Water Mixing Processes Research Articles

Tidal-driven N2O emission is a stronger resister than CH4 to offset annual carbon sequestration in mangrove ecosystems.

The mangrove ecosystems store a significant amount of "blue carbon" to mitigate global climate change, but also serve as hotspots for greenhouse gases (GHGs: CO2, CH4 and N2O) production. The CH4 and N2O emissions offset mangrove carbon benefits, however, the extent of this effect remains inadequately quantified. By applying the 36h time-series observations and mapping cruises, here we investigated the spatial and temporal distribution of GHGs and their fluxes in Dongzhaigang (DZG) bay, the largest mangrove ecosystem in China, at tidal and monthly scales. The spatiotemporal variation of GHGs were mainly controlled by tidal-forced water mixing, outgassing and multiple biogeochemical processes. Tidal-driven porewater outwelling and sediment resuspension largely explained the excess addition of dissolved GHGs in tidal creeks. These lateral export combined with river input contribute significantly to surrounding water emission. Salinity controls CH4 emission in river-tidal creek-bay continuum, with concentration decreased by ∼100-fold from freshwater to seawater sites. N2O concentration was controlled by substrate supply for both nitrification and denitrification. Overall, the GHGs emissions in tidal creeks equal to 669-39,000 (7521±6401) g CO2-eq/m2/yr (CO2 contributed ∼88-91%) to atmosphere. In particular, CH4 and N2O contribute 8-366 (124±78) g CO2-eq/m2/yr and 59-2260 (712±525) g CO2-eq/m2/yr, together offsetting 8.7±2.1% of annual mangrove carbon sequestration, with a larger contribution from N2O (7.4%). Our findings highlight the importance of simultaneous quantification of non-CO2 GHGs to accurately assess blue carbon capacity.

A hydrogeochemical and isotopic approach for assessing the origin, recharge and mixing process of geothermal water in the Yinchuan Basin

The hydrogeochemistry of geothermal fluids is fundamental to reveal the genesis, recharge mechanism and circulation pattern of geothermal water. However, the origin and hydrogeochemical process of geothermal water in deep aquifer system still remain unclear. In this study, 17 water samples were analyzed to study the origin, recharge and mixing process of geothermal water in the Yinchuan basin by using a hydrogeochemical and isotopic approach. The results showed that the concentrations of major ions (SO42−, Na+, Cl−, TDS, Ca2+, K+, Mg2+ and NH4+) and trace elements (Li, F−, Br−, I−, Sr and Mn) in geothermal water are significantly greater than those in shallow water, hot spring and cold spring in the study area. The hydrochemical type of geothermal water is dominated by Cl·SO4-Na, which is mainly influenced by dissolution of halides, chlorides and sulfates under strong fluid-rock interactions. The isotope analysis demonstrated that the atmospheric precipitation in the Helan Mountain area is the major recharge source of geothermal water, the recharge elevation is 1118 m–1133 m, and the deep geothermal water is formed by a mixing process of ancient precipitation and modern precipitation. The silica-enthalpy mixing model suggested that the reservoir temperature of deep geothermal fluid is between 110 °C and 175 °C, and the mixing ratio of cold water is about 54 % to 92 %. The present study sheds some light on the genesis, recharge mechanism and hydrogeochemical evolution of geothermal water in deep aquifers, which are vital for sustainable exploitation and utilization of geothermal resources.

Limestone water mixing process and hydrogen and oxygen stable isotope fractionation response under mining action

