Accurate Mass Balance Research Articles

Optimizing industrial flow measurements in mineral processing: Utilizing radiotracers for enhanced data reliability within Mining 4.0.

As the mining sector undergoes rapid transformation, Industry 4.0 principles — such as data digitalization, process automation, and Big Data Analytics — are crucial for developing intelligent mineral processing plants. These principles advance processes towards an interconnected sequence of steps, each relying on high-quality data. Within this framework, low-uncertainty flowmeter data is vital for accurate metallurgical mass balance determination, efficient process control, and the correct application of advanced analytical tools. However, harsh mining conditions can cause significant deviations in flowmeter readings, necessitating robust data validation methods. This paper introduces the novel application of the radiotracer methodology, which provides certified uncertainties around 1%, to optimize flowmeter data accuracy and align with Mining 4.0 requirements. Three industrial validation examples are presented: Flow meter adjustment in leaching processes, evaluating a NaHS loop piping circuit in a molybdenum flotation plant and validating flow meters to assess the hydraulic behavior of recirculation pumping stations for water balance quantification. On-site validations at the leaching plant revealed that only 36% of the measurements were within the acceptable 5% error margin. Flow assurance was confirmed in the NaHS loop piping circuit as radiotracer velocity data showed no blockages. Deviations in the recirculation pumping stations, ranging from 6.91% to 22.55%, highlighted the need for flowmeter adjustments. These findings underscore the value of radiotracers as a validation method. This paper also provides insights for water and environmental impact assessment, metallurgical mass balance calculations, and process optimization, emphasizing the need to integrate radiotracer methodology within the Mining 4.0 framework.

Controls on the stable Mo isotopic composition of inner-continental precipitation

The molybdenum (Mo) isotope budget of the surface environment has been well characterized in recent decades, facilitating accurate mass balance modeling of the ancient redox-driven Mo cycle. One yet unresolved component is the range of possible processes and sources that result in isotopically heavy river waters relative to continental sources. Following a recent hypothesis that isotopically heavy δ98Mo of precipitation may control the final δ98Mo of river water relative to its continental source bedrock, we investigated the δ98Mo composition of 19 snow samples from three locations in Central Europe: the Swiss Alps (“Alpine” samples) from the Hochalpine Forschungsstation Jungfraujoch (HFSJ) in both summer and winter, the Swiss Jura Mountains in winter and the French Vosges Mountains in winter. Stream waters from two snowmelt-fed streams were additionally collected from the Alpine site. Snow sample δ98Mo compositions were highly variable, ranging from −0.03 to +1.93 ‰, with no clear mixing trends indicating complex sources, source pathways, or post-depositional processing. Only the winter snow samples from the high-altitude HFSJ site had δ98Mo values consistently heavier than typical continental crust. The δ98Mo results were coupled with radiogenic Sr isotopic, major ion, and trace element compositions as tracers for three major sources of airborne ion inputs: sea salt, mineral dust, and anthropogenic aerosols. We found that the most likely source of Mo to precipitation in the lower elevation Vosges and Jura Mountains samples was isotopically light soil mineral dust, which reflected the underlying bedrock sources, with a likely additional anthropogenic component. The isotopically heavy winter snow samples at the elevated HFSJ site were attributed to a higher input of carbonate mineral dust from long-distance transport of carbonate-rich Saharan dust, which was overwritten in the summer by an influx of low elevation sources transported upwards during higher vertical thermal mixing. Finally, we concluded that precipitation has a negligible direct effect on the overall Mo content and isotopic composition of inner continental European streams and rivers relative to other sources, such as bedrock weathering. Future time-series studies may augment these conclusions to show possible heterogeneity of precipitation as well as the addition of sample sites closer to marine sources, where a larger flux of isotopically heavy marine aerosols to streams might be expected.

High-efficiency conversion of corn bran to ethanol at 150 L scale

Fractionated corn bran was processed to maximize ethanol production from starch, cellulose, and xylan. After various bench-scale experiments, an optimized process with dilute acid pretreatment (1.5 % w/w H2SO4) at 90 °C for 60 min was utilized followed by enzymatic hydrolysis using cellulase and hemicellulase for 48 hr. After simultaneous saccharification (regarding starch) and fermentation at 150 L using an engineered yeast, which consumes both glucose and xylose to make ethanol, the 86 % total sugar conversion yield was achieved, including conversions of 95 % for starch, 77 % for cellulose and 77 % for xylan. Also, an accurate mass balance was formulated for ethanol-producing carbohydrates including starch, cellulose, and xylan from feedstock to final ethanol. A highly efficient process of converting corn fiber to ethanol was successfully scaled up to 150 L.

