Asymmetric flow field-flow fractionation for comprehensive characterization of hetero-aggregates made of nano-silver and extracellular polymeric substances.

The present study explores the capability of asymmetrical flow field-flow fractionation (AF4) coupled online with diode array (DAD), fluorescence detectors (FLD), multi-angle light scattering (MALS) and dynamic light scattering (DLS) to characterize silver nanoparticles (nAg) hetero-aggregates formed with diatoms derived extracellular polymeric substances (EPS). The content of EPS varied from 10.5 to 105 mgC L and nAg were dispersed at 4 mg L in a freshwater medium.

Aquatic organisms modulate the bioreactivity of engineered nanoparticles: focus on biomolecular corona.

The increased use of nanoparticle (NP)-enabled materials in everyday-life products have raised concerns about their environmental implications and safety. This motivated the extensive research in nanoecotoxicology showing the possibility that NPs could cause harm to the aquatic organisms if present at high concentrations. By contrast, studies dealing with influence that organisms could exert on the fate and thus effects of NPs are still very rare.

Asymmetrical Flow Field-Flow Fractionation Methods for Quantitative Determination and Size Characterization of Thiols and for Mercury Size Speciation Analysis in Organic Matter-Rich Natural Waters.

Asymmetrical flow field-flow fractionation (AF4) efficiently separates various macromolecules and nano-components of natural waters according to their hydrodynamic sizes. The online coupling of AF4 with fluorescence (Fluo) and UV absorbance (UV) detectors (FluoD and UVD, respectively) and inductively coupled plasma-mass spectrometry (ICP-MS) provides multidimensional information. This makes it a powerful tool to characterize and quantify the size distributions of organic and inorganic nano-sized components and their interaction with trace metals.

Asymmetrical Flow Field-Flow Fractionation Coupled to ICP-MS for Characterization of Trace Metal Species in the Environment from Macromolecular to Nano-Assemblage Forms: Current Challenges for Quantification.

Asymmetrical flow field-flow fractionation (AF4) is a powerful technique employed for the separation of macromolecules, nanoparticles, and their assemblages according to their hydrodynamic behavior. It is well known that at this size range, complex interactions can occur between components (e.g.

Species-specific isotope tracking of mercury uptake and transformations by pico-nanoplankton in an eutrophic lake.

The present study aims to explore the bioaccumulation and biotic transformations of inorganic (iHg) and monomethyl mercury (MMHg) by natural pico-nanoplankton community from eutrophic lake Soppen, Switzerland. Pico-nanoplankton encompass mainly bacterioplankton, mycoplankton and phytoplankton groups with size between 0.2 and 20 μm.

Dissolved Organic Matter and Associated Trace Metal Dynamics from River to Lake, Under Ice-Covered and Ice-Free Conditions.

The present study investigates the changes in dissolved organic matter (DOM) composition and its influences on trace metal dispersion from the Shuya River (SR) in the Petrozavodsk Bay of Lake Onega during ice-covered and ice-free periods. Humic substances (HS) found in the SR dominated the composition of DOM through the river-bay-lake continuum in both periods. When the bay was ice-covered, both the aromaticity and the size of HS varied in the water column according to a horizontal stratification and decreased in the bay, while under ice-free conditions, they decreased along the river-lake gradient, suggesting in both cases a decrease in the proportion of HS with high aromatic character.

Transcriptomic approach for assessment of the impact on microalga and macrophyte of in-situ exposure in river sites contaminated by chlor-alkali plant effluents.

Water quality degradation is a worldwide problem, but risk evaluation of chronic pollution in-situ is still a challenge. The present study aimed to evaluate the potential of transcriptomic analyses in representative aquatic primary producers to assess the impact of environmental pollution in-situ: the microalga Chlamydomonas reinhardtii and the macrophyte Elodea nuttallii were exposed 2 h in the Babeni Reservoir of the Olt River impacted by chlor-alkali plant effluent release resulting in increased concentrations of Hg and NaCl in receiving water. The response at the transcriptomic level was strong, resulting in up to 5485, and 8700 dysregulated genes (DG) for the microalga and for the macrophyte exposed in the most contaminated site, respectively.

Interaction of silver nanoparticles with metallothionein and ceruloplasmin: impact on metal substitution by Ag(i), corona formation and enzymatic activity.

The release of Ag(i) from silver nanoparticles (AgNPs) unintentionally spread in the environment is suspected to impair some key biological functions. In comparison with AgNO, in-depth investigations were carried out into the interactions between citrate-coated AgNPs (20 nm) and two metalloproteins, intracellular metallothionein 1 (MT1) and plasmatic ceruloplasmin (Cp), both involved in metal homeostasis. These were chosen for their physiological relevance and the diversity of their various native metals bound because of thiol groups and/or their structural differences.

Photo-transformation of pedogenic humic acid and consequences for Cd(II), Cu(II) and Pb(II) speciation and bioavailability to green microalga.

Humic substances (HS) play key role in toxic metal binding and protecting aquatic microorganisms from metal-induced stress. Any environmental changes that could alter HS concentration and reactivity can be expected to modify metal complexation and thus affect metal speciation and bioavailability to microalgae. The present study explores the influence of increased solar irradiance on the chemical structures and molecular weight of Elliott soil humic acid (EHA) and the associated consequences for Cd(II), Cu(II) and Pb(II) complexation and intracellular metal content in microalga.

