Compact Treatment Research Articles

Anisotropy of subsoil pore characteristics and hydraulic conductivity as affected by compaction and cover crop treatments

AbstractThe natural and cover crop (CC)‐induced anisotropy of subsoil pore characteristics is important in assessments of soil compaction but, until recently, has received limited attention. This study aims to quantify the anisotropy of soil pore characteristics and hydraulic conductivity in subsoils subjected to compaction and CC treatments in a split‐plot field experiment on temperate sandy loam soils. The main factor was ±compaction and the split‐plot factor was ±CC with fodder radish (Raphanus sativus L.). The compacted plots were heavily trafficked for 4 yr (2010–2013). After 4 yr under CC (2013–2016), core samples were collected at 0.3 m. The samples were taken vertically and horizontally to quantify the anisotropy of air‐filled porosity (εa) and air permeability (ka), saturated hydraulic conductivity (ksat), and bulk density (ρb). The results showed isotropic behavior for ρb and εa and significant anisotropic behavior (p < .05) for ka, pore geometry index (PO1) (ka/εa), ratio of non‐Darcian to Darcian ka (R‐ratio), and ksat. For parameters with significant anisotropy, higher values occurred vertically than horizontally for all compaction –CC combinations, except for R‐ratio. This indicates that pre‐existing vertical continuous pores dominated the pore system in the control subsoil. A nonsignificant trend of higher values of ka, PO1, and ksat in the +CC than in the compacted –CC plots suggest that CC could contribute to the formation of vertical biopores. Including an autumn CC in rotation with a summer cereal crop for a longer period may significantly affect the anisotropy of the soil pore and hydraulic properties.

Development of New Compact Water Treatment System for Flue-Gas Condenser for Households

Abstract This work is a continuation of the article “Methods for Determining the Performance and Efficiency Parameters of the Flue-gas Condenser Sedimentation Tank”. During the experimental determination of Particulate Matter (PM) physical parameters, a described methodology was used. The results obtained affected the choice of water purification technology. Sedimentation technology was selected but provided that a filter element should be present in the installation. The article describes the types of industrial sedimentation tanks used more often. In condition that the system should be compact, while at the same time the purification efficiency rate should be high, the new suitable design of the water treatment system was developed.

Research on Present Situation and the New Technology About Reinforcement in Collapsible Loess Foundation Inside Tunnels

The tunnel foundations treatment is the key and difficult point of the research of the tunnel in collapsible loess areas. The characteristics and advantages of the common foundations treatment technology for tunnels of loess areas are summarized in this paper, at the same time, the characteristics of a new technology for the non-vibration compaction treatment technology developed by the Northwest Research Institute Co., Ltd. of China Railway Engineering Corporation are introduced, which is suitable for the foundation reinforcement treatment of the tunnel in collapsible loess areas. Through the field experiment of base treatment of high-speed railway tunnel of the Baoji–Lanzhou High-Speed Railway Passenger Dedicated Line, it is demonstrated that the new non-vibration compaction machine has the advantages of convenient movement, controllable treatment effect, miniaturization, low cost and so on. The advancement and maneuverability are verified from the soil compaction coefficient between piles and the change law of collapsibility of the soil between piles under the different pile spacing conditions. The research results can provide new techniques and methods for the foundation reinforcement treatment of the tunnel of small space, strictly controlling construction vibration in collapsible loess areas.