North China type coalfield are gradually mining deep, and the mixing of groundwater is intensified. Hydrogen and oxygen isotopes are important elements for tracing groundwater movement. The fractionation response mechanism under mining conditions is not clear. In this paper, combined with numerical simulation, MixSIAR isotope mixing model and other methods, according to the δD, δ18O and hydrochemical information of various water bodies, the impact of coal mining on hydrogen and oxygen isotope fractionation is analyzed from multiple perspectives. The results show that summer soil water is the main source of recharge for limestone water, accounting for 30.7%–41.5%, and the Zhan River is the main source of recharge for limestone water. Before groundwater recharge, evaporation leads to the increase of δ18O in surface water by 0.31‰–5.58‰, water loss by 1.81%–28.00%, the increase of δ18O in soil water by 0.47‰–6.33‰, and water loss by 2.74%–35.80%. Compared with the coal mining layer, the degree of hydrogen and oxygen isotope drift and water-rock interaction in the coal mine stopping layer are significantly improved. The results of numerical simulation show that the pumping activity reduces the 18O concentration in the mining layer. The ion ratio is used as a new variable to eliminate the influence of water-rock interaction when calculating the mixing ratio. The results show that the limestone water is in a state of receiving external recharge, and mixing effect increases the δ18O in limestone water by 0.86‰ on average, and the δD increases by 0.72‰ on average. The research results explain the controlled process of hydrogen and oxygen isotope fractionation under mining conditions, which is of great significance to coal mine safety production.

Numerical Study on the Influence of Different Operating Conditions on Mixing Uniformity of the Helical Gear Pump Mixer

The uniformity of the gelatin solution and water mixing process is a critical factor in the performance of helical gear pump mixers that affects pump efficiency. In this study, we investigate the impact of water inlet velocity and rotational speed on the helical gear pump mixer. A numerical model of the helical gear pump mixer is established using Simerics MP+ 5.2.15 software. By varying the water inlet velocity from 0.159 m/s to 1.272 m/s and the rotational speed from 8 rpm to 50 rpm, we obtained volume fraction distributions of water in different sections of the helical gear pump mixer. The simulation results show that the high water inlet velocity causes the water and gelatin solution in the mixing tank to not mix fully. When the inlet speed is 0.318 m/s, the mixing uniformity of the gelatin solution and water in the mixing tank is effectively promoted, and the maximum volume fraction of water in the water-rich region is reduced by 70.24%. In poor water regions, the maximum volume fraction of water increased by 9.25 times. Furthermore, within a certain range, increasing the rotational speed of the helical gear pump promotes the faster transport of water to the back of the mixing tank, leading to reduced non-uniformity in the gelatin solution and water mixing process. These findings provide valuable insights for enhancing mixing uniformity in helical gear pump mixers.

Coupling major ions and trace elements to turbidity dynamics for allogenic contribution assessment in a binary karst system (Sierra de Ubrique, S Spain)

This investigation deals with the application of a multi-technique approach combining data from turbidity, major ions, and trace elements to characterize the implications of allogenic recharge in a binary karst system and assess the relative hydrochemical contribution to karst springs captured for drinking use. Hydrodynamic and hydrochemical responses of the outlets to storm events were continuously monitored during four selected flooding events, and water samples were collected at the main sinking stream in the recharge area and discharge points (Cornicabra and Algarrobal springs) for chemical analysis. The obtained hydrogeochemical dataset was analyzed through mean of time-series and statistical analysis and allowed to describe the fate and origin of trace elements. Despite that most of analyzed components present a natural origin, the existence of a Wastewater Treatment Plant in the recharge area was determined to be the main source of P (phosphorus) concentrations measured in the karst springs. Sediment (particulate) transport constitutes the most important factor in the mobilization of Al, Mn, Ni, and Ba in both surface and groundwater, whilst Li, Sr, and P are mainly controlled by solute migration. The hydrochemical signature of allogenic water component was constrained by identifying characteristic correlations between Ba and Ca/Sr ratio in water samples. The combination of specific hydrogeological processes as ion solution and sorption processes onto solids between solutes and particles as well as water mixing processes (allogenic vs diffuse) result more evident in Algarrobal spring, which receives a higher contribution of allogenic component due to a greater feeding catchment.

