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22781. 题目: Linear two-pool models are insufficient to infer soil organic matter decomposition temperature sensitivity from incubations | |||||
22782. 题目: Iron and iron-bound phosphate accumulate in surface soils of ice-wedge polygons in arctic tundra | |||||
22783. 题目: Assessment of dissolved organic carbon and iron effects on water color between a forest and pasture-dominated fine-scale catchment in a Central Appalachian region, West Virginia | |||||
22784. 题目: Black liquor as biomass feedstock to prepare zero-valent iron embedded biochar with red mud for Cr(VI) removal: Mechanisms insights and engineering practicality Black liquor (BL) is an agro-industrial residue with high number of lignocellulosic components which could be recognized as a biomass feedstock. In this work, BL coupled with red mud (RM), were applied to prepare cost-effective zero-valent iron (ZVI) embedded in biochar. The oligomers in BL acted as reductants for RM to generate ZVI, while the organic components could be converted into biochar during pyrolysis. The RM/BL demonstrated excellent performance in the removal of Cr(VI) (349.5 mg/g), as the mechanisms were reduction and adsorption. The fixed-bed column study was conducted and 1.7 L simulated wastewater could be treated by 1.0 g RM/BL. After reaction, 95.5%±0.8% and 82.5%±3.2% Cr-loaded adsorbents could be recovered by an external magnet for batch and fixed-bed experiments, respectively. All these results shed light on valorizing these two widespread agro-industrial byproducts, and bridged the knowledge gap between magnetic bio-adsorbent preparation and its industrial practicality on wastewater purification. | |||||
22785. 题目: Evaluating soil organic carbon stock changes induced by no-tillage based on fixed depth and equivalent soil mass approaches It is controversial whether no tillage (NT) should be regarded an effective agro-ecosystem management to increase soil organic carbon (SOC). Some studies suggest NT leads to a notable accumulation of SOC stock across the whole sampling profile over the long-term, whereas other studies argue that the effect of duration on SOC stock increase is limited. Similar controversy is common with respect to the role of climatic conditions in SOC changes. In addition, despite the gradual recognition of the importance of equivalent soil mass (ESM) compared to fixed depth (FD) approach, in terms of SOC stock evaluation, the ESM approach mainly focuses on the direct impact of bulk density but ignores the potential indirect effect on SOC concentration. To further understand the SOC sequestration mechanisms under NT, responses of SOC stock after the adoption of NT were investigated based on FD and ESM approaches. The results showed that NT significantly changed the SOC stock distribution in different soil depths according to both FD and ESM, but no significant changes were observed when soil sampling deeper than 50 cm. Notably, the results illustrated that the use of FD overestimated the SOC stock in the soil surface due to the increased bulk density under NT, but underestimated the SOC stock in 30–70 cm soil layers compared to ESM. Consequently, the overestimate of SOC based on FD may not be as high as previously assumed across the sampling depth. Mean annual temperature and mean annual rainfall did not lead to any significant changes in SOC stock of the overall soil profile or different layers, indicating the limited impacts of climatic conditions on carbon sequestration after the adoption of NT. Long-term NT resulted in a significant accumulation in SOC stock in the top 5 cm of the surface soil, but SOC stock changes with time in soil layers deeper than 5 cm was not significant in both FD and ESM approaches. The overall changes in SOC stock as time increased were not significant across the whole profile based on FD, but was weakly significant based on ESM. The results illustrate that using the overall SOC stock change of the whole sampling soil profile deeper than 30 cm masks the beneficial change in SOC stock in the 0–5 cm soil over long-term adoption of NT. The biased interpretation of depth factor is the main reason that fuels the debate over whether long-term NT is beneficial for the accumulation of SOC stock, and hence must be properly considered. Overall, the data illustrate that the depth factor is not only important in terms of assessing total SOC stock changes under NT, but also critical when evaluating the effectiveness of FD and ESM, as well as the impact of experimental duration on SOC increase. The depth factor should thus be comprehensively considered in SOC stock assessment and more field experiments sampling to deeper depth are urgently needed to clarify whether NT is beneficial for SOC sequestration and climate mitigation. | |||||
