Performance of TiB2 Wettable Cathode Coating

A TiB2 wettable cathode coating was deposited on a graphite carbon cathode material via atmospheric plasma spraying (APS). The microstructure and phase composition of the TiB2 coating were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The wettability and corrosion resistance of the coating were studied in a molten-aluminum electrolytic system. The results showed that the surface of the TiB2 coating prepared via plasma spraying was flat and that the main phase of the coating was TiB2. The wettability between the TiB2 coating and liquid aluminum was better than that between graphite cathode carbon block and liquid aluminum. The abilities of the TiB2 coating and graphite cathode carbon block to resist sodium (Na) penetration and prevent molten salt corrosion were compared through a corrosion test. The TiB2 coating was found to have better resistance to Na penetration and better refractory cryolite corrosion resistance than graphite cathode carbon block

Performance of TiB₂ Wettable Cathode Coating

A TiB2 wettable cathode coating was deposited on a graphite carbon cathode material via atmospheric plasma spraying (APS). The microstructure and phase composition of the TiB2 coating were analyzed via scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The wettability and corrosion resistance of the coating were studied in a molten-aluminum electrolytic system. The results showed that the surface of the TiB2 coating prepared via plasma spraying was flat and that the main phase of the coating was TiB2. The wettability between the TiB2 coating and liquid aluminum was better than that between graphite cathode carbon block and liquid aluminum. The abilities of the TiB2 coating and graphite cathode carbon block to resist sodium (Na) penetration and prevent molten salt corrosion were compared through a corrosion test. The TiB2 coating was found to have better resistance to Na penetration and better refractory cryolite corrosion resistance than graphite cathode carbon block

Estimating High Resolution Daily Air Temperature Based on Remote Sensing Products and Climate Reanalysis Datasets over Glacierized Basins: A Case Study in the Langtang Valley, Nepal

Near surface air temperature (Ta) is one of the key input parameters in land surface models and hydrological models as it affects most biogeophysical and biogeochemical processes of the earth surface system. For distributed hydrological modeling over glacierized basins, obtaining high resolution Ta forcing is one of the major challenges. In this study, we proposed a new high resolution daily Ta estimation scheme under both clear and cloudy sky conditions through integrating the moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (LST) and China Meteorological Administration (CMA) land data assimilation system (CLDAS) reanalyzed daily Ta. Spatio-temporal continuous MODIS LST was reconstructed through the data interpolating empirical orthogonal functions (DINEOF) method. Multi-variable regression models were developed at CLDAS scale and then used to estimate Ta at MODIS scale. The new Ta estimation scheme was tested over the Langtang Valley, Nepal as a demonstrating case study. Observations from two automatic weather stations at Kyanging and Yala located in the Langtang Valley from 2012 to 2014 were used to validate the accuracy of Ta estimation. The RMSEs are 2.05, 1.88, and 3.63 K, and the biases are 0.42, −0.68 and −2.86 K for daily maximum, mean and minimum Ta, respectively, at the Kyanging station. At the Yala station, the RMSE values are 4.53, 2.68 and 2.36 K, and biases are 4.03, 1.96 and −0.35 K for the estimated daily maximum, mean and minimum Ta, respectively. Moreover, the proposed scheme can produce reasonable spatial distribution pattern of Ta at the Langtang Valley. Our results show the proposed Ta estimation scheme is promising for integration with distributed hydrological model for glacier melting simulation over glacierized basins

Antithetical effects of nitrogen and water availability on community similarity of semiarid grasslands: evidence from a nine-year manipulation experiment

