Evaluation of different factors on metal leaching from nickel tailings using generalized additive model (GAM).

Compared with sulfide tailings, the oxidation and transformation of certain substances in oxidized tailings into more soluble forms may affect the bioaccumulation and biomagnification properties and enhance the risk of toxic effects in the ecosystem. This study aimed to apply the generalized additive model (GAM) to evaluate factors affecting heavy metal leaching from nickel (Ni) tailings. We created an orthogonal experiment table (L18(37)) to evenly distribute the different combinations of factor values. The Ni tailings were immersed in solutions with different combinations of factor values for 16 d, and samples were taken on days 1, 2, 4, 7, 11, and 16 to measure the pH and heavy metal concentration of the leachate. The GAM was used to fit the concentration of heavy metals of the leachate and the initial factors of the leaching solution. The results showed that the pH and Cr concentration of the leachate increased with time and stabilized after 1 d (pH of approximately 7), while the Mn, Ni, and Tl concentrations gradually decreased and stabilized after peaking on the first day. An analysis of the GAM results showed that the Cr concentration was highly sensitive to the solid-liquid ratio (F = 127.8) and tailing particle size (F = 10.7). The Cr concentration of the leachate was significantly higher when exposed to a high solid-liquid ratio or a fine particle size, whereas the Mn, Ni, and Tl concentrations were highly sensitive to the KCl concentration and solid-liquid ratio (F = 77.4, 146.9, and 315.9 respectively). The GAM identified interactions between key factors, which have complex and strong effects on the leaching of tailings and the migration of heavy metals, either promotional or antagonistic. The prediction of the minimum Cr leaching concentration shows that GAM can be used to determine the conditions associated with minimum leaching concentrations of heavy metals and to effectively predict the metal concentrations of leachate. As such, the results of this study can be applied to the management of nickel tailings.

Performances of simultaneous enhanced removal of nitrogen and phosphorus via biological aerated filter with biochar as fillers under low dissolved oxygen for digested swine wastewater treatment.

This study aims to explore the feasibility of biochar as a carrier to improve the simultaneous removal of nitrogen and phosphorus in biological aerated filters (BAFs) for treating low C/N digested swine wastewater (DSW). Two similar BAFs (BAF-A with hydrophobic polypropylene resin as fillers and BAF-B with bamboo biochar as carrier) were developed for DSW treatment. Results showed that the NH4+-N, TN, and TP removal performances in BAF-B were higher than those in BAF-A. Carrier type had an obvious influence on the structures and diversity of the microbial population. The biochar carrier in BAF-B was conducive to the enrichment of the functional microorganisms and the increase of microbial diversity under high NH4+-N conditions. Microbial analysis showed that the genera Rhodanobacter (10.64%), JGI_0001001-h003 (14.24%), RBG-13-54-9 (8.87%), Chujaibacter (11.27%), and Ottowia were the predominant populations involved in nitrogen and phosphorus removal in the later stage of phase III in BAF-B. BAF with biochar as carrier was highly promising for TN and TP removal in low C/N and high NH4+-N DSW treatment.

Effects of epidural anesthesia and analgesia on the incidence of chronic pain after thoracoscopic lung surgery: A retrospective cohort study.

Objective: Chronic postoperative pain (CPSP) is common after thoracic surgery, even after the less invasive video-assisted thoracoscopic surgery (VATS). This study investigated the effect of thoracic epidural anesthesia (TEA) on the development of CPSP. Materials: We retrospectively analyzed the data of patients who underwent VATS at our center between 2020 and 2022. The enrolled patients were divided into the epidural block (EPI) and patient-controlled intravenous analgesia (PCIA) groups. A telephone questionnaire was used to collect information regarding CPSP, which was defined as a numerical rating scale (VAS) score ≥1 at 3 or 6 months postoperatively. Additionally, statistical analyses were performed to identify the risk factors for CPSP in the two groups. Results: Overall, 894 patients completed the follow-up interviews at 3 and 6 months, with 325 and 569 patients in the PCIA and EPI groups, respectively. The incidence rates of CPSP in the PCIA group at 3 and 6 months were 16.9 % (95 % confidence interval [CI]: 9.3-32.7 %) and 13.5 % (95 % CI: 8.7-33.4 %), and 10.3 % (95 % CI: 8.1-30.5 %) and 3.6 % (95 % CI: 3.5-21.5 %) in EPI group, respectively. The incidence of CPSP at 3 months (P = 0.0048) and 6 months (P < 0.005) was statistically significant in both groups. Age and lymph node dissection were significantly associated with CPSP. Conclusions: Compared to PCIA, TEA was associated with a lower incidence of CPSP after VATS, and should be considered an important part of the analgesia regimen for patients with VATS.

