Vertical migration from surface soils to groundwater and source appointment of polycyclic aromatic hydrocarbons in epikarst spring systems, southwest China

Understanding the transfer process of polycyclic aromatic hydrocarbons (PAHs) in the karst terrain is of great importance to their ecological risk assessments, however, the impact of the vertical transfer of the soil PAHs on the underground water is largely unknown in the karst system. Here, the vertical distribution and the seasonal variation of 16 PAHs in the soils and the water of 4 epikarst spring catchments in Southwest China were investigated. The total concentration of the PAHs ranged within 61-3285 ng g in the soils, and 341-4969 ng L in the spring water. The vertical distribution of the PAHs in soils varied with ring numbers and altitude of the catchment. PAHs concentrations were linearly related with the total organic carbon (TOC) at different depths in the catchments 563-783 m above the sea level (A.S.L.). However, no correlation with TOC was observed in the catchment of a high altitude (2090 m A.S.L.), because the large water flux led to the fast migration of the 2-3 rings PAHs in soils. The PAHs in soils and springs were mainly derived from the combustion of grass/wood/coal, closely related with the primary fossil fuels used in this area. This study demonstrate that the groundwater was heavily polluted by PAHs in the karst terrains of Southwest China, due to the vertical transfer of PAHs from the surface soils, and effective protection was urgently needed

Reciprocal facilitation between annual plants and burrowing crabs:Implications for the restoration of degraded saltmarshes

Increasing evidence shows that facilitative interactions between species play an essential role in coastal wetland ecosystems. However, there is a lack of understanding of how such interactions can be used for restoration purposes in saltmarsh ecosystems. We therefore studied the mechanisms of reciprocal facilitative interactions between native annual plants, Suaeda salsa, and burrowing crabs, Helice tientsinensis, in a middle-elevation saltmarsh (with generally high plant density and moderate tides) in the Yellow River Delta of China. We investigated the relationship between the densities of the plants and crab burrows in different seasons. Then, we tested whether and how saltmarsh plants and crabs indeed facilitate each other in a series of field and laboratory experiments. Finally, we applied the results by creating a field-scale artificial approach for microtopographic modification to restore a degraded saltmarsh. We found that the density of plant seedlings in spring was positively correlated with the density of crab burrows in the previous autumn; moreover, the density of crab burrows was correlated with the density of plants in summer. The concave-convex surface microtopography created by crabs promoted seed retention and seedling establishment of saltmarsh plants in winter and spring. These plants in turn facilitated crabs by inhibiting predators, providing food and reducing physical stresses for crabs in summer and autumn. The experimental removal of saltmarsh plants decreased crab burrow density, while both transplanting and simulating plants in bare patches promoted crabs. The microtopographic modification, inspired by our new understanding of the interactions between saltmarsh plants and crabs, showed that these degraded saltmarsh ecosystems can be restored by a single ploughing intervention. Synthesis. Our results suggest a reciprocal facilitation between annual plants and burrowing crabs in a middle-elevation saltmarsh ecosystem. This knowledge yielded new restoration options for degraded coastal saltmarshes through the one-time ploughing initiation of microtopographic variation, which could promote the re-establishment of ecosystem engineers and lead to the efficient recovery of pioneer coastal vegetation and associated fauna

Characteristics and ecological risk assessment of polycyclic aromatic hydrocarbons in soil seepage water in karst terrains, southwest China

Concentrations of polycyclic aromatic hydrocarbons (PAHs) in soils and soil seepage waters were analyzed along with dissolved organic carbon (DOC) to investigate the ecological risks and factors controlling the subsurface transport of PAHs in karst terrain in southwest China. The concentrations of dissolved PAHs in soil seepage water increased with depth and the mean concentrations at a depth of 80 cm were relatively high (exceeding 1147 ng/L). PAH composition in soil seepage water was dominated by low molecular weight (LMW) PAHs, whereas those associated with soil matrix were dominated by high molecular weight (HMW) PAHs. The results revealed that HMW PAHs in soil seepage water were closer to the equilibrium of dissolution than LMW and medium molecular weight (MMW) PAHs. However, due to the carrier functions of dissolved organic matter (DOM) for HMW PAHs, all PAHs can be continuously dissolved in the soil seepage water from soil matrix as the water moved vertical downward through the profiles. During this process, dynamic sorption and desorption processes were occurring between constituents in the soil seepage water and the soil matrix. This study demonstrates soil seepage water has posed a high risk to the groundwater, and effective protection is urgently needed

