Organic Carbon Content Research Articles

Transect approach for assessing major and trace elemental contamination in agricultural soils of the palamaner division, chittoor district, andhra pradesh, india.

Three soil transects located in the granitic regions of Palamaner mandal, Andhra Pradesh, India, were examined to assess the pollution levels of both primary and secondary metals (Si, Al, Fe, Ca, Mg, Na, K, Cu, Mn, P, and Zn) and to ascertain the degree of soil pollution in agricultural areas. The soils along these transects are slightly acid to neutral, with dark brown to red rubified argillic clay-rich B horizons alongside a moderate cation exchange capacity. The A horizon soils display low organic carbon levels with a moderate variability and contain over 70% SiO2, exhibiting low variability due to limited leaching in a semiarid climate. The findings suggest that iron (Fe) and manganese (Mn) oxides play a role in reducing contamination levels through oxidation and precipitation processes. Furthermore, the soils show low to moderate cation exchange capacity, which restricts the retention of absorbed heavy metals, thus lessening their negative impacts. A two-way ANOVA revealed significant differences in CEC, organic carbon, and total zinc content across different horizons and landscape positions. Si, Al, and Cu had small increases and negative geoaccumulation indices in all soil profiles, suggesting no pollution. However, the Nemerow and mean contamination degree over 6 point to slight to moderate pollution. The analysis identified three distinct clusters with significant variations in contamination factors for SiO2 and Cu. Five principal components were determined, explaining 76% of the total variance, primarily derived from geogenic sources and remaining within acceptable limits. This research on soil transects in granitic regions contributes to a better understanding of the distribution, movement, and concentration of elemental oxides based on slope position, which is essential for pollution assessment and soil quality enhancement.

Differential Exudation Creates Biogeochemically Distinct Microenvironments during Rhizosphere Evolution.

Plant roots and associated microbes release a diverse range of functionally distinct exudates into the surrounding rhizosphere with direct impacts on soil carbon storage, nutrient availability, and contaminant dynamics. Yet mechanistic linkages between root exudation and emergent biogeochemical processes remain challenging to measure nondestructively, in real soil, over time. Here we used a novel combination of in situ microsensors with high-resolution mass spectrometry to measure, nondestructively, changing exudation and associated biogeochemical dynamics along single growing plant roots (Avena sativa). We found that metabolite and dissolved organic carbon (DOC) concentrations as well as microbial growth, redox potential (EH), and pH dynamics vary significantly among bulk soil, root tip, and more mature root zones. Surprisingly, the significant spike of rhizosphere DOC upon root tip emergence did not significantly correlate with any biogeochemical parameters. However, the presence of sugars significantly correlated with declines in EH following the arrival of the root tip, likely due to enhanced microbial oxygen demand. Similarly, the presence of organic acids significantly correlated to declines in pH upon root tip emergence. Overall, our in situ measurements highlight how different exudates released along growing roots create functionally distinct soil microenvironments that evolve over time.

Effect of ozone on Vibrio removal in a simulated earthen shrimp pond

ABSTRACT This study investigated the efficacy of ozone treatment on Vibrio pathogen removal within a simulated earthen shrimp pond, conducted in three phases. First, physical and chemical properties of the soil, alongside the Vibrio pathogen, were assessed. Results indicated neutral pH levels, high organic matter, and organic carbon content, with a Vibrio pathogen load of 1.0 ± 0.0 × 103 CFU/mg. Second, ozone treatment was applied, comparing its effectiveness in Vibrio pathogen control between treated and untreated soil sets. The treated set exhibited a significantly lower Vibrio pathogen load (6.00 ± 1.41 × 103 CFU/mg) compared to the untreated control (2.00 ± 2.12 × 105 CFU/mg), resulting in a 97.23% eradication efficiency. Concurrently, ammonia rates decreased with ozone, indicating potential benefits for shrimp aquaculture. Finally, ozone application in a simulated earthen pond over 45 days effectively controlled Vibrio pathogens. In the untreated soil set, Vibrio pathogen levels rose to 9.48 ± 1.73 × 105 CFU/mg, while in the ozone-treated, they ranged from 6.5 ± 2.12 × 103 to 1.25 ± 0.29 × 105 CFU/mg. Shrimp growth parameters, including average daily gain, survival rates, and feed conversion ratio, were compared between groups, suggesting ozone treatment's feasibility without adverse effects on shrimp growth. Water quality parameters remained within suitable ranges for shrimp cultivation. These findings highlight ozone's potential as an effective method for Vibrio pathogen control in shrimp aquaculture, with implications for industry sustainability and productivity.

