1. 题目: Feasibility of the 4 per 1000 initiative in Bavaria: A reality check of agricultural soil management and carbon sequestration scenarios
An increase of soil organic carbon (SOC) stocks in agricultural soils does not only have positive effects on soil quality and soil resilience but may also contribute to climate change mitigation. The '4 per 1000′ (4p1000) initiative launched at the 2015 United Nations Climate Change Conference in Paris aims at increasing global SOC stocks in 0–40 cm depth by annually 4‰ in order to compensate the increase of anthropogenic CO2 emissions. In this study we analysed the feasibility of this target for agricultural soils in Bavaria, Southeast Germany. Assuming a total organic carbon (OC) amount of 276 Tg currently stored in the upper 40 cm of agricultural soils in Bavaria (cropland and grassland), the 4p1000 goal corresponds to an annual carbon (C) sequestration of 1.1 Tg. Based on a site-specific analysis of present soil management, we developed spatially explicit C sequestration scenarios including five promising management practices (cover cropping, improved crop rotation, organic farming, agroforestry and conversion of arable land to grassland). The results revealed that the 4p1000 target is not feasible for Bavaria. The total potential of the five practices to sequester C resulted in increases in 0.3 to 0.4 Tg OC per year corresponding to around 1‰ of the present SOC stocks. Expansion of cover crops and agroforestry were identified as most promising options to increase SOC in agricultural soils. Although only around 1.5% of Bavaria's yearly GHG emissions would be compensated, this represents an essential contribution to climate change mitigation. Besides the need to develop new incentive systems (particularly for agroforestry), implementation of networks including farms and/or field trials that demonstrate improved soil management practices would be required to inform farmers and other stakeholders about the benefits of such practices. To maintain a resilient agriculture that withstands more extreme weather conditions in the future, healthy soils are needed. We therefore conclude that expected positive effects of a SOC stock increase on nutrient and water storage, soil erosion, biodiversity and food security are crucial for climate change adaptation.
2. 题目: Effect of biochar on soil properties on the Loess Plateau: Results from field experiments
Soil erosion on the Loess Plateau has been partly controlled, but soil nutrients remain limited throughout the region. Biochar amendments are an efficient method of improving availability of soil nutrients due to their strong adsorptive capacity; however, the effects of biochar amendments on different soil types on the Loess Plateau are not well understood. In this paper, we compared the effects of biochar on soil bulk density, soil organic carbon, and soil nitrogen and phosphorus contents among four soil types on the Loess Plateau. An eight-year field study was conducted in Loessal soil, Dark Loessial soil, Lou soil, and Aeolian sandy soil to investigate changes in soil bulk density and nutrient retention caused by biochar amendment at rates of 0 g/kg (control), 4 g/kg, 8 g/kg and 16 g/kg. Soil organic carbon, total nitrogen, total phosphorus, ammonium nitrogen, and nitrate nitrogen concentrations were measured eight years after biochar application. The biochar amendments significantly increased the soil organic carbon and nitrate nitrogen concentrations in the 0–40 cm layer of all soils. The nitrate nitrogen concentration in the Lou soil and Dark Loessial soil decreased with 4 g/kg biochar application and increased significantly with 8 g/kg and 16 g/kg biochar application, but it did not significantly change in the Loessal soil. In contrast, the nitrate nitrogen concentration in the Aeolian sandy soil decreased with increasing biochar application. Biochar amendments did not significantly influence soil ammonium nitrogen in the 0–20 cm soil layer. However, the soil phosphorus content in the 0–20 cm layer decreased with increasing biochar application, except in the Lou soil and Aeolian sandy soil. These data suggest that biochar-soil interactions on the Loess Plateau have the potential to enhance soil organic carbon and soil nitrogen storage. Moreover, using an appropriate biochar amendment rate according to soil type might help optimise the use of fertilizer on the Loess Plateau.
3. 题目: Can conservation agriculture increase soil carbon sequestration? A modelling approach
Conservation agriculture (CA) involves complex and interactive processes that ultimately determine soil carbon (C) storage, making it difficult to identify clear patterns. To solve these problems, we used the ARMOSA process-based crop model to simulate the contribution of different CA components (minimum soil disturbance, permanent soil cover with crop residues and/or cover crops, and diversification of plant species) to soil organic carbon stock (SOC) sequestration at 0–30 cm soil depth and to compare it with SOC evolution under conventional agricultural practices. We simulated SOC changes in three sites located in Central Asia (Almalybak, Kazakhstan), Northern Europe (Jokioinen, Finland) and Southern Europe (Lombriasco, Italy), which have contrasting soils, organic carbon contents, climates, crops and management intensity. Simulations were carried out for the current climate conditions (1998–2017) and future climatic scenario (period 2020–2040, scenario Representative Concentration Pathway RCP 6.0).
