Oil Fractions Research Articles

Physicochemical protection is more important than chemical functional composition in controlling soil organic carbon retention following long-term land-use change

Understanding the mechanisms that control soil organic carbon (SOC) persistence is central to soil management and climate change mitigation. In the present study, we utilised a chronosequence of Vertisols which have undergone land use change from native vegetation to cropping for up to 82 y in subtropical Australia. We examined whether the marked changes in SOC concentrations were associated with changes in the physicochemical protection of SOC in aggregate structures (occlusion) and mineral surfaces (adsorption) or with changes in chemical functional composition. Soil samples were fractionated using density and physical fractionation to isolate the free particulate organic matter (fPOM), occluded POM (oPOM) and fine mineral-associated organic matter (fine-MAOM) to assess the impact of land use change on soil organic matter (SOM) fractions with differing degrees of physicochemical protection. The impact of long-term cropping on SOC functional group composition across soil fractions was assessed using synchrotron-based near edge X-ray absorption fine structure (NEXAFS) analyses. We found that although long-term cropping caused a loss of 43 % of bulk SOC after 20 y, this marked loss over time was not associated with a change in C functional group composition. Furthermore, although the SOC retention in the various fractions differed up to 60-fold (fPOM-C decreased by 78 % after cropping for 20y, whilst fine-MAOM decreased by 25 %), there were only comparatively minor differences in SOC functional group composition between these fractions. Together, these findings suggest that the differences in C retention between fractions were less related to SOC functional group composition and more related to SOM’s physicochemical protection.

Ice nucleating ability of mineral particles from subtropical South American deserts

Mineral aerosols are one of the most important ice nucleating particles (INPs) because their efficiency in nucleating ice, wide transport and largest mass contribution to particulate matter in the atmosphere. They are sourced from the arid regions of the world. In this context, this work evaluates the INP potential of fourteen topsoil samples collected from subtropical South American deserts, the major source of mineral aerosols in South America, in the immersion freezing mode. Samples were obtained from three distinct regions located in the South American Arid Diagonal and recognized as potential dust source areas: the Puna-Altiplano Plateau in the north, the central-west of Argentina, and Patagonia in the south. In general, results reveal that samples from the Puna-Altiplano and Patagonia regions, and the central-west of Argentina region exhibit the highest and lowest INP abilities, respectively. The active sites per unit surface area for a given temperature were calculated and compared with previously reported values. The results demonstrate that soil mineral particles from the region of study exhibit ice nucleating abilities comparable to the inorganic fraction of agricultural soils of central Argentina. No direct relationship was identified between INP ability and the major minerals observed in the samples. This study is the first to analyze the ice nucleation properties of soil samples collected along the South American Arid Diagonal and one of the few in South America. Since the analyzed topsoil particles were collected from potential dust source regions, this work contributes to understanding the role of aerosols in initiating atmospheric ice formation, providing valuable data for empirical parameterizations. This could contribute to the improvement in the performance of climate models, as the obtained results suggest that the underestimation of coarse and super-coarse aerosols at altitudes relevant for cloud formation may lead to underestimations in INP concentrations, particularly in regions near to the emission sources.

PYROLYSIS OF TEXTILE WASTE: A SUSTAINABLE APPROACH TO WASTE MANAGEMENT AND RESOURCE RECOVERY

The textile industry is one of the most polluting sectors globally, with increasing amounts of textile waste posing significant environmental and public health challenges. This study investigates the pyrolysis of pure cotton, polyester, and a 55% polyester/45% cotton blend as a sustainable approach to waste management and resource recovery. Pyrolysis was conducted in a tubular reactor at 425 °C, 500 °C, and 575 °C. The resulting char, oil and gas fractions were quantified and characterized. The highest oil yield (over 45%) was obtained from pure cotton, primarily composed of heavy naphtha. In contrast, pure polyester and the cotton-polyester blend produced predominantly gaseous fraction (over 50%) with H2 as the major compound. The char produced, especially from cotton at 575 °C, exhibited significant carbon content (75.6%) and textural properties suitable for use as adsorbents. These findings demonstrate the potential of pyrolysis for energy recovery and promoting a circular economy in textile waste management.