Ratios of organic mass to organic carbon in fine particulate matter at urban sites in China and Korea during winter and summer.

This study evaluates the composition and seasonal characteristics of fine particulate matter (PM2.5) during winter and summer through simultaneous measurements conducted at the Gwangju Institute of Science and Technology in South Korea and the Changping campus of Peking University in China. PM2.5 samples were concurrently collected at both sites, and chemical analyses were conducted to quantify various components, including carbonaceous materials, ionic species, and metals. Although the average PM2.5 concentrations were comparable between the two sites, there were distinct differences in the concentrations of major components. Organic indicator compounds were analyzed to discern the contributions of primary and secondary pollution sources. Changping displayed a mix of primary and secondary pollution, characterized by higher concentrations of primary organic carbon (POC) such as polycyclic aromatic hydrocarbons and hopanes, compared to Gwangju. In contrast, Gwangju demonstrated a higher prevalence of secondary organic carbon (SOC), particularly water-soluble organic carbon not related to biomass burning (WSOCnbb) and various polar organic compounds. The organic mass to organic carbon (OM/OC) ratios estimated using the mass balance method revealed significant differences, with Gwangju showing a higher ratio of 2.3 compared to 1.9 at Changping, indicating a greater influence of secondary pollutants at Gwangju. Additionally, both Changping and Gwangju exhibited higher OM/OC ratios in summer (Changping: 2.0, Gwangju: 2.5) compared to winter (Changping: 1.8, Gwangju: 2.2), indicating seasonal differences in organic mass contributions to PM2.5. These findings underscore the importance of accounting for spatial and seasonal variations in air pollution studies and suggest that updating commonly used OM/OC ratios could enhance the reliability of research outcomes.

Spatial distribution of bacterial communities driven by environmental factors in the sediment of Lateolabrax japonicus ponds

Dynamic changes of bacterial communities in the sediment are very important for preventing diseases and water quality in aquaculture ponds. In this study, bacterial communities in the sediment of Sea perch Lateolabrax japonicus, an important farmed fish in China, ponds were studied using 16S rRNA Illumina sequencing and functional gene array. At the phylum level, Pseudomonadota, Actinomycetota and Chloroflexota were the dominant species. The bacterial community composition was different in spatial variation. Among the environmental factors, the concentration of nitrogen related factors (TN, NO3−-N NH3-N, NO2−N) and total organic carbon was the main impact on the composition of bacterial community, especially denitrifying bacterial community. Nitrifying and denitrifying bacteria accounted for 4.81 %, and bacteria related to nitrogen cycle accounted for 18.36 %. Higher diversity of bacteria in healthy fish pond than that of the diseased fish pond. In the diseased fish pond, lower abundance of Nitrosospira and higher abundance of Nitrobacter were found, and the contents of NH3-N, NO2−-N and total organic carbon were significantly higher. This study would help to reveal that microbial community structure could reflect the health of cultured animal and surroundings, and it could provide a theoretical reference for the healthy environments in the sediment of Sea perch ponds in South China.

Depth-dependent Effects of Leguminous Crops on Soil Nitrogen-Fixing Microbial Communities Correlated with Carbon Degradation

Abstract Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity. Current research on the effects of legumes predominantly focuses on surface soil, lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms. Here, the community structure of soil nitrogen-fixing microorganisms in three soil layers (0-20, 20-50, and 50-100 cm) under legume and non-legume cultivation was investigated through metagenomic sequencing. We found that only in topsoil (0-20 cm) legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment. Under legume cultivation, the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers, whereas non-legume treatment displayed an inverse depth-dependent pattern. Combining soil physicochemical properties, the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture, total carbon (TC), and dissolved organic carbon (DOC) content. Both TC and DOC were identified as key drivers of these genes. Subsequently, a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops. The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually, distinct from non-legume treatment. Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation, providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.

