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22901. 题目: Changes in soil organic carbon and microbial community under varying straw incorporation strategies Straw return is a popular management strategy to improve soil organic carbon (SOC) and change soil microbial community structure in agro-ecosystems. In the North China plain, the average straw incorporation rate is 6000–10,000 kg ha−1, however, effective utilization of maize straw is difficult because of its large amount and volume. A four-year (2014–2017) experiment was conducted to investigate the effects of different forms of maize straw on subsoil SOC fractions and microbial communities under deep-buried (30–40 cm) management in a typic Agrosol in Liaohe plain. Six treatments were established: no straw (CK, 0 kg ha−1), whole straw (WS, 6000 kg ha−1), chopped straw (CS, 6000 kg ha−1), pelletized straw (PS, 6000 kg ha−1), straw biochar (BC, 2010 kg ha−1) and straw ash (SA, 960 kg ha−1). Soil organic carbon, dissolved organic carbon (DOC), microbial biomass carbon (MBC), and bacterial and fungal diversity and abundance were analysed by chemical and molecular methods. Compared with CK, the five treatments significantly increased the SOC pool by 1.4–4.8 % in the 0–20 cm soil depth and 3.2–14.2 % in the 20–40 cm depth, with the highest increase under CS. Both CS and WS significantly increased the DOC and MBC, with higher DOC/SOC and MBC/SOC ratios. Notably, straw incorporation showed greater effects on DOC and MBC and a higher increase in SOC fractions in the 20–40 cm depth. Principal component analysis and similarity analysis showed that the different forms of straw incorporation caused significant variations in microbial community structure in the subsoil layer. The BC and SA significantly increased the diversity of soil microorganisms, while CS and WS altered the relative abundance of the dominant bacterial phyla Acidobacteria, Nitrospirae, Proteobacteria, Verrucomicrobia and dominant fungal phyla Ascomycota, Morttierellomycota, Glomeromycota, which increased with increases in SOC fractions. Our results showed that regulation of C-related microbial abundance in the subsoil was more conducive to improving SOC fractions than simply improving soil microbial diversity. Since chopped straw significantly increased the abundance of C-related microflora and SOC fractions, it should be the optimal form of incorporation in deep-buried straw management. | |||||
22902. 题目: Humic acid’s (HA) role on NDMA formation from daminozide (DMNZD) during ozonation | |||||
22903. 题目: Impact of biochar addition on soil thermal properties: Modelling approach Little information is available on the effect of biochar on both measured and model-predicted soil thermal properties although they play a crucial role in the accumulation and transfer of heat and water through the soil. This study aimed at evaluation of the impact of biochar addition on soil thermal properties in field experiments conducted in China and Poland. The experimental data included biochar doses, soil texture, quartz and other minerals, bulk density, particle density, water content, air-filled porosity, and organic matter content. The data were then used to validate three models (analytic of de Vries, analytic of Zhao et al., and statistical-physical) and improve the predictability of the soil thermal properties. The biochar doses in the field experiments were from 4.5 to 40 Mg ha−1 and those in the modelling study ranged from 52 to 267 Mg ha−1. Pure biochar was used as well. The biochar additions caused a significant decrease in thermal conductivity and thermal diffusivity and exerted a less pronounced effect on the heat capacity. As shown by classic statistics and Bland-Altman plots, the agreement between the predicted and measured heat capacity of the Chinese soil was good and similar to the Zhao et al. and de Vries models. The best agreement between the statistical-physical model predicted and measured the thermal conductivity and diffusivity was obtained using the geometric mean of the native soil organic matter and biochar and after reduction of the quartz content in the sand fraction (2–0.05 mm) from 100 to 72%. The thermal diffusivity decreased with increasing biochar dose at comparable water contents and its characteristic maximum shifted towards higher water contents with increasing biochar dose. As thermal diffusivity enhances the smoothing of the temperature wave, these results imply that application of different biochar rates may help in regulation of soil temperature, which is an essential determinant of plant growth and soil processes and functions. | |||||
