KCl pH Research Articles

Electrochemical Immunosensors on Laser-Induced Graphene Platforms for Monitoring of Anti-RBD Antibodies After SARS-CoV-2 Infection

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has posed a major challenge to global health. The development of fast, accurate, and accessible diagnostic methods is essential in controlling the disease and mitigating its impacts. In this context, electrochemical biosensors present themselves as promising tools for the efficient monitoring of SARS-CoV-2 infection. We have developed a highly specific biosensor for the detection of anti-SARS-CoV-2 antibodies in patient sera. The use of the RBD-S region as an antigen, although purified to minimize cross-linking, poses a specific challenge. The structural similarity between SARS-CoV-2 and other respiratory viruses, as well as the complexity of the serum matrix, hinders robust analytical strategies to ensure diagnostic accuracy. This work presents a novel immunosensor for COVID-19 diagnosis using laser-induced graphene (LIG) electrodes subjected to electrochemical reduction with graphene (named rGraphene-LIG). In the present study, we chose an initial approach focused on demonstrating the concept and evaluating the feasibility of the rGraphene-LIG sensor for SARS-CoV-2 detection. The rGraphene-LIG electrodes presented a notable current increase for the redox probe in the aqueous solution of a mixture of 5 mmol L−1 potassium ferricyanide/ferrocyanide ([Fe(CN)6]3−/[Fe(CN)6]4−) in 0.1 mol L−1 KCl (pH set at 7.4). As a proof of concept, the rGraphene-LIG electrode was applied for antibody determination in real samples using cyclic voltammetry, and a limit of detection (LOD) of 0.032 μg L−1 was achieved. When determining antigens in commercial samples, we obtained an LOD of 560 ηg mL−1 and a limit of quantification of 1677 ηg mL−1. The results of the electrochemical experiments were in accordance with the surface roughness obtained from atomic force microscopy images. Based on these results, the rGraphene-LIG electrode is shown to be an excellent platform for immunoglobulin detection when present in individuals after antigenic exposure caused by SARS-CoV-2.

Self-supervised learning of Vision Transformers for digital soil mapping using visual data

In arid environments, prospecting cultivable land is challenging due to harsh climatic conditions and vast, hard-to-access areas. However, the soil is often bare, with little vegetation cover, making it easy to observe from above. Hence, remote sensing can drastically reduce costs to explore these areas. For the past few years, deep learning has extended remote sensing analysis, first with Convolutional Neural Networks (CNNs), then with Vision Transformers (ViTs). The main drawback of deep learning methods is their reliance on large calibration datasets, as data collection is a cumbersome and costly task, particularly in drylands. However, recent studies demonstrate that ViTs can be trained in a self-supervised manner to take advantage of large amounts of unlabelled data to pre-train models. These backbone models can then be finetuned to learn a supervised regression model with few labelled data.In our study, we trained ViTs in a self-supervised way with a 9500 km2 satellite image of dry-lands in Saudi Arabia with a spatial resolution of 1.5 m per pixel. The resulting models were used to extract features describing the bare soil and predict soil attributes (pH H2O, pH KCl, Si composition). Using only RGB data, we can accurately predict these soil properties and achieve, for instance, an RMSE of 0.40 ± 0.03 when predicting alkaline soil pH. We also assess the effectiveness of adding additional covariates, such as elevation. The pretrained models can as well be used as visual features extractors. These features can be used to automatically generate a clustered map of an area or as input of random forests models, providing a versatile way to generate maps with limited labelled data and input variables.