Evolution of chemical composition of fogwater in winter in Chengdu, China.

Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11-C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Sigma15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5-C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

Black carbon pollution in China from 2001 to 2019: Patterns, trends, and drivers.

Based on a near real-time 10 km × 10 km resolution black carbon (BC) concentration dataset, this study investigated the spatial patterns, trend variations, and drivers of BC concentrations in China from 2001 to 2019 with spatial analysis, trend analysis, hotspot clustering, and multiscale geographically weighted regression (MGWR). The results indicate that Beijing-Tianjin-Hebei, the Chengdu-Chongqing agglomeration, Pearl River Delta, and East China Plain were the hotspot centers of BC concentration in China. From 2001 to 2019, the average rate of decline in BC concentrations across China was 0.36 µg/m3/year (p < 0.001), with BC concentrations peaking around 2006 and sustaining a decline for the next decade or so. The rate of BC decline was higher in Central, North, and East China than in other regions. The MGWR model revealed the spatial heterogeneity of the influences of different drivers. A number of enterprises had significant effects on BC in East, North, and Southwest China; coal production had strong effects on BC in Southwest and East China; electricity consumption had better effects on BC in Northeast, Northwest, and East China than in other regions; the ratio of secondary industries had the greatest effects on BC in North and Southwest China; and CO2 emissions had the strongest effects on BC in East and North China. Meanwhile, the reduction of BC emissions from the industrial sector was the dominant factor in the decrease of BC concentration in China. These findings provide references and policy prescriptions for how cities in different regions can reduce BC emissions.

[Spatiotemporal Distribution Characteristics of Air Pollution and Health Risks in Key Cities of China].

Based on the monitoring data of five pollutants in 168 key cities under air pollution prevention and control in China from 2015 to 2020, using the MAKESENS model and the aggregate risk index(ARI), this study quantitatively analyzed the spatial and temporal distribution characteristics of air pollution and health risks in China and the six urban agglomerations. The results showed that:① PM2.5 pollution was the most serious pollution in Chinese key cities. Only 15% of the cities' six-year average concentrations of PM2.5 reached the National Secondary Standard, followed by that of NO2; 77% of the cities' six-year average concentrations of NO2 reached the National Secondary Standard. The urban agglomerations of Beijing-Tianjin-Hebei and Fenwei plain had the most serious air pollution, and the six-year average concentrations of PM2.5, SO2, CO, and NO2 were higher than those of other urban agglomerations. ② The concentrations of PM2.5, SO2, CO, and NO2 in key cities of China showed a decreasing trend, whereas the concentration of O3 in other urban agglomerations showed an increasing trend, except in the Chengdu-Chongqing urban agglomeration. The concentration of SO2 in the urban agglomerations of Beijing-Tianjin-Hebei and Fenwei plain changed the most significantly. ③ The health risk of air pollution in the key cities of China generally showed a decreasing trend, with a sharp decline from 2017 to 2018, and the population exposed to extremely high risks dropped from 160 million to 32.54 million. The urban agglomeration in the middle reaches of the Yangtze River had the most significant decline in health risks, whereas the key cities in China faced higher health risks in spring and winter seasons. ④ The Beijing-Tianjin-Hebei and Fenwei plain urban agglomerations had the highest health risks, and the urban agglomeration in the middle reaches of the Yangtze River had the lowest; O3 gradually replaced PM2.5 as the main pollutant affecting the health risk. These results can provide a reference for evaluating the effectiveness of urban air pollution control in China during the 13th Five-Year Plan period.

Analysis of the meteorological factors affecting the short-term increase in O3 concentrations in nine global cities during COVID-19.

