Organic Matter Content Research Articles

Effect of thermal maturation and organic matter content on oil shale fracturing

The Pabdeh Formation represents organic matter enrichment in some oil fields, which can be considered a source rock. This study is based on the Rock–Eval, Iatroscan, and electron microscopy imaging results before and after heating the samples. We discovered this immature shale that undergoes burial and diagenesis, in which organic matter is converted into hydrocarbons. Primary migration is the process that transports hydrocarbons in the source rock. We investigated this phenomenon by developing a model that simulates hydrocarbon generation and fluid pressure during kerogen-to-hydrocarbon conversion. Microfractures initially formed at the tip/edge of kerogen and were filled with hydrocarbons, but as catagenesis progressed, the pressure caused by the volume increase of kerogen decreased due to hydrocarbon release. The transformation of solid kerogen into low-density bitumen/oil increased the pressure, leading to the development of damage zones in the source rock. The Pabdeh Formation’s small porethroats hindered effective expulsion, causing an increase in pore fluid pressure inside the initial microfractures. The stress accumulated due to hydrocarbon production, reaching the rock’s fracture strength, further contributed to damage zone development. During the expansion process, microfractures preferentially grew in low-strength pathways such as lithology changes, laminae boundaries, and pre-existing microfractures. When the porous pressure created by each kerogen overlapped, individual microfractures interconnected, forming a network of microfractures within the source rock. This research sheds light on the complex interplay between temperature, hydrocarbon generation, and the development of expulsion fractures in the Pabdeh Formation, providing valuable insights for understanding and optimizing hydrocarbon extraction in similar geological settings.

Effect of cover crop on soil fertility and bacterial diversity in a banana plantation in southwestern China

A cover crop can be an effective strategy to mitigate soil degradation in crops, such as banana. In this study, soil bacterial diversity, chemical properties, enzymatic activities, and bacterial nutrient-related functional genes were examined in the intercropping area of a banana plantation from 2018 to 2020 that had conventional tillage with bare soil (CT), natural weed cover (WC), which was primarily goosegrass (Eleusine indica (L.) Gaerth), or a cover crop of cultivated Siratro (Macroptilium atropurpureum (DC.) Urb.) (SC). By 2020, SC followed by WC and CT treatments were higher in soil organic matter, available nitrogen, total nitrogen and total phosphorus content as well as increased phosphatase, catalase, invertase and urease activities. Compared to CT and WC treatments, the co-occurrence network of SC treatment had higher modularity index indicating a more stable bacterial community. The composition of community was significantly different between the CT and SC treatments in 2019 and 2020, and the WC treatment in 2020. The relative abundance of fatty acids and lipid biosynthesis genes in the soil bacterial microbiome were significantly higher with SC compared to CT and WC in 2019 and 2020, as well as for carbon and nitrogen functional genes in 2020. However, the relative abundance of nucleoside and nucleoside biosynthesis genes were significantly lower with SC compared to CT and WC in 2020. SC treatment increased the relative abundance of Bradyrhizobium and MND1 related to nitrogen cycle and utilization compared to CT in 2019 and 2020. In general, the major benefits of a Siratro cover crop was increased soil organic matter, nitrogen content, and nitrogen fixing bacteria, as well as a more stable soil bacterial community, indicating that it provided multiple potential benefits to the soil of banana.

Application of Moringa Seeds Coagulant to Treat Wastewater from Chicken Slaughterhouse Industry

Liquid waste generated by the chicken slaughterhouse industry results in an increased concentration of organic matter decomposes in the environment. High organic matter content can be achieved by the coagulation-flocculation method. This study aims to determine the removal efficiency of turbidity, BOD, COD, and TSS in the reactor. A dose of 250 mL with a coagulation speed of 100 rpm 1 minute and a flocculation speed of 25 rpm 10 minutes with a variation of settling time of 1.5 hours, 2 hours, and 2.5 hours of moringa seeds were investigated to find reduction levels of turbidity, BOD, COD, and TSS. This study showed that moringa seed coagulants were able to reduce the BOD concentration by 87.74% with an initial level of 662 mg/L to 101.01 mg/L in 2.5 hours, a COD concentration of 61.43% with an initial level of 2240 mg/L to 864 mg/L at 2.5 hours, the TSS concentration was 77.78% with an initial level of 360 mg/L to 80 mg/L at 2.5 hours while the turbidity value was 87.73% with an initial level of 441 NTU to 54.1 NTU. Moringa seeds could be effectively used to reduce the parameters of turbidity, TSS, BOD, and COD.