Cadmium concentrations in pore waters can largely increase during soil incubation: Artefacts with consequences for Cd limits in fertilisers

A sound evaluation of the cadmium (Cd) mass balance in agricultural soils needs accurate data of Cd leaching. Reported Cd concentrations from in situ studies are often one order of magnitude lower than predicted by empirical models, which were calibrated to pore water data from stored soils. It is hypothesized that this discrepancy is related to the preferential flow of water (non-equilibrium) and/or artefacts caused by drying and rewetting soils prior to pore water analysis. These hypotheses were tested on multiple soils (n = 27) with contrasting properties. Pore waters were collected by soil centrifugation from field fresh soil samples and also after incubating the same soils (28 days, 20 °C), following two drying-rewetting cycles, the idea being that chemical equilibrium in the soil is reached after incubation. Incubation increased pore water Cd by a factor 4, on average, and up to a factor 16. That increase was statistically related to the decrease of pore water pH and the increase of nitrate, both mainly related to incubation-induced nitrification. After correcting for both factors, the Cd rise was also highest at higher pore water Ca. This suggests that higher Ca in soil enlarges Cd concentration gradients among pore classes in field fresh soils because high Ca promotes soil aggregation and separation of mobile from immobile water. Several empirical models were used to predict pore water Cd. Predictions exceeded observations up to a factor 30 for the fresh pore waters but matched well with those of incubated soils; again, deviations from the 1:1 line in field fresh soils were largest in high Ca (>0.8 mM) soils, suggesting that local equilibrium conditions in field fresh soils are not found at higher Ca. Our results demonstrate that empirical models need recalibration with field fresh pore water data to make accurate soil Cd mass balances in risk assessments.

Spatiotemporal variations in glacier area and surface velocity of the northern Antarctic Peninsula during 2018–2022

Ice sheet serves as a crucial indicator for assessing climate change. Mass loss in recent remote sensing-based studies indicated that the Antarctic Peninsula has rapid rates of glacier retreat and speed up of surface velocity. However, observations of seasonal variability of ice speed are limited, and glacier-area changes require multi-temporal monitoring. This study investigated the changes in area and surface velocities of ∼375 glaciers on the northern Antarctic Peninsula (NAP) utilizing satellite images acquired by the Sentinel 1&2 satellites during 2018–2022. The results indicate that the glacier area reduced by approximately 166.1 ± 44.2 km2 (−0.2% ± 0.1% per year) during the study period, with an acceleration after 2020 (−0.4% ± 0.3% per year), and the most dramatic reduction happened on the eastern NAP. The maximum annual ice speeds on the NAP generally exceeded 3500 m per year, while the ice speeds in 2021 were the highest (exceeded 4210 m per year). The ice speed variability in austral autumn was higher than in other seasons, meanwhile the summer ice speeds showed an increasing trend. The glacier G012158E47018N, McNeile Glacier, glacier G299637E64094S and Drygalski Glacier showed the most remarkable ice speed variations represented by high daily velocities and strong fluctuations on their termini. Our results demonstrated that the variations in glacier area and seasonal ice speed on the NAP were responsive to the ice–ocean–atmosphere processes. Therefore, seasonal velocity and area variations should be considered when conducting accurate mass balance calculations, model validations and change mechanism analyses under climate warming scenarios.

