Organic Mineral Research Articles

Uranium enrichment driven by paleomarine condition and event deposition: Insights from the lower Cambrian Niutitang Formation organic-rich shales in northeastern Guizhou, South China

Organic-rich shale related uranium (U) mineralization has attracted widespread attention as a strategic and clean alternative to fossil energy and a paleoceanic redox proxy. A comprehensive study of mineralogy, organic geochemistry and elemental geochemistry of the lower Cambrian Niutitang Formation organic-rich shales in northeastern Guizhou, South China was conducted to address this issue. SEM-EDS results showed that the U occurrence state in the Niutitang Formation shales is dominated by nanoscale U minerals, mainly including coffinite, brannerite, U-bearing apatite and U-bearing xenotime. Various states of U are closely associated with organic matter, apatite, pyrite and clay minerals. Based on geochemical indexes, paleomarine condition and event deposition jointly drove the U enrichment in the Niutitang shales, in which hydrothermal activities and/or volcanic eruptions increased U fluxes in seawater and euxinic environment with high primary productivity provided a favorable condition for U reduction. The adsorption, complexation and reduction of UO22+ by organic matter and the formation of uranyl phosphate complexes by the combination of phosphate and UO22+ accelerated U immobilization and enrichment from bottom water to sediments. The microbial activities (e.g., BSR) in this process created favorable euxinic conditions and released inorganic-phase P to provide available ligands for UO22+. The U enrichment models of the lower Cambrian Niutitang shales in northeastern Guizhou were established. This paper provides a new insight into the U enrichment mechanism in organic-rich shales, and may also have implications for the applicability of U as redox proxy and the exploration of organic-rich shale related U deposits.

Biotic regulation of phoD-encoding gene bacteria on organic phosphorus mineralization in lacustrine sediments with distinct trophic levels

Organic phosphorus (Po) mineralization hydrolyzed by alkaline phosphatase (APase) can replenish bioavailable P load in the sediment water ecosystem of lakes. However, the understanding about the interaction between P load and bacteria community encoding APase generation in the sediment are still limited. Different P pools in the sediments from Taihu Lake, China were measured using sequential extraction procedure. The APAase activity (APA) were obtained accompanying with enzymatic dynamical parameters Vmax and Km. The abundances and diversity of gene phoD-harboring bacterial communities were assessed using high throughput sequencing. The analysis results showed the decrease of potentially bioavailable P fractions including MgCl2-P and Fe-P along sampling gradient southwards together with active P concentrations in the water. Conversely, increasing APA and absolute abundance of phoD gene were found with the decreasing of P loads southwards. Positive correlation (p < 0.05) between absolute abundance and APA indicated that phoD-encoding bacteria manipulated the APA and Po mineralization. Negative correlation (p < 0.01) suggested that the APA was restrained by high P load and was promoted under low P condition. However, higher Vmax and Km values suggested that high mineralization potential of Po maintained the high concentrations of potentially bioavailable P even the APA was restricted. The abundance increase of predominant genus Cobetia (from 15.51 to 24.34 %) mirrored by the reduced Calothrix abundance (from 24.65 to 1036 %) was speculated to be responsible for the APA promotion under low P condition. Higher diversity indices in the high P scenario suggested that high P load stimulated the ecological diversity of gene phoD-encoding bacteria community. Generally, rare taxa such as Burkholderia having high connected degrees in bacterial communities together with abundant genera synergistically manipulated the phoD gene abundance and APase generation. Interaction between P fractions and bacteria encoding phoD gene determined the eutrophication status in the lacustrine ecosystem.

Preferential extraction of degraded organic matter and mineral protection of aromatic structures based on molecular marker analysis