Gastropoda community structure in the mangrove forest of Ketapang Coastal Waters, Rupat District

Gastropod community structure is a concept or study that studies the arrangement or composition of species in an ecosystem. Changes influence the structure of this gastropod community in terms of environmental factors such as temperature, salinity, substrate type, and organic matter content. Rupat District is geographically located in a cluster of islands directly adjacent to the Strait of Malacca, strongly influenced by coastal environmental conditions. Rupat sub-district has one of three tropical marine ecosystems, namely mangroves. This study aims to determine the structure of gastropod communities in mangrove forests in Ketapang Beach, Rupat District waters. The study was conducted in April 2023 using the technique of random sampling with a total of three stations. There are 8 (eight) species of gastropods found, with the species Cerithidea obtusa the dominant one. The abundance of gastropods is 130,000 ind/ha. The value of the diversity index (H') is 1.24, the uniformity index (E) is 0.33, and the dominance index value (C) is 0.40. The distribution pattern (Id) is grouping. The similarity index (Ss) of gastropods between each station in Ketapang Beach is almost the same type and has similarities that are classified as high category. Test results Oneway ANOVA < 0.05. The LSD (Least Significance Difference) test states that the abundance between stations I and III is significant, just as stations II and III are markedly different. The abundance between station I and station II does not differ markedly.

Deciphering silver nanoparticles perturbation effects and risks for soil enzymes worldwide: Insights from machine learning and soil property integration

Globally extensive research into how silver nanoparticles (AgNPs) affect enzyme activity in soils with differing properties has been limited by cost-prohibitive sampling. In this study, customized machine learning (ML) was used to extract data patterns from complex research, with a hit rate of Random Forest > Multiple Imputation by Chained Equations > Decision Tree > K-Nearest Neighbors. Results showed that soil properties played a pivotal role in determining AgNPs’ effect on soil enzymes, with the order being pH > organic matter (OM) > soil texture ≈ cation exchange capacity (CEC). Notably, soil enzyme activity was more sensitive to AgNPs in acidic soil (pH < 5.5), while elevated OM content (>1.9 %) attenuated AgNPs toxicity. Compared to soil acidification, reducing soil OM content is more detrimental in exacerbating AgNPs’ toxicity and it emerged that clay particles were deemed effective in curbing their toxicity. Meanwhile sand particles played a very different role, and a sandy soil sample at > 40 % of the water holding capacity (WHC), amplified the toxicity of AgNPs. Perturbation mapping of how soil texture alters enzyme activity under AgNPs exposure was generated, where soils with sand (45–65 %), silt (< 22 %), and clay (35–55 %) exhibited even higher probability of positive effects of AgNPs. The average calculation results indicate the sandy clay loam (75.6 %), clay (74.8 %), silt clay (65.8 %), and sandy clay (55.9 %) texture soil demonstrate less AgNPs inhibition effect. The results herein advance the prediction of the effect of AgNPs on soil enzymes globally and determine the soil types that are more sensitive to AgNPs worldwide.

Emerging organic contaminants in the soil-plant-receptor continuum: transport, fate, health risks, and removal mechanisms.

There is a lack of comprehensive reviews tracking emerging organic contaminants (EOCs) within the soil-plant continuum using the source-pathway-receptor-impact-mitigation (SPRIM) framework. Therefore, this review examines existing literature to gain insights into the occurrence, behaviour, fate, health hazards, and strategies for mitigating EOCs within the soil-plant system. EOCs identified in the soil-plant system encompass endocrine-disrupting chemicals, surfactants, pharmaceuticals, personal care products, plasticizers, gasoline additives, flame retardants, and per- and poly-fluoroalkyl substances (PFAS). Sources of EOCs in the soil-plant system include the land application of biosolids, wastewater, and solid wastes rich in EOCs. However, less-studied sources encompass plastics and atmospheric deposition. EOCs are transported from their sources to the soil-plant system and other receptors through human activities, wind-driven processes, and hydrological pathways. The behaviour, persistence, and fate of EOCs within the soil-plant system are discussed, including sorption, degradation, phase partitioning, (bio)transformation, biouptake, translocation, and bioaccumulation in plants. Factors governing the behaviour, persistence, and fate of EOCs in the soil-plant system include pH, redox potential, texture, temperature, and soil organic matter content. The review also discusses the environmental receptors of EOCs, including their exchange with other environmental compartments (aquatic and atmospheric), and interactions with soil organisms. The ecological health risks, human exposure via inhalation of particulate matter and consumption of contaminated food, and hazards associated with various EOCs in the soil-plant system are discussed. Various mitigation measures including removal technologies of EOCs in the soil are discussed. Finally, future research directions are presented.

