Chromium accumulated from source water and pipeline lining materials in corrosion scales could potentially be released into bulk water in drinking water distribution systems (DWDS). This study ...examined the influence of pH (pH 4, pH 5.5, pH 7, pH 8.5, pH 10), temperature (5 °C, 15 °C, 25 °C), sulfate (50 mg/L, 150 mg/L, 250 mg/L), and chloride (50 mg/L, 150 mg/L, 250 mg/L) on chromium accumulation and release between iron corrosion scale phase and the surrounding water phase. For the first time, the accumulation and release behaviors of chromium were assessed and compared in two distinct layers of iron corrosion scales based on the speciation distributions of heavy metals. Results showed that in the outer and inner layers of corrosion scales, chromium exhibited an almost similar trend but significant differences in quantity, with the outer layer accumulating less and releasing more. In particular, the average difference of chromium released after Cr(VI) enrichment from the outer and inner layers was 50.53 μg/L under the same conditions. Further studies conclusively showed that in Cr(VI) accumulation process, a portion of Cr(VI) would be reduced to Cr(III) by Fe(II) in iron corrosion scales. The mechanisms of chromium retention based on different iron (oxyhydr)oxides were discussed.
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Microplastics (MPs) and antibiotics (ATs) have been detected in various aquatic environments and characterized as novel contaminants that have attracted worldwide attention. This review summarizes ...the characteristics of MPs and ATs, analyzes the sources of MPs and ATs in aquatic environments, reviews the concentration distribution of the two pollutants in China, and introduces the environmental effects of mixing MPs and ATs. Studies on single pollutants of MPs or ATs are well established, but the interactions between the two in aquatic environments are rarely mentioned. The physicochemical characteristics of MPs make them carriers of ATs, which greatly increase their risk of being potential hazards to the environment. Therefore, in this article, the interaction mechanisms between MPs and ATs are systematically sorted out, mainly including hydrophobic, electrostatic, intermolecular interactions, microporous filling, charge-assisted hydrogen bonding, cation-bonding, halogen bonding, and CH/π interactions. Also, factors affecting the interaction between ATs and MPs, such as the physicochemical properties of MPs and ATs and environmental factors, are also considered. Finally, this review identifies some new research topics and challenges for MPs and ATs, in order to gain deeper insight into their behavioral fate and toxic mechanisms.
In this study, the optimal conditions and effects of external factors on tetracycline adsorption by magnetic multi-walled carbon nanotubes (MMWCNTs) were established by a response surface methodology ...for the first time. Batch adsorption experiments showed that increasing the dosage and contact time effectively promoted the adsorption of tetracycline and maximum removal of 97.93–99.13% was achieved at pH 3–7. The pseudo-second-order model and Fourier-transform infrared spectroscopy spectra indicated that the mechanism of adsorption may be π–π electron interaction and cation–π electron bonding. Design Expert was utilized to develop a response surface methodology for the analysis and optimization of tetracycline adsorption by magnetic multi-walled carbon nanotubes. The Box–Behnken design (BBD) results showed that the optimization exhibited high significance and reliability. The main effect plots and Pareto chart indicated that pH exerted a significant individual effect on the regulation of adsorption, while 3D response surface plots and interaction effect plots exhibited a significant antagonistic interaction between pH and contact time. A maximum tetracycline removal of 99.16% was achieved under the optimal conditions of 12 mg adsorbent dosage at pH 5.43, with an adsorption time of 120 min. Mathematical and experimental results confirmed the accuracy of the established optimal conditions.
Wastewater collection systems (WCSs) not only play an indispensable role in urban life but also significantly contribute to greenhouse gas (GHG) emissions. Based on extensive literature research, ...this study (1) summarizes current research on the production mechanisms, influencing factors, control techniques, and quantitative estimates of GHGs emitted from WCSs and (2) presents initial estimates of total GHG emissions from WCSs in China. A variety of factors affect GHG production, but standard methods are still lacking to quantify GHG emissions from WCSs. China’s WCSs emit approximately 3.86–15.35 Mt of CO2eq annually (equivalent to 5.1–20.2% of the GHG emissions from wastewater treatment). Thus, GHG emissions from WCSs are significant and deserve attention. Control of GHGs in WCSs can be achieved through the application of chemical agents, while the construction of a green stormwater infrastructure can further facilitate GHG reductions. This review provides valuable insights for policymakers to consider in future policy planning related to GHG reduction and the improved operation of WCSs. Future research should focus on quantifying the impacts of various factors and accumulating field data on GHGs in various regions to facilitate the development of standardized calculation methods.
Surface charge properties of an adsorbent always play an important role for the removal of contaminants from water. A cationic surfactant hexadecyl tri-methyl ammonium bromide (CTAB) was involved ...into adsorptive removal of Orange II (ORII) by bagasse biochars to realize an in-situ modification and an enhanced adsorption capability. Adsorption capacity of biochar (BC600) improved significantly from 1.66 mg/g in the absence of CTAB to 4.42 mg/g in the presence of 2.0 mg/L CTAB. A more hydrophobic surface of bagasse biochar was favorable for the dye uptake in the presence of CTAB. Linear pseudo-second-order kinetic model fitted the kinetics data better at three pH conditions than pseudo-first-order kinetic model, whether in the presence and absence of CTAB. Both nonlinear pseudo-first-order and pseudo-second-order kinetic models were suitable to describe the experimental data. The maximal adsorption capacity in the absence of CTAB was very limited (41.4 mg/g), while the adsorption isotherm curve in the presence of CTAB was almost linear, indicating a strong adsorption capability due to the introduction of CTAB. Direct addition of CTAB into wastewater is a potential technique for the enhanced removal of negatively-charged pollutants by bagasse biochar.