Engineered biochars for simultaneous immobilization of as and Cd in soil: Field evidence

Agricultural soil contamination by potentially toxic elements (PTEs) such as arsenic (As) and cadmium (Cd) poses a serious threat to food security. Immobilization serves as a widely used approach for the remediation of PTEs contaminated soils, nevertheless, the long-term effectiveness for the simultaneous immobilization of both cations and oxyanions remains a challenge. In order to effectively enhance the synergistic immobilization effect of soil As and Cd contaminated by multiple elements and improve the ecological environment of farmland. In this study, a typical polluted tailings area farmland was selected for situ immobilization experiments, and biochar was prepared from cow manure (CMB), rice straw (RSB), and pine wood (PWB) as raw materials. On this basis, the pristine biochar was modified with ferric chloride (F), potassium permanganate (K), magnesium chloride (M), and aluminum chloride (A), respectively. Furthermore, the immobilization effect of modified biochar on As-Cd and the stress effect on soil respiration were investigated. The results showed that CMB and RSB reduced the bioavailability of heavy metals, potassium permanganate has strong oxidizing properties, and the strong oxidability of potassium permanganate stimulated the generation of more oxygen-containing functional groups on the surface of biochar, thereby enhancing the adsorption and complexation effect of modified materials on As and Cd. Among them, the extracted Cd concentration of Diethylenetriamine pentaacetic acid (DTPA) in KCMB and KRSB in 2020 decreased by 8.23–43.12% and 9.67–35.29% compared to other treatments, respectively. Meanwhile, the KCMB and KRSB treatments also reduced the enrichment of As and Cd in plant tissues. In addition, the dissolved organic carbon (DOC) content in KCMB treatment was relatively high, and the carbon stability of the material was weakened. Simultaneously, the soil respiration emission of KCMB treatment was increased by 5.63% and 11.93% compared to KRSB and KPWB treatments, respectively. In addition, the structural equation also shows that DOC has a large positive effect on soil respiration. In summary, the KRSB treatment effectively achieve synergistic immobilization of As-Cd and provide important guiding significance for green and low-carbon remediation of polluted farmland.

Potential of Hyperspectral Data Combined With Optimal Band Combination Algorithm for Estimating Soil Organic Carbon Content in Lakeside Oasis

ABSTRACTAccurate estimation of soil organic carbon (SOC) content is essential for promoting regional sustainable agriculture and improving land quality. Visible and near‐infrared (Vis‐NIR) near‐Earth remote sensing spectroscopy has become an effective alternative to the traditional time‐consuming and costly methods due to its high‐resolution and nondestructive application, but it is vulnerable to the redundancy of spectral information and the overlap between bands. This study delves into the potential of optimal spectral parameters for estimating SOC in arid lakeside oases, using Bosten Lake in Xinjiang, China, as a focal point. Soil samples (0–10 cm, 10–20 cm, 20–30 cm, 30–40 cm) were collected, and their SOC content and hyperspectral reflectance were measured. The spectral data underwent preprocessing techniques, including continuum removal (CR), standard normal variate (SNV), and continuous wavelet transform (CWT). SOC content was predicted using back propagation neural network models constructed based on one‐dimensional (1D), two‐dimensional (2D), and three‐dimensional (3D) correlation coefficients. Results showcased the effectiveness of the CWT method in accentuating potential spectral information and enhancing variable correlation. Among the indices, 3D exhibited the highest performance (R2 = 0.82, RPD = 2.02 for TDI‐1 at 0–10 cm; R2 = 0.85, RPD = 2.28 for TDI‐2 at 10–20 cm; R2 = 0.83, RPD = 2.24 for TDI‐1 at 20–30 cm; R2 = 0.86, RPD = 2.53 for TDI‐4 at 30–40 cm), followed by 2D and then 1D. These insights offer guidance for future strategies in hyperspectral data preprocessing and spectral index determination, facilitating SOC spatial distribution mapping and advancing sustainable agricultural planning. They also have implications for determining the spatial distribution of SOC content based on spatial interpolation, which would contribute to regional agricultural planning and sustainable development.

Temperature sensitivity of soil respiration declines with climate warming in subalpine and alpine grassland soils