Etude des systèmes de stockage thermique par thermocline avec garnissage

The thermocline packed-bed tank with sensible heat or latent heat fillers is a cost-effective option for thermal energy storage (TES). Its thermal performance is very dependent on the packing configurations to each fluid flow and temperature situation. The principal objective of this PhD dissertation is to study the influence factors for different configuration of fluid flow and tank design, and then to conduct multi-layered packing configuration optimization of the storage tank. It starts by exploring the wall impact on thermocline and global thermal performance in dynamic conditions.Then, various influences, including the inlet configuration, the insulation, the filler size, and the operating parameters, on the thermocline in radial and axial direction based on a basic sensible heat filler tank are investigated. After that, the multi-layered configuration optimization of phase change material storage tank using a multi-objective genetic algorithm in multiple cycling is carried out by integrating the tank into an agriculture greenhouse application. The thermal performance of optimal tanks in seasonal operations is studied to find the potential for improvement of future work.Un réservoir thermocline avec un garnissage constitué de matériaux pour du stockage thermique sensible et/ou latent est une solution prometteuse pour le stockage d’énergie thermique (TES). Les performances d’un tel réservoir sont très dépendantes de la configuration physique, et des matériaux du garnissage. Ainsi, il existe un optimum pour chaque cas d’usage même si quelques règles générales sont conservées. L’objectif de cette thèse consiste à d’abord étudier l’effet de ces différents paramètres géométriques, physiques et thermo-hydrauliques sur l’efficacité du stockage. Une étude d’optimisation est réalisée afin de déterminer la meilleure configuration des paramètres pour un objectif donné. La première partie du manuscrit traite de l’impact des parois sur l’évolution de la thermocline et sur l’efficacité globale de la charge/décharge du réservoir, au moyen d’un modèle numérique simplifié prenant en compte ces effets tout en restant rapide à résoudre.Ensuite, les effets de la configuration du diffuseur d’entrée/sortie, de l’isolation thermique et des paramètres de charge/décharge sont étudiés expérimentalement sur un banc de tests dédié. Cette expérience a permi également de valider le modèle numérique. Ce modèle numérique est ensuite utilisé pour mener une optimisation avec une configuration multi-couches et multi-matériaux du garnissage grâce à un algorithme génétique multi-objectifs pour différents types de cycles de charge/décharge. Cette méthodologie est notamment mise en oeuvre pour une application de stockage thermique dédiée à une serre horticole . Le manuscrit décrit, enfin, des pistes à développer pour des travaux futurs

Review of Core Annular Flow

With the increasing demand for heavy oil, core annular flow (CAF) is an economical method to transport heavy oil, and many researchers have explored the energy-saving aspects of the CAF method. This paper presents a review of CAF energy saving and factors affecting CAF energy saving. Among them, the energy saving of CAF mainly concerns the changes in pressure drop and drag reduction efficiency; the factors affecting the energy saving of CAF mainly concern the problem of stability, the issue of restarting the pipeline system, the impact of a nozzle, the impact of fouling on the flow in the pipe, and the problem of oil–water accumulation. The aim of this paper is to provide a reference for the practical application of CAF in heavy oil transportation

