Range Of Residence Times Research Articles

Linking reservoir annual residence time to nitrogen deposition using paleolimnological techniques

In river networks, reservoirs are hotspots for nutrient transformations, providing multiple pathways for nitrogen processing. One of the less measured pathways is nitrogen deposition. Here, we investigated the decadal relationship between water residence time and nitrogen deposition using sediment cores from eight mainstem reservoirs within a river system containing two contrasting watersheds. One watershed was significantly urbanized with regulated flow and the other watershed was unregulated with extensive rural land use. We explored the relationship of sediment nitrogen concentrations across a range of residence times, land uses, and other parameters throughout this linked river-reservoir system. Results show that average annual residence time had the strongest relationship to nitrogen deposition when compared to reservoir volume, mean depth, surface area, outflow, and land use. Pigment analysis revealed that residence time influences nitrogen by allowing for longer periods of algal uptake, followed by deposition in particulate organic form. Supporting this mechanism, sedimentary C:N, with low values representing greater algal influence, expressed a strong and negative relationship with average annual residence time, as well as a positive relationship between residence time and photosynthetic pigments diagnostic of cyanobacteria, diatoms, and a combination of green algae+cyanobacteria. Furthermore, we investigated how drought conditions could alter residence times and intensify nitrogen cycling through primary productivity in reservoirs. Drought increased residence time by 45–60 %. This increase was estimated to raise sediment nitrogen concentrations by roughly 2.5–4 %.

Microbial nitrogen nutrition links to dissolved organic matter properties in East African lakes

East African lakes, especially soda lakes, are home habitats for massive numbers of wildlife such as flamingos, mammals, and fishes. These lakes are known for their high primary production due to local high temperatures, light intensities, and alkalinity (inorganic carbon). However, these lakes, normally within remote areas, receive low nutrient inputs. Ammonium (NH4+) recycling and/or nitrogen fixation can become the major N supply mechanisms for phytoplankton. However, the driving forces on microbial N nutrition in lakes with minimal anthropogenic disturbance remain poorly understood. Using stable isotope tracer techniques, NH4+ recycling rates were measured in 18 lakes and reservoirs in East Africa (Tanzania and Kenya) during the dry season in early 2020. Three functional genes (nifH, gdh, and ureC) relating to microbial N nutrition were also measured. The regeneration of NH4+ supported up to 71 % of the NH4+ uptake. Positive community biological NH4+ demands (CBAD) for all lakes and reservoirs indicate an obvious N demand from microbial community. Our study provides clear evidence that microbial NH4+ uptake rates linked closely to the dissolved organic matter (DOM) properties (e.g., the absorption coefficient at 254 nm, percents of total fluorescence intensity contributed by microbial humic-like and protein-like components) and that water residence time drives microbial NH4+ recycling by regulating the duration of in-lake DOM processing and influencing algal growth. Phytoplankton, especially those of Cyanophyceae, showed maximum biomass and higher NH4+ recycling rates at a certain range of water residence time (e.g., 5–8 years). However, CBAD showed a decreasing trend with longer water residence time, which may be influenced by changes in the algal community composition (e.g., % Cyanophyceae vs. % Bacillariophyceae). These results indicate that DOM dynamics and the water residence time have the potential to facilitate the understanding of microbial nitrogen supply status in East African lakes.

Modelling of JP-8 distributed combustion using a HyChem mechanism under gas turbine conditions

The critical advantages of liquid fuels in aviation over alternative energy carriers imply their dominance in the upcoming decades. The Mixture Temperature Controlled (MTC) combustion concept allows spatially homogeneous, efficient burning (distributed combustion) with low pollutant emission. MTC combustion of jet fuel JP-8 was investigated in an atmospheric burner, and the measured pollutant concentrations in the flue gas were reproduced using the Hybrid Chemistry (HyChem) approach employing Perfectly Stirred Reactor simulations. Using this robust approach comes with losing spatiotemporal characteristics if the mixture homogeneity assumption is globally valid. The effect of residence time and pressure under typical gas turbine operating conditions was investigated. Stable combustion was present above 3 ms residence time at pressures up the 60 bar, which was the upper limit of the investigated regime, while the lower residence time limit of stable combustion was 0.3 ms. The residence time interval of stable operation could be extended by applying flue gas recirculation. NO emission can be reduced by increasing the operating pressure, while the N2O production is dominant only up to 20 bar and in the 10–100 ms residence time range. CO emission vanishes above 10 ms residence time. Ultra-low emission operation requires >20 bar pressure and 10 ms residence time with distributed combustion, requiring larger combustion chambers for future jet engines.