22786. 题目: Afforestation changes soil organic carbon stocks on sloping land: The role of previous land cover and tree type Afforestation contributes to soil organic carbon (SOC) sequestration and the restoration of degraded soil. However, the changes in SOC stock following afforestation on sloping land are poorly understood. Here we conduct a quantitative review that synthesizes 239 observations from 31 studies to evaluate the effects of slope gradients on the changes in SOC stock in three soil layers (0–20 cm, 20–40 cm and 40–60 cm) following afforestation, considering previous land cover (cropland and grassland) and tree type (broadleaf and conifer). In the topsoil layer, slope gradient has a significant effect on the changes in SOC stock: slope gradient positively relates to SOC stock change and significantly predicts the SOC stock change after controlling for temperature, precipitation, stand age, and initial SOC stock. Soil gradient explains 12.5% of the variance. We find a significant decrease in SOC stock after the afforestation of gentle slopes with a gradient lower than 10% but a significant increase in SOC stock on slopes with a gradient higher than 30%. Afforestation on sloping cropland results in an increase in SOC stock, especially in the upper soil, while afforestation on grassland results in an increase in SOC stocks only on very steep slopes (gradient >60%). Tree type has a limited effect on changes in SOC after afforestation on sloping land. However, conifers show a greater SOC sequestration potential in deeper soils and on steep slopes with a gradient higher than 60%, while broadleaf trees sequester more SOC in topsoil and on slopes with a gradient of 30–60%. The present study suggests that to increase SOC sequestration, priority should be given to afforestation with conifers on steep cropland. | |||||
22787. 题目: Nitrogen input in different chemical forms and levels stimulates soil organic carbon decomposition in a coastal wetland Nitrogen (N) input significantly regulates soil organic carbon (SOC) storage in N-limited ecosystems. However, the regulatory direction, magnitude, and mechanisms of SOC decomposition under continuous N input in different chemical forms and levels in coastal wetlands are poorly understood. We investigated the impact of 6-year N input in a coastal wetland of the Yellow River Delta, examining the effects on plant growth and soil properties for different chemical forms (NH: ammonium, NO: nitrate, and NN: ammonium-nitrate) and levels (5 g N m−2 yr−1, 10 g N m−2 yr−1, and 20 g N m−2 yr−1) at two depths (0–10 cm, 10–20 cm). We also set up an incubation experiment with N-treated soil to investigate SOC decomposition under different treatments. Six-year N input led to overall increases in the soil nutrients (i.e., total N, ammonium-N (NH4+-N), and nitrite-N (NO3—N)), stimulation of plant growth (i.e., plant biomass, height, and density), enhancement of soil C storage (i.e., total carbon, SOC, dissolved organic carbon, and microbial biomass carbon), and decreases in the electrical conductivity (EC). The incubation experiment revealed that N input-induced SOC decomposition stimulation is N-form dependent; NO input was the strongest stimulator of decomposition, when compared to NH and NN input. The stimulation differences among the dominant-form N inputs increased with increasing N supply levels. Structural equation modeling (SEM) analysis indicated that the stimulation of SOC decomposition by N input was associated with N-related changes in the soil nutrients, vegetation, soil C storage, and soil environment. Together, these results aid the evaluation of soil C cycling under future N deposition scenarios in coastal wetlands. | |||||
22788. 题目: Exploration of fulvic acid as a functional excipient in line with the regulatory requirement Fulvic acid, a humic substance often considered as a geopolymer, extracted from different natural resources like Shilajit, Peat, dissolved organic matters, etc. There are several reports of its pharmacological properties and its potential as pharmaceutical excipients. So, we have devised a project to strengthen its claim as a functional excipient. For the given project, lyophilized sample of a dietary supplement product (an aqueous solution of peat derived Fulvic acid) was used. The selected studies were typical for an excipient development like physicochemical properties, flow properties, compatibility with other excipient and stability studies, non-clinical safety studies (acute toxicity in mice whereas sub-acute toxicity in rats) and some functionality tests. We also suggest its ability to form co-crystal with natural phytochemicals. Our group has already reported its ability to enhance solubility and or bioavailability of different BCS class II drugs. Henceforth, we can propose that Fulvic acid appears a good candidate to be further explored as a functional excipient and should be evaluated as per the remaining recommendations of IPEC, USFDA, and USP. | |||||
