Nitrogen behavior during artificial groundwater recharge through ponds: A case study in Xiong'an New Area.

The Xiong'an New Area (XA) was established as a development hub in China. Excessive exploitation of groundwater has caused a series of environmental and geological problems, restricting further development of XA. The widely distributed ponds in this area have been targeted as convenient and efficient sites of artificial groundwater recharge. However, nitrogen accumulation in the shallow vadose zone associated with agricultural activities may pose environmental risks to groundwater during the recharge and infiltration process. Therefore, this study investigated the effects, transfer, and transformation of nitrogen during artificial groundwater recharge. The aeration zone is thick and the medium comprises fine particles, with total nitrogen and nitrate accumulation mainly in the shallow aeration zone. In indoor experiments, the nitrate removal rate reached 83.5% when organic carbon in the source water was increased by 10 mg/L. For Baigou diversion river water(BW) with slightly higher (14.46 mg/L) and lower (5.04 mg/L) nitrate contents, the nitrate content decreased by 26.0% (10.70 mg/L) and 26.8% (3.69 mg/L), respectively, after 150 days. When the water head was increased by 20 cm to increase the recharge rate, the time required for nitrate and ammonium to reach the maximum and equilibrium concentration was reduced by 50%. These findings indicate that nitrogen concentration in the source water, aeration zone media, and groundwater should be considered in pond replenishment. It is also necessary to control the concentration of organic carbon and the rate of recharge, which would provide guidance for other similar projects.

A study on the visual recognition patterns of multi-information guide signs based on eye movement data analysis.

A two-factor experiment was devised to assess the appropriateness of the quantity and arrangement of information on multi-information guide signs at unique, spacious exits on elevated expressway sections. This experiment investigated 77 signs containing varying amounts of road name information and different placements of destination road names. The research entailed an indoor experiment that incorporated eye-tracking technology and involved the analysis of a total of twenty-eight indicators. A comprehensive index system was developed, identifying three key aspects: visual recognition efficiency, visual recognition difficulty, and visual fatigue. Utilizing repeated measure analysis of variances, the impact of these two factors was examined to identify significant indicators and establish a comprehensive assessment indicator system. The Technique for Order of Preference by Similarity to Ideal Solution method, in conjunction with the coefficient of entropy weight, was employed to assess the effectiveness of these two factors. The findings demonstrated that the 28 eye-movement indicators utilized in this study effectively constitute a valuable indicator system for evaluating drivers' visual recognition characteristics. These indicators capture the subtle psychophysical traits inherent in the process of recognizing signs, including visual recognition efficiency, difficulty, and fatigue. Regarding the first experimental factor, the number of sign road names significantly influences drivers' visual recognition characteristics (Sig < 0.05). Specifically, an increase in the number of sign road names leads to diminished visual recognition efficiency and heightened visual recognition difficulty and fatigue. Consequently, it is advisable to restrict the number of sign road names to a maximum of six per sign under typical circumstances, with nine being the limit under special conditions. As for the second experimental factor, the placement of the destination road name within the sign layout exerts a significant impact on visual recognition characteristics (Sig < 0.05). Each type of multi-information sign exhibits a distinct visual recognition pattern. Generally, the upper portion of the sign is more easily recognized, while the lower part poses greater recognition challenges. Therefore, to mitigate visual recognition risks, it is recommended that road information placement be prioritized based on actual usage conditions.

Radium desorption behavior of riverine suspended sediment: Theoretical and experimental.

Radium desorption from riverine or suspended sediment is an important source term of Ra isotopes in estuarine water, which is one of the significant factors affecting the source/sink material balance for Ra applications, such as estimating submarine groundwater discharge flux in coastal zones. In this paper, a theoretical model is proposed to study Ra desorption considering several influencing factors, including salinity, particle size and size distribution, alpha recoil range of atoms in the sediment grains, and grain surface roughness. The results of the model parameter sensitivity analysis show that the alpha-decay recoil can improve the number of total exchangeable Ra on grain surfaces, but it is more significant for sediment of small grain size. Sediment with large mean grain size may contain a considerable number of smaller particles, which may facilitate the Ra desorption quantity. Due to the relatively low concentrations of Ra in natural mineral, the Ra desorption quantity is not sensitive to the roughness of the sediment grain surfaces. The model fits well with the indoor experimental data, by fitting the experimental data or quoting the literature values, the desorption parameters (A, B, α, ß) in the model can be determined to estimate the total number of exchangeable Ra of a sediment and also predict the Ra desorption of sediments in different conditions.

