Average Specific Rate Research Articles

Thermodynamic analysis of anaerobic digestion of Eichornia crassipes (Water Hyacinth) biomass from the Volta River basin of Ghana using fruit waste sludge as inoculum

In order to gain understanding on the utilization of biogas fuel derived from water hyacinth (WH) biomass and render it appealing as a sustainable gaseous fuel, the study reports on its various thermophysical, combustion and thermodynamic parameters. The parameters include, specific enthalpy, internal energy, low heating value, Wobbe number index, changes in Enthalpy, Entropy and Gibbs free energy. The experimental procedure was performed at temperature range of 29±3 °C for 61 days in a BlueSens laboratory-scale anaerobic digestion equipment. It comprised of three fermenter bottles designated as F1, F2 and F3. F1 served as the control and the rest served as the test fermenter bottles. The digestion of water hyacinth and fruit waste sludge (WH+FWS) recorded the highest biogas volumes of 19,798.79 ml in fermenter F2 and 19,168.55 ml in fermenter F3 with methane contents of 53.46 % and 51.85 %, respectively. In comparison, the biogas produced exclusively from the water hyacinth (WH) biomass yielded 12,014.49 ml in F2 and 11,384.25 ml in F3, with methane contents of 46.41 % and 43.31 %, respectively. The best biogas fuel was produced from the digestion of (WH+FWS) in fermenter F2 with an internal energy and enthalpy values of 258.6 KJ/kg. K and 344.9 KJ/kg. K, respectively. A low heating value and Wobbe number of 17.51 MJ/m³ and 17.78 MJ/m³ were determined respectively. The biogas production was simulated using the Gompertz modified kinetic equation in MATLAB and an average specific rate (Kexp) of 371.49 ml/gVS.day was obtained. The rate constant (Kexp) was applied in the linearized form of the Erying-Polanyi equation to determine the changes in Enthalpy Entropy, and Gibbs free energy as -2510.66 J, -304.78 J and 94,219 J, respectively which indicated that, the anaerobic digestion process in this study was only thermodynamically feasible at low temperatures.

Energy, exergy and economic investigation of novel hybrid dryer, indirect solar dryer and traditional shade drying

By integrating a secondary energy source into solar dryers, more moisture can be removed from food products in the same time period. For this purpose, tomato slices of different thicknesses (7 mm, 15 mm and quarter size) were dried to see the drying, energy, exergy and economic performance of an innovative hybrid dryer consisting of an indirect solar dryer and geothermal heat exchanger unit. The hybrid dryer’s performance was compared simultaneously with indirect solar dryer and traditional shade drying. The analyzes were evaluated according to the feeding of drying air from the solar air collector and geothermal heat exchanger unit. Compared to the other two dryers, the hybrid dryer dried the 7 mm, 15 mm and quarter size samples in the earliest time, with an average of 1380, 2476.3 and 2397.3 min, respectively. The average highest specific moisture extraction rate (0.87 kg/kWh) and dryer efficiency (45.25 %) and the lowest specific energy consumption (4.75 kWh/kg) for hybrid dryer were obtained for the 15 mm. The highest exergy efficiency for the solar air collector and drying chamber of the hybrid dryer was determined at 7 mm with 3.08 % and 38.9 %, respectively. The lowest payback period for the hybrid dryer was found to be 0.37 years for 7 mm. The results showed that the hybrid dryer was superior to the other two dryers by drying continuously day and night. Hybrid dryer can create a successful commercial ecosystem as an important drying alternative for locations where geothermal energy is available.

A comparative study on pedestrian flow through bottlenecks between flood evacuation and land evacuation

In a flood, people may be forced to evacuate in water until reaching a secure shelter. Understanding the characteristics of pedestrian flow in water is therefore of utmost importance. Some researchers studied individual walking speed in water, whereas it is still rare to study pedestrian and evacuation dynamics, e.g., characteristics of pedestrian flow through a bottleneck. In this paper, evacuation experiments through bottlenecks are conducted in 0.60-m-deep water, with 97 volunteers with an average age of 21.7 years participating. The results are compared with those on land. It is shown that the flow rate in water is lower than that on land, with a difference varying with bottleneck width b as ΔJ=0.60b−0.04ped/s. The average specific flow rate in water is 0.43ped/(m·s) lower than that on land. Based on the relation of time headway–width, density–width, and speed–width, threshold widths for the flow transition from “interrupted” to “flowing” stages are 1.3 m in water and 1.0 m on land respectively. Compared with that on land, during “interrupted” stage in water, stop behavior is more frequent, the speed near the exit is 0.22 m/s lower, and the speed-up point is closer to the exit. During “flowing” stage, continuity of the pedestrian flow at exit is inferior in water compared to that on land, a 0.2–0.3 m wider exit is required in water to achieve similar continuity on land. These findings may provide valuable insights into emergency management during flood evacuation.