The humic fractions were sequentially extracted from soils to study the heterogenous properties of soil organic matter (SOM). However, the bulk characteristics of these samples, such as elemental compositions and functional groups, could not fully reveal their diverse compositions. We sequentially extracted humic acids (HAs) from a sediment, and analyzed its molecular markers (benzene polycarboxylic acids (BPCAs), lignin-derived phenols, free lipids and bound lipids) to illustrate the diverse compositions of SOM. Our results suggested that the investigated HAs were derived from terrestrial C3 plants as reflected by the range of their δ13C values (−27.08 ‰ in HA1 to −27.85 ‰ in HA6), more specifically, non-woody tissue of angiosperm and belowground part as suggested by lignin and lipid markers. With the increasing times of extraction, the relative abundances of lignin-derived phenols, free lipids, and bound lipids increased, while those of the condensed aromatics (as indicated by BPCAs) decreased. We also observed that with the increasing times of extraction, the carbon preference index (CPI) increased, the ratios of acids to aldehydes of vanilly units (Ad/Al)v and δ13C of HAs decreased, suggesting that the extensively degraded organic compositions were selectively extracted because of their favored dissolution. Our results emphasize that the complete extraction of organic compositions is essential to ensure reliable analysis on SOM properties and turnover. The distribution of individual BPCAs suggested that the highly condensed aromatics were preferentially extracted. These might be attributed to the less condensed aromatics were more strongly associated with mineral particles, which is important for the protection of aromatic carbons in the environment.

Combined effect of temperature and illumination on treatment of etching terminal wastewater in single-chamber microbial electrolysis cells

Temperatures and illumination/darkness conditions influenced etching terminal wastewater (ETW) treatment using Serratia marcescens-inoculated single-chamber microbial electrolysis cells (MECs), achieving recalcitrant organics mineralization (6.0 − 12.2 mg/L/h) and complete heavy metals removal at 4 − 60 ℃ during 24 h operation. A favorable 6 h operation for heavy metals removal and the preferable 24 h for recalcitrant organics mineralization, demonstrated nonsynchronous removal/mineralization of these different components in the ETW. Temperature and illumination combinedly regulated S. marcescens release of more cathodic than anodic extracellular polymer substances (EPS) with a compositional diversity and the more functional cathodic triplet 3EPS* than active radical HO•, converse to the HO• over 3EPS* in darkness, for efficient recalcitrant organics mineralization. These results illustrated the combined influential temperature and illumination via regulating S. marcescens release of different EPS for ETW treatment, providing a new regulating strategy towards efficient treatment of actual industrial wastewaters in single-chamber MECs.

Effects of Long-Term Fertilizer Managements on Soil Organic Carbon Mineralization Under the Double-Cropping Rice System in Southern China

ABSTRACT Soil organic carbon (SOC) plays an important role in maintaining or increasing soil fertility and quality in paddy field, but there is limited information about how SOC mineralization responds to different fertilizer managements under the double-cropping rice system in southern China. Therefore, this study was designed to explore changes in SOC content, soil enzyme activities, SOC mineralization at 0–10 cm and 10–20 cm layers, and its relationship with long-term fertilizer managements in a double-cropping rice system of southern China. The experiment included four fertilizer treatments: chemical fertilizer alone (CF), rice straw and chemical fertilizer (RS+F), 30% organic manure and 70% chemical fertilizer (OM+F), and without fertilizer input as a control (Con). These results showed that SOC and labile organic carbon contents at 0–10 cm and 10–20 cm layers in paddy field with RS+F and OM+F treatments were increased, compared to CF and Con treatments. Compared with Con treatment, SOC mineralization rate and accumulation with CF, RS+F, and OM+F treatments were increased. SOC accumulation and potential mineralization at 0–10 cm and 10–20 cm layers with RS+F and OM+F treatments were increased, compared with CF and Con treatments. SOC mineralization rate and accumulation at 0–10 cm layer with CF, RS+F, OM+F, and Con treatments were higher than that of 10–20 cm layer. These results indicated that soil invertase, cellulose and urease activities in paddy field with RS+F and OM+F treatments were significantly higher than that of CF and Con treatments. There was a significant positive relationship between SOC accumulation and SOC content, soil invertase, cellulose, urease activities but were significant negative correlated with soil pH, bulk density. As a result, these were beneficial practices for improving SOC content and SOC mineralization in a double-cropping rice field of southern China by combined application of rice residue or organic matter with chemical fertilizer managements.