AbstractWarming as a climate change phenomenon affects soil organic matter dynamics, especially in high elevation ecosystems. However, our understanding of the controls of soil organic matter mineralization and dynamics remains limited, particularly in alpine (above treeline) and subalpine (below treeline) grassland ecosystems. Here, we investigated how downslope (warming) and upslope (cooling) translocations, in a 5-years reciprocal transplanting experiment, affects soil respiration and its temperature sensitivity (Q10), soil aggregation, and soil organic matter carbon (C) and nitrogen (N) composition (C/N ratio). Downslope translocation of the alpine (2440 m a.s.l.) and subalpine (1850 m a.s.l.) to the lowland site (350 m a.s.l.) resulted in a temperature change during the growing seasons of + 4.4K and + 3.3K, respectively. Warming of alpine soils (+ 4.4K) reduced soil organic carbon (SOC) content by 32%, which was accompanied by a significant decrease of soil macroaggregates. Macroaggregate breakdown induced an increased respiration quotient (qCO2) by 27% following warming of alpine soils. The increase in qCO2 respiration was associated with a significant decrease (from 2.84 ± 0.05 to 2.46 ± 0.05) in Q10, and a change in soil organic matter composition (lower C/N ratios). Cooling did not show the opposite patterns to warming, implying that other mechanisms, such as plant and microbial community shifts and adaptation, were involved. This study highlights the important role of SOC degradability in regulating the temperature response of soil organic matter mineralization. To predict the adverse effect of warming on soil CO2 release and, consequently, its negative feedback on climate change, a comprehensive understanding of the mechanisms of C storage and turnover is needed, especially at high elevations in the Alps that are particularly affected by rising temperatures.

Vegetation degradation reduces aggregate associated carbon by reducing both labile and stable carbon fraction in Northeast China

Vegetation changes can affect soil organic carbon (SOC) content and storage by altering the inputs of plant biomass and the catabolism and anabolism of soil microorganisms. However, influence of vegetation degradation on aggregate associated carbon fractions and the contribution of different aggregates to total SOC in bulk soil remains poorly understood. In this study, undisturbed soil samples were collected from three types of grassland in Songnen grassland: an undegraded grassland (LEY, Leymus chinensis), a moderately degraded grassland (CHL, Chloris virgata), and a severely degraded grassland (SUA, Suaeda heteroptera). Three soil aggregates including macroaggregate (> 0.25 mm), microaggregate (0.053–0.25 mm) and silt and clay fraction (< 0.053 mm) were separated using wet sieving. Contents of total SOC, soil labile and stable carbon in bulk soil and different soil aggregates were measured. Compared with LEY, the mean weight diameter and geometric mean diameter under the degraded vegetation communities reduced by 39.42 % and 28.47 %, respectively. The reduction in SOC contents in bulk soil, macroaggregate, microaggregate and silt and clay fraction resulting from vegetation degradation was 49.81 %, 26.00 %, 76.17 % and 43.65 %, respectively. Under the degraded vegetation communities, contents of soil labile and stable carbon in bulk soil (45.73 % and 52.61 %, respectively), macroaggregate (17.38 % and 31.61 %, respectively), microaggregate (77.83 % and 74.18 %, respectively), and silt and clay fraction (21.20 % and 53.45 %, respectively) were significantly lower than those under LEY. The contribution of macroaggregate, microaggregate and silt and clay fraction to total SOC was 13.27 %, 23.61 % and 63.12 %, respectively. The contribution of soil aggregates to total SOC following vegetation degradation reduced by 53.63 % for microaggregate, but increased by 47.10 % for silt and clay fraction. These findings collectively indicate that vegetation degradation reduces the aggregate associated carbon content by reducing both labile and stable carbon fraction in Songnen grassland, and sustainable vegetation restoration strategies are need to enhance soil carbon storage in Northeast China.

Characteristics and Drivers of Soil Carbon, Nitrogen, and Phosphorus Ecological Stoichiometry at the Heavy Degradation Stage of the Alpine Meadow

An in-depth understanding of the soil nutrient status and balance relationship can help the effective recovery and management of alpine degraded meadows. In order to study the balance relationship among soil carbon, nitrogen, and phosphorus nutrients during the heavy degradation stage of meadows, field sampling and investigation, indoor analysis, and mathematical statistics were used to explore the characteristics and driving factors of changes in soil carbon, nitrogen, and phosphorus content, storage, and ecological stoichiometry during the heavy degradation stage of alpine meadows in the Sanjiangyuan region. The results showed that in the heavy degradation stage, miscellaneous grass plants occupied absolute dominance, soil C∶N∶P was approximately 32.83∶3.87∶0.67, and there was certain nitrogen limitation. The coefficients of variation of soil carbon, nitrogen, and phosphorus content were in the following order： organic carbon （1.09） &gt; total nitrogen （0.63） &gt; total phosphorus （0.29）. The organic carbon content and the carbon and nitrogen ratio showed a significant linear decreasing trend with the increase in the grassland degradation index （GDI）, while the total phosphorus content and organic carbon storage showed a significant non-linear change, in which the total phosphorus content showed a significant gentle U-shaped distribution, and the organic carbon storage decreased more gently at the beginning of the heavy degradation stage and then decreased sharply when the GDI was 57.9. The results of Mantel correlation analysis showed that the soil carbon to nitrogen ratio, carbon to phosphorus ratio, and nitrogen to phosphorus ratio showed significant correlation with organic carbon content and storage and total nitrogen storage. The results of structural equation modeling indicated that soil water content had direct effects as well as indirect through vegetation factors, soil carbon, nitrogen, and phosphorus ecological stoichiometry ratios, and soil water content and vegetation factors （height, cover, and biomass） were key environmental factors affecting soil ecological stoichiometry. The research results can provide scientific basis and practical guidance for the restoration of heavily degraded grassland in alpine meadows.

