Hydraulic fracturing (HF) has emerged as a major method of unconventional oil and gas recovery. The toxicity of hydraulic fracturing flowback and produced water (HF-FPW) has not been previously reported and is complicated by the combined complexity of organic and inorganic constituents in HF fluids and deep formation water. In this study, we characterized the solids, salts, and organic signatures in an HF-FPW sample from the Duvernay Formation, Alberta, Canada. Untargeted HPLC-Orbitrap revealed numerous unknown dissolved polar organics. Among the most prominent peaks, a substituted tri-phenyl phosphate was identified which is likely an oxidation product of a common polymer antioxidant. Acute toxicity of zebrafish embryo was attributable to high salinity and organic contaminants in HF-FPW with LC50 values ranging from 0.6% to 3.9%, depending on the HF-FPW fractions and embryo developmental stages. Induction of ethoxyresorufin-O-deethylase (EROD) activity was detected, due in part to polycyclic aromatic hydrocarbons (PAHs), and suspended solids might have a synergistic effect on EROD induction. This study demonstrates that toxicological profiling of real HF-FPW sample presents great challenges for assessing the potential risks and impacts posed by HF-FPW spills.

Two-dimensional (2D) hexagonal boron nitride (h-BN) is one of the most promising materials for many technological applications ranging from optics to electronics. In past years, a property-tunable strategy that involves the construction of electronic structures of h-BN through an atomic-level design of point defects has been in vogue. The point defects imported during material synthesis or functionalization by defect engineering can endow h-BN with new physical characteristics and applications. In this Perspective, we survey the current state of the art in multifunction variations induced by point defects for 2D h-BN. We begin with an introduction of the band structure and electronic property of the pristine h-BN. Subsequently, the formation and characterization of the most obvious point defects and their modulation in electronic structures of h-BN nanomaterials are envisaged in theory. The experimental results obtained by atom-resolved transmission electron microscopy, magnetic measurement, and optical measurements have provided insights into the point defect engineered structures and their corresponding emerging properties. Finally, we highlight the perspectives of h-BN nanomaterials for heterostructures and devices. This Perspective provides a landscape of the point defect physics involved to demonstrate the modulation of the structure and functionalities in h-BN and identify the roadmap for heterostructure and device applications, which will make advances in electronics, spintronics, and nanophotonics.

Particulate matter is one of the main pollutants, causing hazy days, and it has been serious concern for public health worldwide, particularly in China recently. Quality of outdoor atmosphere with a pollutant emission of PM2.5 is hard to be controlled; but the quality of indoor air could be achieved by using fibrous membrane-based airfiltering devices. Herein, we introduce nanofiber membranes for both indoor and outdoor air protection by electrospun synthesized polyacrylonitrile:TiO 2 and developed polyacrylonitrile-co-polyacrylate:TiO 2 composite nanofiber membranes. In this study, we design both polyacrylonitrile:TiO 2 and polyacrylonitrile-co-polyacrylate:TiO 2 nanofiber membranes with controlling the nanofiber diameter and membrane thickness and enable strong particulate matter adhesion to increase the absorptive performance and by synthesizing the specific microstructure of different layers of nanofiber membranes. Our study shows that the developed polyacrylonitrile-co-polyacrylate: TiO 2 nanofiber membrane achieves highly effective (99.95% removal of PM2.5) under extreme hazy air-quality conditions (PM2.5 mass concentration 1 mg/m 3 ). Moreover, the experimental simulation of the test in 1 cm 3 air storehouse shows that the polyacrylonitrile-co-polyacrylate:TiO 2 nanofiber membrane (1 g/m 2 ) has the excellent PM 2.5 removal efficiency of 99.99% in 30 min.

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