Water mixing processes in a complex multi-layer hydrosystem in southwestern Madagascar: a combined isotopic and piezometry approach

Water transfers through a multilayered aquifer system are difficult to characterize. This study explores whether the conceptual model of water mixing at depth can be extrapolated over a hydrosystem extended across several tens of kilometers and including multiple aquifer layers. The processes are investigated using a combination of isotope tracers and piezometric monitoring over 10 years. The goal of this approach is to better understand how water transfer occurs throughout a complex and poorly documented hydrosystem of the Mahafaly Plateau in southwestern Madagascar. The results show a clear smoothing of isotopic variability with depth, associated with a smoothing of the recharge peaks. Isotopic values are strongly variable in the near surface (from -6.8 to -2.5‰ 18O) and stabilize at a critical depth (near 20 m) at around -4.7‰ 18O. These results indicate high vertical flows through the aquifer system, where there is neither obvious dominant recharge via preferential pathways nor lateral mixing. Such a strong smoothing effect on groundwater isotopic variability with depth has been rarely observed so clearly over a large spatial scale. These results provide information on a remote groundwater flow system at a scale pertinent to groundwater resource assessment. The results also indicate that the Neogene aquifers of the Mahafaly Plateau are poorly connected with other water resources (rivers, old sedimentary formations) except for the percolation of water towards the deep Eocene karst. This means that groundwater resources in the Ankazomanga Basin are limited and that it is essential to understand and quantify recharge for sustainable groundwater management.

Seconds-Scale Response Sensor for In Situ Oceanic Carbon Dioxide Detection

Research on the transient variation processes of oceanic dissolved CO2 makes significant sense because of the complexity and dynamics of the marine environment. Yet, it is inherently challenging due to the limitation of the response performance of in situ sensors. Here, we report a novel system solution capable of providing high-performance detection with a seconds-scale response, sub-ppmv level precision, and 3000 m rated depth. Through the proposed strategy, we break the limitation of the membrane on the response performance of the sensor and improve it by 2 orders of magnitude to the τ100 of 3.5 s (τ90 = 2.7 s). By taking water temperature and CO2 concentration as the tracer, we succeed in portraying the water mixing process and reveal the microstructure of the concentration variation profile. By enabling in situ detection at an unprecedented response speed, this instrument can provide new insights and prospects into the research on the carbon cycle in deep-sea unstable regions, such as hydrothermal vents and cold seeps.

Disentangling runoff generation mechanisms: Combining isotope tracing with integrated surface/subsurface simulation

The majority of runoff studies to date have reported a similar pattern of rapid rain-to-runoff conversion via overland flow and shallow subsurface water flow, as well as the ubiquity of thresholds and hysteresis in rainfall-runoff response. But each of those approaches has limitations in terms of inference and process description. Processes of water transport and mixing and how they influence runoff generation are still not well understood or quantified. In this study, HydroGeoSphere, a fully-integrated surface/subsurface flow model, was used together with stable isotopes for disentangling runoff generation mechanisms in a headwater catchment. The study area (0.21 km2) is the first-level tributary of the Xin’an Jiang River located in a humid climate region of eastern China. Water flow simulation elucidated the spatial water transport process, and isotope tracing quantified the complex water mixing process between the shallow soil and hillslope surface. This study provides insights into the rapid transformation of rainfall infiltration and mixing in soil and exfiltration to a hillslope. Results show that the stream runoff was separated into rainfall-induced overland flow (9 %), exfiltration-induced overland flow (including the 53 % of mixed water from rainfall infiltration and 6 % of the stored soil water), and subsurface flow (32 %). Exfiltration-induced overland flow was the dominant water source in the headwater catchment during a rainfall-runoff event. The mutual influence of rainfall infiltration and soil water exfiltration caused the shallow soil to rapidly become saturated, thus forming saturation excess overland flow. The consistence of estimated soil water velocity based on the integrated isotope and numerical modeling approach, at about 0.4 m/d nearby the stream channel, improved the reliability of model visualizations. Further analysis indicates that water flow paths and velocities responding to the rainfall event were attributed to the soil moisture conditions and topography. This study demonstrates that identifying the rapid mixing processes between the rain and the soil water was crucial for understanding hillslope overland flow and runoff generation in headwater catchments.