Diversity of Soil Surface Arthropods Species in Taman Hutan Raya Sultan Syarif Hasyim, Riau Province

Soil surface arthropods are an important part of an ecosystem in the soil which has a role as a bioindicator of ecosystem balance and acts as a decomposer which can decompose organic materials and enrich the organic material content in the soil. This research aims to determine the diversity of soil surface arthropods species in three vegetation types in Taman Hutan Raya Sultan Syarif Hasyim. Sampling was conducted in Taman Hutan Raya Sultan Syarif Hasyim Riau Province in August 2023. This research used a purposive sampling method with a sampling technique using pitfall traps placed in three vegetation types (natural forest, shrubs and oil palm plantation). The overall results include 9 orders, 15 families, 26 species and a total of 2,027 individuals per hectare. In natural forests, there were 7 orders, 12 families, 20 species and 853 individuals per hectare, with a diversity index (H') of 2.27 (medium). In shrubs, there were 6 orders, 8 families, 12 species and 715 individuals per hectare, with an (H') of 2.17 (medium). In oil palm plantations, there were 4 orders, 5 families, 9 species and 549 individuals per hectare, with an (H') of 2.03 (medium)

Investigating the potential of nanobonechar toward climate-smart agriculture.

Extreme climates and the unpredictability of the weather are significant obstacles to agricultural productivity. This study is the first attempt to explore the capacity of nanobonechar (NBC) for promoting climate-smart agriculture. A pot experiment was performed on maize (Zea mays L.) under a deficit irrigation system (40, 70, and 100% irrigation rates) using different soil application rates of the NBC (0, 0.5, 1, and 2% wt/wt). Additionally, the CO2-C efflux rate and cumulative CO2-C were measured in an incubation experiment. The results indicated the best performance of the 1% NBC treatment under a 70% irrigation rate in terms of the fresh and dry weights of maize plants. Total PO43- and Ca2+ were significantly higher in the plants grown in the NBC-amended soil as compared to the control, showing a gradual increase with an increase in the NBC application rate. The improved productivity of maize plants under a deficit irrigation system was associated with enhanced water-holding capacity, organic matter, and bioavailability of cations (Ca2+, K+, and Na+) and anions (PO43- and NO3-) in the soils amended with NBC. The CO2-C efflux rate and cumulative CO2-C emissions remain higher in the NBC-amended soil than in the un-amended soil, pertaining to the high contents of soil organic matter emanating from the NBC. We conclude that NBC could potentially be used as a soil amendment for promoting maize growth under a water stress condition.

Effects of soil properties and land use patterns on the distribution of microplastics: A case study in southwest China

Microplastic pollution in the soil environment is of great concern. However, the current research on microplastics (MPs) in Southwest China mainly focuses on their distribution characteristics and sources in soil, making the understanding of the soil properties and land use patterns influencing soil MPs insufficient. In this study, the abundance and distribution characteristics of MPs in the soil of different land use patterns in Guizhou Province were determined. The results revealed that the average abundance of MPs in soils was 2936 items/kg, ranging from 780 to 9420 items/kg. The MPs were mainly small particle size (0–0.5 mm), granular, and black, accounting for 87.5%, 36.6%, and 82.2%, respectively. The most common polymer types of MPs were polypropylene, polyethylene terephthalate, and polyethylene, which accounted for 20.4%, 16.8%, and 16.4%, respectively. As soil bulk density increased, microplastic abundance and small particle size decreased. Soil microplastic abundance slightly decreased with increasing soil porosity. The abundance of MPs increased with the increase in soil pH, but no significant correlation was observed between soil organic matter content and microplastic abundance. pH was the major factor that affected the microplastic distribution, which accounted for 32.5%. This study provides insight into the distribution and influencing factors of soil MPs and also provides a theoretical basis for subsequent research on soil microplastic pollution.

