421. 题目: Chemical properties of soil determines the persistence and bioavailability of polycyclic aromatic hydrocarbons in sewage sludge- or sewage sludge/biomass-derived biochar-amended soils
In this study the persistence (organic solvent extractable) and bioavailability (freely dissolved) of polycyclic aromatic hydrocarbons (PAHs) in soils with various properties amended with sewage sludge (BCSSL)- or sewage sludge/biomass (BCSSLW)-derived biochars was examined. Biochars produced at 600 °C were applied to soils (acidic, neutral, or alkaline) at a dose of 2% and subsequently incubated for 180 days. Here, the use of biochars regarding the soil's type was examined for the first time. Depending on the soil pH and the feedstock, the content of sum of 16 organic solvent extractable PAHs was found to decrease from 7.5 to 37% (soil + BCSSL) and from 24 to 40% (soil + BCSSLW). The decrease in the content of sum of 16 freely dissolved PAHs ranged from 18 to 36% (soil + BCSSL) and from 17 to 54% (soil + BCSSLW). In acidic BCSSL-amended soil and the alkaline BCSSLW-amended soil no statistically significant differences in the content of sum of 16 freely dissolved PAHs were noted between the beginning and end of the study. BCSSLW was characterized by a greater reduction content of organic solvent extractable PAHs in the acidic and alkaline soils, while in the neutral one – BCSSL. In turn, a larger reduction in freely dissolved PAH content in the acidic and neutral soils could be seen in the presence of BCSSLW, whereas in the alkaline soil in the presence of BCSSL. The persistence and bioavailability of PAHs in the biochar-amended soils were closely related to the chemical properties of these soils. This was confirmed by numerous statistically significant (P ≤ 0.05) relationships between organic solvent extractable PAHs and pH, cation exchange capacity, available magnesium, potassium and phosphorus, and dissolved organic carbon as well as between freely dissolved PAH and pH, dissolved organic carbon, available potassium and phosphorus content, and electrical conductivity.
422. 题目: Organic matter accumulation of the Upper Triassic Ma'antang shales in the Longmenshan Foreland Basin (western Sichuan, China)
The Upper Triassic Ma'antang Formation is not only an important set of source rocks in the Sichuan Basin but may also be a successor for shale gas in China. In this study, the provenance, tectonic setting, chemical weathering, environment and productivity of the middle-late Carnian (Tuvalian) are reconstructed from petrological and geochemical data to determine the origin of the Ma'antang shales. The brachiopod-dominated fossil composition, type II-dominated organic matter, and fluctuating water salinity reflect that the shale formed in a marine environment influenced by terrestrial influx. TiO2 vs. Zr and La/Th vs. Hf diagrams, as well as the combination of major elements indicate that the Sichuan Basin was a collisional setting in the Tuvalian, and the provenance was felsic igneous source rocks. Redox-sensitive elements indicate dysoxic-anoxic conditions. Samples with Cd/Mo < 0.1 and Co*Mn > 0.4 show normal levels of Cd and relative enrichment of Mn and Co, which supports that the shale is more likely to be a product of anoxic preservation mode associated with the restricted basin. In contrast, the moderate productivity conditions reflected by Babio and P/Ti are also positive factors for organic matter accumulation. Based on the reconstruction of these environmental parameters, several driving factors that promote the formation of high TOC shales are explored. It is believed that the rapid tectonic subsidence in the early stage of foreland basin evolution (undercompensation period) created accommodation space for the shale, and the deep water also promoted anoxic bottom water, which facilitated the preservation of organic matter. The Carnian Pluvial Episode (CPE) increased global weathering and rainfall, allowing the oceans to receive more terrestrial nutrients, and freshwater influx caused stratification due to differences in salinity between the surface water and bottom water. Volcanic ash from the Wrangellia Large Igneous Province (W-LIP) and local volcanoes were transported over long distances in the Late Triassic megamonsoons. Both were able to stimulate marine productivity, maintain and expand oceanic anoxia, and were beneficial for organic matter accumulation.
