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1.
Phys Rev Lett ; 124(7): 070501, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-32142314

##### RESUMO

Twin-field (TF) quantum key distribution (QKD) promises high key rates over long distances to beat the rate-distance limit. Here, applying the sending-or-not-sending TF QKD protocol, we experimentally demonstrate a secure key distribution that breaks the absolute key-rate limit of repeaterless QKD over a 509-km-long ultralow loss optical fiber. Two independent lasers are used as sources with remote-frequency-locking technique over the 500-km fiber distance. Practical optical fibers are used as the optical path with appropriate noise filtering; and finite-key effects are considered in the key-rate analysis. The secure key rate obtained at 509 km is more than seven times higher than the relative bound of repeaterless QKD for the same detection loss. The achieved secure key rate is also higher than that of a traditional QKD protocol running with a perfect repeaterless QKD device, even for an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve a high secure key rate over a long distribution distance, and is therefore practically useful for field implementation of intercity QKD.

2.
Funct Plant Biol ; 47(4): 318-326, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32054564

##### RESUMO

Organic acids secreted from the roots of plants play important roles in nutrient acquisition and metal detoxification; however, the precise underlying mechanisms of these processes remain poorly understood. In the present study we examined the content of organic acids exuded from roots and the effects of these organic acids on the activation of slowly available potassium (K) at different K levels, including normal K supply and K-deficient conditions. In addition, the study system also comprised a high-K tobacco variety (ND202) and two common ones (K326 and NC89). Our results showed that high-K varieties exhibited significantly higher contents of organic acids in its root exudates and available K in both rhizosphere and non-rhizosphere soils than the other varieties. This research also suggested that a cyclic process in which soil was acidified after being complexed by organic acids was involved in the release of slowly available K, and that this process primarily depended on the soil pH at high organic acids concentrations, but the complexation of organic ligands became dominant at low concentrations. In conclusion, tobacco roots secrete organic acids to increase available K content and improve the utilisation rate of soil K. High-K varieties probably enhance slowly available K activation by secreting relatively high amounts of organic acids, thus leading to more available K in soil for absorption by plants.

3.
Nature ; 578(7794): 240-245, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32051600

##### RESUMO

A quantum internet that connects remote quantum processors1,2 should enable a number of revolutionary applications such as distributed quantum computing. Its realization will rely on entanglement of remote quantum memories over long distances. Despite enormous progress3-12, at present the maximal physical separation achieved between two nodes is 1.3 kilometres10, and challenges for longer distances remain. Here we demonstrate entanglement of two atomic ensembles in one laboratory via photon transmission through city-scale optical fibres. The atomic ensembles function as quantum memories that store quantum states. We use cavity enhancement to efficiently create atom-photon entanglement13-15 and we use quantum frequency conversion16 to shift the atomic wavelength to telecommunications wavelengths. We realize entanglement over 22 kilometres of field-deployed fibres via two-photon interference17,18 and entanglement over 50 kilometres of coiled fibres via single-photon interference19. Our experiment could be extended to nodes physically separated by similar distances, which would thus form a functional segment of the atomic quantum network, paving the way towards establishing atomic entanglement over many nodes and over much longer distances.

4.
Transl Oncol ; 13(3): 100736, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-32092670

##### RESUMO

Elderly patients with esophageal carcinoma may benefit from concurrent chemoradiotherapy (CCRT). However, the optimal concurrent chemotherapy regimen has not been determined. The aim of our study was to assess the efficiency and tolerance of treatment with a concurrent 5-fluorouracil (5-Fu)-based regimen and a taxane-based regimen combined with radiotherapy in elderly patients with esophageal squamous cell carcinoma (ESCC). A total of 46 patients with ESCC aged older than 65 years were included in this study. The patient population was divided into two treatment groups: 24 patients who received CCRT with a 5-Fu-based regimen were allocated to the PF group, and 22 patients who received CCRT with a taxane-based regimen were allocated to the DP group. The median overall survival (OS), median progression-free survival (PFS), overall response rate, and treatment-related toxicity were assessed. For patients in the PF group, the median OS time was 27.8 ± 9.1 months, and the median PFS time was 12.5 ± 2.7 months. Patients in the DP group had comparable survival outcomes, with a median OS time of 34.4 ± 6.4 months and a median PFS time of 21.1 ± 6.4 months (P = .296 and P = .115, respectively). Grade ≥3 leukocytopenia and grade ≥2 anemia occurred in 63.6% and 59.1% of patients in the DP group, respectively, and in 25.0% and 16.7% of patients in the PF group, respectively. Our results suggest that CCRT with a taxane-based regimen results in a higher incidence of treatment-related toxicity than CCRT with a 5-Fu-based regimen but comparable survival outcomes.