Soil Ecoenzymatic Stoichiometry Reveals Microbial Metabolic Limitations in Apple Orchards with Cover Crop and Organic Fertilizer Incorporation

Understanding the stoichiometry of extracellular enzymes in soil, particularly in relation to nutrient acquisition (e.g., carbon, nitrogen, phosphorus), provides valuable insights into microorganisms’ resource requirements. This study investigates the metabolic constraints of soil microorganisms in response to different growth stages of apple trees under various soil management practices. A 14-year long-term experiment with a split-plot design was conducted, where the main plots received different cover crop treatments (bare vs. cover crop), and subplots were subjected to four fertilizer treatments (CK, M, NPK, MNPK). The significant main and interactive effects of cover crops, fertilizer treatment, and growth period on soil nutrients were observed (p &lt; 0.001). Both cover crop and fertilizer treatments significantly increased the soil organic matter content, with implications for orchard resilience to drought. However, the cover factor alone did not notably influence soil carbon–nitrogen ratios or microbial communities. Microbial carbon limitations were driven by soil water dynamics and microbial biomass, while microbial phosphorus limitations were closely linked to total nitrogen levels. The results underscore the combination of cover crops and MNPK fertilizer-enhanced soil nutrient levels and enzyme activities, mitigating microbial carbon and phosphorus limitations. These findings suggest practical strategies for optimizing fertilization practices to improve soil fertility and address nutrient constraints in orchard ecosystems.

Biodiversity patterns of macrofauna associated with Halodule wrightii (Ascherson) in meadows of north-eastern Brazil

Context Seagrass meadows are highly productive habitats with a vast species diversity that perform multiple ecosystem services. The fauna associated with these environments is responsible for many of the ecosystem services. Therefore, the fauna composition and functional characteristics should be considered in studies addressing seagrass meadows. Aims This study aimed to evaluate the differences in the taxonomic and functional compositions of the macrofauna associated with Halodule wrightii (Ascherson) meadows subject to different settings of habitat characteristics in the shallow coastal regions of the north-eastern coast of Brazil. Methods We used the Hill diversity series to estimate taxonomic diversity, whereas functional diversity was estimated through biological-trait analyses. Key results Distinct patterns of taxonomic and functional diversities were observed among meadows. However, the composition of functional traits diverged more. Lower taxonomic and functional diversity were observed in the Suape meadows, with values mainly related to the low organic matter content. Catuama meadows presented opposite results, associated with higher organic matter and plant density. Conclusions The meadow heterogeneity can influence the associated macrofauna and its functional characteristics. Implications These results are highly relevant for predicting the consequences of changes in seagrass meadows and how this affects the functioning of these ecosystems.

N2O consumption, uptake, and microbial reduction processes in flooded sandy loamy paddy soils

AbstractSandy loamy soils are widely distributed in fluvial floodplains and experience flooding events frequently, resulting in a large amount of nitrous oxide (N2O) emissions. This case is more serious when the soil use is changed to paddies. It is of great significance to figure out the N2O consumption and its influencing factors in sandy loamy paddy soils to mitigate N2O emissions. In this study, three sandy loamy paddy soils (0–5 cm) originated from lake deposits were selected (S1, S2, and S3) as objectives. A certain concentration of exogenous N2O was added at the bottom of the flooded soil column to monitor the dynamics of N2O and nitrogen (N2) on the soil surface. Total N2O consumption, N2O uptake, and N2 production were quantified, and the abundance of nitrous oxide reductase genes (nosZI, and nosZII) and other soil properties (ammonium‐nitrogen, nitrate‐nitrogen, and dissolved organic carbon [DOC] content) were analyzed. The results showed that the sandy loamy paddy soil column with a depth of 0–5 cm could intercept more than 95% of the exogenous N2O under the flooded anaerobic condition, indicating that the three sandy loamy paddy soils all had extremely strong N2O consumption capacities. And the increment of N2 accounted for 68.73%–76.09% of the total N2O consumption, which had a stronger relationship with the increase of nosZI gene abundance than nosZII gene. In addition, the total N2O consumption and N2 increment of S1 and S3 soils were significantly higher than those of S2 soil. This difference was mainly related to soil organic matter content, total nitrogen content, DOC consumption, and the increase of nosZI gene abundance (p &lt; 0.05). The strong N2O consumption potential of sandy loamy soils can provide feasible solutions for regulating N2O emissions in a wide range of similar environments in fluvial floodplains.