22904. 题目: Effects of biochar on methane emission from paddy soil: Focusing on DOM and microbial communities Biochar can be used as a soil amendment. However, it generally possesses unique physicochemical properties and complex organics, which could affect soil methanogenesis. In this study,straw-based biochars obtained at 300 °C (BC300), 500 °C (BC500) and 700 °C (BC700) were added to the paddy soil. Compared with the blank group, BC300 significantly increased paddy soil methane emissions by about 38%. However, this promoting effect gradually disappeared with the increase of pyrolysis temperature, and the inhibition even appeared in the BC700 group with the methane reduction by 18.2%. This might be related to the organics released from biochar. Van Krevelen (VK) diagram showed that the aromaticity of BC700 and BC500 were significantly higher than BC300. Fluorescent analysis further revealed that BC300 increased the amount of degradable fluorescent organics in the soil, which could provide more substrate for methane production. Moreover, as pyrolysis temperature increased, the fluorescent organics released were more likely to be non-biodegradable humus. In addition, it was shown that BC700 could adsorb some inherent organics in the soil, and thus reduced the total organic content and inhibited soil methane emissions. Microbial analysis showed that methanogenesis had a positive correlation with the abundance of syntrophic bacteria (e.g. Desulfobacca and Clostridium) which had ability to further degrade various types of organics and provided substrates to the methanogens. This article provides a deeper understanding regarding for the effects of biochar on methane emission from paddy soil in terms of organics and microbial perspectives. | |||||
22905. 题目: Application of Aurantiochytrium sp. L3W for food-processing wastewater treatment in combination with polyunsaturated fatty acids production for fish aquaculture Thraustochytrids such as Aurantiochytrium are heterotrophic microorganisms that are known to produce valuable polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In this study, Aurantiochytrium sp. strain L3W was used to remove dissolved organic carbon (DOC) and dissolved nitrogen (DN) from bean-boiling (BB) and miso-processing (MP) wastewater and to simultaneously produce PUFAs. Strain L3W removed 52% of the DOC and 37% of the DN from sterilized BB wastewater and produced biomass that contained 137 mg/g of fatty acids (FAs), including 96.2 mg/g of DHA. Growth of strain L3W in sterilized MP wastewater resulted in the production of biomass containing 147.6 mg/g of FAs, including 97.8 mg/g of DHA, and removal of 47% of the DOC and 55% of the DN from the wastewater. The biomass of strain L3W was digestible by the enzymes extracted from the stomachs of rainbow trout. These results confirmed the potential for use of strain L3W to remove DOC and DN from food processing wastewater and to produce PUFAs. This study also provided the first evidence that the raw biomass of Aurantiochytrium sp. can be used as a fish feed additive. | |||||
22906. 题目: Nickel aluminum layered double oxides modified magnetic biochar from waste corncob for efficient removal of acridine orange The objective of this work was to use corncob as raw material to prepare green reusable magnetic biochar for removal of dyes in wastewater. For this purpose, an environmentally friendly NiAl layered double oxides modified magnetic corncob biochar (MC1/NiAl-LDO) was obtained by pyrolysis of NiAl layered double hydroxides modified magnetic corncob biochar (MC1/NiAl-LDH) at 700 °C for 3 hours. The surface area of MC1/NiAl-LDO is552.62 m2∙g-1, which was much higher than that of MC1 (26.83 m2∙g-1). MC1/NiAl-LDO for acridine orange (AO) exhibited higher adsorption ability, the adsorption capacity of MC1/NiAl-LDO was increased by 90% compared with MC1. Adsorption experiments for AO on MC1/NiAl-LDO were carried with effect of pH, adsorption time, initial concentrations of AO and ionic strength. MC1/NiAl-LDO can be recycled nine times. The results exhibited that MC1/NiAl-LDO was a low cost adsorbent, providing good example for th agricultural waste recycling. | |||||
