[en] The sorption species of Eu(III) on γ-Al₂O₃ and bentonite was investigated by batch, surface complexation model (SCM), and X-ray absorption spectroscopy (XAS). The results showed that sorption edges of Eu(III) on γ-Al₂O₃ and bentonite were as expected shifted forward high pH with the increasing in Eu(III) concentration, and sorption of Eu(III) was strongly dependent on pH. In γ-Al₂O₃ system, sorption of Eu(III) was decreased above pH 8.5 at low concentration of Eu(III) because of water soluble carbonate species of Eu(III), however the decline did not appear at high concentration of Eu(III) possibly due to a offset effect of surface precipitation. Actually, the sorption species of Eu(III) on bentonite mainly referred to at least four kinds of species including ion exchange (>X₃Eu⁰) at low pH, inner-sphere complexes (>AlOEu²⁺ and >SiOEu²⁺) at neutral condition, and hydrolysis species (>SiOEu(OH)₂⁰) at alkaline condition. Linear combination fitting (LCF) in k space testified that hydrolysis of Eu(OH)3(s) and oxide of Eu₂O₃ species were major for Eu(III) sorption on γ-Al₂O₃, whereas Eu³⁺(aq) and hydrolysis species comprised sorption species on bentonite. Extended X-ray absorption fine structure (EXAFS) analysis further confirmed the prediction from SCM and LCF. In addition, the typical shells of Eu-Al in R range of 3.0-3.4 A and Eu-Si at ∼4.0 A were found in radial structure functions, which was possibly identified to edge-shared bidentate of Eu(III) on Al₂O₃ and bentonite. (author)

[en] In this study, the TiO₂ nanotubes were fabricated by electrochemical anodization in a NH₄F/Na₂SO₄/PEG400/H₂O electrolyte system. Ultrasonic wave (80 W, 40 kHz) was used to clean the surface of TiO₂ nanotube arrays in the medium of water after the completion of the anodization. Surface morphology (FESEM) and X-ray diffraction spectrum of the nanotubes treated by sonication at 0 min, 9 min, 40 min and 60 min were compared. The experimental results showed that the precipitate on the surface of the nanotube arrays could be removed by the ultrasonic wave. The treating time had an influence on the precipitate removal and 9 min (corresponding to 12 Wh) is the suitable time for surface cleaning of the TiO₂ nanotubes on this experimental condition.

[en] Highlights: • Soil nutrient contents significantly increased following cropland to orchard conversion. • Conversion of cropland to orchard changed soil microbial community composition, but not diversity. • Actinobacteria tended to increase their relative abundances in responding to land-use conversion. • Belowground microbial community reflects the ecological recovery status. The ‘Grain for Green’ project (GGP) is the largest ecological rehabilitation project in China. A large body of croplands has been abandoned or converted to shrubs or grasslands since 1999. Soil microbes are recognized as sensitive responders of environmental changes, therefore, they are considered as a key component of ecological rehabilitation. However, very limited field experiments have been conducted to investigate the responses of soil microorganisms to restoration projects, especially in karst regions of China. In order to evaluate the response of soil microbial community to ecological restoration, we determined soil microbial community composition by means of qPCR, PLFAs, and high-throughput amplicon sequencing following conversion of cropland to Chinese prickly ash (Zanthoxylum bungeanum Maxim) orchard (CP) along a 20-year chronosequence in a degraded karst ecosystem. Our results showed that soil nutrient contents significantly increased following cropland to CP conversion. qPCR results showed that the highest bacterial abundance was found in the 20-year CP, but bacterial abundance decreased during the first 5-year land-use conversion. Conversion of cropland to CP strongly impacted soil microbial community composition, despite the cropland sites having a long cultivation history (>50 years). However, soil bacterial diversity remained unchanged within a 20-year land-use conversion. Actinobacteria, Proteobacteria, and Acidobacteria were the main bacterial phyla in all land-use sites. In particular, various members of Actinobacteria (e.g., Solirubrobacteraceae) tended to increase their relative abundances in responding to land-use conversion, which may imply that the shifts of soil microbial communities associated with recovering of ecological conditions. Overall, given the rapid yet differential response to ecological restoration, investigation of the belowground microbial community can provide an effective way of assessing ecological recovery of restoration projects in the karst region.

