An explicit hydrological algorithm for basic flow and transport equations and its application in agro-hydrological models for water and nitrogen dynamics

Hydrological simulation is a key component in argo-hydrological models for optimizing resources use and minimizing the environmental consequences in agriculture. In this study we extended a simple and explicit algorithm for solving the basic soil water flow equation by Yang et al. (J. Hydrol. 370, 177-190) to the solute transport equation. The key feature of the algorithm is to use a uniform soil layer thickness and a small time step in solving the soil water and solute transport equations, so that the calculations can be made on a layer basis. This drastically simplifies the procedure of modeling water and solute transport in soil using the basic equations. The proposed algorithm was tested against the complex finite element (FE) numerical scheme in simulating soil water and solute transport in different soils via numerical experiments. The results showed that the proposed algorithm with a uniform soil layer thickness of 5 cm and a small time step of 0.001d was able to achieve the identical accuracy as the FE method. Tests of the proposed algorithm in simulating water and nitrogen dynamics against data from a field experiment on wheat revealed that the predicted results with the simple algorithm were in good agreement with the time-course measurements of soil water and mineral N concentration at the various depths in the profile, suggesting that the proposed algorithm performed well and can be reliably applied in agro-hydrological models. The simplicity and accuracy of the algorithm will encourage scientists to use basic equations for soil water and solute transport more in the future for improving performance of agro-hydrological models

An easily implemented agro-hydrological procedure with dynamic root simulation for water transfer in the crop–soil system: validation and application

Models for water transfer in the crop–soil system are key components of agro-hydrological models for irrigation, fertilizer and pesticide practices. Many of the hydrological models for water transfer in the crop–soil system are either too approximate due to oversimplified algorithms or employ complex numerical schemes. In this paper we developed a simple and sufficiently accurate algorithm which can be easily adopted in agro-hydrological models for the simulation of water dynamics. We used a dual crop coefficient approach proposed by the FAO for estimating potential evaporation and transpiration, and a dynamic model for calculating relative root length distribution on a daily basis. In a small time step of 0.001 d, we implemented algorithms separately for actual evaporation, root water uptake and soil water content redistribution by decoupling these processes. The Richards equation describing soil water movement was solved using an integration strategy over the soil layers instead of complex numerical schemes. This drastically simplified the procedures of modeling soil water and led to much shorter computer codes. The validity of the proposed model was tested against data from field experiments on two contrasting soils cropped with wheat. Good agreement was achieved between measurement and simulation of soil water content in various depths collected at intervals during crop growth. This indicates that the model is satisfactory in simulating water transfer in the crop–soil system, and therefore can reliably be adopted in agro-hydrological models. Finally we demonstrated how the developed model could be used to study the effect of changes in the environment such as lowering the groundwater table caused by the construction of a motorway on crop transpiration

Crowdsourcing Methods for Data Collection in Geophysics: State of the Art, Issues, and Future Directions

Data are essential in all areas of geophysics. They are used to better understand and manage systems, either directly or via models. Given the complexity and spatiotemporal variability of geophysical systems (e.g., precipitation), a lack of sufficient data is a perennial problem, which is exacerbated by various drivers, such as climate change and urbanization. In recent years, crowdsourcing has become increasingly prominent as a means of supplementing data obtained from more traditional sources, particularly due to its relatively low implementation cost and ability to increase the spatial and/or temporal resolution of data significantly. Given the proliferation of different crowdsourcing methods in geophysics and the promise they have shown, it is timely to assess the state‐of‐the‐art in this field, to identify potential issues and map out a way forward. In this paper, crowdsourcing‐based data acquisition methods that have been used in seven domains of geophysics, including weather, precipitation, air pollution, geography, ecology, surface water and natural hazard management are discussed based on a review of 162 papers. In addition, a novel framework for categorizing these methods is introduced and applied to the methods used in the seven domains of geophysics considered in this review. This paper also features a review of 93 papers dealing with issues that are common to data acquisition methods in different domains of geophysics, including the management of crowdsourcing projects, data quality, data processing and data privacy. In each of these areas, the current status is discussed and challenges and future directions are outlined

