Extracellular polymeric substances (EPS) from bloom-forming cyanobacteria exist ubiquitously in eutrophic waters, while their effects on the aggregation/stabilization of nanoparticles remain unknown. In this study, the stability of ZnO nanoparticles (ZNPs) upon adsorption of cyanobacterial EPS was investigated by using two dimensional ATR-FTIR correlation spectroscopy, XPS and DLVO theory. Results showed that the adsorption process followed the Langmuir isotherm and pseudo-second-order kinetics both for the total organic contents as well as the individual parallel factor-derived components. The physicochemical and spectroscopic techniques revealed the mechanism of both electrostatic attraction and surface complexation in EPS adsorption. Further analysis showed increased absorbance and turbidity of ZNPs solutions with EPS addition, demonstrating the enhanced colloidal stability. The DLVO theory explained that the increased energy barriers and values of second energy maximum were responsible for the stability enhancement. This study facilitates a deeper insight into the environmental behavior of nanoparticles in eutrophic algae-rich waters.

Dissolved organic matter (DOM) and carbon nanotubes are introduced into aquatic environments. Thus, it is important to elucidate whether their interaction affects DOM amount and composition. In this study, the composition of DOM, before and after interactions with single-walled carbon nanotubes (SWCNTs), was measured and the adsorption affinity of the individual structural fractions of DOM to SWCNTs was investigated. Adsorption of DOM to SWCNTs was dominated by the hydrophobic acid fraction, resulting in relative enhancement of the hydrophilic character of non-adsorbed DOM. The preferential adsorption of the HoA fraction was concentration-dependent, increasing with increasing concentration. Adsorption affinities of bulk DOM calculated as the normalized sum of affinities of the individual structural fractions were similar to the measured affinities, suggesting that the structural fractions of DOM act as independent adsorbates. The altered DOM composition may affect the nature and reactivity of DOM in aquatic environments polluted with carbon nanotubes.

Levels of polybrominated diphenyl ethers (PBDEs) and dechlorane plus (DPs) were investigated in the Indus River Basin from Pakistan. Concentrations of ∑PBDEs and ∑DPs were ranged between 0.05 and 2.38 and 0.002–0.53 ng g−1 in the surface soils while 1.43–22.1 and 0.19–7.59 pg m−3 in the passive air samples, respectively. Black carbon (fBC) and total organic carbon (fTOC) fractions were also measured and ranged between 0.73 and 1.75 and 0.04–0.2%, respectively. The statistical analysis revealed strong influence of fBC than fTOC on the distribution of PBDEs and DPs in the Indus River Basin soils. BDE's congener profile suggested the input of penta–bromodiphenylether (DE-71) commercial formulation in the study area. Soil–air partitioning of PBDEs were investigated by employing octanol-air partition coefficients (KOA) and black carbon-air partition coefficients (KBC−A). The results of both models suggested the combined influence of total organic carbon (absorption) and black carbon (adsorption) in the studied area.

The effects of chironomid larvae bioturbation on the lability of phosphorus (P) in sediments were investigated through sediment incubation for 140 days. High-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were applied to obtain soluble and labile P/Fe profiles at a millimeter resolution, respectively. The larvae bioturbation decreased concentrations of soluble/labile P and Fe by up to over half of the control at the sediment depths of influence up to 70 and 90 mm respectively. These effects continued over 116 days and disappeared on the 140th days due to eclosion of chironomid larvae. Labile P was highly correlated with labile Fe, while a weak correlation was observed between soluble P and soluble Fe. It was concluded that Fe(II) oxidation and its enhanced adsorption were the major mechanisms responsible for the decreases of soluble and labile P.

LSER models for organic compounds adsorption by single and multi-walled carbon nanotubes and activated carbon were successfully developed. The cavity formation and dispersion interactions (vV), hydrogen bond acidity interactions (bB) and π-/n-electron interactions (eE) are the most influential adsorption mechanisms. SWCNTs is more polarizable, less polar, more hydrophobic, and has weaker hydrogen bond accepting and donating abilities than MWCNTs and AC. Compared with SWCNTs and MWCNTs, AC has much less hydrophobic and less hydrophilic adsorption sites. The regression coefficients (e, s, a, b, v) vary in different ways with increasing chemical saturation. Nonspecific interactions (represented by eE and vV) have great positive contribution to organic compounds adsorption, and follow the order of SWCNTs > MWCNTs > AC, while hydrogen bond interactions (represented by aA and bB) demonstrate negative contribution. These models will be valuable for understanding adsorption mechanisms, comparing adsorbent characteristics, and selecting the proper adsorbents for certain organic compounds.

