bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation of Efficient Metal-Binding Bacteria from Boreal Peat Soils and Development of Microbial Biosorbents for Improved Nickel Scavenging
Authors: Virpiranta Hanna , Banasik Michal , Taskila Sanna , Leiviskä Tiina , Halttu Maiju , Sotaniemi Ville-Hermanni , Tanskanen Juha
Published: July 2020

Boreal peatlands with low iron availability are a potential, but rarely studied, source for the isolation of bacteria for applications in metal sorption. The present research focused on the isolation and identification of Actinobacteria from northern Finland, which can produce siderophores for metal capture. The 16S rDNA analysis showed that isolated strains belonged to Firmicutes (Bacillus sp.) and Actinobacteria (Microbacterium sp.). The culture most efficiently producing siderophores in the widest array of the media was identified as Microbacterium sp. The most appropriate media for siderophore production by the Microbacterium strain were those prepared with glucose supplemented with asparagine or glutamic acid, and those prepared with glycerol or fructose supplemented with glutamic acid. The microorganism obtained and its siderophores were used to develop Sphagnum moss-based hybrid biosorbents. It was showed that the hybrid sorbent could bind nickel ions and that the nickel removal was enhanced by the presence of siderophores. Bacterial cells did not have a significant effect on sorption efficiency compared to the use of siderophores alone. The microbial biosorbent could be applied in the final effluent treatment stage for wastewater with low metal concentrations.
The Role of Nanofluids and Renewable Energy in the Development of Sustainable Desalination Systems: A Review
Authors: Singh Tejvir , Atieh Muataz Ali , Al-Ansari Tareq , Mohammad Abdul Wahab , McKay Gordon
Published: July 2020

Desalination accounts for 1% of the total global water consumption and is an energy-intensive process, with the majority of operational expenses attributed to energy consumption. Moreover, at present, a significant portion of the power comes from traditional fossil-fuel-fired power plants and the greenhouse gas emissions associated with power production along with concentrated brine discharge from the process, pose a severe threat to the environment. Due to the dramatic impact of climate change, there is a major opportunity to develop sustainable desalination processes to combat the issues of brine discharge, greenhouse gas emissions along with a reduction in energy consumption per unit of freshwater produced. Nanotechnology can play a vital role to achieve specific energy consumption reduction as nanofluids application increases the overall heat transfer coefficient enabling the production of more water for the same size desalination plant. Furthermore, concentrated brine discharge harms the marine ecosystems, and hence, this problem must also be solved to support the objective of sustainable desalination. Several studies have been carried out in the past several years in the field of nanotechnology applications for desalination, brine treatment and the role of renewable energy in desalination. This paper aims to review the major advances in this field of nanotechnology for desalination. Furthermore, a hypothesis for developing an integrated solar thermal and nanofluid sustainable desalination system, based on the cyclic economy model, is proposed.
Simulation of Soil Water Evaporation during Freeze–Thaw Periods under Different Straw Mulch Thickness Conditions
Authors: Chen Junfeng , Wei Yizhao , Zhao Xiping , Xue Jing , Xu Shuyuan , Du Qi
Published: July 2020

Straw mulching is an effective agricultural technology to reduce soil water loss in arid and semi-arid areas. Herein, the soil temperature and soil water content of bare land (LD) and 5 cm (JG5), 10 cm (JG10), 15 cm (JG15), 20 cm (JG20) and 30 cm (JG30) straw mulch thicknesses were measured through field experiments performed to assess the soil water evaporation using the simultaneous heat and water model during a freeze–thaw period. The results showed that the inhibiting effect of straw mulching on soil water evaporation during the freeze-thaw period reached 24–56.7%, and straw mulch reduced the range of daily soil water evaporation by 2.02–2.48 mm, the effects of random factors on the daily soil water evaporation were significantly decreased. The highest soil water evaporation rate occurs during the unstable freezing stage, and the lowest occurs during the stable freezing stage. When the straw mulch thickness exceeded 10 cm, the effect of increasing straw mulch thickness on daily soil water evaporation was reduced. The straw mulch layer could not completely inhibit the effect of the external environment on soil water evaporation even when the straw mulch thickness was increased to 30 cm. This research results can provide a basis for the scientific evaluation and prevention of soil water evaporation in arid and semi-arid areas.
Hydropower Potential in the Alps under Climate Change Scenarios. The Chavonne Plant, Val D’Aosta
Authors: Duratorre Tommaso , Bombelli Giovanni , Menduni Giovanni , Bocchiola Daniele
Published: July 2020

