Soil Extracts Research Articles

Centrifuge model tests on spudcan penetration and extraction in sand-clay mixed soil

Jack-up vessels have been used for the construction of offshore wind turbines, and various studies have been conducted on the ground behavior during the penetration and extraction of their spudcans. In this study, the ground behavior of sand-clay mixed soil was investigated. Specifically, a series of actual operations, such as penetration, repeated loading, extraction, and repenetration, were reproduced by centrifuge model tests using sand and clay, as well as their mixtures with different fine-grain contents. Several elemental tests were also conducted prior to the model tests. In addition, the bearing capacity of the spudcan was discussed using estimation equations. The results of the elemental tests showed that in the soils used, the effect of partial drainage became more pronounced when the fine-grain content exceeded 20%, and the permeability, consolidation coefficient, and shear properties changed. These results were close to those of clay when the fine-grain content exceeded 50%. In the centrifuge model tests, the deformation characteristics of the ground changed, and the penetration resistance decreased as the fine-grain content increased. The influence of consolidation and drainage conditions was suggested. The estimation equations of the bearing capacity showed that, in the case of mixed soil, the bearing capacity obtained by the estimation equation under drained or undrained conditions differed significantly from the test results, and the estimation equation that considered the effect of partial drainage could be used to calculate the bearing capacity.

Antioxidant capacity sources of soils under different land uses

Antioxidants (AOX) in soils originate mainly from secondary plant metabolites and are pivotal in many redox processes in environment, maintaining soil quality. Still, little is known about the influence of land uses on their accumulation in soil. The aim of the paper was to determine the content of these redox-active compounds in the extracts of A horizons of abandoned fallows, arable and woodland soils. Total antioxidant capacity (TAC) of soils under various uses and vegetation was evaluated in different soil extracts using Folin-Ciocâlteu method. The contribution of humic acids to TAC was determined and antioxidant profiles estimated using the chromatographic GC–MS method. Forest soils exhibited the highest TAC (15.5 mg g−1) and AOX contents (4.34 mg g−1), which were positively correlated with soil organic carbon content. It was estimated that humic acids contribute to over 50% of TAC in soils. The main phenolics in woodland A horizons were isovanillic and p-hydroxybenzoic acid (p-HA), while esculetin and p-HA predominated in the abandoned fallows due to the prevalence of herbaceous vegetation. Cultivated soils were the most abundant in p-HA (56.42%). In the studied topsoils, there were considerable amounts of aliphatic organic matter, which role in redox processes should be further evaluated.

Effects of arbuscular mycorrhizal fungi on the reduction of arsenic accumulation in plants: a meta-analysis.

Arsenic (As) accumulation in plants is a global concern. Although the application of arbuscular mycorrhizal fungi (AMF) has been suggested as a potential solution to decrease As concentration in plants, there is currently a gap in a comprehensive, quantitative assessment of the abiotic and biotic factors influencing As accumulation. A meta-analysis was performed to quantitatively investigate the findings of 76 publications on the impacts of AMF, plant properties, and soil on As accumulation in plants. Results showed a significant dose-dependent As reduction with higher mycorrhizal infection rates, leading to a 19.3% decrease in As concentration. AMF reduced As(V) by 19.4% but increased dimethylarsenic acid (DMA) by 50.8%. AMF significantly decreased grain As concentration by 34.1%. AMF also improved plant P concentration and dry biomass by 33.0% and 62.0%, respectively. The most significant reducing effects of As on AMF properties were seen in single inoculation and experiments with intermediate durations. Additionally, the benefits of AMF were significantly enhanced when soil texture, soil organic carbon (SOC), pH level, Olsen-P, and DTPA-As were sandy soil, 0.8%-1.5%, ≥7.5, ≥9.1 mg/kg, and 30-60 mg/kg, respectively. AMF increased easily extractable glomalin-related soil protein (EE-GRSP) and total glomalin-related soil protein (T-GRSP) by 23.0% and 28.0%, respectively. Overall, the investigated factors had significant implications in developing AMF-based methods for alleviating the negative effects of As stress on plants.