423. 题目: Enhanced removal of arsenic and cadmium from contaminated soils using a soluble humic substance coupled with chemical reductant
Soil washing is an efficient, economical, and green remediation technology for removing several heavy metal (loid)s from contaminated industrial sites. The extraction of green and efficient washing agents from low-cost feedback is crucially important. In this study, a soluble humic substance (HS) extracted from leonardite was first tested to wash soils (red soil, fluvo-aquic soil, and black soil) heavily contaminated with arsenic (As) and cadmium (Cd). A D-optimal mixture design was investigated to optimize the washing parameters. The optimum removal efficiencies of As and Cd by single HS washing were found to be 52.58%–60.20% and 58.52%–86.69%, respectively. Furthermore, a two-step sequential washing with chemical reductant NH2OH•HCl coupled with HS (NH2OH•HCl + HS) was performed to improve the removal efficiency of As and Cd. The two-step sequential washing significantly enhanced the removal of As and Cd to 75.25%–81.53% and 64.53%–97.64%, which makes the residual As and Cd in soil below the risk control standards for construction land. The two-step sequential washing also effectively controlled the mobility and bioavailability of residual As and Cd. However, the activities of soil catalase and urease significantly decreased after the NH2OH•HCl + HS washing. Follow-up measures such as soil neutralization could be applied to relieve and restore the soil enzyme activity. In general, the two-step sequential soil washing with NH2OH•HCl + HS is a fast and efficient method for simultaneously removing high content of As and Cd from contaminated soils.
424. 题目: Saline soil organic matter characteristics in aggregate size fractions after amelioration through straw and nitrogen application
425. 题目: Black carbon emissions and reduction potential in China: 2015–2050
Black carbon is a product of the incomplete combustion of carbonaceous fuels and has significant adverse effects on climate change, air quality, and human health. China has been a major contributor to global anthropogenic black carbon emissions. This study develops a black carbon inventory in China, using 2015 as the base year, and projects annual black carbon emissions in China for the period 2016–2050, under two scenarios: a Reference scenario and an Accelerated Reduction scenario. The study estimates that the total black carbon emissions in China in 2015 were 1100 thousand tons (kt), with residential use being the biggest contributor, accounting for more than half of the total black carbon emissions, followed by coke production, industry, agricultural waste burning, and transportation. This study then projects the total black carbon emissions in China in 2050 to be 278 kt in the Reference scenario and 86 kt in the Accelerated Reduction Scenario. Compared to the Reference scenario, the Accelerated Reduction scenario will achieve much faster and deeper black carbon reductions in all the sectors. The dramatic reductions can be attributed to the fuel switching in the residential sector, faster implementation of high-efficiency emission control measures in the industry, transportation, and coke production sectors, and faster phase-out of agricultural waste open burning. This analysis reveals the high potential of black carbon emission reductions across multiple sectors in China through the next thirty years.
426. 题目: A feasibility study on production, characterisation and application of empty fruit bunch oil palm biochar for Mn2+ removal from aqueous solution
Empty fruit bunch oil palm (EFBOP) is one of the byproducts after oil palm fruitlet is removed in oil palm processing and is considered as waste. In this study, EFBOP was converted to biochar (BC-EFBOP) at 350–700 °C, with an overarching aim of determining the feasibility of adsorptive removal of manganese (a second dominant element in acid mine draingae) from water. . Results showed that with increasing temperature, the BC-EFBOP yield decreased from 44.34% to 26.74%, along with the H/C (0.89%–0.29%) and O/C ratios (0.38%–0.23%), and the carbon content increased (62.7%–73.93%). As evidenced by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), abundant oxygen-containing surface functional groups such as hydroxyl (-OH), carboxyl (-COOH), and ether (C–O–C) were retained, and aromatic CC groups were largely generated in the biochar. Pyrolysed biochar at 350 °C (BC350), with the least surface area (0.5 m2 g−1), exhibited the highest Mn2+ adsorption capacity (8.2 mg g−1), whereas for BC700, with the largest surface area (2.19 m2 g−1), had the lowest capacity for Mn2+ (1.2 mg g−1). Regardless of the temperature, solution pH of 5 was found to be optimal for Mn2+ removal from water. The Langmuir isotherm model best described the equilibrium adsorption data with a maximum adsorption capacity of 1.2–8.2 mg g−1 for initial concentrations of 5–250 mg L−1, whereas the adsorption kinetics followed the pseudo-second-order model. There was nearly four-fold increase in Mn2+ ions removal with increased biochar dosage (0.05–0.5 g), at initial Mn2+ concentration of 100 mg L−1. The study showed that a low-cost, environmentally friendly BC-EFBOP with optimal surface chemistry could potentially remediate Mn2+ ions from aqueous media. However, a proper cost-benefit and techno-economic analysis is needed prior to potential pilot scale studies.