Present and prospective climate change will likely affect the hydrological cycle in sensitive areas, such as the Alps, thus impacting water-based activities. A most representative example is hydropower production, i.e., exploitation of water to produce energy. In the Italian Alps hydropower is strictly dependent upon water from snow and ice melt, and both are decreasing in response to global warming. Here, we study the effects of potential climate change scenarios at 2100 upon hydropower production from the Chavonne plant, in Valle d’Aosta region of Italy, a run-of-the-river (ROR) plant taking water from two high altitude glacierized catchments of Val di Cogne, and Valsavarenche. We use Poli-Hydro, a state-of-the-art hydrological model to mimic the hydrological budget of the area, including ice and snow melt share. Projections of the hydrological budget were built until 2100 by means of selected climate change scenarios, under proper downscaling. We used runs of three General Circulation Models (GCMs), EC-Earth, CCSM4, and ECHAM6.0 under three Representative Concentration Pathways RCP 2.6, RCP 4.5, and RCP 8.5 from AR5 of IPCC, and of their updated version under four Shared Socio-Economic Pathways SSP1 2.6, SSP2 4.5, SSP3 7.0, and SSP5 8.5 from AR6. We then assessed hydropower production changes against a recent control run CR period (2005–2015). Mean annual flow is estimated at 14.33 m3 s−1 during CR, with ice melt contribution ca. 2%, and snow melt contribution ca. 44%. Ice cover in 2005 was estimated as 19.2 km2, reaching in 2015, 9.93 km2. Mean hydropower production was estimated at 153.72 GWh during the CR. Temperature would largely increase throughout the century (+0.93 °C on average at the half century, +2.45 °C at the end of the century). The ice covered area would be largely depleted (ca. −86%, −94% respectively), with reduced contribution of ice melt (0.23%, <0.1%, respectively) and snow melt (ca. 37%, 33%, respectively). Precipitation would show uncertain patterns, and hence incoming discharge at the plant would erratically vary (−29% to +24% half century, −27% to +59% end of century). Hydropower production displays a large dependence upon monthly discharge patterns, with mostly positive variations (+2.90% on average at half century, +6.95% on average at end of century), with its change driven by exceedance of plant’s capacity.
Selective Inhibition on Growth and Photosynthesis of Harmful Cyanobacteria (Microcystis aeruginosa) by Water Soluble Substances of Dendranthema indicum Flowers
Authors: Gao Yunni , Zhang Fang , Wu Jing , Yang Hui , Dong Jing , Zhang Man , Li Xuejun
Published: July 2020

Harmful cyanobacterial blooms become serious environmental issues in various waterbodies, including aquaculture ponds, which inherently need a high biomass and healthy composition of phytoplankton to sustain their high productivity. Indoor bioassays were conducted to investigate the effects of an aqueous extract of Dendranthema indicum flowers on cyanobacteria and green algae species. The thermal stability and polarity of the water-soluble active substances of D. indicum flowers were also assessed based on the growth and photosynthesis responses of Microcystis aeruginosa. There was obvious growth promotion of green algae, including Chlorella vulgaris, Kirchneriella sp. and Haematococcus pluvialis and strong growth inhibition of toxigenic and non-toxigenic M. aeruginosa by aqueous extracts of D. indicum flowers at concentrations ranging from 0.5 to 2.0 g·DW·L−1. The cell concentrations of M. aeruginosa and C. vulgaris were 46.5% and 242.2% of those in the corresponding controls after a 10-day exposure to aqueous extracts of D. indicum flowers at 1.0 g·DW·L−1. There must be some water-soluble active allelochemicals released from D. indicum flowers that are responsible for the selective inhibition of M. aeruginosa rather than green algae. The inhibition ratio of the growth and photosynthesis of M. aeruginosa by aqueous extracts of D. indicum flowers at 2.0 g·DW·L−1 prepared with water at 25 °C and 100 °C were above 90% and 80% compared to the cell density and performance index on absorption basis (PIABS) value of M. aeruginosa in the control on day 6, without significant differences. It indicates that the active substances of D. indicum flowers were thermally stable. The methanol fraction eluted from solid phase extraction (SPE)-enriched aqueous extracts of D. indicum flowers showed the strongest inhibition of the growth and photosynthesis of M. aeruginosa compared to the other four fractions. It indicates that the most polar substances of D. indicum flowers were responsible for the selective inhibition of M. aeruginosa. More experiments are required to identify the responsible active substances and reveal the underlying mechanisms of aqueous extracts of D. indicum flowers that selectively inhibit cyanobacteria and regulate the phytoplankton community structure.
Mekong Delta Runoff Prediction Using Standardized Remotely-Sensed Water Balance Variables
Authors: Fok Hok Sum , Zhou Linghao , Ji Hang
Published: July 2020

A suitable routing model for predicting future monthly water discharge (WD) is essential for operational hydrology, including water supply, and hydrological extreme management, to mention but a few. This is particularly important for a remote area without a sufficient number of in-situ data, promoting the usage of remotely sensed surface variables. Direct correlation analysis between ground-observed WD and localized passive remotely-sensed surface variables (e.g., indices and geometric variables) has been studied extensively over the past two decades. Most of these related studies focused on the usage of constructed correlative relationships for estimating WD at ungauged locations. Nevertheless, temporal prediction performance of monthly runoff (R) (being an average representation of WD of a catchment) at the river delta reconstructed from the basin’s upstream remotely-sensed water balance variables via a standardization approach has not been explored. This study examined the standardization approach via linear regression using the remotely-sensed water balance variables from upstream of the Mekong Basin to reconstruct and predict monthly R time series at the Mekong Delta. This was subsequently compared to that based on artificial intelligence (AI) models. Accounting for less than 1% improvement via the AI-based models over that of a direct linear regression, our results showed that both the reconstructed and predicted Rs based on the proposed approach yielded a 2–6% further improvement, in particular the reduction of discrepancy in the peak and trough of WD, over those reconstructed and predicted from the remotely-sensed water balance variables without standardization. This further indicated the advantage of the proposed standardization approach to mitigate potential environmental influences. The best R, predicted from standardized water storage over the whole upstream area, attained the highest Pearson correlation coefficient of 0.978 and Nash–Sutcliffe efficiency of 0.947, and the lowest normalized root-mean-square error of 0.072.
Techniques and Applications in Water Science and Engineering
Authors: Zhou Jian Guo , Liu Haifei , Borthwick Alistair , Gualtieri Carlo
Published: July 2020