Human health risks of trace metals through the dietary intake of potato tubers and exposures of potato cultivating soils: A case study of Mymensingh district, Bangladesh

BackgroundTrace metal contamination in soil and farm products is common in Bangladesh, which enhances public awareness. Most of the studies in our country ignored potential human health risks from different routes of exposures to trace metals present in potato tubers and potato-growing soils. ObjectivesThe study objectives were to measure trace metals pollution level in soils, and to evaluate human health risks due to dietary intake of potato tubers, as well as ingestion, dermal and inhalation exposures of potato-cultivating soils of Mymensingh district, Bangladesh. MethodsAn atomic absorption spectrophotometer was used to determine Cd, Ni, Pb, Cr, Cu, Zn, Fe, Co, and Mn in the extract of soils and potato tubers. The study employed contamination factor (CF), pollution load index (PLI), and potential ecological risk index (PERI) to evaluate the level of soil pollution. Non-carcinogenic and carcinogenic human health risks were assessed based on calculated Hazard Quotient and Cumulative Incremental Lifetime Cancer Risk (∑ILCR), respectively. ResultsA threshold of "moderate contamination" (1.0 ≤ CF < 3.0) can be assigned to certain soil sampling sites based on the computed CF values for Ni, Cd, and Pb. On the contrary, the calculated PERI indicated that the soils of potato-cultivating regions of the study area are ecologically free from pollution. Regarding non-cancer risks, the measured hazard quotient (HQ) values for all avenues of exposure to trace metals were below 1.0, indicating that they are safe for human health. On the other hand, the calculated incremental lifetime cancer risk (ILCR) values for Ni in 83.3% of potato tuber samples for both sexes and Cd in 58.3% of males and 91.7% of females had scores greater than 1.00E-04, which indicates carcinogenic risks to adult humans. However, the estimated mean ∑ILCR for males and females in various routes of exposure showed a decreasing trend in the order of ILCROral (potato ingestion) >ILCRSoil ingestion >ILCRDermal adsorption >ILCRSoil inhalation. ConclusionThe agricultural soils of Bangladesh are becoming progressively degraded due to multiple contamination causes along with trace metals. The investigation recommended that future traceability efforts focus on locating possible sites of entry for toxic metals into the nation's food supply chain.

Phycoremediation Potential of Salt-Tolerant Microalgal Species: Motion, Metabolic Characteristics, and Their Application for Saline-Alkali Soil Improvement in Eco-Farms.

Microalgae have great potential for remediating salt-affected soil. In this study, the microalgae species Coelastrella sp. SDEC-28, Dunaliella salina SDEC-36, and Spirulina subsalsa FACHB-351 were investigated for their potential to rehabilitate salt-affected soils. Nylon screens with optimal aperture sizes and layer numbers were identified to efficiently intercept and harvest biomass, suggesting a correlation between underflow capability and the tough cell walls, strong motility, and intertwining characteristics of the algae. Our investigations proved the feasibility of incorporating monosodium glutamate residue (MSGR) into soil extracts at dilution ratios of 1/200, 1/2000, and 1/500 to serve as the optimal medium for the three microalgae species, respectively. After one growth period of these three species, the electrical conductivities of the media decreased by 0.21, 1.18, and 1.78 mS/cm, respectively, and the pH remained stable at 7.7, 8.6, and 8.4. The hypotheses that microalgae can remediate soil and return profits have been verified through theoretical calculations, demonstrating the potential of employing specific microalgal strains to enhance soil conditions in eco-farms, thereby broadening the range of crops that can be cultivated, including those that are intolerant to saline-alkali environments.

