Can site-specific nutrient management improve the productivity and resource use efficiency of climate-resilient finger millet in calcareous soils in India?

Finger millet, an important 'Nutri-Cereal' and climate-resilient crop, is cultivated as a marginal crop in calcareous soils. Calcareous soils have low organic carbon content, high pH levels, and poor structure. Such a situation leads to poor productivity of the crop. Site-specific nutrient management (SSNM), which focuses on supplying optimum nutrients when a crop is needed, can ensure optimum production and improve the nutrient and energy use efficiency of crops. Moreover, developing an appropriate SSNM technique for this crop could offer new insights into nutrient management practices, particularly for calcareous soils. A field experiment was conducted during the rainy seasons of 2020 and 2021 in calcareous soil at Dr. Rajendra Prasad Central Agricultural University, Pusa, India. The experiment consisted of 8 treatments, viz. control, nitrogen (N)/phosphorus (P)/potassium (K)-omission, 75 %, 100 %, and 125 % recommended fertilizer dose (RFD), and 100 % recommended P and K + 30 kg ha-1 N as basal + rest N as per GreenSeeker readings. From this study, it was observed that the GreenSeeker-based SSNM resulted in the maximum grain yield (2873 kg ha-1), net output energy (96.3 GJ ha-1), and agronomic efficiency of N (30.6 kg kg-1), P (68.9 kg kg-1), and K (68.9 kg kg-1). The application of 125 % RFD resulted in ∼7 % lower yield than that under GreenSeeker-based nutrient management. Approximately 12 % greater energy use efficiency and 21-36 % greater nutrient use efficiency were recorded under GreenSeeker-based nutrient management than under 125 % RDF. The indigenous supplies of N, P, and K were found to be 14.31, 3.00, and 18.51 kg ha-1, respectively. Thus, 100 % of the recommended P and K + 30 kg ha-1 N as basal + rest N according to GreenSeeker readings can improve the yield, nutrient use efficiency, and energy balance of finger millet in calcareous soils.

How the Ecology of Calcified Red Macroalgae is Investigated under a Chemical Approach? A Systematic Review and Bibliometric Study.

Characteristics such as calcareous morphology and life cycle are used to understand the ecology of calcified rhodophytes. However, there is limited information regarding their chemical profiles and biological activities. Therefore, a systematic review (PRISMA) was conducted to assess the influence of the chemistry of calcareous rhodophytes on ecological interactions in the marine environment. The keywords used were: ["Chemical AND [Ecology OR Interaction OR Response OR Defense OR Effect OR Cue OR Mediated OR Induce]"] AND ["Red Seaweed" OR "Red Macroalgae" OR Rhodophy?] AND [Calcified OR Calcareous] in Science Direct, Scielo, PUBMED, Springer, Web of Science, and Scopus. Only English articles within the proposed theme were considered. Due to the low number of articles, another search was conducted with three classes and 16 genera. Finally, 67 articles were considered valid. Their titles, abstracts, and keywords were analyzed using IRaMuTeQ through factorial, hierarchical and similarity classification. Most of the studies used macroalgae thallus to evaluate chemical mediation while few tested crude extracts. Some substances were noted as sesquiterpene (6-hydroxy-isololiolide), fatty acid (heptadeca5,8,11-triene) and dibromomethane. The articles were divided into four classes: Herbivory, Competition, Settlement/Metamorphosis, and Epiphytism. Crustose calcareous algae were associated with studies of Settlement/Metamorphosis, while calcified algae were linked to herbivory. Thus, the importance of chemistry in the ecology of these algae is evident,and additional studies are needed to identify the substances responsible for ecological interactions. This study collected essential information on calcified red algae, whose diversity appears to be highly vulnerable to the harmful impacts of ongoing climate change.

Partial incision blunt scissors lamellar keratectomy under topical anesthesia for the treatment of presumed calcific corneal degeneration in dogs.

