Journal of Soils and Sediments最新文献

Purpose

Vanadium-titanium magnetite tailings are bulk industrial solid wastes and can be found in the Panxi Region of Sichuan province. The utilization of vanadium-titanium magnetite tailings as soil represents a viable strategy for achieving extensive depletion, while simultaneously fostering ecological revitalization. In order to effectively reuse the stockpiled Vanadium-titanium magnetite tailings, a comprehensive analysis was conducted to assess their physicochemical attributes, microbial community composition, and mineralogical makeup.

Methods

The morphologies of six heavy metals, V, Cd, Cr, Cu, Ni, and Fe, extracted from different depths of the tailings soil were extracted and analyzed using the modified European Community Bureau of Reference (BCR) sequential extraction procedure. The physicochemical indexes—such as water content, pH, available sulfur, and available potassium, of the tailings soil were analyzed. The microbial community structure was analyzed using high-throughput sequencing, and the mineral composition was analyzed using X-ray diffraction (XRD).

Results and discussion

The concentrations of Ni, Cu, Cr and Cd in the vanadium-titanium magnetite tailings are all within the controllable range. The content of available phosphorus was graded as level 1 (> 40 mg/kg), the content of cation exchange capacity (CEC) was graded as level 1 (> 20 cmol ( +)/kg), and the content of available sulfur was 6.91 times higher than the average value (34.3 mg/kg) of available sulfur of the 10 southern provinces of China. At the T3-D3 sample sites, the Geothermobacter genus prevailed, while Thiobacillus reigned supreme at the remaining sampling locations. The microbial populations in the tailings were primarily influenced by sulfur and iron metabolism. The X-ray diffraction (XRD) analyses showed that pyroxene, mica, cordierite, and kaolinite were the primary minerals in the tailings.

Conclusion

There is a low risk of soil contamination from the utilization of vanadium and titanium magnetite tailings as an ecological reclamation substrate. Organic matter and nitrogen being the limiting indicators of soil utilization. The abundance of Actinobacteria and Bacteroidota can be appropriately intensified during soil utilization to enhance the soil nitrogen and carbon cycling performance. The chemical weathering dominated the tailings, and its maturation could be accelerated by strengthening the chemical weathering pathway of tailings.

Purpose

Drylands occupy 41% of the Earth's surface and 31% of South America. In these environments, anthropogenic climate changes may contribute to the intensification of droughts and increase the susceptibility of lands to desertification. In this study, the evolution, current topics, and the research trends in climate change in four dry environments in South America (Caatinga, Patagonia, Gran Chaco, and the Atacama Desert) were analyzed.

Methods

The database was obtained from the Core Collection of Web of Science. A total of 1,386 scientific papers (1993–2022) were analyzed.

Results

Patagonia accounted for 37.4% of research on climate change in the four studied environments, while the Gran Chaco accounted for only 6.9%. Overall, the research trends indicate the need for the understanding in the increasing severity of drought in the Caatinga and the intensification of fire frequency in the Gran Chaco on soil properties, animals, and plants. The implementation of more sustainable animal production systems, aiming at soil conservation and reducing greenhouse gases (GHG) emissions should be a priority in Patagonia. In Atacama Desert, the relationship between climate change and soil microbiome, as well as plant-microorganism interactions under hyper-arid conditions, represent important research trends in this ecosystem. Across all biomes, quantification of GHG emissions, the development of strategies to promote C sequestration by biomass and in soils and studies to understand the effects of climate change on people's lives have been scarce and urgently need implementation.

Conclusion

There is an urgent need to implement public policies aimed at mitigating and adapting to climate change in the dry climate environments of South America with emphasis on the Gran Chaco, where climate-environmental research is limited, and ecosystem degradation is pronounced.

Purpose

Identification of hotspots of accelerated erosion of soil and organic carbon (OC) is critical to the targeting of soil conservation and sediment management measures. The erosion risk map (ERM) developed by Lilly and Baggaley (Soil erosion risk map of Scotland, 2018) for Scotland estimates erosion risk for the specific soil conditions in the region. However, the ERM provides no soil erosion rates. Erosion rates can be estimated by empirical models such as the Revised Universal Soil Loss Equation (RUSLE). Yet, RUSLE was not developed specifically for the soil conditions in Scotland. Therefore, we evaluated the performance of these two erosion models to determine whether RUSLE erosion rate estimates could be used to quantify the amount of soil eroded from high-risk areas identified in the ERM.