Subsoil compaction effect on spatio-temporal root growth, reuse of biopores and crop yield of spring barley

Subsoil compaction in arable farming caused by increasingly heavy machinery results in increased subsoil strength and reduced aeration and water flow. This can restrict root growth and reduce crop yield. To mitigate these effects of subsoil compaction, we included a deep-rooted catch crop of fodder radish (Raphanus sativus var. oleifera) in a rotation of spring barley (Hordeum vulgare). The objective was to determine the effect of subsoil compaction on root growth and grain yield of barley, and to investigate the creation and use of biopores for subsequent root growth. Studies were carried out in 2013–2016 in a soil compaction experiment established in 2010 on a sandy loam. The soil had for four consecutive years (2010–2013) been compacted with multi-passes in an 8 Mg wheel load treatment (M8) or had not been compacted (Control). Spring barley was grown every year and fodder radish was grown as a catch crop from harvest to winter in 2013–2016. Penetration resistance to 90 cm depth was measured in 2015 at a soil water content near field capacity. Root growth and biopore reuse were investigated using horizontal minirhizotrons installed at 30, 50 and 70 cm depth from 2013–2016. Spring barley grain yield was recorded annually. We found that M8 caused critical subsoil compaction with penetration resistance peaking at 3.5 MPa in the upper subsoil (30−40 cm depth). Subsoil compaction reduced root growth by c. 50 % at 30 cm depth and barley yields by 6–8 % compared to the Control in three years after cessation of the compaction treatment. The number of biopores that were reused were higher for fodder radish than for spring barley, 4.1 % and 3.1 %, respectively, but did not differ between compaction treatments. Our study displayed a marked, negative residual effect of soil compaction on above- and belowground crop growth. There was no tendency towards a recovery within the years studied (1–3 years after compaction). Severe subsoil compaction is a widespread problem and therefore we call for more studies on the spatio-temporal dynamics of the creation and subsequent use of biopores for root growth as these are essential for the recovery of compacted subsoils.

The Technologies Optimization for the Treatment of Underground Water with Iron and Arsenic Content – A Case Study

Generally, in Romania, the water treatment aimed at removing the classic compounds of iron, manganese, ammonium, nitrates / nitrites, etc. by the known classical technologies (chemical coagulation, precipitation, decantation, slow / fast filtration with free / under pressure, disinfection). When in the raw water, besides the classical compounds, heavy metals semi-metals are also found, together with the classical treatment technologies, advanced technologies are required combined, known as hybrid processes (Electro-coagulation / EC, oxidation, adsorption / exchange ions, membrane filtration -UF / NF / RO), which can lead to the desired results. Along with iron, manganese, ammonium, nitrites / nitrates, arsenic is a naturally occurring element in the Earth’s crust. Arsenic in drinking water is a global problem affecting the population worldwide because the arsenic and its components have carcinogenic properties. Regarding the elimination of arsenic (As) found in the water especially collected from the underground, the studies and researches applied were much more restricted and the applications completely isolated, at present the subject being more intensely approached. This situation is also caused by the fact that the Water Framework Directive no.98_83_CEE, transposed into national legislation, lowered the Arsenic (As) chemical indicator limit to 10 μg As / L (from 50 μg As / L). An alternative / complementary technology with low maintenance costs for underground treatment is Electro-oxidation/coagulation (EC), which has been of increasing interest in the last decade. The use of pilot stations / equipment for studying potential treatment technologies is essential for optimizing the treatment schemes and in order to avoid the implementation of costly technologies that cannot work for various reasons. In this case study, it was analysed comparatively from the efficiency point of view combining and optimizing oxidation-coagulation-filtration technologies in a pilot station for water treatment with iron, manganese and arsenic content, coming from the medium depth underground source (western Romania). In the initially provided technological flow (oxidation with ozone, multimedia filtration and disinfection with hypochlorite for the remanence), an electro-coagulation / oxidation (EC) cell was introduced upstream of the multimedia filter. This process aimed at eliminating the use of chemicals (ferric chloride) from the coagulation process that would have caused the rapid alteration of the multimedia filter and consequently increased operating costs. The results showed that compared to conventional technologies, the EC advantage includes high disposal efficiency, a compact treatment plant and the possibility of complete automation.