Particle and bulk media characteristics of food waste compost-based biomedia by dynamic high-temperature aerobic composting process

The dynamic high-temperature aerobic composting (DHAC) process, as a decentralized system, is considered a sustainable strategy for renewable resource-based raw materials. The food waste compost-based biomedia (BMFWCs) produced within five days of the DHAC process exhibited the physical properties of peaty topsoil with acceptable maturity under the meso-thermophilic phase. To understand the particle and bulk media characteristics of the BMFWCs, organic matter (OM) fraction–density–porosity parameters, particle size distribution, and uniformity coefficient were considered. Operating the DHAC process produced end products characteristics of relatively high total porosity (φb,T) and low dry bulk density (ρb) compared to the conservative mixture theory due to binary mixing and shape effects. A significant change in total porosity was estimated as an increase in non-spherical fibrous particles within the OM fraction of 0.4. Appropriate organic–mineral additives led to the effective arrangement of the variable porosity structure and improvement of aggregate stability (fom,spent coffee grounds≥0.2, fm,oyster shell powder≤0.4). The Forced aeration supply contributed to the expansion of the open space and macropore structures that serve as gas passages in the BMFWCs, while the introduction of microbes (Bacillus subtilis) promoted the biodegradation of medium and small macroaggregates (0.25–2 mm). The BMFWCs produced by the DHAC process was expected to have application potential in sustainable nature-based solution technology, due to appropriate particle properties, uniformity, and maturity.

Quantifying the negative effects of dissolved organic carbon of maize straw-derived biochar on its carbon sequestration potential in a paddy soil

Biochar of low-medium temperature may contain abundant dissolved organic carbon (BDOC), affecting its priming effect and carbon sequestration potential in soils. However, the direct and quantitative evidence for such impacts remains lacking. This study conducted incubation experiments on maize straw-derived 300/450 °C biochar, BDOC-extracted biochar residues and BDOC, and applied δ13C analysis to quantify biochar's mineralization and their priming effects on native soil organic carbon in a paddy soil. BDOC contained abundant lipid-, protein-, carbohydrate-like species, serving as nutrients for the metabolism of microorganisms, and thus enhanced native soil organic carbon's mineralization by 15–20%. After BDOC extraction, 300 °C biochar-trigged priming effect shifted from a positive (3.7 mg CO2–C kg−1 soil) to a negative state (−14.4 mg CO2–C kg−1 soil), and 450 °C biochar-induced negative priming effect increased by 31%; biochar's mineralization also decreased by 41–65%. Overall, after BDOC extraction, the net carbon balance in biochar-amended soils reduced by 7–8%. Furthermore, BDOC shifted the dominant priming mechanisms of biochar mainly by enhancing soil macro-aggregates while reducing sorptive protection for native soil organic carbon. Its extraction reduced the amount of soil macro-aggregates by 16–25% but enhanced the sorption affinity of native soil organic carbon by biochar by 68–122%. Additionally, after BDOC extraction, the microbial communities in biochar-amended soils contained more fungi and G+-bacteria. These findings proved that BDOC extraction appears a feasible strategy to enhance the short-period carbon sequestration potential of biochar.

Microplastics increase the microbial functional potential of greenhouse gas emissions and water pollution in a freshwater lake: A metagenomic study

Aquatic ecosystems are being increasingly polluted by microplastics (MPs), which calls for an understanding of how MPs affect microbially driven biogenic element cycling in water environments. A 28-day incubation experiment was conducted using freshwater lake water added with three polymer types of MPs (i.e., polyethylene, polypropylene, polystyrene) separately or in combination at a concentration of 1 items/L. The effects of various MPs on microbial communities and functional genes related to carbon, nitrogen, phosphorus, and sulfur cycling were analyzed using metagenomics. Results showed that Sphingomonas and Novosphingobium, which were indicator taxa (genus level) in the polyethylene treatment group, made the largest functional contribution to biogenic element cycling. Following the addition of MPs, the relative abundances of genes related to methane oxidation (e.g., hdrD, frhB, accAB) and denitrification (napABC, nirK, norB) increased. These changes were accompanied by increased relative abundances of genes involved in organic phosphorus mineralization (e.g., phoAD) and sulfate reduction (cysHIJ), as well as decreased relative abundances of genes involved in phosphate transport (phnCDE) and the SOX system. Findings of this study underscore that MPs, especially polyethylene, increase the potential of greenhouse gas emissions (CO2, N2O) and water pollution (PO43−, H2S) in freshwater lakes at the functional gene level.

Macrogenomics reveal the effects of inter-cropping perilla on kiwifruit: impact on inter-root soil microbiota and gene expression of carbon, nitrogen, and phosphorus cycles in kiwifruit.

