Photoaged polystyrene nanoplastics exposure results in reproductive toxicity due to oxidative damage in Caenorhabditis elegans.

The increase of plastic production together with the incipient reuse/recycling system has resulted in massive discards into the environment. This has facilitated the formation of micro- and nanoplastics (MNPs) which poses major risk for environmental health. Although some studies have investigated the effects of pristine MNPs on reproductive health, the effects of weathered MNPs have been poorly investigated. Here we show in Caenorhabditis elegans that exposure to photoaged polystyrene nanoplastics (PSNP-UV) results in worse reproductive performance than pristine PSNP (i.e., embryonic/larval lethality plus a decrease in the brood size, accompanied by a high number of unfertilized eggs), besides it affects size and locomotion behavior. Those effects were potentially generated by reactive products formed during UV-irradiation, since we found higher levels of reactive oxygen species and increased expression of GST-4 in worms exposed to PSNP-UV. Those results are supported by physical-chemical characterization analyses which indicate significant formation of oxidative degradation products from PSNP under UV-C irradiation. Our study also demonstrates that PSNP accumulate predominantly in the gastrointestinal tract of C. elegans (with no accumulation in the gonads), being completely eliminated at 96 h post-exposure. We complemented the toxicological analysis of PSNP/PSNP-UV by showing that the activation of the stress response via DAF-16 is dependent of the nanoplastics accumulation. Our data suggest that exposure to the wild PSNP, i.e., polystyrene nanoplastics more similar to those actually found in the environment, results in more important reprotoxic effects. This is associated with the presence of degradation products formed during UV-C irradiation and their interaction with biological targets.

Thermal degradation of calcium and sodium alginate: A greener synthesis towards calcium oxide micro/nanoparticles.

Processes for nanoparticle synthesis often use toxic solvents under aggressive conditions. A greener alternative is the burning of self-organized alginate systems. We followed the influence of the CaCl2 concentrations during gelation of sodium alginate and the heating rate on the synthesis of nanoparticles by the combustion method using TGA as a reactor vessel. Samples were collected after each main process of mass loss and characterized using the Scanning Electron Microscopy, Infrared Spectroscopy, and X-ray Diffraction. Samples treated at 50 °C·min-1 presented porous structures at temperatures more than 500 °C lower than the treatments at 10 °C·min-1. All calcium alginate samples presented changing from a predominantly amorphous to crystalline structures such as Ca(OH)2, CaCO3 in the calcite phase and CaO as a function of the temperature, while sodium alginate produced mainly Na2CO3, NaOH and NaO. We observed two main correlations: 1) between the porosity and the heating rate, and 2) between the formation of crystalline structure in intermediate temperatures and the CaCl2 concentration in the gelation step.

Natural organic matter residue as a low cost adsorbent for aluminum.

The contamination of aquatic and terrestrial environments by potentially toxic metals is highlighted by the possible impacts that their high availability can have on the environment. Thus, the development of alternative absorbents that can be used in the remediation of contaminated areas is of great environmental interest. Humin, one of the fractions of natural organic matter, is a promising alternative in studies on the retention of different metals that are environmentally toxic. In this study, the influence of the organic and inorganic humin constituents that are involved in the retention of aluminum species was evaluated. After extraction and calcination to obtain the ashes (inorganic constituents), humin and ash samples were structurally characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Interaction studies between aluminum-humin and ash-humin were performed in the pH range of 4.0-8.0 and with various contact times. The results of the characterization of humin and ash showed different functional groups present in the structures of these materials. Based on the results of the interaction between humin-aluminum and ash-aluminum, it can be inferred that both the organic and inorganic components of humin are efficient at absorbing aluminum. However, the adsorption isotherms showed that humin and the ashes have different adsorption behaviors. Humin is the only fraction of natural organic matter with a significant inorganic constituent content; it is the fraction least used by researchers in this field and is often discarded as waste. In light of this, the results obtained in this work highlight the importance of humin as a natural adsorbent material. Humin may be promising for the removal of aluminum species in contaminated environments due to the presence of organic and inorganic constituents.

Ion exchange kinetics of magnetic alginate ferrogel beads produced by external gelation.

This paper reports on a study of the influence of sodium alginate concentration and iron addition on the ion exchange kinetics of calcium alginate ferrogel beads produced by external gelation. The calcium absorption and sodium release of the beads were fitted to Fick's second law for unsteady state diffusion in order to obtain the effective diffusion coefficients of Na(+) and Ca(2+). The dried beads were characterized concerning their thermal stability, particle size distribution and morphology. The gelation kinetics showed that an increase in alginate concentration from 1% to 2% increased the Ca(2+) equilibrium concentration, but presented no effect on Ca(2+) effective diffusion coefficient. Alginate concentration higher than 2% promoted saturation of binding sites at the bead surfaces. The addition of iron promoted faster diffusion of Ca(2+) inside the gel beads and reduced the Ca(2+) equilibrium concentration. Also, iron particles entrapped in the alginate gel beads promoted greater absorption of water compared to pure alginate gel and lower thermal stability of the beads. The main diffusion of Ca(2+) into and Na(+) out from the bead took place during the first 60 min, during which almost 85-90% of the Ca(2+) equilibrium concentration is achieved, indicating that this period is sufficient to produce a Ca-alginate bead with high crosslinking of the polymer network.