22789. 题目: Machine learning in space and time for modelling soil organic carbon change Spatially resolved estimates of change in soil organic carbon (SOC) stocks are necessary for supporting national and international policies aimed at achieving land degradation neutrality and climate change mitigation. In this work we report on the development, implementation and application of a data‐driven, statistical method for mapping SOC stocks in space and time, using Argentina as a pilot. We used Quantile Regression Forest machine‐learning to predict annual SOC stock at 0–30 cm depth at 250 m resolution for Argentina between 1982 and 2017. The model was calibrated using over 5,000 SOC stock values from the 36‐year time period and 35 environmental covariates. We pre‐processed NDVI dynamic covariates using a temporal low‐pass filter to allow the SOC stock for a given year to depend on the NDVI of the current as well as preceding years. Predictions had modest temporal variation with an average decrease for the entire country from 2.55 kg C m−2 to 2.48 kg C m−2 over the 36‐year period (equivalent to a decline of 211 Gg C, 3.0% of the total 0–30 cm SOC stock in Argentina). The Pampa region had a larger estimated SOC stock decrease from 4.62 kg C m−2 to 4.34 kg C m−2 (5.9%) during the same period. For the 2001–2015 period, predicted temporal variation was 7‐fold larger than that obtained using the Tier 1 approach of the IPCC and UNCCD. Prediction uncertainties turned out to be substantial, mainly due to the limited number and poor spatial and temporal distribution of the calibration data, and the limited explanatory power of the covariates. Cross‐validation confirmed that SOC stock prediction accuracy was limited, with a Mean Error of 0.03 kg C m−2 and a Root Mean Squared Error of 2.04 kg C m−2. In spite of the large uncertainties, this work showed that machine learning methods can be used for space–time SOC mapping and may yield valuable information to land managers and policy makers, provided that SOC observation density in space and time is sufficiently large. This article is protected by copyright. All rights reserved. | |||||
22790. 题目: Climate variability in Mediterranean ecosystems is reflected by soil organic matter pyrolytic fingerprint Soil organic matter (SOM) is a major component of the biogeochemical cycle contributing to soil general properties and conservation. The progressive depletion of the SOM in Mediterranean ecosystems results in an increased advance of desertification. The SOM not only plays a crucial role in soil resilience, but also represents a repository of environmental information on soil forming factors in particular climatic constraints. In this research, analytical pyrolysis (Py-GC/MS) is used to study SOM composition in 30 soils under contrasting bioclimatic scenarios as defined by the classical Emberger (Q) index. Partial least squares (PLS) regression using the major pyrolysis compounds as descriptors allowed to predict (P < 0.05) Q indexes, and provide molecular proxies of climatic variability effects on SOM composition. In addition, pyrolytic compound assemblages from soils developed under extreme climatic conditions were compared using a graphical approach based on surface density plots built from the major 193 pyrolysis compounds represented in the plane defined by their H/C and O/C atomic ratios. The differences between the proportions of the individual pyrolysis compounds in terms of the bioclimatic scenarios were also illustrated by a simulation of SOM molecular composition under extreme conditions of aridity or wetness. Although no cause-to-effect is inferred, the results show that SOM composition retains environmental information on the Q index. This is mainly related with the total abundances of methoxyphenols and alkylbenzene compounds, suggesting that the degree of transformation of SOM could be related with the variable accumulation of microbial and plant biomass controlled by climatic factors which is a potential field for future research. | |||||
22791. 题目: Daily denitrification rates in floodplains under contrasting pedo-climatic and anthropogenic contexts: modelling at the watershed scale | |||||