The impact of lake discontinuities on nitrogen biogeochemistry in river networks

River networks connect terrestrial and marine ecosystems through transport of pollutants and nutrients. Lakes represent discontinuities within these river networks, which can be important biogeochemical hotspots, introducing substantial changes to the aquatic environment. Nitrogen is a key macronutrient that can potentially limit or co-limit primary production, but the processes that determine the fate of nitrogen during transport through river-lake networks are poorly understood. We studied three river systems and their lake discontinuities, spanning a range of trophic states and average water residence times, to understand the changes introduced to riverine nitrogen biogeochemistry by lake discontinuities. In-lake processes noticeably altered the concentration and speciation of nitrogen. Annually, lakes reduced up to 44% of nitrate compared to main inflow concentrations, while there was large variability in nitrate dynamics seasonally. The drawdown in surface nitrate concentrations resulted at times in phytoplankton co-limitation by nitrogen in-lake, as well as in the downstream river, where altered nitrogen patterns could persist for several kilometers. However, lakes occasionally subsidized N to downstream rivers as ammonium or dissolved organic nitrogen. Assimilation of nitrate in lake surface waters was one of the dominant processes impacting nitrogen availability; however, stable isotope data revealed an unexpected contribution of nitrification on nitrogen cycling in the epilimnion throughout the year and across trophic gradients. These changes in nitrogen concentration, as well as speciation introduced by lake discontinuities have potentially important consequences for the composition and metabolism of communities in downstream rivers and contribute to our fundamental understanding of freshwater processes.

Update of the Interpretive Conceptual Model of Ladeira de Envendos Hyposaline Hydromineral System (Central Portugal): A Contribution to Its Sustainable Use

The aim of this paper is to describe the surveys performed in order to update the interpretive conceptual circulation model of the Ladeira de Envendos hyposaline hydromineral system (Central Portugal). The geology of the Ladeira de Envendos region is strongly controlled by the Amêndoa-Carvoeiro synform, of Ordovician-Silurian age, presenting continuous and aligned quartzite ridges on the NE flank, that form the basic structure of a set of inselbergs. The physico-chemical analysis of the Ladeira de Envendos natural mineral spring and borehole waters was provided by the Super Bock Group Enterprise (Concessionaire of the Ladeira de Envendos). Furthermore, two sampling campaigns took place to increase knowledge on the isotopic composition of the studied natural mineral waters. The stable (δ2H, δ18O) isotopic data indicate that local meteoric waters infiltrate around 400 m altitude and evolve to the natural mineral waters (of Cl-Na facies) through a NW–SE underground flow path ascribed to the highly fractured and permeable quartzite rocks. From recharge to discharge, the infiltrated meteoric waters acquire silica (±9 mg/L) due to water–quartzite rock interaction. These natural mineral waters emerge at temperatures around 21 °C, being the up flow of these waters controlled by the rock fractures and local faults. The natural mineral waters mean residence time range between 25 and 40 years, as indicated by the 3H content of these waters, enhancing an active recharge of this hydromineral system. The results obtained indicate existence of three hydrogeological subsystems, ascribed to three inselbergs, with similar groundwater circulation paths. These multi and interdisciplinary studies should be seen as an important contribution to the sustainable management of this type of natural mineral water resources.