Microstructure, Mechanical and Tribological Properties of High-Entropy Carbide (MoNbTaTiV)C5.

High-entropy carbide (NbTaTiV)C4 (HEC4), (MoNbTaTiV)C5 (HEC5), and (MoNbTaTiV)C5-SiC (HEC5S) multiphase ceramics were prepared by spark plasma sintering (SPS) at 1900 to 2100 °C, using metal carbide and silicon carbide (SiC) as raw materials. Their microstructure, and mechanical and tribological properties were investigated. The results showed that the (MoNbTaTiV)C5 synthesized at 1900-2100 °C had a face-centered cubic structure and density higher than 95.6%. The increase in sintering temperature was conducive to the promotion of densification, growth of grains, and diffusion of metal elements. The introduction of SiC helped to promote densification but weakened the strength of the grain boundaries. The average specific wear rates for HEC4 were within an order of magnitude of 10-5 mm3/N·m, and for HEC5 and HEC5S were within a range of 10-7 to 10-6 mm3/N·m. The wear mechanism of HEC4 was abrasion, while that of HEC5 and HEC5S was mainly oxidation wear.

Critical Optical Depth Hypothesis for Phytoplankton Growth and Bloom. A New Graphical Approach to the Classic Sverdrup Critical Depth Model

A modification to the classic Sverdrup Critical Depth Model relating phytoplankton light-limited net growth in a mixed water column to its depth is presented by introducing optical depth in place of the physical depth of the column, as well as by the inclusion of self-shading and competition among phytoplankton species for light. The concept of critical optical depth of a well-mixed column is used to establish criteria for phytoplankton growth and competitive exclusion. This model shows not only the direction of the growth for a given column, such as the classic Sverdrup model, but also the magnitude of that growth. The model relies on plots of the average specific (per unit biomass) rate of this growth in the column against the optical depth of that column. These graphs are invariant under changes of light absorbers in the column as well as the depth of the column. In particular, these graphs do not change in the presence of competing species or with changes in column biomass, thus facilitating the analysis of these processes. Also, for this purpose, the concept of opacity load is introduced to name the optical depth. Such an extended Sverdrup model provides a simple visual, qualitative way of obtaining results consistent with Huisman and Weissing’s (1994) critical light theory. It is convenient for considering more complex phytoplankton growth scenarios.

Kretanje obolevanja i umiranja od kolorektalnog karcinoma kod muškaraca i žena Centralne Srbije za period 1999-2020. godine

Introduction/Aim: Colorectal cancer is the third leading cancer in terms of morbidity in the world, right after breast and lung cancer, and the second leading malignant tumor according to the number of deaths, after lung cancer. This descriptive study aimed to analyze the trends in incidence and mortality from colorectal cancer in men and women in Central Serbia from 1999 to 2020. Methods: Data on patients and deaths from colorectal cancer (codes C18-C20, according to the International Classification of Diseases), as well as on the number of inhabitants, by sex and age, for the period from 1999 to 2020, were taken from cancer registries in Central Serbia and at the request of the Institute for Public Health of Serbia "Dr. Milan Jovanović Batut". Crude, age-specific and standardized incidence and mortality rates for colorectal cancer were calculated. In order to analyze trends in incidence and mortality rates, joinpoint regression analysis was used. Results: In the period from 1999 to 2020 in Central Serbia, an average of 1696 men and 1112 women were diagnosed with colorectal cancer, and 990 men and 676 women died. In the mentioned period, the average standardized incidence rate (per 100,000) was 34.4 for men and 19.5 for women, and the average standardized mortality rate (per 100,000) was 18.4 for men and 10.1 for women. Average age specific incidence and mortality rates from colorectal cancer increase with age in both sexes. In the period 1999-2020, the standardized incidence rates of colorectal cancer are increasing significantly by 0.7% per year for women and 1% per year for men. In women, a significant increase in the mortality rate from colorectal cancer of 2.6% per year is observed in the period 1999-2006 year, and then a decline of 1.2% per year for the period 2006-2020. However, in men, a significant increase is observed in the period 1999-2010, followed by a decrease of 1.2% per year, but without statistical significance. Conclusion: It is necessary to work on improving the implementation of organized screening for colorectal cancer, as well as on educating the population about the risk factors for the occurrence of this malignancy and the possibilities for prevention.