Biochar affects organic carbon composition and stability in highly acidic tea plantation soil

Biochar amendments are effective in stabilizing soil aggregates and improving soil organic carbon (SOC) content. However, the effects of biochar on highly acidic soil and their relation with soil SOC stability remain understudied. The study aimed to investigate the impact of biochar on changes of aggregate distribution and SOC stability in a highly acidic tea plantation soils over an eight-year period. Soil samples were collected from plots with varying biochar application amounts (0, 2.5 t ha−1, 5 t ha−1, 10 t ha−1, 20 t ha−1 and 40 t ha−1). The content of SOC, iron bound organic carbon (OC-Fe), particulate organic carbon (POC), mineral-associated organic carbon (MAOC) and the functional group composition of SOC was analyzed. The results indicated that in the biochar application treatments, the value of soil pH, SOC, POC and MAOC contents were increased from 3.92 to 4.28, 6.68%–187.02%, 8.31%–66.78% and 13.07%–236.47% respectively, compared with CK, while the content of macro-aggregate (particle size>0.25 mm) and soil aggregates mean weight diameter (MWD) significantly increased with higher biochar application amounts. But dissolved organic carbon (DOC) and OC-Fe content exhibited downward trend, decreased from 2.43% to 6.97% and 4.18%–19.91%. Furthermore, aromatic-C levels increased, with increased biochar application amounts. The integration of biochar not only bolstered soil aggregate stability but also amplified the presence of aromatic-C, thereby enhancing the resilience of organic carbon in highly acidic tea garden soil (BC40 > BC20 > BC5>BC2.5 > BC10 > CK), with increases ranging from 6% to 47%. The principal component analysis and structural equation modeling identified soil pH, TN, SOC, POC, MAOC, R > 0.25 and MWD as key factors of soil organic carbon stability. These findings provide crucial insights into the mechanism underlying biochar's efficiency in fortifying organic carbon stability, particularly in the context of highly acidic soil.

Characteristics of Soil Respiration and Organic Carbon Mineralization in Dryland Potato Fields Under Different Ridge-furrow Mulching Patterns

Exploring the response mechanism of soil respiration rate to hydrothermal factors and organic carbon mineralization under different ridge-furrow mulching modes is of high importance for the development of the regional carbon cycle and assessment of its ecological benefits. An experimental study was carried out in 2020 in a dry-crop potato field in the mountainous area of southern Ningxia by setting three furrow-ridge ratios [60 cm∶30 cm （R1）, 60 cm∶45 cm （R2）, and 60 cm∶60 cm （R3）] combined with three mulching modes [ridge covered with ordinary plastic film, furrow covered with straw （DJ）, degradable water-permeable plastic film （DS）, and no mulching （DB） in furrows, respectively]. The soil hydrothermal factors, respiration rate, organic carbon content, and mineralization characteristics of potatoes during the reproductive period under different mulching modes were investigated with plain mulching without mulching （CK） as the control. The results showed that different furrow-ridge ratios combined with the mulching mode could significantly increase the soil water storage capacity in the 0-60 cm layer, and the R3DJ treatment had a better effect, with a significant increase of 24.99% compared with that in CK. The R2 treatment had the best effect of increasing temperature during the whole life cycle of the potato. The DS treatment had the effect of increasing temperature, and the DJ treatment had the effect of decreasing temperature under different mulching materials. Different furrow and ridge cover patterns could significantly increase the average soil respiration rate during the reproductive period, and the R3DS treatment was the most significant among the different furrow and ridge cover patterns, with a significant increase of 24.71% compared with that in the CK treatment. The soil organic carbon content in the 0-20 cm and 20-40 cm layers at harvest time was higher in the R2 and R1 ridges, respectively, and higher in the DB and DS treatments for different mulching materials. The soil organic carbon mineralization rate declined rapidly in the early stage of cultivation and then slowly declined and leveled off in the middle and late stages, which was highest in the R3 treatment for the three types of ridge ratios and highest in the DS treatment for different mulching materials. The fitting equations of soil respiration rate with soil hydrothermal factors during the reproductive period revealed that the synergistic effect of soil hydrothermal dual factors on soil respiration was higher than that of a soil hydrothermal single factor and that the quadratic hydrothermal dual factors could well explain 86.4% to 99.9% of the soil respiration. Correlation analysis showed that the average soil respiration rate during the whole life span of the potato was highly significantly and positively correlated with the average soil temperature in the 0-25 cm layer and the average soil organic carbon mineralization rate in the 0-40 cm layer, and the soil temperature was highly significantly and positively correlated with the organic carbon mineralization rate. The furrow-ridge ratio combined with the mulching mode was shown to improve the soil hydrothermal environment and increase the rate of organic carbon mineralization, thus affecting the soil respiration rate, with a furrow-ridge ratio of 60 cm∶45 cm or 60 cm∶60 cm under the ridge mulching mulch ditch covering biodegradable seepage mulch mode being more effective.