Characterising the decay of organic metal complexes in speleothem-forming cave waters

Organic metal complexes (OMCs) transport trace metals (e.g., Co, Ni, Cu) from surface soils, via the unsaturated zone, to sites of cave carbonate (speleothem) formation. OMCs clearly imprint on speleothem trace element chemistry, but the role of kinetic factors in the signal transfer process has yet to be elucidated. We investigated whether OMCs may viably link metal concentrations in stalagmites and local hydrology (i.e., drip rate), via their time-sensitive dissociation (or ‘decay’) in the speleothem water thin-film. We performed competitive ligand exchange experiments using water and soil samples from eight geographically diverse Aotearoa New Zealand caves, providing a first comparative characterisation of speleothem-specific OMC kinetics. Critically, this approach corroborated that NOM ligands limit transition metal availability at the dripwater-speleothem interface, exhibiting stabilities on the order Cu ≈ Co > Ni, whereas organic complexation of the alkaline earth metals Mg and Sr was virtually absent. Systematic variations of OMC stability with natural organic matter characteristics were not observed amongst water samples, whilst enhanced complexation was clearly evident in the comparably organic-rich soil extracts. Our results imply that the supply of transition metals to speleothems is inversely related to drip rate, increasing with drip interval via the decay of OMCs. This process appears most sensitive on time-scales relevant to typical speleothem-forming settings (<0 to ca. 40 drips min−1, corresponding to ca. <5.6 mL min−1), and therefore provides a general, mechanistic link to a quantitative proxy of palaeoclimatic cave drip rates.

Влияние молотой серы на альгоцианофлору щелочных засолённых почв

The paper considers the impact of ground sulphur (S 0 ) used as a chemical ameliorant for alkali-saline soils, as well as of sulphur with mineral and organic fertilizers, on species diversity and abundance of soil phototrophic microorganisms – algae and cyanobacteria. The research was carried out in laboratory conditions through the example of alkali soil. The alkali type is automorphic, its subtype is brown semiarid. Application of ground sulphur, as well as sulphur with mineral and organic fertilizer additives to alkali-saline soil caused considerable change in its chemical and physical-chemical properties: рН decrease, and increase in conductivity and phosphorus, potassium, magnesium, and calcium content in soil extract. Soluble carbonates and hydrocarbonates content decreased. Changes in soil properties and chemical composition effected species composition and abundance of soil algocyanoflora. 16 species, including Cyanobacteria – 10, Bacillariophyta – 4, Chlorophyta – 2, were found in the control soil. 25 species of soil microphototrophs, such as Cyanobacteria – 14, Chlorophyta – 4, Bacillariophyta – 7, were found in the soil of experiment variants. Algocyanoflora species composition of control and experiment variants remains mostly the same (64%). Application of mineral and organic additives caused growth of algocyanoflora species diversity in soil. Sulphur application contributed to microphototrophs cells increasing in number. The highest species diversity of microphototrophs found in the variant with sulfur and a complex of mineral and organic fertilizers.

Selenium increases antimony uptake in ramie (Boehmeria nivea L.) by enhancing the physiological, antioxidative, and ionomic mechanisms

Ramie (Boehmeria nivea L.) is a promising phytoremediation candidate due to its high tolerance and enrichment capacity for antimony (Sb). However, challenges arise as Sb accumulated mainly in roots, complicating soil extraction. Under severe Sb contamination, the growth of ramie may be inhibited. Strategies are needed to enhance Sb accumulation in ramie's aboveground parts and improve tolerance to Sb stress. Considering the beneficial effects of selenium (Se) on plant growth and enhancing resistance to abiotic stresses, this study aimed to investigate the potential use of Se in enhancing Sb uptake by ramie. We investigated the effects of Se (0.5, 1, 2, 5, or 10 μM) on ramie growth, Sb uptake and speciation, antioxidant responses, and ionomic profiling in ramie under 10 mg/L of SbIII or antimonate (SbV) stresses. Results revealed that the addition of 0.5 μM Se significantly increased shoot biomass by 75.73% under SbIII stress but showed minimal effects on shoot and root length in both SbIII and SbV treatments. Under SbIII stress, 2 μM Se significantly enhanced Sb concentrations by 48.42% in roots and 62.88% in leaves. In the case of SbV exposure, 10 μM Se increased Sb content in roots by 42.57%, and 1 μM Se led to a 91.74% increase in leaves. The speciation analysis suggested that Se promoted the oxidation of SbIII to less toxic SbV to mitigate Sb toxicity. Additionally, Se addition effectively minimized the excess reactive oxygen species produced by Sb exposure, with the lowest malondialdehyde (MDA) content at 0.5 μM Se under SbIII and 2 μM Se under SbV, by activating antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione peroxidase. Ionomic analysis revealed that Se helped in maintaining the homeostasis of certain nutrient elements, including magnesium, potassium (K), calcium (Ca), iron (Fe), and copper (Cu) in the SbIII-treated roots and K and manganese (Mg) in the SbV-treated roots. The results suggest that low concentrations of Se can be employed to enhance the phytoremediation of Sb-contaminated soils using ramie.

