Analysis of Pollution in Dianchi Lake and Consideration of Its Application in Crop Planting

AbstractAfter investigating the distribution and composition of N-cycle-related bacteria of different sites and different depth of Dianchi sediment, we analyzed the longitudinal distribution, lateral distribution of N, its transportation and transformation in Dianchi sediment, as well as the involvement of these bacteria in nitrogen cycle. Conclusion was drawn as follows, (1) Azotobateria could be effectively used as indicative strains to track the changes of Dianchi pollution because the distribution of Azotobateria can not only indicate N contamination but also P enrichment, (2) ammoniate and nitrite is mainly existed in top sediment of Dianchi Lake while other forms of nitrogen mainly in deeper sediment, (3) due to the fact that Dianchi is rich in P, together with the mutual promotion between N pollution and P pollution, the pollution of south part will worsen rapidly, (4) if the south part is also polluted badly, the pollution distribution will appear as peaking at both ends (north and south), and the pollution will definitely extend toward the middle, and finally Dianchi Lake will totally be seriously polluted. Combining with the fact that 40% of Dianchi pollution was caused by abusive use of chemical fertilizer, we put forward the idea of “changing pollutants into things of value”, which could be specified as “using the sediment as agricultural fertilizer”. Such method can solve the problem of internal pollution, and what's more, it can develop agriculture, while cut down the use of chemical fertilizer and thus reduce relative pollution source

Progress in electrolyte-free fuel cells

Solid oxide fuel cell (SOFC) represents a clean electrochemical energy conversion technology with characteristics of high conversion efficiency and low emissions. It is one of the most important new energy technologies in the future. However, the manufacture of SOFCs based on the structure of anode/electrolyte/cathode is complicated and time-consuming. Thus, the cost for the entire fabrication and technology is too high to be affordable, and challenges still hinder commercialization. Recently, a novel type of electrolyte-free fuel cell (EFFC) with single component was invented, which could be the potential candidate for the next generation of advanced fuel cells. This paper briefly introduces the EFFC, working principle, performance, and advantages with updated research progress. A number of key R&D issues about EFFCs have been addressed, and future opportunities and challenges are discussed

Impact of the COVID-19 lockdown on air pollution in an industrial city in Northeastern China

Many studies in China investigated how the lockdown following the coronavirus disease 2019 substantially affected air quality; however, few were conducted in Northeastern China. Here, the changes in six criteria air pollutants, including particulate matter (PM10 and PM2.5), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and ozone (O3), were investigated in Shenyang from January to May 2015–2020. Compared with the pre-lockdown, the mass concentrations of PM2.5, PM10, SO2, NO2, and CO during the lockdown decreased by 40.3% to 48.6%, indicating a positive impact of lockdown policies on reducing pollutant emissions. The responses of PM2.5, PM10, and CO to the lockdown measures in downtown areas were more sensitive than in the suburbs. However, the O3 concentration showed the opposite trend, attributed to the drop in NOx and particulate matters. Compared to the same period in 2015–2019, the proportion of days with good air quality increased from 63.2% to 77.2% during the lockdown and Shenyang experienced no severe pollution. Our results suggest that reducing human activities can improve air quality; however, coordinated control policies of O3, PM2.5, and NO2 are imperative.

Synthesis and Photoelectrocatalytic Applications of TiO2/ZnO/Diatomite Composites

ZnO and TiO2 are semiconductor nanomaterials that are widely used in photocatalysis. However, the relatively high recombination rate and low quantum yield of photogenerated electron–hole pairs limit their practical applications. In this study, a series of TiO2/ZnO/diatomite composites with various compositions were successfully prepared via a two-step precipitation method. They exhibited stronger UV–visible absorption properties and substantially lower fluorescence intensities than those of ZnO and ZnO/diatomite, which was mainly due to the low recombination rate of the photogenerated electron–hole pairs in the composite system. The reaction intermediates of methylene blue were detected by liquid chromatography–mass spectrometry, and the degradation process was determined. The best composite catalyst was used for the degradation of gaseous methylbenzene and gaseous acetone. The gaseous acetone degradation product was determined to be acetaldehyde via gas chromatography–mass spectrometry. The results show that the composite catalyst exhibited a good photocatalytic degradation of both liquid pollutants and harmful volatile gases. When applied to the hydrogen and oxygen evolution reactions, the composite catalyst retained a good photoresponsivity and electrolytic efficiency