Effects of Two Different Size ZnO Nanoparticles on the Growth of Aspergillus oryzae

Two different kinds of ZnO nanoparticles (NPs) with distinct particle sizes were synthesized by a precipitation method. For the first time, the effects of two distinct sizes ZnO NPs on the growth, photoluminescence properties and kojic acid (KA) yield of Aspergillus oryzae (A. oryzae) were examined. The findings showed that ZnO-A and -B NPs, with average particle sizes of 11.93 nm and 34.41[Formula: see text]nm, respectively, exhibited a hexagonal crystal structure. It was found that when the concentration of NPs was below 100[Formula: see text][Formula: see text]g/mL, ZnO NPs were nontoxic and served as activators to stimulate the growth of A. oryzae, and the biomass of solid and liquid medium, the total integral emission intensity, the content of extracellular protein and total organic carbon and KA yield of A. oryzae grown with ZnO-A (ZnO-B) NPs were about 2.19 (1.97), 2.47 (1.56), 1.67 (1.16), 2.45 (1.95), 0.47 (0.50) and 2.07 (1.37) times more than that of control sample (without NPs), respectively.

Phosphogypsum with Rice Cultivation Driven Saline-Alkali Soil Remediation Alters the Microbial Community Structure.

The improvement of saline-alkali land plays a key role in ensuring food security and promoting agricultural development. Saline soils modifies the response of the soil microbial community, but research is still limited. The effects of applying phosphogypsum with rice cultivation (PRC) on soil physicochemical properties and bacterial community in soda saline-alkali paddy fields in Songnen Plain, China were studied. The results showed that the PRC significantly improved the physicochemical properties of soil, significantly reduced the salinity, increased the utilization efficiency of carbon, nitrogen, and phosphorus, and significantly increased the activities of urease and phosphatase. The activities of urease and phosphatase were significantly correlated with the contents of total organic carbon and total carbon. A redundancy analysis showed that pH, AP, ESP, HCO3-, and Na+ were dominant factors in determining the bacterial community structure. The results showed that PRC could improve soil quality and enhance the ecosystem functionality of soda saline-alkali paddy fields by increasing nutrient content, stimulating soil enzyme activity, and regulating bacterial community improvement. After many years of PRC, the soda-alkali soil paddy field still develops continuously and healthily, which will provide a new idea for sustainable land use management and agricultural development.

Effects of Microplastics on Soil N2O Emission and Nitrogen Transformations from Tropical Agricultural Soils