Unraveling the mechanisms of free radicals-based transformation and accumulation of potentially toxic metal(loid)s in biochar- and compost-amended soil-plant systems

Rapid industrialization and urbanization have resulted in the widespread contamination of soil by potentially toxic metal(loid)s (PTMs). Among these, arsenic (As), cadmium (Cd), chromium (Cr) lead (Pb) and nickel (Ni) are particularly concerning, affecting millions of hectares of arable land globally and posing significant threats to food security and human health. Biochar (BC) has emerged as a promising soil amendment due to its ability to mitigate soil pollution by immobilizing contaminants. But how biochar-linked free radicals affect this process in plants and soil remains murky. Additionally, the mechanism of the geochemical transformation of PTMs in soil-plant systems influenced by biochar-based free radicals is unclear. Here, the influence of free radicals on immobilization, and transformation of PTMs in the soil-plant system under various BC and Comp treatment was investigated. Six treatment groups (1% and 2% biochar, compost, combined application, and control) were randomly assigned to pots in a randomized complete block design (RCBD) to test their effects on maize growth. Results revealed that there was a noticeable rise in the concentration of free radicals in both the BC and Comp treatments compared to the control and the combined application of BC and Comp treatments. The biochar treatment showed a slight reduction in these functional groups, suggesting possible adsorption or sequestration onto the BC surface while the Comp treatment led to an increase in functional groups associated with carbohydrates, proteins, and lipids, indicating enhanced organic matter content. The combined treatment exhibited intermediate effects, suggesting a synergistic interaction between Comp and biochar. X-ray diffraction analysis indicated that the BC did not demonstrate significant alterations in soil mineralogy, suggesting minimal direct effects on mineral dissolution or transformation. Conclusively, biochar-generated free radicals, especially hydroxyl radicals (•OH), play a crucial role in PTMs (i.e., Cd, Cr, Ni, As and Pb) immobilization in soil-plant systems. This study provides novel insights into biochar's mechanisms for mitigating PTMs pollution, paving the way for optimized soil amendment strategies.

Mobility and Fate of Potentially Toxic Elements in Soil Environment

AbstractSoil pollution, caused by potentially toxic elements (PTEs), is a significant problem worldwide. This study has investigated the key factors that control the mobility and fate of six PTEs (Pb, Cd, Cr, Cu, Zn, and Ni) which are frequently detected in contaminated soils. The findings of this study demonstrate that smaller particles present in soil show stronger adsorption capacity compared to larger particles because of the higher specific surface area. Moreover, soil with higher organic matter content (e.g., humic acid) exhibits stronger adsorption capacity due to the presence of abundant functional groups namely hydroxyl (─OH) and carboxyl (─COOH). Notably, these functional groups possess high affinity for Pb adsorption, followed by Cd &gt; Cu &gt; Cr &gt; Zn &gt; Ni. The adsorption of most of the PTEs by soil with and without humic acid is better described by the Langmuir isotherm model and pseudo‐second‐order kinetic model. Overall, the experimental results illustrate that soil with high contents of humic acid can restrict the mobility of PTEs. This mechanistic evaluation predicts how soils with different organic matter contents respond to PTEs pollution. This study outcome will be helpful in developing sustainable remediation strategies to tackle pollution caused by PTEs in the soil environment.

Valorization of kiwi waste through composting

ABSTRACT Kiwi waste from the calibration process is a major environmental problem of kiwi production due to landfill deposition. This work aims to contribute to the agronomic use of recycled kiwi waste through composting. With this objective, a composting experiment was carried out with kiwi fruit waste mixed with 5%, 10% and 20% (fresh weight) of wheat straw from bundles used to protect kiwifruit trunks from frost, as abulking agent to increase aeration, in the piles 5S, 10S and 20S, respectively. The highest temperatures for piles 5S and 10S were above 60°C, whereas the temperature did not reach 40°C in the pile with the highest straw content (20S) because the aeration increased heat loss in addition to increased C/N ratio of this pile. Also, the amount of organic matter mineralized decreased with increasing amount of straw because of the high C/N ratio of the straw. The highest total N (29.7 g kg−1) and the lowest C/N ratio (13) of the compost with 5% of straw is important from the agricultural point of view to promote N availability. In contrast, the high electrical conductivity (4.6 dS m−1) of this compost increases the risk of salt accumulation in the soil. Our results show that the compost with 10% straw, with high degree of maturation, absence of poor hygiene indicators as coliforms and pathogens as Salmonella sp., high organic matter content and rich in nutrients, together with the adequate compost pH and low electrical conductivity improves compost quality.