Beam Characteristics of the First Clinical 360°-rotational Compact Scanning Pencil Beam Proton Treatment System and Comparisons against a Multi-Room System

This paper is to present the dosimetric characteristics of the first clinical CBCT guided 360˚-rotational compact/single-room scanning pencil beam proton treatment system (SRPT) and comparisons against a recent beam data from a multi-room proton therapy system (MRPT) by the same vendor. The proton beam commissioning was conducted on the first clinical, newly-designed compact ProBeam 360˚ for its scanning pencil beams for protons ranging from 70MeV to 220MeV. The integrated depth dose curves (IDDs) were acquired in water with AP monogenic proton beams using a PTW Bragg peak chamber. The dose output factors, measured by a Marcus chamber at 15 mm transmission beam portion using single layer 10x10 cm2 proton plans, were then incorporated to the iDD's along with a factor of 1.1 for RBE offset. The beam spot sigma sizes were then derived from single Gaussian fitting for the in-air measured spot profiles. After beam modeling and validation for a treatment planning system, the proton dosimetric characteristics were compared against the recent data of MRPT. In contract to MRPT data, the Bragg peaks of SRPT have shown moderately extended proton beam range straggling in the peak region accompanied by a marginally elevated proximal transmission beam portion. This phenomenon displayed more noticeably in the mid-ranged or even high energies. Consequently, IDDs of SRPT showed about 0.41 to 0.94 mm broader Bragg peak widths (Rb80 - Ra80) in energies of 140 MeV or greater, peaked at 180 MeV. About 0.65-0.79 mm slightly extended distal falloffs (Rb20-80) were noticeable for energies between 140 MeV and 170 MeV, consistent with the findings of minimally raised energy sigma in AcurosPT Monte Carlo model. An independent check for the dose and energy accuracy of a spread-out Bragg peak plan on a simple phantom by the IROC showed 1.00 accuracy with 1.00 ±5% allowance. Additional comprehensive end-to-end independent check using a more realistic prostate phantom offered by IROC was reported a 96% accuracy and the passing score at a set passing criterion of 85%. The result over 108 patient specific individual field QAs with Octavius 1500 2D ionization chamber array showed 100% passing rate using a Gamma index of 3%/3mm or tighter from fields with or without range shifters. The high QA passing rates suggest a high confidence on the accuracy and quality of the commissioning for the newly designed SRPT. The commissioning results of the new-designed SRPT showed slightly widened proton Bragg peaks, elevated beam transition region and extended peak distal falloffs, particularly in mid-high energies, suggest minimally broader spectra for selected proton energies in comparing against MRPT data. This did not show a meaningful impact on the quality and accuracy of proton therapy program, indicated by high scores from independent dosimetry end-to-end checks and over 108 patient’s specific beam QA’s.

Precrops alleviate soil physical limitations for soybean root growth in an Oxisol from southern Brazil

The impact of soil compaction on soybean root growth and grain yield can be alleviated by the presence of biopores and root channels in the soil profile. We hypothesize that cover crops (ruzigrass and oats) are better than grain crops (wheat and maize) to reduce the soil physical limitation to soybean root growth. We aimed to identify which precrops have higher potential to reduce the mechanical and water stresses resulting from soil compaction and soil desegregation, and to enhance soybean (Glycine max L) root growth and yield in an Oxisol (Rhodic Eutrudox), with clayey soil texture. Soybean was grown after four precrops (ruzigrass, oats, wheat, or maize), under four soil compaction levels [soil chiselling (MTC), no-tillage (NT), NT additionally compacted with four passes of a tractor (NTCT), and NT additionally compacted with eight passes of a grain harvester (NTCH)]. Soil physical attributes (bulk density, macroporosity, water-filled pore space and soil penentration resistance) in the soil profile (0−50 cm) and soybean components (grain yield, cumulative root length density and root dry mass) were investigated. Soil physical attributes were improved over time due to the combined effects of natural wetting-drying cycles and biopores created by the roots of precrops. Ruzigrass increased soybean root biomass and length density, mainly at deeper soil layers of compacted treatments (NTCT and NTCH). The rate of increase of soybean root length density in the soil profile was higher after ruzigrass cultivation in comparison with maize and oats. Soil compaction effects on grain yield were partially (NTCH) or totally (NTCT) alleviated after two years and ruzigrass intensified the mitigation process. Ruzigrass also resulted in higher soybean yields in comparison with maize, whereas NTCH and MTC reduced yields in approximately 400 kg ha−1 (∼13 %) compared to NT and NTCT. Soil strengthening was more evident after ruzigrass and oats cultivation than maize or wheat cropping. Soil compaction in clayey Oxisols can be alleviated over time as a result of root channels provided by precrops combined with natural wetting-drying cycles. Among the evaluated precrops, ruzigrass is of particular interest, as it provides the most suitable soil physical environment for soybean root growth and grain yield. In contrast, chiselling was demonstrated to be a non-viable strategy to mitigate soil physical constraints for root growth and grain yields.