A widespread concern had been there regarding soil ecological and environmental problems caused by microplastic pollution in agricultural soils. A controlled laboratory incubation experiment was performed to examine the effects of different types of microplastics on soil properties, N2O emissions, and nitrogen （N） transformations in tropical arable soils from a pepper-corn cropping system in Hainan Province. Three treatments were done： soil without microplastics （CK） and soil amended with 5% of polyethylene （PE） or with 5% of polybutylene adipate co-terephthalate （PBAT）. The results showed that both types of microplastic addition increased soil pH, soil organic carbon （SOC）, and dissolved organic carbon （DOC） contents, with stronger treatment effects observed for PBAT than those for the PE treatment. In addition, the PE and PBAT treatments increased soil ammonium nitrogen （NH4+-N） contents by 66.07% and 119.65% and decreased nitrate nitrogen （NO3--N） contents by 8.56% and 29.68%, respectively. Compared to those in the CK treatment, the addition of PBAT significantly increased soil N2O emissions by 254.92% （P < 0.05）, whereas that of PE produced no significant effects. Furthermore, both the PE and PBAT treatments increased soil net nitrogen mineralization rate （NMR） and decreased soil net nitrification rate （NNR）, with more obvious treatment effects observed in PBAT than in the PE treatment. PBAT addition increased the abundance of ureC, while PE had no significant effects. Microplastic addition reduced the abundance of nitrifying gene abundances （AOA-amoA, AOB-amoA, and nxrA）, with more obvious treatment effects found in the PBAT treatment. Further, PBAT addition significantly increased the gene abundances of nirK, nirS, nosZ, and fungal nirK （P < 0.05）, whereas the addition of PE had no significant effect on those gene abundances. Soil N2O emissions had positive relationships with NH4+-N intensity, pH, DOC, SOC, and nirS abundance. In conclusion, biodegradable microplastics addition produced stronger influences on soil properties and N transformations than the non-biodegradable one in tropical arable soils and aggravated soil N2O emissions mainly by promoting denitrification.

The effects of roots and earthworms on aggregate size distribution and their associated carbon under contrasting soil types and soil moisture conditions

Soil’s potential as a carbon sink is uncertain due to biotic and abiotic interactions. Soil aggregates are important carriers of organic carbon (OC), and clarifying the response of aggregates and their associated OC to plant roots and earthworms can better understand the carbon cycle in terrestrial ecosystems. Herein, we determined the regulatory role of plant roots (Lolium perenne) and earthworms (Metaphire tschiliensis) in isolation and in combination on aggregate size distribution and their associated OC and readily oxidizable OC (ROOC) under contrasting soil types (Phaeozems and Anthrosols) and soil moisture conditions (constant wetting, CW; wetting–drying cycle repeated four times, 4WD) by a laboratory microcosm experiment. Results showed that earthworm presence significantly increased plant biomass by 30 % and 221 % in Phaeozems and Anthrosols, respectively (p < 0.05). For Phaeozems, plant alone (P) and plant and earthworm in combination (PE) had lower proportion of large aggregate (5–8 and 2–5 mm) than bare soil (CK) under 4WD condition (p < 0.05). For Anthrosols, the PE treatment decreased the proportion of 5–8 and 2–5 mm aggregate by 45 % and 25 %, respectively, under CW condition, and decreased the proportion of 5–8 mm aggregate by 37 % under 4WD condition (p < 0.05). Moreover, the proportion of 5–8 and 2–5 mm aggregate in P treatment was lower under CW condition (6.92 % and 22.13 %) but was higher under 4WD condition (11.49 % and 32.55 %) than those in CK (14.69 % and 29.91 %; 8.85 % and 20.56 %) (p < 0.05). Our results further indicated that the PE treatment had relatively higher OC and ROOC contents, especially for small aggregates in Anthrosols. The study indicates that plant roots and earthworms significantly influence aggregate turnover and the carbon cycle, with soil type and moisture playing a crucial role.

Unveiling the main drivers of tree decline in Zagros semi-arid forests

Abstract Tree decline in arid and semi-arid forest ecosystems causes severe socioeconomic and ecological problems and thus needs to be thoroughly quantified and monitored across space and time. This study investigates tree and forest decline in Iran’s Zagros forests, considering environmental factors (e.g. topographic, soil, and climatic variables). We used field data from Chaharmahal-and-Bakhtiari (a study area covering 165 km2) and environmental data derived from freely available databases. Relationships between tree, forest decline, and environmental data were analyzed using generalized additive models. Our findings reveal that slope and the BioClim-16 variable (precipitation of the wettest quarter) significantly influence tree decline across various decline classes (P-values: slope = .009, BioClim-16 = .02). The best multivariate model for forest decline incorporated soil organic carbon and silt as predictive variables, with soil organic carbon emerging as the key factor (P-value = .04). Additionally, a spectral analysis of bare soil in declining and non-declining areas consistently demonstrated reduced reflectance values in declining regions across 10 Sentinel-2 bands, with VNIR-3, SWIR-2, red, green, and blue bands consistently showing significant differences as unveiled by the Wilcoxon test in all seasons except winter. These reduced reflectance values may indicate that forests stocked on soils with larger grain size (a higher fraction of sand) and/or higher organic carbon content may be more vulnerable to decline. This study contributes to our hitherto understanding of the main drivers of tree and forest decline in semi-arid forests, among others underscoring the potential utility of the spectral properties of bare soil in sparse semi-arid forests to predict the likelihood of tree decline.