427. 题目: Insight into humification of mushroom residues under addition of Rich-N sources: Comparing key molecular evolution processes using EEM-PARAFAC and 2D-FTIR-COS analysis
Accelerating the humification of organic solid waste is one of the most important issues in composting. This present study aims to study and compare the humification process of different rich-N sources (chicken manure, cattle manure, and urea) addition during the composting of mushroom residues, from macro physicochemical properties to micro humic molecular structure evolution process. The physicochemical elements and humic components were determined for evaluating the compost quality and humification degree as composting proceed. The coupled analysis of excitation-emission matrix with parallel factor analysis (EEM-PARAFAC) and two-dimensional correlation with Fourier transform infrared spectrum (2D-FTIR-COS) were used to characterize the functional molecular structure evolution of dissolved organic matter during humification process. The results indicated that the rank order for humification level were the treatments of chicken manure (HM), urea (UM), cattle manure (CM), and single mushroom residue treatment (CK), with their humification index of 22.18%, 22.05%, 18.47%, and 16.52%, respectively. Humic substance, humic acid, and fulvic acid were obtained the highest in HM treatment with contents of 35.41 ± 0.86%, 23.32 ± 1.57%, and 10.97 ± 0.52%, respectively. The rich-N source addition enhanced the degradation of protein-like and polysaccharides-like substances in dissolved organic matter, thus accelerating the humification process of mushroom residues. The key structure evolution of dissolved organic matter in the HM treatment, in which the CO and CC stretching of quinone, amide, or ketone, and the C–O stretching of polysaccharides may be responsible for the faster formation of humus compared to the other nitrogen treatments. In this study, redundancy analysis indicated that the total nitrogen (TN) and nitrate nitrogen (NO3−-N) may be the potential indicators for determining the humification level as composting proceed. The result provides significant insight into the humification mechanism of mushroom residue under different types of nitrogen sources at the molecular level, and will be reference for improving the composting technique in practical field.
428. 题目: Fluorescence Quenching of Humic Substances and Natural Organic Matter by Nitroxide Free Radicals
429. 题目: Microscale spatial distribution and soil organic matter persistence in top and subsoil
The spatial distribution of organic substrates and microscale soil heterogeneity significantly influence organic matter (OM) persistence as constraints on OM accessibility to microorganisms. However, it is unclear how changes in OM spatial heterogeneity driven by factors such as soil depth affect the relative importance of substrate spatial distribution on OM persistence. This work evaluated the decomposition and persistence of 13C and 15N labeled water-extractable OM inputs over 50 days as either hotspot (i.e., pelleted in 1–2 mm-size pieces) or distributed (i.e., added as OM < 0.07 μm suspended in water) forms in topsoil (0–0.2 m) and subsoil (0.8–0.9 m) samples of an Andisol. We observed greater persistence of added C in the subsoil with distributed OM inputs relative to hotspot OM, indicated by a 17% reduction in cumulative mineralization of the added C and a 10% higher conversion to mineral-associated OM. A lower substrate availability potentially reduced mineralization due to OM dispersion throughout the soil. NanoSIMS (nanoscale secondary ion mass spectrometry) analysis identified organo-mineral associations on cross-sectioned aggregate interiors in the subsoil. On the other hand, in the topsoil, we did not observe significant differences in the persistence of OM, suggesting that the large amounts of particulate OM already present in the soil outweighed the influence of added OM spatial distribution. Here, we demonstrated under laboratory conditions that the spatial distribution of fresh OM input alone significantly affected the decomposition and persistence of OM inputs in the subsoil. On the other hand, spatial distribution seems to play a lower role in topsoils rich in particulate OM. The divergence in the influence of OM spatial distribution between the top and subsoil is likely driven by differences in soil mineralogy and OM composition.