[en] As phosphorus plays a significant role in the maintenance of ecosystem service at watershed scale, it has been studied with a dramatic growth of publications. The bibliometric dataset of publications on watershed phosphorus was downloaded from the Science Citation Index Expanded from the Web of Science and visualized with cluster and network analysis to map global research status and trends. The results showed that annual output of articles experienced a notable increase since 1991. Most research articles on watershed phosphorus appeared in the Journal of Environmental Quality. “Environmental Sciences,” “Water Resources,” and “Marine Freshwater Biology” were the most popular subject categories, and a development tendency of cross-disciplinary research appeared since 2005. The USA was a leading country in total publications, collaborating closely with China, Canada, and the UK. Chinese Academy of Sciences, USDA ARS, and US Geological Survey were the most productive institutions, and Chinese Academy of Sciences has become the core force of international cooperation recently. The mainstream research related to watershed phosphorus was environmental issues like eutrophication. Moreover, phosphorus management using models (soil and water assessment tool and best management practices) has emerged as an important research direction recently. To tackle environmental issues and realize sustainable development of watershed, it is crucial to further strengthen (1) the interdisciplinary collaboration, particularly between natural and social sciences; (2) North–South, South–South, and triangular regional cooperation on science and technology; and (3) theoretical research on the impact of human activities and climate change on biogeochemical cycle of phosphorus and ecosystem integrality of watershed.

[en] Highlights: • Feasibility of stainless steel cathode in EF pretreatment of antibiotics was investigated. • 17.68 mg• L⁻¹ of H₂O₂ was generated without external O₂ aeration. • 7 intermediates were observed and 2 reasonable degradation pathways were proposed. • Acute toxicity of AMX wastewater was reduced by half. -- Abstract: In this work, a scaled-up electro-Fenton (EF) system was performed on the treatment of amoxicillin (AMX) wastewater. The effects of operational parameters on AMX degradation efficiency were investigated, such as Fe²⁺ concentration, pH, applied current (mA) and initial AMX concentration. Kinetic analysis exhibited the degradation process followed the First-order kinetic model. Box-Behnken design (BBD) was applied here to determine and analyze the optimum operating condition. Up to17.68 mg• L⁻¹ of H₂O₂ could be in situ generated in 120 min without external O₂ supply and reusability of the electrodes were analyzed. Moreover, a degradation mechanism with hydroxyl radicals (• OH) as dominant oxidant was proposed. UPLC-MS analysis was performed to identify oxidation intermediates and thus a reasonable degradation pathway of AMX was speculated. Acute toxicity assessment showed a 50% decrease in bio-toxicity of the treated effluent. The EF system provided a new insight into the effective pretreatment of antibiotic wastewater.

[en] Highlights: • Microbial-induced carbonate precipitation could effectively reduce the available Pb in soil. • Biomineralization materials could increase the stability of soil aggregates. • Biomineralization remediation materials could improve soil agglomeration and pore structure. Soil structure is an important index to evaluate soil quality; however, previous researchers have only paid attention to the effect and economic benefits of soil heavy metal remediation. In this study, microbial-induced carbonate precipitation (MICP) technology was used to remediate soil Pb pollution, and its effect on soil structure was studied by sieving and X-ray computed tomography techniques. The results showed that the leaching amount of heavy metals in soil decreased by 76.34% after remediation. Interestingly, due to the addition of organic matter and microorganisms, the soil particle size changed from microaggregates to large aggregates, and the large soil particle size (diameter > 2 mm) increased significantly by 71.43%. The soil porosity increased by 73.78%, which enhanced the soil permeability and increased the soil hydraulic conductivity. Therefore, MICP bioremediation not only remediated soil heavy metal pollution but also promoted the soil aggregation structure, which has important significance for soil remediation and improvement.