Methods

The study was conducted in the catchment of Loch Davan, Aberdeenshire, Scotland. Organic carbon loss models were constructed to compare land use specific OC yields based on RUSLE and ERM using OC fingerprinting as a benchmark. The estimated soil erosion rates in this study were also compared with recently published estimates in Scotland (Rickson et al. in Developing a method to estimate the costs of soil erosion in high-risk Scottish catchments, 2019).

Results

The region-specific ERM most closely approximated the relative land use OC yields in streambed sediment however, the results of RUSLE were very similar, suggesting that, in this catchment, RUSLE erosion rate estimates could be used to quantify the amount of soil eroded from the high-risk areas identified by ERM. The RUSLE estimates of soil erosion for this catchment were comparable to the soil erosion rates per land use estimated by Rickson et al. (Developing a method to estimate the costs of soil erosion in high-risk Scottish catchments, 2019) in Scottish soils except in the case of pasture/grassland likely due to the pastures in this catchment being grass ley where periods of surface vegetation cover/root network absence are likely to have generated higher rates of erosion.

Conclusion

Selection of suitable erosion risk models can be improved by the combined use of two sediment origin techniques—erosion risk modelling and OC sediment fingerprinting. These methods could, ultimately, support the development of targeted sediment management strategies to maintain healthy soils within the EU and beyond.

Purpose

Land use changes influence soil porosity, soil water, and heat transport, which may alter freeze–thaw characteristics within the soil profile. However, the response to freeze–thaw process after long-term land use change in Northeast China is still unclear. Thus, this study explored the characteristics and dynamics of soil hydrothermal during the freeze–thaw process in Northeast China.

Materials and methods

The investigation focused on grassland and bare land that have undergone a long-term transformation from cropland. The soil temperature (ST) and soil water content (SWC) data during the freeze–thaw period were collected from 2016 to 2021. Characteristics of ST and SWC at 0–180 cm soil depth were carried out in two sites during the freeze–thaw period.

Results

It was found that soil in the bare land started to freeze and thaw earlier than that in the grassland. The bare land exhibited a 10.3–186.2% higher amplitude in ST at different depths and greater thermal efficiency between air and soil. In both study sites, the SWC showed a downward–stable–upward trend at different soil layers during the monitoring period. The migrated SWC in most soil layers decreased in two sites. The maximum amount of migrated water reached 2.11 and 5.14 mm in grassland and bare land, respectively. The SWC correlated exponentially with absolute temperature in two sites but decreased faster at 0–30 cm depths in the same temperature interval in bare land.

Conclusions

The soil in the grassland had more stable water and heat regulation ability than that in the bare land. Our results contribute to improving the comprehension of the relationship between water and heat in different land uses in seasonal frozen regions.

Background and Aim

Continuous monocropping with high nitrogen (N) fertilizer input substantially increases greenhouse gas (GHG) emissions in maize-based agroecosystems in the North China Plain (NCP). Introducing soybeans as an intercrop with maize and partially substituting urea with manure might effectively decrease GHG emissions. The aim of this study was to quantify the synergistic effect of maize-soybean intercropping and manure on soil GHG emissions.

Methods

A two-year field experiment with three cropping systems (maize monocrop, soybean monocrop, and maize-soybean intercrop) and four N treatments (control, urea, manure, and manure + urea) was carried out at Luancheng Agro-Ecosystem Experimental Station in the NCP. All N treatments, except the control, received 150 kg N ha⁻¹season⁻¹, either full dose as a basal application or two equal split applications.

Results

Results showed that all treatments contributed as a net source of N₂O and CO₂ fluxes but acted as a net sink of CH₄ fluxes. In both cropping seasons, intercrops had significantly lower N₂O emissions compared to monocropping systems, with 38% and 14% less emissions than maize monocrops in 2018 and 2019, respectively. Additionally, maize monocrops had significantly higher soil CO₂ emissions than other systems, while maize-soybean intercropping had 12% and 13% less CO₂ emissions than maize monocrops in 2018 and 2019, respectively. Among fertilized treatments, manure-treated soils emit notably lower N₂O fluxes compared to sole urea treatments. In this study, N₂O and CO₂ fluxes had a strong positive correlation with soil mineral N concentrations, soil temperature, and moisture content. Possibly due to more efficient N utilization, intercrop soils exhibited significantly lower NH₄⁺ and NO₃⁻ concentrations, leading to reduced nitrification and denitrification in the system, resulting in lower N₂O emissions from maize-soybean intercrops.