22792. 题目: Physical attributes and organic carbon in soils under natural and anthropogenic environments in the South Amazon region | |||||
22793. 题目: Impacts of two East Asian atmospheric circulation modes on Black Carbon aerosol over the Tibetan Plateau in winter Light‐absorbing particles over the Tibetan Plateau (TP) can accelerate glacial melt, thus causing a series of serious environmental and social problems. Previous studies mainly focus on seasonal transport of aerosols over the TP, while the potential factors influencing the subseasonal variation in airborne black carbon (BC) is almost ignored. In this study, the Weather Research and Forecasting coupled with chemistry (WRF‐Chem) model and multiple observations are used to investigate the impacts of East Asian atmospheric circulation on BC aerosol over the TP in winter. Results show that the weakness of westerly wind over northern TP, acceleration of westerly wind over southern TP and eastward shift of East Asia major trough, are responsible for the high BC concentration over east slope of the TP. In this circumstance, more BC from northern India can be transported to eastern TP and the south slopes of the TP by the enhanced westerly wind. The intensified southwesterly wind over eastern TP brings more BC from the Sichuan Basin to northeastern TP. The BC can also penetrate to eastern TP in planetary boundary layer. Subsequently, the weakened westerly wind over northern TP and positive anomalous updrafts over east slope of the TP support the accumulation and uplift of BC. Another circulation mode is opposite to the pattern above and results in low BC concentration over the TP. These two circulation modes are possibly associated with the low‐level meridional temperature anomaly over East Asia which modulates the upper‐level atmospheric circulation through the transient eddy feedback. | |||||
22794. 题目: Soil quality and carbon sequestration under conservation agriculture with balanced nutrition in intensive cereal-based system Conventional tillage practices and imbalanced use of inorganic fertilizers is well known to result in poor soil health. Alternative tillage and precision nutrient management are important strategies for tackling the issues of soil health deterioration, particularly in cereal-based intensive cropping systems. Therefore, we conducted a 4-year study with the objective of (a) monitoring the changes in soil physical, biological and chemical properties and crop productivity, (b) development of soil quality index-SQI, and monitor its' changes against system productivity as management goal, and (c) studying the changes in soil organic carbon-SOC in relation to annual C input. The experiment was laid out in a split-plot design with 3-tillage practices [zero tillage-ZT; permanent beds-PB; and conventional tillage-CT] and 4-nutrient management strategies [Control (unfertilized), farmers' fertilizer practice-FFP, recommended fertilizers doses-Ad-hoc and site specific nutrient management-SSNM] under a continuous maize (Zea mays L.) - wheat (Triticum aestivum L.)- mungbean (Vigna radiata L. Wilczek) rotation in a sandy loam soil (Typic Haplustept) of north-western Indo-Gangetic plains (NW-IGP) of India. The ZT/PB with SSNM/Ad-hoc nutrient management resulted in higher values of a) physical parameters viz., water stable aggregates >250 μm, saturated hydraulic conductivity (Ksat) and mean weight diameter-MWD, b) chemical parameters viz., SOC, available N, P, and K, and c) biological parameters viz., microbial biomass carbon and enzyme activities (fluorescein diacetate hydrolase, dehydrogenase, ß-glucosidase and alkaline phosphatase) compared with CT and unfertilized treatments. The CA practices recorded an increase in WSA (12–21%), MWD (14–29%), and Ksat (11–14%) compared with CT at the 0-0.15 m and 0.15–0.30 m soil depths, respectively. The PB-SSNM registered (44.1%) higher SOC content as compared to CT-unfertilized plots. Values for MBC, FDA and βGA declined in the order SSNM=Ad-hoc>FFP > Control. While, the DHA declined in the order SSNM>Ad-hoc=FFP > Control. Principal component analysis included MWD, SOC and available K in the minimum data set (MDS) as the soil quality indicators. Adoption of PB/ZT resulted ∼22.5% higher SQI compared with CT. The SSNM plots improved SQI by ∼19.3% and ∼5.3% over unfertilized and FFP. The SSNM based CA practices attained a significantly higher annual C sequestration rate than other treatments. Therefore, adoption of CA with SSNM and Ad-hoc nutrient management in intensive cereal based systems of NW-IGP is essential for improving nutrient cycling, soil quality, crop productivity and C-sequestration potential. | |||||