This Special Issue of Water on “Techniques and Applications in Water Science and Engineering” publishes selected high-quality research papers presented at the Inaugural International Symposium on Water Modelling (iSymWater2019). The symposium was hosted by Beijing Normal University and Manchester Metropolitan University, and took place during 8–10 July 2019 in Beijing, China. A wide range of research topics were considered, including hydraulic modelling, hydro-environment modelling, hydro-ecology modelling, water management simulation, physical experiments, and software. The Issue reports eight papers by researchers from many institutions around the world, and focuses on solving sustainable water challenges through theoretical and physical modelling approaches.
Mesozooplankton Selective Feeding on Phytoplankton in a Semi-Enclosed Bay as Revealed by HPLC Pigment Analysis
Authors: Feng Cui , Han Mengqi , Dong Chenchen , Jia Jingyi , Chen Jianwu , Wong Chong Kim , Liu Xiangjiang
Published: July 2020

Mesozooplankton have been known to be important consumers of phytoplankton, and the community plays an important role in removing the primary production in the marine ecosystem. In the present study, mesozooplankton grazing on phytoplankton were studied in situ at two sampling stations (TM4 and TM8) in Tolo Harbour. HPLC analysis showed that diatoms were the dominant phytoplankton in the two stations throughout the year, and contributed on average to over 40% of total phytoplankton biomass. Dinoflagellates were the second most abundant group of phytoplankton in the two monitoring stations, while the contribution of haptophytes, green algae, cyanobacteria, and cryptophytes was negligible. Feeding experiments, combined with HPLC pigment analysis, were conducted to measure mesozooplankton selective feeding on phytoplankton. The results demonstrated that mesozooplankton displayed a clear feeding selectivity for phytoplankton in Tolo Harbour. Firstly, mesozooplankton showed strong preference for the phytoplankton with the size of 20–200 μm, which suggested that the grazing selectivity and grazing rates of mesozooplankton were affected by the size of the food particles. On the other hand, mesozooplankton assemblages in Tolo Harbour displayed significant feeding selectivity for diatoms, dinoflagellates, and cryptophytes over other types of phytoplankton. The three algae groups are all the major phototrophic components in marine planktonic communities, and they often cause red tides in the marine environment. These results, taken together, suggested that mesozooplankton should play an important role in the regulation of red tides.
Role of the Hyporheic Zone in Increasing the Resilience of Mountain Streams Facing Intermittency
Authors: Bruno Maria Cristina , Doretto Alberto , Boano Fulvio , Ridolfi Luca , Fenoglio Stefano
Published: July 2020

We investigated the impact of intermittence in previously-perennial Alpine stream reaches, targeting the role of the hyporheic zone in increasing the resilience of these aquatic systems. We selected a perennial and an intermittent site in a reach of the Po River (North-Western Italy). We installed piezometers reaching −1 m (permanent and intermittent site), and −3 m (intermittent site) and monitored three supraseasonal droughts over a period of three years. We classified the hyporheic fauna into three categories of increasing affinity to life in the hyporheic (stygoxene, stygophile, stygobite), and used communities composition, abundance, beta-diversity and functional groups: (1) to compare assemblages at the same depth but with different hydrological characteristics, as well as assemblages from two depths at the intermittent site, and (2) to assess how the connection with surface water and the direction of the vertical aquifer flow determined the faunistic assemblages. Different taxonomic groups responded differently to intermittence, the hyporheic zone acted as a refuge increasing the resilience of the system, but resilience decreased with increasing degree of affinity to hyporheic life. Disentangling the effects of intermittence on the different faunistic component in the hyporheic zone can help guiding effective protection and restoration measures of river systems with temporary reaches.
Experimental Study at the Reservoir Head of Run-of-River Hydropower Plants in Gravel Bed Rivers. Part I: Delta Formation at Operation Level
Authors: Sindelar Christine , Gold Thomas , Reiterer Kevin , Hauer Christoph , Habersack Helmut
Published: July 2020