Hydrological Processes in a Small Research Watershed under Forest Coverage in the Coast of Chiapas, Mexico

In the hydrological watershed, some natural processes take place in which the interaction of water, soil, climate and vegetation favors the capture of water. The present study aimed to evaluate preliminary information regarding the hydrological response and the water balance in a small research watershed with tropical forest cover (15°01'44''N and 92°13'55''W, 471 m, 2.3 has). Events of precipitation, direct runoff, infiltration rate and baseflow were performed. The amount, duration and intensity of rainfall events were recorded with the use of a pluviograph. Surface runoff was quantified with an established gauging station, an H-type gauging device and a horizontal mechanical gauging limnograph. Runoff base flow was measured at the gauging station using the volume-time method. Infiltration was measured using a triple ring infiltrometer, taking two measurements in the upper part and two in the lower part of the microbasin. Evapotranspiration was measured with the amount of rainfall entering and runoff leaving the watershed. In the study period, annual rainfall of 4417.6 mm distributed over 181 events were recorded; about 70% of the storms showed lower intensities at 20 mm·h-1. The total runoff was 345.8 mm caused by half of the rainfall events, which represents 7.8% of the total rain; 77% of runoff events showed lower sheets of 5 mm and an average specific rate of 20.7 L·s-1·ha-1 with a maximum of 113.6 L·s-1·ha-1. Three runoff events were greater than 20.1 mm and caused the 22.5% of the total runoff depth in the study period showing the equilibrium conditions in the hydrological response of the forest. Water outputs like baseflow was 669.5 mm. In this way, 90% of the rainfall is infiltrated every year in the micro-watershed, which shows the importance of the plant cover in the hydrological regulation and the groundwater recharge.

Sustainable strategy for lignocellulosic crop wastes reduction by Tenebrio molitor Linnaeus (mealworm) and potential use of mealworm frass as a fertilizer

Lignocellulosic crop wastes (LCW) are refractory solid wastes that are not biodegradable at appreciable rates in most environments, causing management of LCW been environmental concerns for years. This study investigated the feasibility of low waste emission complete LCW (rice straw (RS), rice husk (RH), and corn straw (CS)) recycling through feeding to Tenebrio molitor Linnaeus larvae (mealworms) using egested frass to produce organic fertilizers. For larvae fed RS, CS, and RH plus nutrients co-diets groups, the 48-day average specific rates of LCW consumption increased by 118.09%, 155.30%, and 87.14%, respectively when compared with that of sole diet groups. The order of the feed consumption rate and conversion rate in a mealworm farm fed on the three LCWs agreed with the trend obtained with lab-scale experiments, with RS＞CS＞RH. The forty-eight days cellulose, hemicellulose, and lignin biodegradation increased by 1.48–17.61%, 4.26–11.50%, and 4.20–15.75%, respectively, for co-fed larvae. Enterococcus sp. and Erwinia sp., which previous reports have indicated are strongly associated with lignocellulose degradation, were identified in the gut microbiome of mealworms fed with RS and CS co-diets. Furthermore, the RS-fed frass quickly formed a high-quality compost within 32 days of composting, which had a germination rate ratio of 8% and 17% higher than that of WB and CS-fed frass. LCA (life cycle assessment) proved a relatively promising environmental-friendly alternative to dispose of RS, using their excreted frass for composting with low waste emissions. This study provides new insight into insect-involved crop waste utilization, and economical strategies for sustainable in situ recycling of LCWs into high-value-added products.