Geochemical distribution of major and trace elements in hydromorphic soil profiles developed on recent alluvium

Geochemical composition and distribution of major elements study is vital in terms of investigating the major soil forming compounds and to know the fate of trace elements in soils. Particle size distribution (PSD), pH, organic carbon (OC), and major and trace elements of hydromorphic soils formed on recent alluvium in Obafemi-Owode Local Government Area of Ogun state, Nigeria were analysed using standard procedures. Three profiles pits were dug based on the mapping units identified, and samples were collected for laboratory analysis. Data were subjected descriptive statistics and Pearson’ correlation coefficients using IBM SPSS version 27. The PSD was dominated by sand content, followed by clay and silt, and soil pH in KCl was strongly acid (3.17–4.30) and pH in H2O was moderately acid (4.74–5.80), while OC contents were low to moderate (1.22–6.69 g/kg). The major elemental results showed higher concentration of SiO2 (>50 %) connotes presence quartz, feldspar, and clay minerals. Manganese, Cu, Ba, Zr, and Zn have higher concentrations among the trace elements. Major elements ratios (SiO2/Al2O3, K2O/Al2O3) showed moderate weathering stage, while trace elements ratios (Ni/Co and Cu/Zn) revealed deposition under humid conditions and anoxic environment. The statistical analysis revealed that most elements have skewness closed to zero except MgO and K2O. Correlation coefficients between the elements are positive and significant (p < 0.05 and p < 0.01) indicating that their presence can be accounted for by similar lithology, though some have negative relationship which could be as a result of anthropogenic activities. The study found that elements were potential tracers for the presence of human activities and environmental changes.

Soil Fertility Status of the Two Eruptions of Mount Tangkuban Parahu and Mount Tampomas in Tanjungsari District Sumedang Regency

Soil fertility is one of the important factors to optimize plant growth and productivity. This study aims to analyze the status of soil fertility through soil physical analysis (texture) soil chemistry (pH H2O and KCl, C-organic, cation exchange capacity, base saturation, P2O5, and K2O) in several land units of Tanjungsari District, Sumedang Regency. The method used to determine sample points is purposive sampling method by considering several land units, namely soil type map, soil parent material map, topography map (slope), land use map, and rainfall data. Soil fertility status is determined by the matching table method between the results of soil chemical analysis with soil fertility status index that refers to the Soil Research Center (PPT) 1995. The results of the matching table data analysis showed that the research area almost entirely included low fertility status criteria except for the pine forest land unit on a moderately steep slope including medium fertility status criteria. The factors of base saturation, k-potential (K2O), and C-organic are the limiting factors of soil fertility status in the Tanjungsari District of Sumedang Regency, including the low to medium category.

Tensile-Strained Cu Penetration Electrode Boosts Asymmetric C-C Coupling for Ampere-Level CO2-to-C2+ Reduction in Acid.

The synthesis of multicarbon (C2+) products remains a substantial challenge in sustainable CO2 electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere-level high-efficiency CO2 electroreduction to C2+ products in both neutral and strongly acidic (pH=1) electrolytes using a hierarchical Cu hollow-fiber penetration electrode (HPE). High concentration of K+ could concurrently suppress hydrogen evolution reaction and facilitate C-C coupling, thereby promoting C2+ production in strong acid. By optimizing the K+ and H+ concentration and CO2 flow rate, a faradaic efficiency of 84.5 % and a partial current density as high as 3.1 A cm-2 for C2+ products, alongside a single-pass carbon efficiency of 81.5 % and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H2SO4 and KCl (pH=1). Experimental measurements and density functional theory simulations suggested that tensile-strained Cu HPE enhances the asymmetric C-C coupling to steer the selectivity and activity of C2+ products.

Tensile‐Strained Cu Penetration Electrode Boosts Asymmetric C–C Coupling for Ampere‐Level CO2‐to‐C2+ Reduction in Acid

The synthesis of multicarbon (C2+) products remains a substantial challenge in sustainable CO2 electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere‐level high‐efficiency CO2 electroreduction to C2+ products in both neutral and strongly acidic (pH = 1) electrolytes using a hierarchical Cu hollow‐fiber penetration electrode (HPE). High concentration of K+ could concurrently suppress hydrogen evolution reaction and facilitate C–C coupling, thereby promoting C2+ production in strong acid. By optimizing the K+ and H+ concentration and CO2 flow rate, a faradaic efficiency of 84.5% and a partial current density as high as 3.1 A cm–2 for C2+ products, alongside a single‐pass carbon efficiency of 81.5% and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H2SO4 and KCl (pH = 1). Experimental measurements and density functional theory simulations suggested that tensile‐strained Cu HPE enhances the asymmetric C–C coupling to steer the selectivity and activity of C2+ products.