Justification of the operating parameters of the soil mill for the formation of a ridge

Abstract This paper presents the development and justification of operating parameters for a soil milling machine designed to form ridges for the pre-sowing preparation of industrial crops. The study focuses on determining the optimal parameters of the working bodies and operating modes of the cutter, emphasizing the importance of reducing undesirable soil fractions to enhance seed germination. Experimental results demonstrate that the use of organomineral complexes significantly improves soil structure, leading to better moisture retention and reduced vibrations during sowing. The machine’s design incorporates four sections, each equipped with milling drums, ridge formers, and compaction rollers, allowing for efficient soil preparation in a single pass. Key findings indicate that increasing the number of knives on the milling drum enhances soil crumbling efficiency, with optimal configurations yielding significant improvements in grain weight and overall crop quality. The research highlights the effectiveness of the developed machine in achieving high-quality tillage while conserving resources, thereby contributing to more sustainable agricultural practices.

Alleviation of Fe-induced chlorosis of soybean plants grown in calcareous soil by a freeze-dried iron fertilizer containing siderophores produced by Rhizobium radiobacter

The concerns about the unsustainability of traditional synthetic Fe chelates lead to the search for new environmentally friendly alternatives, such as siderophores-based fertilizers. In this work, the focus was on the evaluation of a bio-based Fe-chelate fertilizer obtained from the culture of the siderophore-producer bacterium Rhizobium radiobacter. The suitability of a freeze-dried fertilizer formulated from a R. radiobacter culture labeled with 57Fe to alleviate Fe chlorosis in soybean plants cultivated in calcareous soil was analyzed and the new potential Fe fertilizer was evaluated in comparison to the traditional synthetic chelate o,oEDDHA/57Fe3+. This natural chelate was able to maintain chlorophyll content stable during all the pot trials and presented greater Fe concentration in the remaining soil fractions serving as an Fe pool for a long time whereas o,oEDDHA/57Fe3+ could supply Fe quickly. The new bio-based Fe siderophore fertilizer, derived from R. radiobacter culture, could be a green substitute to conventional synthetic chelates to address Fe chlorosis in calcareous soil conditions.

Effects of crop rotation on plant- and microbial-derived carbon within particulate and mineral fractions in paddy soils

Paddy soil is an important soil organic carbon (SOC) sink, and particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) are distinct components of SOC concerning their formation and function. However, the contributions of plant- (lignin phenols) and microbial- (amino sugars) derived C within the POC and MAOC fractions of SOC under various paddy field rotation systems have not yet been documented. Thus, we conducted an 8-year field experiment encompassing four distinct crop rotation systems: wheat-rice (W-R), rapeseed-rice (R-R), Chinese milk vetch-rice (A-R), and A-R with a 20 % reduction in nitrogen fertilizer (A-R-N). From 2017–2023, crop rotation improved the concentration of amino sugars (AS) in POC and the lignin phenols (VSC) in MAOC. Compared to the beginning of the experiment, the W-R significantly improved the SOC stock at 0–20 cm by 84.1 % by promoting the formation of POC (69.5 %) and MAOC (101.5 %) in 2023. W-R increased the content and proportion of AS in POC, as well as the content of VSC compared with the other treatments. Nevertheless, rice yield does not increase synergistically with SOC. On average, W-R had the lowest rice yield and decreased rice yield by 9.2 %, 2.8 %, and 5.6 % compared to R-R, A-R, and A-R-N, respectively. However, the annual yield of W-R was 9.7 %, 62.6 %, and 57.9 % higher than that of R-R, A-R, and A-R-N, respectively. Our findings highlight that incorporating rapeseed and Chinese milk vetch can increase next-stubble rice yield slightly but is not conducive to carbon sequestration in rice fields, and wheat-rice is a promising cropping system for sustaining SOC sequestration and crop production.