OBJECTIVE: The aim of the study was to investigate clinical features of lamellar keratectomy for presumed calcific corneal degeneration in a population of geriatric dogs using blunt scissors dissection under topical anesthesia. ANIMALS STUDIED AND PROCEDURES: Retrospective analysis of dogs with clinically diagnosed calcific degeneration treated by keratectomy under topical anesthesia between 2015 and 2021 at two veterinary ophthalmology practices was performed. Descriptive data regarding signalment, concurrent systemic and ocular disease, complications, healing time, and recurrence were collected. Kaplan-Meier survival analysis was performed to calculate 1-year recurrence probability. RESULTS: Sixty-five eyes in 57 dogs met inclusion criteria. All 54 eyes with follow-up healed within a median of 14 days (7-74), including 17 with complicating factors of infection or deep stromal ulceration. Globe rupture occurred intraoperatively in three eyes (4.6%), for which subsequent conjunctival graft was performed. Calculated 1-year recurrence probability from 47 eyes followed long term was 25%. Multivariate Cox proportional hazard modeling showed a significant association between documented systemic disease and time to recurrence (p = .035), irrespective of topical EDTA use (p = .432). Median follow-up time available for all cases was 249 days. CONCLUSIONS: Blunt lamellar dissection with corneal scissors can be performed in dogs under topical anesthesia, yielding healing times and recurrence comparable to previously reported treatments for calcific corneal degeneration. Globe rupture is an inherent risk of both the disease and procedure and occurred in 4.6% of treated eyes. This approach expands non-anesthetic treatment options for affected patients but should only be performed with advanced microsurgical training and client counseling on individual risk and benefit.

Transport and preservation of calcareous and organic-walled dinoflagellate cysts off Cape Blanc (NW africa) in relation to nepheloid layers.

Our understanding of dinoflagellates' present-day and past ecology is limited due to the scarcity of data on the transport of dinoflagellate cysts in oceanic environments. Previous studies have shown that lateral transport affects the source-to-sink trajectory of cysts in the very productive region off Cape Blanc (NW Africa). Unsolved questions remain, such as: how far these cysts can be advected, whether the cyst sources vary over time and whether lateral transport is a permanent feature or restricted to individual events. To fill these gaps and assess the role of nepheloid layers on the lateral transport and preservation of dinoflagellate cysts, new data on dinoflagellate cyst distributions in the water column and sediments along a land-sea transect were obtained. Samples were collected in November 2018 along a shelf break-offshore transect during intense upwelling, notably, within and between the nepheloid layers. The composition and abundance of cysts with organic walls in the water column and surface sediments were studied. Moreover, the distribution of calcareous cysts was also analysed in the water samples, using non-destructive acid-free preparation methods. The records were dominated by empty cysts, but no clear indications that these originated from local resuspension of older sediments were observed. Clustering, principal component analysis and redundant discriminant analysis were used to compare cyst assemblages in the water column and surface sediments, and environmental conditions in the upper water column. The strong similarity in species composition of water samples collected in the active upwelling region to those collected from the more onshore parts of the Benthic Nepheloid Layer (BNL), upper Intermediate Nepheloid Layer (INL) (∼1000 m depth) and lower INL (∼2200 m depth) indicated that lateral transport of cysts within these NLs occurred until about ∼110 km from the shelf break. Cyst assemblages from above and below these NLs showed significantly different taxa composition reinforcing the role of NLs in the lateral advection of cysts. In the more offshore stations, vertically similar cyst assemblages were observed in the same station, independent of the sample depth, within or between the NLs, which supported that at these stations vertical transport was the dominant process influencing cyst assemblages. Consequently, the cyst signal in sediments off Cape Blanc may be affected both by horizontal transport of allochthonous cysts and vertical deposition of locally-produced cysts, particularly in the more offshore stations (>2000 m depth). Despite lateral transport and possible species-specific preservation effects, horizontal distributions of most cyst taxa in the water column and the surface sediments could be explained to a great extent by the main environmental gradients in the upper water column. This agrees with observations made in other regions, and reinforces that dinoflagellate cysts as good proxies to reconstruct past environmental conditions in offshore environments. New data on dinoflagellate cyst distribution, transport and accumulation patterns in deep environments off Cape Blanc may be useful for interpreting past environmental signals in the region. This is particularly relevant regarding calcareous cysts, as information on their distribution and ecology is very scarce. The present work contributes to a better understanding of the dispersal patterns of dinoflagellate cysts in the deep ocean, highlighting the significant role played by nepheloid layers in this process and thus on the dinoflagellate cyst signature in deep-sea sediments.