Pseudomonas sp. Bacteria: potentially toxic metal-contaminated soil remediation potentials - minimum inhibitory concentration investigation and application

Agricultural inputs used for correction or nutrition in agriculture have a composition that, in addition to containing desirable elements, often includes potentially toxic metals that contaminate the soil. Faced with this scenario, one can observe the appearance of various remediation techniques, amongst them, bio-remediation. This technique has been shown to be highly promising, as there is a wide variety of genera and species of microorganisms. In this study, the application of Pseudomonas sp. bacteria in soil from bean cultivation was investigated, with the aim of removing Zn2+ and Ni2+ ions. Analyzes were carried out of soil parameters, pH in water and KCl, Zero Charge Point, exchangeable acidity, quantity of organic matter in soil and initial concentrations of ions. To evaluate the tolerance of bacteria to metal concentrations in the soil, studies of Minimum Inhibitory Concentration were conducted. A bioremediation experiment was then carried out, applying the bacteria to the soil and monitoring the process over 21 days. The results showed that Pseudomonas sp. bacteria showed good resistance to high metal concentrations, as well as remarkable capacity and efficiency in the absorption of metals, reaching 0,063 mg kg-1 and 90.5% efficiency in the removal of Ni2+ ions, and 0,012 mg kg-1 capacity and 47.9% efficiency in the removal of Zn2+ ions. These results suggest that the Pseudomonas sp. bacteria are promising for the bioremediation of soils contaminated with potentially toxic metals.

Design of poured earth construction materials from the elementary characteristics of tropical soils

Sustainable construction materials and local solutions are crucial for meeting urbanisation demands in tropical regions like French Guiana. Poured earthen construction, primarily composed of local soil, offers a cost-effective and environmentally friendly alternative. To ensure good consistency for pouring, the use of dispersants to deflocculate clay particles is an effective strategy that reduces water demand while enhancing the material's physical and mechanical properties. However, the variability of soil impacts the effectiveness of dispersants and the earth's material properties. It is currently unknown how the specific properties of tropical soils can influence the mix design of poured earth and how it impacts their resulting physical and mechanical characteristics. This work examines the soil properties that could help select suitable soil for poured earth construction. Four tropical soils of French Guiana were characterised in detail and used to prepare mortars with varying amounts of water and dispersant (sodium hexametaphosphate). The consistency and compressive strength of the mortars correlated with the mineralogical and geotechnical characteristics of the soils. In particular, soils with high levels of metal oxides produced mortars with the highest compressive strength. Using a dispersant consistently increased the compressive strength and dry density of the mortars and enabled a reduction in water content. Importantly, the analysis revealed that two easily measurable soil properties, the passing at 63 µm and the pH measured in potassium chloride (pH KCl), could predict the mechanical properties of the mortars and the amount of dispersant needed. Specifically, the pH KCl correlated with the proportion of iron and aluminium oxide and showed a positive linear correlation with the compressive strength. Overall, this study identifies easily measurable soil properties, in particular the pH KCl, for selecting and designing high-performance earth materials with tropical soils. It offers promising prospects for industrialising poured earth construction.