Surface ozone (O3) is a major air pollutant around the world. This study investigated O3 concentrations in nine cities during the Coronavirus disease 2019 (COVID-19) lockdown phases. A statistical model, named Generalized Additive Model (GAM), was also developed to assess different meteorological factors, estimate daily O3 release during COVID-19 lockdown and determine the relationship between the two. We found that: (1) Daily O3 significantly increased in all selected cities during the COVID-19 lockdown, presenting relative increases from -5.7% (in São Paulo) to 58.9% (in Guangzhou), with respect to the average value for the same period in the previous five years. (2) In the GAM model, the adjusted coefficient of determination (R2) ranged from 0.48 (Sao Paulo) to 0.84 (Rome), and it captured 51-85% of daily O3 variations. (3) Analyzing the expected O3 concentrations during the lockdown, using GAM fed by meteorological data, showed that O3 anomalies were dominantly controlled by meteorology. (4) The relevance of different meteorological variables depended on the cities. The positive O3 anomalies in Beijing, Wuhan, Guangzhou, and Delhi were mostly associated with low relative humidity and elevated maximum temperature. Low wind speed, elevated maximum temperature, and low relative humidity were the leading meteorological factors for O3 anomalies in London, Paris, and Rome. The two other cities had different leading factor combinations.

Progress on two-dimensional binary oxide materials.

Two-dimensional van der Waals (2D vdW) materials have attracted much attention because of their unique electronic and optical properties. Since the successful isolation of graphene in 2004, many interesting 2D materials have emerged, including elemental olefins (silicene, germanene, etc.), transition metal chalcogenides, transition metal carbides (nitrides), hexagonal boron, etc. On the other hand, 2D binary oxide materials are an important group in the 2D family owing to their high structural diversity, low cost, high stability, and strong adjustability. This review systematically summarizes the research progress on 2D binary oxide materials. We discuss their composition and structure in terms of vdW and non-vdW categories in detail, followed by a discussion of their synthesis methods. In particular, we focus on strategies to tailor the properties of 2D oxides and their emerging applications in different fields. Finally, the challenges and future developments of 2D binary oxides are provided.

Spatio-Temporal Heterogeneity of the Relationships Between PM2.5 and Its Determinants: A Case Study of Chinese Cities in Winter of 2020.

Fine particulate matter (PM2.5) poses threat to human health in China, particularly in winter. The pandemic of coronavirus disease 2019 (COVID-19) led to a series of strict control measures in Chinese cities, resulting in a short-term significant improvement in air quality. This is a perfect case to explore driving factors affecting the PM2.5 distributions in Chinese cities, thus helping form better policies for future PM2.5 mitigation. Based on panel data of 332 cities, we analyzed the function of natural and anthropogenic factors to PM2.5 pollution by applying the geographically and temporally weighted regression (GTWR) model. We found that the PM2.5 concentration of 84.3% of cities decreased after lockdown. Spatially, in the winter of 2020, cities with high PM2.5 concentrations were mainly distributed in Northeast China, the North China Plain and the Tarim Basin. Higher temperature, wind speed and relative humidity were easier to promote haze pollution in northwest of the country, where enhanced surface pressure decreased PM2.5 concentrations. Furthermore, the intensity of trip activities (ITAs) had a significant positive effect on PM2.5 pollution in Northwest and Central China. The number of daily pollutant operating vents of key polluting enterprises in the industrial sector (VOI) in northern cities was positively correlated with the PM2.5 concentration; inversely, the number of daily pollutant operating vents of key polluting enterprises in the power sector (VOP) imposed a negative effect on the PM2.5 concentration in these regions. This work provides some implications for regional air quality improvement policies of Chinese cities in wintertime.

Marked Efficiency Improvement of FAPb0.7Sn0.3Br3 Perovskite Light-Emitting Diodes by Optimization of the Light-Emitting Layer and Hole-Transport Layer.

Highly luminescent FAPb0.7Sn0.3Br3 nanocrystals with an average photoluminescence (PL) quantum yield of 92% were synthesized by the ligand-assisted reprecipitation method. The 41-nm-thick perovskite film with a smooth surface and strong PL intensity was proven to be a suitable luminescent layer for perovskite light-emitting diodes (PeLEDs). Electrical tests indicate that the double hole-transport layers (HTLs) played an important role in improving the electrical-to-optical conversion efficiency of PeLEDs due to their cascade-like level alignment. The PeLED based on poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,40-(N-(p-butylphenyl))-diphenylamine)] (TFB)/poly(9-vinylcarbazole) (PVK) double HTLs produced a high external quantum efficiency (EQE) of 9%, which was improved by approximately 10.9 and 5.14 times when compared with single HTL PVK or the TFB device, respectively. The enhancement of the hole transmission capacity by TFB/PVK double HTLs was confirmed by the hole-only device and was responsible for the dramatic EQE improvement.