Impact of densification process on unprocessed biomass and post-hydrothermal carbonization

The pulp and paper industry use biomass residues, such as paper sludge and bark as fuel to provide energy for their plants. However, issues such as high-water content or low heating value limit the amount of energy that can be utilized. Processes to improve heat generation include biomass densification, which facilitates transportation and handling and can increase energy yield. However, the technical feasibility of briquetting is a function of the feedstock and preprocessing. This study introduces a novel approach to briquette production from biomass residues by utilizing wet biomass with water as a natural binder, contrasting with conventional methods that require forced drying and/or the addition of binders. The objective of this research was to investigate the impact of briquetting both unprocessed biomass and post-hydrothermal carbonization. The study focused on manufacturing briquettes derived from different sources, including bark (Balsam fir), paper sludge, and hydrochar of paper sludge. The feedstock was characterized for ash content and higher heating value. Biomass particle size (range), moisture content (range), process temperature (range), process pressure (range), and process residence time (range) were varied in briquetting experiments to determine conditions to produce high-quality briquettes with minimal energy input. Moisture content as high a 50 wt% in feedstock produced technically feasible briquettes, with appropriate physical-mechanical properties (durability, volumetric expansion and apparent density), and energetic potential (calorific value). The addition of heat (pressing temperature of 150 °C) during the pressing process resulted in briquettes with enhanced physical-mechanical, and energetic properties, surpassing those produced at room temperature. Further tests with additional steps in the production process are required to meet commercialization standards in Canada, but the treatments conducted in this study effectively improved the energy potential of biomass for internal industrial energy gains.

Dehydration and decarboxylation via pyrolysis process of waste oily sludge accumulated at North Refineries Company Baiji for use as a pyro-fuel

Waste oily sludge (WOS) accumulated in a yard was exposed to sunlight and stored randomly from various sources at North Refineries Company Baiji (NRC). This study aims to convert WOS into pyro-fuel via pyrolysis technology via ranges of temperatures and times. First, run; a range of temperature was 250, 450, and 650 °C respectively, feed amount 5 g of WOS, residence time 90 min, under N2 pressure. Second, run; with a range of residence time at 60, 90, and 120 min respectively, with feed amount 5 g, the temperature at 650 °C (optimum temperature found). The pyro-fuel was investigated via solid yield, high heating value HHV (proximate and ultimate analysis), fuel ratio, and atomic ratio, it was compared with the raw material WOS. As a result, the best pyro-fuel was ((pyro@90–650 reached HHV16.20 MJ/kg) and (pyro@120–650 reached HHV 15.95 MJ/kg)). The best HHV was increased from 9.11 to 16.20 MJ/kg enhanced by 77.82%, and the fuel ratio reached 0.77 of WOS, increased to 0.85 about a 10.40% increase of best pyro-fuel. While the atomic ratio was decreased of pyrochars, this indicated that the pyro-fuel was enhanced. As finding the pyro-fuel produced from WOS has a higher HHV and carbon content, which can be used as a solid carbon alternative fuel for energy production in the oil industry at NRC Baji.

Exploring the impact of partial pressure and typical compounds on the continuous electroconversion of CO2 into formate

Previous research in CO2 electroreduction primarily focused on cathodic electrocatalysts and electrode configurations using pure CO2. Few studies explored the impact of residence time and N2/O2 compounds, crucial for practical industrial implementation. In this study, the effect of residence time and the influence of N2 and O2 compounds on CO2 electroreduction to formate are investigated, employing Bi carbon-supported nanoparticles in the form of Gas Diffusion Electrodes within an electrochemical flow reactor with a single pass of the reactants. The results highlight the critical role of residence time and the impact of N2 and O2 compounds in the CO2 electroconversion process. On the one hand, the evaluation of residence time holds paramount significance for the potential establishment of a large-scale CO2 recycling plant, as it has the potential to significantly impact both the capital and operational costs of the integrated electrolyzer-separator system. Optimal results are obtained in the range of residence times between 1.8 and 2.9 seconds, corresponding to CO2 flow rates of 150 and 250 mL·min−1, respectively. On the other hand, the study resulted in a promising Faradaic Efficiency for formate of 75.0%, with similar values achieved at CO2 concentrations in the range of 75 – 100 vol%. These results are particularly noteworthy as they demonstrate that achieving a CO2 capture efficiency of 100% is not necessary, thereby reducing the costs associated with this process and, consequently, the overall cost of integrating both capture and utilization processes in a CO2 recycling plant.