Enhancing Load-Bearing Capacity of Calcareous Sands through Gel Stabilization: A Mechanical and Material Characterization Study.

Calcareous sands often display wide ring grain configurations, high intragranular porosity, a complex structure, and low grain hardness. These attributes typically do not meet the strength criteria necessary to sustain overlying infrastructure in civil engineering applications. This study investigates gel stabilization techniques, blending gel material with calcareous sand at concentrations ranging from 5% to 22%, followed by curing periods of 3 to 28 days to evaluate the load-bearing capacity. Subsequently, an unconfined compressive test is performed to determine the gel material content in stabilized specimens and investigate the influence of gel material types. The gel material-to-sand ratios employed are set at 5%, 10%, and 16% for Portland cement and 13%, 16%, and 22% for gypsum. After that, a triaxial consolidated undrained test is conducted to assess mechanical behavior, pore water pressure, and mechanical properties. The findings reveal increased dilation, stress-strain hardening, and softening post-yield, regardless of gel material type. Principal stress ratios, secant modulus, and cohesion show a positive correlation with maintenance duration and binder content, with implications for improved load-bearing capacity. The study also elucidates the qualitative relationship between secant modulus E50 and confining pressure.

Experimental Study on Mechanical Properties and Permeability Characteristics of Calcareous Mudstone under Different Confining Pressures.

Calcareous mudstone, a type of red-bed soft rock, is prevalent in the surrounding rock of the Central Yunnan Water Diversion Project (CYWDP) in Yunnan Province, China, significantly impacting both construction and operation. The mechanical properties of calcareous mudstone vary with depth. This study investigates its mechanical properties, permeability characteristics, energy evolution, and macro- and micro-failure characteristics during deformation using triaxial compression tests under different confining pressures. Results reveal distinct stage characteristics in the stress-strain behavior, permeability, and energy evolution of calcareous mudstone. Crack propagation, permeability evolution, and energy dissipation are closely linked, elucidating the deformation and failure process, with fluid pressure playing a crucial role. The confining pressure σ3 increased from 2 MPa to 4 MPa and 6 MPa, while the peak stress σc (Pw = 1 MPa) of the calcareous mudstone increased by 84.49% and 24.89%, respectively. Conversely, the permeability at σc decreased from 11.25 × 10-17 m2 to 8.99 × 10-17 m2 and 5.72 × 10-17 m2, while the dissipative energy at σc increased from 12.39 kJ/m3 to 21.14 kJ/m3 and 42.51 kJ/m3. In comparison to those without fluid pressure (Pw = 0), the value of σc at Pw = 1 MPa was reduced by 36.61%, 23.23%, and 20.67% when σ3 was 2, 4, and 6 MPa, respectively. Increasing confining pressure augments characteristic stresses, deformation and failure energy, and ductility, while reducing permeability, crack propagation, and width. These findings enhance our understanding of calcareous mudstone properties at varying depths in tunnel construction scenarios.

Assessing Soil Quality, Wheat Crop Yield, and Water Productivity under Condition of Deficit Irrigation.