Impaired liver function in Xenopus tropicalis exposed to benzo[a]pyrene: transcriptomic and metabolic evidence.

Background: Despite numerous studies suggesting that amphibians are highly sensitive to cumulative anthropogenic stresses, the role pollutants play in the decline of amphibian populations remains unclear. Amongst the most common aquatic contaminants, polycyclic aromatic hydrocarbons (PAHs) have been shown to induce several adverse effects on amphibian species in the larval stages. Conversely, adults exposed to high concentrations of the ubiquitous PAH, benzo[a]pyrene (BaP), tolerate the compound thanks to their highly efficient hepatic detoxification mechanisms.

Cell-wall-dependent effect of carboxyl-CdSe/ZnS quantum dots on lead and copper availability to green microalgae.

The present study examines the effect of carboxyl-CdSe/ZnS quantum dots (QDs) on Cu and Pb availability to microalgae with different cell wall characteristics: Chlorella kesslerii possessing a cellulosic cell wall and two strains of Chlamydomonas reinhardtii, a wall-less and a walled strain containing glycoproteins as the main cell wall component. Results demonstrated that QDs decreased Pb and Cu intracellular contents ({Cu}(int) and {Pb}(int)) in walled strains by a factor of 2.5 and 2, respectively, as expected by the decrease of about 70% and 40% in the dissolved Cu and Pb concentrations.

Toxicokinetic of benzo[a]pyrene and fipronil in female green frogs (Pelophylax kl. esculentus).

A general consensus that an increased logK(ow) led to an increase in xenobiotic uptake and bioaccumulation is accepted. In this study we compared the toxicokinetics of two chemically different xenobiotics, i.e.

Effect of humic substance photoalteration on lead bioavailability to freshwater microalgae.

The present study provides results on the influence of humic substance (HS) photoalteration on lead availability to the freshwater microalga Chlorella kesslerii . The evolution of the free lead-ion concentrations measured by the ion exchange technique [Pb](IET) and intracellular lead contents was explored in the presence of Suwannee River humic (SRHA) and fulvic (SRFA) acids, as well as Aldrich humic acid (AHA) exposed at increasing radiance doses under a solar simulator. Modifications of HS characteristics highly relevant to Pb complexation and accumulation of HS to algal surfaces, including Fourier transform infrared spectroscopy, were followed.

Colloidal organic matter from wastewater treatment plant effluents: Characterization and role in metal distribution.

Colloidal organic matter from wastewater treatment plants was characterized and examined with respect to its role in metal distribution by using tangential flow ultrafiltration, liquid chromatography coupled with organic carbon and UV detectors, and an asymmetrical flow field-flow fractionation (AFlFFF) multidetection platform. Results revealed that a humic-like fraction of low aromaticity with an average molar mass ranging from 1600 to 2600Da was the main colloidal component. High molar mass fractions (HMM), with molar mass ranges between 20 and 200kDa, were present in lower proportions.

Uptake of Cd(II) and Pb(II) by microalgae in presence of colloidal organic matter from wastewater treatment plant effluents.

The present study addresses the key issue of linking the chemical speciation to the uptake of priority pollutants Cd(II) and Pb(II) in the wastewater treatment plant effluents, with emphasis on the role of the colloidal organic matter (EfOM). Binding of Cd(II) and Pb(II) by EfOM was examined by an ion exchange technique and flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry in parallel to bioassays with green microalga Chlorella kesslerii in ultrafiltrate (<1 kDa) and colloidal isolates (1 kDa to 0.45 mum).

Determination of Ni2+ using an equilibrium ion exchange technique: Important chemical factors and applicability to environmental samples.

In natural waters, the determination of free metal concentrations is a key parameter for studying bioavailability. Unfortunately, few analytical tools are available for determining Ni speciation at the low concentrations found in natural waters. In this paper, an ion exchange technique (IET) that employs a Dowex resin is evaluated for its applicability to measure [Ni(2+)] in freshwaters.

Ni uptake by a green alga. 2. Validation of equilibrium models for competition effects.

It is generally admitted that the presence of major cations and H+ can attenuate trace metal uptake. Recent models such as the biotic ligand model (BLM) aim to quantify and predict this effect by determining stability constants for each of the major competitors for any given interaction of a trace metal with a biological organism. In this study, short-term Ni internalization fluxes (J(int)) were used to quantitatively assess the binding of H+, Mg2+, Ca2+ (K(H-Rs), K(Mg-Rs), K(Ca-Rs)), and trace metals to transport sites (R(s)) leading to Ni biouptake by Chlamydomonas reinhardtii.

Ni uptake by a green alga. 1. Validation of equilibrium models for complexation effects.

Short-term (< 60 min) internalization fluxes (J(int)) by the green alga Chlamydomonas reinhardtii were measured in the presence of a variety of ligands forming hydrophilic (citric, diglycolic, or nitrilotriacetic acids), amphiphilic (Suwannee River fulvic and humic acids), and hydrophobic (oxine, diethyldithiocarbamate) Ni complexes. Free nickel concentrations, ranging from 10(-10) to 10(-3) M, were evaluated by thermodynamic modeling and by a resin exchange technique. Ni internalization appeared to occur via a single transport site that was characterized by a conditional stability constant (pH 6.