Synthesis and Photoelectrocatalytic Applications of TiO₂/ZnO/Diatomite Composites

ZnO and TiO2 are semiconductor nanomaterials that are widely used in photocatalysis. However, the relatively high recombination rate and low quantum yield of photogenerated electron–hole pairs limit their practical applications. In this study, a series of TiO2/ZnO/diatomite composites with various compositions were successfully prepared via a two-step precipitation method. They exhibited stronger UV–visible absorption properties and substantially lower fluorescence intensities than those of ZnO and ZnO/diatomite, which was mainly due to the low recombination rate of the photogenerated electron–hole pairs in the composite system. The reaction intermediates of methylene blue were detected by liquid chromatography–mass spectrometry, and the degradation process was determined. The best composite catalyst was used for the degradation of gaseous methylbenzene and gaseous acetone. The gaseous acetone degradation product was determined to be acetaldehyde via gas chromatography–mass spectrometry. The results show that the composite catalyst exhibited a good photocatalytic degradation of both liquid pollutants and harmful volatile gases. When applied to the hydrogen and oxygen evolution reactions, the composite catalyst retained a good photoresponsivity and electrolytic efficiency

Numerical Analysis of Water–Sediment Flow Fields within the Intake Structure of Pumping Station under Different Hydraulic Conditions

The vortices, backflow, and siltation caused by sediment-laden flow are detrimental to the safe and efficient operation of pumping stations. To explore the effects of water–sediment two-phase flow on the velocity field, vorticity field, and sediment distribution within intake structures, field tests and numerical simulations were conducted in this study with consideration for the sediment concentration, flow rate, and start-up combination. We applied a non-contact laser scanner and ultrasonic Doppler velocimetry to obtain the field data and reverse modeling of the three-dimensional model of the intake structure under siltation. A multiphase flow model based on the Euler–Euler approach combined with the k-ε turbulence model was adopted for numerical simulation under 10 working conditions, and the reliability was verified with field data. The results indicate that sediment promotes the evolution of coaxial vortices into larger-scale spiral vortices along the water depth, and the process of sediment deposition is controlled by the range, intensity, and flow velocity of the backflow zone. Furthermore, the maximum volume fraction of the near-bottom sediment increased by 202.01% compared to the initial state. The increase in flow rate exacerbates the turbulence of the flow field. Although the increase in sediment concentration benefits the flow diffusion, it further promotes sediment deposition. This study provides a new idea for modeling complex surfaces and considers different operating conditions. It can serve as a scientific reference for the structural optimization and anti-siltation design of similar water-conservancy projects

Insecticidal Activity of 11 Bt toxins and 3 Transgenic Maize Events Expressing Vip3Aa19 to Black Cutworm, Agrotis ipsilon (Hufnagel)

Black cutworm (BCW), Agrotis ipsilon (Hufnagel), is an occasional pest of maize that can cause considerable economic loss and injury to corn seedlings. This research mainly assessed the susceptibility of BCW neonates to 11 Bt toxins (Cry1Ab, Cry1Ac, Cry1Ah, Cry1F, Cry1Ie, Cry1B, Cry2Aa, Vip3_ch1, Vip3_ch4, Vip3Ca2, Vip3Aa19) by exposing neonates to an artificial diet containing Bt toxins and evaluated the efficacy of three transgenic maize events (C008, C009, C010) expressing Vip3Aa19 toxin against BCW. The toxin-diet bioassay data indicated that Vip3Aa19 protein (LC50 = 0.43 μg/g) was the most active against BCW. Chimeric protein Vip3_ch1 (LC50 = 5.53 μg/g), Cry1F (LC50 = 83.62 μg/g) and Cry1Ac (LC50 = 184.77 μg/g) were less toxic. BCW was very tolerant to the other Bt toxins tested, with LC50 values more than 200 μg/g. Greenhouse studies were conducted with artificial infestations at the whorl stage by placing second-instar BCW larvae into whorl leaf and the fourth-instar larvae at the base of maize seedings. These results suggest that these transgenic maize events expressing Vip3Aa19 can provide effective control for BCW