Intercropping systems can improve soil fertility and health, however, soil microbial communities and functional genes related to carbon, nitrogen and phosphorus cycling under the intercropping system of mesquite and perilla have not been studied. Therefore, in the present study, different planting densities and varieties of Perilla frutescens (L.) Britt and kiwifruit were used for intercropping, and changes in soil microbial communities and carbon, nitrogen, and phosphorus cycling genes in kiwifruit inter-roots under inter-cropping conditions were investigated by macro-genome sequencing technology. The results showed that intercropping with Perill caused a decrease in most soil nutrients, soil enzyme activities, and had a significant impact on the microbial (bacteria and fungi) diversity. Inter-cropping increased the relative abundance of the dominant bacterial phylum "Proteobacteria" and "Actinobacteria" by 47 and 57%, respectively, but decreased the relative abundance of the dominant fungal phylum "Chordata" and "Streptophyta" by 11 and 20%, respectively, in the inter-root soil of kiwifruit, and had a significant impact on the microbial (bacteria and fungi) diversity. In addition, inter-cropping could greatly increase the inter-root soil carbon sequestration (PccA, korA/B/C/D, fhs, and rbcl/s), carbon degradation (abfD), organic nitrogen mineralization (GDH2), denitrification (napA/B, nirB, norB), organic phosphorus mineralization (phop, phn), and inorganic phosphorus solubilization (gcd, ppk) gene abundance. The gene co-occurrence network indicated that soil korB, nirB, and gnd key functional genes for carbon, nitrogen, and phosphorus cycling in kiwifruit inter-root soils and their expression was up-regulated in the inter-cropping group. Structural equation (SEM) further showed that soil total nitrogen, organic matter, total carbon and acid phosphatase had significant effects on microbial diversity (p < 0.05) and soil carbon cycling gene korB and phosphorus cycling gene purH (p < 0.001), while korB and purH had positive effects on kiwifruit quality. In conclusion, intercropping perilla in kiwifruit orchards changed the structure of bacterial and fungal communities in the inter-root soil of kiwifruit, but I believe that intercropping perilla stimulates carbon degradation, leading to carbon emission and serious loss of soil nutrients, and that prolonged intercropping may adversely affect the quality of kiwifruit, and thus its limitations should be noted in future studies.

Accumulation and translocation of lead in vegetables through intensive use of organic manure and mineral fertilizers with wastewater

In many countries with wastewater irrigation and intensive use of fertilizers (minerals and organics), heavy metal deposition by crops is regarded as a major environmental concern. A study was conducted to determine the impact of mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse on soil’s trace Pb content and edible parts of vegetables. It also evaluated the risk of lead (Pb) contamination in water, soil, and food crops. Six vegetables (Daucus carota, Brassica oleracea, Pisum sativum, Solanum tuberosum, Raphanus sativus, and Spinacia oleracea) were grown in the field under twelve treatments with different nutrient and water inputs. The lead concentrations in soil, vegetables for all treatments and water samples ranged from 1.038–10.478, 0.09346–9.0639 mg/kg and 0.036–0.26448 mg/L, The concentration of lead in soil treated with wastewater in treatment (T6) and vegetable samples was significantly higher, exceeding the WHO’s permitted limit. Mineral and organic fertilizers combined with wastewater treatment reduced lead (Pb) concentrations in vegetables compared to wastewater application without organic fertilizers. Health risk indexes for all treatments except wastewater treatment (T6) were less than one. Pb concentrations in mineral fertilizers, cow manure, poultry manure, leaf litter, and sugarcane bagasse treated were determined to pose no possible risk to consumers.

Enhancing sulfur absorption in soybean rhizosphere through arbuscular mycorrhizal fungi inoculation: Implications for soil health and crop growth