Effect of subsoil compaction on rooting behavior and yields of wheat

Soil compactions are widely dispersed in the world but tend to be the most prevalent, where heavy machinery is used in agriculture. The increasing use of heavy machinery is the primary cause of soil and subsoil compaction. The impact of subsoil compaction on root growth and yield of wheat (Triticum aestivum L) were evaluated during 2006 and 2007. Sub-soil compactions were created by three normal loads, i.e. 4.40, 6.40 and 8.40 kg and four number of passes of tractor, i.e. 1, 6, 11 and 16. The field was divided into 39 plots including a control plot, i.e. no passes of the tractor. The size of each plot was 400 square meter. A factorial randomized block design was followed in laying out the experiment and care was taken that all the 13 treatments and their replications are included in field experiments. It was observed that for all the compaction treatments in the field experiment on the wheat crop, 51–61% of wheat roots were confined in 0–15 cm, 17–20% in 15–30 cm and the rest 22–28% is below 30 cm soil layer. Sub-soil compaction reduced the wheat crop yields to a maximum of 23%. A statistical model is developed to predict crop yield considering the root length density of the crop. Average root diameters increased with the increase of the sub-soil compaction level. In sub-soil zone, average root diameter decreased with the increase of sub-soil compaction level.

Variation of soil moisture and fine roots distribution adopts rainwater collection, infiltration promoting and soil anti-seepage system (RCIP-SA) in hilly apple orchard on the Loess Plateau of China

Improving the utilization efficiency of rainwater resources was a key issue for apple orchards in semi-arid areas. The RCIP-SA system combined rainwater collection systems, infiltration promoting tube and soil anti-seepage layer to gather limited rainwater resources into the soil layer where the roots of apple tree were concentrated. To evaluate the effect of the RCIP-SA system on soil moisture change and fine root distribution, a field experiment was completed in a hilly apple orchard on the Loess Plateau of China from 2017 to 2019. The results showed that the soil moisture of the RCIP-SA system was 24.0–43.9% higher than CK in the 0–60 cm soil layer in the rainwater collection ditch, and generated a larger area with higher moisture content near the impermeable layer during the apple tree growth period. The RCIP-SA system also expanded the dense distribution zone of apple tree roots. The dry fine root densities of apple trees in the RCIP-SA system in the 0–200 cm soil layer was 11.7–59.6% and 18.2–30.3% higher than CK under the plastic film (60 cm from the trunk) and edge of the rainwater collection ditch (100 cm from the trunk), respectively. Soil moisture and root distribution of apple trees were significantly different under different impermeable layers, and compacted red clay as the impermeable layer was the best anti-seepage strategy in RCIP-SA systems. The RCIP-SA system brought higher economic benefits; the average yield per tree was recorded for red clay compaction treatment (38.1 kg·tree−1), equating to a production level of 22 800 kg·ha−1, and a difference of 9.6 kg·tree−1 with CK treatment, equating to 5700 kg·ha−1. This strategy should be recommended as an agricultural measurement for apple production on the Loess Plateau of China.