Human exposure to PBDEs via house dust ingestion in Guangzhou, South China.

Numerous studies have demonstrated the important role played by indoor dust in human exposure to polybrominated diphenyl ethers (PBDEs), particularly in children, who spend most of their time indoors. Few data have been available for PBDEs in house dust in China. In this study, dust samples were collected randomly from 46 houses in Guangzhou, South China, for the first time to investigate levels and pattern profiles of PBDEs and to estimate human exposure to PBDEs for adults and toddlers (6 months to 2 years old). Using gas chromatography-mass spectrometry in selected ion monitoring mode, congeners--including BDE28, 47, 66, 85, 99, 100, 153, 154, 183, and 209--were determined. The results show that BDE209 is the predominant congener in house dust, comprising 90.7% to 99.8% (mean 97.4%) of the total concentration. Of ∑tri-hepta BDEs, BDE47, 99, and 183 were the most abundant congeners, with mean contributions of 23.3%, 25.2%, and 21.9%, respectively. The intake of ∑tri-hepta BDEs via dust ingestion was 0.16-3.82 ng/d for adults and 2.1-7.64 ng/d for toddlers, accounting for 0.65% to 13.6% and 18.6% to 45.5%, respectively, of the total (based on data in our previous work) (Chen et al. 2008). With respect to intake of BDE209, the values increased to 11 to 264 ng/d for adults and to 145 to 527 ng/d for toddlers. Risk assessment indicated that PBDEs may possibly affect the health of toddlers in Guangzhou, South China. Further studies are needed to investigate the bioavailability and metabolism of PBDEs in humans to improve risk evaluation.

Magnon Torque Transferred into a Magnetic Insulator through an Antiferromagnetic Insulator.

Electrical spin-orbit torque (SOT) in magnetic insulators (MI) has been intensively studied due to its advantages in spin-orbitronic devices with ultralow energy consumption. However, the magnon torque in the MIs, which has the potential to further lower the energy consumption, still remains elusive. In this work, we demonstrate the efficient magnon torque transferred into an MI through an antiferromagnetic insulator. By fabricating a Pt/NiO/Tm3Fe5O12 heterostructure with different NiO thicknesses, we have systematically investigated the evolution of the transferred magnon torque. We show that the magnon torque efficiency transferred through the NiO into the MI can retain a high value (∼50%), which is comparable to the previous report for the magnon torque transferred into the metallic magnet. Our study manifests the feasibility of realizing the pure magnon-based spin-orbitronic devices with ultralow energy consumption and high efficiency.

[Spatial Variation of Surface Ozone Concentration During the Warm Season and Its Meteorological Driving Factors in China].

The concentration of surface ozone (O3) in China increased consistently from 2015 to 2018, and became an important air pollutant, followed by particulate matter. This study uses real-time O3 and meteorological data, obtained in 337 cities in China during the warm seasons (April to September) of 2015 to 2018, to determine the spatial variation of surface O3 and its meteorological driving factors in major cities in China, via trend analysis, spatial autocorrelation, hotspot analysis, and multi-scale geographically weighted regression (MGWR) modeling. The results show that: ① during the warm season, O3 concentrations showed a significant growth trend (P<0.05), with an average growth rate of 0.28 µg·(m3·a)-1, while more than 55% of urban O3 concentrations increased by 0.50 µg·m-3 annually. ② There were significant regional differences in O3 concentration. High values (>60 µg·m-3) were distributed over east China, north China, central China, and northwest China, while low values (<20 µg·m-3) were distributed over south China and southwest China. ③ The spatial agglomeration of O3 concentration has been enhanced year by year, with hotspots mainly distributed over east China and central China. In contrast, there are cold spots in northeast China, southwest China, and southern China. ④Analysis of the MGWR model indicated that temperature, wind speed, cloud coverage, and precipitation all have a significant effect on the distribution of O3, although there are also discrepancies in driving factor priorities between the different regions. Temperature was the main meteorological driving factor of O3 variation during the warm season in China, and its impact on O3 concentration was significantly higher in north China, northwest China, and northeast China than in other regions; overall, there was a significant positive correlation between O3 concentration and temperature, except in Guangxi, Yunnan, and Jiangxi. O3 concentration was negatively correlated with wind speed in most regions of south China, east China, and central China, and positively correlated with wind speed in north China and northeast China. O3 concentration was significantly negatively correlated with cloud cover, except in Liaoning, Shandong, Hebei, Gansu, Guangdong, and some areas in southwest China. O3 concentration was significantly negatively correlated with precipitation, except in the northwest and southwest regions.

