[Meta-analysis on the Effects of Nitrogen Addition on Soil Organic Carbon Content in Terrestrial Ecosystems].

Several studies have demonstrated that the increased deposition of nitrogen(N) has significantly affected the content of soil organic carbon(SOC); however, the change significantly varies in different regions. In this study, Meta-analysis, Meta-regression, and linear regression were performed to systematically evaluate the effects of climate, soil properties, and field design factors on the responses of SOC to N addition based on 408 data points from 49 field experiments in China. The results revealed that the response of SOC to N addition was significantly positively correlated with the mean annual temperature(MAT) and mean annual precipitation(MAP) of the sample sites(P<0.05). In the regions with lower MAT(<3℃) or MAP(<500 mm), SOC significantly decreased after N addition. In the areas with higher MAT(>3℃) or MAP(>500 mm); however, SOC significantly increased. For soil properties, SOC significantly accumulated after N addition in the plots with a higher soil C:N ratio(>15) or acidic soil(pH<6.5) but less changed in the plots with a lower C:N ratio(≤ 15) or higher pH(≥ 6.5). For ecotype, after N addition, SOC decreased significantly in the grassland ecosystem(-5.34%) but less changed in the wetland ecosystem. SOC accumulated the most after N addition in the forest ecosystem(10.52%), particularly in the broad-leaved forest ecosystem(13.10%). Further analysis showed that the soil C:N ratio was the most important factor. For type of N application, the addition of ammonium nitrate or urea increased the SOC content significantly, but the effect of nitrate was not significant. In summary, when accurately evaluating, predicting, and analyzing the effects of N addition on SOC content, the effects of climatic characteristics and soil properties of sample sites and field design factors should be comprehensively considered.

Meta-analysis on the effects of nitrogen deposition on soil N2O flux in different habitats.

We carried out a meta-analysis to explore the effects of site characteristics (climatic factors and soil properties) and nitrogen (N) factors on soil nitrous oxide (N2O) flux after N addition based on 290 data from 66 field N addition experiments in China. The results showed that mean annual precipitation, mean annual temperature, ambient N deposition rate, and soil C/N of sites were positively correlated with the increases of N2O flux after N addition. Soil pH was negatively correlated with the increases of N2O flux after N addition. Furthermore, soils in wetland ecosystem were most sensitive to N addition, followed by forest ecosystem, and grassland showed the lowest sensitivity. Among all the site characteristics, soil pH and C/N were the most important factors driving the responses of N2O flux to N addition. Soil N2O flux increased the greatest after nitrate addition. The increase of N2O flux was similar after the addition of urea and ammonium, while N2O flux increased the least when ammonium nitrate was added. In summary, to accurately assess and predict the response of soil N2O flux to N deposition, the effects of site characteristics and N fertilizer types should be comprehensively considered.

Facile synthesis of CoOOH@MXene to activate peroxymonosulfate for efficient degradation of sulfamethoxazole: performance and mechanism investigation.

Using MXene as substrate, CoOOH@MXene with different mass content of CoOOH were prepared and used to active peroxymonosulfate (PMS) for the sulfamethoxazole (SMX) degradation. The sample characterizations demonstrated the successful preparation of CoOOH@MXene. CoOOH@MXene possessed much higher BET surface area (183.82 m2/g) than CoOOH (85.36 m2/g) and MXene (6.89 m2/g) due to the good dispersibility of CoOOH particles on MXene. Due to its large surface area, 1.3CoOOH@MXene displayed the best catalytic performance for the degradation of SMX. With 0.2 g/L of 1.3CoOOH@MXene and 0.5 mM of PMS, 20 µM of SMX was completely eliminated in 10 min. The degradation followed pseudo-first-order kinetic model well, with rate constants of 0.33 min-1 for 1.3CoOOH@MXene and 0.054 min-1 for CoOOH. Influencing factors of initial pH, catalyst dosage, PMS concentration, SMX concentration, and co-existing anions on SMX degradation were assessed systematically. Recycling tests verified the excellent reusability and stability of the catalyst. Quenching experiments and electron paramagnetic resonance analysis substantiated that 1O2 played a leading role. Moreover, the intermediates were identified, and degradation pathways and activation mechanism of CoOOH@MXene for PMS were proposed. This work may highlight the application of MXene with transition metals in PMS activation.

Fabrication of magnetic nickel incorporated carbon nanofibers for superfast adsorption of sulfadiazine: Performance and mechanisms exploration.

Herein, novel magnetic nickel incorporated carbon nanofibers (Ni@CNF) were successfully synthesized via electrostatic spinning method for sulfadiazine (SDZ) adsorption. We combined computational and experimental tools to clarify the distinct nature of SDZ on Ni@CNF. Extensive computations and characterizations of SDZ-Ni adsorption complexes evidenced that Ni atoms were indispensable for SDZ adsorption and increasing the number of Ni atoms in Ni@CNF significantly improved SDZ adsorption due to the lower adsorption energy (Ead). As we surmised, the adsorption capacity of Ni@CNF enhanced gradually with increasing the mass ratio of Ni in the composite. The as-prepared 9%Ni@CNF achieved removal efficiency of 98.9% for SDZ (2.5 mg/L) in 25 min, while the pure CNF hardly removed any SDZ under the identical conditions. The experimental data was better fitted by the Langmuir model with the maximum monolayer adsorption capacity of 103.21 mg/g at 318 K. Besides, the 9%Ni@CNF exhibited great applicability to various organic contaminants, and excellent stability and reusability over five consecutive cycles. Overall, for the first time, we provide the evidence that Ni atoms in the Ni@CNF plays a crucial role in SDZ adsorption, which can guide us for constructing nickle incorporated adsorbents with impressive adsorption capacity in environmental remediation.