A simplified treatment of neutron slowing by elastic collisions

An approximate treatment of neutron slowing by elastic collisions with nuclei of a moderating material in a nuclear reactor is developed on the basis of a compact treatment of elastic collisions previously published in this journal [B. C. Reed, Am. J. Phys. 86(8), 622 (2018)]. The analysis is straightforward enough to be presented to lower-level students and gives results in good accord with more sophisticated treatments.

Estação de tratamento de esgoto compacta para tratamento de efluentes de banheiros químicos: Um estudo de caso sobre eficiência do sistema, em uma obra executada em Bom Jesus das Selvas - MA

O processo de tratamento de efluentes sanitários é um mecanismo que depende da análise de variáveis técnicas e demográficas para a especificação do sistema de tratamento mais adequado à demanda atrelada à eficiência de remoção de carga orgânica requerida e o uso que se pretende dar ao efluente tratado. Dessa forma o objetivo do presente estudo de caso, é avaliar a eficiência de um sistema compacto de tratamento de efluentes sanitários, especificado e implantado, para atender uma demanda bruta com contribuição de 71% dos efluentes gerados em frentes de obras por banheiros químicos, tendo como premissas a implantação de equipamento com característica de tratamento aeróbio, com sistema de lodo ativado. A metodologia utilizada baseou-se no levantamento bibliográfico de referência, com a compilação de dados técnicos dos projetos de engenharia executados e normas associadas, realizando análise das taxas de tratabilidade do sistema, através dos resultados obtidos por laudos de monitoramentos realizados durante o ano de 2015. Como resultados, conseguiu-se observar o enquadramento dos parâmetros pH, temperatura, materiais sedimentáveis, materiais flutuantes, óleos e graxas (minerais e vegetais) dentro dos limites da Resolução CONAMA 430/11, além de atestar a taxa média de redução de 75% para DBO5, ou seja, superior ao valor de 60% estabelecido como referência na supracitada resolução, atestando a eficiência do sistema para tratamento dos efluentes com as características previstas.O processo de tratamento de efluentes sanitários é um mecanismo que depende da análise de variáveis técnicas e demográficas para a especificação do sistema de tratamento mais adequado à demanda atrelada à eficiência de remoção de carga orgânica requerida e o uso que se pretende dar ao efluente tratado. Dessa forma o objetivo do presente estudo de caso, é avaliar a eficiência de um sistema compacto de tratamento de efluentes sanitários, especificado e implantado, para atender uma demanda bruta com contribuição de 71% dos efluentes gerados em frentes de obras por banheiros químicos, tendo como premissas a implantação de equipamento com característica de tratamento aeróbio, com sistema de lodo ativado. A metodologia utilizada baseou-se no levantamento bibliográfico de referência, com a compilação de dados técnicos dos projetos de engenharia executados e normas associadas, realizando análise das taxas de tratabilidade do sistema, através dos resultados obtidos por laudos de monitoramentos realizados durante o ano de 2015. Como resultados, conseguiu-se observar o enquadramento dos parâmetros pH, temperatura, materiais sedimentáveis, materiais flutuantes, óleos e graxas (minerais e vegetais) dentro dos limites da Resolução CONAMA 430/11, além de atestar a taxa média de redução de 75% para DBO5, ou seja, superior ao valor de 60% estabelecido como referência na supracitada resolução, atestando a eficiência do sistema para tratamento dos efluentes com as características previstas.

Global Warming Threshold and Mechanisms for Accelerated Greenland Ice Sheet Surface Mass Loss.