Simple and Rapid Voltammetric Method Using a Gold Microwire Electrode to Measure Inorganic Arsenic in Holopelagic Sargassum (Fucales, Phaeophyceae)

The valorization of massive strandings of holopelagic Sargassum spp. is strongly limited by high levels of inorganic arsenic (Asi) that are potentially above the limit of current regulations. Monitoring Asi in algal biomass is currently achieved using standard chromatographic separation followed by spectroscopic detection. Here, we propose an alternative simpler procedure based on the extraction of Asi from the freeze-dried algal powder in deionized water and the electroanalytical detection of the diluted extract at a gold-microwire electrode. The protocol was optimized both in terms of extraction (powder/water ratio, extraction time, temperature) and electrolyte used for the voltammetric detection. Two electrolytes were tested: one composed of citric acid, sulfamic acid and KCl (pH 2.0) and another composed of an acetate buffer (pH 4.7) and NaCl. We demonstrate here that Asi determination is possible with the first electrolyte but it is necessary to deal with a relative unstable signal. Measurement of Asi was best achieved with the second electrolyte (acetate buffer and NaCl) with the following optimized electrochemical conditions: deposition potential of −1.2 V, deposition time of 30 seconds and linear scan voltammetry. Voltammetric results were then compared to a reference method (HPLC-ICP-MS) using different morphotypes of holopelagic Sargassum spp. (S. natans VIII, S. natans I and S. fluitans III), using commercial extracts of brown seaweeds and using a Hijiki certified reference material. Very good agreement was obtained between our novel method and HPLC-ICP-MS. Both methods show that inorganic arsenic is almost entirely present as As(V) in Sargassum spp. extracts.

A new frontier of archaeological dark earth at the northern Amazonia headwaters of Roraima state: Soil attributes and landscape interplays

Despite the existence of various studies on Archaeological Dark Earth - ADE, there is still a very large gap concerning the Amazon region, with many areas remaining unexplored scientifically. The aim of this study, therefore, was to characterize and classify areas of Archaeological Dark Earth located on rural properties and in one riverside community in the southern mesoregion of the state of Roraima. At these locations, trenches were dug in a total of 13 areas, and the profiles morphologically characterized and sampled for soil classification and Carbon-14 dating. The areas were georeferenced and measured, and the history of land use was described, together with the predominant vegetation in the region. The following physical analyses were carried out: texture and bulk density. The chemical analysis consisted of pH in water and KCl, exchangeable cations, exchangeable Al, available P, titratable acidity (H + Al), total N and organic matter. To produce the maps, computational processing was used in a Geographic Information System - GIS, employing geoprocessing tools with the aid of the ArcGIS v10.6 software; the attributes prepared from SRTM images were drainage network and terrain. Using the Brazilian System of Soil Classification (SiBCS), the profiles were classified as: Argissolos Amarelos, Cambissolo Háplico, Latossolos Amarelos, Argissolo Vermelho Amarelo, and Nitossolo Vermelho. It is suggested that the anthropogenic subgroup be included in the SiBCS. With the exception of 3 horizons, the anthropogenic horizon of each of the profiles sampled in the region has a eutrophic character, with ages that range from 1120 to 1864 years before present (YBP). Each of the areas of ADE is associated with a drainage network ranging from a small creek, approximately 6m wide, to a fast-flowing river, such as the Branco River, which is over 1,700m wide. The 13 areas are located in places away from the flood area that show little variation in relief, with a predominance of flat to gently undulating terrain.

Benzydamine plays a role in limiting inflammatory pain induced by neuronal sensitization.