5.
J Stroke Cerebrovasc Dis ; 29(4): 104627, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31952979

##### RESUMO

Introduction and Case Presentation: A 44-year-old female patient suffered migraines and underwent contrast-enhanced transcranial Doppler (c-TCD). During the rapid injection of contrast agent, she suffered chest tightness, palpitation, decreased consciousness, perimouth numbness, and headache, respectively. Meanwhile, "curtain" pattern of air embolic signals lasted up to 115 seconds in her decreased right middle cerebral artery accompanied with arrhythmia. The microair embolic signals lasted as long as 340 seconds. The patient's symptoms were relieved in 30 minutes. The aforementioned symptoms and signs occurred, lasted, then disappeared coinciding in time with changes of microbubbles. The woman was later found to have ventricular septal defect. Discussion: The adverse effects to cardiac-neurovascular system of c-TCD are reported for the first time, which arouse attention to safety of the procedure.

6.
J Hazard Mater ; 386: 121930, 2020 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-31893556

##### RESUMO

In this work, sludge conditioning efficiency of cerium chloride (CeCl3) in combination with organic polymers was evaluated, the floc microstructure and extracellular polymeric substances (EPS) properties under flocculation conditioning were analyzed. The interaction mechanisms between EPS and Ce(III) were systematically investigated through two-dimension correlation spectroscopy, X-ray photoelectron spectroscopy, and confocal laser scanning microscopy. In addition, the adsorption and catalytic abilities of Ce-sludge based carbon (SBC) in tetracycline (TC) removal were evaluated. The results showed that CeCl3 conditioning performed well in improving sludge dewaterability, and CeCl3 and cationic polyacrylamide showed a synergistic effect in sludge conditioning. Contents of EPS decreased as the dosage of CeCl3 increased because of charge neutralization and complexation reactions. 2D-UV-FTIR heterospectral correlation spectroscopy analysis suggested the reaction activity of EPS to Ce(III) followed the order of humic acidâ¯>â¯proteinâ¯>â¯polysaccharide. The decrease of α-helix content improved the hydrophobicity of proteins in EPS, which was responsible for sludge dewaterability improvement in CeCl3 conditioning. Besides, the SBC was prepared with CeCl3 conditioned sludge for treating water containing TC. Ce-SBC had a dual function of adsorption and Fenton-like activity. This work provides a sludge recycling process that coupled chemical conditioning to pyrolysis carbonization to prepare functional carbon-based materials.

7.
Med Biol Eng Comput ; 58(3): 559-572, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31919719

##### RESUMO

Intraoperative fluoroscopic images, as one of the most important input data for computer-assisted orthopedic surgery (CAOS) systems, have a significant influence on the positioning accuracy of CAOS system. In this study, we proposed to use multi-angle intraoperative fluoroscopy images as input based on real clinical scenario, and the aim was to analyze the positioning accuracy and the error propagation rules with multi-angle input images compared with traditional two input images. In the experiment, the positioning accuracy of the C-arm calibration-based algorithm was studied, respectively, using two, three, four, five, and six intraoperative fluoroscopic images as input data. Moreover, the error propagation rules of the positioning error were analyzed by the Monte Carlo method. The experiment result showed that increasing the number of multi-angle input fluoroscopic images could reduce the positioning error of CAOS system, which has dropped from 1.01 to 0.61 mm. The Monte Carlo simulation analysis showed that for random input errors subject to normal distribution (µ = 0, σ = 1), the image positioning error dropped from 0.29 to 0.23 mm, and the staff gauge positioning error dropped from 1.36 to 1.19 mm, while the tracking device positioning error dropped from 3.41 to 2.13 mm. In addition, the results showed that image positioning error and staff gauge positioning error were all nonlinear error for the whole system, but tracker device positioning error was a strictly linear error. In conclusion, using multi-angle fluoroscopy images was helpful for clinic, which could improve the positioning accuracy of the CAOS system by nearly 30%. Graphical abstract The experiment process and Monte Carlo analysis of spatial positioning accuracy (A: Setup for the experiment; B: The process of Monte Carlo analysis; C: Results).

