Saturation Depth Research Articles

Research of natural remediation of the subsurface contaminated with petroleum products

Remediation of the subsurface contaminated with petroleum products is the ecological problem on a world scale and a foreground direction of geoecological research in Ukraine. Remediation of contaminated vadose zone can be provided with the activity of microorganisms, mainly micromycets, whose features of location and vital activity depend on a depth, the level of contamination, aerobic conditions, etc. Practically, it is complicated to use artificial microbiological methods and natural remediation of contaminated subsurface due to microorganisms should be taken into consideration. Microorganisms oxidizing hydrocarbons are of particular interest. Field investigations were carried out within the fuel storage of the Boryspil airport where subsurface contamination with petroleum products was revealed in 1998. The research included sampling at contaminated and uncontaminated sites, quality analysis of petroleum product contains in soils and determination of the species composition of micromycets. Soil samples were taken in three wells at different depths – in the center of the contamination source at the depths of 0,1 m and 2,0 m (unsaturated zone) and 4,0 m (saturated zone), in the northern part of the fuel storage in the unsaturated zone at the depths of 0,1 m and 1,0 m, and out of the contamination source in the unsaturated zone at the depth of 3,7 m. Fungus culture determination data in soil samples indicate that variety of their forms depends on a contamination degree, a depth of sampling, lithology and water saturation. Regular monitoring should be carried out including soil sampling and determination of petroleum product contains to specify conclusions about natural remediation of contaminated soils due to life activity of microorganisms oxidizing hydrocarbons.

Dynamics of the Carbonate System Across the Peruvian Oxygen Minimum Zone

The oxygen minimum zone (OMZ) of Peru is recognized as a source of CO2 to the atmosphere due to upwelling that brings water with high concentrations of dissolved inorganic carbon (DIC) to the surface. However, the influence of OMZ dynamics on the carbonate system remains poorly understood given a lack of direct observations. This study examines the influence of a coastal Eastern South Pacific OMZ on carbonate system dynamics based on a multidisciplinary cruise that took place in 2014. During the cruise, onboard DIC and pH measurements were used to estimate pCO2 and to calculate the calcium carbonate saturation state (Ω aragonite and calcite). South of Chimbote (9oS), water stratification decreased and both the oxycline and carbocline moved from 150 m depth to 20-50 m below the surface. The aragonite saturation depth was observed to be close to 50 m. However, values less than 1.2 were detected close to 20 m along with low pH (minimum of 7.5), high pCO2 (maximum 1250 μatm), and high DIC concentrations (maximum 2300 μmol kg-1). These chemical characteristics are shown to be associated with Equatorial Subsurface Water (ESSW). Large spatial variability in surface values was also found. Part of this variability can be attributed to the influence of mesoscale eddies, which can modify the distribution of biogeochemical variables, such as the aragonite saturation horizon, in response to shallower (cyclonic eddies) or deeper (anticyclonic eddies) thermoclines. The analysis of a 21-year (1993-2014) data set of mean sea surface level anomalies (SSHa) derived from altimetry data indicated that a large variance associated with interannual timescales was present near the coast. However, 2014 was characterized by weak Kelvin activity, and physical forcing was more associated with eddy activity. Mesoscale activity modulates the position of the upper boundary of ESSW, which is associated with high DIC and influences the carbocline and aragonite saturation depths. Weighing the relative importance of each individual signal results in a better understanding of the biogeochemical processes present in the area.

Investigating the Effect of Different Hydraulic Cross Sections of Denitrification Beds on the Amount of Effluent EC

Nitrate loadings from agricultural drainage to surface water resources cause’s serious water quality concerns in many parts of the world. Denitrification bioreactors are suitable option for removing nitrate from agricultural drainage water. The objectives of this study was to investigate the effect of different hydraulic cross sections of denitrification beds on the amount of effluent EC. In this study, three denitrification beds were constructed with a semicircular, triangle and a rectangle cross sections, filled with wood chips of beech tree. Samples were taken from the outlets of all three beds at a depth at 25 and 50 cm from the bottom of the bed for two months. EC of the samples was meassured using EC-meter. After determining the EC of the samples, data were analyzed by T-test and Univariate tests. The results showed that the shape of the cross-section of the denitrification beds and the saturation depth had a significant effect on EC and the amount of EC of the outflow was increased.