Identifying soil water movement and water sources of subsurface flow at a hillslope using stable isotope technique

Knowledge concerning soil water movement and water sources of subsurface flow is crucial for understanding runoff generation mechanisms and nutrient-pollution migration. Although the spatiotemporal characteristics of soil water have been confirmed, water sources of subsurface flow during rainfall remain poorly understood at the hillslope scale. We measured the δ18O and δ2H in soil water before and after storm events to explore the mixing process of new water (rainwater) and old water (pre-event soil water) at the hillslopes with different farming practices (bare land, no-tillage and straw mulching). Water source partitioning of subsurface flow during three storms (April 11, April 24, June 10) were quantified using the MixSIAR model. The results showed that both preferential flow and piston flow existed in the process of soil water movement which were detected by the variation in the isotopic values of soil water after storms. The proportional contributions of new water to subsurface flow from 0 − 30 cm in no-tillage plot was the highest (46.60%) among experimental plots. The fraction of new water to subsurface flow for no-tillage, bare land, and straw mulching plot was 27.36%, 22.39%, and 16.28%, respectively, indicating that farming practices affected water source partitioning of subsurface flow. The average proportion of old water to subsurface flow of 0 − 30 cm, 30 − 60 cm and 60 − 90 cm during three storm events were 71.77%, 76.72%, and 87.48%, respectively, suggesting that subsurface flow was mainly derived from old water with soil depths specific responses. In addition, the proportional contributions of new water to subsurface flow varied dynamically with the progress of rainfall, implying that the mixing between new and old water affected water sources of subsurface flow. These findings have crucial implications for understanding the generation mechanisms of subsurface flow and the sustainable management of agro-environmental systems.

Estimation of sea surface pCO2 and air–sea CO2 flux in the East China Sea using in-situ and satellite data over the period 2000–2016

The partial pressure of carbon dioxide (pCO2) is an important variable to characterize the state of the seawater carbonate system. It is required to calculate the air-sea CO2 flux (FCO2) and for understanding ocean acidification. Surface ocean pCO2 is influenced by thermodynamic process, physical mixing, biological activity and air-sea gas exchange. Knowledge of the surface pCO2 in the East China Sea (ECS) is limited due to a lack of observations and well-informed models. This study employed in situ hydrographic (sea surface temperature and salinity) and carbonate system observations combined with satellite observations of chlorophyll a to develop a regional multiple non-linear regression (MNR) model to estimate pCO2 for three different physical-biogeochemical domains of the ECS. Comparison of the pCO2 from in situ observations with the MNR model had a root mean square error (RMSE) of 45.19 μatm and coefficient of determination (R2) of 0.87 in the transitional domain, an RMSE of 11.59 μatm and R2 of 0.92 in the shelf-dominated domain and an RMSE of 3.73 μatm and R2 of 0.97 in the open water domain. The reliability of the MNR model was also validated using an independent dataset with a good accuracy (RMSE of 9.15 μatm for domain II and RMSE of 7.71 μatm for domain III). The MNR model was applied to estimate the surface pCO2 and FCO2 for ten cruises on the period of 2013–2018, and also used to predict monthly surface pCO2 by using Changjiang Biology Finite-Volume Coastal Ocean Model (FVCOM) outputs for the period of 2000–2016 on the ECS inner shelf, and analyzed the seasonal and interannual variability of surface pCO2 and FCO2. The seasonal dynamics of sea surface pCO2 were mainly attributed to temperature changes, biological activities and water mixing process over the seasons. The time series of surface pCO2 and FCO2 on the ECS inner shelf showed an increasing trend of 3.32 ± 0.79 μatm yr−1 and 0.018 ± 0.0125 mol CO2 m−2 yr−2, and the region was a CO2 sink with an CO2 uptake of 0.12 ± 0.48 Tg C yr−1.