430. 题目: Variability of sedimentary organic matter in subtropical estuarine systems due to anthropogenic and climatic events
Estuaries are ecosystems that have been changed by climatic and anthropogenic events, and subtropical estuaries located in the Southern Hemisphere are important examples of historical human occupation, land use and recent degradation. This study aims to assess whether climatic and anthropogenic events promoted the variability of sedimentary organic matter (OM) in two estuarine systems, the Paranaguá Estuarine System and Guaratuba Bay, Brazil, using geochemical multiproxies. In this approach, bulk elementary and isotopic properties were integrated with specific molecular biomarkers (n-alkanes, n-alkanol and sterols) detected in the sedimentary OM from sediment cores. Our results showed a predominance of terrigenous OM in both estuarine systems over the last century. However, sterols proved to be a more robust proxy for indicating changes in the autochthonous input of sedimentary OM, especially in the core top sections. Based on the molecular biomarkers and total annual precipitation data, the climatic effects of periodic events (e.g., El Niño–Southern Oscillation) that occurred during the last century did not seem to have imposed noticeable changes in the sedimentary OM over the period covered by the cores (e.g., between 1912 and 2010 for the Paranaguá Estuarine System). Instead, OM variations may respond to changes in the drainage basin or to specific local human activities. Plant extraction in the drainage basin was recorded in Guaratuba Bay before the 1960s, and the intensification of human occupation after the 1950s was recorded in the Paranaguá Estuarine System. The multiproxy approach demonstrated that local environmental changes related to regional anthropogenic events in the adjacent drainage basin of estuaries may be considered for identifying human impacts in coastal zones.
431. 题目: Aggregate-associated carbon contributes to soil organic carbon accumulation along the elevation gradient of Helan Mountains
Physically or biochemically protected soil organic carbon (SOC) can dampen microbial decomposition by reducing substrate availability, enhancing the stability of SOC. However, microbe-mediated changes in the physical and chemical compositions of SOC along an elevation gradient are poorly understood, especially in arid mountain environments. Here, soil samples from depths of 0–20 cm and 20–40 cm along five elevations ranging from 1380 to 2438 m in Helan Mountains were collected. We explored the effect of the soil microbial community and enzyme activities on the physical (via aggregate-associate C) and chemical compositions of SOC. The results showed that the amount of aggregate-associated C, the abundance of microbes and enzyme activities were significantly greater in the 0–20 cm than the 20–40 cm soil layer. The ratio of fungi to bacteria (F/B), aggregate-associated C, and cellobiohydrolase (CBH) activity increased with elevation. However, the highest proportion of aromatic C, total PLFA, β-glucosidase (BG), N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (AP) were found at the mid-elevation (2139 m), with a hump-shaped unimodal distribution pattern. This indicated that soil microbes at mid-elevation had the highest potential to decompose the relatively labile carbon compositions. CBH explained the most variations in the physical and chemical compositions of the SOC and had a significant effect on the macroaggregate- and silt and clay-associated C. Structural equation modeling (SEM) indicated that with an increase in elevation, F/B and the enzyme activities involved in C cycling (BG, CBH) decreased physical protection and recalcitrance of SOC. Collectively, our findings demonstrated that the primary mechanism for SOC accumulation in the Helan Mountains was the decrease in aggregate-protected C with an increase in elevation.
432. 题目: A data-driven approach for understanding the structure dependence of redox activity in humic substances
Humic substances (HS) can facilitate electron transfer during biogeochemical processes due to their redox properties, but the structure-redox activity relationships are still difficult to describe and poorly understood. Herein, the linear (Partial Least Squares regressions; PLS) and nonlinear (artificial neural network; ANN) models were applied to monitor the structure dependence of HS redox activities in terms of electron accepting (EAC), electron donating (EDC) and overall electron transfer capacities (ETC) using its physicochemical features as input variables. The PLS model exhibited a moderate ability with R2 values of 0.60, 0.53 and 0.65 to evaluate EAC, EDC and ETC, respectively. The variable influence in the projection (VIP) scores of the PLS identified that the phenols, quinones and aromatic systems were particularly important for describing the redox activities of HS. Compared with the PLS model, the back-propagation ANN model achieved higher performance with R2 values of 0.81, 0.65 and 0.78 for monitoring the EAC, EDC and ETC, respectively. Sensitivity analysis of the ANN separately identified that the EAC highly depended on quinones, aromatics and protein-like fluorophores, while the EDC depended on phenols, aromatics and humic-like fluorophores (or stable free radicals). Additionally, carboxylic groups were the best indicator for evaluating both the EAC and EDC. Good model performances were obtained from the selected features via the PLS and sensitivity analysis, further confirming the accuracy of describing the structure-redox activity relationships with these analyses. This study provides a potential approach for identifying the structure-activity relationships of HS and an efficient machine-learning model for predicting HS redox activities.