8.
Anal Chem ; 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-31984730

##### RESUMO

The total OH reactivity (kOH') is an important parameter for quantitative assessment of the atmospheric oxidation capacity. Although laboratory measurement of kOH' has been achieved 20 years ago, the instruments required are often costly and complex. Long-term atmospheric observations remain challenging and elusive. In this work, a novel instrument combining laser-flash photolysis with a mid-infrared Faraday rotation spectrometer (LFP-FRS) has been developed for the measurement of kOH' and for studying gas phase free radical kinetics. The reactor is composed of a Herriott-type optical multipass cell, and OH radicals were generated by flash photolysis of ozone with a 266 nm pulsed Nd:YAG laser. The decay of the OH signal was directly measured with a time-resolved FRS spectrometer at 2.8 µm. The overlapping path length between the pump beam and probe beam was 25 m. High performance was achieved by subtracting the signals before and after flash photolysis to eliminate interferences caused by H2O absorption and background drift. The optimum precisions (1σ) of OH concentration and kOH' measurement were 4 × 106 molecules cm-3 and 0.09 s-1 over data acquisition times of 56 and 112 s, respectively. The performance of the system was evaluated by the reaction of OH with CO and NO. The measured rate coefficients (kOH+CO and kOH+NO) were in good agreement with values reported in the literature. The developed LFP-FRS provides a new, high precision, and highly selective tool for atmospheric chemistry research of OH radicals and other transient paramagnetic free radicals such as HO2 radicals.

9.
Phys Rev Lett ; 124(1): 010502, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31976724

##### RESUMO

Ensuring the nonentanglement-breaking (non-EB) property of quantum channels is crucial for the effective distribution and storage of quantum states. However, a practical method for direct and accurate certification of the non-EB feature is highly desirable. Here, we propose and verify a realistic source based measurement device independent certification of non-EB channels. Our method is resilient to repercussions on the certification from experimental conditions, such as multiphotons and imperfect state preparation, and can be implemented with an information incomplete set. We achieve good agreement between experimental outcomes and theoretical predictions, which is validated by the expected results of the ideal semiquantum signaling game, and accurately certify the non-EB channels. Furthermore, our approach is highly robust to effects from noise. Therefore, the proposed approach can be expected to play a significant role in the design and evaluation of realistic quantum channels.

10.
FASEB J ; 34(1): 1169-1181, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31914631

##### RESUMO

BHLHE40, a member of the basic helix-loop-helix transcription factor family, has been reported to play an important role in inflammatory diseases. However, the regulation and function of BHLHE40 in Helicobacter pylori (H pylori)-associated gastritis is unknown. We observed that gastric BHLHE40 was significantly elevated in patients and mice with H pylori infection. Then, we demonstrate that H pylori-infected GECs express BHLHE40 via cagA-ERK pathway. BHLHE40 translocates to cell nucleus, and then binds to cagA protein-activated p-STAT3 (Tyr705). The complex increases chemotactic factor CXCL12 expression (production). Release of CXCL12 from GECs fosters CD4+ T cell infiltration in the gastric mucosa. Our results identify the cagA-BHLHE40-CXCL12 axis that contributes to inflammatory response in gastric mucosa during H pylori infection.

11.
Water Res ; 169: 115265, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31710914

##### RESUMO

Extracellular polymeric substances (EPS) in wastewater sludge form a network structure that is highly hydrophilic and compressible. Thus chemical conditioning is always required to improve sludge dewaterability by changing the gelatinous structure of sludge flocs. Layered double hydroxides (LDH) are generally characterized by large surface area and high anion exchange capacity, so we prepared three types of hydrotalcite-like compounds (Ca/Mg/Al-LDHs) from a typical solid waste, blast furnace slag, using NaOH precipitation (giving LDHa), a hydrothermal method (LDHb), and NaOH-Na2CO3 precipitation (LDHc). The physicochemical properties of the three LDH were comprehensively characterized, and their effectiveness as sludge conditioners was evaluated. The results showed that LDH conditioning was able to promote sludge dewaterability, and conditioning efficiency was strongly dependent on LDH structural properties. LDH neutralized the negative charges onto sludge particles and interacted with EPS to increase floc strength. LDH also formed a skeletal structure that reduced sludge compressibility. In addition, there were interactions between the LDH surfaces and the OC-OH in EPS proteins, which altered the secondary structure of protein molecules, consequently increasing sludge dewaterability. The biomolecules of low-molecular-weight fractions (such as peptides and humic acids) in soluble EPS intercalated LDH. Both the surface complexation of organic matter containing carboxyl groups and the intercalation of small molecules in soluble EPS were responsible for EPS-LDH interactions. The combination of skeleton formation, electrostatic interaction, and EPS-LDH interactions resulted in compression of gel-like structure and improved sludge dewatering performance. We finally suggested a novel sludge treatment process that increases sludge dewaterability using slag-derived Ca/Mg/Al-LDH to condition the sludge, and it could be combined with pyrolysis to prepare multi-functional materials or bio-oil.