High-Cell-Density Yeast Oil Production with Diluted Substrates Imitating Microalgae Hydrolysate Using a Membrane Bioreactor

Microbial oil production from industrial waste streams and biogenic resources, such as biomass hydrolysates, is emerging as a sustainable alternative to use of fossil and vegetable oils. However, the carbon sources of these substrates are typically diluted, leading to low product concentrations and, therefore, high fermentation and downstream processing costs. In this study, high-cell-density yeast oil production with a defined medium, which imitated the sugar composition of a diluted substrate, a typical microalgal biomass hydrolysate, is carried out on a 50 L scale using a membrane bioreactor (MBR) consisting of a microfiltration unit suited for industrial application. The process was run on a semi-continuous mode to reduce operational costs. Oleaginous yeast Cutaneotrichosporon oleaginosus was used as a biocatalyst and lipid production was induced by phosphate deficiency in the medium with a C/P ratio of 3515 g g−1. In this way, high cellular lipid contents of up to 76.5% (w/w) of dry cell mass, an average lipid yield of 32% (w/w), and a lipid space–time yield (STY) of up to 8.88 g L−1 d−1 were achieved with final high cell densities of up to 116 g L−1 dry biomass. Furthermore, use of a defined medium and elemental analysis of the yeast cells and yeast oil enabled drawing an accurate carbon mass balance of the production system. Carbon conversion efficiencies—fraction of total carbon supplied in the form of sugars converted into lipids at the end of the process—of up to 61.5% were achieved from diluted substrates using the MBR with total cell retention. Considering these results, it is concluded that utilization of an MBR on a semi-continuous mode would be very reasonable for yeast oil production, enabling high productivities with diluted sugar substrates.

Suitability of nitrogen fractions determination to assess serum protein separation efficiency from a mass balance perspective during microfiltration of skim milk

Efficient separation of serum from colloidal proteins in bovine milk in their native form can be achieved by microfiltration (MF). This study assessed partitioning of serum proteins (SP) in skim milk by a MF process using 0.1 μm graded permeability ceramic membranes with two diafiltration (DF) steps, from a mass balance and energy utilisation perspective. A mass balance focused on dry matter and true protein yielded recoveries of 99.5 and 95.3%, respectively. However, an accurate mass balance relative to colloidal and SP contents in the retentate and permeate streams was not achieved, linked to errors surrounding quantification of nitrogen fractions in processed streams using standard methodologies designed for raw milk. Additionally the energy required for each MF/DF step was 13.1, 13.7 and 20.6 kW h kg−1 of SP removed, respectively, demonstrating the dynamic relationship between SP partition relative to diafiltrant utilisation and its impact on energy consumption.

An original Arduino-controlled anaerobic bioreactor packed with biochar as a porous filter media

Bioreactors are commonly used apparatuses generally equipped with several built-in specifications for the investigation of biological treatment studies. Each bioreactor test may require different types of specialty such as heating, agitation, re-circulation and some further technologies like online sensoring. Even thought, there are many ready-to-use fabricated bioreactors available in the market with a cost usually over than 1000 €, it is often not possible to access those advanced (but inflexible) systems for many students, young-researchers or small-scale private R&D companies. In this work, a new low cost (≈100€) packed-bed anaerobic bioreactor was developed, and all methodological details including open-source coding and 3D design files are shared with informative descriptions. Some preliminary tests were conducted to verify the developed bioreactor system's credibility in terms of leak-tightness, accurate gas monitoring, temperature controlling, and mass balance (COD-eq) coverage, which all have shown a very promising performance.•A consistent model bioreactor that will be called as “tetrapod” was developed for anaerobic treatment of challenging substrates such as pyrolytic liquids.•Coarse biochar grains were used as an organic packing material to stimulate the microbial bioconversion by increasing the active surface area for the attached-growth anaerobic mixed microbial culture (MMC).•An open-source Arduino based digital gasometer was developed for online monitoring of biogas change in the lab-scale system. Arduino was also used as a digital controller for maintaining pulse-mode liquid recirculation of the bioreactor.