An explicit hydrological algorithm for basic flow and transport equations and its application in agro-hydrological models for water and nitrogen dynamics

Hydrological simulation is a key component in argo-hydrological models for optimizing resources use and minimizing the environmental consequences in agriculture. In this study we extended a simple and explicit algorithm for solving the basic soil water flow equation by Yang et al. (2009) to the solute transport equation. The key feature of the algorithm is to use a uniform soil layer thickness and a small time step in solving the soil water and solute transport equations, so that the calculations can be made on a layer basis. This drastically simplifies the procedure of modeling water and solute transport in soil using the basic equations. The proposed algorithm was tested against the complex finite element (FE) numerical scheme in simulating soil water and solute transport in different soils via numerical experiments. The results showed that the proposed algorithm with a uniform soil layer thickness of 5 cm and a small time step of 0.001 d was able to achieve the identical accuracy as the FE method. Tests of the proposed algorithm in simulating water and nitrogen dynamics against data from a field experiment on wheat revealed that the predicted results with the simple algorithm were in good agreement with the time-course measurements of soil water and mineral N concentration at the various depths in the profile, suggesting that the proposed algorithm performed well and can be reliably applied in agro-hydrological models. The simplicity and accuracy of the algorithm will encourage scientists to use basic equations for soil water and solute transport more in the future for improving performance of agro-hydrological models.Richards' equation Transport equation Soil-crop system Soil water movement Solute transport

Beneficial Utilization of Rice Husk Ash (RHA) as a New Sorbent for Removal of Antimony (III) from Water

This study represents the first scientific effort to evaluate the technical feasibility of rice husk ashes (RHA; ash burned after RH) as a new water treatment material for adsorption of Sb(III) from drinking water. Three RHA samples (RHA300, RHA450, RHA600) were prepared from RH at 300, 450 and 600 °C, respectively. Compared with RH, RHA had great specific surface areas, small particle sizes, and large total pore volumes. Moreover, the RHA was characterized by an amorphous structure. In the subsequent bench-scale tests, the RHA samples were utilized to adsorb Sb(III) from water. Kinetics tests showed that pseudo firstorder and pseudo second-order kinetics models both well fit the experimental data, and Sb(III) sorption rates followed the order of RHA450 \u3e RHA600\u3e RHA300 \u3e RH. Among the 4 tested adsorption isotherm models (Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich), the Langmuir isotherm was the best one to fit the measured data, and the adsorption capacities of RHA300, RHA450 and RHA600 were 1.407, 3.842 and 2.731 mg/g, respectively. Solution pH, natural organic matters (NOMs) and certain cations (e.g. Fe3+ and Fe2+) were significant factors controlling the adsorption process. RHA300 adsorption was increased with increasing pH from 2 to 12, while RHA450 and RHA600 showed a high adsorption potential at pHs 4-10. Their maximum adsorption capacities were observed at pH values where the lowest zeta potentials were found. Fe3+ and Fe2+ both greatly inhibited RHA adsorption of Sb(III). In contrast, K+, Na+, Mn2+ and Cu2+, as well as humic acid (HA) (the major NOM fraction), had a minor impact upon the adsorption. Our results demonstrate that RHA is a technically effective sorbent to address the Sb(III) pollution in water

Degradation Effect of Sulfa Antibiotics by Potassium Ferrate Combined with Ultrasound (Fe(VI)-US)

Sulfa antibiotics are a family of typical broad-spectrum antibiotics, which have become one of the most frequently detected antibiotics in water, posing a great threat to human health and ecosystem. Potassium ferrate is a new type of high-efficiency multifunctional water treatment agent, collecting the effects of oxidation, adsorption, flocculation, coagulation, sterilization, and deodorization. Performance and mechanism of degradation of typical broad-spectrum antibiotics by Fe(VI)-US were further studied, investigating the degradation effect of sulfa antibiotics by single ultrasound, single potassium ferrate, and potassium ferrate-ultrasound (Fe(VI)-US). It was found that Fe(VI)-US technology had a significant role in promoting the degradation of sulfa antibiotics via orthogonal experiments. Factors evaluated included sulfa antibiotics type, pH value, potassium ferrate dosage, ultrasonic frequency, and ultrasonic power, with the pH value and potassium ferrate dosage being affected most significantly. One reason for synergy facilitating the degradation is the common oxidation of potassium ferrate and ultrasound, and the other is that Fe(III) produced promotes the degradation rate. According to the product analysis and degradation pathways of three sulfa antibiotics, ferrate-sonication sulfa antibiotics are removed by hydroxyl radical oxidation