##### Assuntos
Esgotos , Águas Residuárias , Hidróxido de Alumínio , Filtração , Hidróxido de Magnésio , Minerais , Eliminação de Resíduos Líquidos , Água
12.
Chemosphere ; 243: 125333, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31734596

##### RESUMO

Pyrolysis carbonisation is a promising technology to convert organic waste into valuable carbon-based materials. However, sludge is generally highly compressible and difficult to dewater because of its high concentrations of biopolymers; the bound water of sludge is trapped in a network composed of biopolymers. Therefore, chemical conditioning is an indispensable step for improving sludge dewaterability performance. In the present work, the effects of different chemical conditioning agents (polymeric aluminium chloride (PACl), iron(III) chloride (FeCl3), KMnO4-Fe(II) and Fenton's reagent) on the physicochemical properties of sludge-based carbons (SBCs) were systematically studied and the SBCs were further used in advanced wastewater treatment. The adsorption mechanisms of dissolved organic matters (DOMs) by different SBCs were also investigated. The results showed that conditioning with KMnO4-Fe(II) and Fenton's reagent improved the specific surface area of the SBCs, whereas inorganic salt flocculation conditioning reduced the porosity of the SBCs. In addition, we found that the Fenton-SBC and Mn/Fe-SBC performed better than the other investigated SBCs in the removal of organic compounds from secondary effluent and that the pseudo-second-order kinetic model could better describe the process of DOMs adsorption by all of the investigated SBCs. Moreover, three-dimensional fluorescence excitation-emission matrix spectroscopy in combination with an analysis of the physical and chemical fractionation of DOMs showed that all of the SBCs performed well in the adsorption of aromatic substances, hydrophobic acids and hydrophobic neutrals, whereas the Mn/Fe-SBC and Fenton-SBC performed better than the other SBCs in the removal of weakly hydrophobic acids.

13.
Appl Opt ; 58(32): 8743-8750, 2019 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-31873651

##### RESUMO

We report the development of an improved spherical mirror multipass-cell-based interband cascade laser (ICL) spectrometer for ambient formaldehyde (HCHO) detection. The multipass cell consists of two easily manufactured spherical mirrors that are low cost, and have a simple structure, large mirror area utilization, and dense spot pattern. Optical interference caused by the multipath cell was largely reduced, resulting in good sensitivity. Using wavelength modulation spectroscopy (WMS), a detection precision (${1} \sigma$1σ) of 51 pptv in 10 s was achieved with an absorption pathlength of 96 m, which compared favorably with the performance of other state-of-the-art instruments. The precision can be further improved by using a long absorption pathlength configuration and by removing fringe-like optical noise caused by the collimation lens. Ambient application of the developed spectrometer was demonstrated.

14.
Appl Opt ; 58(30): 8148-8152, 2019 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-31674484

##### RESUMO

In this work, we report a large-active-area multispectral superconducting nanowire single-photon detector for free-space applications. The detector is realized by fabricating NbTiN nanowire with an active area of 35 µm diameter on two serially connected dielectric mirrors that can simultaneously and efficiently detect single photons at the three typical wavelengths employed in free-space applications, namely, 532, 850, and 1064 nm. Maximal system detection efficiencies (SDEs) of 80.0% at 532 nm and 850 nm and 75.8% at 1064 nm are achieved for polarized light obtained by coupling the detector with an SMF-28 fiber. Upon coupling with a 50 µm multimode fiber, SDEs of 68.6%, 59.6%, and 47.0%, are achieved for 532, 850, and 1064 nm wavelength unpolarized light, respectively. Moreover, the detector shows timing jitters of 37.1 and 41.0 ps when coupled with SMF-28 fiber and 50 µm multimode fiber. This type of detector with a large active area and multiwavelength detection capability is promising for both single and multiwavelength free-space applications.