Fate of phosphorus from treated wastewater in soil-based constructed wetlands

In France, soil-based constructed wetlands for the discharge of treated wastewater have become a popular technique to both reduce flow to surface receiving water bodies and perform complementary treatments. This study focuses on the fate of phosphorus in three different soils, as well as its assimilation by Phragmites australis. The experimental set-up consisted of three lysimeters containing three soils selected to be representative of those typically found near wastewater treatment plants (i.e. a silt loam Fluvisol, a sandy loam Fluvisol and a sandy-clay loam Technosol). Lysimeters are undisturbed soil monoliths (1.5 m3 in volume), whose masses are continuously monitored in order to obtain an accurate water mass balance. The lysimeters here were intermittently fed for 3.5 days and then left to rest for 3.5 days. The experiment lasted 26 months, including 18 months of feeding with phosphorus (PO4-P, TP) fluxes in and out being monitored along with water content, oxygen content and redox potential at various depths. The quantities of phosphorus stored in the soils and assimilated in the Phragmites australis were measured. Phosphorus fractionation in soils was performed to better understand its distribution and potential remobilization. Low phosphate concentrations were measured at the outlets of all three lysimeters, thereby highlighting satisfactory phosphorus retention in the three soils (removal efficiencies >90%). A significant amount of phosphorus can be exported by harvesting Phragmites australis aerial parts (26%, 17% and 13% of the yearly incoming phosphorus mass for the silt loam Fluvisol, sandy loam Fluvisol and sandy-clay loam Technosol, respectively). The fractionation step served to determine that the phosphorus retained in the soil was primarily bound to iron oxides/hydroxides, calcium and clay. Moreover, it was found to be preferable to hold oxidizing (aerobic) conditions and pH close to neutral in order to maintain conditions under which the complexes formed with phosphorus remain stable.

Tracing the Atmospheric Input of Seawater-Dissolvable Pb Based on the Budget of 210Pb in the East Sea (Japan Sea)

In order to determine the atmospheric input of 210Pb and seawater-dissolvable Pb in the East Sea (Japan Sea), we measured the concentrations of total 210Pb and dissolved Pb (<0.2 μm) in seawater and 210Pb and 226Ra in sinking particles. The East Sea is deep (∼3700 m) and enclosed by surrounding continents except for the shallow sills (<150 m). Since the East Sea is located off the East Asian continent under the westerlies, the concentrations of 210Pb and dissolved Pb in this sea are significantly affected by terrestrial sources through the atmosphere. The vertical profiles of total 210Pb and dissolved Pb generally showed a surface maximum and then decreased with depth. The concentrations of dissolved Pb in the surface water were 2 and 3 times higher than those in the North Pacific and North Atlantic Oceans, respectively. Using an independent box model (upper 1000 m or 2000 m), we estimate the atmospheric input of 210Pb to be 1.46 ± 0.25 dpm cm−2 y −1, which is within the range of published results from the land-based sites (0.44–4.40 dpm cm−2 y −1) in South Korea, China, and Japan. Based on this flux, the residence time of total 210Pb in the East Sea is calculated to be approximately 7.1 ± 1.6 years, which is twice lower than the previous estimation. Combining the residence time of 210Pb and the inventory of dissolved Pb, the atmospheric input of seawater-dissolvable Pb is estimated to be 0.98 ± 0.28 nmol cm−2 y −1. This flux is approximately 25% of the Pb flux through the wet deposition (acid-leachable fraction). Thus, our results suggest that the flux and fate of atmospheric Pb in the ocean can be successfully determined using an accurate mass balance model of naturally occurring 210Pb.

An investigation of nonlinear time-fractional anomalous diffusion models for simulating transport processes in heterogeneous binary media

In this work, we consider two of the most frequently used two-dimensional nonlinear time-fractional anomalous sub-diffusion models for simulating transport phenomena in heterogeneous binary media—a variable-order model and a generalised transport equation based on the Riemann-Liouville fractional operator. Our computational modelling framework uses a second order modified weighted shifted Grünwald-Letnikov scheme with correction terms to approximate the time-fractional derivative and nonlinear source term, together with an unstructured mesh control volume method for the spatial discretisation that accommodates the heterogeneous model properties. The resulting nonlinear system of algebraic equations is then stepped in time using an efficient Jacobian-free, Newton-Krylov solver to determine the set of discrete solution unknowns. We derive a semi-analytical solution and mass balance equation for a class of two-layered problems to evaluate the accuracy of the different computational models. A key contribution of our work is to identify the correct form of the interfacial boundary conditions to impose for the flux terms within the time-fractional framework and to illustrate the significant impact that the time-fractional indices have on the mass transfer. We show that the generalised transport model not only exhibits the correct physical solution behaviour, it produces a more accurate overall mass balance in comparison to the variable-order time-fractional model which is unable to resolve the abrupt changes in the solution behaviour at the interface between two different media having contrasting diffusivity, fractional index and source term. This finding indicates that this generalised model is an effective tool for characterising anomalous transport processes in heterogeneous systems. Finally, a series of numerical examples are presented to verify the theoretical analysis and to highlight the capability of the generalised transport model.