Etude des systèmes de stockage thermique par thermocline avec garnissage

Un réservoir thermocline avec un garnissage constitué de matériaux pour du stockage thermique sensible et/ou latent est une solution prometteuse pour le stockage d’énergie thermique (TES). Les performances d’un tel réservoir sont très dépendantes de la configuration physique, et des matériaux du garnissage. Ainsi, il existe un optimum pour chaque cas d’usage même si quelques règles générales sont conservées. L’objectif de cette thèse consiste à d’abord étudier l’effet de ces différents paramètres géométriques, physiques et thermo-hydrauliques sur l’efficacité du stockage. Une étude d’optimisation est réalisée afin de déterminer la meilleure configuration des paramètres pour un objectif donné. La première partie du manuscrit traite de l’impact des parois sur l’évolution de la thermocline et sur l’efficacité globale de la charge/décharge du réservoir, au moyen d’un modèle numérique simplifié prenant en compte ces effets tout en restant rapide à résoudre.Ensuite, les effets de la configuration du diffuseur d’entrée/sortie, de l’isolation thermique et des paramètres de charge/décharge sont étudiés expérimentalement sur un banc de tests dédié. Cette expérience a permi également de valider le modèle numérique. Ce modèle numérique est ensuite utilisé pour mener une optimisation avec une configuration multi-couches et multi-matériaux du garnissage grâce à un algorithme génétique multi-objectifs pour différents types de cycles de charge/décharge. Cette méthodologie est notamment mise en oeuvre pour une application de stockage thermique dédiée à une serre horticole . Le manuscrit décrit, enfin, des pistes à développer pour des travaux futurs.The thermocline packed-bed tank with sensible heat or latent heat fillers is a cost-effective option for thermal energy storage (TES). Its thermal performance is very dependent on the packing configurations to each fluid flow and temperature situation. The principal objective of this PhD dissertation is to study the influence factors for different configuration of fluid flow and tank design, and then to conduct multi-layered packing configuration optimization of the storage tank. It starts by exploring the wall impact on thermocline and global thermal performance in dynamic conditions.Then, various influences, including the inlet configuration, the insulation, the filler size, and the operating parameters, on the thermocline in radial and axial direction based on a basic sensible heat filler tank are investigated. After that, the multi-layered configuration optimization of phase change material storage tank using a multi-objective genetic algorithm in multiple cycling is carried out by integrating the tank into an agriculture greenhouse application. The thermal performance of optimal tanks in seasonal operations is studied to find the potential for improvement of future work

Etude des systèmes de stockage thermique par thermocline avec garnissage

The thermocline packed-bed tank with sensible heat or latent heat fillers is a cost-effective option for thermal energy storage (TES). Its thermal performance is very dependent on the packing configurations to each fluid flow and temperature situation. The principal objective of this PhD dissertation is to study the influence factors for different configuration of fluid flow and tank design, and then to conduct multi-layered packing configuration optimization of the storage tank. It starts by exploring the wall impact on thermocline and global thermal performance in dynamic conditions. Then, various influences, including the inlet configuration, the insulation, the filler size, and the operating parameters, on the thermocline in radial and axial direction based on a basic sensible heat filler tank are investigated. After that, the multi-layered configuration optimization of phase change material storage tank using a multi-objective genetic algorithm in multiple cycling is carried out by integrating the tank into an agriculture greenhouse application. The thermal performance of optimal tanks in seasonal operations is studied to find the potential for improvement of future work.Un réservoir thermocline avec un garnissage constitué de matériaux pour du stockage thermique sensible et/ou latent est une solution prometteuse pour le stockage d’énergie thermique (TES). Les performances d’un tel réservoir sont très dépendantes de la configuration physique, et des matériaux du garnissage. Ainsi, il existe un optimum pour chaque cas d’usage même si quelques règles générales sont conservées. L’objectif de cette thèse consiste à d’abord étudier l’effet de ces différents paramètres géométriques, physiques et thermo-hydrauliques sur l’efficacité du stockage. Une étude d’optimisation est réalisée afin de déterminer la meilleure configuration des paramètres pour un objectif donné. La première partie du manuscrit traite de l’impact des parois sur l’évolution de la thermocline et sur l’efficacité globale de la charge/décharge du réservoir, au moyen d’un modèle numérique simplifié prenant en compte ces effets tout en restant rapide à résoudre. Ensuite, les effets de la configuration du diffuseur d’entrée/sortie, de l’isolation thermique et des paramètres de charge/décharge sont étudiés expérimentalement sur un banc de tests dédié. Cette expérience a permi également de valider le modèle numérique. Ce modèle numérique est ensuite utilisé pour mener une optimisation avec une configuration multi-couches et multi-matériaux du garnissage grâce à un algorithme génétique multi-objectifs pour différents types de cycles de charge/décharge. Cette méthodologie est notamment mise en oeuvre pour une application de stockage thermique dédiée à une serre horticole. Le manuscrit décrit, enfin, des pistes à développer pour des travaux futurs