15.
Phys Rev Lett ; 123(10): 100503, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31573287

##### RESUMO

Quantum computing has seen tremendous progress in past years. Due to implementation complexity and cost, the future path of quantum computation is strongly believed to delegate computational tasks to powerful quantum servers on the cloud. Universal blind quantum computing (UBQC) provides the protocol for the secure delegation of arbitrary quantum computations, and it has received significant attention. However, a great challenge in UBQC is how to transmit a quantum state over a long distance securely and reliably. Here, we solve this challenge by proposing a resource-efficient remote blind qubit preparation (RBQP) protocol, with weak coherent pulses for the client to produce, using a compact and low-cost laser. We experimentally verify a key step of RBQP-quantum nondemolition measurement-in the field test over 100 km of fiber. Our experiment uses a quantum teleportation setup in the telecom wavelength and generates 1000 secure qubits with an average fidelity of (86.9±1.5)%, which exceeds the quantum no-cloning fidelity of equatorial qubit states. The results prove the feasibility of UBQC over long distances, and thus serves as a key milestone towards secure cloud quantum computing.

16.
Phys Rev Lett ; 123(10): 100505, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31573314

##### RESUMO

Channel loss seems to be the most severe limitation on the practical application of long distance quantum key distribution. The idea of twin-field quantum key distribution can improve the key rate from the linear scale of channel loss in the traditional decoy-state method to the square root scale of the channel transmittance. However, the technical demands are rather tough because they require single photon level interference of two remote independent lasers. Here, we adopt the technology developed in the frequency and time transfer to lock two independent laser wavelengths and utilize additional phase reference light to estimate and compensate the fiber fluctuation. Further, with a single photon detector with a high detection rate, we demonstrate twin field quantum key distribution through the sending-or-not-sending protocol with a realistic phase drift over 300 km optical fiber spools. We calculate the secure key rates with the finite size effect. The secure key rate at 300 km (1.96×10^{-6}) is higher than that of the repeaterless secret key capacity (8.64×10^{-7}).

17.
BMC Public Health ; 19(1): 1269, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31533693

##### RESUMO

BACKGROUND: Several studies have demonstrated that smoke-free legislation is associated with a reduced risk of mortality from acute myocardial infarction (AMI). This study aimed to examine and quantify the potential effect of smoke-free legislation on AMI mortality rate in different countries. METHODS: Studies were identified using a systematic search of the scientific literature from electronic databases, including PubMed, Web of Science, ScienceDirect, Embase, Google Scholar, and China National Knowledge Infrastructure (CNKI), from their inception through September 30, 2017. A random effects model was employed to estimate the overall effects of smoke-free legislation on the AMI mortality rate. Subgroup analysis was performed to explore the possible causes of heterogeneity in risk estimates based on sex and age. The results of meta-analysis after excluding the studies with a high risk of bias were reported in this study. RESULTS: A total of 10 eligible studies with 16 estimates of effect size were included in this meta-analysis. Significant heterogeneity in the risk estimates was identified (overall I2 = 94.6%, p < 0.001). Therefore, a random effects model was utilized to estimate the overall effect of smoke-free legislation. There was an 8% decline in AMI mortality after introducing smoke-free legislation (RR = 0.92, 95% confidence interval (CI): 0.90-0.94). The results of subgroup analyses showed that smoke-free legislation was significantly associated with lower rates of mortality for the following 5 diagnostic subgroups: smoke-free in workplaces, restaurants and bars (RR = 0.92, 95% CI: 0.90-0.95), smaller sample size (RR = 0.92, 95% CI: 0.89-0.95), study location in Europe (RR = 0.90, 95% CI: 0.85-0.94), regional study area (RR = 0.92, 95% CI: 0.89-0.94), and no previous local smoke-free legislation (RR = 0.91, 95% CI: 0.90-0.93). However, there was not much difference in AMI mortality rates after the legislation between the longer (RR = 0.92, 95% CI: 0.86-0.98) and shorter follow-up duration subgroups (RR = 0.92, 95% CI: 0.89-0.94). CONCLUSION: Smoke-free legislation could significantly reduce the AMI mortality rate by 8%. The reduction in the AMI mortality rate was more significant in studies with more comprehensive laws, without prior smoke-free bans, with a smaller sample size, at the regional level, and with a location in Europe.