22907. 题目: Tree planting in organic soils does not result in net carbon sequestration on decadal timescales Tree planting is increasingly being proposed as a strategy to combat climate change through carbon (C) sequestration in tree biomass. However, total ecosystem C storage that includes soil organic C (SOC) must be considered to determine whether planting trees for climate change mitigation results in increased C storage. We show that planting two native tree species (Betula pubescens and Pinus sylvestris ), of widespread Eurasian distribution, onto heather (Calluna vulgaris ) moorland with podzolic and peaty podzolic soils in Scotland, did not lead to an increase in net ecosystem C stock 12 or 39 years after planting. Plots with trees had greater soil respiration and lower SOC in organic soil horizons than heather control plots. The decline in SOC cancelled out the increment in C stocks in tree biomass on decadal timescales. At all four experimental sites sampled, there was no net gain in ecosystem C stocks 12–39 years after afforestation—indeed we found a net ecosystem C loss in one of four sites with deciduous B. pubescens stands; no net gain in ecosystem C at three sites planted with B. pubescens ; and no net gain at additional stands of P. sylvestris . We hypothesize that altered mycorrhizal communities and autotrophic C inputs have led to positive 'priming' of soil organic matter, resulting in SOC loss, constraining the benefits of tree planting for ecosystem C sequestration. The results are of direct relevance to current policies, which promote tree planting on the assumption that this will increase net ecosystem C storage and contribute to climate change mitigation. Ecosystem‐level biogeochemistry and C fluxes must be better quantified and understood before we can be assured that large‐scale tree planting in regions with considerable pre‐existing SOC stocks will have the intended policy and climate change mitigation outcomes. | |||||
22908. 题目: Soil organic matter turnover depending on land use change: Coupling C/N ratios, δ13C and lignin biomarkers | |||||
22909. 题目: Delineating the continuum of dissolved organic matter in temperate river networks | |||||
22910. 题目: Successive biochar amendment improves soil productivity and aggregate microstructure of a red soil in a five-year wheat-millet rotation pot trial Soil structure affects soil physical, chemical, and microbial processes, and is a key factor influencing soil productivity and ecological functions. Biochar (BC) has a porous structure, large surface area and high organic carbon content and therefore has the potential to regulate soil structure and productivity. In the present study, we evaluated the effects of five-year successive seasonal application of BC at three different rates (0, 2.25 and 22.5 Mg ha−1) along with chemical fertilizer on soil microstructure and soil fertility of a red soil using a pot trial under wheat-millet crop rotations. We found continuous application of chemical fertilizers reduced soil fertility with progressive reductions in wheat and millet biomass yields over five rotation cycles. While BC amendment slowed the decline of soil productivity with their yield of grain and straw significantly higher than the treatment without BC. Application of high rate of BC (BC22.5) significantly improved soil fertility, with increased soil pH (3.29 units), cation exchangeable capacity (5.66 cmol kg−1), plant available water capacity (50.0%), soil organic carbon (306%), total nitrogen (182%), available phosphorus (241%), potassium (513%), calcium (245%) and magnesium (265%), and significantly decreased bulk density (0.52 g cm−3), soil exchange acidity (6.37 cmol kg−1) and exchange Al3+ concentrations (5.87 cmol kg−1) after five rotations. Specially, BC improved aggregate stability, intra-aggregate pore structure and water retention capacity, manifesting that BC might be an effective soil amendment to reduce soil erosion in this region. Our results indicated that long-term successive seasonal BC application could improve soil fertility and soil aggregation, and thus eliminate soil acidification and restore soil productivity in the acidic red soil. | |||||