The implications of biochar aging regarding their material properties as well as their interactions with other contaminants are not vivid. We report the role of biochar aging on sorption behavior of di-alkyl phthalates (PAEs). Biochars used in this study were produced from peanut-shell and their aging was simulated by chemical oxidation. The structural composition and morphology of the obtained biochars, before and after oxidation with HNO3/H2SO4, were analyzed by element composition, XPS, DRIFT, and SEM/EDX. Several experimental results unequivocally showed oxygen enrichment in the mixed acid treated samples compared to their precursors. Despite surface area reduction and pore destruction, increased PAEs sorption on oxidized biochar surfaces portrayed existence of strong PAEs binding sites. The adsorption of PAEs on oxidized biochar surface is a cumulative influence of hydrophobic interactions and pi–pi electron donor–acceptor interactions. Our results suggest that imminent aging of biochar upon environmental exposure may change their sorbent properties.

The removal efficiency of sediment phosphorus (P) in all fractions with a combined technology of porous ceramic filter media (PCFM) and submerged macrophytes was studied in Donghu Lake, Wuhan, China. The adsorption kinetic models of the sediment P in all fractions on PCFM could be described well by a power function equations (Qt = k · ta, 0 < a < 1). The P removal capacity of the combination of PCFM and Potamogeton crispus, a submerged macrophyte, was higher for all P forms than that of the combination of PCFM and another macrophyte, Vallisneria spiralis. This study suggested that the combination of PCFM and macrophytes could achieve a synergetic sediment P removal because the removal rates of the combinations were higher than the sum of that of PCFM and macrophytes used separately. The combined technology could be further applied to treat internal P loading in eutrophic waters.

This study aimed to determine whether the uptake and localization of Ag in zebrafish was affected by the presence of polyethylene microplastic beads (PE MPBs). Zebrafish were exposed to 1 μg Ag L−1 (radiolabelled with 110mAg) for 4 and 24 h in the presence or absence of PE MPBs (10, 100 or 1000 MPBs mL−1), and one treatment in which MPBs (1000 MPBs mL−1) were incubated with Ag to promote adsorption. The presence of MPBs, at any of the tested doses, had no effect on the uptake or localization of Ag. However, exposure to the Ag-incubated MPBs (∽75% of the Ag bound to MPBs) significantly reduced Ag uptake at both time points and also significantly increased the proportion of intestinal Ag. This study demonstrates that microplastics can alter the bioavailability and uptake route of a metal contaminant in a model fish species.

With extensive application of diverse engineered nanoparticles (NPs), multiple NPs would inevitably be released into the environment. However, much emphasis in most previous studies on the interactions of pollutants with NPs has been placed on only one type of NPs at a time. This study investigated the impact of inorganic NPs (I-NPs) on the adsorption of 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) by multi-walled carbon nanotubes (CNTs). The presence of I-NPs inhibited the adsorption and increased the equilibrium time of E2 and EE2 by CNTs. Moreover, the effect of Al2O3 was stronger than that of SiO2, because electrostatic attraction enhanced the interaction between oppositely charged Al2O3 and CNTs. The addition sequence of I-NPs and pollutant also influences adsorption. This is among the first studies investigating the effect of I-NPs on pollutants adsorption by CNTs, which is useful for understanding the transport and fate of CNTs and contaminants in natural aquatic systems.

The abiotic transformation of nanomaterials in the natural environment can significantly affect their fate, transport, and effects. We observed that the adsorption affinities of graphene oxide nanoparticles (GONPs) for both phenanthrene and 1-naphthol were profoundly enhanced in the presence of sulfide, an environmentally relevant reductant, with doses as low as 0.5 mM Na2S per 10 mg/L GONPs. For phenanthrene adsorption enhancement was predominantly caused by the increased surface hydrophobicity from Na2S treatment. For 1-naphthol, however, adsorption enhancement was caused mainly by the conversion of the epoxy/ether groups on the surface of graphene oxide (GO) to the phenolic hydroxyl and carbonyl groups, which allowed more significant H-bonding between 1-naphthol and GONPs. The findings of this study underline that abiotic transformation of GO not only affects the stability and mobility of GONPs, but also influences the adsorptive interactions between GONPs and environmental contaminants, and consequently, may increase the environmental risks of GONPs.