Analysis of the impact of hydraulic properties and climate change on estimations of borehole yields

Understanding the impact of climate change on borehole yields from fractured aquifers is essential for future water resources planning and management. Although variation in hydraulic conductivity with depth (VKD) in fractured aquifers is a well-known phenomenon, the relative significance of climate change and VKD on borehole yield estimates is poorly understood. We hypothesize that VKD exerts a significant additional control on borehole yields under climate change that has not been considered in yield assessments to date. We developed a simple two-layered radial groundwater flow model of an idealised pumping borehole in the fractured Chalk aquifer of south-east England, and applied 11 VKD profiles based on a simple conceptual representation of variation in hydraulic conductivity with depth in the Chalk. For each time step, the transmissivity is calculated by integrating the VKD profile over the saturated depth calculated at the previous time step. For each VKD profile and resulting transmissivity, we applied 20 climate scenarios and six constant pumping rates for the period 1962–2014. We then estimated borehole yields based on the derived lowest pumping water levels during key drought years (e.g. 1976). We show that the hydraulic properties of the aquifer are more significant (p < 0.001) than changes in climate (p > 0.1) in controlling lowest pumping groundwater levels when abstraction rates are <9000 m3/day, and that both are significant when abstraction ≥9000 m3/day. Hydraulic conductivity is as significant a control as climate on borehole yields, although responses are non-linear associated with whether pumping water level-pumping rate curves intersect key yield constraints (e.g. pump intake depth, major inflow horizons). It is recommended that variations in hydraulic conductivity with depth are taken into consideration in future assessments of borehole yields under climate change. The approach presented is generic and can be applied across different aquifers where vertical heterogeneity is present and affects transmissivity.

Analysis of Landslide Risk Distribution Pattern under Extreme Precipitation

This study analyzed the landslide risk in Ulsan, Korea using infinite slope stability analysis considering rainfall infiltration in the soil layer. The parameters used in the analysis were obtained by geographic information system (GIS) and field survey using the following parameter values: a cohesion of 30.84 kPa, unit weight of 1.46 t/m3, specific gravity of 2.65, effective soil depth of 0.41 m, and internal friction of 27.15°. The rainfall intensity was set to last for 60 min at a 10-year frequency of 57.8 mm/h, 50-year frequency of 78.5 mm/h, 100-year frequency of 87.3 mm/h, and 500-year frequency of 107.5 mm/h. The minimum safety factor for the landslide risk was set at 1.3, according to the slope design criterion of construction slope announced by Korea's Ministry of Land, Infrastructure, and Transport. The safety factors with the values of 0-1.3 have been classified into four grades based on the saturation depth ratio varying with the rainfall intensity. The higher the rainfall intensity, the higher the percentage of the first grade (very dangerous) area. For verification, the landslide risk area proposed in this study was compared with the ‘Landslide Risk Map’ provided by Korea Forest Service. It is expected that high accuracy could be achieved in future by increasing the field survey data. Keywords: Infinite Slope Stability Analysis, Rainfall Infiltration, Landslide, Wetting Front

An Intelligent Model for Estimating Relative Permeability in the Abu-Sennan Oil and Gas Fields, Southwestern Egypt

Permeability is arguably the most critical vector flow parameter used in the analysis of hydrocarbon formations. Permeability data are usually obtained from well shut-in tests and core investigations; however, only a small number of wells have well tests or core measurements. In contrast, well logs are often available for most wells in a field. Therefore, techniques that evaluate relative permeability using well logs can be extremely useful. To this end, an effective and thorough model composed of a radial base function neural network has been constructed to predict the relative permeability of formations within the Abu-Sennan Oil and Gas Fields. A total of 105 previously reported relative permeability core data points scattered along the Abu-Sennan Fields were used to construct and evaluate the proposed model. Input parameters for the neural network were wettability, water saturation, irreducible water saturation, porosity and sample depth. The results of the proposed model were compared to reported field data. The results illustrate that the proposed model is able to predict the relative permeability of specific units within the Abu-Sennan Fields with a high correlation coefficient for unnamed data in the model. The proposed model was assessed using sensitivity analysis based on the input parameters.