22911. 题目: Rapid recovery of carbon cycle processes after the cessation of chronic nutrient enrichment Salt marshes provide critical ecosystem services including some of the highest rates of carbon storage on Earth. However, many salt marshes receive very high nutrient loads and there is a growing body of evidence indicating that this nutrient enrichment alters carbon cycle processes. While many restoration plans prioritize nutrient management in their efforts to conserve salt marsh ecosystems, there has been little empirical investigation of the capacity for carbon cycle processes to recover once nutrient loading is reduced. To address this, we compared rates of greenhouse gas fluxes (i.e., CO2 and methane) measured using static chambers, and soil organic matter decomposition, using both decomposition bags and the Tea Bag index, during the last two years of a long-term, ecosystem-scale nutrient enrichment experiment (2015–2016), as well as in the first two years post-enrichment (2017–2018). We found that both ecosystem respiration (Reco) and decomposition processes (i.e., rhizome decomposition and soil organic matter stabilization) were enhanced by nutrient enrichment, but returned to reference ecosystem levels within the first year following the cessation of nutrient enrichment, and were maintained in the second year. These results suggest that management practices intended to reduce nutrient loads in coastal systems may, in fact, allow for rapid recovery of carbon cycle processes, potentially restoring the high rates of carbon sequestration to these blue carbon ecosystems. | |||||
22912. 题目: Overseeding legumes in natural grasslands: Impacts on root biomass and soil organic matter of commercial farms Overseeding legumes in natural grasslands coupled with phosphorous fertilization are management practices oriented to increase forage production and quality, and to restore nutrient losses generated by livestock. Several studies show increases in forage due to this practice, but less is known about impacts on soil fertility and carbon sequestration. The objective of this study was to evaluate under real farm conditions changes in root C and N stocks and soil organic carbon (SOC) and nitrogen (SON) stocks in two different soil pools, the particulate organic matter (POM) and the mineral associated organic matter (MAOM), after the introduction in natural grasslands of a legume species, Lotus subbiflorus cv. El Rincón, accompanied with phosphorous fertilization. We also evaluated changes in the natural abundance of 15N and 13C in soils and roots to understand changes in N fixation and species composition. We selected 12 adjacent paddocks of natural grasslands (NG) and natural grasslands overseeded with legumes and fertilized with phosphorous (NGLP) located in commercial farms in Uruguay. We found that overseeding legumes increased root C and N stocks and SOC and SON stocks in some farms but decreased them in others. On average, no significant differences arose between NGLP and NG paddocks in total stocks of 0–30 cm depth. However, higher C stocks were observed in POM of NGLP paddocks in 0–5 cm layer and lower contents in 5–10 cm layer indicating a change in the vertical distribution of C in POM. Changes in δ15N suggest that atmospheric N is being fixed by legumes in NGLP paddocks, but not translated into more N or C stocks in the MAOM fraction, probably due to high N losses promoted by cattle grazing. Our work suggests that carbon sequestration can be achieved after legumes introduction in grazed natural grasslands but will depend on grazing management practices. | |||||
22913. 题目: Agrochemical leaching reduction in biochar‐amended tropical soils of Belize The aim of this study was to determine the effects of biochar addition on agrochemical leaching in tropical soils of Belize. Biochars were produced from mixed softwood, rice husk and miscanthus straw, each pyrolysed at 700°C. Loam, sandy silt loam, and clay loam tropical soils were amended with 0, 1, 2.5 and 5% (w/w) biochar to determine atrazine, diuron, enrofloxacine, oxytetracycline and tetracycline absorption in batch studies following OECD 106 guidelines. FOCUS groundwater modelling was performed with the results of the batch‐sorption study and alterations to the soil profiles to explore the effect of biochar amendment on the leaching of atrazine in a risk assessment context. Results showed that agrochemical sorption was higher in biochar amended soils than soils without biochar amendment. Soil organic matter content and biochar amendment contributed to the agrochemical sorption increase in soils. The FOCUS modelling showed a significant reduction in Predicted Environmental Concentration in groundwater (PECgw) of atrazine when biochar was amended to the soil. However, a trade‐off was identified between the sorptive capacity of the biochar and the changes in hydrology in the soil as a result of the biochar incorporation. The amendment of Belizean tropical soils with rice husk biochar was shown to be an effective method to reduce the leaching of the selected agrochemicals, though the widespread implementation should be conducted carefully, taking account of the potential trade‐offs with biochar use identified in our modelling. | |||||