A facile synthesis of nanostructured CoFe2O4 for the electrochemical sensing of bisphenol A.

This work reports a novel, highly sensitive and cost-effective electrochemical sensor for the detection of bisphenol A in environmental water samples. Attractive non-noble transition metal oxide CoFe2O4 nanoparticles were successfully synthesized using a sol-gel combustion method and further characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. Under optimal conditions, the CoFe2O4 nanoparticle modified glassy carbon electrode exhibits high electrochemical activity and good catalytic performance for the detection of bisphenol A. The linear calibration curves are obtained within a wide concentration range from 0.05 µmol L-1 to 10 µmol L-1, and the limit of detection is 3.6 nmol L-1 for bisphenol A. Moreover, this sensor also demonstrates excellent reproducibility, stability, and good anti-interference ability. The sensor was successfully applied to determine bisphenol A in practical samples, and the satisfactory recovery rate was between 95.5% and 102.0%. Based on the great electrochemical properties and practical application results, this electrochemical sensor has broad application prospects in the sensing of bisphenol A.

Enhancement of alkaline water splitting activity by Co-P coating on a copper oxide nanowire.

Hydrogen is the most attractive source of energy in the 21st century. However, high-efficiency mass production of hydrogen still faces many challenges. Although electrochemical water splitting is an ideal way to produce hydrogen, it requires low-cost and efficient electrocatalysts. In this work, a hybrid shell/core Co-P/CuO nanowire array was fabricated by Co-P film electrodeposition on a CuO nanowire array. Because of the synergy between Co-P and CuO nanowire arrays, Co-P/CuO shows remarkable activity toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). This bifunctional electrocatalyst achieving 20 mA cm-2 requires a cell voltage of only 1.645 V, and has superb long-term electrochemical stability and high faradaic efficiency.

[Pollution Characteristics and Exposure Risk Assessment of Perfluoroalkyl Substances in Road Dust, Chengdu].

To study the pollution characteristics and exposure health risk of perfluoroalkyl substances (PFASs) in road dust, 12 PFASs were analyzed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) in this study. PFAS concentrations in road dust ranged from 0.95 to 111 ng·g-1, with an average concentration of (25.6±37.2) ng·g-1, suggesting large spatial differences between PFASs in road dust. PFAS concentrations on the main roads were significantly higher than on minor roads, and the minor roads downtown displayed higher concentration levels than suburban minor roads. Perfluorobutanoic acid (PFBA) was the predominant compound in Section 1 of Jie-fang Road, Jin-niu-ba Road and Shui-nian-he Road, while perfluroroocantanoic acid (PFOA, 24.8%) and perfluorooctane sulfonate (PFOS, 24.1%) were the main PFASs on other roads, indicating different sources of PFASs in these areas. The total daily dose of PFASs in road dust for children and adults were 0.168 ng·(kg·d)-1 and 0.028 ng·(kg·d)-1, respectively, suggesting higher exposure risk for children than adults. Therefore, more attention should be paid to children's health risk assessment. Daily doses of PFOA and PFOS in road dust for Chengdu residents were lower than the maximum daily intakes recommended by the European Authority, indicating that there was no immediate health risk to local residents.

Spatiotemporal distribution and isomer profiles of perfluoroalkyl acids in airborne particulate matter in Chengdu City, China.