Organic matter and nutrients removal in hybrid constructed wetlands: Influence of saturation

Three hybrid wetland systems were studied for organics and nutrients removal from synthetic wastewater recipe. Each system included a vertical flow (VF) followed by a horizontal flow (HF) wetland. The wetlands were filled with common and unconventional media (gravel, biochar and sand) with different saturation and water depth ratio. Input N, P and COD loadings ranged between 48–145, 1–7 and 56–191 g/m2 d, respectively across first stage VF wetlands. Recalcitrant compounds of synthetic recipe reduced organics removals in VF wetlands. NH4-N adsorption and carbon leaching properties of biochar triggered N removals (19–102 g/m2 d) in partially saturated VF wetlands. Carbon unavailability influenced N removals in gravel based unsaturated VF wetland. Input N load increment reduced nitrification and NH4-N adsorption in VF wetlands. However, such increment improved N removal percentages in shallow water depth second stage HF wetlands, primarily due to removals in previous stages and atmospheric oxygen transfer via unsaturated zone; HF wetland with deep water depth showed opposite removal trend. P removal in experimental wetlands was achieved via media based adsorption; decrease of P concentration in synthetic recipe enhanced removals. N and P contents percentage (with respect to total removal) in plants ranged between 1 and 7% (VF), 5–17% (HF) and 2–36% (VF), 23–35% (HF), respectively, indicating dominance of microbial transformation and media based adsorption on observed removals. Partially saturated-shallow water depth hybrid wetland systems achieved ≥90% BOD, ≥97% N and 100% P removals. This study signifies potential application of partially saturated-shallow water depth hybrid wetland systems packed with unconventional media for wastewater treatment.

Soil Health Assessment Methods and Relationship with Wheat Yield

Soil quality assessment methods, based on different attributes, are available but not well calibrated/validated for subsequent operational applications. We have developed a method for soil quality index assessment by considering soil texture, organic carbon, pH, available water, cation exchange capacity, bulk density, total porosity, saturated hydraulic conductivity, salinity, aggregate stability, slope and soil depth. The scoring was done on 0 - 100 scale and the lowest score was assigned to the most limiting factor of crop growth and development. Attribute-wise rating was made by using Macros developed in MS-Excel and IDRISI3.2 was used to delineate the rating maps. About 64.6% soils scored more than 60 and the best soil group (score > 70) was only about 15%. Soil health score, as determined through our method, showed good relationship with wheat yield. Multiplicative response function was more sensitive than simple regression model. The correlation analyses with one or two attributes with most severe stress and relatively with lower rating values showed better predictability of wheat yields. The soil quality index as estimated from principal component analysis having strongly loaded (>0.75) factors showed inferior correlation with grain yields of wheat than geometric mean approach. It is concluded that geometric mean approach for soil health scoring can be utilized in similar environments around the globe with or without further improvement.

Capillary-based method for rock typing in transition zone of carbonate reservoirs