Fibre optic sensing technology for field assessment of thermal conductivity of aquatic sediments

Abstract Purpose This study explores the in situ variability of sediment thermal conductivity (K) in a pond, integrating field-deployed fibre optic sensing with laboratory analyses of sediment properties to enhance our understanding and management of aquatic systems. Materials and methods A 20-m cable setup, consisting of a fibre optic cable (FOC) and a heating tape, was buried at two depths within a channel-shaped section of a pond. Induced temperatures along the FOC were recorded during several heating and cooling periods using distributed temperature sensing (DTS). Thermal conductivity (K) was estimated at five locations along the FOC during the heating periods using the heat conduction theory for an infinite line source. Sediment core samples collected from these locations were analyzed to determine dry bulk density (DBD), organic matter content (OM), and particle size distribution (PSD), exploring their effects on K variability. Results Analysis of core samples identified three distinct layers, each with varying PSD, OM, and DBD. The study revealed substantial spatial differences in the thermal conductivity of sediments, even over very short distances along the FOC, attributed to variations in sediment properties. Through a combination of field and laboratory results, we developed quadratic regression models (R2 &gt; 0.9) to characterize the influence of DBD and OM on K. These models enabled detailed vertical and horizontal characterization of K within specific sediment contexts. Conclusion The study demonstrates the effectiveness of active DTS in detecting in-situ variations in K, emphasizing the impact of OM and DBD on temperature propagation. This study highlights the necessity of considering sediment property variability in modelling heat transfer for accurate water resource management and environmental assessments.

ENSO-driven hydroclimate changes in central Tibetan Plateau since middle Holocene: Evidence from Zhari Namco’s lake sediments

The Tibetan Plateau, often referred to as the “Asian Water Tower”, holds immense significance as a critical water source for billions of people in surrounding regions. Its unique location and extreme environmental conditions contribute to the formation of some of the world largest lakes, crucial components of the regional water cycle. These lakes not only store vast freshwater resources but also play a vital role in regulating the flow and quality of rivers, maintaining a delicate balance in the local ecosystem. Recent decades have witnessed rapid expansion of many plateau lakes, primarily attributed to glacial melt. However, evaluating the contribution of climate forcings to these changes remains challenging. In this study, we reconstructed Zhari Namco's lake-level changes between 5.3 ka and 1.3 ka based on optically stimulated luminescence dating, a period with relatively stable glacial amount on the Tibetan Plateau. Our analysis employed sediment grain size distribution, organic matter contents and their stable carbon isotopes. In contrast to recent expansions, our findings reveal a declining trend in Zhari Namco's lake level since the middle Holocene, consistent with intermittent paleo-shoreline records from major central Tibetan Plateau lakes. This regional decline is likely the result of a weakening of the Indian Summer Monsoon. In addition to the long-term drying trend, we identified high-frequency fluctuations in Zhari Namco's lake level on centennial timescale. Further comparison with hydroclimate records from the tropics suggests that centennial high lake levels correlate with increased monsoonal precipitation during periods when ENSO activities were reduced. This study sheds lights on the historical dynamics and driving mechanisms of Zhari Namco's lake levels, providing valuable insights for predicting the impacts of future climate change on the Tibetan Plateau's water cycle.

Influence of conditioner and straw on the herbaceous plant-based phytoremediation copper tailings: a field trial at Liujiagou tailings pond, China.

A field trial was performed to carry out an enhanced phytoremediation technique for multi-metal contaminated copper tailings by Sudan grass (Sorghum Sudanese), ryegrass (Lolium perenne L.), and Bermuda grass (Cynodon dactylon), using conditioner (TH-LZ01) and straw combination into composite amendments as soil amendments, aimed to obtain the maximum of phytoremediation effect. The results showed that compared with untreated herbaceous plants, the application of conditioner and straw planted with herbaceous plants reduced the pH and conductivity and increased the organic matter and water content of the copper tailings to different degrees. With the addition of conditioner and straw, the DTPA-Cd, DTPA-Cu, DTPA-Pb, and DTPA-Zn contents in the copper tailings showed a decreasing trend compared with the untreated group. The herbaceous plants were promoted to reduce the percentage contents of acid soluble fractions Cd, Cu, Pb, and Zn and to increase the percentage contents of reducible, oxidizable, and residual fractions heavy metals (Cd, Cu, Pb, and Zn) in the copper tailings to different degrees. The contents of Cd, Cu, Pb, and Zn in the underground part of herbaceous plants were higher than those in the aboveground part, and the contents of Cd, Cu, Pb, and Zn in the aboveground part and underground part decreased after adding conditioner and straw, which indicated that the conditioner and straw inhibited the transport of heavy metals in the plant. Furthermore, the principal component analysis showed that the application of conditioner and straw with planting ryegrass had more potential for improving the physicochemical properties of copper tailings and reducing heavy metal toxicity, followed by Bermuda grass and Sudan grass.

