "The robust concept of mineral-associated organic matter saturation: A letter to Begill et al. (2023)".

In this response to a letter to the editor, we provide evidence that the findings regarding a non-detectable limit of mineral-associated organic carbon as published in Begill et al. (2023) are robust. This is mainly done by showing that no methodological bias was present and that the main correlation was not driven by a few exceptional soils.

Impact of particle flux on the vertical distribution and diversity of size-fractionated prokaryotic communities in two East Antarctic polynyas.

Antarctic polynyas are highly productive open water areas surrounded by ice where extensive phytoplankton blooms occur, but little is known about how these surface blooms influence carbon fluxes and prokaryotic communities from deeper waters. By sequencing the 16S rRNA gene, we explored the vertical connectivity of the prokaryotic assemblages associated with particles of three different sizes in two polynyas with different surface productivity, and we linked it to the magnitude of the particle export fluxes measured using thorium-234 (234Th) as particle tracer. Between the sunlit and the mesopelagic layers (700 m depth), we observed compositional changes in the prokaryotic communities associated with the three size-fractions, which were mostly dominated by Flavobacteriia, Alphaproteobacteria, and Gammaproteobacteria. Interestingly, the vertical differences between bacterial communities attached to the largest particles decreased with increasing 234Th export fluxes, indicating a more intense downward transport of surface prokaryotes in the most productive polynya. This was accompanied by a higher proportion of surface prokaryotic taxa detected in deep particle-attached microbial communities in the station with the highest 234Th export flux. Our results support recent studies evidencing links between surface productivity and deep prokaryotic communities and provide the first evidence of sinking particles acting as vectors of microbial diversity to depth in Antarctic polynyas, highlighting the direct influence of particle export in shaping the prokaryotic communities of mesopelagic waters.

Comparisons in molecular weight distributions and size-dependent optical properties among model and reference natural dissolved organic matter.

Humic acid (HA) and reference natural organic matter (NOM) have been widely used in environmental assessment, biogeochemistry, and ecotoxicity studies. Nevertheless, similarities and differences among the commonly used model/reference NOMs and bulk dissolved organic matter (DOM) have rarely been systematically evaluated. In this study, HA, SNOM (Suwannee River NOM) and MNOM (Mississippi River NOM), both from International Humic Substances Society, and freshly collected unfractionated NOM (FNOM) were concurrently characterized to evaluate their heterogeneous nature and size-dependent chemical properties. We found that molecular weight distributions, PARAFAC-derived fluorescent components, and size-dependent optical properties are NOM-specific and highly variable with pH. The < 1 kDa DOM abundance followed the order of HA < SNOM < MNOM < FNOM. In addition, FNOM was more hydrophilic and contained more protein-like and autochthonous components with a higher UV-absorbance ratio index (URI) and biological fluorescence index, whereas HA and SNOM contained more allochthonous, humic-like components with a higher aromaticity and lower URI. Significant differences in molecular composition and size spectra between FNOM and model/reference NOMs suggest that environmental role of NOMs should be evaluated at the levels of molecular weight and functionalities under the same experimental conditions and that HA and SNOM may not represent bulk NOM in the environment. This study provides new information about similarities and differences in DOM size-spectra and chemical properties between reference NOMs and in-situ NOM and highlights the need to better understand the heterogenous roles of NOMs in regulating the toxicity/bioavailability and environmental fate of pollutants in aquatic environments.

Characterization of the Plasmatic and Erythroid Multielemental Biodistribution in Childhood Obesity Using a High-Throughput Method for Size Fractionation of Metal Species.

In this chapter, we describe a metallomics method based on protein precipitation under non-denaturing conditions and further analysis by inductively coupled plasma mass spectrometry for high-throughput metal speciation in plasma and erythrocyte samples. This methodology enables to study the total multielemental profile of these biological matrices, as well as to quantify the metal fractions conforming the metallometabolome and the metalloproteome. Furthermore, the analytical coverage comprises several essential and toxic metal elements, namely aluminum, arsenic, cadmium, cobalt, chromium, copper, iron, lithium, manganese, molybdenum, nickel, lead, selenium, vanadium, and zinc. Altogether, the metallomics method here proposed represents an excellent approach to comprehensively characterize the metal biodistribution in human peripheral blood, which would enable to decipher the role of metal homeostasis in health and disease, and particularly in childhood obesity.

Revealing the reasons for the pasting property changes of rice during aging from the perspective of starch granule disaggregation.