This study concerns scaled physical model tests of the delta formation process at the head of a run-of-river hydropower plant (RoR). It forms part of a larger research project to provide a scientific base for RoR sediment management strategies in medium-sized gravel bed rivers. The physical model consisted of an idealized river having a width of 20 m, a mean slope of 0.005, a mean flow rate of 22 m3/s and a 1-year flood flow of 104 m3/s. The model scale was 1:20. For the experiments, five different grain sizes were used, covering a range of 14 to 120 mm at 1:1 scale. Experiments were carried out under mobile-bed conditions at flow rates which correspond to 50%–80% of a 1-year flood HQ1. Even at the head of the reservoir, which is least influenced by the backwater effect of the RoR, sediment transport practically ceases for sediment fractions >14 mm for a flow rate of 0.7 × HQ1. The whole sediment load coming from the undisturbed upstream section accumulates at the head of the reservoir. This delta formation is accompanied by a substantial rise in water levels. A spatio-temporal scheme of the delta formation was derived from the experiments. The study proved that the delta formation increases the flood risk at the head of the reservoir. Conversely, reservoir drawdowns at flood events of high probability may be a promising strategy to enhance sediment connectivity under the specified boundary conditions.
Forecasting Urban Water Demand Using Cellular Automata
Authors: Marques de Oliveira Laís , Maria Oliveira da Silva Samíria , de Assis de Souza Filho Francisco , Maria Nunes Carvalho Taís , Locarno Frota Renata
Published: July 2020

Associating the dynamic spatial modeling based on the theory of cellular automata with remote sensing and geoprocessing technologies, this article analyzes what would be the per capita consumption behavior of Fortaleza-CE, located in the Northeast of Brazil, in 2017, had there not been a period of water scarcity between 2013 and 2017, and estimates the future urban water demand for the years 2021 and 2025. The weight of evidence method was applied to produce a transition probability map, that shows which areas will be more subject to consumption class change. For that, micro-measured water consumption data from 2009 and 2013 were used. The model was validated by the evaluation of diffuse similarity indices. A high level of similarity was found between the simulated and observed data (0.99). Future scenarios indicated an increase in water demand of 6.45% and 10.16% for 2021 and 2025, respectively, compared to 2017. The simulated annual growth rate was 1.27%. The expected results of urban water consumption for the years 2021 and 2025 are essential for local water resources management professionals and scientists, because, based on our results, these professionals will be able to outline future water resource management strategies.
Modeling the Spatial Distribution of Three Typical Dominant Wetland Vegetation Species’ Response to the Hydrological Gradient in a Ramsar Wetland, Honghe National Nature Reserve, Northeast China
Authors: Yan Dandan , Luan Zhaoqing , Xu Dandan , Xue Yuanyuan , Shi Dan
Published: July 2020

Water level fluctuations resulting from natural and anthropogenic factors have been projected to affect the functions and structures of wetland vegetation communities. Therefore, it is important to assess the impact of the hydrological gradient on wetland vegetation. This paper presents a case study on the Honghe National Nature Reserve (HNNR) in the Sanjiang Plain, located in Northeast China. In this study, 210 plots from 18 sampling line transects were sampled in 2011, 2012, and 2014 along the hydrological gradient. Using a Gaussian logistic regression model, we determined a relationship between three wetland plant species and a hydrologic indicator—a combination of the water level and soil moisture—and then applied that relationship to simulate the distribution of plants across a larger landscape by the geographic information system (GIS). The results show that the optimum ecological amplitude of Calamagrostis angustifolia to the hydrological gradient based on the probability of occurrence model was [0.09, 0.41], that of Carex lasiocarpa was [0.35, 0.57], and that of Carex pseudocuraica was [0.49, 0.77]. The optimum of Calamagrostis angustifolia was 0.25, Carex lasiocarpa was 0.46, and Carex pseudocuraica was 0.63. Spatial distribution probability maps were generated, as were maps detailing the distribution of the most suitable habitats for wetland vegetation species. Finally, the model simulation results were verified, showing that this approach can be employed to provide an accurate simulation of the spatial distribution pattern of wetland vegetation communities. Importantly, this study suggests that it may be possible to predict the spatial distribution of different species from the hydrological gradient.
Evaluation of CYGNSS Observations for Flood Detection and Mapping during Sistan and Baluchestan Torrential Rain in 2020
Authors: Rajabi Mahmoud , Nahavandchi Hossein , Hoseini Mostafa
Published: July 2020

Flood detection and produced maps play essential roles in policymaking, planning, and implementing flood management options. Remote sensing is commonly accepted as a maximum cost-effective technology to obtain detailed information over large areas of lands and oceans. We used remote sensing observations from Global Navigation Satellite System-Reflectometry (GNSS-R) to study the potential of this technique for the retrieval of flood maps over the regions affected by the recent flood in the southeastern part of Iran. The evaluation was made using spaceborne GNSS-R measurements over the Sistan and Baluchestan provinces during torrential rain in January 2020. This area has been at a high risk of flood in recent years and needs to be continuously monitored by means of timely observations. The main dataset was acquired from the level-1 data product of the Cyclone Global Navigation Satellite System (CYGNSS) spaceborne mission. The mission consisted of a constellation of eight microsatellites with GNSS-R sensors onboard to receive forward-scattered GNSS signals from the ocean and land. We first focused on data preparation and eliminating the outliers. Afterward, the reflectivity of the surface was calculated using the bistatic radar equations formula. The flooded areas were then detected based on the analysis of the derived reflectivity. Images from Moderate-Resolution Imaging Spectroradiometer (MODIS) were used for evaluation of the results. The analysis estimated the inundated area of approximately 19,644 km2 (including Jaz-Murian depression) to be affected by the flood in the south and middle parts of the Sistan and Baluchestan province. Although the main mission of CYGNSS was to measure the ocean wind speed in hurricanes and tropical cyclones, we showed the capability of detecting floods in the study area. The sensitivity of the spaceborne GNSS-R observations, together with the relatively short revisit time, highlight the potential of this technique to be used in flood detection. Future GNSS-R missions capable of collecting the reflected signals from all available multi-GNSS constellations would offer even more detailed information from the flood-affected areas.
Students’ Scientific Evaluations of Water Resources
Authors: Medrano Josh , Jaffe Joshua , Lombardi Doug , Holzer Margaret , Roemmele Christopher
Published: July 2020