Sorting and Weathering Trends of Soil at Gale Crater, Mars: Implications for Regional Pedological Processes

AbstractDetailed soil characterization at Gale crater based on in situ observations has revealed compositional trends within soils, while the physical and chemical processes underlying the compositional trends remain to be evaluated. Here we use the grain‐morphometrical and geochemical trends across the Wentworth‐classes of 48 in situ soil targets at Gale crater to evaluate underlying pedological processes and potential chemical weathering signatures. The concentration of olivine minerals within the ∼250 to ∼500 μm size range indicates the prevalence of heavy mineral sorting in a granulometric sense in Gale soils that surpasses the possible effect of the cratering‐induced mixing processes. The extent of olivine sorting in soils varies spatially and is influenced by the targets' aeolian setting. The finest portion of Gale soils (<125 μm) is likely a mixture of allochthonous sediment, globally sourced from atmospheric suspension, and autochthonous counterparts from the weathering of local rocks, while the coarser soils (>125 μm) are mostly sourced from local rocks, with possible inputs from both the unaltered parent rock of the Stimson formation and the bedrocks that have undergone diagenetic alteration. If applicable globally, this would reinforce prior inferences that even dust‐mantled regions are geochemically heterogeneous owing to a substantial fraction of soils derived from underlying lithology. The low chemical weathering intensity and coupling of mobile elements in soils suggest localized, low pH and low water‐to‐rock ratio aqueous weathering conditions under predominantly cold and arid climates, which may occur either during post‐pedogenetic alteration in soils or during the acidic alteration of source rocks.

Accumulation of metals and metalloids in soil cover, road dust, and their PM10 fraction in Ulan-Ude: Spatial variation and source apportionment

Coal-fired thermal power plants remain one of the primary sources of electricity generation in the Asian part of Russia. However, coal combustion leads to severe environmental pollution. This study attempts to assess this impact in a large city in Eastern Siberia, Ulan-Ude, the capital of Buryatia, where coal is widely used in thermal power plants and for stove heating. The accumulation of trace metals (MMs) in the upper soil horizons, road dust, and their fine PM10 fraction was evaluated. The coal, ash, soil and road dust samples were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS/AES) to determine concentrations of As, Bi, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Sr, V, W, and Zn. The coal was enriched only in Sr compared to world coals, while the ash was depleted in all these MMs. Concentrations of all MMs were higher than the local natural soil background values, with priority pollutants in Ulan-Ude's soils identified as Cu, Pb, Sb, Cd, Zn, and W. For the first time, the primary sources of MMs were quantitatively assessed using the PMF receptor model. It was established that most MMs (As, Ni, Cr, Sr, V, Co, Bi) originated from mixed sources, including natural sources and emissions from coal combustion. Its contribution accounted for 32.6 % for the bulk soils and 25.4 % for the PM10 fraction. The contribution of exhaust and non-exhaust emissions was estimated as 19.2 % and 22.4 % for bulk soils and the PM10 fraction, respectively. The spatial distribution of the Total Pollution Index (TPI) for soils indicated that the pollution degree was highest in private residential areas (mean TPI = 24), suggesting an influence of coal combustion conditions (including temperature) on contamination levels. The PM10 fraction of soil was most polluted in the railway transport zone (mean TPI = 46). Approximately 8 % of Ulan-Ude's territory displayed maximum, extremely hazardous levels of pollution in soils and their PM10 fraction, posing a risk to human health. Road dust was enriched in Sr, Sb and Pb compared to the continental upper crust values. Bulk road dust exhibited a low level of pollution, while the Total Pollution Index for its PM10 fraction reached an extremely hazardous level (TPI > 128). The highest pollution levels in road dust and its PM10 fraction were observed on main roads. In large industrial cities, pollution from coal combustion occurs alongside other significant sources, including vehicular emissions, contributing to the diversity of total pollutant emissions.

Organosolv-derived lipids from hemicellulose and cellulose, and pre-extracted tannins as additives upon hydrothermal liquefaction (HTL) of spruce bark lignins to bio-oil

The rise in global temperature and accumulation of petroleum-based wastes in the environment forces the scientific focus towards renewable alternatives. In the present work, an under-exploited resource – spruce bark – is investigated as a raw material for production of bio-oil as a liquid energy carrier. To enhance the energy-content of the produced bio-crude, ultimately being produced through hydrothermal liquefaction, the polysaccharides were extracted through organosolv fractionation and converted to lipids by oleaginous microorganisms. The effect originating from tannins was also investigated by performing a pre-extraction before the organosolv fractionation. It was found that performing the organosolv fractionation and upgrading the isolated organosolv lignin to bio-oil greatly reduced the oxygen content of the oil fraction thereby improving its energy content, and introducing upgraded polysaccharides in the form of lipids, as well as pre-extracted tannins, caused clear changes in the product distribution of the final bio-oil and kept a final product with low oxygen content. The other factor largely influencing the product distribution originated from the various heating rates tested by altering operational mode of the HTL process between batch and semi-continuous. Ultimately, performing the organosolv fractionation and individual upgrading of the polysaccharides had a beneficial effect on reducing the final solids content and enhancing the liquid oil yield.