Chloride Transport Behaviour and Service Performance of Cracked Concrete Linings in Coastal Subway Tunnels.

The concrete lining in subway tunnels often undergoes cracking damage in coastal cities. The combination of cracked tunnel lining structures and high concentrations of corrosive ions in the groundwater (e.g., chlorine) can accelerate concrete erosion, reduce the mechanical performance of the lining structures and shorten the tunnel service life. This paper investigates the chloride ion concentration in the groundwater of several subway tunnels in the coastal city of Qingdao, China. Indoor experiments and numerical simulations are conducted to investigate the chloride ion transport behaviour and service performance of cracked concrete linings. The results are applied to predict the service life of lining structures. The crack depth in concrete linings is found to have the most significant effect on the transport rate of chloride ions, followed by the crack width. The numerical simulations are carried out using COMSOL software to study the chloride transport behaviour in cracked specimens and predict the service lifetimes of lining structures of different thicknesses, and the results correspond well with the experimental data. The durability of a concrete lining can be enhanced by increasing the thickness of the protective concrete layer. Additional measures are proposed for treating cracked concrete linings to resist chloride ion attack in subway tunnels.

Numerical and Experimental Study on the Steel Strands under the Coupling Effect of a Salt Spray Environment and Cyclic Loads.

Composed of multi-strand parallel high-strength wires or steel strands, the stayed cables have been widely used recently in stayed bridges or suspension bridges owing to their light weight and high bearing capacity, especially the steel strands. Meanwhile, chloride-induced corrosion of steel strands is one of the most considerable factors for the durability of the stayed cable exposed to marine environments. The fatigue caused by both cyclic loading and corrosion can affect the life of the steel strands. Besides, the current studies related to the effects of the aforementioned two impact factors on the life of the steel strands either considered the fatigue only, or took the two impact factors into account separately. The coupling effects of fatigue and corrosion on the life of the steel strands are required to be further explored and discussed. Consequently, it is essential to create a model to predict the life of the steel strands with the coupling effects taken into consideration. In this paper, an indoor physical experiment of the steel strand specimens exposed to marine tidal environment was carried out. To avoid accidental errors, the whole specimens were divided into 20 groups, with each group having two steel wires with a 5 days, 10 days, and 15 days cycle for the test. The corrosion of steel strands was observed at various exposure times and it was found that the pits were formed on the surface with the chloride ion erosion to the steel strands. Deeper and sharper pits result in greater pitting-local stress and a shorter fatigue life, which is also the main reason for reducing the carrying capacity of the steel strands. However, a detailed description for this problem is lacking in current domestic and foreign literature, because the pit is hard to predict owing to its complex nature. In order to simulate the evolution of the pits, the stochastic pitting-corrosion model was set up by the neural network method to evaluate the pit evolutions over time. In addition, an empirical formula consisting of length-width ratios, length-depth ratios, and depth-to-width ratios of the pits was obtained to determine the stress concentration factor based on the multi-dimensional linear regression method. The fatigue notch factor of components can be deduced by the stress concentration factor, and the life of the steel strands can be deduced by both of them. The findings are expected to be useful in realistically predicting the durability of wire structures.

Dataset of the PV surface temperature distribution when generating electricity (PV-On) and without generating electricity (PV-Off) using Halogen Solar Simulator.

These datasets present the Joule heating effect from our experimental series for the paper entitled, "Development and Experiment on the Performance of Collector with Polymeric Thermal Photovoltaic Thermal (PVT) Collector with Halogen Solar Simulator" [1]. The experiment was carried out before integrating the photovoltaic (PV) module part with the thermal (T) collector part into a hybrid PVT collector. The Joule heating effect was investigated from the surface temperature distribution of a PV module when generating electricity (PV-On). The irradiance was set to 1000 W/m2 using a pyranometer. After replacing by the PV module, the PV output has been set at the maximum power point (MPP) by setting the sliding variable resistor. The measurement took place at the rear side of the PV module to avoid the cable obstructing the light beam from the solar simulator, The thermocouples were installed at 10 points and connected to the data-logger. After steady-state in 30 minutes from starting the experiment, the measurements of the PV-On and PV-Off took place alternately 10 minutes by opening and closing the circuit. After completing the experiment, the light source was turned off for naturally cooling. These data is useful to provide an overview of PV surface temperature during PV-On and PV-Off. These datasets provide a more detailed picture of the temperature distribution on the PV surface to be more accurate in analyzing the performance of the PV module for simulation or field application. These datasets can be used as a reference for further improvements, especially in designing a more uniform solar simulator and understanding the operational modes of the PV module.