Wheat is one of the most important cereal crops in Egypt and all over the world. Its productivity is adversely affected by drought due to deficient irrigation to provide nutrients required for plant growth. In a field experiment, silicon foliar applications at concentrations of 0, 200, and 400 mg L-1 were performed at different irrigation rates ranging from 1000 to 4000 m3 ha-1 to assess water irrigation productivity and wheat crop yield in a calcareous soil under arid climate conditions. Increased irrigation rates led to a significant increase in soil nutrient dynamics, as well as in the number and weight of grains per spike, leaf area index, grain yield, straw yield, and biological yield, with the exception of the weight of 1000 grains. Spraying with sodium silicate had a significant impact on grain yield and harvest index but did not significantly impact the other traits. Furthermore, the interaction between irrigation and silicate application rates showed significance only for grain yield, the number of spikes/m2, and the harvest index. Applying three times irrigation could produce the highest nutrient retention, wheat yield, and water irrigation productivity. No significance was observed between 3000 m3 ha-1 and 4000 m3 ha-1 irrigation, indicating a saving of 25% of applied irrigation water. It can be concluded that applying irrigation at 3000 m3 ha-1 could be a supplemental irrigation strategy. High wheat grain yield can be achieved under deficit irrigation (3000 m3 ha-1) on the northwestern coast of Egypt with an arid climate by spraying crops with sodium silicate at a rate of 400 mg L-1.

Forecast the Habitat Sustainability of Schoenus ferrugineus L. (Cyperaceae) in the Southern Urals under Climate Change.

An analysis of the current potential range of the Pleistocene relict plant species Schoenus ferrugineus and modeling of changes in its future range under moderate (RCP4.5) and strong (RCP8.5) climate change in the middle and second half of the 21st century were carried out. The MaxEnt program was used for modeling. Climate variables from CHELSA Bioclim, the global digital soil mapping system SoilGrids, and a digital elevation model were used as predictors. Modeling has shown that climate change will lead to a significant reduction in the suitability of S. ferrugineus habitat conditions by the mid-21st century. The predicted changes in the distribution of habitats of S. ferrugineus, a diagnostic species of calcareous mires and an indicator of their ecological state, indicate a possible strong transformation of wetland complexes in the Southern Urals region even under moderate climate change. A reduction in the distribution of S. ferrugineus at the eastern limit of its range will also be facilitated by more frequent extreme droughts. To maintain the distribution of S. ferrugineus on the eastern border of its range, a number of measures are proposed to mitigate the negative consequences of climate change, contributing to the preservation of the hydrological regime of calcareous mires.

Assessment of soil fertility and nutrient management strategies in calcareous soils of Khuzestan province: a case study using the Nutrient Index Value method.

Soil fertility (SF) is a crucial factor that directly impacts the performance and quality of crop production. To investigate the SF status in agricultural lands of winter wheat in Khuzestan province, 811 samples were collected from the soil surface (0-25 cm). Eleven soil properties, i.e., electrical conductivity (EC), soil organic carbon (SOC), total nitrogen (TN), calcium carbonate equivalent (CCE), available phosphorus (Pav), exchangeable potassium (Kex), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), and soil pH, were measured in the samples. The Nutrient Index Value (NIV) was calculated based on wheat nutritional requirements. The results indicated that 100%, 93%, and 74% of the study areas for CCE, pH, and EC fell into the low, moderate, and moderate to high NIV classes, respectively. Also, 25% of the area is classified as low fertility (NIV < 1.67), 75% falls under medium fertility (1.67 < NIV value < 2.33), and none in high fertility (NIV value > 2.33). Assessment of the mean wheat yield (AWY) and its comparison with NIV showed that the highest yield was in the Ramhormoz region (5200 kg.ha-1), while the lowest yield was in the Hendijan region (3000 kg.ha-1) with the lowest EC rate in the study area. Elevated levels of salinity and CCE in soils had the most negative impact on irrigated WY, while Pav, TN, and Mn availability showed significant effects on crop production. Therefore, implementing SF management practices is essential for both quantitative and qualitative improvement in irrigated wheat production in Khuzestan province.