Effects of Water and Fertilizer Flow Rates on the Mixing Process and Fertilization Uniformity of Cotton under Mulch Drip Irrigation

Water and fertilizer flow rates are the most convenient variable to control in the process of drip irrigation under mulch. Suitable water and fertilizer flow rates are beneficial to improve water and fertilizer uniformity. Nine groups of water and fertilizer rate combinations were set in the common water and fertilizer rate range to study the influence of the water and fertilizer rate on fertilization uniformity. The numerical simulation of the mixing process in the main pipe was first carried out based on the multiphase flow theory, and then the field experiment for the different water and fertilizer rate combinations in the machine-picked cotton-planting pattern (one film, three tubes and six rows) was conducted. Through the numerical simulation of the mixing process in the pipeline and the analysis of water and fertilizer uniformity field experiment results, it was found that the uniform mixing length is related to the water and fertilizer flow rate, and the water and fertilizer flow rate had some effect on fertilizer uniformity. In the irrigation system with a main pipe diameter of 100 mm and a fertilizer injection pipe diameter of 20 mm, the water fertilizer flow rate ratio should be between 3–8 to ensure the effect of the mixing process and fertilization uniformity. A water flow rate of 2 m s−1 and fertilizer flow rate of 0.35 m s−1 is recommended during the fertilizer process in northern Xinjiang. This paper shows the feasibility of numerical simulation in the study of cotton water and fertilizer mixing processes, and the results can provide some reference for cotton planting.

Hydrochemistry of the Mixed Dead Sea-Red Sea Water under Different Impoundment Scenarios as a Time Dependent State

The expected water mixing process between Red/Dead Sea water during the proposed conveyance projects is the main target of this research. The project will ensue transporting Red Sea water to recover and maintain certain level of the Dead Sea, mostly will reach -395 m. It is found that, the two different water bodies with different EC values or different densities (salinities) are relatively divided by stable plane. This plane is defined as the BARZACH PLANE. In this study, the mixing process occurred between the Red Sea with the Dead Sea waters, located at 20% - 24% of the Dead Sea column depth based on the Barzach Plane level. During a laboratory experimental work, it is found that the mixed Red/Dead Sea water evaporates in a high rate until certain level where the solution attains oversaturated conditions with different dissolved solids. At this stage, a thin layer of solids suddenly formed and floated at the surface of the dense brine. The salinity of the captured water is so dense that floated salt layer cannot be dissolved. In addition, the formed floated salt layer at the surface prevents the below captured water to evaporate and at this stage, stalactites start to form until the excess dissolved solids are not oversaturated with any mineral.

Alternative Use of Artificial Quarry Lakes as a Source of Thermal Energy for Greenhouses

In northern Italy, most greenhouses rely on gas or oil heaters which are sometimes subject to high operating costs. Several greenhouses are nearby quarry lakes, which are the legacy of the expansion of cities in the last decades, including Turin (NW Italy). About 20 quarry lakes were excavated close to the Po riverbed in the southern part of this urban area, along a belt of more than 30 km in length, with an overall volume exceeding 10 million m3 water. The study addresses these artificial lakes as a low enthalpy thermal energy source, potentially providing heat to surrounding agri-business buildings. Detailed temperature monitoring of a large lake quarry was conducted over two years at different depths, measuring the surrounding groundwater level as well. Two different behaviors of the lake during the winter and summer seasons enabled the definition of a quite low water mixing process between the surrounding aquifers and the lake (in the range of 2–4 °C). An evaluation of the heat extraction potential using the lake as a heat source, depending on water temperature and its volume, and a qualitative comparison with groundwater systems are proposed. This study contributes to increasing knowledge on an overlooked resource for sustainable heating.

Characteristics of raw water sources and analysis of the optimal model of the mixing process with parameter design in clean water pump installations