Airborne particulate matter (APM) was collected in four seasons at five different areas of the city of Chengdu, China to study the spatial and seasonal contamination pattern of perfluoroalkyl acids (PFAAs). The results showed that ∑PFAA concentrations in Downtown Chengdu (mean value: 297 ±â€¯238 pg/m3) were higher than concentrations in suburban areas. The highest concentrations of PFAAs occurred during spring (97.5-709 pg/L; arithmetic mean concentration: 297 ±â€¯191 pg/L) while the lowest concentration occurred during autumn (9.27-105 pg/L; arithmetic mean concentration 41.1 ±â€¯24.8 pg/L). Perfluorooctanoic acid (PFOA) was the main PFAA quantified during winter, summer and autumn, and perfluorononanoic acid (PFNA) was the predominant PFAA in spring. Relative humidity (RH) and average daily precipitation (PRE) showed significant negative correlations with PFAA concentrations in winter and summer, suggesting that they played an important role in controlling PFAA concentrations in APM. The linear structural isomer of PFOA (n-PFOA) was the most abundant isomer in APM in Chengdu, with the average proportion of 85.6% ±â€¯6.13%, higher than the proportion in ECF PFOA commercial products (74.3-77.6%). However, the consistent fingerprint of branched PFOA in the APM implies that ECF PFOA makes a significant contribution to the PFOA in APM. PFOS in the APM collected throughout the year had a mean proportion of 54.0 ±â€¯8.81% of n-PFOS. This proportion of n-PFOS is lower than commercial ECF products (62.9-78.2%), suggesting an additional proportion of branched PFOS isomers in APM in Chengdu.

A self-supported amorphous Ni-P alloy on a CuO nanowire array: an efficient 3D electrode catalyst for water splitting in alkaline media.

Energy-efficient electrochemical water splitting is one important way to produce hydrogen fuel but still faces many challenges. In this communication, we report that an amorphous Ni-P alloy shell electrodeposited on a CuO nanowire array supported on copper foam (CuO@Ni-P NA/CF) can be used for efficient water splitting in alkaline media. As a 3D catalytic electrode, it exhibits excellent activity both for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) with overpotentials of 106 mV for HER and 275 mV for OER to achieve a current density of 30 mA cm-2 in 1.0 M KOH. This bifunctional electrode enables a high-performance alkaline water electrolyzer to achieve a current density of 30 mA cm-2 at a cell voltage of 1.71 V.

Threshold and multiple indicators for nitrogen saturation in subtropical forests.

The influence of nitrogen (N) deposition on forest ecosystems largely depend on the N status. Developing threshold and practical indicators for N saturation in subtropical forests, with extremely high N deposition, would both enhance forest management and the assessments of global N balance and carbon (C) sequestration. Here, we quantified the N mass balance and assessed current N status at a number of subtropical forest sites in South China, using both N content, C/N ratio, and 15N natural abundance (δ15N) as potential indicators of N saturation. Among the studied sites, N deposition ranged from 13.8 to 113 kg N ha-1 yr-1 in throughfall, and was dominated by ammonium (NH4+). The threshold for N leaching in subtropical forest was first found to be 26-36 kg N ha-1 yr-1, which was 160% higher than in temperate forest (based on prescribed minimum). This indicates that critical parameter inputs in global models of the impact of N deposition are in need of revision, based on specific ecosystem characteristics. We found a critical C/N ratio of 20 for the O/A horizon as indicator of N saturation. Foliar N content and δ15N were positively correlated with N deposition and were well suited to indicate regional N status. The δ15N enrichment factor (Ɛfoli/So2, δ15Nfoliage - δ15NSoil2) was between -10‰ and -1‰, and had similar trend to those obtained from other regions with increasing N deposition. These suggest that the enrichment factor could be used to investigate the influence of N deposition in forest ecosystems, regardless of spatial heterogeneity in δ15N of N input, soil N availability and geomorphology.

New Insights into CO2 Adsorption on Layered Double Hydroxide (LDH)-Based Nanomaterials.

The interlamellar spacing of layered double hydroxides (LDHs) was enlarged by dodecyl sulfonate ions firstly, and then, (3-aminopropyl)triethoxysilane (APS) was chemically grafted (APS/LDHs). The structural characteristics and thermal stability of these prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), reflectance Fourier transform infrared spectrometer (FTIR), thermogravimetric analysis (TG), and elemental analysis (EA) respectively. The CO2 adsorption performance was investigated adopting TG and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results presented that the CO2 adsorption capacity on APS/LDHs was as high as 90 mg/g and showed no obvious reduction during a five cyclic adsorption-desorption test, indicating its superior performance stability. The DRIFTS results showed that both carbamates and weakly bounded CO2 species were generated on APS/LDHs. The weakly adsorbed species was due to the different local chemical environment for CO2 capture provided by the surface moieties of LDHs like free silanol and hydrogen bonds.