Anaerobic denitrification has been proved to be negatively affected by ZnO nanomaterials (NPs), but little is known about how ZnO NPs affects aerobic denitrification. In this study, inhibition of ZnO NPs to an aerobic denitrifier, Pseudomonas stutzeri PCN-1, was firstly reported. The results showed total nitrogen removal efficiency was decreased from 100% to 1.70% with the increase of ZnO NPs from 1 to 128 mg/L. The presence of ZnO NPs caused significant inhibition of gene expressions and catalytic activities of nitrate reductase and nitrite reductase, which finally led to delayed nitrate reduction and high nitrite accumulation. Further studies revealed that the deposition of nanoparticles on the bacterial surface caused by electrostatic forces and the generation of reactive oxygen species (ROS) were responsible for the cytotoxicity of ZnO NPs, where ROS played a more important role. These results were of significance to evaluating the potential ecological toxicity and risks of nanomaterials. (C) 2017 Elsevier Ltd. All rights reserved.
A novel Z-scheme AgI/Bi2MoO6 hybrid photocatalyst was fabricated via a solvothermal-precipitation approach to disinfect bacteria in water. Powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopic (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscope (HRTEM), UV-vis diffuse reflectance spectra (DRS), as well as photoluminescence spectra (PL) were employed to characterize the fabricated photocatalyst. Due to the stronger redox potential and better separation of charge carriers induced by the Z-scheme structure, the optimal synthesized AgI/Bi2MoO6 exhibited excellent disinfection activity towards both Gram-negative strain Escherichia coli (E. coli) and Gram-positive strain Staphylococcus aureus (S. aureus) under visible light irradiation. 5.0 × 107 CFU mL−1 of E. coli and S. aureus cells were completely disinfected within 30 min and 90 min, respectively. Ag+ ions did not contribute to the disinfection activity, while active species including h+, ·O2−, e-, and H2O2 contributed to the cell inactivation. By changing the interaction force and being involved in the photocatalytic reactions, the common anions (Cl−, NO3−, SO42−, and H2PO4−) would affect the disinfection activity. Moreover, AgI/Bi2MoO6 exhibited effective disinfection activity in four consecutive reused cycles. Thus, AgI/Bi2MoO6 could be used as a promising photocatalyst for water disinfection.
Decabromodiphenyl ether (decaBDE) is a highly brominated flame retardant that recent studies have identified as a potential persistent organic pollutant. Large amounts of decaBDE have been consumed and released in the environment in China, while no emission inventory has been available until now. In this study, a substance flow analysis was applied to establish the emission inventory of decaBDE in China from 1982 (the first year of decaBDE production in China) until 2013 based on activity data, transfer coefficients, and emission factors. The results show that the stock of decaBDE continually increased, reaching a peak of 290,000 tons in 2007. The annual processing capacity of decaBDE also increased, and the processing capacity in 2013 was 49,000 tons. Historical accumulative emissions were estimated to be 313.3 tons from 1982 to 2013, and the annual emissions peaked in 2003 at 27.5 tons. On average, decaBDE processing was the major source (58.4%) of total emissions, followed by treatment, production, and usage processes. From 1982 to 2013, decaBDE was released mainly into water sources, accounting for 50.7% of the accumulative emissions. At the provincial level, Guangdong, Shandong, and Zhejiang provinces were the largest producers in China. Simulations produced by the level III fugacity model showed that the projected concentration was very consistent with the measured value. The stock of decaBDE in the soil and sediment phases accounted for 99.8% of the total stock, and the transfer among the four environmental phases occurred mainly at the atmosphere–soil interface.
Chlorinated paraffins (CPs) are used as flame retardants, plasticizers, and metalworking fluids, which have varying contents of toxic short-chain chlorinated paraffins (SCCPs). Based on the study of several relevant production and consumption sectors, this paper classifies the consumption of CPs among sectors and provides an emission inventory and the provincial emission distribution of SCCPs in China in 2010–2014 based on the consumption patterns and emission factors of each sector. The total emissions of SCCPs in China in 2014 were 3083.88 tons, with emissions to the atmosphere and water accounting for 894.81 tons and 2189.07 tons, respectively. The largest emission source was from metalworking fluids, with total emissions of 2459.12 tons, of which 756.65 tons went to the atmosphere and 1702.47 tons to water. Our results show that SCCP emissions were mainly concentrated in the eastern, more developed regions and that Jiangsu Province was the biggest producer in China, with total emissions of 1853.06 tons, of which 562.61 tons were to the atmosphere and 1290.46 tons to water.