The quality characteristics of raw water sources in the regional integrated drinking water supply system (SPAM) of Banjarbakula were investigated and found to maintain the supply of drinking water quantity and quality in accordance with drinking water standards. The optimum model for the mixing process of raw water and poly aluminum chloride (PAC) and pump stroke for the input of water sources from rivers to obtain a composition setting that is in accordance with the raw water sources of each region in the region was selected and determined. So the optimum parameter setting model between alum water, raw water and pump stroke for each raw water source is known and is regionally integrated as a result of a comprehensive study. The integration of Taguchi parameter design and response surface can complement each other and become two methods that go hand in hand in the process of optimizing clean water products. Parameter design provides a very practical optimization step, the basis for this formation refers to the factorial fractional experimental design. However, the absence of statistical assumptions that follow the stages of analysis makes this method widely chosen by researchers and practitioners. With the experimental design of the raw water mixing process, turbidity such as 5 lt/sec, 10 lt/sec, 15 lt/sec, 20 lt/sec and 25 lt/sec and % PAC concentration 5 ppm, 10 ppm, 15 ppm, 20 ppm and 25 ppm with a pump installation stroke of 5 %, 10 %, 15 %, 20 % and 25 % were used. In the process of adding PAC, always pay attention and observe the behavior of the attractive force of the floating particles (flock). The particles were then subjected to SEM (scanning electron microscopy) to determine the dimensions of the flock grains deposited

Realization of Accurate Modeling and Simulation of Oilfield Water Mixing Gathering and Transportation System

In order to solve the shortcomings that the simulation accuracy of oilfield water mixing gathering and transportation system is not high, the dual-process of mixing water and returning to the station cannot be realized at the same time, the system is accurately modeled, and the data structure and computer model suitable for calculation are established by reading static data. The design modeling software realizes the logical and data interface and realizes the display of the physical model on the computer. Based on the quasi-Newton loop iteration method, an online algorithm is proposed. Using the flow rate of each node of the system as the constraint condition, the water mixing process node and pipeline parameters are calculated. According to the calculation results and the oil well produced fluid parameters, the principle of mixed calorimetry is applied to construct the initial value and iterative formula of the return flow simulation. The temperature at the return station is consistent with the inlet temperature of the heating furnace at the joint station. It can dynamically reflect the production and operation status of the water mixing system, and provide a scientific basis for the control and operation of the water mixing system.

Temperature and water level control in a multi-input, multi-output process using neuro-fuzzy controller

In this research, a simulation study for temperature and level control in a liquid (water) mixing process is proposed using MATLAB/Simulink. The objective of this control system is to maintain the temperature and water level at the set points in a liquid mixing process by controlling the flowrate of cold and hot water that enters the mixing tank. The mixing tank used in this study is assumed to have a volume of 80 liter, while the maximum flowrates of both water inputs are 15 liter/min, and the maximum temperature and level in the mixing tank are 90 C and 75 cm, respectively. The influence of one variable to the other is reduced using decoupling technique. In the development process of the controller, PI controller is used to generate the training data required by the ANFIS-based controller. The performance of the proposed controllers has been tested with several set points changes by observing its performances parameters, such as RMSE, rise time, settling time, and % overshoot as quantitative data. It also has been compared with a PI controller using the same set point changes as the ANFIS-based controller did. These results show that the ANFIS-based controller is generally better than the PI controller. It has the average RMSE values of 0.174 and 0.196 for temperature and level control respectively, while the PI controller has 0.21 and 0.20 average RMSE values for temperature and level control.

Coupling Mineralogical Analyses, Leaching Tests and Kinetic Modelling to Unravel Groundwater Flow-Paths in a Complex Landslide: An Attempt from the Vedriano Case Study (Northern Italian Apennines)

As the rise in pore water pressure is one of the main factors in triggering landslides, the understanding of groundwater processes taking place at the hillslope scale is a crucial issue in slope stability analysis. However, identifying flow-paths travelled by water molecules from their infiltration is still a complex task. Hydrochemistry is recognized as a powerful tool that can help to gain useful hydrogeological information and has gradually become increasingly used in addition to conventional study methods. This manuscript presents a comprehensive geochemical investigation consisting of leaching tests and quantitative mineralogical analyses on soil samples, chemical analyses on groundwater samples and modelling. Our results highlighted the usefulness of coupling, even in hydrogeological studies focusing on landslides, geochemical surveys on both water and the soil matrix to constrain the interactions between host-rocks and groundwater. Moreover, it demonstrated that kinetic-based geochemical models, if properly calibrated on leaching tests, can provide valuable information on groundwater dynamics, allowing us to elucidate water-mixing processes beneath the soil surface.