Ammonium addition reduces phosphorus leaching in a long-term mineral or organic fertilized calcareous soil during flooding conditions.

Organic amendment substitutes mineral fertilizers has been proven to increase the organic matter content of soils, which in turn may induce phosphorus (P) mobilization by triggering the redox reaction. However, under flooded conditions according to local agricultural practices, as one of the factors restricting the decomposition of organic matter, the role ammonium plays in P transformation and leaching from soils with different organic matter remains unclear. To address the knowledge gap, the calcareous soils were collected from a long-term field trial (>13 years) containing two treatments with equal P inputs: a long-term mineral fertilization and a long-term organic amendment. Both long-term mineral fertilized soil and long-term organic amended soil were split into ammonium applications or no ammonium applications. A series of column devices were deployed to create flooded conditions and monitor the P leaching from the collected soils. The K-edge X-ray absorption near-edge structure and sequential extraction method were employed jointly to detect soil P fractions and speciation, and the P sorption/desorption characteristics of soil were evaluated by Langmuir fitting. The results showed a reduction of cumulative leached P from soils by 33.2%-43.3% after ammonium addition, regardless of previous long-term mineral fertilization or organic amendment history. A significant enhancement of soil labile P pool (indicated by the H2O-P fraction and NaHCO3-P fraction) after ammonium addition results in the reduction in soil P leaching. The reduced P sorption capacity coupled with the transformation from hydroxyapatite to ß-tricalcium phosphate indicated that the phosphate retention is attributed to the precipitation formation rather than phosphate sorption by soil. The present study highlights that the ammonium addition could affect the phosphate precipitation transformation. This may be attributed to the effect of ammonium addition on the calcium and magnesium ion content and molar ratio in this soil, thereby regulating the form of soil phosphate precipitation. The mechanisms revealed in this study can support developing optimized agricultural management practices to alleviate soil P loss.

Flower-bee versus pollen-bee metanetworks in fragmented landscapes.

Understanding the organization of mutualistic networks at multiple spatial scales is key to ensure biological conservation and functionality in human-modified ecosystems. Yet, how changing habitat and landscape features affect pollen-bee interaction networks is still poorly understood. Here, we analysed how bee-flower visitation and bee-pollen-transport interactions respond to habitat fragmentation at the local network and regional metanetwork scales, combining data from 29 fragments of calcareous grasslands, an endangered biodiversity hotspot in central Europe. We found that only 37% of the total unique pairwise species interactions occurred in both pollen-transport and flower visitation networks, whereas 28% and 35% were exclusive to pollen-transport and flower visitation networks, respectively. At local level, network specialization was higher in pollen-transport networks, and was negatively related to the diversity of land cover types in both network types. At metanetwork level, pollen transport data revealed that the proportion of single-fragment interactions increased with landscape diversity. Our results show that the specialization of calcareous grasslands' plant-pollinator networks decreases with landscape diversity, but network specialization is underestimated when only based on flower visitation information. Pollen transport data, more than flower visitation, and multi-scale analyses of metanetworks are fundamental for understanding plant-pollinator interactions in human-dominated landscapes.

Recalcification stabilizes cadmium but magnifies phosphorus limitation in wastewater-irrigated calcareous soil.