[en] Highlights: • SMT-Sb(V)-complexes formed when they coexisted in aqueous solution • Groups of NH₂, N-H, S=O, C-N of SMT complexed with Sb(V) • Complexing was enhanced and followed the order of pH 7.0 > pH 5.0 > pH 3.0. • Complexation reaction inhibited the adsorption of Sb(V) ions by the black soil. • The adsorption capacity of Sb(V) followed the order of 3.0 > pH 5.0 > pH 7.0. This paper reported when sulfamethazine (SMT) and antimony (Sb(V)) coexisted in aqueous solution at pH of 3.0, 5.0 and 7.0, the complexation between SMT and Sb(V) occurred. Such a complexation impeded the adsorption of Sb(V) on the black soil. The higher the solution pH value was, the more the amount of Sb(V) was prevented from adsorbing on the black soil. The maximum adsorption capacity (q_m) of Sb(V) at the presence of SMT under pH of 3.0, 5.0 and 7.0 was 5.28, 3.45 and 1.95 mg/g, respectively. -NH₂, NH, SO and CN of pyrimidine ring carried by SMT acted as the complexation sites with Sb(V). The complexation constant K were − 3.15, −3.26 and − 3.48 at pH of 7.0, 5.0 and 3.0, respectively, indicating that the complexation strength between SMT and Sb(V) followed the order of pH 7.0 > pH 5.0 > pH 3.0. The binding energy between Sb(V) and the CN group of pyrimidine ring was the highest (1.42 eV), and then followed by the groups of -NH (1.37 eV), SO (0.66 eV) and -NH₂ (0.39 eV). Besides SO and CN, Sb(V) tends to complex with NH via coordination bond at pH of 7.0 while -NH₂ via cation-π interaction at pH 3.0 and 5.0. Compared to pH of 5.0, the strength of cation-π interaction at pH of 3.0 weakened according to the molecular electrostatic potential map. These results demonstrated that different from the situation where Sb(V) exists in aqueous solution alone, the coexistence of SMT with Sb(V) affected the adsorption behavior of Sb(V) in soil and solution pH was also an influence factor. These findings in this paper would be helpful for further understanding the mobility, bioavailability and other environmental behavior of Sb(V) in soil when Sb(V) coexists with antibiotics even other organic compounds.

[en] Spatial variability of polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matter (PM_2.5) was investigated in Xi'an, China, in summer of 2013. Sixteen priority PAHs were quantified in 24-h integrated air samples collected simultaneously at nine urban and suburban communities. The total quantified PAHs mass concentrations ranged from 32.4 to 104.7 ng m⁻³, with an average value of 57.1 ± 23.0 ng m⁻³. PAHs were observed higher concentrations at suburban communities (average: 86.3 ng m⁻³) than at urban ones (average: 48.8 ng m⁻³) due to a better enforcement of the pollution control policies at the urban scale, and meanwhile the disorganized management of motor vehicles and massive building constructions in the suburbs. Elevated PAH levels were observed in the industrialized regions (west and northwest of Xi'an) from Kriging interpolation analysis. Satellite-based visual interpretations of land use were also applied for the supporting the spatial distribution of PAHs among the communities. The average benzo[a]pyrene-equivalent toxicity (Σ[BaP]_eq) at the nine communities was 6.9 ± 2.2 ng m⁻³ during the sampling period, showing a generally similar spatial distribution to PAHs levels. On average, the excess inhalation lifetime cancer risk derived from Σ[BaP]_eq indicated that eight persons per million of community residents would develop cancer due to PM_2.5-bound PAHs exposure in Xi'an. The great in-city spatial variability of PAHs confirmed the importance of multiple points sampling to conduct exposure health risk assessment. - Highlights: • Strict motor vehicle emission control measures can be benefited to both urban and suburban air quality. • Green city plan bearing urban capacity favors a clean atmosphere. • New air pollution purification technology and advanced management improve air quality. • Eight cancer cases per million of residents could be attributable to PM_2.5-bound PAHs exposure. - Inefficient control of vehicle is the most significant contributor to the suburban PAHs. Eight cancer cases per million of residents could be attributable to PM_2.5-bound PAHs exposure.