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The purpose of this study was to investigate the impact of long-term application of pig manure on the accumulation of heavy metals, antibiotics and ARGs in surface soil sampled from the Jiaxing long-term field experimental site with three manure treatments, N-PM (0 kg/ha/y, dw), L-PM (7720 kg/ha/y, dw), and H-PM (11,580 kg/ha/y, dw), in 2013 and 2014. The results showed that most serious metal pollution of Zn and Cu was recorded in all manured samples in both years, and their contents exceeded the soil quality standards. Among the three tetracyclines, chlortetracycline was the predominant antibiotic detected with a range of 3.04–98.03 μg·kg −1 in 2013 and 28.67–344.74 μg·kg −1 in 2014 after long-term pig manure application. Q-PCR results showed that the average accumulation of ribosomal protection protein genes ( tet M, tet O, tet Q and tet W) was lower than most of the efflux pump genes ( tet A and tet G). The abundance of tet and sul genes of those sites with manure application was significantly higher than that of sites without manure application in both years. Metagenomics analysis of ARGs revealed that the abundance of multidrug resistance genes was the most abundant subtype, followed by fluoroquinolone, bacitracin, sulfonamide and tetracycline. There was a positive correlation between the levels of ARGs; soil organic matter, antibiotics, Cu, As, and Zn levels in both years. These results may shed light on the mechanism underlining the effects of long-term manure application on the occurrence and dissemination of ARGs in surface soil. [ABSTRACT FROM AUTHOR]

Water contamination by heavy metals is a serious environmental concern. To unravel the "species resolved" interaction mechanism of heavy metals with graphene oxide (GO), a multi-aspects analyses incorporating metal species distribution, GO surface charge, adsorption behavior and fitting, hard-soft acid-base (HSAB) theory, Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy were performed. For pH 7 and T = 25 °C, adsorptions of aqueous Cd(Ⅱ) and Pb(Ⅱ) with equal initial concentrations of 300 mg L−1 by GO at 500 mg L−1 equilibrated in 15 min. The corresponding adsorption percentage and quantity for Cd(Ⅱ) were 98.04% and 588.22 mg g−1 and those for Pb(Ⅱ) were 92.10% and 552.56 mg g−1. When pH ≤ 7, bare Cd2+ and Pb2+ were the dominant metal species adsorbed by GO via ion exchange and chemical complexation. When pH ≥ 7, hydroxyl-complexed species were the dominant ones adsorbed by GO via precipitation, ion exchange, and chemical complexation. Electron transfer and energy lowering induced by the GO–heavy metal interaction, calculated based on HSAB theory, illuminated two points: (1) OH had a stronger binding affinity than COOH toward either Cd(Ⅱ) or Pb(Ⅱ) and (2) either OH or COOH had a stronger binding affinity toward Cd(Ⅱ) than Pb(Ⅱ). Explorations of this work may provide guidance in developing efficient graphene-based adsorbents for wastewater remediation. [Display omitted] • An improved Hummers method was utilized to prepare graphene oxide (GO). • GO adsorbs 588.22 mg g−1 or 552.56 mg g−1 of Cd(Ⅱ) or Pb(Ⅱ) in 15 min. • The "species resolved" adsorption mechanism was unveiled. • The hard-soft acid-base theory was incorporated to unravel the adsorption mechanism. • Different pH range gives rise to different adsorption mechanism. [ABSTRACT FROM AUTHOR]