Pyrolytic decomposition of methanol, ethanol, and butanol at various temperatures and residence times in a high-temperature flow reactor

The potential use of low-carbon renewable fuel molecules, such as short chain alcohols, as a substitute or extender for fossil fuels, offers an opportunity to address pollutant emissions from transport and the sustainability of energy sources. Moreover, it may help reduce pollutants detrimental to air quality and human health, of which particulate matter (PM) is a significant contributor. To this end, the pyrolysis of three renewable alcohol fuels, methanol, ethanol, and butanol, has been studied in a laminar flow reactor at a sample inlet temperature range of 869 0C to 1120 0C. All the tested fuels were injected into a nitrogen carrier gas stream at a fixed concentration of 10,000 ppm on a carbon atom basis. A range of pyrolysis temperatures and residence times were selected so as to gain insight into the pyrolytic decomposition of short chain alcohol fuels to intermediate species important to the subsequent formation of benzene rings, larger polycyclic aromatic hydrocarbons (PAH), and particulate matter. In this paper, the presence of ten intermediary species that may aid in the formation of benzene rings and the growth of PAHs were quantified, with an emphasis on probable routes of first ring formation from the alcohols of varying chain length. Gaseous samples were collected from the pyrolyser at different temperatures and residence times using a novel high-temperature air-cooled ceramic sampling probe. The identification and quantification of intermediate gaseous species were undertaken by Gas Chromatography-Flame Ionization Detection (GC-FID). During methanol pyrolysis, only a tenth of the supplied carbon was detected as hydrocarbon gaseous species (mainly methane), with no benzene found, highlighting that methanol pyrolysis does not readily result in polyaromatic hydrocarbons and soot. Ethanol and butanol pyrolysis produced substantial amounts of ethylene and acetylene, suggesting a role in benzene and soot formation. Uniquely, pyrolysis of the longest chain alcohol, butanol, produced appreciable levels of C3 and C4 hydrocarbons, in addition to C1 and C2 hydrocarbons, suggesting additional reaction pathways for benzene formation and growth in comparison with ethanol.

GEOTRACES Reflections

GEOTRACES is an international program that has benefited from contributions by investigators in 35 nations. The program mission is to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes in the ocean and to establish the sensitivity of these distributions to changing environmental conditions. This perspective first summarizes the historical motivation for the program, and then describes selected research highlights, focusing on recent findings related to iron. The patchy distribution of iron in the ocean indicates a short residence time, at the low end of the range of residence times estimated in models. Iron removal from the ocean must, therefore, be rapid. Recent results from the North Atlantic Ocean suggest that the formation of particulate authigenic iron phases may be a factor contributing to iron removal that is faster than previously thought. This article also identifies several areas where advancements are expected through modeling and synthesis efforts.

Predictive mechanistic modeling of loading and elution in protein A chromatography

Protein A chromatography is an enabling technology in current manufacturing processes of monoclonal antibodies (mAbs) and mAb derivatives, largely due to its ability to reduce the levels of process-related impurities by several orders of magnitude. Despite its widespread application, the use of mathematical modeling capable of accurately predicting the full protein A chromatographic process, including loading, post-loading wash and elution stages, has been limited. This work describes a mechanistic modeling approach utilizing the general rate model (GRM), the capabilities of which are explored and optimized using two isotherm models. Isotherm parameters were estimated by inverse-fitting simulated breakthrough curves to experimental data at various pH values. The parameter values so obtained were interpolated across the relevant pH range using a best-fit curve, thus enabling their use in predictive modeling, including of elution over a range of pH. The model provides accurate predictions (< 3% mean error in 10% dynamic binding capacity predictions and ∼ 5% mean error in elution mass and pool volume predictions, both on scale-up) for various residence times, buffer conditions and elution schemes and its effectiveness for use in scale-up and process development is shown by applying the same parameters to larger columns and a wider range of residence times.