Socially-relevant and controversial topics, such as water issues, are subject to differences in the explanations that scientists and the public (herein, students) find plausible. Students need to be more evaluative of the validity of explanations (e.g., explanatory models) based on evidence when addressing such topics. We compared two activities where students weighed connections between lines of evidence and explanations. In one activity, students were given four evidence statements and two models (one scientific and one non-scientific alternative); in the other, students chose four out of eight evidence statements and three models (two scientific and one non-scientific). Repeated measures analysis of variance (ANOVA) showed that both activities engaged students’ evaluations and differentially shifted students’ plausibility judgments and knowledge. A structural equation model suggested that students’ evaluation may influence post-instructional plausibility and knowledge; when students chose their lines of evidence and explanatory models, their evaluations were deeper, with stronger shifts toward a scientific stance and greater levels of post-instructional knowledge. The activities may help to develop students’ critical evaluation skills, a scientific practice that is key to understanding both scientific content and science as a process. Although effect sizes were modest, the results provided critical information for the final development and testing stage of these water resource instructional activities.
Non-Fickian Solute Transport in Rough-Walled Fractures: The Effect of Contact Area
Authors: Hu Yingtao , Xu Wenjie , Zhan Liangtong , Ye Zuyang , Chen Yunmin
Published: July 2020

The influence of contact area, caused by normal deformation, on fluid flow and solute transport through three-dimensional (3D) rock fractures is investigated. Fracture surfaces with different Hurst exponents (H) were generated numerically using the modified successive random addition (SRA) method. By applying deformations normal to the fracture surface (Δu), a series of fracture models with different aperture distributions and contact area ratios (c) were simulated. The results show that the contact area between the two fracture surfaces increases and more void spaces are reduced as deformation (Δu) increases. The streamlines in the rough-walled fractures show that the contact areas result in preferential flow paths and fingering type transport. The non-Fickian characteristics of the “early arrival” and “long tail” in all of the breakthrough curves (BTCs) for fractures with different deformation (Δu) and Hurst parameters (H) were determined. The solute concentration distribution index (CDI), which quantifies the uniformity of the concentration distribution within the fracture, decreases exponential as deformation (Δu) and/or contact area ratios (c) increase, indicating that increased contact area can result in a larger delay rate of mass exchange between the immobile zone around the contact areas and the main flow channel, thus, resulting in a longer time for the solute to fill the entire fracture. The BTCs were analyzed using the continuous time random walk (CTRW) inverse model. The inverse modeling results show that the dispersion exponent β decreases from 1.92 to 0.81 as c increases and H decreases, suggesting that the increase in contact area and fracture surfaces enhance the magnitude of the non-Fickian transport.
Kinetic and Prediction Modeling Studies of Organic Pollutants Removal from Municipal Wastewater using Moringa oleifera Biomass as a Coagulant
Authors: Adelodun Bashir , Ogunshina Matthew Segun , Ajibade Fidelis Odedishemi , Abdulkadir Taofeeq Sholagberu , Bakare Hashim Olalekan , Choi Kyung Sook
Published: July 2020

This study investigated the potential of Moringa oleifera (MO) seed biomass as a coagulant for the removal of turbidity, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) of municipal wastewater. Triplicated laboratory experiments using MO coagulant added at varying treatment dosages of 50, 100, 150, 200 mg/L, and a control (0 mg/L) treatment were performed for a settling period of 250 min at room temperature. Kinetics and prediction variables of cumulative turbidity, BOD, and COD removal were estimated using simplified first order and modified Gompertz models. Results showed that the maximum removal of turbidity, BOD, and COD were 94.44%, 68.72%, and 57.61%, respectively, using an MO dose of 150 mg/L. Various kinetic parameters, such as rate constant (r), measured (REm) versus predicted (REp) cumulative removal, and specific pollutant removal rate (µm), were also maximum when an MO dose of 150 mg/L was added, the standard error being below 5%. The developed models were successfully validated over multiple observations. This study suggests low cost and sustainable removal of turbidity, BOD, and COD of municipal wastewater using MO seed biomass as a coagulant.
Sorption Characteristics and Removal Efficiency of Organic Micropollutants in Drinking Water Using Granular Activated Carbon (GAC) in Pilot-Scale and Full-Scale Tests
Authors: Golovko Oksana , de Brito Anton Luana , Cascone Claudia , Ahrens Lutz , Lavonen Elin , Köhler Stephan J.
Published: July 2020