Theoretical and observational studies have suggested that environmental variations would change compositional similarity between plant communities. However, this topic has rarely been examined via experiments involving direct manipulation of resources utilized by plant communities. A 9-year field manipulation experiment was conducted to examine the effects of nitrogen addition and increased water on community similarity between a steppe and an old field in the semiarid region of northern China. Over the experimental period, nitrogen addition reduced community similarity between the steppe and the old field, whereas water addition enhanced community similarity. These treatment effects were closely related to changes in diversity characteristics as well as abundance of functional groups and dominant species of plant communities. These results highlight the importance of resource availability in regulating the trajectory of ecosystem succession, and suggest that the increase in atmospheric nitrogen deposition in northern China will contribute to divergence between the steppe and the old field, whereas the increase in growing-season precipitation may encourage convergence between the two grasslands with respect to species composition during succession. Thus the decrease in community similarity caused by nitrogen enrichment may be counteracted, at least partially, by precipitation increase under changing atmosphere and climate

Frequency and intensity of nitrogen addition alter soil inorganic sulfur fractions, but the effects vary with mowing management in a temperate steppe

Sulfur (S) availability plays a vital role in driving functions of terrestrial ecosystems, which can be largely affected by soil inorganic S fractions and pool size. Enhanced nitrogen (N) input can significantly affect soil S availability, but it still remains largely unknown if the N effect varies with frequency of N addition and mowing management in grasslands. To investigate changes in the soil S pool and inorganic S fractions (soluble S, adsorbed S, available S, and insoluble S), we conducted a field experiment with different frequencies (two times per year vs. monthly additions per year) and intensities (i.e., 0, 1, 2, 3, 5, 10, 15, 20, and 50 g N m(-2) yr(-1)) of NH4NO3 addition and mowing (unmown vs. mown) over 6 years in a temperate grassland of northern China. Generally, N addition frequency, N intensity, and mowing significantly interacted with each other to affect most of the inorganic S fractions. Specifically, a significant increase in soluble S was only found at high N frequency with the increasing intensity of N addition. Increasing N addition intensity enhanced adsorbed S and available S concentrations at low N frequency in unmown plots; however, both fractions were significantly increased with N intensity at both N frequencies in mown plots. The high frequency of N addition increased the concentrations of adsorbed S and available S in comparison to the low frequency of N addition only in mown plots. Changes in soil S fractions were mainly related to soil pH, N availability, soil organic carbon (SOC), and plant S uptake. Our results suggested that N input could temporarily replenish soil-available S by promoting dissolution of soil-insoluble S with decreasing soil pH and mineralization of organic S due to increasing plant S uptake. However, the significant decrease in organic S and total S concentrations with N addition intensity in mown plots indicated that N addition together with biomass removal would eventually cause soil S depletion in this temperate grassland in the long term. Our results further indicated that using large and infrequent N additions to simulate N deposition can overestimate the main effects of N deposition and mowing management on soil S availability in semiarid grasslands

Flow-Through Electrochemical Activation of Persulfate for Efficient Wastewater Treatment using Ti₄O₇ Reactive Electrochemical Membranes

Herein, a flow-through reactive electrochemical membrane (REM) system was reported for the complete activation of S2O82– upon a single-pass through the Ti4O7 REM cathode with less than 10 s of residence time. The kinetic constant for S2O82– activation was observed at 21–109 × 10–5 m s–1, which is 1–2 orders of magnitude higher than the reported conventional batch/flow-by electrochemical systems even with the addition of activators. The Ti4O7 REM electrode exhibited good stability in activating S2O82–, and the efficiency decreased by only ∼5% after 5 h of continuous operation due to scaling in a wastewater treatment plant (WWTP) effluent sample. As a proof-of-concept, the REM–persulfate system, i.e., integration of both anodic electrooxidation and cathodic persulfate-based advanced oxidation process, was successfully applied to treat both antibiotics-spiked WWTP effluent and reverse osmosis (RO) concentrate of pretreated coking wastewater. A single-pass of the REM–persulfate system achieved over 95% removal of 6 antibiotics (each 10 μg L–1) from WWTP effluents. As compared with the REM system without persulfate, the addition of 10 mM S2O82– for treating RO concentrate of pretreated coking wastewater resulted in a significant increase in total organic carbon removal from 51.5 to 78.9%. However, it also resulted in the formation of chlorinated byproducts, including ClO3–, ClO4–, and absorbable organic chlorine. Techno-economic analysis with an RO concentrate of pretreated coking wastewater showed that the REM–persulfate system featured a 50% lower initial capital cost than the REM system without persulfate. Results of this study indicate the REM–persulfate system may be potentially a promising wastewater treatment technology