BACKGROUND: The pasting properties of rice change markedly after aging, although the mechanism for this still remains unknown. Aged and fresh rice grains were ground and the flours were fractionated by particle size, and then the pasting properties, particle size distribution and microscopic morphology of the heated flour fractions were evaluated. RESULTS: Compared to the corresponding fresh flour fractions with the same particle size, a lower peak viscosity for those aged flour fractions from 80 µm to 450 µm and a higher peak viscosity for those aged flour fractions from 20 µm to 60 µm were observed. The amounts of smaller particles disaggregated from the aged flour fractions were significantly less and the separated entities were always larger than the corresponding fresh rice fractions. CONCLUSION: Disaggregation difficulty of starch granules was the reason for the changes in the pasting properties of rice after aging. This finding is helpful for understanding rice aging mechanisms and regulating eating quality of rice flour as an ingredient. © 2022 Society of Chemical Industry.

Impact of sample clarification by size exclusion on virus detection and diversity in wastewater-based epidemiology.

The use of wastewater-based epidemiology (WBE) for early detection of virus circulation and response during the SARS-CoV-2 pandemic increased interest in and use of virus concentration protocols that are quick, scalable, and efficient. One such protocol involves sample clarification by size fractionation using either low-speed centrifugation to produce a clarified supernatant or membrane filtration to produce an initial filtrate depleted of solids, eukaryotes and bacterial present in wastewater (WW), followed by concentration of virus particles by ultrafiltration of the above. While this approach has been successful in identifying viruses from WW, it assumes that majority of the viruses of interest should be present in the fraction obtained by ultrafiltration of the initial filtrate, with negligible loss of viral particles and viral diversity. We used WW samples collected in a population of ~700,000 in southwest USA between October 2019 and March 2021, targeting three non-enveloped viruses (enteroviruses [EV], canine picornaviruses [CanPV], and human adenovirus 41 [Ad41]), to evaluate whether size fractionation of WW prior to ultrafiltration leads to appreciable differences in the virus presence and diversity determined. We showed that virus presence or absence in WW samples in both portions (filter trapped solids [FTS] and filtrate) are not consistent with each other. We also found that in cases where virus was detected in both fractions, virus diversity (or types) captured either in FTS or filtrate were not consistent with each other. Hence, preferring one fraction of WW over the other can undermine the capacity of WBE to function as an early warning system and negatively impact the accurate representation of virus presence and diversity in a population.

Wide-Range Size Fractionation of Graphene Oxide by Flow Field-Flow Fractionation.

Many interesting properties of 2D materials and their assembled structures are strongly dependent on the lateral size and size distribution of 2D materials. Accordingly, effective size separation of polydisperse 2D sheets is critical for desirable applications. Here, we introduce flow field-flow fractionation (FlFFF) for a wide-range size fractionation of graphene oxide (GO) up to 100 µm. Two different separation mechanisms are identified for FlFFF, including normal mode and steric/hyperlayer mode, to size fractionate wide size-distributed GOs while employing a crossflow field for either diffusion or size-controlled migration of GO. Obviously, the 2D GO sheet reveals size separation behavior distinctive from typical spherical particles arising from its innate planar geometry. We also investigate 2D sheet size-dependent mechanical and electrical properties of three different graphene fibers produced from size-fractionated GOs. This FlFFF-based size selection methodology can be used as a generic approach for effective wide-range size separation for 2D materials, including rGO, TMDs, and MXene.

Diversity of Candidatus Patescibacteria in Activated Sludge Revealed by a Size-|Fractionation Approach.

Uncultivated members of Candidatus Patescibacteria are commonly found in activated sludge treating sewage and are widely distributed in wastewater treatment plants in different regions and countries. However, the phylogenetic diversity of Ca. Patescibacteria is difficult to examine because of their low relative abundance in the environment. Since Ca. Patescibacteria members have small cell sizes, we herein collected small microorganisms from activated sludge using a filtration-based size-fractionation approach (i.e., 0.45-0.22| |µm and 0.22-0.1| |µm fractions). Fractionated samples were characterized using 16S rRNA gene amplicon and shotgun metagenomic sequence ana-lyses. The amplicon ana-lysis revealed that the relative abundance of Ca. Patescibacteria increased to 73.5% and 52.5% in the 0.45-0.22| |µm and 0.22-0.1| |µm fraction samples, respectively, from 5.8% in the unfractionated sample. The members recovered from the two size-fractionated samples included Ca. Saccharimonadia, Ca. Gracilibacteria, Ca. Paceibacteria, Ca. Microgenomatia, class-level uncultured lineage ABY1, Ca. Berkelbacteria, WS6 (Ca. Dojkabacteria), and WWE3, with Ca. Saccharimonadia being predominant in both fraction samples. The number of operational taxonomic units belonging to Ca. Patescibacteria was approximately 6-fold higher in the size-fractionated samples than in the unfractionated sample. The shotgun metagenomic ana-lysis of the 0.45-0.22| |µm fractioned sample enabled the reconstruction of 24 high-quality patescibacterial bins. The bins obtained were classified into diverse clades at the family and genus levels, some of which were rarely detected in previous activated sludge studies. Collectively, the present results suggest that the overall diversity of Ca. Patescibacteria inhabiting activated sludge is higher than previously expected.