Granulated active carbon (GAC) is commonly used as a chemical barrier for the removal of organic micropollutants (OMPs) in drinking water treatment plants (DWTPs). However, little is known about the impact of dissolved organic carbon (DOC) and its long-term performance with regard to OMP removal efficiency. This study examined the performance of two GAC types (Norit 830W and Filtrasorb 400) in the removal of OMPs and DOC from natural lake water, in pilot-scale and full-scale tests run for almost one year. Potential early warning indicators of the exhaustion of GAC sorption capacity were also evaluated. The seven OMPs investigated (carbamazepine, lamotrigine, cetirizine, fexofenadine, oxazepam, fluconazole and N,N-diethyl-meta-toluamide (DEET)) all showed decreasing removal efficiencies after ~20,000 bed volumes (BV) in the pilot-scale Norit 830W and Filtrasorb 400 columns. However, columns with an 18-min empty bed contact time (EBCT) showed better performances than columns with 6-min EBCT. DEET was the OMP adsorbed most weakly. We found that DOC concentrations, methylene blue sorption kinetics, UV and fluorescence did not sufficiently explain the OMP breakthrough in the GAC columns. We concluded that carbamazepine, lamotrigine and fexofenadine can be used as indicators of decreasing GAC adsorption performance, due to their later breakthrough. Based on the results, UV and fluorescence removal could be used for the early detection of declining DOC removal, and online solid-phase extraction (SPE)–liquid chromatography–tandem mass spectrometry (SPE-LC-MS/MS) could be used for the early detection of OMPs in drinking water.
Feasible Ways Promoting Nitrate Removal in Riparian Zone Downstream of a Regulated River
Authors: Liu Dongsheng , Zhu Bei , Zhu Haoyu , Zhao Jian
Published: July 2020

Set in the downstream riparian zone of Xin’an River Dam, this paper established a 2D transversal coupling flow and solute transport and reaction model by verification within situ groundwater level and temperature. The denitrifying methods and principles in the riparian zone from the perspective of hyporheic exchange were explored, which provided a basis for the engineering techniques for river ecological restoration. Our studies have shown that under the condition of water level fluctuation, a biological method such as adding denitrifying bacteria biomass to a fixed degree (the same below) can greatly increase the denitrifying rate (1.52 g/d) in the riparian zone; chemical methods such as adding organic carbon into the surface water or groundwater can increase the total riparian nitrate removal (8.00–8.18 g) and its efficiency (19.5–20.0%) to a great extent; hydrogeological methods such as silt cleaning of the aquifer surface or local pumping around the contaminated area can increase the total riparian nitrate removal (1.06–14.8 g) to some extent, but correspondingly reduce the denitrifying efficiency (0.95–1.4%); physical methods such as designing the bank form into gentle slope or concave shape can slightly increase the total riparian nitrate removal (0.22–0.52 g) and correspondingly improve the denitrifying efficiency (0.25–0.85%). At the application level of river ecological restoration, integrated adopting the above methods can make the riparian denitrifying effect “fast and good”.
Debris Flow Susceptibility Assessment Using the Integrated Random Forest Based Steady-State Infinite Slope Method: A Case Study in Changbai Mountain, China
Authors: Si Alu , Zhang Jiquan , Zhang Yichen , Kazuva Emmanuel , Dong Zhenhua , Bao Yongbin , Rong Guangzhi
Published: July 2020

Debris flow events often pose significant damage and are a threat to infrastructure and even livelihoods. Recent studies have mainly focused on determining the susceptibility of debris flow using deterministic or heuristic/probabilistic models. However, each type of model has its own significant advantages with some irreparable disadvantages. The random forest model, which is sensitive to the region where the terrain conditions are suitable for the occurrence of debris flow, was applied along with the steady-state infinite slope method, which is capable of describing the initiation mechanism of debris flow. In this manner, a random-forest-based steady-state infinite slope method was used to conduct susceptibility assessment of debris-flow at Changbai mountain area. Results showed that the assessment accuracy of the proposed random-forest-based steady-state infinite slope method reached 90.88%; however, the accuracy of just the random forest model or steady-state infinite slope method was only 88.48% or 60.45%, respectively. Compared with the single-model assessment results, the assessment accuracy of the proposed method improved by 2.4% and 30.43%, respectively. Meanwhile, the debris-flow-prone area of the proposed method was reduced. The random-forest-based steady-state infinite slope method inherited the excellent diagnostic performance of the random-forest models in the region where the debris flow disaster already occurred; meanwhile, this method further refined the debris-flow-prone area from the suitable terrain area based on physico-mechanical properties; thus, the performance of this method was better than those of the other two models.
Shift Detection in Hydrological Regimes and Pluriannual Low-Frequency Streamflow Forecasting Using the Hidden Markov Model
Authors: Rolim Larissa , de Souza Filho Francisco
Published: July 2020