The Community Earth System Model version 2.1 (CESM2.1) is used to investigate the evolution of the Greenland ice sheet (GrIS) surface mass balance (SMB) under an idealized CO forcing scenario of 1% increase until stabilization at 4 pre‐industrial at model year 140. In this simulation, the SMB calculation is coupled with the atmospheric model, using a physically based surface energy balance scheme for melt, explicit calculation of snow albedo, and a realistic treatment of polar snow and firn compaction. By the end of the simulation (years 131–150), the SMB decreases with 994 Gt yr with respect to the pre‐industrial SMB, which represents a sea‐level rise contribution of 2.8 mm yr. For a threshold of 2.7‐K global temperature increase with respect to pre‐industrial, the rate of expansion of the ablation area increases, the mass loss accelerates due to loss of refreezing capacity and accelerated melt, and the SMB becomes negative 6 years later. Before acceleration, longwave radiation is the most important contributor to increasing energy for melt. After acceleration, the large expansion of the ablation area strongly reduces surface albedo. This and much increased turbulent heat fluxes as the GrIS‐integrated summer surface temperature approaches melt point become the major sources of energy for melt.

Efficacy, pharmacokinetics and neurocognitive performance of dual, NRTI-sparing antiretroviral therapy in acute HIV-infection.

The aim of this study was to evaluate penetration of antiretrovirals into compartments and efficacy of a dual, NRTI-sparing regimen in acute HIV infection (AHI). Single-arm, open-label pilot study of participants with AHI initiating ritonavir-boosted darunavir 800 mg once daily and etravirine 400 mg once daily or 200 mg twice daily within 30 days of AHI diagnosis. Efficacy was defined as HIV RNA less than 200 copies/ml by week 24. Optional sub-studies included pharmacokinetics analysis from genital fluids (weeks 0-4, 12, 48), cerebrospinal fluid (CSF) (weeks 2-4, 24 and 48) and endoscopic biopsies (weeks 4-12 and 36-48). Neuropsychological performance was assessed at weeks 0, 24 and 48. Fifteen AHI participants were enrolled. Twelve (80%) participants achieved HIV RNA less than 200 copies/ml by week 24. Among 12 participants retained through week 48, nine (75%) remained suppressed to less than 50 copies/ml. The median time from ART initiation to suppression less than 200 and less than 50 copies/ml was 59 and 86 days, respectively. The penetration ratios for etravirine and darunavir in gut associated lymphoid tissue were 19.2 and 3.05, respectively. Most AHI participants achieving viral suppression experienced neurocognitive improvement. Of the three participants without overall improvement in neurocognitive functioning as measured by impairment ratings (more than two tests below 1 SD), two had virologic failure. NRTI-sparing ART started during AHI resulted in rapid viral suppression similar to NRTI-based regimens. More novel and compact two-drug treatments for AHI should be considered. Early institution of ART during AHI appears to improve overall neurocognitive function and may reduce the risk of subsequent neurocognitive impairment. CLINICALTRIALS.GOV:: NCT00855413.

Heterogeneous diffusion in aerobic granular sludge.

Aerobic granular sludge (AGS) technology allows simultaneous nitrogen, phosphorus, and carbon removal in compact wastewater treatment processes. To operate, design, and model AGS reactors, it is essential to properly understand the diffusive transport within the granules. In this study, diffusive mass transfer within full‐scale and lab‐scale AGS was characterized with nuclear magnetic resonance (NMR) methods. Self‐diffusion coefficients of water inside the granules were determined with pulsed‐field gradient NMR, while the granule structure was visualized with NMR imaging. A reaction‐diffusion granule‐scale model was set up to evaluate the impact of heterogeneous diffusion on granule performance. The self‐diffusion coefficient of water in AGS was ∼70% of the self‐diffusion coefficient of free water. There was no significant difference between self‐diffusion in AGS from full‐scale treatment plants and from lab‐scale reactors. The results of the model showed that diffusional heterogeneity did not lead to a major change of flux into the granule (<1%). This study shows that differences between granular sludges and heterogeneity within granules have little impact on the kinetic properties of AGS. Thus, a relatively simple approach is sufficient to describe mass transport by diffusion into the granules.