The potential of soil microbial communities to transform deoxynivalenol in agricultural soils-a soil microcosm study.

Infestation of cereal fields with toxigenic Fusarium species is identified as an environmental source for the mycotoxin deoxynivalenol (DON). During rain events, DON may be washed off from infested plants and enter the soil, where microbial transformation may occur. Although some studies showed DON transformation potential of soil microbial communities in liquid soil extracts, these findings can not be transferred to environmental conditions. Accordingly, microbial transformation of DON in soil has to be investigated under realistic conditions, e.g., microcosms mimicking field situations. In this study, we investigated the potential of soil microbial communities to transform DON in six different agricultural soils at two levels (0.5 and 5 µg g-1). The dissipation and the formation of transformation products were investigated in a period of 35 days and compared to a sterilized control. In addition, we measured soil respiration and applied the phospholipid-derived fatty acid (PLFA) analysis to assess whether soil microbial community characteristics are related to the microbial transformation potential. Dissipation of DON in non-sterilized soils was fast (50% dissipation within 0.6-3.7 days) compared to the sterile control where almost no dissipation was observed. Thus, dissipation was mainly attributed to microbial transformation. We verified that small amounts of DON are transformed to 3-keto-deoxynivalenol (3-keto-DON) and 3-epi-deoxynivalenol (3-epi-DON), which were not detectable after 16-day incubation, indicating further transformation processes. There was a trend towards faster transformation in soils with active and large microbial communities and low fungi-to-bacteria ratio.

Laser-induced graphene electrochemical sensor for quantitative detection of phytotoxic aluminum ions (Al3+) in soils extracts

Aluminum in its Al3+ form is a metal that inhibits plant growth, especially in acidic soils (pH < 5.5). Rapid and accurate quantitative detection of Al3+ in agricultural soils is critical for the timely implementation of remediation strategies. However, detecting metal ions requires time-consuming preparation of samples, using expensive instrumentation and non-portable spectroscopic techniques. As an alternative, electrochemical sensors offer a cost-effective and minimally invasive approach for in situ quantification of metal ions. Here, we developed and validated an electrochemical sensor based on bismuth-modified laser-induced graphene (LIG) electrodes for Al3+ quantitative detection in a range relevant to agriculture (1–300 ppm). Our results show a linear Al3+ detection range of 1.07–300 ppm with a variation coefficient of 5.3%, even in the presence of other metal ions (Pb2+, Cd2+, and Cu2+). The sensor offers a limit of detection (LOD) of 0.34 ppm and a limit of quantification (LOQ) of 1.07 ppm. We compared its accuracy for soil samples with pH < 4.8 to within 89–98% of spectroscopic methods (ICP-OES) and potentiometric titration. This technology's portability, easy to use, and cost-effectiveness make it a promising candidate for in situ quantification and remediation of Al3+ in agricultural soils and other complex matrices.

Assessment of Common Factors Associated with Droplet Digital PCR (ddPCR) Quantification of Paratrichodorus allius in Soil.