Experimental research on the determination of the filtration characteristic on the base of low-pressure hydraulic engineering constructions on complex multi-layer ground

In this study, the issue of studying the filtration flow characteristics of hydraulic engineering constructions designed by building a hydrodynamic grid for the filtration flow area using the method of electrohydrodynamic similarity is considered. Given there is complexity and diversity of filtration deformation problems in base of hydraulic engineering constructions, we conduct experimental studies to determine the filtration flow characteristics in base of low-pressure hydraulic engineering constructions in a special model to determine the overall picture and qualitative assessment of these processes. Before observing the filtration deformation processes in the construction soil, the filtration coefficients of the soils in the soil were determined using the Darcy device. The purpose of determining the filtration coefficients of soils is the importance of using the value obtained in the laboratory under experimental work. Based on the experimental studies, graphs of the average filtration flow rate and specific flow rate depending on the water pressure were constructed. The theoretical results obtained were compared with existing analytical methods.

Local Volume Late-Type Galaxies with an Extreme Ratio of Hα-to-FUV Star-Formation Rates

Abstract Using a currently most representative sample of 477 late-type galaxies within 11 Mpc of the Milky Way with measured star-formation rates (SFRs) from the far ultraviolet (FUV) and Hα emission line fluxes, we select galaxies with the extreme ratios: SFR(Hα)/SFR(FUV) > 2 and SFR(Hα)/SFR(FUV) < 1/20. Each subsample amounts to ∼5% of the total number and consists of dwarf galaxies with the stellar masses M*/M⊙ = (5.5 − 9.5) dex. In spite of a huge difference in their SFR(Hα) activity on a scale of ∼10 Myr, the temporarily “excited” and temporarily “quiescent” galaxies follow one and the same relation between SFR(FUV) and M* on a scale of ∼100 Myr. Their average specific star-formation rate log [SFR(FUV)/M*] = −10.1 ± 0.1 (yr−1) coinsides with the Hubble parameter log (H0) = −10.14 (yr−1). On a scale of t ∼ 10 Myr, variations of SFR have a moderate flash amplitude of less than 1 order above the main-sequence and a fading amplitude to 2 orders below the average level. In general, both temporarily excited and temporarily quiescent galaxies have almost similar gas fractions as normal main-sequence galaxies, being able to maintain the current rate of star-formation on another Hubble time scale. Ranging the galaxies according to the density contrast produced by the nearest massive neighbor exhibits only a low average excess of SFR caused by tidal interactions.

A perspective on sodium-induced agglomeration of Zhundong coal gasification: Experiments and calculations

In order to provide basic knowledge for the gasification utilization of low-rank Zhundong (ZD) coal in the process of circulating fluidized bed (CFB), this study focuses on gasification reactivity and ash related agglomeration of ZD coal mainly induced by sodium transformation. Typical ZD coal was pyrolyzed in a horizontal tube reactor by a rapid pyrolysis method at 900 °C. Isothermal and non-isothermal thermogravimetric analyses were used to study the gasification reactivity of ZD char under CO2 atmosphere. The effect of temperature, ranging from 850 °C to 1050 °C, on isothermal gasification was investigated, and the obtained gasification residues were analyzed to observe microscope morphology and evaluate agglomeration degree. The ternary system relationship of Na2O–SiO2–Al2O3 at each gasification temperature was calculated with FactSage to compare with the experimental results. The results show that: the gasification reactivity of ZD coal char is greatly affected by the gasification temperature. Higher temperature can increase the average specific gasification rate, thus shorten the reaction time that the carbon conversion reaches equilibrium. The gasification reactivity of coal char is proved to be better at higher temperature. The agglomeration characteristics were also affected by the gasification temperature. There is almost no melting and agglomeration phenomenon for 850 °C gasification residue, while a strong tendency to agglomeration is showed in other samples. However, when the mass fraction of local CaO on the surface of large particles is more than 40%, the melting phenomenon can be alleviated. According to the Na2O–SiO2–Al2O3 phase diagram, the positions of ZD coal and ZD char are located near the complete Slag-liq region, indicating that using ZD coal and ZD char at the operation temperature of CFB above 950 °C has strong risk of slagging, and a relatively lower gasification temperature, ∼900 °C, is suitable for ZD coal/char gasification.