Practical Application of the Galerkin Finite Element Method with a Mass Conservation Scheme under Dirichlet Boundary Conditions to Solve Groundwater Problems

The Galerkin finite element method (FEM) has long been used to solve groundwater flow equations and compute the mass balance in a region. In this study, we proposed a simple, new computational FEM procedure for global mass balance computations that can simultaneously obtain boundary fluxes at Dirichlet boundary nodes and finite element hydraulic heads at all nodes in only one step, whereas previous approaches usually require two steps. In previous approaches, the first step obtains the Galerkin finite element hydraulic heads at all nodes, and then, the boundary fluxes are calculated using the obtained Galerkin finite element hydraulic heads in a second step. Comparisons between the new approach proposed in this study and previous approaches, such as Yeh’s approach and a conventional differential approach, were performed using two practical groundwater problems to illustrate the improved accuracy and efficiency of the new approach when computing the global mass balance or boundary fluxes. From the results of the numerical experiments, it can be concluded that the new approach provides a more efficient mass balance computation scheme and a much more accurate mass balance computation compared to previous approaches that have been widely used in commercial and public groundwater software.

On-line recovery system coupled to a Rock-Eval® device: An analytical methodology for characterization of liquid and solid samples

The Rock-Eval® device has been widely used to identify the type and the thermal maturity of sedimentary organic matter, as well as for quantifying the total organic carbon content. Traditionally, it is a screening tool to estimate the petroleum generation potential of source rocks using standardized parameters. More recently, a new Rock-Eval® method (Shale Play™) was proposed for the investigation of the hydrocarbon content of liquid-rich tight rock samples. In this study, we describe a dual vacuum and on-line system that was developed to recover most compounds that are thermally released during a Rock-Eval® Shale Play™ analysis. Thermally vaporized products are divided so that half is analyzed by the Rock-Eval® flame ionization detector (FID) while the other portion is cryogenically trapped in the on-line recovery system. The trapped products can then be transferred via a vacuum line system into a sample vial for subsequent molecular and/or isotopic composition analyses. The recovery vacuum line volumes were calibrated using known quantities of gas (CH4 and CO2). Sample transfer without isotopic fractionation was demonstrated for CO2 evolved from Rock-Eval® preparation of pure carbonate standards (siderite, magnesite and azurite). Recovery efficiencies were first measured on C8-C16n-alkane standards and then on produced oil samples. Results indicate a high quantitative recovery and an accurate mass balance of most compounds released during the Shale Play™ Sh0 thermovaporization step (100–200 °C). Thermally vaporized compounds released at higher temperatures Sh1 (200–350 °C) are recovered at lower efficiencies, but are still suitable for subsequent characterization. The coupled Rock-Eval® and recovery system could have applications beyond petroleum geochemistry.

Direct measurement of selected soil services in a drained agricultural field: Methodology development and case study in Saclay (France)

Over the last decade, many researchers around the world have realized the importance for society of the many services provided by soils, and a significant body of research has been devoted to estimating them using various types of proxies or relying on models. However, the field has suffered so far from a complete lack of actual measurements with which to evaluate available estimation methods. In this context, the key objective of the present research was to obtain, for the first time, direct measurements of several services provided by soils. The experimental site at which the research was carried out is an agricultural field located southwest of Paris (France), which presents the unique advantage that is it artificially drained, and therefore allows accurate mass balances to be computed over time for rain water, nutrients, and herbicides applied to the soil. A detailed methodology is presented to extract, from these data, quantitative measurements of 3 provisioning services (supply of water to nearby stream, provision of food by supplying, respectively, water and nitrogen to wheat crop), and 3 regulating services (flood mitigation, and filtration of, respectively, nutrients and herbicides). The results obtained with this methodology, and the relative significance of the different services are discussed. In particular, it is shown that, given the industrial-type of agriculture practiced at the site and its heavy reliance on fertilizers, the service related to the supply of nitrogen to the crops by the soil is not marginal, accounting for 22% of the total nitrogen consumption by the wheat. The availability of quantitative measures of selected soil services now paves the way for a detailed assessment of the various estimation methods currently in use, and the development of improved approaches.