Reservoir simulation is established as a good practice to make the best decision for a petroleum reservoir. The reservoir is characterized in terms of reservoir elements such as structural model, well data, rock and fluid properties. Then the reservoir model is enhanced through history matching and finally different prediction scenarios are tried to find the best plan for the reservoir understudy. The more accurate the reservoir is characterized, the faster and the more precisely the history match is finished and the more reliable predictions are obtained. The most important part of reservoir characterization is the rock typing, where the quality of CCAL (conventional core analysis) and SCAL (special core analysis) properties are evaluated and estimated for any simulation grid. The resulting oil in place must be confirmed by the OOIP (original oil in place) calculated based on average petro-physical parameters for any layer. To allocate different rock types to simulation grid, rock types should be assigned according to different ranges of rock differentiation parameter which has to be determined in any specific study. Based on our experience in Iranian carbonate reservoirs, most frequently irreducible water saturation is the rock differentiation parameter. In the oil zone, water saturation from log data is assumed to be the irreducible water saturation. Thus, the rock type is identified with no trouble. The problem arises in transition zone, where water saturation from log data is not equal to the irreducible water saturation of that rock. This study includes the observed variations in terms of water saturation data versus depth and how to assign rock types to the transition zone grids. The objective of the capillary-based method is to produce a water saturation map which honors laboratory data as well as the well log data and considers the depth so that it can handle the transition zone in a proper manner. In fact, novelty of this work is to explain how it is possible to consider log and capillary pressure data together so that the most accurate rock type is assigned to reservoir grids of the transition zone. Moreover, this method is consistent with equilibration method for initializing reservoir simulations. A procedure is presented for how to implement the capillary-based method in a stepwise manner. Once the proposed method is carried out, the initialized simulation model is consistent with all sources of data (core analysis and petro-physical data). In this procedure original oil in place calculated after the initialization for simulation is more accurate and can be cross-checked with volumetric calculation based on interpreted log data. Therefore, it is considered to facilitate subsequent stages of reservoir study, namely history match and prediction.

Mechanisms and feedbacks for evapotranspiration-induced salt accumulation and precipitation in an arid wetland of China

Salt dissolved in soil water is transported upward to the soil surface through capillary rise from shallow groundwater, leading to salt accumulation near the surface and salinization of wetlands in arid regions. However, it is not clear how the mechanism and feedback for evapotranspiration induces salt accumulation and precipitation. Here, we developed a model to simulate the transport of water, solutes, and heat, and measured the meteorological, hydrological, and hydraulic parameters of soil using field experiments to calibrate the model for riparian and saltmarsh wetlands in northwestern China. The results showed that the annual atmospheric precipitation averaged 125.3 ± 10.2 mm in two types of wetlands, the evapotranspiration, depth to the groundwater and soil salinity averaged 587.7 mm yr−1, 85.4 ± 5.4 cm and 29.80 g kg−1 in the riparian wetland, while 637.2 mmyr−1, 129.7 ± 15.1 cm and 63.64 g kg−1 in the saltmarsh wetland, respectively. We found that the flux of liquid water, flux of water vapor, salinity, and efflorescence had maximum values of 1.23 mm day−1, 0.22 mm day−1, 104.16 g kg−1, and 2.10 cm in the riparian wetland, respectively, versus 1.28 mm day−1, 0.32 mm day−1, 202.02 g kg−1, and 3.70 cm in the saltmarsh wetland. Our simulations show that the salinity increases significantly with increasing evapotranspiration, soil temperature, saturated water content, and groundwater depth in the saltmarsh wetland, but that the effects of saturated water content and groundwater depth were small in the riparian wetland. As a result of these factors, the efflorescence pattern exhibited characteristic seasonal and inter-annual variability in which complex interactions among atmospheric precipitation, evapotranspiration, groundwater, and river water provided the long-term driving forces for water flow and salt transport. We found that the increasing efflorescence disrupted evaporation more than subflorescence, which reduced the soil porosity and possibly affected water vapor transport.

AISI 5140 steel nitriding in a plasma of a non-self-sustaining arc discharge with a thermionic cathode under the pulse action of ions

Steel AISI 5140 was exposed to pulsed (50 kHz) low-energy (up to 1 kV) nitriding in the plasma of a non-self-sustained arc discharge with a hot hollow cathode in a pure nitrogen atmosphere. The aim was to investigate the effect of the ion energy (pulse amplitude) and ion current density on the nitride layer thickness and on the depth of diffusion saturation with nitrogen. Experiments were also performed to study the effect of the ion energy and ion current density on the efficiency of nitriding at a constant specimen temperature and constant process time.

Influence of saturated zone depth and vegetation on the performance of vertical flow-constructed wetland with continuous feeding.