Analyses of colloidal, truly dissolved, and DGT-labile metal species and phosphorus in mining area surrounded by tailing dams using self-organising maps.

The knowledge of size-distribution and lability of metals and nutrients in freshwater systems is important for estimation of the ecological effects of mining. However, it is still limited in several mining areas such as the Quadrilátero Ferrífero (Brazil) which was severely polluted by the collapse of the Fundão tailings dam in November 2015. In this study, results of an investigation from 2014 using a neural network named self-organising map (SO-Map) into the conditions of selected trace metals that are of particular importance to mining areas (Cr, Cu, Co, Mn, Ni, Pb, Zn) are presented. Additionally, P was considered by its high importance as a nutrient and sites later affected by the dam burst were also included by chance. Water samples were collected at six sites in dry and rainy seasons and filtered and ultrafiltered for determination of total dissolved (<0.45 µm) and truly dissolved (<1 kDa) fractions. Diffusive gradients in thin films (DGT) devices were deployed in situ for determination of the DGT-labile fraction. All data were analysed using SO-Map and Spearman's rank correlation. Phosphorus in the Carmo River occurred mainly in the truly dissolved and DGT-labile fractions. The higher amounts of this element in the river water (up to 263 µg L-1 of total P) might be related to untreated sewage discharge. Moreover, the concentrations of other trace metals (Mn, Cu, Co, Ni, Zn) were high, even under the "natural" conditions (before the dam failure) due to natural and anthropogenic factors such as local lithology and mining.

Impacts of size-fractionation on toxicity of marine microplastics: Enhanced integrated biomarker assessment in the tropical mussels, Perna viridis.

Accumulation of microplastics (MP) in oceanic waters is eroding the health of marine biota. We investigated how size-fractionated MP influence the toxicity risks towards a tropical keystone species, Perna viridis. Tissue-specific bioaccumulation and in vivo toxicity of polystyrene (PS) particles (0.5, 5, and 50 µm) were measured upon continuous exposure for 7 days, followed by 7 days depuration. P. viridis were exposed to equivalent mass (0.6 mg/L), corresponding to 4.0-4.6 particles/mL, 4.6-7.1 × 103 particles/mL, and 1.1-4.8 × 106 particles/mL for 50 µm, 5 µm and 0.5 µm PS particles, respectively. Onset toxicity were quantified through the enhanced integrated multi-biomarker response (EIBR) model, measured by weighting of biological organisation levels of eight biomarkers: (i) molecular (i.e., DNA damage (comet), 7-ethoxy resorufin O-deethylase (EROD), Catalase (CAT), Superoxide dismutase (SOD), Ferric Reducing Antioxidant Power (FRAP)); (ii) cellular (i.e., Neutral red retention (NRR), phagocytosis); and (iii) physiological (i.e., filtration rate). Data showed slightly elevated lysosomal instability (NRR) and antioxidant defences (FRAP, SOD, CAT, EROD) in specimens exposed to nano-PS (0.5 µm) compared to micro-PS (5 and 50 µm). Immunotoxicity (phagocytosis) and genotoxicity (comet) for haemocyte cells were significantly higher in specimens exposed to nano-PS (p < 0.05). EIBR index corroborated increasing toxicity modulated by MP sizes in descending order: 0.5 µm > 5 µm > 50 µm, with nano-PS exerted significantly higher biological effects (EIBR = 19.77 ± 5.89) than the unexposed group (EIBR = 10.97 ± 2.02; p < 0.05). Symptomatic organismal depression was manifested by the depleting filtering proficiency and weakened defence against invasive Zymosan bioparticles in the phagocytosis assay. Although impaired mussels duly recovered during depuration, individuals affected by nano-PS showed immunocompetence deficiency and gill responses that were not readily reversible, which could potentially increase their vulnerability towards further environmental stressors.

Antimony and arsenic particle size distribution in a mining contaminated freshwater river: Implications for sediment quality assessment and quantifying dispersion.