Conclusion

Our findings indicate that intercropping maize and soybean reduces soil NH₄⁺ and NO₃^– concentrations, as well as significantly decreasing soil N₂O and CO₂ emissions when compared to traditional maize monoculture. Therefore, due to its potential for reducing soil GHG emissions, maize-soybean intercropping can be regarded as an effective alternative cropping system to the prevailing maize-dominant monoculture to develop a sustainable agroecosystem in the NCP region.

Purpose

The objective of this study was to investigate the spatiotemporal distribution patterns of two common heavy metals, Cd and Pb, in urban rivers in plains, and analyze the impact of weak hydrodynamics on the transport of heavy metals, and guide their ecological risk assessments in these regions.

Materials and methods

Two field surveys (wet and dry seasons) were conducted at a total of 36 sites in the tributaries of Gehu Lake, located in a plain region in China. The European Community Bureau of Reference (BCR) extraction method was employed to analyze the components of Cd and Pb. The Nemello index and ecological risk index were calculated to assess their pollution levels and ecological risks.

Results and discussion

Cd primarily accumulated at the river mouths, while Pb was predominantly concentrated near the discharge sources. The mobile fractions of Cd were more likely to be released and migrate downstream, and thus the total Cd content demonstrated a significantly negative correlation with these mobile forms (p < 0.05). In contrast, although Pb had a greater proportion of mobile fractions, they were readily re-adsorbed onto particles and settled near the source. The source area displayed notable pollution with Pb, whereas the downstream river mouth area posed a high risk of Cd pollution.

Conclusions

The results indicated that the weak river hydrodynamics within plains amplify the impact of heavy metal mobility on their behaviors, producing a “screening effect” on Pb and Cd and resulting in distinct distribution patterns in sediments. These findings can guide the ecological risk assessment of heavy metals in aquatic ecosystems within plains.

Purpose

Most forms of Mercury (Hg) in soil have significant destructive effect on ecosystems and food safety because of enormous toxicity. The existing treatment methods have drawbacks such as high energy consumption, complex operation, long remediation cycle, and secondary pollution. Therefore, this study aims to develop a governance method with low energy consumption, simple operation, short execution cycle, and no secondary pollution.

Methods

A new system was set up to remove leachable Hg²⁺ from soil and its performance was evaluated. The system consisted of photochemical vapor generator (PVG, for Hg²⁺ removal), dielectric barrier discharge (DBD) trapping reactor (for collection of removed Hg⁰). In the presence of organic acids, leachable Hg²⁺ was converted to gaseous Hg⁰ by UV irradiation in the PVG, and transported to the DBD trap by air for collection of the removed Hg²⁺. Soil samples in PVG were taken into glass tubes at specific time and then added aqua regia, analyzed using ICP-MS after digested in a boiling water bath. The performance of DBD trap was analyzed by connecting with ICP-MS.

Results

This study achieved the removal of leachable Hg²⁺ from soil under the UV excitation, the subsequent conversion of escaped gaseous Hg⁰ to solid and enrichment in DBD trap. The factors affecting the efficiencies of photochemical reaction, transport and collection were carefully investigated. Under the optimized conditions, the removal efficiency of 2.00 mg L⁻¹ leachable Hg²⁺ in soil reached 95.0% within 1 h. Even in the presence of 15 interfering ions separately containing 50 mg L⁻¹, good remediation effects can still be achieved. The capture rate of gaseous Hg⁰ by DBD trap is close to 100%. The system can achieve Hg pollution control in 10 types of soil, demonstrating great promotion value.

Conclusions

This system utilizes PVG theory and DBD low-temperature plasma device to construct a safe, green, simple, and inexpensive method for removing leachable Hg²⁺ from soil.

Graphical Abstract

Purpose

The Cr(VI) removal capacity of green synthesized nano-zero-valent iron (GnZVI) using tea polyphenols (TPs) remains limited. To improve their application in contaminated soil and groundwater, the GnZVI was modified. This is necessary for in-situ remediation of heavy metal-contaminated soil and groundwater.