Effect of glycerol thermal and hydrothermal pretreatments on lignin degradation and enzymatic hydrolysis in paddy straw

The selection of effective pretreatment method for exploiting lignocellulosic biomass plays an important role for sustainable biofuel production as it accounts the highest share of production cost. The present study aims to compare the efficiency of glycerol thermal pretreatment (GTP) over hydrothermal and alkali pretreatments of paddy (rice) straw as a feedstock. The efficacy of pretreatment was assessed by analyzing the reducing sugar (RS) yield, holocellulose digestibility and component degradation. The study was further elaborated for enzyme kinetics, FTIR spectra, crystallinity, accurate mass and energy balance. GTP showed 71.52% RS yield with 94.36% holocellulose digestibility, which was higher than that of alkali and hydrothermal pretreatments. GTP was more effective in lignin and hemicellulose removal with little damage to cellulose. The enzyme kinetic study further proved the effectiveness of GTP and showed the enhanced enzyme adsorption and hydrolysis on exposing enzyme binding sites. Crystallinity of cellulose revealed the effectiveness of GTP by XRD studies. FTIR study gives emphasis on alteration in lignocellulose structure due to pretreatment. The mass and energy balances further confirmed the reliability of GTP pretreatment.

Carbon isotopes in clastic rocks and the Neoproterozoic carbon cycle

It has been proposed that isotopically light inorganic carbon precipitated diagenetically in clastic sediments can explain the large carbon isotopic excursions recorded in Neoproterozoic carbonates. To date, however, the data needed to test this hypothesis have been limited. Here we report the analysis of ca. 540 clastic sedimentary rocks, including shales, siltstones, sandstones and tillites, that span the second half of the Neoproterozoic Era. A diagenetic carbon isotopic overprint does indeed occur in many of the samples; however, when we include our analyses in a carbon isotope mass balance model, they produce only a small effect on mass balance model results. Thus, clastic sedimentary rocks were not a major sink for 13C-depleted carbonate during the Neoproterozoic Era. These results do, however, produce a more accurate carbon mass balance, pointing to a high proportion of total organic carbon burial, compared to total carbon burial, during the late Tonian, Cryogenian, and late Ediacaran Periods. This result suggests a vigorous release of oxygen to the atmosphere. The clastic carbonate record also offers a chemostratigraphic tool. For example, we observe an isotope trend in clastic-hosted carbonates of the Isaac Formation, Windermere Supergroup, that strongly resembles the Shuram-Wonoka isotope anomaly, allowing us to place this previously undated section in a temporal context. We also find isotope trends in the fossiliferous and radiometrically well-dated sedimentary rocks of the Avalon Peninsula, Newfoundland, that may also reflect the Shuram-Wonoka anomaly. If correct, this constrains the timing of the Shuram event, suggesting that it began after 571 Ma and ended before 562 Ma, with the most extreme isotopic values lying well within those bounds.

Eemian Greenland ice sheet simulated with a higher-order model shows strong sensitivity to surface mass balance forcing

Abstract. The Greenland ice sheet contributes increasingly to global sea level rise. Its history during past warm intervals is a valuable reference for future sea level projections. We present ice sheet simulations for the Eemian interglacial period (∼130 000 to 115 000 years ago), a period with warmer-than-present summer climate over Greenland. The evolution of the Eemian Greenland ice sheet is simulated with a 3-D higher-order ice sheet model, forced with a surface mass balance derived from regional climate simulations. Sensitivity experiments with various surface mass balances, basal friction, and ice flow approximations are discussed. The surface mass balance forcing is identified as the controlling factor setting the minimum in Eemian ice volume, emphasizing the importance of a reliable surface mass balance model. Furthermore, the results indicate that the surface mass balance forcing is more important than the representation of ice flow for simulating the large-scale ice sheet evolution. This implies that modeling of the future contribution of the Greenland ice sheet to sea level rise highly depends on an accurate surface mass balance.