Soybean, a sulfur-loving cash crop, suffers from declining soil sulfur with continuous cropping, hindering its growth and development. Arbuscular mycorrhizal fungi (AMF) form beneficial partnerships with plant roots, aiding in nutrient uptake and promoting plant growth. Recent research has increasingly focused upon AMF's potential to enhance sulfur absorption through increased rhizosphere microbial activity. This study investigated the impact of AMF inoculation on soil organic sulfur mineralization, microbial community composition, and sulfur cycle function genes in the continuous cropping soybean rhizosphere. 16 S rRNA sequencing and high-throughput qPCR revealed changes in microbial community composition and the expression of sulfur cycle genes. ICP-MS measured total soil sulfur, and the BaSO4 turbidimetric method determined available sulfur. Following inoculation of continuous cropping soybean soil with AMF, it was observed that OTU1851, OTU1897, OTU2148, OTU3303, and OTU3738, five specific rhizospheric soil sulfur cycling microbial communities, were enriched. And AMF inoculation enhanced sulfur cycle function, the abundance of aspA, soxY and yedZ increased by 143.23 %, 236.04 % and 436.64 %. This led to increased soil arylsulfatase (S-ASF) activity (from 39.17 to 49.82 μg/(mL·h)), available sulfur content (from 12.88 to 17.55 mg/kg), and ultimately, improved soybean sulfur absorption and growth. Therefore, this study holds significant implications for improving available sulfur content and utilization in sulfur-deficient soils. Furthermore, it provides a theoretical basis for using AMF as a biofertilizer to remediate sulfur -deficiency, offering a sustainable and environmentally friendly solution.

Critical factors in soil organic carbon mineralization induced by drying, wetting and wet-dry cycles in a typical watershed of Loess Plateau

As global climate change progresses, soil will experience prolonged periods of both drought and heavy rainfall, leading to a more frequent drought-re-wetting process that may impact the ecosystem's carbon (C) cycle. However, understanding the extent to which different water conditions and wet-dry cycles alter the process of soil organic carbon (SOC) mineralization remains limited. Therefore, our study focused on the dammed land unique to the Loess Plateau, silted by check dams constructed for erosion control. We implemented three water gradients-drought (30% WHC), water stress (100% WHC), and wet-dry cycling (30–100%)-indoors to observe the SOC mineralization process five times. We identified a transient excitation effect of the wet-dry cycles on SOC mineralization. Soil mineralization decreased gradually with the alternation of wet-dry cycles. The wet-dry cycles not only significantly impacted the contents of SOC and TN but also stimulated the activities of enzymes related to C and N cycles. As the cycle frequency increased, the utilization of C sources by soil microorganisms gradually decreased, and the dominance of carbohydrates, amines, and acids evolved into a single acid, esters, or alcohols. Phosphatase and Chloroflexi were the main factors influencing SOC mineralization under drought stress, while TN and Ascomycota were the primary factors under water stress. SOC and Gemmatimonadetes were the main limiting factors for SOC mineralization under the wet-dry cycles. Additionally, we quantified the direct and interactive contributions of each factor to SOC mineralization. The direct contributions of drought stress, water stress, and the wet-dry cycles to SOC mineralization were 0.961, 0.736, and 0.942, respectively. This study contributes to a more comprehensive understanding of the mechanisms underlying SOC mineralization in the Loess Plateau under changing conditions.

Invasive Spartina alterniflora alters sediment organic carbon mineralization dynamics in a coastal wetland of Southeastern China

Invasive Spartina alterniflora has significant impacts on sediment carbon pool and turnover in the tidal wetlands of estuaries and coasts. Yet, how this exotic S. alterniflora affects sediment organic carbon mineralization dynamics remains poorly understood. In this study, sediment geochemical properties, organic carbon fractions, and mineralization dynamics were examined in a native Cyperus malaccensis habitat and three invasive S. alterniflora habitats (6-, 10-, and 14-year-old) in summer and winter. We found that invasive S. alterniflora generally increased sediment total organic carbon and their labile fraction contents. The organic carbon mineralization rates and cumulative carbon mineralization amounts were significantly influenced by invasive S. alterniflora, and their values increased with this exotic plant invasion chronosequences. The mineralization rates and cumulative mineralization amounts were also characterized by higher values in surface sediment (0 – 10 cm depth) compared to subsurface sediment (10 – 20 cm depth) and by seasonal variations with higher values in summer than in winter. The sediment organic carbon labile fractions, rather than total organic carbon, were the most important factor affecting carbon mineralization dynamics. The cumulative carbon mineralization amounts exhibited an excellent fit to the first-order kinetic equation (R2 ≥ 0.93). The changes in modeled kinetic parameters (potential carbon mineralization amounts (C0) and carbon mineralization rate constant (k)) among these four habitats were similar to carbon mineralization rates, implying invasive S. alterniflora promoted the availabilities of organic compounds for microbial respiration metabolism. Overall, our findings highlighted the importance of S. alterniflora invasion in accelerating organic carbon decomposition and carbon dioxide release potential, although it also increases carbon accumulation.