Improved water resource management relies on accurate analyses of the past dynamics of hydrological variables. The presence of low-frequency structures in hydrologic time series is an important feature. It can modify the probability of extreme events occurring in different time scales, which makes the risk associated with extreme events dynamic, changing from one decade to another. This article proposes a methodology capable of dynamically detecting and predicting low-frequency streamflow (16–32 years), which presented significance in the wavelet power spectrum. The Standardized Runoff Index (SRI), the Pruned Exact Linear Time (PELT) algorithm, the breaks for additive seasonal and trend (BFAST) method, and the hidden Markov model (HMM) were used to identify the shifts in low frequency. The HMM was also used to forecast the low frequency. As part of the results, the regime shifts detected by the BFAST approach are not entirely consistent with results from the other methods. A common shift occurs in the mid-1980s and can be attributed to the construction of the reservoir. Climate variability modulates the streamflow low-frequency variability, and anthropogenic activities and climate change can modify this modulation. The identification of shifts reveals the impact of low frequency in the streamflow time series, showing that the low-frequency variability conditions the flows of a given year.
Assessment of the Urban Water Security in a Severe Water Stress Area–Application to Palestinian Cities
Authors: Jabari Samah , Shahrour Isam , El Khattabi Jamal
Published: July 2020

This paper presents an assessment of the urban water security in a severe water stress area using a semi-quantitative risk-based approach. Water security indicators are selected according to the recommendations of international institutions, the literature review and the opinion of a panel of water experts. Selected indicators cover three fields: water resources, water services and water governance. The field of water resources is described by indicators related to the water resources availability, annual precipitation and the ratio of treated water, while the water services field is described by indicators related to the water service coverage, water losses and the continuity of water supply. Water governance includes three indicators: role and responsibility, access to water information and stakeholder engagement. Water security assessment is conducted in three stages: (i) data collection for five Palestinian cities in the West Bank of Jordan, (ii) determination of the risk score for each indicator using collected data and an expert’s opinion, (iii) determination of the global water security score and water security index using the matrix risk assessment and the wise weight assessment ratio analysis (SWARA) methods. Results show that water risk is ranked as extreme for all cities. Risk related to water resources is a major contributor to global risk, followed by water governance.
Biocontrol of Phytopathogens under Aquaponics Systems
Authors: Rivas-García Tomás , González-Estrada Ramsés Ramón , Chiquito-Contreras Roberto Gregorio , Reyes-Pérez Juan José , González-Salas Uriel , Hernández-Montiel Luis Guillermo , Murillo-Amador Bernardo
Published: July 2020

Aquaponics is an alternative method of food production that confers advantages of biological and economic resource preservations. Nonetheless, one of the main difficulties related to aquaponics systems could be the outbreak and dissemination of pathogens. Conventional treatments need to be administrated carefully because they could be harmful to human, fish, plants and beneficial microorganisms. Aquaponics practitioners are relatively helpless against plant diseases when they occur, especially in the case of root pathogens. Biological control agents (BCAs) may be an effective alternative to chemical inputs for dealing with pathogens of plants under aquaponics systems. Research of BCAs on aquaponics systems is limited, but there are numerous publications on the use of BCAs to control plant pathogens under soilless systems which confirm its potential use on aquaponics systems. The present review summarized the principal plant pathogens, the conventional and alternative BCA treatments on aquaponics systems, while considering related research on aquaculture and soilless systems (i.e., hydroponic) for its applicability to aquaponics and future perspectives related to biological control. Finally, we emphasized the case that aquaponics systems provide relatively untapped potential for research on plant biological control agents. Biological control has the potential to reduce the perturbation effects of conventional treatments on microbial communities, fish and plant physiology, and the whole function of the aquaponics system.
Comparison of Uranium Isotopes and Classical Geochemical Tracers in Karst Aquifer of Ljubljanica River catchment (Slovenia)
Authors: Rovan Leja , Lojen Sonja , Zuliani Tea , Kanduč Tjaša , Petrič Metka , Horvat Barbara , Rusjan Simon , Štrok Marko
Published: July 2020

The karst aquifer of the Ljubljanica River catchment, which has numerous springs and sinks, presents an interesting environment for studying hydrogeological processes. This study aims to explore the behavior of U isotopes and to evaluate their use as tracers of hydrogeochemical processes as an alternative to classical geochemical tracers (i.e., physicochemical parameters, elemental ratios, and alkalinity) involved in water–rock interactions and water flow in this karst water system. Basic hydrochemical parameters, as well as the spatiotemporal variations of total U concentrations, 234U/238U activity ratios, and δ238U values, were monitored in water samples from springs and sinks under different hydrological conditions. The bedrock as the source of dissolved and detrital U was also analyzed. Multi-collector inductively couple plasma-mass spectrometry results reveal variations of the 234U/238U activity ratios, which are consistently negatively correlated with the discharge at most analyzed sites. Large 238U/235U isotope fractionation occurred during bedrock weathering, and the large variability of the measured δ238U values is seemingly unrelated to the lithological characteristics of the bedrock or discharge. Our results confirm that 234U/238U activity ratios in water can be used as a tracer for studying changes in groundwater flows and the mixing of waters of different origins under different hydrological conditions.
Evaluation of Reservoir-Induced Hydrological Alterations and Ecological Flow Based on Multi-Indicators
Authors: Li Mingqian , Liang Xiujuan , Xiao Changlai , Zhang Xuezhu , Li Guiyang , Li Hongying , Jang Wenhan
Published: July 2020