•MMWCNTs were prepared using carbon nanotubes and MnFe2O4.•MMWCNTs showed extensive application foreground for magnetic separation.•The adsorption process depended on surface functional groups of ...MMWCNTs.•MMWCNTs provide an encouraging alternative in the field of environmental application.
Copper (Cu(Ⅱ)) pollution has a hazardous effect on human health. However, designing new adsorbents with prominent properties is a tremendous challenge in effectively removing Cu(Ⅱ) ions from the environment. In this study, new adsorbent—MnFe2O4/multi-wall carbon nanotubes (MMWCNTs), with excellent magnetic properties were synthesized and then systematically characterized. Introducing MnFe2O4 addressed the challenge of separating the nano-adsorbent from the liquid medium. Batch adsorption experiment results indicated that effective adsorption occurred in a relatively neutral range (pH=6–8). The adsorption behaviors were consistent with the pseudo-second-order model and the Freundlich model. The maximum adsorption capacity reached 46.41 mg/g at 308 K. The adsorption thermodynamics revealed the endothermic character of adsorption by MMWCNTs, and increasing the temperature benefitted the adsorption process. Furthermore, many surface functional groups of MMWCNTs facilitated adsorption performance. Compared with the MWCNTs before modified, the adsorbent had a nearly tenfold improvement from 3.4% to 34.8% in the removal efficiency of Cu(Ⅱ) ions. These results demonstrated that MMWCNTs are a suitable, efficient adsorbent that can be used in natural water bodies for adsorbing Cu(Ⅱ) ions.
In this paper, a triangle matching algorithm using local gravity field maps is proposed to bound the drift errors inherent in Strapdown Inertial Navigation Systems (SINS) in gravity-aided navigation. ...This triangle matching algorithm has two main stages, the first is the initial matching stage, which has a coarse phase and a fine phase to address the large unknown initial errors made by INS, and the other is the tracking matching stage, which mainly aims at tracking the matching solution with the vehicle running in real time. Simulations were carried out using data for the Bohai Sea and South China Sea areas, to assess the effects of different initial errors on the matching solutions. Finally some experiments were carried out to evaluate the proposed algorithm. The results show that the triangle matching algorithm has some compelling advantages, such as a capability to address the large unknown initial errors made by INS, and good real-time quality of matching the gravity measurements with the local gravity maps.
Microplastics have aroused widespread concern because of their adverse effects on aquatic organisms. However, the underlying toxicity mechanisms have not been examined in detail. This study ...investigated the interactions between polystyrene microplastics (PS-MPs) and the model freshwater microalgae Euglena gracilis. The results of transmission electron microscopy showed that the vacuoles of microalgae were induced after 24 h exposure to 1 mg/L PS-MPs (5 μm and 0.1 μm). Furthermore, PS-MPs significantly (p < 0.05) reduced pigment contents. Moreover, superoxide dismutase activities were significantly (p < 0.05) induced in all PS-MPs treated groups. Peroxidase activities were also significantly (p < 0.05) affected by two sizes of PS-MPs (5 μm and 0.1 μm), indicating that oxidative stress was induced after exposure to PS-MPs. At the molecular level, PS-MPs dysregulated the expression of genes involved in cellular processes, genetic information processing, organismal systems, and metabolisms. The KCS gene and the CTR1 gene may be key pathways to induce adverse effects on the E. gracilis after exposure to 5 μm PS-MPs. These findings will help to elucidate the underlying molecular mechanism of microplastics toxicity on freshwater organisms.
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•Physiological and transcriptomic responses of E. gracilis exposured PS-MPs were detected.•PS-MPs significantly inhibit the growth of E. gracilis in a dose-dependent manner.•KCS and CTR1 gene may be the key pathways to induce adverse effects on E. gracilis PS-MPs exposure.
The emerging global problems of microplastics pollution and their co-occurrence with other pollutants have presented major new challenges for environmental health and protection. This study used ...column experiments to investigate the co-transport behavior and Trojan-horse effect of colloidal microplastics (non-functional polystyrene microspheres (MS), carboxyl-modified polystyrene microspheres (CMS) and sulfonate-modified polystyrene microspheres (SMS)) and lead (Pb) in porous media. Results showed that a Trojan-horse effect occurred during the co-transport of colloidal microplastics and Pb. In the process of co-transport, colloidal microplastics and Pb mutually inhibited each other’s transport at an ionic strength of 1 mM, which may be due to Pb absorption by microplastics, resulting in the destabilization of agglomerates and a reduction in the electronegativity of microplastics. At an ionic strength of 100 mM, colloidal microplastics and Pb promoted each other’s transport, potentially due to their competition for adsorption in porous media. The functional groups present on colloidal microplastics inhibited the transport of Pb at low ionic strengths, while at high ionic strengths Pb transport was promoted. Furthermore, deposition experiments verified that quartz crystal microbalance with dissipation (QCM-D) monitoring could effectively account for and predict the transport and deposition behavior of microplastics in the presence or absence of Pb.
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•Adsorption and competition affected the transport of colloidal microplastic and Pb.•Colloidal microplastics and Pb inhibited each other’s transport at 1 mM (K+).•Colloidal microplastics and Pb promoted each other’s transport at 100 mM (K+).•Carboxyl and sulfonic groups could increase the exposure risk of microplastics.
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