22795. 题目: Spatial variation of soil carbon stability in sugarcane crops, central-south of Brazil The decay constant (k) of soil organic carbon can be used in the decision making of soil management practices and it is an indicative of the spatial variability of soil carbon stability, which depends on the interactions of physical, chemical and biological factors within agroecossystem. The aim of this work was to determine the spatial variability structure of soil carbon losses, expressed by the factor k, and its relationship with the soil attributes in sugarcane crops, in the central-south region of Brazil. The experiments were carried out in areas of commercial sugarcane plantations, in the cities of Motuca (MOT), Guariba (GUA) and Pradópolis - SP (PAD), in the State of São Paulo, and Aparecida do Taboado (APT), in Mato Grosso do Sul. The measurements of soil CO2 emission (FCO2) were recorded in the areas of study by the LI-COR system (LI-8100). The multivariate approach indicated that the two principal components (PC1 and PC2) explained around 55% to 68% of the total variability contained in the dataset in the areas studied, respectively. The soil physical attributes showed discriminatory power within PC1 and indicated a contrast between air-filled pore space and soil water content. In PC2, the chemical attributes indicated a joint action of the cations exchange capacity and available phosphorous content. PAD and APT areas presented negative and significant spatial patterns between factor k and PC1. For the spatial patterns between k and PC2 in GUA and APT, values with negative and significant correlations occurred. The results indicate that the soil carbon accumulation potential presented high spatial variability on a small scale; thus, in the same area, there were changes in the spatial patterns of factor k, presenting regions with potential accumulations or sources of carbon in the system of cultivation of raw cane, being able to be carried out the specific management in the same productive area. | |||||
22796. 题目: Biotic and abiotic nitrogen immobilization in soil incorporated with crop residue Incorporating crop residue favors biotic and abiotic nitrogen (N) immobilization, which can effectively conserve active N in soil. Here we summarize the occurrence characteristics of biotic and abiotic N immobilization and affecting factors, and then identify a general pattern of the relative importance of the two processes in soil incorporated with crop residue. When microorganisms decompose crop residue for a source of energy and carbon (C) to support their metabolism, they need N to build cellular components, resulting in N immobilization in biomass. Alternatively, N can be incorporated into soil organic matter (SOM) through the following known mechanisms: ammonium (NH4+) fixation by clay minerals, condensation of ammonia (NH3) with phenol or quinone rings, and nitrosation of nitrite (NO2-) with phenolic compounds. The biotic and abiotic contribution to N immobilization is significantly controlled by soil properties and crop residual quality. When a large fraction of C is in the form of labile organic compounds, biotic N immobilization may be important. In contrast, high fraction of lignin-derived phenolic compounds or other recalcitrant organic compounds facilitates abiotic N immobilization. In the N-limited soil, the increase in N availability contributes to microbial activity, which would stimulate biotic processes. However, when microbial metabolism switches from N-limited to C-limited due to the increase in N availability, abiotic processes become important. Abiotic processes even predominate over biotic processes under N-enriched conditions. The relative roles of biotic or abiotic N immobilization in soil incorporated with crop residue are dependent on the availability of C relative to N and soil N availability. Carbon and N availability in turn is related to their forms. Moreover, N availability is affected by soil pH. The mechanisms by which N is immobilized determine the fate of immobilized N and are of vital importance for the management of N availability and losses through combining N fertilizer with crop residue. More investigation is necessary to quantify the contribution of biotic and abiotic processes during the decomposition of crop residue and to determine the factors affecting N immobilization in the field. | |||||
22797. 题目: Biochar induced negative priming effect on soil organic carbon mineralisation by changing the microbial community structure across plant growth stages | |||||