Excessive discharge of heavy metals by industrial activities has caused severe environmental problem. In this work, a magnetic graphene oxide nanocomposite (MGON) based on graphene oxide-Fe 3 O 4 framework was prepared, characterized and employed as adsorbent to remove aqueous Mn(Ⅱ), Zn(Ⅱ) efficiently. The adsorption performance and mechanism were investigated carefully. Results suggest, the mutual enhancement between GO and Fe 3 O 4 brings synergistic effect on adsorption performance, which enables MGON to outperform either of the two single phase. In particular, MGON efficiently adsorbs 399.67 mg g−1, 372.98 mg g−1 of Mn(Ⅱ), Zn(Ⅱ) in 4 min, 6 min, respectively. What is more, MGON can be readily recovered via magnetic separation for further recycling. The thermodynamic parameters of the adsorptions under 298.15 K are: Δ H = 20.86 kJ mol−1, Δ S = 108.84 J K−1 mol−1, Δ G = −11.59 kJ mol−1 for Mn(Ⅱ) and Δ H = 20.99 kJ mol−1, Δ S = 96.04 J K−1 mol−1, Δ G = −7.64 kJ mol−1 for Zn(Ⅱ), respectively, indicating spontaneous, endothermic and entropy increasing features. Both adsorptions fit well by the Freundlich, pseudo second order, and intra-particle diffusion models. Furthermore, adsorption mechanism is based on the chemical interaction of the oxygen atoms in C O, C-O related groups with Mn(Ⅱ), Zn(Ⅱ). The high adsorption efficiency suggests that MGON has promising application in heavy metal treatment. Schematic illustration of MGON preparation, heavy metal adsorption and magnetic separation from aqueous solution (M(Ⅱ) denotes divalent heavy metal). [Display omitted] • Magnetic graphene oxide nanocomposite (MGON) was prepared and characterized. • MGON adsorbed 399.67 mg g−1, 372.98 mg g−1 of Mn(Ⅱ), Zn(Ⅱ) in 4 min, 6 min. • MGON can be readily recovered via magnetic separation for further recycling. • Adsorption rate is controlled by intra-particle diffusion and chemical interaction. • Oxygen atoms in C O, C-O related groups chemically interact with Mn(Ⅱ), Zn(Ⅱ). [ABSTRACT FROM AUTHOR]

The depletion of phosphorus resources and the excess discharge of phosphorus into waste streams are contrasting problems. The key to solving both problems is to recover phosphorus from the waste streams. Current phosphorus recovery technologies require high phosphorus concentrations and lack the ability to separate toxic substances from recovered phosphorus products. Membrane separation processes such as nanofiltration, forward osmosis, and electrodialysis are examples of effective methods for solving some of these issues. In this paper, the mechanisms, performance, and influential factors affect phosphorus recovery from membrane separation are reviewed. Membrane fouling, energy consumption, and the selectivity of toxic substances in membrane separation processes were evaluated. This work will serve as a basis for future research and development of phosphorus recovery by membrane separation processes and as a response to the increasingly pressing issues of eutrophication and the growing depletion of phosphorus resources. Unlabelled Image • Membrane separation processes for P recovery are reviewed. • Performance on membrane fouling, energy consumption, and selectivity was evaluated. • Prospects of membrane separation processes for P recovery are presented. [ABSTRACT FROM AUTHOR]

Nanoparticle capping agents are critical for controlling the growth, oxidation state, and final particle size during aqueous synthesis. However, despite the known phytotoxicity of cetyltrimethylammonium bromide (CTAB) to plants, it is used to synthesize metal oxide nanoparticles of uniform size and with mesoporous structure. Among the few studies that have investigated how CTAB influences nanoparticle toxicity, CTAB has never been identified as the primary cause of nanoparticle toxicity in environmental systems; rather nanoparticle surface charge or morphology was identified as the driver of toxicity in environmentally relevant systems. In the current study, CTAB release from CTAB surface modified Cu 2 O nanoparticles (SM-Cu 2 O NPs) inhibited duckweed (Landoltia punctata) growth, even when administered at subtoxic Cu concentrations. Organic ligands, such as humic acid (HA) and ethylenediaminetetraacetic acid (EDTA), lessened growth inhibition associated with exposure to SM-Cu 2 O NPs, likely through electrostatic and hydrophobic interactions with CTAB. Such results highlight the need for a more holistic approach to nanoparticle surface modification and improved communication between toxicologists and synthetic chemists to develop green alternatives for nanoparticle synthesis. Surface modification of metal oxide nanoparticles with CTAB, applied to improve nanoparticle uniformity and performance under specific conditions, may induce environmental toxicity at sub-toxic metal concentrations. Unlabelled Image • Released CTAB surface coatings can induce negative growth response in plants. • Ligands can alter the magnitude of the negative growth response to CTAB. • Green nanoparticle formulation can mitigate nanoparticle effects in natural systems. [ABSTRACT FROM AUTHOR]