Assessments of antimony (Sb) and arsenic (As) contamination in sediments are reported on a wide range of different particle size fractions, including <63 µm, < 180 µm and <2 mm. Guidelines vary between jurisdictions which limits comparative assessment between contamination events and complicates ecotoxicity assessment, and almost no information exists on Sb size distribution in contaminated sediments. This study quantified and compared the size distribution of Sb and As in 11 sediments (and 2 floodplain soils) collected along 320 km of waterway contaminated by historic mining activity. Sediment particle size distribution was the primary determinant of total metalloid load in size fractions across the varying substrates of the waterway. Minerals and sorption complexes influenced metalloid particle distribution but relative importance depended on location. Arsenic concentrations were greatest in the fine <63 µm fraction across all the different river environments (7.3-189 mg kg-1, or 1-26% of total sample As), attributed to fine-grained primary arsenopyrite and/or sorption of As(V) to fine solid-phases. The Sb particle size concentrations were greatest in mid-size fractions (205-903 mg kg-1) in the upper catchment and up to 100 km downstream to the mid-catchment as a result of remnant Sb minerals. Antimony concentrations in the lower catchment were greatest in the <63 µm fraction (8.8-12.1 mg kg-1), reflecting the increasing importance of sorption for Sb particle associations. This work demonstrates the importance of particle size analysed for assessment of sediment quality, and provides support for analysis of at least the <250 µm fraction for Sb and As when comparing pollutant distribution in events impacted by primary contamination. Analysis of the <63 µm fraction, however, provides good representation in well-dispersed contaminated sediments.

Comparative trace metal assessment in phytoplankton using size and density fractionation.

Trace metal assessment in marine phytoplankton is challenging due to complex assemblages and variable amounts of abiogenic suspended particulates. Using aliquots, this study were able to compare trace metal concentrations in plankton samples subjected to size and density fractionation. Elements including Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Hg, and Pb were analyzed by inductively coupled plasma mass spectrometer (ICP-MS). Trace metals were found to be significantly higher in size fractionated than density fractionated plankton for both small (1.2-50 µm) and large (50-120 µm) fractions. Metals from abiogenic sources (61-88%) also significantly contributed to trace metals detected in 1.2-120 µm suspended particulates collected from Kaohsiung Harbor. Results suggest that size fractionation can potentially overestimate trace metals in phytoplankton. It is therefore recommended combining the two methods by first isolating different size fractions followed by density fractionation to separate phytoplankton from zooplankton, and abiogenic particulates from phytoplankton assemblages, respectively.

Morpho-Functional Traits Reveal Differences in Size Fractionated Phytoplankton Communities but Do Not Significantly Affect Zooplankton Grazing.

The recent emergence of approaches based on functional traits allows a more comprehensive evaluation of the role of functions and interactions within communities. As phytoplankton size and shape are the major determinants of its edibility to herbivores, alteration or loss of some morpho-functional phytoplankton traits should affect zooplankton grazing, fitness and population dynamics. Here, we investigated the response of altered phytoplankton morpho-functional trait distribution to grazing by zooplankton with contrasting food size preferences and feeding behaviors. To test this, we performed feeding trials in laboratory microcosms with size-fractionated freshwater phytoplankton (3 size classes, >30 µm; 5-30 µm and <5 µm) and two different consumer types: the cladoceran Daphnia longispina, (generalist unselective filter feeder) and the calanoid copepod Eudiaptomus sp. (selective feeder). We observed no significant changes in traits and composition between the controls and grazed phytoplankton communities. However, community composition and structure varied widely between the small and large size fractions, demonstrating the key role of size in structuring natural phytoplankton communities. Our findings also highlight the necessity to combine taxonomy and trait-based morpho-functional approaches when studying ecological dynamics in phytoplankton-zooplankton interactions.

Toxicity reduction of reverse osmosis concentrates from petrochemical wastewater by electrocoagulation and Fered-Fenton treatments.

In this work, both Electrocoagulation (EC) and Fered-Fenton (FF) technologies were used to treat reverse osmosis concentrates (ROC) from petrochemical production. The toxicity reduction capacity and mechanism were comparatively assessed during these two treatments. The results showed that FF exhibited higher capacity to reduce toxicity than EC in the 30 min treatment, which could be attributed to the removal of organic pollutants and heavy metals. The results showed that the ROC contained organics with molecular weight of 1200 g mol-1 and 220 g mol-1, which mainly consisted of the soluble microbial by-product-like and humic acid-like substances. The removal of these organics directly led to the noticeable toxicity reduction. Alkanes, haloalkanes, ketones, PAHs, and other four organic pollutants were the dominant species in the ROC, and the removal of small molecular weight organic pollutants played an essential role in reducing toxicity. FF exhibited stronger capacity to remove PAHs, BTEXS and haloalkanes, and the removal efficiencies for the PAHs were in the following order: 5-ring > 4-ring > 3-ring > 2-ring. The promotion of heavy metals removal appeared to be favorable for decreasing toxicity in ROC. This study illustrated the mechanism of the toxicity reduction and the characteristics of pollutants removal during FF and EC treatments, and provided valuable guidance for petrochemical manufacturing to the toxicity reduction and operation of wastewater treatment facilities.