22914. 题目: Molecular dynamics of foliar litter and dissolved organic matter during the decomposition process | |||||
22915. 题目: Effects of Storm Events on Phosphorus Concentrations in a Forested New England Stream | |||||
22916. 题目: Reactivity of Pyrogenic Carbonaceous Matter (PCM) in mediating environmental reactions: Current knowledge and future trends | |||||
22917. 题目: Incorporation of biochar into semi-interpenetrating polymer networks through graft co-polymerization for the synthesis of new slow-release fertilizers Modern agriculture is strongly calling for the development of environment-friendly slow-release fertilizers (SRFs) with high water retention. In this study, a new biochar embedded-Semi-IPN based SRF is developed by the incorporation of biochar into semi-interpenetrating polymer networks (Semi-IPN) via grafted co-polymerization, which holds great potential to combine the advantages of biochar and Semi-IPN when they are used in SRFs. The results show that the as-prepared biochar embedded-Semi-IPN based SRF (BiBe-SRF) exhibits a high water-retention capacity with the value of 73.50% after 25 days, which far outstrips that of Semi-IPN based SRF without the incorporation of biochar. BiBe-SRF also has a better slow-release performance of nutrients than the Semi-IPN based SRF. The release ratios of N, P and K from Semi-IPN based SRF within 30 days reach in the range of 95.5% to 100.0%, but they are less than 80.0% for BiBe-SRF. The degradation ratio for BiBe-SRF is 62.63% after 90 days' degradation experiment which is higher than Semi-IPN based SRF, suggesting that the presence of biochar significantly improves the degradability of BiBe-SRF. Pot experiments reveal that pepper seedlings fertilized by BiBe-SRF grow better than those fertilized by Semi-IPN based SRFs, which further highlights its great potentials for the practical application. The mechanism study suggests that the existence of biochar is beneficial for the formation of improved porous structure and generation of abundant cross-linking points within BiBe-SRF, and it is also responsible for the high hydrophilicity of BiBe-SRF. Overall, this study demonstrates a new route for the development of environment-friendly SRFs with high water retention. | |||||
22918. 题目: A comparison of methods for the extraction of dissolved organic matter from freshwaters Studies of dissolved organic matter (DOM) composition have used several different methods to concentrate and extract the DOM from fresh water, but the impact of these methods on the composition of the DOM is relatively unknown, as very few studies use more than one method to compare results. The aim of this study was to use several methods, frequently used in the scientific literature, to concentrate and extract DOM from fresh water and compare the elemental and functional group composition of the extracted DOM. In addition, the cost, in terms of money, resources and time, were assessed for each method. The results showed that the elemental and functional group composition of the extracted DOM varied between methods significantly. The methods that yielded the most similar and reproducible DOM results were rotary evaporation, dry-down at 60 °C and freeze-drying. Although each of these methods required a relatively expensive piece of laboratory equipment, this was a 'one-off' cost, and consumables and time per sample were relatively low. This study highlights the dangers of comparing DOM data from different studies when the DOM has been extracted via different methods. In future, it is recommended that studies of DOM composition report their methods of extraction clearly and consistently, ideally using one (or more) of the methods showing reliable results here. | |||||