Predictive Equations for Butterhead Lettuce (Lactuca Sativa, cv. Flandria) Root Surface Area Grown in Aquaponic Conditions

Aquaponic systems are becoming more prevalent and have led to accurate mass and energy balance models that allow nutrient utilization to be maximized and plant and fish systems to be coupled or complimentary. Such models still do not address the potential of using the plant side as both the primary nitrification system and as a sink for the nitrate being produced from the fish system. However, using the plants as the nitrification system for the fish waste requires a better understanding and quantification of the nitrification capacity of the plant system. A series of experiments were conducted using butterhead lettuce (Lactuca sativa, cv. Flandria) in deep water culture rafts. Plants were grown under two growing conditions and were evaluated based upon harvestable weight. Treatment 1 (H5) consisted of a standard hydroponic nutrient solution maintained at pH 5.8, while treatment 2 (A7) consisted of an aquaponic waste solution maintained at pH 7.0. The aquaponic conditions were created from a fish rearing system using koi (Cyprinus carpio) that was continuously recirculated between the designated plant tubs and the fish tank with an in-line bead filter to capture and mineralize fish solids. The total root surface area was not significantly different between treatments, but the ratio of root surface area to root fresh weight was different, suggesting that aquaponic roots are finer than hydroponic roots. Predictive equations were developed to correlate root surface area to shoot or root fresh weight, which can be used to design the nitrification component for a recirculating aquaculture system (RAS), as part of an integrated aquaponic system.

Integrating data reconciliation into material flow cost accounting: The case of a petrochemical wastewater treatment plant

Material flow cost accounting analyzes input/output relations of material flows in the production process based on mass balance principles. However, the measured data of a process contains errors representing a mass imbalance in the system such as that of a wastewater treatment plant. Therefore, measured data should be verified before establishing mass balance and, subsequently, material flow cost accounting. Hence, in this work, a novel practical stepwise methodology using data reconciliation technique is introduced to improve the accuracy and certainty of measurements before material flow cost accounting. A full-scale petrochemical wastewater treatment plant was selected to establish this methodology. The presented results of this case study show an error of −3.22% (−35244 t/year) between total input and output streams of wastewater treatment plant demonstrating mass imbalance in the system. However, the overall mass balance could be closed by simultaneously solving the incidence matrix (system of balances). The results revealed that by including data reconciliation into material flow cost accounting, an accurate mass balance can be performed, which is a key element in material flow cost accounting calculations. The comparison results showed a relatively significant difference between material flow cost accounting for reconciled and measured data (unreconciled). The developed approach provides a reliable set of data for implementing material flow cost accounting in the system. Therefore, using this novel stepwise approach will help decision-makers to enhance both financial and environmental performances more confidently and to define appropriate improvement plans.

Global sea-level contribution from Arctic land ice: 1971–2017

The Arctic Monitoring and Assessment Program (AMAP 2017) report identifies the Arctic as the largest regional source of land ice to global sea-level rise in the 2003–2014 period. Yet, this contextualization ignores the longer perspective from in situ records of glacier mass balance. Here, using 17 (>55 °N latitude) glacier and ice cap mass balance series in the 1971–2017 period, we develop a semi-empirical estimate of annual sea-level contribution from seven Arctic regions by scaling the in situ records to GRACE averages. We contend that our estimate represents the most accurate Arctic land ice mass balance assessment so far available before the 1992 start of satellite altimetry. We estimate the 1971–2017 eustatic sea-level contribution from land ice north of ∼55 °N to be 23.0 ± 12.3 mm sea-level equivalent (SLE). In all regions, the cumulative sea-level rise curves exhibit an acceleration, starting especially after 1988. Greenland is the source of 46% of the Arctic sea-level rise contribution (10.6 ± 7.3 mm), followed by Alaska (5.7 ± 2.2 mm), Arctic Canada (3.2 ± 0.7 mm) and the Russian High Arctic (1.5 ± 0.4 mm). Our annual results exhibit co-variability over a 43 year overlap (1971–2013) with the alternative dataset of Marzeion et al (2015 Cryosphere 9 2399–404) (M15). However, we find a 1.36× lower sea-level contribution, in agreement with satellite gravimetry. The IPCC Fifth Assessment report identified constraining the pre-satellite era sea-level budget as a topic of low scientific understanding that we address and specify sea-level contributions coinciding with IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) ‘present day’ (2005–2015) and ‘recent past’ (1986–2005) reference periods. We assess an Arctic land ice loss of 8.3 mm SLE during the recent past and 12.4 mm SLE during the present day. The seven regional sea-level rise contribution time series of this study are available from AMAP.no.