433. 题目: Effects of emergent plants on soil carbon-fixation and denitrification processes in freshwater and brackish wetlands in a watershed in northern China
Plants could affect wetland ecosystem functions by influencing the carbon and nitrogen cycles driven by microorganisms. However, the underlying mechanisms associated with CO2-fixation rate (CFR) by autotrophic microbes and denitrification rate (DR) in relation to wetland emergent plants remain unclear. In this study, we conducted a field experiment to analyze the effects of emergent plants on the activities and community characteristics of CO2-fixing autotrophic bacteria and denitrifying bacteria in two types of wetlands in a lake basin: freshwater and brackish water. We found that the effects of emergent plants on CFR and DR differed between freshwater and brackish wetlands. Compared to freshwater wetland, brackish wetland exhibited higher CFR in the rhizosphere, probably due to the abundance of organic carbon conducive to facultative autotrophic bacteria. However, the lower rhizosphere DR in brackish wetland compared to that in freshwater wetland was due to the salt stress. In both freshwater and brackish wetlands, rhizosphere soil increased CFR and DR. The microbial communities associated with them were distinct from those in non-rhizosphere. Besides, neutral-based processes governed the assembly of these bacterial communities, while the rhizosphere showed more prominent dominance of niche-based processes than non-rhizosphere. Statistical analyses revealed that soil organic carbon and root exudates jointly drove the differences in the metabolic activities and composition of CO2-fixation- and denitrification-associated microbial communities between rhizosphere and non-rhizosphere. Overall, our findings suggest that the organic carbon released by plants through root exudates and plant litter is vital for promoting wetland soil carbon-fixation and denitrification and alleviating the detrimental effects of salinity on denitrification. This study provides valuable information for the conservation of CO2-fixation and nitrogen removal with suitable plant species in wetlands.
434. 题目: Macropores and burial of dissolved organic matter affect nitrate removal in intertidal aquifers
Coastal ecosystems are sensitive to the input of chemicals originating from submarine groundwater discharge (SGD). The mixing zone between freshwater and saltwater in beach aquifers promotes biogeochemical transformations affecting nutrient fluxes into the coastal ocean. Macropores affect groundwater flow, leading to a more complicated mixing process and greatly promoting nitrogen transformations. Laboratory-scale experiments and numerical modeling were employed in this study to investigate how macropores affect freshwater-saltwater mixing and terrestrial solute transport. A numerical investigation is presented demonstrating the influence of macropores on the transport and transformation of nitrate (NO3−) in a homogeneous unconfined nearshore aquifer under spring-neap tide action using COMSOL. The results indicate that macropores modify the groundwater discharge pathway of terrestrial NO3− by changing nearshore groundwater flow dynamics. The denitrification zone expanded from the low tide mark to the high tide mark, extended downward to the base of the upper saline plume (USP), and expanded with increasing macropore depth and quantity. Macropores increased NO3− removal by creating larger mixing zones, which increased with the macropore depth and quantity. Lower freshwater levels enhanced denitrification and weakened the impact of macropores on denitrification. The deep burial dissolved organic matter (DB-DOM) simulation results demonstrated that dissolved organic matter (DOM) could stimulate denitrifiers to increase the denitrification zone by fully consuming O2 along longer flow paths, resulting in up to 85% higher NO3− removal. The findings provide notable implications for management design engineering to protect coastal ecosystems and decrease NO3− fluxes into the ocean.