Long term detection of water depth changes of coastal wetlands in the Yellow River Delta based on distributed scatterer interferometry

Coastal wetland ecosystems are among the most productive yet highly threatened systems in the world, and population growth and increasing economic development have resulted to extremely rapid degradation and loss of coastal wetlands. Spaceborne differential Interferometry SAR has proven a remarkable potential in wetland applications, including water level monitoring in high spatial resolution. However, due to the absence of ground observations for calibration and validation, long term monitoring of water depth, which is essential to evaluate ecosystem health of wetlands, is difficult to be estimated from spaceborne InSAR data. We present a new differential synthetic aperture radar method for temporal evolution of water depth in wetlands. The presented technique is based on distributed scatter interferogram technique in order to provide a spatially dense hydrological observation for coastal wetlands, which are characterized by high temporal decorrelation. This method adapts a strategy by forming optimum interferogram network to get a balance between maximum interferometric information preservation and computational cost reduction, and implements spatial adaptive filtering to reduce noise and enhance fringe visibility on distributed scatterers. Refined InSAR observation is tied to absolute reference frame to generate long term high resolution water level time-series using stage data. We transform water level time-series to long term observation of water depth with assistance of a dense measurement network of water depth. We present water depth time-series obtained using the data acquired from 2007 to 2010 by the ALOS satellite, which supplied significant information to evaluate ecological performance of wetland restoration in the Yellow River Delta

3D structure fungi-derived carbon stabilized stearic acid as a composite phase change material for thermal energy storage

Stearic acid (SA)/fungi-derived carbon (FDC) composite phase change materials (PCM) were fabricated by vacuum impregnation, where three types of FDC (FDC-C, FDC-H, and FDC-K) as carrier were synthesized by diverse synthetic procedures of carbonization. The FDC-K modified by synergistic hydrothermal and KOH-assisted calcination process had a 3D-cellular structure with considerably higher inner surface area (1799.48 m2 g−1) and cumulative pore volume (0.7476 cm3 g−1) than other matrixes, leading to that a loading capability value of SA (LC, %) in SA/FDC-K composite was up to 344.64%. X-ray diffraction and Fourier transform infrared spectroscopy shown that physical interaction instead of chemical reaction happened between FDC and SA. X-ray photoelectron spectroscopy indicated that KOH-assisted calcination treatment improved oxygenic functional groups on matrix surface so that facilitating SA loading. Raman spectra illustrated the IG/ID value of three amorphous carbons were ∼1.04. For SA/FDC-K composite, it had a melting and freezing enthalpy of 144.8 J g−1 and 142.6 J g−1, respectively, and phase transition point of 52.72 °C and 52.95 °C, respectively. The thermal conductivity (0.574 W m−1 K−1) was 115% higher than pure SA. It was also stable in terms of thermal and chemical after thermal cycles in heating and cooling. Thus, the SA/FDC-K exhibited high phase transition enthalpy and excellent thermal stability has potential application in thermal energy storage.This work was supported by the National Natural Science Foundation of China (51874047, 51504041); the Training Program for Excellent Young Innovators of Changsha (kq1802007); the Fund for University Young Core Instructors of Hunan Province; the Natural Science Foundation of Hunan Province (2016JJ3009); and the Hunan Province 2011 Collaborative Innovation Center of Clean Energy and Smart Grid