Benzydamine is an active pharmaceutical compound used in the oral care pharmaceutical preparation as NSAID. Beside from its anti-inflammatory action, benzydamine local application effectively reliefs pain showing analgesic and anaesthetic properties. Benzydamine mechanism of action has been characterized on inflammatory cell types and mediators highlighting its capacity to inhibit pro-inflammatory mediator's synthesis and release. On the other hand, the role of benzydamine as neuronal excitability modulator has not been yet fully explored. Thus, we studied benzydamine's effect over primary culture DRG nociceptors excitability and after acute and chronic inflammatory sensitization, as a model to evaluate nociceptor response. Benzydamine demonstrated to effectively inhibit neuronal basal excitability reducing its firing frequency and increasing rheobase and afterhyperpolarization amplitude. Its effect was time and dose-dependent. At higher doses, benzydamine induced changes in action potential wavelength, decreasing its height and slightly increasing its duration. Moreover, the compound reduced neuronal acute and chronic inflammatory sensitization. It inhibited neuronal excitability mediated either by an inflammatory cocktail, acidic pH or high external KCl. Notably, higher potency was evidenced under inflammatory sensitized conditions. This effect could be explained either by modulation of inflammatory and/or neuronal sensitizing signalling cascades or by direct modulation of proalgesic and action potential firing initiating ion channels. Apparently, the compound inhibited Nav1.8 channel but had no effect over Kv7.2, Kv7.3, TRPV1 and TRPA1. In conclusion, the obtained results strengthen the analgesic and anti-inflammatory effect of benzydamine, highlighting its mode of action on local pain and inflammatory signalling.

A Conceptual Approach to the Histosols Profile Morphology as a Risk Indicator in Assessing the Sustainability of Their Use and Impact on Climate Change

In the context of climate change, the questions of the sustainability of peat soil use are particularly relevant. The evaluation of changes in the properties of soils (including histosols) using chemical methods is expensive, thus, their application possibilities are limited. Analyzing the morphology of histosol profiles would provide effective spatial analysis opportunities for assessing the extent of their anthropogenic transformation and impact on climate change. The key diagnostic horizons and their sequences for the identification of the risk group are the main results of the study. The analysis included 12 soil profiles, whose morphological structure was characterized using the WRB 2022 system of master symbols and suffixes for soil profile horizon descriptions. The analyzed profiles were excavated in forested (relatively natural), agricultural (agrogenized) and peat mining (technogenized) areas. The insights of this article in the discussion are based on the chemical analyses (pH KCl, N, P and K, soil organic carbon, dissolved organic carbon, mobile humus substance, humic and fulvo acids, C:N ratio and humification degree) of three histosol profiles. The main discussion is based on the results of the morphological analysis of the profiles. The results of this research allowed for the identification of a different structure of the histosol profile. The upper part of the histosol profile, which consists of O–H(a,e,i) horizons, indicates its naturalness. The murshic horizon (Hap) is the classic top horizon of the agricultural histosol profile, which is most affected by mineralization. The technogenized histosols have a partially destroyed profile, which is represented by the Ahτ/Haτ or only Haτ horizons at the top. The morphology of the histosol profile and the identification of the relevant horizons (Hap, Haτ and Ahτ) indicate its risks and presuppose a usage optimization solution. The most dangerous in the context of sustainable land use principles and climate change is the murshic horizon (Hap), which is uncovered after removing the horizon O. The risks of sustainable use of histosol are caused by measures that promote its microbiological activity, which is the maintenance of a drained state and cultivation. In the context of GHG emissions and sustainable use, the most favorable means would be the formation of the horizon O by applying perennial plants. Rewetting should be applied to those histosols whose removal from the agricultural or mining balance would provide maximum ecological benefits.

Pushing the Limits of Biosensing: Selective Calcium Ion Detection with High Sensitivity via High-k Gate Dielectric Engineered Si Nanowire Random Network Channel Dual-Gate Field-Effect Transistors.

Calcium ions (Ca2+) are abundantly present in the human body; they perform essential roles in various biological functions. In this study, we propose a highly sensitive and selective biosensor platform for Ca2+ detection, which comprises a dual-gate (DG) field-effect transistor (FET) with a high-k engineered gate dielectric, silicon nanowire (SiNW) random network channel, and Ca2+-selective extended gate. The SiNW channel device, which was fabricated via the template transfer method, exhibits superior Ca2+ sensing characteristics compared to conventional film channel devices. An exceptionally high Ca2+ sensitivity of 208.25 mV/dec was achieved through the self-amplification of capacitively coupled DG operation and an enhanced amplification ratio resulting from the high surface-to-volume ratio of the SiNW channel. The SiNW channel device demonstrated stable and reliable sensing characteristics, as evidenced by minimal hysteresis and drift effects, with the hysteresis voltage and drift rate measuring less than 6.53% of the Ca2+ sensitivity. Furthermore, the Ca2+-selective characteristics of the biosensor platform were elucidated through experiments with pH buffer, NaCl, and KCl solutions, wherein the sensitivities of the interfering ions were below 7.82% compared to the Ca2+ sensitivity. The proposed Ca2+-selective biosensor platform exhibits exceptional performance and holds great potential in various biosensing fields.