Long-term wastewater irrigation leads to the loss of calcium carbonate (CaCO3) in the tillage layer of calcareous land, which irreversibly damages the soil's ability to retain cadmium (Cd). In this study, we selected calcareous agricultural soil irrigated with wastewater for over 50 years to examine the recalcification effects of sugar beet factory lime (SBFL) at doses of 0%, 2.5%, 5%, and 10%. We found that SBFL promoted Cd transformation in the soil from active exchangeable species to more stable carbonate-bonded and residual species, which the X-ray diffraction patterns also confirmed results that CdSO4 reduced while CdS and CaCdCO3 increased. Correspondingly, the soil bioavailable Cd concentration was significantly reduced by 65.6-84.7%. The Cd concentrations in maize roots and shoots were significantly reduced by 11.7-50.6% and 13.0-70.0%, respectively, thereby promoting maize growth. Nevertheless, SBFL also increased the proportion of plant-unavailable phosphorus (P) in Ca8-P and Ca10-P by 4.3-13.0% and 10.7-25.9%, respectively, reducing the plant-available P (Olsen P) content by 5.2-22.1%. Consequently, soil P-acquiring associated enzyme (alkaline phosphatase) activity and microbial (Proteobacteria, Bacteroidota, and Actinobacteria) community abundance significantly increased. Our findings showed that adding SBFL to wastewater-irrigated calcareous soil stabilized Cd, but exacerbated P limitation. Therefore, it is necessary to alleviate P limitations in the practice of recalcifying degraded calcareous land.

Photosynthetic physiological characteristics, growth performance, and element concentrations reveal the calcicole-calcifuge behaviors of three Camellia species.

We grew three yellow Camellia species (the calcifuge C. nitidissima and C. tunghinensis, and the calcicole C. pubipetala) in acidic and calcareous soils for 7 months and assessed their photosynthetic physiological characteristics, growth performance, and element concentrations in this developmental context. The calcifuge C. nitidissima and C. tunghinensis species exhibited poor growth with leaf chlorosis, growth stagnation, and root disintegration in calcareous soils, and with their P n, G s, T r, F v/F m, ΦPSII, ETR, qP, leaf Chla, Chlb, and Chl(a + b) concentrations, and root, stem, leaf, and total biomass being significantly lower when grown in calcareous soils relative to in acidic soils. In contrast, the calcicole C. pubipetala grew well in both acidic and calcareous soils, with few differences in the above parameters between these two soil substrates. The absorption and/or transportation of nutrient elements such as N, K, Ca, Mg, and Fe by the two calcifuge Camellia species plants grown in calcareous soils were restrained. Soil type plays a major role in the failure of the two calcifuge Camellia species to establish themselves in calcareous soils, whereas other factors such as competition and human activity are likely more important limiting factors in the reverse case. This study furthers our understanding of the factors influencing the distribution of these rare and endangered yellow Camellia species, allowing for improved management of these species in conservation projects and horticultural production.

Acute calcareous corneal degeneration in a patient with chronic graft-versus-host disease.

Objective: To describe acute calcareous corneal degeneration as a complication of chronic graft-versus-host disease. Materials and methods: Clinical case and review of the literature. Results: We presented a case of bilateral acute calcareous corneal degeneration in a patient with chronic graft-versus-host disease. Conclusions: Chronic graft-versus-host disease (cGVHD) occurs in 50-70% of bone marrow transplantation patients, the most frequent ocular complication being keratoconjunctivitis sicca (KCS). Calcareous corneal degeneration is a type of calcium deposition that can be secondary to chronic ocular inflammation or dry eye, but there are few cases reported of acute calcareous corneal degeneration and recurrent perforation in cGVHD. Abbreviations: GVHD = Chronic graft-versus-host disease, aGVHD = Acute graft-versus-host disease, cGVHD = Chronic graft-versus-host disease, KCS = Keratoconjunctivitis sicca, PKP = Penetrating keratoplasty, AMT = Amniotic membrane transplantation, PRGF = Plasma rich in growth factors, OD = Right eye, OS = Left eye.

Impact of regenerative farming practices on soil quality and yield of cotton-sorghum system in semi arid Indian conditions.