A spatial analysis and modeling study of sedimentation impacts on dams found in south Gondar zone, Ethiopia

Sedimentation is a significant issue for agricultural dams in Ethiopia, as it diminishes the capacity limit and life expectancy of the repositories. The procedure of sedimentation begins from the very first moment of the seizing of water in some random supply. Even though an arrangement is made for each reservoir during anticipating a specific stockpiling limit, explicitly for silt testimony, called dead storing, a significant part of the sediments gets kept for a long time of the supply's life in zones other than the dead storing, and this pattern cannot be turned around at a simple expense. This investigation is focused on the examination of persuasive sedimentation forms in the close by many dams found in the south Gondar zone catchment situated inside the Upper Blue Nile Basin of Ethiopia and spotlights on the appraisal of yearly sedimentation rate. Spatial investigation and displaying examines were directed dependent on the Revised Universal Soil Loss Equation and GIS to decide silts yield and level of effect of every store for a given scene, precipitation, and catchment heterogeneity. Field perceptions and soil testing were done to decide the components that lead to repository sedimentation. Spatial Data on the dams in south Gondar zone catchment were likewise gathered from the Ministry of Agriculture, which were utilized for ground-truthing, GIS-based computations, and model approval. The average specific sediment rate and silt delivery proportion were seen as 4059.2 t km−2 year−1 and 72.67%, individually. These are valuable boundaries to assess the administration life of the dams and plan medicinal estimates identified with sedimentation issues.

Kinetics and Isotherms of Mercury Biosorption by Dry Biomass of Arthrospira (Spirulina) platensis

AbstractInorganic mercury was effectively removed from water solutions by means of dry biomass of Arthrospira (Spirulina) platensis as biosorbent. The results obtained at defined pH and biomass concentration as well as variable Hg concentrations were used to estimate biosorption kinetics and isotherm parameters. Biosorption kinetics was best described by the pseudo‐first‐order model of Lagergren that allowed estimating an average specific rate constant as high as 0.044 min−1, while the Dubinin and Radushkevich model was the best fitting isotherm. Hg biosorption seemed to occur via physisorption. Considering the wide dissemination of A. platensis and its easy cultivation, these results point to its biomass as a low‐cost biosorbent to treat Hg‐contaminated waters.

Effect of electric field on oxide layer structure at zirconium oxidation in H2O, CO2 and H2O/CO2 supercritical fluids

Oxidation of zirconium plates in supercritical fluids H2O, CO2 and H2O/CO2 was studied at 823 K and 24–39 MPa. An experimental cell was a flat capacitor, where the zirconium plate acted as the anode and the copper plate of the same size was the cathode. The interelectrode gap was 2 mm. The experiments were carried out in the absence of electric field and in the electric field of 300 kV m−1. It has been found that in all cases the oxidized layer consists of two parts: the outer loose layer and the inner dense layer forming an interface with Zr. At oxidation in a medium containing H2O, there is non-uniformity in distribution of oxygen near the boundary region of the loose and dense layers. When Zr is oxidized in the H2O/CO2 mixture, zirconium carbonate is found on the surface. In the electric field, an average specific rate of an increase in the sample mass decreases linearly with an increase in the fraction of CO2 in the H2O/CO2 mixture, and without the electric field it increases. Apparently, the reason for this is formation and subsequent decomposition of zirconium carbonate, leading to additional destruction of the oxidized layer and accelerated oxidation. When Zr is oxidized in CO2 in the presence of the electric field, a 12-fold increase in the rate of zirconium oxidation is registered, and this is associated with an increase in the surface leakage current due to formation of amorphous carbon.

Mathematical–Statistical Problem that Has a Significant Implication on Estimation of Interval-Specific Rates of Soil-Forming Processes

Mathematical–statistical problem on estimation of soil-forming processes. This paper raises a mathematical–statistical problem that finally can be found in any chronosequence of a specific Quaternary-based process (e.g. soil mass, clay content accumulation). The problem arises when interval-specific rates of a component f(t) are intended by dividing the stock by the given age t. The procedure implies that only an average specific rate is calculated in a linear form, for example when soil organic carbon often tends to an asymptotic end-value. For any other parameters (e.g. sedimentation rates, soil horizons thickness), the same holds true. The mathematical–statistical problem arises if the rates are derived using a linear calculation (individual stocks, f(t) divided by time, t) and then plotted as a function of time, in circumstances where there is no correlation between t and the components f(t). To illustrate this problem, we used a random generator function where the plot t versus f(t) are not correlated. We also give examples of the chronosequence approaches of soil organic carbon and soil mass, where, at a given point, the real specific rate corresponds to the slope (first derivative) of the obtained non-linear regression function. The random generator function for the plot t versus f(t) showed no significant relationship (R2 = 0.0), but f(t)t−1 and t showed highly significant correlation (R2 = 0.62). The error in calculating the component rate by dividing by time instead of using the derivative function when the processes are not linear ranged between 22% and > 500%. We conclude that non-independent variables plotted in a chronosequence can infer correlations even when they might not exist. Carefully observation is needed on the dataset when the time is involved, particularly in Quaternary-based studies, since the mass component not necessarily is related with time. Avoid in calculating the change of the mass component simply dividing by time, because an over- or under-estimation from real rate (obtained by derivative function) occurs when the process under study is not linear.