Selective Methanol Oxidation to Green Oxygenates—Catalyst Screening, Reaction Kinetics and Performance in Fixed-Bed and Membrane Reactors

Experimental and simulation-based investigations are carried out for the selective oxidation of green methanol to the oxygenates dimethoxymethane (DMM) and methyl formate (MF), including an initial catalyst screening, the derivation of a reaction kinetic model, and a feasibility study of a fixed-bed and a membrane reactor with oxygen distribution. The catalyst screening of different supports and loading of vanadium revealed a 6.6 wt.-% VOx/TiO2 catalyst offering the highest potential to the formation for the target products. Kinetic experiments performed in a broad range of operation conditions, e.g., residence time, temperature, and oxygen concentration, are used for the postulation of a reaction network, providing the basis for mathematical modeling of the individual five reaction rates with a reduced mechanistic approach. A simulation study based on the derived reaction kinetics and parameters revealed the high potential of a distributed oxygen dosing at high residence times, outperforming the conventional fixed-bed reactor by up to 6% in the yield of DMM and up to 19% in the yield of MF. The formation of DMM is favored at low temperatures, whereas the formation of MF is supported by high temperatures.

Constraining Bedrock Groundwater Residence Times in a Mountain System With Environmental Tracer Observations and Bayesian Uncertainty Quantification

AbstractGroundwater residence time distributions provide fundamental insights on the hydrological processes within watersheds. Yet, observations that can constrain groundwater residence times over broad timescales remain scarce in mountain catchment studies. We use environmental tracers (CFC‐12, SF6, 3H, and 4He) to investigate groundwater residence times along a hillslope in the East River Watershed, Colorado, USA. We develop a Bayesian inference framework that applies a Markov‐chain Monte Carlo (MCMC) approach to estimate noble gas recharge temperature, elevation, and excess‐air parameters and the resulting environmental tracer concentrations. MCMC is then used to propagate the environmental tracer uncertainties to estimates of groundwater mean residence times inferred with lumped parameter models. All samples contain 3H, CFC‐12, and SF6 in addition to terrigenic 4He, suggesting a mixture of water characterized by modern and premodern residence times. 4He exponential mean residence times range from hundreds of years at the upslope well to thousands of years at the toe‐slope well assuming average crustal production rates. We find that binary mixing residence time distributions with separate young and old mixing fractions are needed to predict the 4He, CFC‐12, SF6, and 3H observations, supporting the importance of flow path mixing in this bedrock system. Our findings that the fractured bedrock hosts groundwater with a mixture of residence times ranging from decades to millennia suggest variable recharge dynamics and flow path mixing along the hillslope and highlight the importance of characterizing groundwater systems with observations that are sensitive to transport over a broad range of residence times.

Exploration of new olefin production process: Effects of the addition of CO2 and H2O on n-heptane pyrolysis

In order to study the new cracking process characteristics of hydrocarbon feedstock to light olefins by direct flue gas heating, the pyrolysis experiments of n-heptane in CO2 and H2O atmosphere were performed in pretreated STS316L flow reactor (ϕ10 mm × 2.5 mm × 700 mm) at a temperature range of 1073–1373 K, pressure range of 0.1–1.0 MPa. By changing the n-heptane flow and system pressure to adjust the residence time, results show that the latter is not conducive to olefin formation, but the residence time range about high olefin formation of the latter is wider than that of the former. Due to the promotion of CO and the high-temperature solubility of CO2, the types and contents of PAHs in tar under H2O&CO2 atmosphere are higher. Based on the analysis of n-heptane cracking products stream, the reactivity of H2O and CO2 gradually appears at high temperature and the reactivity of H2O is significantly higher than that of CO2, resulting in higher yields of H2 and CO. The mainstream of the process is the cracking of n-heptane, in which H2O is the supply source of •OH and •H, and CO2 acts as a coking agent. High olefin yields can be achieved in either H2O-rich or CO2-rich atmosphere, and the ratio of the two needs to be properly regulated.