##### Assuntos
Infarto do Miocárdio/mortalidade , Logradouros Públicos/legislação & jurisprudência , Saúde Pública/legislação & jurisprudência , Política Antifumo/legislação & jurisprudência , Fumar/legislação & jurisprudência , China , Feminino , Humanos , Masculino , Infarto do Miocárdio/prevenção & controle , Restaurantes/legislação & jurisprudência , Fatores de Tempo , Local de Trabalho/legislação & jurisprudência
18.
Opt Express ; 27(18): 25241-25250, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31510399

##### RESUMO

Broadband photon detectors are a key enabling technology for various applications such as spectrometers, light detection and ranging. In this work, we report on an ultra-broadband single-photon detector based on a microfiber (MF)-coupled superconducting nanowires structure operating in the spectral range from visible to near-infrared light. The MF-coupled superconducting nanowire single-photon detector (SNSPD) is formed by placing an MF on top of superconducting niobium nitride (NbN) nanowires, allowing ultra-broadband photon detection due to their nearly lossless transmission/absorption and nearly unity internal efficiency for ultra-broad waveband. The simulation results indicate that with optimal device structure, the optical absorption with efficiency > 90% can be realized over a wavelength range of 350 nm to 2150 nm. The fabricated MF-coupled SNSPD shows unparalleled broadband system detection efficiencies (SDEs) of more than 50% from 630 nm to 1500 nm. The SDEs reach 66% at 785 nm and 45% at 1550 nm. These results pave the way for ultra-broadband weak light detection with quantum-limit sensitivity.

19.
Ecol Evol ; 9(16): 9376-9384, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31463028

##### RESUMO

Allochthonous (e.g., riparian) plant litter is among the organic matter resources that are important for wetland ecosystems. A compact canopy of free-floating vegetation on the water surface may allow for riparian litter to remain on it for a period of time before sinking to the bottom. Thus, we hypothesized that canopy of free-floating vegetation may slow decomposition processes in wetlands. To test the hypothesis that the retention of riparian leaf litter on the free-floating vegetation in wetlands affects their subsequent decomposition on the bottom of wetlands, a 50-day in situ decomposition experiment was performed in a wetland pond in subtropical China, in which litter bags of single species with fine (0.5 mm) or coarse (2.0 mm) mesh sizes were placed on free-floating vegetation (dominated by Eichhornia crassipes, Lemna minor, and Salvinia molesta) for 25 days and then moved to the pond bottom for another 25 days or remained on the pond bottom for 50 days. The leaf litter was collected from three riparian species, that is, Cinnamomum camphora, Diospyros kaki, and Phyllostachys propinqua. The retention of riparian leaf litter on free-floating vegetation had significant negative effect on the carbon loss, marginal negative effects on the mass loss, and no effect on the nitrogen loss from leaf litter, partially supporting the hypothesis. Similarly, the mass and carbon losses from leaf litter decomposing on the pond bottom for the first 25 days of the experiment were greater than those from the litter decomposing on free-floating vegetation. Our results highlight that in wetlands, free-floating vegetation could play a vital role in litter decomposition, which is linked to the regulation of nutrient cycling in ecosystems.

20.
J Air Waste Manag Assoc ; 69(11): 1368-1376, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31204897

##### RESUMO

Malodor is becoming the main secondary pollution in the municipal sewage sludge-composting process. Ammonia and volatile sulfide compounds (VSCs) are the representative odorants that generated and emitted during the composting process. The emission characteristics of ammonia and VSCs were studied at different workshops in a full-scale municipal sludge-composting plant in North People's Republic of China. Results show that ammonia was the most dominant odorant of all the workshops and relative high concentrations of VSCs were detected at sludge stacking yard and composting workshop. The odor pattern of VSCs at the composting workshop and stacking yard were different. The odor pollution occurred mainly in the first 15 days of the composting process, in which the odor contribution of ammonia increased with time and the VSCs contributed largely in the first 5 days. The cumulative release concentration of VSCs from compost materials was in the order of DMDS (dimethyl disulfide) > DMS (dimethyl sulfide) > CS2 > MT (methyl mercaptan), and the total VSCs release concentration was in the range of 50-3200 µg·m-3. The production of ammonia correlated to the temperature and nitrogen content and state changes, however, the production of VSCs was more complicated due to the reaction and transformation of VSCs. Optimization of aerobic composting conditions and process parameters should be further studied to reduce the emission of odor gas from compost. Implications: Along with the widespread use of sludge aerobic composting in People's Republic of China, the malodor pollution during the composting treatment is becoming a serious environmental issue. The odor pollution occurred mainly in the first 15 days, and ammonia was the main odorant of all the workshops and need to be controlled. Relative high concentrations of VSCs were detected at sludge stacking yard and composting workshop, however, the odor impact of VSCs were different. The generation of VSCs is more complicated than ammonia due to the reaction and transformation of VSCs.