Maize straw increases while its biochar decreases native organic carbon mineralization in a subtropical forest soil

Organic soil amendments have been widely adopted to enhance soil organic carbon (SOC) stocks in agroforestry ecosystems. However, the contrasting impacts of pyrogenic and fresh organic matter on native SOC mineralization and the underlying mechanisms mediating those processes remain poorly understood. Here, an 80-day experiment was conducted to compare the effects of maize straw and its derived biochar on native SOC mineralization within a Moso bamboo (Phyllostachys edulis) forest soil. The quantity and quality of SOC, the expression of microbial functional genes concerning soil C cycling, and the activity of associated enzymes were determined. Maize straw enhanced while its biochar decreased the emissions of native SOC-derived CO2. The addition of maize straw (cf. control) enhanced the O-alkyl C proportion, activities of β-glucosidase (BG), cellobiohydrolase (CBH) and dehydrogenase (DH), and abundances of GH48 and cbhI genes, while lowered aromatic C proportion, RubisCO enzyme activity, and cbbL abundance; the application of biochar induced the opposite effects. In all treatments, the cumulative native SOC-derived CO2 efflux increased with enhanced O-alkyl C proportion, activities of BG, CBH, and DH, and abundances of GH48 and cbhI genes, and with decreases in aromatic C, RubisCO enzyme activity and cbbL gene abundance. The enhanced emissions of native SOC-derived CO2 by the maize straw were associated with a higher O-alkyl C proportion, activities of BG and CBH, and abundance of GH48 and cbhI genes, as well as a lower aromatic C proportion and cbbL gene abundance, while biochar induced the opposite effects. We concluded that maize straw induced positive priming, while its biochar induced negative priming within a subtropical forest soil, due to the contrasting microbial responses resulted from changes in SOC speciation and compositions. Our findings highlight that biochar application is an effective approach for enhancing soil C stocks in subtropical forests.

Pollution characteristics, source apportionment, and health risk assessment of PM10 and PM2.5 in rooftop and kerbside environment of Lanzhou, NW China.

To investigate air pollution in the kerbside environment and its associated human health risks, a study was conducted in Lanzhou during December 2018, as well as in April, June, and September 2019. The research aimed to characterize the composition of PM10 and PM2.5, including elements, ions, and carbonaceous components, at both rooftop and kerbside locations. Additionally, source apportionment and health risk assessment were conducted. The results showed that the average mass concentrations of PM10 on the rooftop were 176.01 ± 83.23μg/m3, and for PM2.5, it was 94.07 ± 64.89μg/m3. The PM10 and PM2.5 levels at the kerbside are 2.21 times and 1.79 times, respectively, greater than those on the rooftop. Moreover, the concentrations of elements, ions, and carbonaceous components in kerbside PM were higher than those at the rooftop location. Chemical mass closure analysis identified various sources, including organic matter, mineral dust, secondary ions, other ions, elements, and other components. In comparison to rooftop particulate matter (PM), mineral dust makes a more substantial contribution to kerbside PM. Secondary ions show an opposite trend, making a greater contribution to rooftop PM. The contribution of organic components within PM of the same particle size remains relatively consistent. The outcome of the health risk assessment indicates that Co, Cd, and As in PM within the kerbside and rooftop environments do not pose a notable carcinogenic risk. However, Al and Mn do present specific non-carcinogenic risks, particularly in the kerbside environment. Furthermore, children experience elevated non-carcinogenic risk compared to adults. These findings can serve as a scientific foundation for formulating policies within the local health department.