This research investigated the factors associated with the quantitative detection of Paratrichodorus allius in soil using droplet digital PCR (ddPCR). Small-sized nematodes exhibited significantly lower DNA quantities compared to their medium and large counterparts. Soil pre-treatments (room temperature drying and 37 °C oven-drying) demonstrated no substantial impact on ddPCR detection, and soil storage (0-3 months at 4 °C) exhibited negligible alterations in DNA quantities. A commercial DNA purification kit improved the resulting quality of ddPCR, albeit at the cost of a notable reduction in DNA quantity. Upon assessing the impact of inhibitors from soil extracts, a higher inhibitor concentration (5%) influenced ddPCR amplification efficiency. Incorporating bovine serum albumin (BSA) (0.2 μg/μL or 0.4 μg/μL) into the ddPCR setup mitigated the issue. In brief, while ddPCR exhibits minimal sensitivity to soil pre-treatments and storage, higher concentrations of PCR inhibitors and the DNA purification process can influence the results. Despite ddPCR's capability to detect nematodes of all sizes, quantification may not precisely reflect soil population. Incorporating BSA into the ddPCR setup enhances both detection and quantification capacities. This study represents the first comprehensive investigation of its kind for plant-parasitic nematodes, providing crucial insights for application of ddPCR in nematode diagnosis directly from the soil DNA.

Revitalizing Degraded and Abandoned Lands: Reflections from Local Government Involvement in Mud Brick Production - Tanzania

The study assessed local government involvement in revitalising abandoned holes and degraded lands around brick-making sites in Morogoro Municipality. Specifically, it delineated the effects of mudbrick-making activities on the communities surrounding the brick-making sites, identified alternative uses of the abandoned holes in the brick-making sites, and established the knowledge required by the community and brick-makers for improving abandoned land use for sustainability. Several techniques were utilised in data collection, including interviews and focus group discussions with village and ward leaders, district environmental officers, district community development officers, district planners, mud brick makers, and some members of the community from three specific wards, namely Kauzeni, Mindu, and Kihonda Maghorofani. The findings revealed a significant contribution of the mudbrick-making industry to enhancing income and improving the living standards of communities through employment creation. Particularly, women were involved in selling food to brick makers, while youth actively participated in brick-making activities. The abandoned holes resulting from soil extraction were repurposed for fishing, vegetable cultivation, and sugar cane production. The income accrued from these activities improved housing standards and increased social interaction among people from different regions, including seasonal migrants attracted to brick-making activities. Despite the noted positive effects, mud brick activities contributed significantly to land degradation due to the traditional technologies used in the process, resulting in large holes that posed risks to human and livestock lives. The study recommends enhancing brick makers' and landowners' awareness of implementing mud brick-making activities with appropriate sustainable environmental protection to improve the socio-economic status of both brick makers and the broader community.

Modern instrumentation and practical application of flame atomic emission spectrometry

The modern instrumentation for flame atomic emission spectrometry (FAES) is overviewed: the main technical (composition of the fuel gas used, dispersing element, number of analytical channels, reference channel, detecting element, sampling method) and analytical (determined elements, range of determined concentrations, limits and the accuracy of their determination, the duration of a single measurement, the equired amount of the analyzed sample) characteristics of flame photometers for industrial and clinical use as well as spectrophotometers currently made by various manufacturers such as Sherwood Scientific Ltd., BWB Technologies UK Ltd., Labtron Equipment Ltd., Labnics Equipment Ltd. and JENWAY Ltd (UK); A.KRÜSS Optronic (Germany); Cole Parmer Instrument Company and Labfon Equipment Inc. (USA); Inesa Analytical Instrument Co., Ltd (China); OJSC Zagorsk Optical and Mechanical Plant, Unico-SIS LLC and VMK-Optoelectronics LLC (Russia); Manti Lab Solutions, Labtronics, Systonic, Globe Instruments, Electronics India, Lasany (India). The main areas of application of FAES are presented – bioenergy, agriculture (analysis of plants, soil extracts and fertilizers), mineral raw materials (geology), clinical medicine and pharmaceuticals, food industry, environmental control (analysis of drinking, technical and waste water), nuclear energy, metallurgy and chemical industry, as well as some features and problems associated with the preparation of samples for analysis by the FAES method. The review includes references to works on the practical application of FAES, published mainly from 1998 to 2023.