Although they fulfill various needs of human beings, reservoirs also cause hydrological regime variation in the downstream regions, thus affecting ecological diversity. Therefore, studying the reservoir-induced hydrological alterations and ecological effects is of great significance, as it could guide the regulation of the reservoir to protect the river ecology. In this study, taking the Taizi River as an example, the impact of a reservoir on hydrological alteration and ecological diversity was comprehensively evaluated through eco-flow indicators based on the flow duration curve and multiple hydrological indicators. The results reveal that: (1) Ecological indicators can be used to analyze the annual and seasonal changes in the streamflow after the construction of the reservoir. The high-flow values and frequency decrease after the construction of the reservoir, especially in the autumn, while the low-flow component values increase significantly, especially in spring and summer. (2) The main influencing factors of the ecological indicators can be reflected by the relationship with precipitation, as the annual ecosurplus is not significantly affected by the reservoir, while the ecodeficit is greatly affected, and the seasonal ecological indicators (especially in spring and summer) are greatly affected by the reservoir. (3) The indicators of hydrologic alteration (IHA) show significant changes after the construction of the reservoir and are consistent with the changes in the eco-flow indicators; the change in the Shannon index indicates that the ecological diversity reduced after construction of the reservoir. It is controlled by the reservoir, and a new equilibrium state appears. (4) The eco-flow indicators have a good correlation with the 32 IHAs; they can reflect the change information of most IHAs and can avoid statistical redundancy.
Photolytic Degradation of Tetracycline in the Presence of Ca(II) and/or Humic Acid
Authors: Li Si , He Yiyan , Kong Fanguang , Sun Weiling , Hu Jiangyong
Published: July 2020

Photolytic degradation of tetracycline (TC) was investigated in mono- and binary solute systems of Ca(II) and humic acid (HA) under UVA light emitting diode (UVA-LED) light irradiation. TC photolysis proceeded via pseudo-first-order reaction kinetics. The presence of Ca(II) significantly accelerated the degradation rate constants of TC, with the highest value at 0.0314 ± 0.0019 min−1 when the Ca(II) concentration was 5.0 mM. The promoted degradation was attributed to complexation of TC with Ca(II), which increased the light absorption. Absorbance and fluorescence measurements revealed that the strong complexation between TC and Ca(II) likely occurred via the C11 and C12 oxygen groups in the phenolic-diketone moiety of TC in nearly neutral solutions. The formation of HA-Ca(II) complex was found in the binary solute system of HA and Ca(II). Thus, the promotional effect of Ca(II) on photolysis was diminished by HA addition. The largest reduction of 32.5% in rate constants was observed with the highest Ca(II) concentration. Scavenger studies revealed that TC could undergo direct photolysis and self-sensitization by 1O2. These results suggest that the coexistence of HA and Ca(II) greatly influences the fate of TC in natural waters, which has important implications for understanding the behavior of antibiotics coexisting with other metal species and ligands.
Spatial Predictions of Debris Flow Susceptibility Mapping Using Convolutional Neural Networks in Jilin Province, China
Authors: Chen Yang , Qin Shengwu , Qiao Shuangshuang , Dou Qiang , Che Wenchao , Su Gang , Yao Jingyu , Nnanwuba Uzodigwe Emmanuel
Published: July 2020

Debris flows are a major geological disaster that can seriously threaten human life and physical infrastructures. The main contribution of this paper is the establishment of two–dimensional convolutional neural networks (2D–CNN) models by using SAME padding (S–CNN) and VALID padding (V–CNN) and comparing them with support vector machine (SVM) and artificial neural network (ANN) models, respectively, to predict the spatial probability of debris flows in Jilin Province, China. First, the dataset is randomly divided into a training set (70%) and a validation set (30%), and thirteen influencing factors are selected to build the models. Then, multicollinearity analysis and gain ratio methods are used to quantify the predictive ability of factors. Finally, the area under the receiver operatic characteristic curve (AUC) and statistical methods are utilized to measure the accuracy of the models. The results show that the S–CNN model gets the highest AUC value of 0.901 in the validation set, followed by the SVM model, the V–CNN model, and the ANN model. Three statistical methods also show that the S–CNN model produces minimum errors compared with other models. The S–CNN model is hailed as an important means to improve the accuracy of debris–flow susceptibility mapping and provides a reasonable scientific basis for critical decisions.
Attitudes and Beliefs of Students and Lecturers about Educational Theories: Results of a Mixed Methods Study
Authors: Siegel Stefan T. , Daumiller Martin
Published: July 2020

Educational theories are central for teacher education. Despite their theoretical relevance, students’ and lecturers’ understandings of educational theories and their theory-related attitudes and beliefs thereof are hardly understood. To elucidate these constructs and to test their relevance, we conducted a mixed methods study with 32 students and 12 lecturers. We found that both groups perceived educational theories as rather abstract concepts. Students reported rather negative attitudes and naïve beliefs. For both populations, we found that attitudes and beliefs were strongly tied to motivational and affective aspects when dealing with educational theories, which stresses their relevance for teaching and teacher education.