Soil Organic Nitrogen Mineralization and N2O Production Driven by Changes in Coastal Wetlands

AbstractPlant invasion and land reclamation have drastically transformed the landscape of coastal wetlands globally, but their resulting effects on soil organic nitrogen (SON) mineralization and nitrous oxide (N2O) production remain unclear. In this study, we examined 21 coastal wetlands across southern China that have undergone habitat transformation from native mudflats (MFs) to Spartina alterniflora marshes (SAs), and subsequently to earthen aquaculture ponds (APs). We determined the SON net mineralization rate and the presence of pertinent enzyme‐encoding genes, namely chiA, pepA, and pepN. The SON net mineralization rate increased by 46.7% following the conversion of MFs to SAs but decreased by 33.1% in response to the transformation of SAs to APs. Nevertheless, there was no significant difference in the estimated mineralization efficiency of soil microbes among the habitat types. The results of structural equation modeling showed that N‐mineralization gene abundance played a major role in regulating SON mineralization. Although less than 20% of the SON was estimated to be labile/semi‐labile, SON mineralization was important in sustaining soil N2O production, with 5.8% of the mineralized N being fed into N2O production. Overall, our findings showed that the presence of S. alterniflora increased both SON content and mineralization rate, which would in turn promote further proliferation of this exotic plant along the coast. The conversion of S. alterniflora marshes to APs partially mitigated the positive effects of exotic plant invasion on SON turnover.

Screening of plant growth-promoting rhizobacteria helps alleviate the joint toxicity of PVC+Cd pollution in sorghum plants

Combined microplastic and heavy metal pollution (CM-HP) has become a popular research topic due to the ability of these pollutants to have complex interactions. Plant growth-promoting rhizobacteria (PGPR) are widely used to alleviate stress from heavy metal pollution in plants. However, the effects and mechanisms by which these bacteria interact under CM-HP have not been extensively studied. In this study, we isolated and screened PGPR from CM-HP soils and analyzed the effects of these PGPR on sorghum growth and Cd accumulation under combined PVC+Cd pollution through pot experiments. The results showed that the length and biomass of sorghum plants grown in PVC+Cd contaminated soil were significantly lower than those grown in soils contaminated with Cd alone, revealing an enhancement in toxicity when the two contaminants were mixed. Seven isolated and screened PGPR strains effectively alleviated stress due to PVC+Cd contamination, which resulted in a significant enhancement in sorghum biomass. PGPR mitigated the decrease in soil available potassium, available phosphorus and alkali-hydrolyzable nitrogen content caused by combined PVC+Cd pollution and increased the contents of these soil nutrients. Soil treatment with combined PVC+Cd pollution and PGPR inoculation can affect rhizosphere bacterial communities and change the composition of dominant populations, such as Proteobacteria, Firmicutes, and Actinobacteria. PICRUSt2 functional profile prediction revealed that combined PVC+Cd pollution and PGPR inoculation affected nitrogen fixation, nitrification, denitrification, organic phosphorus mineralization, inorganic phosphorus solubilization and the composition and abundance of genes related the N and P cycles. The Mantel test showed that functional strain abundance, the diversity index and N and P cycling-related genes were affected by test strain inoculation and were significant factors affecting sorghum growth, Cd content and accumulation. This study revealed that soil inoculation with isolated and screened PGPR can affect the soil inorganic nutrient content and bacterial community composition, thereby alleviating the stress caused by CM-HP and providing a theoretical basis and data support for the remediation of CM-HP.

Influence of mineral source and inclusion levels of iron, copper, and zinc on the oxidative stability of extruded cat food

This study aimed to compare inorganic sources (sulfates) and chelated organic sources (proteinates) of minerals on the oxidative stability and shelf-life of extruded cat food. Five complete foods were formulated, including a negative control without supplementation of iron (Fe), copper (Cu), or zinc (Zn). The other formulations were obtained by supplementing the negative control formulation with these microminerals in organic or inorganic form at one (1x) or two (2x) times the FEDIAF (2021) requirement level for adult cats. The effects of supplementation on oxidative stability and shelf-life were determined before and after extrusion and during the 365-day storage period. The levels of fatty acids and synthetic antioxidants (BHA and BHT) were significantly lower after extrusion (P < 0.05). While inorganic and organic mineral sources did not differ, the negative control retained higher levels of fatty acids and synthetic antioxidants compared to mineral sources and levels. After extrusion, saturated, monounsaturated, and polyunsaturated fatty acids were reduced by 22.82% ± 1.8%, 22.91% ± 1.9%, and 19.32% ± 2.5%, respectively, with no mineral source and level effects. The Concentrations of synthetic antioxidants were significantly lower after extrusion, with a retention of 49.72% in the negative control and 35.09% ± 1.23% in the other treatments. Storage studies showed that fatty acids declined over time without significant treatment differences (P > 0.05). As expected, the most evident change was that of polyunsaturated fatty acids. Synthetic antioxidant levels also lowered during storage, with significant differences among treatments (P < 0.05). The highest losses were observed in formulations supplemented with inorganic sources. These differences affected peroxide value, which was influenced by both supplementation level and source. At the end of 365 days of shelf life, the peroxide value in foods supplemented with inorganic minerals was 92.3% (1×) and 49.7% (2×) greater than in foods with the same level of organic minerals. The negative control formulation had the lowest peroxide value among all treatments. From this data, we can conclude that the source of the microelements Fe, Cu, and Zn does not influence the oxidative stability of cat food during the extrusion process; however, the inorganic sources (e.g., sulfates) favor the oxidation during storage, which may be attenuated using less reactive, organic trace mineral sources, such as proteinates.