Antimony mobility in soil near historical waste rock at the world's largest Sb mine, Central China

Soil near waste rock often contains high concentrations of antimony (Sb), but the mechanisms that mobilize Sb in a soil closely impacted by the waste rock piles are not well understood. We investigated these mobility mechanisms in soils near historical waste rock at the world's largest Sb mine. The sequential extraction (BCR) of soil reveal that over 95 % Sb is present in the residual fraction. The leached Sb concentration is related to the surface protonation and deprotonation of soil minerals. SEM-EDS shows Sb in the soil is associated with Fe and Ca. Moreover, X-ray absorption spectroscopy (XAS) results show Sb is predominantly present as Sb(V) and is associated with Fe in the form of tripuhyite (FeSbO4) as well as edge- and corner-sharing complexes on ferrihydrite and goethite. Thus, Fe in soils is important in controlling the mobility of Sb via surface complexation and co-precipitation of Sb by Fe oxides. The initially surface-adsorbed Sb(V) or co-precipitation is likely to undergo a phase transformation as the Fe oxides age. In addition, Sb mobility may be controlled by small amounts of calcium antimonate. These results further the understanding of the effect of secondary minerals in soils on the fate of Sb from waste rock weathering and inform source treatment for Sb-contaminated soils.

Arbuscular mycorrhizal fungi and rhizobia accelerate plant growth and N accumulation and contribution to soil total N in white clover by difficultly extractable glomalin-related soil protein

Arbuscular mycorrhizal fungi and rhizobia are soil symbiotic microorganisms involved in plant nitrogen (N) acquisition, whereas it is unclear how single or combined inoculation of both contributes to soil total N in legume crops. This study analyzed the effects of single or combined inoculation with arbuscular mycorrhizal fungus (Paraglomus occultum) and rhizobium (Rhizobium leguminosarum bv. trifolii) on growth performance, root soluble protein, leghemoglobin, NH4+-N, NO3−-N, and N concentrations, nitrogenase activities, soil total N contents, N contents in glomalin-related soil protein (GRSP), as well as the contribution of N in GRSP to soil total N in white clover. Twelve weeks after inoculation, P. occultum promoted nodule formation, and R. leguminosarum bv. trifolii accelerated root mycorrhizal colonization. Single or combined inoculation with P. occultum and R. leguminosarum bv. trifolii improved biomass, root total length, surface area and volume, root soluble protein concentrations, nodule leghemoglobin concentrations, and nitrogenase activities to varying degrees, with the trend of improvement being more pronounced with combined inoculation. R. leguminosarum bv. trifolii and/or P. occultum significantly increased NO3−-N, NH4+-N, and total N concentrations in nodules and roots, as well as soil total N concentrations. The N in easily extractable GRSP (EE-GRSP) and difficultly extractable GRSP (DE-GRSP) was 4.37–5.64 mg/g and 6.69–7.83 mg/g, respectively, contributing 2.68–3.26 % and 2.28–3.10 % of soil total N. P. occultum and combined inoculation accelerated the production of EE-GRSP and DE-GRSP and N in EE-GRSP. R. leguminosarum bv. trifolii not only significantly increased DE-GRSP production but also reduced N in DE-GRSP. R. leguminosarum bv. trifolii or P. occultum significantly increased the contribution of N in DE-GRSP, not EE-GRSP, to soil total N. It was concluded that arbuscular mycorrhizal fungus and rhizobium accelerated N accumulation and contribution to soil total N in white clover by DE-GRSP.