22919. 题目: Enhanced cometabolism of benzo(a)anthracene by the lignin monomer vanillate is related to structural and functional responses of the soil microbiome Lignin is a natural polymer composed of phenolic units. The structural similarity between lignin monomers and recalcitrant aromatic pollutants raises the possibility of their cometabolism by soil microorganisms. Here, we explored the links between polycyclic aromatic hydrocarbon (PAH) degradation and microbiome responses in soil microcosms amended with lignin or one of its phenolic units, vanillate, by coupled amplicon and metagenomic shotgun sequencing. The transformation of the four-ring model PAH benzo(a)anthracene (BaA) was monitored by using a radiolabelled tracer. The results demonstrated that vanillate significantly promoted 14CO2 production during incubation, suggesting activation of BaA biodegradation in the soil microcosms. Lignin changed the fate of BaA mainly by increasing its adsorption to soil organic matter. In contrast to the control microcosms, the mineralization and formation of nonextractable residue (NER) from BaA in the presence of vanillate were sensitive to the fungicide cycloheximide. Lignin and vanillate consistently enriched bacterial methyl utilization and aromatic ring cleavage genes at the two sampling times, which, however, did not translate to BaA mineralization. The distinct responses of the fungal community to vanillate as well as the coupled cycloheximide-induced inhibition of BaA mineralization and 18S rRNA gene abundance suggest an essential contribution of fungi to BaA biodegradation in the vanillate-amended microcosms. Overall, these findings reveal a cometabolic mechanism between vanillate and PAHs, which contributed to the detoxification of BaA in the soil. This study also provides a scientific basis for the bioremediation of PAH-contaminated soil by modulating the soil microbiome with phenolic monomers of lignin. | |||||
22920. 题目: Using Fe chemistry to predict Fe uptake rates for natural plankton assemblages from the Southern Ocean A recent study using Fe-limited phytoplankton strains, showed that iron (Fe) uptake rates normalized by cellular surface area were best related to dissolved iron (dFe) concentrations as the inorganic Fe (Fe') supply rates were not sufficient to satisfy the Fe biological demand. Short-term (24 h) shipboard incubations with the in-situ phytoplankton community were used to measure Fe uptake rates that were normalized per biomass (as particulate organic carbon, POC). Fe uptake rates measured following 55FeCl3 additions (0.05 to 0.9 nM) were fitted to different Fe pools (dFe, Felabile, and Fe') using the Michaelis-Menten equation. Data showed a similar high conditional stability constant for biological transporters across all sites and phytoplankton size classes, with only a 2-fold variation in the concentrations of cellular transporters. These observations are in line with previous reports that eukaryotic phytoplankton takes up Fe close to the limit imposed by transporters cellular density and uses similar high-affinity Fe uptake systems. To further explore the link between Fe uptake rates and Fe chemistry, we also studied the effect of additions of preequilibrated with different Fe-binding ligands (L) including: the siderophore desferrioxamine B, two carbohydrates (glucuronic acid and carrageenan) and two different bacterial exopolycarbohydrates (L6 and L22, referred as EPS). For all stations, phytoplankton were able to acquire Fe associated to DFB as previously reported, however, different Fe:L ratios prevent quantitative comparison with previous studies. Iron bound to carbohydrates, glucuronic acid, carrageenan and EPS could enhance or decrease Fe uptake rates in comparison to equimolar FeCl3 addition. These results illustrate that the effect of such L on Fe uptake rates will depend on the in-situ plankton community and their chemical structure. The variation of the Fe' concentrations was able to explain up to 69% of the Fe uptake rates observed for the Antarctic communities. This relationship with Fe' was related to the fact that the Fe' maximal supply, due to the dissociation of FeL, was enough to satisfy the Fe uptakes rates. Calculations using previous reports in contrasted regions of the Southern Ocean, showed that Fe' maximal supply was greater than Fe uptake rates measured in 80% of the cases. Moreover, considering photo- and redox-chemistry as well as kinetical situations prevailing in the field, Fe' should not be overlooked as a pool able to satisfy most of the Fe biological demand. Finally, this study points towards the potential that the GEOTRACES Fe chemical speciation data represent to explore Fe uptake rates at a larger scale in this vast Fe-limited oceanic region. | |||||