ZIF-8 assisted synthesis of magnetic core-shell Fe3O4@CuS nanoparticles for efficient sulfadiazine degradation via H2O2 activation: Performance and mechanism.

A novel magnetic core-shell Fe3O4@CuS have been successfully synthesized by chemical etching and cation exchange method using Zeolitic imidazolate frameworks (ZIF) as the template. The morphology and microstructural properties characterization indicated that Fe3O4@CuS nanoparticles were rhombic dodecahedral shape, highly stable, and magnetic with a large specific surface area (772.20 m2/g). The catalytic activity of Fe3O4@CuS was assessed on sulfadiazine (SDZ) degradation by H2O2 activation. Multi-factors affecting the SDZ removal was adequately investigated. Approximately 93.2% SDZ (50 µM) was removed with 0.2 g/L Fe3O4@CuS and 5 mM H2O2 in 90 min. In particular, Fe3O4@CuS exhibited a quality catalytic performance within a wide pH range of 3.0-11.0. Radical scavenger tests and electron paramagnetic resonance (EPR) analysis confirmed that •O2-, •OH, and 1O2 all contributed to the SDZ degradation, and •OH played the dominant role. Meanwhile, mechanism investigation suggested that the effective catalytic activity of Fe3O4@CuS could be ascribed to the sulphur-enhanced copper-based Fenton reaction on the CuS shell, sulphur-enhanced iron-based Fenton reaction on the Fe3O4 core, and the effective electron transfer between the shell and core. Finally, the possible SDZ degradation pathways were further proposed on the basis of the intermediates identification. This work put forward a new strategy to synthesize magnetic core-shell Fe3O4@CuS using ZIF-8 as the template with outstanding performance for H2O2 activation to degrade SDZ.

Characterization of air plasma-activated carbon nanotube electrodes for the removal of lead ion.

Carbon nanotube electrodes were prepared by pressing a mixture of carbon nanotubes and polytetrafluoroethylene (which acted as a binder) on a stainless steel net collector, and the electrodes were subsequently activated in our self-designed plasma apparatus, using air plasma. The morphology and surface functional groups of the electrodes were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. The results showed that the electrodes activated by air plasma possessed a rougher surface and more oxygen-containing groups than the raw electrodes, properties that were beneficial for their electrosorption performance. After 5 min of air plasma activation, the lead ion electrosorption capacity of the activated electrodes (measured at 450 mV) increased to 3.40 mg/g, which was 73% higher than the capacity of the non-activated, raw electrode, and 5.76 times the adsorption capacity of the raw electrode at 0 mV. The results of this study indicate that air plasma activation can be used to effectively enhance the electrosorption capacity of carbon nanotube electrodes.

[Combination of subradical external radiation and brachytherapy plus radical operation in the treatment of carcinoma of uterine cervix].

OBJECTIVE: To summarize retrospectively the 5-year survival rates and long-term complication of stage Ib-IIIa cervical carcinoma treated by combination of subradical external radiation and brachytherapy plus radical operation. METHODS: 106 patients with cervical carcinoma were all treated by radical hysterectomy and pelvic lymphadenectomy, of whom 78 had had preoperative radiotherapy (external radiation and brachytherapy), 16 combination of brachytherapy and radical operation, 12 adjuvant postoperative radiotherapy (external radiation and brachytherapy). (60)Co was used for external radiation, in which the point B dose was 25 - 30 Gy in preoperative radiation and 40 - 50 Gy in postoperative radiation. (192)Ir high-dose-rate afterloading unit was used in brachytherapy, with a dose of 6 - 18 Gy at point A. RESULTS: The follow up rate was 95.3%. The overall 5-year survival rates were 78.2% (61/78) in the preoperative radiotherapy group, 68.8% (11/16) in brachytherapy plus radical operation, 33.3% (4/12) in the postoperative radiotherapy group, showing a higher 5-year survival rate in the preoperative radiotherapy group than the postoperative radiotherapy group (P < 0.05). In stage II patients, the preoperative radiotherapy group -77.6% (45/58) also gave a higher survival than the postoperative radiotherapy group -25.0% (1/4) (P < 0.05). But all the other groups gave differences of insignificance. The chief long-term complications were radio-proctitis and cystitis, with incidences of 34.6% (27/78), 31.3% (5/16), 33.3% (4/12) in the preoperative radiotherapy group, brachytherapy plus radical operation group and the postoperative radiotherapy group (P > 0.05). CONCLUSION: The overall 5-year survival rate of combined subradical external radiation and brachytherapy plus radical operation was obviously higher than that of postoperative radiotherapy for stage Ib-IIIa and II patients, with statistically significant differences. However, the incidence of long-term complications give no statistical significance in the preoperative radiotherapy group or brachytherapy plus the operation group as compared with the postoperative radiotherapy group.