Enhanced synergistic catalysis of bisphenol A in river water using an anti-aging photocatalytic membrane

Bisphenol A (BPA), as an endocrine disruptor, poses a potential threat to ecosystems and human health in aquatic environments. Membrane catalytic systems can accelerate the degradation of BPA and facilitate its conversion into harmless compounds. Nevertheless, the complex nature of the water environments and the limited stability of catalysts often result in challenges such as catalyst aging and deactivation. Herein, an anti-aging multifunctional AgFeO2 catalytic material with electron transfer membrane support was prepared for synergistic catalysis of low-energy LED light (12 W) excitation and peroxydisulfate (PDS) activation. The anti-aging photocatalytic membrane completely degraded 10 ppm of BPA within 30 min, and did not show significant aging after the long-term synergistic catalytic process. In addition, actual river water was employed to assess the aging process and catalytic efficiency in a practical environment. A 60.79 cm2 photocatalytic membrane completely purified 10 L of BPA polluted river water, while the total organic carbon content decreased by 50 %. This was mainly due to the synergistic catalytic effect of the membrane, which boosted photoelectron transfer through electron transfer shortcuts, thereby enhancing persulfate activation. Overall, the multifunctional membrane provides an effective strategy for achieving a long-lasting catalytic effect and controlling photocatalyst aging in practice.

Sedimentary factors controlling the organic matter enrichment in oil shale, Seyitömer Lacustrine Basin, Western Anatolia: New implications from organic and inorganic geochemistry

AbstractWestern Anatolia, an important segment of the Alp‐Himalayan Belt, hosts numerous Neogene lacustrine basins with potential oil shale reserves surpassing 1.6 billion tonnes. Among these basins, the Seyitömer Basin (Kütahya) stands out, containing oil shales that are intercalated with claystone, marl, limestone and coal layers. This study presents a comprehensive dataset of organic and inorganic chemistry to gain insight into the palaeoclimate and palaeoenvironmental factors that control the enrichment of organic matter. The studied samples exhibit high total organic carbon contents, averaging 12.85% (ranging from 2.22 to 36.21%), high hydrogen indices (486–812 mgHC/g rock) and low oxygen indices (33–70 mgCO2/g total organic carbon), indicating their substantial hydrocarbon‐source potential. These characteristics indicate predominantly ‘excellent’ to occasionally ‘very good’ source rock qualities and very high oil potential. Their pyrolysis, gas chromatography and gas chromatography–mass spectrometer parameters indicate an immature‐early mature characteristic for Seyitömer oil shale samples. They comprise dominantly Type‐I kerogen with minor Type‐II kerogen and lacustrine algal organic matter. Their sedimentological characteristics, along with various geochemical values, such as total organic carbon versus S, B versus Ga and dibenzothiophene/phenanthrene, reveal a moderately deep fresh/brackish to saline lacustrine environment. The Ga/Rb, K/Al and Sr/Cu ratios suggest dominantly humid and warm climate conditions, occasionally interrupted by periods of less humidity. The prevalence of warm and humid climate conditions leads to intense chemical weathering processes, supported by high Chemical Index of Alteration and low Rb/Sr ratios in the associated oil shale samples. Intense chemical weathering and high runoff resulted in dissolved nutrient enrichment, promoting ecological dynamics favourable to increased productivity. Their low Pr/Ph and Mo/total organic carbon ratios, high Ni/Co ratio and, relatively low MoEF/UEF ratio, along with well‐developed lamination of the oil shales, indicate the presence of anoxic conditions in the bottom water. These anoxic conditions would have facilitated the preservation potential of organic matter in the samples. Thus, the palaeoclimate conditions integrated with sedimentary factors have an important role in the ecological dynamic and physical–chemical environmental conditions, ultimately contributing to the organic matter enrichment of the studied samples. This work provides a case study to better understand the sedimentary factors controlling organic matter enrichment in the lacustrine basins of the Alp‐orogenic belt.