435. 题目: Synthesis of N-doped sludge biochar using the hydrothermal route-enabled carbonization method for the efficient degradation of organic pollutants by peroxymonosulfate activation
Nitrogen-doped biochar (HTNBC) was prepared from sewage sludge via hydrothermal route-enabled carbonization, and the optimized HTNBC was found to efficiently activate peroxymonosulfate (PMS) by aiming the less consumption of the chemicals. The optimal HTNBC degraded a 0.1 mM aqueous solution of bisphenol A (BPA) within 10 min at a rate of 0.62 min−1, exhibiting a significantly superior catalytic activity compared to that of pristine sludge biochar. The HTNBC/PMS system effectively oxidized various organic pollutants, including BPA, sulfamethoxazole, 4-chlorophenol, carbamazepine, and nitrobenzene with a low consumption of PMS (1.0 mM) and a low catalyst loading (0.2 g/L). The active sites for PMS activation were identified as graphitic-N, pyridinic-N, and carbonyl groups, besides structural defects and a high specific surface area were also important. The primary oxidation mechanism was anticipated to involve non-radical pathways followed by radical-induced oxidation, in which the surface-bound reactions dominate. The HTNBC/PMS system acts over a wide pH range and exhibits a high resistance to the inorganic anions of natural water. Our results indicate that nitrogen doping via a hydrothermal route allows the fabrication of biochar with a greater abundance of oxygen functional groups, and the specific nitrogen species present within the carbon matrix are also of importance in the development of advanced carbon catalysts.
436. 题目: Spatiotemporal analysis of fluorescent dissolved organic matter to identify the impacts of failing sewer infrastructure in urban streams
Failing sewer infrastructure introduces raw wastewater into streams. We used fluorescence excitation-emission matrix (EEM) spectroscopy and parallel factor analysis (PARAFAC) to track hotspots of raw wastewater in low- and medium-order urban streams that do not receive wastewater effluent but are impacted by sanitary sewer overflows, septic systems, and sewer exfiltration. After analyzing 296 surface water samples from 27 sites in two watersheds over a one-year period, we proposed that the (i) area-normalized ratio of soluble microbial product-like to humic acid-like fluorescence (R4/R5 ≥ 0.85) and (ii) ratio of EEM-PARAFAC components with tryptophan-like and fulvic acid-like fluorescence (C4/C3 ≥ 1.45) could distinguish when and where untreated wastewater is introduced to urban streams. The proposed ratios were validated by co-detection of contaminants of emerging concern, such as sucralose, antibiotics, and UV filters, at concentrations as high as 1,354, 108, and 212 ng L−1, respectively. Based on the aggregate data, we identified three sites in rural/suburban areas that were impacted by septic systems and ten sites in urban sections affected by sanitary sewer overflows and/or sewer exfiltration. Moreover, the ratiometric C4/C3 and R4/R5 parameters were immune to dilution effects caused by rain events. Impacts on upstream sites were mostly identified in spring and early summer, but urban hotspots occurred in almost every month. These findings confirmed the potential for EEM-PARAFAC-based wastewater indicators as a quick, easy, cost-effective, and scalable technique to screen for failing sewer infrastructure in low-order streams.
437. 题目: The role of biochar and zeolite in enhancing nitrogen and phosphorus recovery: A sustainable manure management technology
Swine manure is a potential source of plant-available ortho-phosphate (ortho-P) and ammonium (NH4+). However, transport and application issues restrict its widespread use in agriculture and cause water quality degradation. This study investigates the potential of biochar (BC) produced from corn stover (control-BC) and FeSO4 pretreated corn stover (Fe-BC) and zeolite to recover ortho-P and NH4+ from liquid swine manure. Chemisorption increased ortho-P sorption from manure onto Fe-BC (29,831 mg kg-1) relative to control-BC (19,000 mg kg-1). During Mehlich III (M-III) desorption study, manure-treated Fe-BC and control-BC released 34% and 80% of adsorbed ortho-P, respectively. Increasing the BC loading rate from 5 g L-1 to 25 g L-1 in manure significantly dropped the M-III P desorption (<10%) for the Fe-BC but not for the control-BC. Sorption of manure NH4+ on Fe-BC, control-BC, and zeolite occurred by I) specific adsorption on surfaces and within pores, II) co-adsorption of NH4+ with manure colloids, and III) precipitation as N-minerals (struvite). The NH3 volatilization and KCl desorption studies revealed that NH4+ sorption/desorption from manure to BC cannot be explained by simple ion exchange or volatilization loss. The BC-zeolite combination increased the NH4+ recovery from manure (28-38%) relative to BC’s without zeolite addition. SEM-EDS and XRD analyses revealed the association of P with both Mg and Fe and the presence of struvite (NH4MgPO4·6H2O) in batch and centrifuge studies. Our results suggest that low-cost BC and zeolite can recover ortho-P and NH4+ from liquid swine manure, which may facilitate its easy transport and widespread application in agriculture.