First field application of functionalized nanoparticles-based nanofluids in thermal enhanced oil recovery: From laboratory experiments to cyclic steam stimulation process

The increasing global demand for fossil fuels and the depletion of light crude oil reserves have driven the petroleum industry to focus on exploiting heavy crude oils, which present significant challenges in recovery and processing. To address these challenges, enhanced oil recovery (EOR) technologies are being developed, with a strong emphasis on advances in catalysis and nanomaterials science. This research significantly contributes to developing new technologies for petroleum exploitation by introducing a novel nanofluid designed to facilitate in-situ upgrading of heavy oil, improving its quality for downstream refining and fuel production. The nanofluid, engineered to enhance the productivity of a heavy oil reservoir under cyclic steam stimulation, targets improvements in oil recovery and fuel-quality indicators such as API gravity and viscosity. Laboratory tests demonstrated the nanofluid’s capability to reduce oil viscosity, improve oil mobility, and selectively interact with heavy oil fractions like resins and asphaltenes. Displacement tests simulating steam injection conditions showed an improvement in oil recovery, increasing from 56 % to 76 % after nanofluid application. The treatment also led to a notable increase in API gravity, from 11.6° to 29.2°, and a significant reduction in viscosity, from 39,987 cP to 104 cP, indicating enhanced crude oil quality, critical for refining and fuel production. Field trials in two wells in Colombia demonstrated the nanofluid’s practical effectiveness, with production increases averaging 97 % and incremental yields of 11,966 barrels in well A and 3213 barrels in well B. Post-treatment, the crude oil exhibited sustained improvements in quality, with API gravity increasing from 11.6° to 13.4° and viscosity decreasing from 39,987 cP to 11,734 cP. These results confirm the long-term durability of the nanofluid’s effects and its potential to enhance fuel production from heavy oil reservoirs. Additionally, the field trial indicated a 48 % reduction in operational costs, primarily due to decreased steam generation and lower CO2 emissions, highlighting the environmental and economic benefits of nanofluid technology for petroleum exploitation.

Screening, Isolation and Hydrocarbon Degradation Characteristics of Yeasts from Mangrove Sediments of Kerala

The aim of the present work was to examine the hydrocarbon degradation potential of yeasts isolated from the mangrove sediments. Mangrove sediments around the world were considered to be heavily polluted with oil contaminants and the microbes dwelling in them were believed to be highly active in metabolizing and detoxifying the oil fractions. In the present study, 70 yeast isolates were screened for their lipolytic activity qualitatively and 35 of them which showed comparatively higher lipolysis were tested for their crude oil degradation ability. Screening of hydro-carbon utilizing isolates was performed on Bushnell Haas agar media overlaid with 1% crude oil and the appearance of colonies were considered a positive. Three isolates were selected based on this and were sequenced using ITS gene of the 18S region of the rDNA and identified to be Candida tropicalis. The extent of crude oil degradation was assessed by growing the isolates in basal medium supplemented with heavy crude oil as the carbon source for 21 days. The residual crude oil fractions were then analyzed using GC-MS to quantitatively measure the degradation potential of each isolate. Our results showed that the yeast strains under study could actively metabolize the crude oil including the higher chain fractions which make them efficient hydrocarbon degraders that can be used in the bioremediation processes.