Hydrothermal Synthesis of Hydrangea-Like F-Doped Titania Microspheres for the Photocatalytic Degradation of Carbamazepine under UV and Visible Light Irradiation

Hydrangea-like F-doped TiO2 microspheres have been synthesized on a large scale by a simple hydrothermal process using potassium titanium oxalate as the titanium source, ammonium fluoride and hydrogen peroxide as the etchant. The photocatalytic activities were evaluated using carbamazepine as the target organic molecule under UV and visible light irradiation. Structural characterization indicates that the hydrangea-like TiO2 microspheres, with an average diameter of 2.80 μm, are composed of numerous anatase TiO2 petals. Moreover, it is found that both the NH4F and H2O2 dosages have important effects on the formation of the hydrangea-like structures. In addition, photocatalytic experiments show that the hydrangea-like TiO2 microspheres calcined at 500°C exhibit high photocatalytic efficiency under both UV and visible light irradiation. The enhanced photocatalytic activity can be attributed to the successful fluorine doping, good crystallinity, and the unique nanostructures

Occurrence of Algae and Algae-Related Taste and Odour (T&O) Compounds in the Qingcaosha Reservoir, China

This study examined the temporal and spatial variations in the occurrence of major algae and algaerelated taste and odour (T&O) compounds in Qingcaosha Reservoir, China. Water samples were collected monthly from seven sites in the reservoir and analysed using solid phase microextraction combined with gas chromatography-mass spectrometry. Results showed that green algae were dominant over the 9-month study. In addition, cyanobacteria in the summer and early autumn peaked at 3.2 ∼ 9.6 × 106 cell/L. Among the four most common algae-related T&O compounds, dimethyl trisulphide was undetectable at any of the sampling sites, and 2-methylisoborneol (2-MIB), geosmin and β-cyclocitral were frequently over their respective odour threshold levels from August through October. β-cyclocitral concentration was linearly correlated with the concentration of cyanobacteria (R2 = 0.9831). The peak β-cyclocitral concentrations varied from 452 to 1, 293 ng/L and were observed close to the water table. In contrast, high concentrations of 2-MIB and geosmin occurred in the water overlying sediments, probably because some of the 2-MIB and geosmin came from the micro-organisms in the sediments. These results provide important information regarding algae and algae-related T&O compounds in a typical reservoir in estuary and coastal areas, and will be helpful for developing appropriate strategies to minimize undesirable T&O issues in water sources

Efficient Reduction of Bromate by Iodide-Assisted UV/Sulfite Process

Bromate ( BrO 3 − ) residue in drinking water poses a great health risk. Ultra-fast reduction of BrO 3 − , under aerobic conditions, was realized using an ultraviolet (UV)/sulfite process in the presence of iodide (UV/sulfite/iodide). The UV/sulfite/iodide process produced BrO 3 − removal efficiency of 100% at about 5 min with complete conversion to bromide, while UV/sulfite induced 13.1% BrO 3 − reduction under the same conditions. Hydrated electrons, generated from the photolysis of sulfite and iodide, was confirmed as the main contributor to BrO 3 − degradation (77.4% of the total contribution). As the concentration of iodide was kept constant, its presence remarkably enhancing the generation of hydrated electrons led to its consideration as a homogeneous catalyst in the UV/sulfite/iodide system. Sulfite played a role not only as a hydrated electron precursor, but also as a reactive iodine species shielding agent and a regenerant of iodide. Results surrounding the effects on common water quality parameters (pH, bicarbonate, nitrate, natural organic matter, and solution temperature) indicated that preferred degradation of BrO 3 − occurred in an environment of alkaline pH, low-content natural organic matter/bicarbonate/nitrate, and high natural temperature