The object of this study was to investigate the effect of saturated zone depth (SZD) and plant on the removal of organics and nitrogen in four continuous-feed vertical flow-constructed wetlands (VFCWs). Three VFCWs were planted with Iris pseudacorus and operated at different SZDs (19, 51, and 84cm), and the other one was non-planted and operated at 51cm SZD. The VFCWs were operated with an organic loading rate (OLR) of 79g chemical oxygen demand (COD)m-2day-1, a total nitrogen loading rate (NLR) of 11g Nm-2day-1, and a hydraulic loading rate (HLR) of 0.35m3m-2day-1. Simultaneous transformation of ammonium and nitrate occurred in all of the four systems. In the planted bed with 51cm SZD, suitable conditions for nitrification and denitrification could be created and the best performance for total nitrogen (TN) removal was realized via simultaneous nitrification and denitrification (SND), achieving TN removal efficiency of 67.4-80.3%. Higher ammonium nitrogen (NH4+-N) and COD removal efficiency was obtained in the system operated with 19cm SZD, whereas higher NO3--N removal could be achieved in the bed with 84cm SZD. With the same SZD of 51cm, the planted VFCW performed preferable removal of COD, NH4+-N, and TN in comparison with the non-planted one. All the VFCWs showed high removal efficiencies for total phosphorus (> 60.15%). Adsorption of phosphorus was primarily observed in the top and upper-middle layers filled with carbon burn slag. It has been proved that the partially saturated VFCW operated with continuous feed could achieve good performance in removal of organic matter and nitrogen by SZD adjustment to develop appropriate aerobic and anoxic regions.

Interannual and Seasonal Variations in Estuarine Water Quality

Anthropic processes degrade quality of estuarine environments, resulting in a worrying form of water pollution. The objective this study was to describe and discuss interannual and seasonal changes of water quality based on indicators monitored in Goiana River estuary, as well as identifying the main drivers of such changes. We considered three estuarine areas or habitats (upper estuary, middle estuary and lower estuary), and two seasons (dry and rainy) for anchoring sample design. The information collected for surface and bottom water include water temperature (°C), salinity, dissolved oxygen (mg L-1), saturation (%) and Secchi depth (cm) (n=864). The monthly total rainfall (mm) was compiled from public database. Multivariate analyses highlight inter dependency among these parameters. Water quality was reduced in dry periods (including episodes of hypoxia), but generally increased towards the mouth of estuary. Rainfall is the most important factor in the renewal and maintenance waters of small tropical estuaries. Regions most sensitive to climate change where water resources are depleted and/or compromised should pay even more attention to upcoming changes in rainfall (seasonal) and climatic patterns in addition to better water management practices.

Determination of saturation depth in Compton scattering using Artificial Neural Network

Determination of saturation depth in Compton scattering using Artificial Neural Network

New method for processing gamma backscattering spectra to estimate saturation depth and to determine thickness of aluminum and steel materials

In this study, we present a new gamma spectrum processing method is applied to analyze experimental scattering spectra on aluminum and steel for determining the intensity of the single scattering component. Based on these results, the saturation depth of aluminum and steel materials are 78.8 and 22.5 mm, respectively. The thickness of both materials is determined with a maximum relative deviation of about 7% in comparison with real thickness. Besides, the result also shows that we can use the new spectrum processing method, which is a simple, and useful solution to determine the material thickness, for NaI(Tl) detector and a low activity source.

Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania

Abstract. Biogeochemical change in the water masses of the Southern Ocean, south of Tasmania, was assessed for the 16-year period between 1995 and 2011 using data from four summer repeats of the WOCE–JGOFS–CLIVAR–GO-SHIP (Key et al., 2015; Olsen et al., 2016) SR03 hydrographic section (at ∼ 140° E). Changes in temperature, salinity, oxygen, and nutrients were used to disentangle the effect of solubility, biology, circulation and anthropogenic carbon (CANT) uptake on the variability of dissolved inorganic carbon (DIC) for eight water mass layers defined by neutral surfaces (γn). CANT was estimated using an improved back-calculation method. Warming (∼ 0.0352 ± 0.0170 °C yr−1) of Subtropical Central Water (STCW) and Antarctic Surface Water (AASW) layers decreased their gas solubility, and accordingly DIC concentrations increased less rapidly than expected from equilibration with rising atmospheric CO2 (∼ 0.86 ± 0.16 µmol kg−1 yr−1 versus ∼ 1 ± 0.12 µmol kg−1 yr−1). An increase in apparent oxygen utilisation (AOU) occurred in these layers due to either remineralisation of organic matter or intensification of upwelling. The range of estimates for the increases in CANT were 0.71 ± 0.08 to 0.93 ± 0.08 µmol kg−1 yr−1 for STCW and 0.35 ± 0.14 to 0.65 ± 0.21 µmol kg−1 yr−1 for AASW, with the lower values in each water mass obtained by assigning all the AOU change to remineralisation. DIC increases in the Sub-Antarctic Mode Water (SAMW, 1.10 ± 0.14 µmol kg−1 yr−1) and Antarctic Intermediate Water (AAIW, 0.40 ± 0.15 µmol kg−1 yr−1) layers were similar to the calculated CANT trends. For SAMW, the CANT increase tracked rising atmospheric CO2. As a consequence of the general DIC increase, decreases in total pH (pHT) and aragonite saturation (ΩAr) were found in most water masses, with the upper ocean and the SAMW layer presenting the largest trends for pHT decrease (∼ −0.0031 ± 0.0004 yr−1). DIC increases in deep and bottom layers (∼ 0.24 ± 0.04 µmol kg−1 yr−1) resulted from the advection of old deep waters to resupply increased upwelling, as corroborated by increasing silicate (∼ 0.21 ± 0.07 µmol kg−1 yr−1), which also reached the upper layers near the Antarctic Divergence (∼ 0.36 ± 0.06 µmol kg−1 yr−1) and was accompanied by an increase in salinity. The observed changes in DIC over the 16-year span caused a shoaling (∼ 340 m) of the aragonite saturation depth (ASD, ΩAr = 1) within Upper Circumpolar Deep Water that followed the upwelling path of this layer. From all our results, we conclude a scenario of increased transport of deep waters into the section and enhanced upwelling at high latitudes for the period between 1995 and 2011 linked to strong westerly winds. Although enhanced upwelling lowered the capacity of the AASW layer to uptake atmospheric CO2, it did not limit that of the newly forming SAMW and AAIW, which exhibited CANT storage rates (∼ 0.41 ± 0.20 mol m−2 yr−1) twice that of the upper layers.

Origin and Evolution of Silicic Magmas in Oceanic Arcs; an in situ Study from St Lucia, Lesser Antilles

Processes linked with the genesis, evolution and emplacement of silicic complexes in arcs are still poorly constrained. Of particular interest are the depth of magma production, the relative contribution of crystal fractionation versus crustal partial melting and the timescales involved. The Soufriere Volcanic Complex (SVC) on St Lucia is one of the largest silicic centres in the Lesser Antilles arc. Here we present the results of a detailed mineralogical study, including in situ Sr isotopes in plagioclase and in situ δ18O in dated zircons, of both SVC and Pre-SVC volcanic rocks to place constraints on the processes intrinsic to the development and evolution of the silicic complex. These data suggest that the production of silicic magma in the SVC occurs in two stages. The first stage involves differentiation of mafic magma by crustal assimilation and mineral fractionation in the middle–lower crust of the arc to produce magmas with intermediate compositions. These intermediate magmas are water-rich (∼7 wt %) and have high 87Sr/86Sr, Ba, Sr and La/Sm (∼5) compared with Pre-SVC lavas. Near-constant trace element and isotopic compositions throughout the SVC lifespan indicate that the same process was persistent over the last 600 kyr. In the second stage, the intermediate magmas are transferred to a shallower and more differentiated chamber (∼6 km depth). During ascent, any crystals or xenocrysts residual from stage one in the deeper chamber become fully resorbed and the magma crystallizes calcic amphibole microphenocrysts, followed by anorthite-rich plagioclase close to or at the water saturation depth. During mixing upon recharge within the shallow chamber, anorthite-rich plagioclase from the recharging magma is partially resorbed; so are the crystals in equilibrium with the resident differentiated magma. The recharge event probably causes chamber-wide convection. Mixing is thought to trigger eruption of the silicic complex magmas.