Soil zinc dynamics over time on applied organics, bacterial inoculant and zinc fertilizers in calcareous soil of southern India

Bioavailability of zinc was impacted by soil properties, externally applied sources, time, and various fractions of zinc. An experiment was conducted to investigate the bioavailable and other zinc fractions in calcareous soil and the efficiency of organic and inorganic sources on bioavailability with the presence and absence of zinc solubilizing bacteria (ZSB). The sequential extraction procedure followed at every interval of the incubation period for all forms of zinc was studied. Externally added inorganic sources significantly affected all fractions of zinc compared to untreated soils. Among them, ZnSO4 influences all forms of zinc, mainly Ws+Ex (water soluble+exchangeable) and carbonate-bound zinc, whereas Zn-EDTA maintains a high status of bioavailable zinc throughout the experimental period. On the 60th day of incubation, Zn-EDTA and ZnSO4 applied to soil maintained bioavailable zinc content of 3.71 and 2.94 times higher than that of control. Irrespective of sources, the available zinc of Zn fertilizers applied to soils was reduced with an increase in incubation days. Organic and microbial addition effects solely or combined increase the soil zinc content significantly in both fertilized and unfertilized soils. Among two different organic sources, the zinc solubility performance of farmyard manure was higher than that of vermicompost. In untreated soil, residual and carbonate-bound fractions contribute a major portion towards total zinc based on quantity. The bioavailable fraction mainly the Ws+Ex and organically bound fractions were markedly influenced in all treatments.

AI-Based Evaluation of Homogeneous Flow Volume Fractions Independent of Scale Using Capacitance and Photon Sensors

Metering fluids is critical in various industries, and researchers have extensively explored factors affecting measurement accuracy. As a result, numerous sensors and methods are developed to precisely measure volume fractions in multi-phase fluids. A significant challenge in multi-phase fluid pipelines is the formation of scale within the pipes. This issue is particularly problematic in the petroleum industry, leading to narrowed internal diameters, corrosion, increased energy consumption, reduced equipment lifespan, and, most crucially, compromised flow measurement accuracy. This paper proposes a non-destructive metering system incorporating an artificial neural network with capacitive and photon attenuation sensors to address this challenge. The system simulates scale thicknesses from 0 mm to 10 mm using COMSOL multiphysics software and calculates counted rays through Beer Lambert equations. The simulation considers a 10% interval of volume variation in each phase, generating 726 data points. The proposed network, with two inputs—measured capacity and counted rays-and three outputs—volume fractions of gas, water, and oil—achieves mean absolute errors of 0.318, 1.531, and 1.614, respectively. These results demonstrate the system’s ability to accurately gauge volume proportions of a three-phase gas-water-oil fluid, regardless of pipeline scale thickness.

Plants and microorganisms both contribute to soil organic matter formation through mineral interactions: Evidence from a subtropical forest succession

Understanding the formation and stabilization of soil organic carbon (SOC) is essential for predicting SOC dynamics. Traditionally, it was believed that SOC accumulates primarily through the selective retention of recalcitrant plant lignin components. However, an emerging hypothesis suggests that microbial necromass adsorbed onto mineral-associated soil fractions play a more significant role in promoting SOC formation. In this study, we tested the above hypothesis by investigating SOC content, particulate fraction (LF + POC) vs. mineral-associated fraction (MAOC), along with microbial necromass (amino sugars as biomarker) and plant lignin component (lignin phenols as biomarker) in the topsoil (0–20 cm) and subsoil (20–40 cm) across three successional stages: early coniferous forest, middle mixed forest and climax broadleaved forest in southern China. Results showed that SOC content increased with forest succession, accompanied by increasing contributions of MAOC in both soil layers. Interestingly, the contribution of microbial necromass to SOC increased throughout the succession only in the subsoil, whereas in the topsoil, it increased from the early to the middle stage, then slightly decreased at the climax stage. Additionally, the contributions of lignin phenols or LF + POC to SOC decreased in both soil layers with forest succession. A partial least squares path model further revealed that MAOC played a dominate role in governing SOC accumulation, driven by active mineral content combined with plant-derived dissolved organic matter in the topsoil and microbial necromass in the subsoil. Collectively, our findings suggest that plants and microorganisms contribute to SOC formation through interactions with minerals, unveiling an intricate interactive mechanism of plant–microbe-mineral continuum in SOC stabilization.