Surface charge characteristics of Inceptisols ameliorated with biochar from young coconut waste

The colloidal surface of the soil contains an electric charge and various surface characteristics. The application of amelioration technology can increase the availability of nutrients and overcome contamination such as pesticides in the soils. This research aimed to study the surface charge characteristics of Inceptisols ameliorated with biochar from young coconut waste (YCW). The experiment was carried out using a completely randomized design with three replications each. The treatment was carried out in a pot with dose equivalent to biochar YCW: A = 0 (0.0g); B = 10 (2.5g); C = 20 (5.0g); D = 30 (7.5g), and (E) 40 t ha-1 (10g 500g-1 soil). The results showed amelioration technology with biochar from young coconut waste, at the application of 40 t ha-1 on Inceptisols, an increased soil surface charge through changes in chemical characteristics by increasing the pH (H2O), EC, CEC, and SOM. The reduction in transmittance in the H-O-H bending band of water and C=C alkene (aromatic) (from 88.95 to 88,83 %) and minerals (from 50.50 to 50.42 %), increased the adsorption capacity of Inceptisols. The relationship of surface charge with chemical properties of Inceptisols ameliorated with biochar from young coconut waste occurred at a correlation value of ΔpH with pH H2O > pH PZC > CEC > Mineral = SOM > EC > pH KCl.

Perbaikan kualitas tanah berpasir untuk kebun kopi dengan penambahan tanah liat dan kompos di Desa Bambang, Kecamatan Wajak

Introduction: This study focuses on the effect of applying clay and compost on improving the quality of sandy soil in terms of the physical and chemical quality of the soil so that it can be a solution to problems in managing sandy soil so that the land can be productive and sustainable. Methods: This study used a factorial completely randomized design (RAL-F) with 3 treatment factors, namely: Depth (K1: 0-30 cm, K2: 30-60 cm), Dosage of compost (M1: 0 ton ha-1 as control, M2: 20 ton ha-1), Percentage of mineral soil (T1: 0% as control, T2: 25%, T3: 50%). Each treatment was repeated 4 times to obtain 48 pot units for the experiment. Data collection is carried out every 2 weeks for soil pH data. As for the other observation parameters taken in the last week of the incubation process, the data taken are chemical data in accordance with predetermined observation parameters which include soil physical properties such as bulk density, specific gravity, porosity, moisture content, pF value and basic chemical properties such as pH, organic matter, P-Available, N-Total. Results: Based on the results of laboratory analysis, it was shown that there was an increase in the average value of pH H2O and pH KCl every week, where initially the pH of H2O was 5.3 (1 MSI) to 5.9 (11 MSI) and the pH of KCl was from 5.1 (1 MSI) to 5.5 (11 MSI). This proves that the addition of organic matter and clay to the soil can increase the soil pH value. In addition to an increase in soil pH, there was also an increase in other chemical properties (BO, total-N and available-P) as well as soil physical properties (BI, BJ, Porosity and pF 2.5). Conclusion: the addition of clay soil and compost can improve the quality of sandy soil, especially the soil chemistry characteristics.

Conformational preferences of DNA from the promoter regions of the c-MYC, VEGF, and Bcl-2 oncogenes.