Correlation between electrical conductivity in saturated paste extracts and different diluted extracts (1/2.5, 1/5) of coarse-textured soils

Soil salinity poses a significant challenge to agricultural productivity, necessitating precise measurement methods. Rather than relying on complex determinations like saturated paste extracts (ECe), a practical alternative involves assessing soil salinity through the Electrical Conductivity (EC) of soil-water extracts. This simplified yet reliable method is crucial for understanding the impact of soil salinity on agricultural yields. To improve accuracy in representing soluble salts relevant to plant growth, the conversion of EC from soil water extracts to ECe becomes pivotal.In an experimental study, a clear relationship was sought between the Electrical Conductivity (EC) of saturated paste extracts (ECe) and the ratios found in soil-water extracts (1/2.5 and 1/5). Fifty samples of coarse-textured soil were collected from the Djamâa palm grove in Sidi Yahia village, located in the Oued Righ region within the Djamaa Zone. The analysis of the collected data revealed compelling findings, indicating a robust and statistically significant correlation between values obtained from ECe and those derived from EC1/2.5 and EC1/5 (correlation coefficient of R = 0.93 and 0.91, at a significance level of P = 0.05). These results highlight the promising potential of accurately estimating ECe in coarse-textured soils by employing EC1/2.5 and EC1/5, paving the way for streamlining assessment methodologies for soil salinity. This study not only elucidates the correlation between conductivity measures but also proposes a practical means to estimate soil salinity more efficiently. The findings contribute to informed decision-making in agricultural practices within the Northern Sahara's Djamâa palm grove and similar regions, offering valuable insights for sustainable soil management.

Integrating liquid chromatography-electrochemical detection-surface Enhanced Raman Spectroscopy on microfluidic chip for phenylurea herbicides analysis

The widespread use of phenylurea herbicides (PHs) is a serious threat to human health and environmental safety. These pollutants usually have similar molecular structures but distinct toxicities. Therefore, developing rapid detection methods to analyze PHs quantitatively and qualitatively is highly desirable. This study fabricated a microfluidic glass liquid chromatography (LC) coupled with electrochemical detection (ECD) and Surface-Enhanced Raman spectroscopy (SERS) synchronous system, which demonstrated excellent separation and analysis performance for PHs. The complete separation of three PHs could be achieved using the microfluidic chip LC with a theoretical plate number of 342525 plates m–1. The limit of detection (LOD) of the PHs for optimized electrochemical analysis reached 0.0099–0.1388 mmol/L. More importantly, the detection system integrated with ECD and SERS had high sensitivity and molecular recognition ability, with intra and inter-day precision of less than 6.7630% and 7.5601%, respectively. The recovery of the PHs could reach 102.9861% when this detection system was applied to the analysis of soil extracts in the small potted plant and actual water samples in the environment. It is expected that the microfluidic chip with the LC-ECD-SERS synchronous detection system has significant potential in various environmental, food safety, drug, and biomedical analyses.

Effects of Pyrolysis Temperature and Acid-Base Pre-Treatment on the Synthesis of Biochar-Based Slow-Release Selenium Fertilizer and Its Release in Soil.

Plant-derived selenium is an important source of selenium (Se) for humans, which, however, has been restricted by a low content of Se in soil. Traditional Se fertilizers have tended to result in low selenium utilization. Thus, it was necessary to develop a new slow-release material to control Se fertilizer release. In this study, biochar pyrolyzed at 300 °C and 800 °C was cross-linked with polyethyleneimine (PEI) after being treated with HNO3 or NaOH (which were labeled Acid-W300, Acid-W800, Alkali-W300, and Alkali-W800). The results showed that the maximum adsorption capacities of Acid-W300, Alkali-W300, Acid-W800, and Alkali-W800 were 329.16 mg/g, 321.93 mg/g, 315.04 mg/g, and 344.33 mg/g, respectively. Among them, Acid-W800 and Alkali-W800 were mainly imine- and amide-bonded with SO32-, while Acid-W300 and Alkali-W300 were loaded with SO32- by forming the C-Se bonding as well as through imine- and amide-bonding. The release of four biochar-based selenium fertilizers in the red soil and brown soil extracts conformed to the pseudo-second-order kinetic model. The release rate and release amount of four biochar-based selenium fertilizers in the red soil extract were higher than those in the brown soil extract. Alkali-W800-Se had a higher proportion of Se-exchangeable release, accounting for 87.5% of the total loaded selenium, while Acid-W300-Se had the lowest proportion at 62.2%. However, the Se releases of Alkali-W800-Se were more than 42.49% and 37.67% of the total Se-loading capacity during 5 days of continuous red soil extraction and brown soil extraction, respectively. Acid-W300-Se released less than 20% of the total Se-loading capacity. Thus, Acid-W300-Se was the recommended slow-release Se fertilizer in red soil and brown soil.