English

The performance of maize on tilled and untilled sandy loam soil, under different levels of compaction of 0, 2, 4 and 6 tractor-wheel passes in a humid tropical environment was investigated with a Massey Ferguson (MF) 90-disc plough, mounted on an MF 260 tractor. The experimentation had different aspects, respectively conducted in the field and laboratory, at the Rivers State University, Port Harcourt, Nigeria. The experimental field was a 72 m2 plot of land, which was left fallow for two years before the investigation. The plot was sub-divided into five experimental subplots of 9 m2 each, numbered 1 to 5, with a furrow spacing of 0.5 m. Soil samples were taken randomly at a depth of 0.3 m for the determination of the soil physical properties. After the compaction treatments, maize seeds were manually planted at a depth of 0.05 m and the growth and yield of the maize monitored over a period of fourteen weeks after planting. The investigation showed that the maize crop performed optimally on subplot (2), which was tilled and un-compacted, with a dry matter content of 2,859 kg ha-1, while the least performance was on subplot (1) that was untilled and un-compacted, with a dry matter content of 1,192 kg ha-1. Therefore, this research establishes that, with the agricultural practice of shifting cultivation, sandy loam soil in a humid tropical region requires a minimum level of tillage to achieve optimal yield of maize crop. Key words: Maize, compaction, growth and yield, tilled soil, untilled soil, sandy loam. &nbsp;

Influence of rain events on the efficiency of a compact wastewater treatment plant: a case study on a university campus aiming water reuse for agriculture.

In this study, the efficiency of contaminant removal from a compact wastewater treatment plant (CWTP) in a university campus under different rain conditions was evaluated. Wastewater samples were collected weekly for 1year and the physicochemical parameters were monitored. Removal efficiency higher than 77%, reaching values above 95% for samples with lower wastewater flow rates, was found for biological oxygen demand (BOD) and total and fecal coliforms. The pH values remained in the range of 6.0-8.0. However, pH values below 6.8 impaired the nitrification rate and, therefore, the removal of total Kjeldahl nitrogen (TKN) and ammonia was lower than the expected, with concentration values above those set by the Brazilian regulation for wastewater discharge. The results show that the flow rate of wastewater at the entrance of the CWTP is directly related to the rain events, thus affecting its efficiency, mainly in the removal of total solids, turbidity, and organic matter. The assessment of the treated wastewater reuse on site for agricultural purposes showed to be a prominent and more sustainable alternative regarding the discharge of wastewater into water bodies.

Evaluation of the technoeconomic feasibility of electrochemical hydrogen peroxide production for decentralized water treatment

This study evaluated the feasibility of electrochemical hydrogen peroxide (H2O2) production with gas diffusion electrode (GDE) for decentralized water treatment. Carbon black-polytetrafluoroethylene GDEs were prepared and tested in a continuous flow electrochemical cell for H2O2 production from oxygen reduction. Results showed that because of the effective oxygen transfer in GDEs, the electrode maintained high apparent current efficiencies (ACEs,>80%) for H2O2 production over a wide current density range of 5–400 mA/cm2, and H2O2 production rates as high as ∼202 mg/h/cm2 could be obtained. Long-term stability test showed that the GDE maintained high ACEs (>85%) and low energy consumption (< 10 kWh/kg H2O2) for H2O2 production for 42 d (∼1000 h). However, the ACEs then decreased to ∼70% in the following 4 days because water flooding of GDE pores considerably impeded oxygen transport at the late stage of the trial. Based on an electrode lifetime of 46 days, the overall cost for H2O2 production was estimated to be ∼0.88 $/kg H2O2 including an electricity cost of 0.61 $/kg and an electrode capital cost of 0.27 $/kg. With a 9 cm2 GDE and 40 mA/cm2 current density, ∼2–4 mg/L of H2O2 could be produced on site for the electro-peroxone treatment of a 1.2 m3/d groundwater flow, which considerably enhanced ibuprofen abatement compared with ozonation alone (∼43%–59% vs. 7%). These findings suggest that electrochemical H2O2 production with GDEs holds great promise for the development of compact treatment technologies for decentralized water treatment at a household and community level.