Discrepancies in emission estimates of carbon tetrachloride (CCl 4 , CTC), between bottom-up and top-down methods, have been shown since the 1990s at both the global and regional scale. This study estimates the emissions of China from 1992 to 2014 based on emission functions and aggregated activity information given reasonable uncertainties. The results show that emissions increase from 7.3Gg/yr (5.6–9.1Gg/yr at 95% confidential interval) to 14.0 (9.1–19.5) Gg/yr with a growth rate of 6.7 (1.9–11.4) %/yr during 1992–2002 and then decrease to a minimum of 4.3 (1.9–8.0) Gg/yr in 2011. More than 54% of the emissions during 1992–2009 are from the process agents sector. The estimates are comparable with those of other studies and those in this study based on observations during 2011–2014 using the interspecies correlation method. China's contribution to global emissions increases from 7.5% to 19.5% during 1992–2009, but the contribution is reduced to 9.9% and 8.0% in 2010 and 2011, respectively, indicating the effectiveness of compliance with the Montreal Protocol and its subsequent Amendments and Adjustments, whereby CTC emissions are phased-out. The results of this study are beneficial for narrowing the gap between bottom-up estimates and top-down emission calculations of CTC in China.
In order to apply classical micromechanics in predicting the effective prop-erties of nanocomposites incorporating interface energy, a concept of equivalent inclusion (EI) is usually adopted. The properties of EI are obtained by embedding a single inclusion with the interface into an infinite matrix. However, whether such an EI is universal for different micromechanics-based methods is rarely discussed in the literature. In this pa-per, the interface energy theory is used to study the applicability of the above mentioned EI. It is found that some elastic properties of the EI are related only to the properties of the inclusion and the interface, whereas others are also related to the properties of the matrix. The former properties of the EI can be applied to both the classical Mori-Tanaka method (MTM) and the generalized self-consistent method (GSCM). However, the latter can be applied only to the MTM. Two kinds of new EIs are proposed for the GSCM and used to estimate the effective mechanical properties of nanocomposites.
In order to apply classical micromechanics in predicting the effective prop-erties of nanocomposites incorporating interface energy, a concept of equivalent inclusion (EI) is usually adopted. The properties of EI are obtained by embedding a single inclusion with the interface into an infinite matrix. However, whether such an EI is universal for different micromechanics-based methods is rarely discussed in the literature. In this pa-per, the interface energy theory is used to study the applicability of the above mentioned EI. It is found that some elastic properties of the EI are related only to the properties of the inclusion and the interface, whereas others are also related to the properties of the matrix. The former properties of the EI can be applied to both the classical Mori-Tanaka method (MTM) and the generalized self-consistent method (GSCM). However, the latter can be applied only to the MTM. Two kinds of new EIs are proposed for the GSCM and used to estimate the effective mechanical properties of nanocomposites.
Based on a time-series dataset and the mass balance method, the contributions of various sources to the nutrient discharges from the Yangtze River to the East China Sea are identified. The results indicate that the nutrient concentrations vary considerably among different sections of the Yangtze River. Non-point sources are an important source of nutrients to the Yangtze River, contributing about 36% and 63% of the nitrogen and phosphorus discharged into the East China Sea, respectively. Nutrient inputs from non-point sources vary among the sections of the Yangtze River, and the contributions of non-point sources increase from upstream to downstream. Considering the rice growing patterns in the Yangtze River Basin, the synchrony of rice tillering and the wet seasons might be an important cause of the high nutrient discharge from the non-point sources. Based on our calculations, a reduction of 0.99 Tg per year in total nitrogen discharges from the Yangtze River would be needed to limit the occurrences of harmful algal blooms in the East China Sea to 15 times per year. The extensive construction of sewage treatment plants in urban areas may have only a limited effect on reducing the occurrences of harmful algal blooms in the future. (C) 2016 Elsevier B.V. All rights reserved.