Impact of temperature and residence time on the hydrothermal carbonization of organosolv lignin

Herein, we have investigated how pure lignin extracted from birch and spruce via a hybrid organosolv/steam explosion method reacts under hydrothermal carbonization (HTC) to produce hydrochar, a product that has found applications in environmental remediation, energy storage and catalysis. We subjected thirteen lignin samples obtained from birch and spruce under different extraction conditions to HTC at 260 ℃ for four hours. The yield of hydrochar varied between the different extraction conditions and source, although no clear correlation between extraction conditions and yield could be observed. For instance, lignin from birch pretreated in 60%v/v ethanol for 15 min resulted in a hydrochar yield of 39 wt%. Increasing the time to 30 and 60 resulted in a hydrochar yield of 27 wt% and 23 wt%, respectively. This suggested that small changes in the organosolv reaction conditions might produce highly structurally different lignin, resulting in the difference in HTC yield. Thus, we chose a subset of four lignin samples to investigate in-depth, subjecting these samples to a range of hydrothermal reaction temperatures and residence times. Solid State NMR and FTIR analysis indicated that the most significant structural changes occurred below 230 ℃ resulting in the breaking of C-O- linkages. Increasing the temperature or time had minimal impact, with no further C-O- linkages broken and no changes to the ring structure of C-C groups. Size exclusion chromatography indicated that the degree of micro and macromolecules in the liquid product varied significantly with lignin source and HTC reaction conditions. Overall, this study demonstrated that lignin has a large reaction range where it produces a very chemically similar solid product, with the only major difference being the yield of material. This is important for industry, as it indicates that a similar solid product can be easily achieved independently of extraction conditions allowing the HTC reaction to be tuned towards extracting the maximum benefit from products contained in the liquid.

Strontium and radium occurrence at the boundary of a confined aquifer system

Aquifers are susceptible to contamination by naturally occurring metals and radionuclides that limits the quantity of groundwater available for drinking. The Midwestern Cambrian-Ordovician aquifer system (MCOAS) is an important drinking water source in the North Central region of the U.S., but can contain elevated levels of geogenic radium (Ra) and strontium (Sr). Here, the occurrence of Ra and Sr is investigated with respect to natural groundwater evolution and water-rock interactions using a multi-isotope approach (δ18O, δ2H, δ34SSO4, 87Sr/86Sr, and [234U/238U]), in a portion of the MCOAS that straddles regionally unconfined and regionally confined conditions. Hierarchical cluster analysis reveals three distinct groups of groundwater geochemistry, evolving from a young (<10,000 years) HCO3−- dominant groundwater located upgradient to old (>10,000 years) SO42− and Cl−-dominant groundwater located downgradient. Strontium and Ra concentrations are highest downgradient, where extreme [234U/238U] disequilibrium indicates increased water-rock interactions due to local confinement or a stagnant groundwater zone. Geochemical conditions evolve as a consequence of water-rock interaction, resulting in Ra and Sr mobilization mechanisms including enhanced mineral dissolution and weathering, and decreased sorption efficiency due to competitive sorption and the absence or dissolution of iron and manganese (hydr)oxides with sorbed Ra and Sr. Relative to redox processes, ‘mixed’ redox samples have the highest median Sr and Ra concentrations, where young, oxic groundwater mixes with old, anoxic groundwater over long open boreholes. Isotopic results (δ18O and δ2H, 87Sr/86Sr) indicate these wells with long open boreholes are receiving more of the old, deep groundwater elevated in Ra and Sr, suggesting that well construction is an important consideration for Ra and Sr occurrence. The presented framework can be used to examine the occurrence of geogenic contaminants with respect to recharge history, water-rock interactions, and evolving geochemical conditions in other aquifer systems with a range of groundwater residence times and geochemistry.

Molecular analysis of nitrogen-containing compounds in vacuum gas oils hydrodenitrogenation by (ESI+/-)-FTICR-MS

This paper is a part of a study on reactivity descriptors in vacuum gas oil hydrotreatment (VGO HDT). It aims to understand the differences in feeds of various process origins and the corresponding hydrotreated effluents on a molecular level. Four different vacuum gas oils were hydrotreated over a sulfided NiMo/Al2O3 catalyst at a wide range of temperatures and residence times in order to collect HDT effluents at a broad range of hydrodenitrogenation (HDN) conversions. Vacuum gas oils and HDT effluents have been analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) in positive ESI(+) and negative ESI(-) electrospray ionization modes to characterize the basic and neutral nitrogen-containing species and the subtleties of HDT transformations depending on the feedstock type.