Evaluation of bacterial contamination on three different surfaces within domestic refrigerators

The objectives of this study were to analyze the number of microorganisms, fungal composition and the correlation between bacterial enrichment and air quality on three internal surfaces (the inner wall, shelf, and basket) of domestic refrigerators. The results showed that the inner wall had a significantly lower number of coliforms (P < 0.05), and the range was 0.2−2.5 log MPN cm−2. The total bacterial counts and psychrophilic bacterial counts on three internal surfaces in the same refrigerator tended to be consistent. Moreover, the inner wall owned a simpler bacterial community structure. At the genus level of fungi, the dominant flora of both the inner wall and shelf were Saccharomyces spp. and Candida spp., while Saccharomyces spp., Candida spp. and Fistulina spp. took superiority in the basket. Specifically, Shannon index and Simpson index, which represent the bacterial community diversity, were the lowest on the wall, and six bacterial species on the inner wall had relative abundance higher than 0.5% of the total operational taxonomic units (OTUs), while for the shelf and basket, there were 12 and 11 bacterial species respectively. Also, there was a significant negative correlation in the basket between the chao1 index and PM2.5. This study could provide guidance for the sanitation and recommend adequate packaging of foods stored in refrigerators

Predicting the Evolution Trend of Water and Land Resource Carrying Capacity Based on CA–Markov Model in an Arid Region of Northwest China

The evolution of water and land resource carrying capacity significantly impacts optimal water and land resource allocation and regional sustainable development in arid regions. This study proposes a model that combines cellular automaton (CA) and Markov; this model aids in predicting spatial changes in water and land resource availability. In this study, taking the Jingdian Irrigation District in China’s northwest arid region as an example, we used long-series monitoring data and a Landsat dataset to create a raster-weighted fusion of 18 indicators and quantitatively analyzed the carrying status of water and land resources from 1994 to 2018. The CA–Markov model was used to simulate the carrying status of water and land resources in 2018 and to perform accuracy correction. The validated CA–Markov model was used to predict water and land resource carrying status in 2026 and 2034. The results show (1) from 1994 to 2018, the area of “good carrying” zone increased by 10.42%, the area of “safe carrying” zone increased by 7%, and spatially rose in an arc from the town to the surrounding regions. The area of “critical carrying” zone remains almost unchanged. The area of “slight carrying” zone decreased by 5.18% and the area of “severe carrying” zone decreased by 11.99%. (2) Comparing the actual and predicted carrying state of water and land resources in 2018, it was found that the simulation accuracy of “good carrying”, “safe carrying”, “critical carrying”, “slight carrying”, and “severe carrying” reached 98.71%, 92.07%, 95.34%, 94.05%, and 93.73%, respectively. This indicates that the simulation results have high reliability and applicability. (3) The future medium and long-term carrying status of water and land resources are healthy, but this trend is gradually slowing. The “slight carrying” and “severe carrying” zones show the gradual spatial transition from land desertification to soil salinization

Optimizing the Controlling Parameters of a Biomass Boiler Based on Big Data

This paper presents a comprehensive method for optimizing the controlling parameters of a biomass boiler. The historical data are preprocessed and classified into different conditions with the k-means clustering algorithm. The first-order derivative (FOD) method is used to compensate for the lag of controlling parameters, the backpropagation (BP) neural network is used to map the controlling parameters with the boiler efficiency and unit load, and the ant colony optimization (ACO) algorithm is used to search the opening of air dampers. The results of the FOD-BP-ACO model show an improvement in the boiler efficiency compared to the predicted values of FOD-BP and the data compared to the historical true values were observed. The results suggest that this FOD-BP-ACO method can also be used to search and optimize other controlling parameters