We characterized the conformational preferences of DNA in an equimolar mixture of complementary G-rich and C-rich strands from the promoter regions of the c-MYC, VEGF, and Bcl-2 oncogenes. Our CD-based approach presupposes that the CD spectrum of such a mixture is the spectral sum of the constituent duplex, G-quadruplex, i-motif, and coiled conformations. Spectra were acquired over a range of temperatures at different pH and concentrations of KCl. Each spectrum was unmixed in terms of the predetermined spectra of the constituent conformational states to obtain the corresponding weighting factors for their fractional contributions to the total population of DNA. The temperature-dependences of those contributions then were analyzed in concert according to a model based on a thermodynamic representation of the underlying equilibria. Comparison of the conformational data on the c-MYC, VEGF, and Bcl-2 DNA reveals that the distribution of conformational states depends on the specific DNA sequence and is modulated by environmental factors. Under the physiological conditions of room temperature, neutral pH, and elevated concentrations of potassium ions, the duplex conformation coexists with the G-quadruplex conformation in proportions that depend on the sequence. This observed conformational diversity has biological implications suggesting a novel, thermodynamically controlled mechanism for the regulation of gene expression. In that hypothesis, a specific distribution of duplex and tetraplex conformations in a promoter region is fine-tuned to maintain the healthy level of gene expression. Any deviation from a healthy distribution of conformational states may result in pathology stemming from up- or downregulation of the gene.

3D porous CS-AuNPs-PEDOT-PB nanocomposite cryogel for highly sensitive label-free electrochemical immunosensor for carcinoembryonic antigen determination

An electrochemical immunosensor was developed to determine carcinoembryonic antigen (CEA). A sensor platform was created using a three-dimensional (3D) porous chitosan cryogel incorporating poly(3,4-ethylenedioxythiophene), Prussian blue, and gold nanoparticles modified screen-printed carbon electrode (CS-AuNPs-PEDOT-PB cry/SPCE). The platform was activated with anti-CEA and measurement of CEA was based on the formation of an immunocomplex proportional to CEA concentration in the sample. CEA was detected using differential pulse voltammetry, which measured the change in reduction peak current of PB in response to the immunocomplex formed. Crucially, PEDOT stabilized PB and amplified the redox current of PB. Under optimal conditions, the proposed immunosensor displayed a high sensitivity, a linear range from 1.0 × 10−4 to 1.0 × 103 pg mL−1, and a detection limit of 5.05 × 10−5 pg mL−1 in 0.10 mol L−1 phosphate buffer containing 0.10 mol L−1 KCl (PBS) (pH 7.00). Reproducibility was excellent (RSD of less than 5.3 %, n = 6), and reusability (sensitivity > 90 % for 36 individual CEA measurements), stability (90 % sensitivity at 5 weeks), and selectivity were good. Additionally, this electrochemical immunosensor successfully quantified CEA in real samples, achieving good recoveries and results agreed (P > 0.05) with the immunoturbidimetry technique.

The Influence of Sewage Sludge and Fly Ash Fertilization on the Total Number of Bacteria (TNB) and Bradyrhizobium Species in Soybean Agroecosystem

The aim of this study was to determine the impact of different chemical properties in soil, including changes in magnetic susceptibility and the impact of humic substances from sewage sludge and fly ash on the microbial community in the soybean agroecosystem. A field experiment was carried out using the random plot method on Cambisol with a texture of silt loam. The experiment consisted of 24 plots (six treatments and four replications) using different dozes of sewage sludge and fly ash. The following physicochemical and chemical analyses were performed in the soil samples: pH in KCl, conductivity (λ), total content of heavy metal, magnetic measurements and fractional composition of organic matter. The TNB and the number of the species of Bradyrhizobium in the field cultivation of the soybean variety Lissabon were evaluated using the spread plate method. The total content of heavy metals (Cu, Zn, Cd, Ni, Pb, Cr, Hg, Fe) in the analyzed treatments showed a significant difference between them. The study of the magnetic parameter χ indicated a significant differentiation between treatments from 34.0 to 65.8 × 10−8·m3·kg−1. High correlation coefficients between χ and Fe (r = 0.789), Zn (r = 0.653), Cr (r = 0.617) and TOC (r = 0.949) indicated that the source of these elements was external organic matter. Biological tests (TNB and species of Bradyrhizobium) in different experimental treatments indicated significant relationships between them and showed the resistance of the microbial community in the field cultivation of Lissabon soybean to heavy metal contamination from sewage sludge and fly ash. The study confirmed that external organic matter, such as sewage sludge, can be used as an alternative to natural fertilizers for soybean production.