Materials and methods

The GnZVI-based carbon-composite (L&GnZVI@BC) was successfully constructed via the synergistic effect of L-cysteine modification and biochar support. The Cr(VI) removal capacity and transportability of L&GnZVI@BC were investigated in soil–water system by batch and column experiments.

Results and discussion

Comparison with two materials of GnZVI separately modified by L-cysteine (L-GnZVI) or supported by biochar (GnZVI@BC)), GnZVI composite with a combination modification of L-cysteine and biochar (L&GnZVI@BC, L-cysteine/biochar/Fe = 0.1/0.1/1) showed a much higher Cr(VI) removal capacity in soil and groundwater. The synergistic effect of the reduction of L-cysteine functional groups and the dispersibility of biochar support can enhance the transportability of L&GnZVI@BC in water-saturated sand media for more Cr(VI) adsorption at neutral pH; while that improved the soluble Fe(II) released from composite for the higher reduction of Cr(VI) into Cr(III) at acidic pH. Particularly, L&GnZVI@BC favored more Cr(III) generation during transport in porous media at lower pH when applied in the treatment of Cr(VI) contamination.

Conclusion

This research highlights that the modification of both L-cysteine and biochar was beneficial to sufficient transport and efficient remediation in Cr(VI)-contaminated soil and groundwater environments at different pH ranges. This study’s results provide a theoretical support for the practical application of nZVI composites in in-situ remediation of Cr(VI)-contaminated soil and groundwater via an environmental-friendly approach.

Purpose

Arsenic (As) and antimony (Sb) are toxic elements that usually co-occur in paddy soils due to their chemical similarity. Those elements are redox-sensitive and shift their species across the soil–water interface (SWI) where redox potentials change in every millimeter. In the real world, the distribution and speciation of As and Sb in soils are often influenced by external redox disturbance, but their temporospatial response remains poorly understood. This study aimed to address this gap by introducing external disturbance by adding nitrate into the overlying water.

Methods

Daily changes in the profile of As, Sb, iron (Fe), and sulfur (S) were measured using ICP-MS and the In-situ Porewater Iterative (IPI) sampler array.

Results

The results revealed a rapid formation of a sink for As and Fe at the oxic-anoxic transition zone within one day, persisting for at least 6 days and extending to ~ 30 mm below the SWI. Moreover, Sb was re-mobilized in the same area as the As and Fe sink, but the re-mobilized Sb zone was weaker, lasting only 4 days and extending to ~ 20 mm below the SWI. The presence of aqueous ferrous Fe below the transition zone facilitated the formation of Fe and As sink, while the presence of aqueous sulfide below the transition zone hindered the development of the Sb source.

Conclusion

These findings highlight the importance of carefully evaluating the impact of nitrate-based fertilizers or stabilization reagents when applied in As and Sb contaminated soils.

Purpose

Soil Phosphorous (P) availability is critical for many important ecological processes and oil-contaminated soil remediation. Despites a few studies confirmed directly effects of crude oil exposure on soil Phosphorus-cycling (P-cycling), how soil microbes and functional genes affiliated with P-cycling respond to crude oil remains poorly understood.

Methods

Here, metagenomics was implemented to analyze variations in the microbial community structure and potential functions associated with P transformation in the coastal soil contaminated by crude oil.

Results

Results showed a dramatic scarcity of P in the contaminated soil. Microbial inorganic P solubilization was governed by genes gcd and ppx in CK soil. In contrast, genes encoding C-P lyase (phnGHIJKLN) and alkaline phosphatase (phoA) displayed significantly greater abundances in the contaminated soils. Taxa annotation revealed that oil contamination altered the structure of the P-cycling microbial community with a bias towards those with oligotrophic characteristics. Specifically, the oil-contaminated soils were characterized by a stronger contribution of Proteobacteria, Ascomycota and Firmicutes. Overall, the strategy for acquiring P in the CK is inorganic P solubilization, while it converted to organic P mineralization under petroleum contamination. Soil N/P ratio played a key role in affecting P-cycling functional genes.

Conclusion

Our results highlighted that oil contamination with unbalanced N/P ratio greatly altered the microbial strategy for obtaining available P (AP) in soil. A better understanding of P-cycling mechanism exposed to oil contamination and further scientifically regulating it may set the stage for in-depth improvement for current bioremediation practices.