Alfalfa Yield Prediction Using UAV-Based Hyperspectral Imagery and Ensemble Learning

Alfalfa is a valuable and intensively produced forage crop in the United States, and the timely estimation of its yield can inform precision management decisions. However, traditional yield assessment approaches are laborious and time-consuming, and thus hinder the acquisition of timely information at the field scale. Recently, unmanned aerial vehicles (UAVs) have gained significant attention in precision agriculture due to their efficiency in data acquisition. In addition, compared with other imaging modalities, hyperspectral data can offer higher spectral fidelity for constructing narrow-band vegetation indices which are of great importance in yield modeling. In this study, we performed an in-season alfalfa yield prediction using UAV-based hyperspectral images. Specifically, we firstly extracted a large number of hyperspectral indices from the original data and performed a feature selection to reduce the data dimensionality. Then, an ensemble machine learning model was developed by combining three widely used base learners including random forest (RF), support vector regression (SVR) and K-nearest neighbors (KNN). The model performance was evaluated on experimental fields in Wisconsin. Our results showed that the ensemble model outperformed all the base learners and a coefficient of determination (R2) of 0.874 was achieved when using the selected features. In addition, we also evaluated the model adaptability on different machinery compaction treatments, and the results further demonstrate the efficacy of the proposed ensemble model.

Root anatomical traits contribute to deeper rooting of maize under compacted field conditions.

To better understand the role of root anatomy in regulating plant adaptation to soil mechanical impedance, 12 maize lines were evaluated in two soils with and without compaction treatments under field conditions. Penetrometer resistance was 1-2 MPa greater in the surface 30 cm of the compacted plots at a water content of 17-20% (v/v). Root thickening in response to compaction varied among genotypes and was negatively associated with rooting depth at one field site under non-compacted plots. Thickening was not associated with rooting depth on compacted plots. Genotypic variation in root anatomy was related to rooting depth. Deeper-rooting plants were associated with reduced cortical cell file number in combination with greater mid cortical cell area for node 3 roots. For node 4, roots with increased aerenchyma were deeper roots. A greater influence of anatomy on rooting depth was observed for the thinner root classes. We found no evidence that root thickening is related to deeper rooting in compacted soil; however, anatomical traits are important, especially for thinner root classes.

Long-term impacts of soil compaction and cultivation on soil carbon and nitrogen pools, foliar δ13C and δ15N as well as tree growth in a hoop pine plantation of subtropical Australia

The aim of this study was to examine the long-term impacts of mechanical compaction and cultivation on soil C and N pools, δ13C and δ15N of soil and foliage as well as tree growth. In a hoop pine plantation of subtropical Australia, the diameter at breast height over bark (DBHoB) and tree height; δ13C and δ15N of soil and foliage; and soil C and N pools were determined after 17 years following forwarder compaction (control, light and heavy) and cultivation (control and disc plough) treatments. Light compaction was associated with the significantly higher soil total carbon (TC) and total nitrogen (TN) in the 20–30 cm soil and higher TN in the 30–60 cm soil (p < 0.01). Cultivation was linked to the significantly higher soil TC in the 0–10 cm soil, and TC, TN and hot water-extractable total nitrogen (HWETN) in the 10–20 cm soil (p < 0.01). Higher δ15N in the 0–10 cm soil and in the foliage in the heavily compacted plots was due to previous soil denitrification, while light compaction and cultivation were associated with the lower foliar δ13C due to decreased foliar N concentration and reduced photosynthesis rate with increasing foliar biomass under higher N supply. The δ13C and δ15N of foliage and soil were useful indicators of the C and N processes in plant-soil system in response of management impacts in the plantation. Light compaction and cultivation generally had beneficial impacts on soil C and N pools over long term, whereas there was no difference in the impacts of different compaction and cultivation treatments on tree growth.