Performance analyses on fluidized bed dryer integrated biomass furnace with and without air preheater for paddy drying

The performance of a fluidized bed dryer integrated biomass furnace with air preheater (FBD with APH) and a fluidized bed dryer integrated biomass furnace without air preheater (FBD without APH) for drying of paddy have been evaluated. The FBD with APH and FBD without APH decreased the moisture of paddy from 24% (wet basis) to 14% (wet basis) within 43 and 47 minutes with average temperatures and relative humidities of 59.58 <sup>o</sup>C and 59.14<sup>o</sup>C, and 18.81% and 18.68%, respectively. The drying rate of paddy varied in the range of 0.11 kg/min-0.32 kg/min and 0.10 kg/min- 0.30 kg/min for FBD with APH and FBD without APH, with average values of 0.18kg/min and 0.17kg/min, respectively. The minimum, maximum, and average value specific moisture evaporation rate (SMER) was 0.20 kg/kWh, 0.57 kg/kWh, and 0.31 kg/kWh, respectively for FBD with APH, as well as 0.149 kg/kWh, 0.448 kg/kWh, and 0.252 kg/kWh, respectively, for FBD without APH. The specific energy consumption (SEC), the specific electrical energy consumption (SEEC), and the specific thermal energy consumption (STEC) were varied from 1.749 kWh/kg to 5.076 kWh/kg, 0.090 kWh/kg to 2.872 kWh/kg, and 0.760 kWh/kg to 2.204 kWh/kg, with average values of 3.528 kWh/kg, 1.96 kWh/kg, and 1.532 kWh/kg, respectively for FBD with APH, as well as from 2.234 kWh/kg to 6.702 kWh/kg, 1.056 kWh/kg to 3.167 kWh/kg, and 1.179 kWh/kg to 3.536 kWh/kg, with average values of 4.391 kWh/kg, 2.075 kWh/kg, and 2.316 kWh/kg, respectively, for FBD without APH. The thermal efficiencies of the FBD with APH and FBD without APH were varied between 12.4% and 37.93%, and 9.78% and 29.82%, resvectively, with average values of 20.78% and 16.61%. The thermal efficiency of FBD with APH was higher compared to FBD without APH.

Simulation and Analysis on the Optimal Tax Rate of Water Resources in Yunnan Province

The shortage of water resources has become an increasingly common problem. One of the biggest challenges in China’s current economic development is the prominent contradiction between water supply and demand in some densely populated areas. Although Yunnan Province has abundant water resources, due to factors such as precipitation timing, uneven distribution, regional geological conditions and low water-use efficiency, there are also contradictions in water supply and demand. In order to accelerate the transformation of extensive regional water resources utilization and achieve sustainable regional economy development, this paper establishes a Computable General Equilibrium Model (CGE) incorporating water resources elements of Yunnan Province, and simulates the water price changes. The conclusion is that the reasonable tax rate of water resources in Yunnan Province should be about 13%. Considering the corresponding average water price, the average specific tax rate of water resources should be 0.21 yuan/m3.

X-rays across the galaxy population – III. The incidence of AGN as a function of star formation rate