Intensity and frequency of nitrogen addition alter soil chemical properties depending on mowing management in a temperate steppe

Anthropogenic nitrogen (N) enrichment can significantly alter soil chemical properties in various ecosystems. Previous manipulative N experiments mainly focused on the intensity of N addition on soil properties by changing N input rates. It remains unclear, however, whether frequency of N addition can affect soil chemical properties. We examined the effects of frequency (2 versus 12 applications yr(-1)) and rate (ranging from 0 to 50 g N m(-2) yr(-1)) of N addition on soil chemical properties of pH, base cations, soil pH buffering capacity (pHBC), and soil available micronutrients in a temperate steppe with and without mowing. Mowing significantly increased the effective cation exchange capacity (ECEC), soil exchangeable Ca and Na, available Fe, and soil pHBC when N was applied at low frequency. Low frequency of N addition significantly decreased soil pH and exchangeable Na but increased soil exchangeable Mg without mowing; however, it increased soil exchangeable Na and available Zn with mowing, while available Fe and Mn increased both with and without mowing. Higher rates of N addition (>= 20 g N m(-2) yr(-1)) decreased soil pH, ECEC and exchangeable Ca but increased soil available Fe, Mn and Cu regardless of the mowing treatment and frequency of N addition. Changes in soil organic matter, pHBC and ECEC were the main reasons affecting soil pH across mowing and N application treatments. Our results indicate that frequency of N addition played an essential role in altering soil chemical properties. Simulating N deposition via large and infrequent N additions can underestimate (exchangeable Mg and available Fe and Mn) or overestimate (soil pH and exchangeable Na) changes in soil properties. Our results further suggest that the effects of frequency of N addition on soil chemical attributes in semi-arid grassland ecosystems can be regulated by appropriate mowing management

Experimentally increased water and nitrogen affect root production and vertical allocation of an old-field grassland

Background and aims Evidence for impacts of environmental changes on belowground net primary production (BNPP) from long-term experiments is rather scarce. We aimed to understand how long-term changes in water and nitrogen availability affect production and vertical allocation of roots in semi-arid grasslands and its consequence on carbon (C) and nitrogen (N) cycles. Methods We investigated changes of BNPP and its vertical allocation along the soil profile to 40 cm in depth in response to simultaneous increases in water and N availability over 11 years in an old-field grassland in northern China. Results Water addition increased BNPP in all soil layers (0-10 cm, 10-20 cm, and 20-40 cm), and enhanced the percentage BNPP in the upper soils but decreased that in 10-20 cm soil layer. Nitrogen addition decreased BNPP in 10-20 cm and 20-40 cm soil layers as well as total BNPP in 0-40 cm, and increased the percentage BNPP in the upper soil layer but decreased that in 10-20 cm soil layer. Water addition increased soil total C and N concentrations in 0-10 cm and 10-20 cm soil layers, while N addition only marginally decreased soil C:N ratio in 0-10 cm and 20-40 cm soil layers. Both soil total N concentration and soil C: N ratio were closely related to BNPP. Conclusions Our results highlight the importance of environmental factors, especially water availability, in determining BNPP, and in turn controlling soil nutrient accumulation in semi-arid grasslands, although the specific mechanisms remain unclear. The projected increase in precipitation in those semi-arid grasslands would enhance soil C and N sequestration. The increased allocation of BNPP in upper soils with long-term precipitation increment and N deposition may accelerate thecycles of C and N in these ecosystems, and thus increase the risk of soil C and N loss