Mixing processes of autogenic and allogenic waters in a large karst aquifer on the edge of a sedimentary basin (Causses du Quercy, France)

On the edge of sedimentary basins, karst aquifers can be fed by several water origins from both autogenic and allogenic recharge. In some cases, water origin assessment is difficult and issues in water management may arise. The main goal of this study is to understand what controls hydrodynamical and geochemical variations at the outflow of a quite complex and large karst system. More precisely, this study illustrates how a consistent observational setup can be developed, based on a multi-proxy approach that can be used for tracing water origins, evaluating mixing phenomena, and contributions in karst aquifers considering both autogenic and allogenic recharge.The Ouysse karst system (650 km2), located in western France, provides the opportunity of studying water-mixing processes in binary karst systems fed by allogenic and autogenic recharges. Global water chemistry, hydrograph and chemograph analysis during a flood event, and source-mixing calculation were used to evaluate groundwater-flow origins and the contribution of each water type during the studied flood event: (i) karstic water; (ii) evaporite water; (iii) water from igneous-metamorphic rock aquifers.In terms of resource management, the information obtained can be used as a basis of forecasting and management actions.

Deep carbon degassing in the Matese massif chain (Southern Italy) inferred by geochemical and isotopic data.

The Italian Apennines are among the most important sources of freshwater for several Italian regions. With evidences of deep CO2-rich fluids intruding into aquifers in the nearby central-southern Apennines, a thorough investigation into the geochemistry of groundwater became critical to ensure the water quality in the area. Here, we show the main hydrogeochemical processes occurring in the Matese Massif (MM) aquifer through the investigation of 98 water samples collected from springs and water wells. All waters were classified as HCO3 type with Ca dominance (from 50% up to 97%) and variable amount of Mg (from 1% up to 49%). A multivariate statistical approach through the application of the factor analysis (FA) highlighted three main hydrogeochemical processes: (i) water-carbonate rock interactions mostly enhanced in peripheral areas of the MM by CO2 deep degassing; (ii) addition of NaCl-rich components linked to recharging process and to water mixing processes of the groundwater with a thermal component relatively rich in Cl, Na, and CO2; (iii) anthropogenic activities influencing groundwater composition at the foothills of MM. Furthermore, the first detailed TDIC, pCO2, and δ13C-TDIC distribution maps of the MM area have been created, which track chemical and isotopic anomalies in several peripheral areas (Pratella, Ailano, and Telese) throughout the region. These maps systematically highlight that the greater the amount of dissolved carbon occurs the heavier the C isotope enrichment, especially in the peripheral areas. Conversely, spring waters emerging at higher altitudes within MM are only slightly mineralized and associated with δ13C-TDIC values mainly characterized by recharging processes with the addition of biogenic carbon during the infiltration process through the soil.

Distributing PID controllers applied in water-mixing process

In a process control system influenced by several parameters, which are usually located and separated in a large area, the one-central controller is not effective anymore. It is computationally hard for the controller hardware to do many tasks at the same time, therefore, they are considered to distribute in Local Control Units (LCUs). This research investigates the distributed PID controllers in the water-mixing process. The main controlled variables (SVG) are the level and temperature influenced by three parameters (flow-in of cold water, flow-in of hot water, and flow-out of the main tank), which are then distributed to LCU-1 to LCU-3. To maintain the SVG, the master controller is then designed based on the difference between SVG and feedback of the main-tank (PVG) so that it will deliver SV for each LCU. The results show that with control parameters in LCU-1 (Kp, Ti, Td are 2, 10, 0.46, respectively), LCU-2 (Kp, Ti, Td are 8, 6, 0.6), and LCU-3 (Kp, Ti, Td are 3, 70, 20), the response of water temperature (measured based on settling-time [Ts], % overshoot [OS], and rise-time [Tr]) are 42s, 0%, 45.3s. In the water level control, the response can be maintained with the 60s, 0%, 62s, for Ts, %OS, Tr, respectively.