438. 题目: Methane Production Linked to Organic Matter Molecule and Methanogenic Community in Estuarine Benthic Sediments
439. 题目: Mechanochemical modified nitrogen-rich biochar derived from shrimp shell: Dominant mechanism in pyridinic-N for aquatic methylene blue removal
N-doping for the preparation of functional carbon materials is a trending research topic. In this study, N-rich biochar (BC) was prepared by calcining naturally N rich shrimp shells under oxygen-limiting environment, and the calcining temperatures were controlled. BC were activated with 5% hydrochloric acid solutions and then post-modified with ball-milling to obtain a series of novel adsorbents (MBCs). All samples were characterized by SEM, BET, FT-IR, XRD, XPS, TG, and element analysis. Surface area, pore volume, and other surface functional groups were significantly improved after acidizing and ball-milling. The adsorption capacities for MB were MBC350 > MBC500 > MBC650 >BC350 > BC650 > BC500, and the equilibrium adsorption capacities were 575.01 mg/g, 506.52 mg/g, 424.59 mg/g, 113.31 mg/g, 93.53 mg/g and 86.25 mg/g, respectively. The excellent adsorption performance of MBCs for MB was ascribed to Lewis acid-base interaction, π-π interaction, electrostatic interaction and van der Waals, and the quinone group and pyridinic-N on the surface of the MBCs are identified as the major active sites. Taken together, ball-milled shrimp shell biochar is a promising material for cation dye adsorption.
440. 题目: Drying-rewetting of permanent pasture and agricultural soils induces a shift towards microbial use of more C-rich organic matter
Rewetting dry soil induces enormous dynamics in microbial growth and biogeochemistry. The temporal dynamics of soil carbon (C) mineralization following drying-rewetting (D/RW) have been widely documented. However, there have been far fewer assessments of gross nitrogen (N) mineralization, and it remains unclear how C and N mineralization dynamics are linked following D/RW events. To address this, soils were sampled from permanent pasture and tilled-and-cropped agricultural fields at two depths (“shallow” soils from 0 to 5 cm depth and “deep” soils from >15 cm depth), with soil C mineralization and gross N mineralization, along with responses in bacterial and fungal growth, measured at high temporal resolution after D/RW. Although soil C mineralization and gross N mineralization were both stimulated by D/RW, the dynamics in C and N mineralization were transiently decoupled. In the cropland soils from both depths, C mineralization peaked immediately and then declined, while N mineralization was sustained at a high level. Similarly, in the deep pasture soil, N mineralization peaked immediately and then declined while C mineralization was maintained at a high level. The shallow pasture was the only soil where C mineralization and N mineralization dynamics were clearly linked after D/RW, both during the first 24 h, and throughout the 7-day study. Interestingly, in all cases, the ratio of soil C mineralization to N mineralization after D/RW was higher than in moist control soils, suggesting a consistent shift towards microbial use of more C-rich organic matter. The shift was especially pronounced in the pasture soils, where the C-to-N ratio of substrate used after D/RW was more indicative of plant-residues than microbial necromass. The δ13C-signature of respired CO2 was also consistently lower after D/RW compared to that of the moist control – particularly for the pasture soils – providing further evidence that the organic matter used by microorganisms after D/RW was more recently plant-derived than that targeted by microorganisms under optimal moisture conditions. Together, these results highlight that while C and N mineralization are both stimulated by D/RW, changes in mineralization rates do not necessarily occur in parallel, with shifts in the ratio of C-to-N mineralization reflecting shifts in the source of organic matter being used by microorganisms.