22798. 题目: Soil microbes of an urban remnant riparian zone have greater potential for N removal than a degraded riparian zone Soils in the riparian zone, the interface between terrestrial and aquatic ecosystems, may decrease anthropogenic nitrogen (N) loads to streams through microbial transformations (e.g., denitrification). However, the ecological functioning of riparian zones is often compromised due to degraded conditions (e.g. vegetation clearing). Here we compare the efficacy of an urban remnant and a cleared riparian zone for supporting a putative denitrifying microbial community using 16S rRNA sequencing and qPCR of archaeal and bacterial nitrogen cycling genes. Although we had no direct measure of denitrification rates, we found clear patterns in the microbial communities between the sites. Greater abundance of N‐cycling genes was predicted by greater soil ammonium (N‐NH4), organic phosphorus, and C:N. At the remnant site, we found positive correlations between microbial community composition, which was dominated by putative N oxidisers (Nitrosomonadaceae, Nitrospiraceae and Nitrosotaleaceae), and abundance of AOA, nirS , nirK and nosZ , whereas the cleared site had lower abundance of N‐oxidisers and N cycling genes. These results were especially profound for the remnant riparian fringe, which suggests that this region maintains suitable soil conditions (via diverse vegetation structure and periodic saturation) to support putative N cyclers; which could amount to higher potential for N removal. This article is protected by copyright. All rights reserved. | |||||
22799. 题目: Management of table olive processing wastewater by an osmotic membrane bioreactor process The management of fermentation brines from the table olive processing is very complex due to its characteristics: high salinity and high organic matter concentration including phenolic compounds, which behave as slow degradable compounds when a biological process is performed. In this work, the management of these effluents by an osmotic membrane bioreactor has been assessed. This technique combines a biological reactor with forward osmosis membranes. For the study, a laboratory plant consisting of 1 L reactor and a forward osmosis module equipped with a membrane of 42 cm2 of active surface has been used. Fermentation brine from table olive processing was fed to the system both as draw solution to set out the driving force for the membrane process and as a part of the feed to the reactor, mixing it with municipal wastewater. The experiments were carried out at a constant feed to microorganism ratio of 0.4 g COD·g SS−1·d−1. Results indicated that the hypersaline effluent was able to produce the needed driving force by the process. Permeate fluxes ranged between 1 and 1.5 L·m−2·h−1 after the flux decay of the first operation days. Concerning the biological reaction, it has to be highlighted that phenols were eliminated after 24 days. Until that day, the biological process was jeopardized due to the quick increase of the conductivity in the reactor (ranging between 30 and 35 mS·cm−1), which was caused not only by the salinity of the influent but also by the reverse salt flux phenomenon. Soluble microbial products and extracted extracellular polymeric substances also increased in the reactor during the start-up. | |||||
22800. 题目: Rosmarinic acid enhanced Fe(III)-mediated Fenton oxidation removal of organic pollutants at near neutral pH In this study, we reported that the presence of rosemary acid (RA) could strongly enhance the Fe(III)-mediated Fenton oxidation of 2,4-DCP as the model contaminant at near neutral pH. This enhancement was verified by the strong chelating and reducing ability of RA, which could prevent ion precipitation and accelerate the Fe3+/Fe2+ cycle. Radical quenching experiments and electron paramagnetic resonance confirmed the existence and roles of hydroxyl radicals in the Fe3+/RA/H2O2 system. Lot size optimized experiments were executed to achieve efficient 2,4-DCP degradation (99.93%) under the optimum conditions of 100 μmol/L Fe3+, 100 μmol l/L RA and 8 mmol/L H2O2 within 60 min. In addition, co-existing metal ions, inorganic anions and natural organic matters were proved that they could inhibit removal efficiency and rate at varying degrees. Total organic carbon and chloride ion measurements were employed to probe the mineralization of organic matters (including RA and 2,4-DCP). This study provides a new modified Fenton system to enhance the oxidation removal of refractory organics in water and will enrich the understanding on effective H2O2 activation at neutral pH. | |||||