We map the co-eval growth of galaxies and their central supermassive black holes in detail by measuring the incidence of Active Galactic Nuclei (AGN) in galaxies as a function of star formation rate (SFR) and redshift (to z~4). We combine large galaxy samples with deep Chandra X-ray imaging to measure the probability distribution of specific black hole accretion rates (LX relative to stellar mass) and derive robust AGN fractions and average specific accretion rates. First, we consider galaxies along the main sequence of star formation. We find a linear correlation between the average SFR and both the AGN fraction and average specific accretion rate across a wide range in stellar mass ($M_* \sim 10^{8.5-11.5}M_\odot$) and to at least z~2.5, indicating that AGN in main-sequence galaxies are driven by the stochastic accretion of cold gas. We also consider quiescent galaxies and find significantly higher AGN fractions than predicted, given their low SFRs, indicating that AGN in quiescent galaxies are fuelled by additional mechanisms (e.g. stellar winds). Next, we bin galaxies according to their SFRs relative to the main sequence. We find that the AGN fraction is significantly elevated for galaxies that are still star-forming but with SFRs below the main sequence, indicating further triggering mechanisms enhance AGN activity within these sub-main-sequence galaxies. We also find that the incidence of high-accretion-rate AGN is enhanced in starburst galaxies and evolves more mildly with redshift than within the rest of the galaxy population, suggesting mergers play a role in driving AGN activity in such high-SFR galaxies.

SUBDOMÍNIOS HIDROGEOLÓGICOS DO AQUÍFERO POROSO DE PORTO VELHO, RONDÔNIA, BRASIL

Estudos hidrogeológicos foram desenvolvidos na zona urbana da cidade de Porto Velho, Rondônia, que compreende um sistema hidrogeológico poroso, heterogêneo e anisotrópico, possuindo propriedades de aquíferos livres, bem como semiconfinados quando envoltos por aquitardo. Constitui-se por coberturas cenozoicas com espessura média de 61,8 metros que sobrepõe às rochas granitoides do embasamento regional. A estratigrafia de 189 poços tubulares de captação de água subterrânea possibilitou a identificação do domínio hidrogeológico poroso e seus subdomínios laterítico e sedimentar. O subdomínio laterítico (materiais do perfil laterítico) possui produtividade baixa a muito baixa e vazão específica média de 0,26 m³/h/m. No subdomínio sedimentar (depósitos sedimentares), foram identificadas as zonas hidrogeológicas aluvionar, aquitardo e sedimentos indiferenciados. A zona aluvionar denota produtividade alta a muito alta (vazão específica média de 11,4 m³/h/m) e localiza-se na porção leste da área de estudo. Por outro lado, a zona aquitardo apresenta produtividade muito baixa (vazão específica média de 0,39 m³/h/m) e localiza-se nas proximidades de drenagens, e a zona sedimentos indiferenciados corresponde a maior parte da área de estudo e exibe uma produtividade moderada a baixa (vazão específica média de 1,9 m³/h/m).

Methane oxidation coupled to denitrification under microaerobic and hypoxic conditions in leach bed bioreactors

Managing nitrogen and carbon cycles in landfills is an environmental challenge. In this study, our purpose was to test two types of methane oxidation processes coupled to denitrification inside landfills: microaerobic and hypoxic methane oxidation coupled to denitrification (MAME-D and HYME-D). Leach bed bioreactors were designed and operated for >100 d with NO3−-N concentration ranging from 100 to 400 mg N/L. During six runs of the leach bed bioreactor experiment, leach bed bioreactor 2 (MAME-D) reached 100% denitrification efficiency and the highest average specific denitrification rate of 20.36 mg N/(L·d) in run 5, while leach bed bioreactor 3 (HYME-D) achieved 75% denitrification efficiency and the highest average specific denitrification rate of 8.09 mg N/(L·d) in run 6. Subsequently, waste from leach bed bioreactors 1, 2, and 3 was inoculated into anaerobic bottles to run a batch experiment for 13 d. The total consumed methane, oxygen, and nitrate amounts in the microaerobic system with no methane and oxygen supplement were 2.33, 2.38, and 2.04 mmol, respectively, which almost matched the theoretical equation of aerobic methane oxidation coupled to denitrification. In the hypoxic system, the total consumed methane and nitrate amounts were 0.23 and 0.41 mmol, respectively, the ratio of which closely matched the HYME-D. In addition, via the diverse functional community analysis, methane oxidation in the microaerobic system was confirmed to be conducted by methanotrophs (i.e., Methylobacter and Methylomonas) using oxygen as an electron acceptor. Subsequently, the generated organic compounds could support denitrifiers (i.e., Methylophilaceae) to complete denitrification. In the hypoxic system, Methylomonas and Methylobacter utilized nitrate as a direct electron acceptor to oxidize methane. The two landfill processes characterized here will expand our understanding of the environmental role of methanotrophs and methylotrophs in both carbon and nitrogen cycles.