Stability of arsenic(Ⅲ, Ⅴ) in galvanized steel pipe scales coexisting with colloidal polystyrene microplastics under drinking water conditions

Polyamide 6 microplastics as carriers led to changes in the fate of bisphenol A and dibutyl phthalate in drinking water distribution systems: The role of adsorption and interfacial partitioning

Microplastics (MPs) co-exist with plastic additives and other emerging pollutants in the drinking water distribution systems (DWDSs). Due to their strong adsorption capacity, MPs may influence the occurrence of additives in DWDSs. The article investigated the occurrence of typical additives bisphenol A (BPA) and dibutyl phthalate (DBP) in DWDSs under the influence of polyamide 6 (PA6) MPs and further discussed the partitioning of BPA/DBP on PA6s, filling a research gap regarding the impact of adsorption between contaminants on their occurrence within DWDSs. In this study, adsorption experiments of BPA/DBP with PA6s and pipe scales were conducted and their interaction mechanisms were investigated. Competitive adsorption experiments of BPA/DBP were also carried out with site energy distribution theory (SEDT) calculations. The results demonstrated that PA6s might contribute to the accumulation of BPA/DBP on pipe scales. The adsorption efficiencies of BPA/DBP with both PA6s and pipe scales were 26.47 and 2.61 times higher than those with only pipe scales. It was noteworthy that BPA had a synergistic effect on the adsorption of DBP on PA6s, resulting in a 26.47 % increase in DBP adsorption. The article provides valuable insights for the compounding effect of different types of additives in water quality monitoring and evaluation.

Cu fate driven by colloidal polystyrene microplastics with pipe scale destabilization in drinking water distribution systems

Microplastics (MPs) and Cu have been detected in drinking water distribution systems (DWDSs). Investigating MP effects on Cu adsorption by pipe scales and concomitant variations of pipe scales was critical for improving the water quality, which remained unclear to date. Therefore, polystyrene microplastics (PSMPs) were adopted for the model MPs to determine their effects on Cu fate and pipe scale stabilization, containing batch adsorption, metal speciation extraction, and Cu release experiments. Findings demonstrated that complexation and electrostatic interactions were involved in Cu adsorption on pipe scales. PSMPs contributed to Cu adsorption via increasing negative charges of pipe scales and providing additional adsorption sites for Cu, which included the carrying and component effects of free and adsorbed PSMPs, respectively. The decreased iron and manganese oxides fraction (45.57 % to 29.91 %) and increased organic fraction (48.51 % to 63.58 %) of Cu in pipe scales when PSMPs were coexisting illustrated that PSMPs had a greater affinity for Cu than pipe scales and thus influenced its mobility. Additionally, the release of Cu could be facilitated by the coexisted PSMPs, with the destabilization of pipe scales. This study was the first to exhibit that Cu fate and pipe scale stabilization were impacted by MPs, providing new insight into MP hazards in DWDSs.

Tracking anthropogenic microparticles in wildlife of an alpine insular environment

Despite the isolation of remote natural regions, it has been discovered that they are experiencing the accumulation of anthropogenic microparticles (i.e., microplastics or natural or semisynthetic cellulosic particles). Teide National Park (Canary Islands, Spain) is a high-mountain protected area known for its rich biodiversity. This study aims to assess the occurrence of coloured anthropogenic particles in the faecal matter of wild mammals, specifically rabbits and mouflons, residing in the park. With this purpose, faeces were collected from 68 systematically distributed sampling points. A stereomicroscopy-guided grinding process allowed a chemical-free and quick visual inspection of 616 individual excreta, revealing that 96% were particle-free. However, 37 anthropogenic particles were found, which correspond to 0.79 ± 0.20 items per gram of dry faecal matter. The archetypical particle was a cellulosic blue microfibre of 2721 ± 407 µm, though poly(ethylene-vinyl acetate) and polypropylene were also identified via micro Fourier-transform infrared spectroscopic analysis. Atmospheric deposition and touristic pressure may be the sources of the anthropogenic particles, as they were randomly found in 36% of the sampling points. These findings represent the first evidence of anthropogenic particle ingestion by wild rabbits and mouflons, signifying the introduction of microplastics into terrestrial food chains in a remote high-mountain environment.

Interaction mechanism of water-soluble inorganic arsenic onto pristine nanoplastics

Nanoplastics (NPLs) persist in aquatic habitats, leading to incremental research on their interaction mechanisms with metalloids in the environment. In this regard, it is known that plastic debris can reduce the number of water-soluble arsenicals in contaminated environments. Here, the arsenic interaction mechanism with pure NPLs, such as polyethylene terephthalate (PET), aliphatic polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and polystyrene (PS) is evaluated using computational chemistry tools. Our results show that arsenic forms stable monolayers on NPLs through surface adsorption, with adsorption energies of 9-24 kcal/mol comparable to those on minerals and composite materials. NPLs exhibit varying affinity towards arsenic based on their composition, with As(V) adsorption showing higher stability than As(III). The adsorption mechanism results from a balance between electrostatics and dispersion forces (physisorption), with an average combined contribution of 87%. PA, PET, PVC, and PS maximize the electrostatic effects over dispersion forces, while PE and PP maximize the dispersion forces over electrostatic effects. The electrostatic contribution is attributed to hydrogen bonding and the activation of terminal O-C, C-H, and C-Cl groups of NPLs, resulting in several pairwise interactions with arsenic. Moreover, NPLs polarity enables high mobility in aqueous environments and fast mass transfer. Upon adsorption, As(III) keeps the NPLs polarity, while As(V) limits subsequent uptake but ensures high mobility in water. The solvation process is destabilizing, and the higher the NPL polarity, the higher the solvation energy penalty. Finally, the mechanistic understanding explains how temperature, pressure, pH, salinity, and aging affect arsenic adsorption. This study provides reliable quantitative data for sorption and kinetic experiments on plastic pollution and enhances our understanding of interactions between water contaminants.

Chromium immobilization and release by pipe scales in drinking water distribution systems: The impact of anions

Due to its high toxicity, the release of chromium (Cr) by pipe scales poses a serious risk to drinking water quality and human health. This study looked into how Cr immobilized and released by pipe scales. SEM, XRD, and XPS were applied to evaluate the physicochemical characterization of pipe scales. To identify times of immobilization and release and the proper scale to water ratio, the behaviors of Cr were examined in stagnation experiments. Afterward, the common anions in drinking water were designed as nine concentration gradients to explore their species and concentrations impacts on the immobilization and release process of Cr. It is worth mentioning that the pipe scales were classified into block pipe scales, lumpy pipe scales, and powder pipe scales in this experiment. The types of pipe scales were rarely considered as an influencing factor. Results revealed that in contrast to powder pipe scales, block pipe scales and lumpy pipe scales exhibited extremely comparable trends. Specifically, in terms of accumulation capacity, the order from largest to smallest was powder pipe scales, lumpy pipe scales, and block pipe scales. However, the potential of Cr release from block pipe scales was the highest, indicating a high danger of heavy metal re-release in actual circumstances. Findings from this study discovered the turning points of chloride and sulfate concentrations associated with the pipe scales species in the anion-promoted release. These results provide insight into the relationship between pipe scales and Cr in drinking water distribution systems (DWDS).