Cu Concentration in Vegetable-Cultivated Soil: Comparison Between Open Fields and Protected Environments in Brazil

High copper (Cu) concentration in soils used for vegetable production is an agricultural, social and environmental issue. The excess of Cu in soil can cause toxicity in plants, reducing growth and yields. Moreover, Cu can also be absorbed and accumulated in edible organs, increasing risks for human health. This study aimed to compare Cu fractions in soils: (1) non-cultivated, natural soil (NC), (2) soils cultivated with open field crops (FCs) and (3) soils cultivated in controlled environments (CEs). The survey was carried out on 25 sites in Rio Grande do Sul (Southern Brazil), with each site containing the three types of soils described above. From these sites, the four with the highest soil Cu concentrations were selected to compare soluble (Cu-CaCl2), available (Cu-EDTA) and total (Cu-EPA) Cu. Both total and available soil Cu concentration in soil solution, in CE and FC areas were higher than in NC. At sites 23R1 (Oxisol) and 11R1 (Molisol) the soluble and available Cu content was higher in the FC environment than in CEs, and the same was observed for the total Cu content at sites 23R1 (Oxisol) and 9R1 (Molisol). Some FC soils showed total Cu concentrations higher than the limits established by Brazilian environmental legislation, being, as a consequence, potentially contaminated. Soil monitoring and cropping practices must be adopted to reduce the Cu content in soils of vegetable crops in this region.

Data Reconciliation for Assessing Compliance of Physicochemical Properties of Petroleum Products in Commercial Transactions

The physicochemical properties of petroleum products in commercial transactions are crucial for quality control in the oil and gas industry. However, different laboratories often produce slightly different measurement results. These variations can be significant when approving or rejecting properties based on regulatory agency and environmental body specifications. A simple arithmetic average is typically used to determine the most probable value in disputes. This study proposed using a Data Reconciliation approach to address the disparity between the projected model and empirical data. An objective function was employed to optimize and evaluate parameters using maximum likelihood estimation, considering the experimental uncertainty values. This study found that the flash point of jet fuel, as determined by the Tag Closed Cup Tester, was within the specified range (maximum of 40 °C). The application of this tool resolved a dispute between a supplier and a customer, as the reconciled value with minimized uncertainty was determined to be 37.5 ± 2.0 °C. Additionally, the study utilized experimental results from 12 accredited laboratories to determine a single reconciled value for the final boiling point of gasoline. Despite the varying experimental uncertainties ranging from 6.0 °C to 13 °C, the reconciled uncertainty was minimized to 2.6 °C. The last case study identified that ASTM D4294 was incompatible with other test methods for evaluating the mass fraction in diesel oil. In this manner, Data Reconciliation enhanced the accuracy and effectively reduced measurement uncertainties, rendering it a potent tool for resolving legal disputes when evaluating the compliance of the physicochemical properties of petroleum products in commercial transactions.

Vernonanthura tweediana (Baker) H. Rob. (Asteraceae), an Ordinary Bush or an Anti-Inflammatory and Immunomodulator Aromatic Species?

Background: Oral traditional knowledge disseminates the use of young leaves of Vernonanthura tweediana (Asteraceae) as poultice in feverish cases among family farmers in Santa Catarina, Brazil, but there is a lack of phytochemistry and pharmacological studies on this species, especially those related to volatile organic compounds. Methods: In the present study, the dry leaves of V. tweediana were subjected to hydrodistillation for the extraction of essential oil. Sample characterization was conducted using GC-FID and GC-MS. To evaluate anti-inflammatory and immunomodulatory activities, the air pouch method was used, and with the exudate obtained, total and differential leukocyte counts were performed, as well as the quantification of total proteins, interleukin (IL) 1β, IL-6, and tumor necrosis factor (TNF). Results: The essential oil yield extraction was 0.13%, and sesquiterpenes were the main constituents: α-copaene (5.1%), β-caryophyllene (27.77%), α-caryophyllene (15.1%), germacrene D (14.0%), and bicyclogermacrene (13.3%). A sample was subjected to biological tests, with a reduction in leukocyte migration to the inflammatory focus. The immunomodulatory activity was also pronounced, as the oil modulated all cytokine secretions measured when compared to the control. The high concentration of caryophyllenes might explain these findings. Conclusions: Future studies will consider the fractionation of the essential oil to establish the degree of synergism between the constituents.