Are sulfides the primary host of sedimentary Hg? A case study from the Lower Jurassic of the Surat Basin (Australia)

Several mass extinction events and major paleoenvironmental perturbations during the Phanerozoic have been linked to massive volcanic eruptions, especially those associated with large igneous province (LIP) emplacement. Because magmatism during LIPs can be accompanied by the release and widespread dispersal of mercury (Hg), Hg concentration in sedimentary rocks has proven to be a useful proxy for paleovolcanism. Organic matter is often the primary host of Hg in sedimentary rocks, so total organic carbon (TOC) is commonly used to normalize Hg and thus robustly assess anomalies. Nevertheless, the singular use of anomalies in Hg/TOC to assess volcanic activity is questionable. Sulfides or clay minerals also act as hosts for Hg, with sulfides in particular having a strong affinity for Hg in reducing environments. At the same time, the source of organic matter has a potentially very strong influence on Hg abundance because the Hg binding potential of different organic matter types varies. Here, we investigate the influence of organic matter content and type on Hg concentrations and investigate how Hg is hosted in shallow marine and nearshore sedimentary rocks of the Lower Jurassic Precipice Sandstone and Evergreen Formation from the Surat Basin, Australia. Our results demonstrate that sulfides were likely the main host of Hg in these rocks, despite the general absence of reducing conditions in these rocks and the significant variability in organic matter sources. Our results suggest that researchers should routinely collect sulfide or at least total sulfur concentration data when testing for volcanic Hg enrichment in ancient sedimentary rocks.

[Effects of Four Amendments on Fertility and Labile Organic Carbon Fractions of Acid Purple Soil].

The aim of this study was to explore the effects of four amendments on soil fertility and labile carbon fraction characteristics of acid purple soil, so as to provide scientific basis for nutrient management and carbon storage stability in purple soil. Field experiments were carried out, and six treatments were set up:no fertilization (CK), only chemical fertilizer (F), lime + chemical fertilizer (SF), organic fertilizer + chemical fertilizer (OM), biochar + chemical fertilizer (BF), and vinasse biomass ash + chemical fertilizer (JZ). The contents of soil organic matter, pH, available nutrients, soil integrated fertility index (IFI), dissolved organic carbon (DOC), microbial biomass carbon (MBC), particulate organic carbon (POC), their effective rates, and soil carbon pool management index (CPMI) under different treatments were studied to clarify their relationships. The results showed that:① the application of amendments significantly increased soil pH and the contents of organic matter, alkali-hydrolyzed nitrogen, available phosphorus, and available potassium (P<0.05). The OM and JZ treatments had the most significant increase in soil comprehensive fertility index (P<0.05), with increases of 1.96 and 0.77 and 170.43% and 66.96%, respectively. ② Compared with those in the control treatment, the contents of POC, MBC, and DOC in JZ and OM increased by 110.30% and 84.81%, 61.08% and 46.56%, and 195.87% and 141.67%, respectively. The application of amendments significantly increased the soil carbon pool index (CPI) and CMPI (P<0.05), in which the OM treatment showed the most significant increase, with soil CPI and CMPI values increasing by 107.34% and 90.75% compared with those of the control, respectively. ③ Soil organic carbon and its labile fractions were positively correlated with IFI (P<0.05), and redundancy analysis showed that there were significant differences among different treatments. The interpretation rates of soil IFI, pH, and available potassium to organic carbon and its components reached significant levels, and the order of interpretation rates was IFI(74.6%)>pH (11.7%)>AK(6.5%). The application of vinasse biomass ash and organic fertilizer to acid purple soil had the most significant effect on improving soil fertility and soil quality and was conducive to promoting the accumulation and activation of soil carbon fractions.