Dark diversity at home describes the success of cross‐continent tree invasions

AbstractAimNon‐native species threaten ecosystems worldwide, but we poorly know why some species invade more. Functional traits, residence time and native range size have been often used as invasion predictors. Here, we advance in the field by linking invasion success to native range parameters derived from dark diversity – a set of species present in the surrounding region that are absent in a study location even if ecological conditions are suitable. We tested whether those parameters improve the description of species success outside their native range.LocationNorth America; Europe and Mediterranean Basin.MethodsFor 170 tree species native in one and non‐native in another region, we defined their invasion success as the number of locations occupied at the non‐native range. The probabilistic dark diversity was estimated based on the species co‐occurrences in their native ranges. It specifies how suitable is a species for a location, even if the species is absent. We calculated two parameters: sum of native location suitabilities (niche breadth proxy) and dark diversity probability (how often a species is absent from suitable locations, indicating niche realization limitations). We explored whether models including the dark diversity parameters performed better than one with a common species range measure, the number of locations occupied. We accomplished our models by adding functional traits, residence time and invasion direction.ResultsInvasion success increased with the sum of native location suitabilities and decreased with dark diversity probability. This model with dark diversity parameters outperformed an alternative using the number of native locations occupied. Our best model included invasion direction, functional traits (including mycorrhizal status) and residence time, but dark diversity parameters remained important predictors.Main conclusionsThe dark diversity parameters can contribute to invasion ecology by linking the species performance in the non‐native range to its niches parameters, derived from the native range.

Overall Rate Kinetics Model for Chlorine Demand of Urban Rainfall Runoff

The built environment significantly alters the rainfall-runoff response and associated transport of particulate matter (PM), chemicals, and pathogens in the urban water cycle. Urban water sustainability requires mitigation of runoff impacts while providing a potential resource to traditional water supply sources. Chlorination for wastewater, combined sewer overflows (CSOs), and reuse waters is the most common disinfection practice to ensure public health. Chlorinated wastewater effluent is a common reclaimed water for reuse applications such irrigation and mixing with source-area runoff during wet-weather events. Chlorine demand models have been developed for source waters and wastewaters. The current study adds to this knowledge base through modeling of sodium hypochlorite demand kinetics for source-area runoff PM and also dissolved phases utilizing dissolved chemical oxygen demand (CODd). Second-order rate models of hypochlorite demand are developed for both phases, with the PM phase subdivided into three fractions on a granulometric basis. PM (suspended, settleable, and sediment) fractions exert a significant hypochlorite demand compared with the dissolved fraction. Ultimate chlorine demand translates to 36% of the CODd, of which 39% of the demand is exerted in less than 5 min, which is in the range of residence times for small manufactured unit operations that are common for best management practices (BMPs). Chlorine demand is 350 mg/g for suspended, 320 mg/g for settleable, and 650 mg/g for sediment PM.

Statistical Modeling and Optimization of Reducing Sugar Production for Enzymatic Digestibility of Bamboo Grass by Box-Behnken Design Methodology

Bamboo plants are plants that can grow quickly and easily, and is an abundant and renewable resource plants analogous to deciduous tree and conifer. In this study, bamboo species of Yushania alpina was pretreated with sodium hydroxide (NaOH) and hydrolyzed by dilute sulfuric acid to produce reducing sugar. Phenol-sulphur acid method was used to determine the response. Seventeen experimental runs were carried out at temperature range (110-128oC), concentration of H2SO4 range of (1-7%) and residence time range of (30-60 min) respectively. The effect of the parameters was measured by concentration of reducing sugar produced for each, and the optimization of glucose production was done by using Box-Behnken design methodology. The results reveal that, the temperature, concentration and time significantly affected the glucose production. At range of low temperature, concentration and time, the yield was decreased while at high value of factors the yield of reducing sugar increased. At 113.17oC, 3.43wt%, 33.65min and desirability of 0.71 the optimum reducing sugar of 19.9 found.