Calcite dissolution kinetics at the sediment-water interface in natural seawater

Abstract The absorption, or uptake, of anthropogenic CO 2 by the oceans results in a decrease in pH and carbonate ion concentration, [CO 3 2 − ]; as a consequence, the saturation state of seawater with respect to CaCO 3 minerals (calcite, aragonite) falls, leading to a shallowing of their saturation depths and triggering an increase in their dissolution at the seafloor. Nearly one-third of the seabed is composed of CaCO 3 -rich sediments, and their dissolution is the ultimate marine sink of anthropogenic CO 2 . Despite numerous past studies, much confusion and uncertainty still surround our understanding of the rates and kinetics of CaCO 3 dissolution at the deep seafloor. Results from in situ studies disagree with laboratory studies, most of which have been carried out under conditions, e.g., mineral suspensions, that are not representative of processes at the seafloor. Herein, we report measurements of the dissolution rate of calcite, formed into synthetic sediment disks by mixing various amounts of this mineral with montmorillonite. These disks were placed in a stirred-flow reactor and exposed to a range of saturation states and shear stress conditions to simulate conditions at the sediment-water interface. The dissolution rates, normalized to the interfacial area of the sediment disks, were linearly dependent on the undersaturation state of the experimental seawater solution and displayed a square-root dependence on the calcite content, under both quiescent and stirred conditions. The rate of release of reaction products from the sediment increased with stirring rate, i.e., shear stress, until it became invariant at higher stirring rates. This latter result argues that calcite dissolution is transport (water-side) controlled for shear stress levels known to exist at the seafloor, which advises a simpler kinetic description of benthic calcite dissolution.

MATHEMATICAL AND TECHNOLOGICAL MODELING FOR SOLVING OF PROBLEMS OF THE TECHNOLOGY OF CONSTRUCTION OF ENVELOPES FROM NO-FINE EXPANDED-CLAY CONCRETE IN A PERMANENT FORM

The article views the problems of construction of envelope structures from no-fi ne expanded-clay concrete in a permanent form made from cement-bonded boards and due to the complexity of the technological problems associated with the processes of mixing and laying of light concrete mixture into the form that are solved by methods of mathematical modeling. The main technological challenges in the construction of structures made of no-fi ne expanded-clay concrete are considered. Specifi c volumes of aggregates and cement glue and their mass are theoretically and numerically determined. Control parameters and functions are studied to calculate the saturation depth of the aggregate grains. The links of relative depth impregnation dR / R of eff ective porosity of diff erent structures are derived. The conclusions about further implementation of the models and their research are made.

Enhancement of the complete autotrophic nitrogen removal over nitrite process in a modified single-stage subsurface vertical flow constructed wetland: Effect of saturated zone depth

This study was conducted to explore enhancement of the complete autotrophic nitrogen removal over nitrite (CANON) process in a modified single-stage subsurface vertical flow constructed wetland (VSSF) with saturated zone, and nitrogen transformation pathways in the VSSF treating digested swine wastewater were investigated at four different saturated zone depths (SZDs). SZD significantly affected nitrogen transformation pathways in the VSSF throughout the experiment. As the SZD was 45cm, the CANON process was enhanced most effectively in the system owing to the notable enhancement of anammox. Correspondingly, the VSSF had the best TN removal performance [(76.74±7.30)%] and lower N2O emission flux [(3.50±0.22)mg·(m2·h)−1]. It could be concluded that autotrophic nitrogen removal via CANON process could become a primary route for nitrogen removal in the VSSF with optimized microenvironment that developed as a result of the appropriate SZD.