Roles of the SOM and clay minerals in alleviating the leaching of Pb, Zn, and Cd from the Pb/Zn smelter soil: Multi-surface model and DFT study

Soil organic matter (SOM) and clay minerals are important sinks for reactive heavy metals (HMs) and exogenous hydrogen ions (H+). Therefore, HMs are likely to be released into soil porewater under acid rainfall conditions due to the competitive adsorption of H+. However, negligible Lead, Zinc, and Cadmium (<6 ‰) in the Pb/Zn smelter soil were leached, and the effects of SOM and clay minerals on HMs leaching were unclear. Herein, the H+ consumption and HMs redistribution on SOM and clay minerals were quantitated by the multi-surface model and density functional theory calculations to reveal the roles of SOM and clay minerals in alleviating HMs' leaching. Clay minerals consumed 43.2 %–52.0 % of the exogenous H+, serving as the dominant sink for the exogenous H+ due to its high content and hindering H+ competitive adsorption on SOM. Protonation of the functional groups constituted >90 % of the total H+ captured by clay minerals. Meanwhile, some H+ also competed with HMs for adsorption sites on clay minerals due to its 0.497-fold to 1.54-fold higher binding energies than HMs, resulting in the release of HMs. On the contrary, SOM served as an accommodator for taking over the released HMs from clay minerals. The HMs complexation on the low-affinity sites (R-L−) of SOM was responsible for the recapture of HMs. In Ca-enriched soil, the released HMs were also recaptured by SOM via ion exchange on the R-L-Ca+ and the high-affinity sites (R-H-Ca+) sites due to the 30.8 %–178 % higher binding energies of HMs on these sites than those of Ca. As a result, >63.4 % of the released HMs from clay minerals were transferred to the SOM. Thus, the synergy of SOM and clay minerals in alleviating the leaching of HMs in Pb/Zn smelter soils cannot be ignored in risk assessment and soil remediation.

Identifying Dietary Timing of Organic Trace Minerals to Reduce the Incidence of Osteomyelitis Lameness in Broiler Chickens Using the Aerosol Transmission Model.

Our prior research demonstrated a 20% to 25% reduction in bacterial chondronecrosis with osteomyelitis (BCO) lameness in broilers with organic Zn, Mn, and Cu (Availa® ZMC) supplementation. Expanding on this, we investigated the optimal timing for Availa® ZMC feeding to mitigate BCO lameness and reduce feed additive costs in the poultry industry. In this study, we compared the application of 0.15% Availa® ZMC for 56 days, the first 28 days, and the last 28 days. The experimental design was a randomized block design involving 1560 one-day-old chicks distributed across two wire-floor pens as BCO source infection and four treatment groups with six replicates. The source of BCO infection exhibited a cumulative lameness incidence of 83%, whereas the negative control group showed a 77% cumulative incidence of lameness (p = 0.125). Administering 0.15% of Availa® ZMC during the initial 28 d resulted in a 41.3% reduction in BCO incidence, significantly different from the supplementation during the last 28 d (p < 0.05). However, this reduction did not differ substantially (p > 0.05) from the 56d application period. Hence, administering 0.15% Availa® ZMC during the first four weeks emerges as the optimal timing protocol, providing a defense against lameness comparable to the continuous supplementation throughout the complete production duration. Implementing this feeding approach reduces the cost of feed additive, promotes the health of skeletal bones, and effectively protects against BCO lameness in broilers, offering a valuable consideration for producers seeking optimal outcomes in the poultry industry.