Regenerative agricultural practices, i.e. organic and natural farming, are rooted in India since ancient times. However, the high cost of production, lack of organic pest control measures and premium price of organic produces in chemical agriculture encourage natural farming. In the present study, the quality improvement of calcareous soils under organic (OGF) and natural (NTF) management was compared with integrated conventional (ICF) and non-invasive (NIF) farming practices with cotton-sorghum crops over three consecutive years. A total of 23 soil attributes were analyzed at the end of the third cropping cycle and subjected to principal component analysis (PCA) to select a minimum data set (MDS) and obtain a soil quality index (SQI). The attributes soil organic carbon (SOC), available Fe, pH, bulk density (BD) and alkaline phosphatase (APA) were selected as indicators based on correlations and expert opinions on the lime content of the experimental soil. The SQI was improved in the order of OGF (0.89) > NTF(0.69) > ICF(0.48) > NIF(0.05). The contribution of the indicators to SQI was in the order of available Fe (17-44%) > SOC (21-28%), APA (11-36%) > pH (0-22%), and BD (0-20%) regardless of the farming practices. These indicators contribute equally to soil quality under natural (17-22%) and organic (18-22%) farming. The benefit:cost ratio was calculated to show the advantage of natural farming and was in the order of NTF(1.95-2.29), ICF (1.34-1.47), OGF (1.13-1.20) and NIF (0.84-1.47). In overall, the natural farming significantly sustained the soil quality and cost benefit compared to integrated conventional farming practices.

Growing on calcareous soils and facing climate change.

Soil calcium carbonate (CaCO3) impacts plant mineral nutrition far beyond Fe metabolism, imposing constraints for crop growth and quality in calcareous agrosystems. Our knowledge on plant strategies to tolerate CaCO3 effects mainly refers to Fe acquisition. This review provides an update on plant cellular and molecular mechanisms recently described to counteract the negative effects of CaCO3 in soils, as well as recent efforts to identify genetic bases involved in CaCO3 tolerance from natural populations, that could be exploited to breed CaCO3-tolerant crops. Finally, we review the impact of environmental factors (soil water content, air CO2, and temperature) affecting soil CaCO3 equilibrium and plant tolerance to calcareous soils, and we propose strategies for improvement in the context of climate change.

Influence of Calcareous Deposits on Hydrogen Embrittlement Susceptibility of Q460 Steel.

Cathodic protection is widely used to protect structural steel from corrosion in marine environments. However, an inappropriate cathodic potential may lead to hydrogen embrittlement (HE). Therefore, this study investigates the relationship between cathodic protection potential, structure and composition of calcareous deposits, and hydrogen embrittlement susceptibility of Q460 steel. The slow strain rate test results and fracture analysis reveal that Q460 steel had the smallest HE susceptibility when covered with the calcareous deposits formed under -1.1 VSCE. The deposits have a relatively thin calcium-rich inner layer and a condensed magnesium-rich outer layer, which can significantly inhibit hydrogen entry. A sustained deposition reaction during slow strain rate testing (SSRT) in artificial seawater can also decrease the HE susceptibility of Q460 steel.

Experimental study on the effects of water content on the compression characteristics and particle breakage of calcareous sand.

The particle breakage effect and compression characteristics of calcareous sand are related to the water content in the sand material. However, the effects of water content on the particle breakage and compression characteristics of calcareous sand have rarely been investigated. In this work, 50 sets of confined compression tests were conducted on calcareous sand specimens, and the compression characteristics and particle breakage effects of two single-particle-size groups (particle size ranges of 1-0.5 mm and 0.5-0.25 mm) of calcareous sand were investigated under five different water contents. The test results showed that with the increase in the water content, the final compression deformation of calcareous sand was positively correlated with the water content. The final compression deformation decreased when the water content reached a certain value. The water content corresponding to the peak final compression deformation was related to the gradation of the calcareous sand; the specific values were 10% and 15% for particle size ranges of 1-0.5 mm and 0.5-0.25 mm, respectively. With the increase in the water content, the slope of the loading curve of calcareous sand appeared to increase and then decrease, reaching maximum when the water content was 10%. Moreover, the slope of the loading curve was close to twice that of the loading curve of dry sand, whereas the slope of the unloading curve changed little. Under the same water content, the initial gradation had no effect on the compression and unloading characteristics of the specimens beyond a vertical pressure of 1 MPa. The effects of the variation in the water content on the particle breakage of calcareous sand were mainly reflected in the softening effect of water on the specimen particles, which reduced the Mohr strength of the particles.