Sorption of Organic Contaminants by Stable Organic Matter Fraction in Soil.

Soil organic matter (SOM) and its heterogeneous nature constitutes the main factor determining the fate and transformation of organic chemicals (OCs). Thus, the aim of thus research was to analyze the influence of the molecular chemodiversity of a stable SOM (S-SOM) on the sorption potential of different groups of OCs (organochloride pesticides-OCPs, and non-chlorinated pesticides-NCPs, polycyclic aromatic hydrocarbons-PAHs). The research was conducted as a batch experiment. For this purpose, a S-SOM was separated from six soils (TOC = 15.0-58.7 gkg-1; TN = 1.4-6.6 gkg-1, pH in KCl = 6.4-7.4 and WRB taxonomy: fluvisols, luviosols, leptosols) by alkaline urea and dimethylsulphoxide with sulfuric acid. Isolated S-SOM fraction was evaluated by UV-VIS, FT-IR and EEM spectroscopy to describe molecular diversity, which allowed the assessment of its potential sorption properties regarding OCs. In order to directly evaluate the sorption affinity of individual OCs to S-SOM, the mixture of the 3 deuterated contaminants: chrysene (PAHs), 4,4'DDT (OCPs) atrazine (NCPs) were applied. The sorption experiment was carried out according to the 106 OECD Guidelines. The OCs concentration was analyzed by gas chromatography triple mass spectrometry (GC-MS/MS). OCs were characterized by different sorption rates to S-SOM fractions according to the overall trend: atrazine (87.5-99.9%) &gt; 4,4'DDT (64-81.6%) &gt; chrysene (35.2-79.8%). Moreover, atrazine exhibited the highest saturation dynamic with fast bounding time amounting to 6 h of contact with S-SOM. Proportionally, the chrysene showed the slowest binding time achieving an average of 55% sorption after 78 h. Therefore, S-SOM isolated from different soils demonstrated varying binding capacity to OCs (CoV = 21%, 27% and 33% for atrazine, DDT and chrysene, respectively). Results indicate that each sample contains S-SOM with different degrees of transformation and sorption properties that affect the OCs availability in soil. Spectroscopic analyses have shown that the main component of S-SOM are biopolymers at various stages of transformation that contain numerous aromatic-aliphatic groups with mostly hydrophilic substituents.

MORFOLOGI DAN KLASIFIKASI TANAH PADA FORMASI PENIRON BAHAN INDUK ANDESIT PIROKSEN DI DESA PAGEDONGAN, BANJARNEGARA

Rock formation as parent material in Pagedongan Village, Banjarnegara influences the properties of the soil formed. The purpose of this research was to identify the morphology and soil classification according to USDA Taxonomy, National Soil Classifications, and World Reference Base for Soils. This study uses a survey method by determining observation points based on a rock formation, namely Peniron Formation, with pyroxene andesite as parent material for observing soil morphology, physical and chemical of soil in the field, then laboratory analysis included soil texture, bulk density, organic C, soil pH H2O and KCl, exchangeable cations K, Ca, Mg, Na, CEC, and base saturation. The results showed that the soil developed in the Peniron Formation with pyroxene andesite as parent material had morphology with diagnostic horizons of umbric epipedon and argillic endopedon. The results showed that the soil classification according to USDA Taxonomy is Typic Palehumults Isohyperthermic, according to National Soil Classifications is Podsolics Ortoxic, and according to World Reference Base for Soils is Loamic Abruptic Alfisols.