Biocontrol potential of some selected native bacterial antagonists against tomato (&lt;em&gt;Solanum lycopersicum&lt;/em&gt; L.) early blight causal agent &lt;em&gt;Alternaria alternata&lt;/em&gt;

Seven selected bacterial antagonists isolated from healthy tomato rhizosphere and phyllosphere were evaluated for their biocontrol efficacy against the tomato early blight causal agent Alternaria alternata under in vitro conditions. The causal organism of early blight of tomato was isolated from a tomato leaf sample which showed early blight symptoms and verified it as Alternaria alternata. Healthy tomato rhizosphere soil, fructosphere and phyllosphere extracts were used as the potential sources of antagonists. Thirty bacterial isolates from tomato rhizosphere soil and 22 bacterial isolates from tomato phyllosphere were isolated using serial dilution technique. Out of those isolates, 24 were subjected to antagonists screening procedure. It was observed that, all the bacterial isolates except RA 5, RA 21, PA 1, PA 2, inhibited the growth of A. alternata significantly (p&lt;0.05) in co-cultivation and dual culture showing an average radial growth inhibition of 69 %. Seven different bacterial isolates coded as RA 8, RA 12, RA 17, RA 18, RA 29, PA 4 and PA 12 were selected for further studies. Based on 16 S rRNA analysis, four of these antagonists were identified as Bacillus thuringiensis, Bacillus cereus and Pseudomonas sp. Microscopic observations of A. alternata hyphae subjected to antagonism showed deviations from the normal hyphae including thickenings, swellings and vacuolation. Inhibition of A. alternata spore germination by selected antagonists was significant at p&lt;0.05 level with an average inhibition of 83.7 %. All the selected antagonists produced diffusible antifungal substances and showed hyperparasitism and competition as their mechanisms in antagonizing the fungal pathogen A. alternata. These results suggested that these seven bacterial isolates can be further explored as potential biocontrol agents in controlling early blight disease in tomato.

Study of factors affecting the remediation of contaminated soil through pneumatic fracturing and soil vapor extraction

In low-permeability soils, the effectiveness of soil vapor extraction (SVE) is often constrained, resulting in increased time and operational expenses. In this study, pneumatic fracturing and the SVE were combined to remediate low-permeability clay contaminated with ammonia gas. The soil parameters, pneumatic fracturing parameters, extraction mode, and other influencing factors were investigated via laboratory testing. The results indicated that: (1) Pneumatically induced fracturing disrupts soil structure, forming cracks and providing new pathways for ammonium gas migration; (2) the soil crack area exhibits a quadratic function relationship with both the fracturing pressure and frequency, and the soil crack area increases with higher pneumatic frequencies, leading to a faster pneumatic pressure decline; (3) a denser network of pathways emerges within the soil due to the reduced distance between the two pneumatic fracturing points, consequently enhancing soil permeability and increasing pollutant elimination efficiency; (4) the ammonium gas removal efficiency gradually increases with an increase in the extracted vapor flow rate, but there is an optimal extraction flow rate (9 L/min); (5) continuous extraction combined with gas injection effectively ameliorates the issue of prolonged fluctuations in ammonium gas concentration during the later stages of extraction. (6) Fracturing and extraction reduce the moisture content of the surrounding soil. The results demonstrated the feasibility and superiority of pneumatic pre-fracturing extraction in low-permeability soils.