Ecotoxic effect in Allium cepa due to sphalerite weathering arising in calcareous conditions.

The ecotoxic effect of Zn species arising from the weathering of the marmatite-like sphalerite ((Fe, Zn)S) in Allium cepa systems was herein evaluated in calcareous soils and connected with its sulfide oxidation mechanism to determine the chemical speciation responsible of this outcome. Mineralogical analyses (X-ray diffraction patterns, Raman spectroscopy, scanning electron microscopy and atomic force microscopy), chemical study of leachates (total Fe, Zn, Cd, oxidation-reduction potential, pH, sulfates and total alkalinity) and electrochemical assessments (chronoamperometry, chronopotentiometry, cyclic voltammetry, and electrochemical impedance spectroscopy) were carried out using (Fe, Zn)S samples to elucidate interfacial mechanisms simulating calcareous soil conditions. Results indicate the formation of polysulfides (Sn2-), elemental sulfur (S0), siderite (FeCO3)-like, hematite (Fe2O3)-like with sorbed CO32- species, gunningite (ZnSO4·H2O)-like phase and smithsonite (ZnCO3)-like compounds in altered surface under calcareous conditions. However, the generation of gunningite (ZnSO4·H2O)-like phase was predominant bulk-solution system. Quantification of damage rates ranges from 75 to 90% of bulb cells under non-carbonated conditions after 15-30 days, while 50-75% of damage level is determined under neutral-alkaline carbonated conditions. Damage ratios are 70.08 and 30.26 at the highest level, respectively. These findings revealed lower ecotoxic damage due to ZnCO3-like precipitation, indicating the effect of carbonates on Zn compounds during vegetable up-taking (exposure). Other environmental suggestions of the (Fe, Zn)S weathering and ecotoxic effects under calcareous soil conditions are discussed.

Arsenic and cadmium simultaneous immobilization in arid calcareous soil amended with iron-oxidizing bacteria and organic fertilizer.

Immobilization stands as the most widely adopted remediation technology for addressing heavy metal(loid) contamination in soil. However, it is crucial to acknowledge that this process does not eliminate pollutants; instead, it confines them, potentially leaving room for future mobilization. Presently, our comprehension of the temporal variations in the efficacy of immobilization, particularly in the context of its applicability to arid farmland, remains severely limited. To address this knowledge gap, our research delves deep into the roles of iron-oxidizing bacteria (FeOB) and organic fertilizer (OF) in the simultaneous immobilization of arsenic (As) and cadmium (Cd) in soils. We conducted laboratory incubation and field experiments to investigate these phenomena. When OF was combined with FeOB, a noteworthy transformation of available As and Cd into stable species, such as the residual state and combinations with Fe-Mn/Al oxides, was observed. This transformation coincided with changes in soil properties, including pH, Eh, soluble Fe, and dissolved organic carbon (DOC). Furthermore, we observed synergistic effects between available As and Cd when treated with bacteria and OF individually. The stabilization efficiency of As and Cd, as determined by the Toxicity Characteristic Leaching Procedure, reached its highest values at 33.39 % and 24.67 %, respectively, after 120 days. Nevertheless, the formation of iron­calcium complexes was disrupted due to pH fluctuations. Hence, long-term monitoring and model development are essential to enhance our understanding of the remediation process. The application of organic fertilizer and the use of FeOB in calcareous soil hold promise for the restoration of polluted soil and the maintenance of soil health by mitigating the instability of heavy metals(loid).