Spatial Variability in the Speciation of Lead (Pb) and Other Metals Across Urban Lawns Is Linked to Post-Deposition Weathering Reactions

The historical use of lead (Pb) poses ongoing health risks via exposure to contaminated urban soils. However, there is limited information about heterogeneity in Pb speciation and distribution at the house lot scale. This study determined highly spatially resolved Pb and other metal speciation along horizontal transects and vertical soil cores from three homes in the Akron, Ohio (USA) municipal. Solid phase characterization was coupled with a sequential extraction protocol to determine operationally defined speciation (exchangeable (MEX), reducible (MRED), oxidizable (MOX), and residual (MRES)). Lead and Zn were strongly correlated across all fractions (R2 = 0.92). Total extractable Pb and Zn were found in low weight percent concentrations nearest to the homes, and speciation was dominated by MEX and MRED. High Pb in the MEX fraction was correlated with the presence of Pb-bearing paint chips in the soil. Lead in the MEX fraction in soils near the homes decreased with increasing time due to exterior renovations coupled with increases in Pb and Zn in the MRED fraction. These results suggest that homes are the dominant source of Pb and Zn due to the weathering of exterior surfaces and highlight the acute risk of exposure to more labile Pb immediately following exterior renovations and damage to home exteriors in areas of older housing stock.

Granulometric and Geochemical Distribution of Arsenic in a Mining Environmental Liability in a Semi-arid Area.

This study focuses on the "El Lavadero" tailings deposit, a mining environmental liability (MEL) located near the town of San Felipe de Jesús, Sonora, in northwest Mexico. The objective was to determine the total arsenic (As) content, its granulometric and geochemical distribution, as well as its mobilization capacity and bioavailability. The results from oxidized and unoxidized tailings showed low potential of hydrogen (pH) values (2.4-5.7) and high concentrations of total arsenic (8235-36,004mgkg-1), predominantly in the finer granulometric fractions (< 0.05mm). Arsenic also prevails in the finest fraction of agricultural soil (> 2mm). These fine particles could present adverse environmental effects due to their potential to be transported by leaching and water suspension. In contrast, arsenic in the effluent sediments is primarily found in the coarser fraction (> 2mm). A significant proportion of arsenic in the tailings (5-40%) was found in the non-residual geochemical fractions (I + II + III) (1106-7675mgkg-1), indicating potential for mobilization and bioavailability. Depending on environmental conditions (redox potential and pH), arsenic can redissolve and exhibit high mobility in abiotic media, which may ultimately impact the environment and human health. Therefore, it is crucial to rehabilitate the "El Lavadero" MEL to prevent further environmental damage. This study provides useful information to understand some phenomena in other global mining environmental liabilities, such as mobilization and bioavailability of arsenic and its possible impact on the surrounding environment and biota, contributing to the worldwide research of ecosystems polluted by mining activity, especially in arid and semi-arid climates.

Effects of exogenous nitrogen addition on soil organic nitrogen fractions in different fertility soils: Result from a 15N cross-labeling experiment

Exogenous nitrogen (N) addition serves as a pivotal nutrient management strategy, significantly enhancing agricultural production by regulating soil N availability and retention. However, the dynamics of soil organic nitrogen (SON) fractions in response to various forms of exogenous N addition across differing soil fertility levels remain inadequately understood. This study utilized data from a 25-year fertilization experiment and a 15N cross-labeling experiment in Northeast China to assess and quantify the effects of mineral N fertilizers and organic materials (manure and straw) on SON fractions in NPK (mineral fertilizer addition) and NPKM (NPK combined with composted pig manure) treatments. Our findings indicate that long-term incorporation of manure substantially elevates soil fertility compared to the exclusive use of mineral fertilizers. Notably, exogenous N primarily boosts soil N availability by enhancing acid-soluble organic N fractions, particularly ammonium nitrogen (AN) and amino acid nitrogen (AAN). Organic materials, particularly straw, significantly enhanced the retention of mineral fertilizer N in both NPK and NPKM treatments (9.54 % vs 10.70 %). Moreover, over 70 % of the N from straw or manure remained in the soil as stable SON fractions. While straw rapidly improves low-fertility soils, manure contributes to enhanced soil N reserves and increased crop yields. Therefore, incorporating organic matter may bolster soil N sequestration in Northeast China, which is contingent upon soil fertility and tailored fertilizer management strategies. This research elucidates the distribution and conversion of exogenous N within SON pools, facilitating optimized N management, sustaining yields, reducing farmland N pollution, and promoting agricultural sustainability.