Five cropping systems were simulated: conventional systems under ploughing with monoculture and residues removed (Conv − R) or residues retained (Conv + R); no-tillage (NT); CA and CA with a cover crop, Italian ryegrass (CA + CC). In Conv − R, Conv + R and NT, the simulated monocultures were spring barley in Almalybak and Jokioinen, and maize in Lombriasco. In all sites, conventional systems led to SOC decline of 170–1000 kg ha−1 yr−1, whereas NT can slightly increase the SOC. CA and CA + CC have the potential for a C sequestration rate of 0.4% yr−1 or higher in Almalybak and Jokioinen, and thus, the objective of the 4 per 1000 initiative can be achieved. Cover crops (in CA + CC) have a potential for a C sequestration rate of 0.36–0.5% yr−1 in Southern Finland and in Southern Kazakhstan under the current climate conditions, and their role will grow in importance in the future. Even if in Lombriasco it was not possible to meet the 4 per 1000, there was a SOC increase under CA and CA + CC. In conclusion, the simultaneous adoption of all the three CA principles becomes more and more relevant in order to accomplish soil C sequestration as an urgent action to combat climate change and to ensure food security.
4. 题目: Soil physical changes induced by sugarcane cultivation in the Atlantic Forest biome, northeastern Brazil
In northeastern Brazil, the sugarcane expansion has occurred historically over the Atlantic Forest biome. However, little is known about the physical process and changes induced by sugarcane cultivation in this biome. Thus, a field study was conducted to evaluate changes induced by sugarcane cultivation on soil physical properties, processes and functions in the Atlantic Forest biome. For that, soil samples were collected at three sites in northeastern Brazil: AF – Atlantic Forest, SCratoon – successive sugarcane ratoon cultivation and SCtill – tilled soil for sugarcane replanting. Quantitative and semi-quantitative soil properties [i.e. bulk density, soil penetration resistance (SPR), water-stable aggregates, soil organic carbon (C), pore size distribution and Visual Evaluation of Soil Structure (VESS) scores] were examined. In addition, four critical soil functions were evaluated by a soil physical quality index (SPQI). Atlantic Forest soil presented the greatest soil physical quality (i.e. lower bulk density, higher porosity, soil C and soil aggregate stability), functioning, according to SPQI, at 88% of its full capacity. However, SPR under AF was significantly higher than SCratoon and SCtill. Soil tillage reduced SPR in SCtill compared to the area under successive sugarcane cultivation (SCratoon). The results revealed that the high SPR in AF and SCratoon areas occurred without soil volume variation (i.e. no compaction) in relation to the SCtill, indicating that these soils are susceptible to hardening induced by C bonds and thixotropy processes. Soil tillage for sugarcane replanting resulted in immediate improvements on physical conditions for root growth by decreasing SPR; however, soil disturbance increases its susceptibility to degradation by reducing water-stable soil aggregate, organic C and aeration pores. Thus, sugarcane cultivation declined the performance of soil physical functions to 72 and 67% of its full capacity in SCtill and SCratoon, respectively. Finally, best management practices to reduce soil disturbance and increase C should be prioritised, as well as minimising the mechanisms responsible by soil hardening in order to reduce soil physical degradation and improve the environment for root growth in sugarcane fields.
5. 题目: Hyperspectral imaging for high-resolution mapping of soil carbon fractions in intact paddy soil profiles with multivariate techniques and variable selection
Soil organic carbon (SOC) and its labile C fractions play a central role in soil quality and C cycles. This study aimed to investigate the potential of laboratory-based hyperspectral imaging (HSI) spectroscopy to predict and map SOC and its labile C fractions (e.g., dissolved organic C, DOC; readily oxidizable organic C, ROC; and microbial biomass C, MBC) in soil profiles with a high resolution. The HSI images were captured from 16 intact paddy soil profiles to a depth of 100 ± 5 cm from four typical parent materials. The linear (i.e., partial least squares regression, PLSR) and nonlinear (i.e., artificial neural networks, ANN; cubist regression tree, Cubist; Gaussian process regression, GPR; and support vector machine regression, SVMR) multivariate techniques were compared to assess their ability to map the soil C fractions in the profiles. A spectral variable selection technique (i.e., competitive adaptive reweighted sampling, CARS) was applied to these multivariate models (i.e., CARS-PLSR, CARS-ANN, CARS-Cubist, CARS-GPR, and CARS-SVMR). Overall, the results showed that the nonlinear models performed better than the PLSR models in most cases. All optimized multivariate models with CARS achieved prediction performances similar to the full spectrum models, with high Lin's concordance correlation coefficient (LCC) and low root mean square error (RMSE). CARS-SVMR used only 37–70 spectral variables and took less time-consuming on computations (<0.5 min). Considering both the prediction performance and model-run efficiency, the CARS-SVMR models for SOC (LCCP = 0.98, RMSEP = 1.48 g kg−1), DOC (LCCP = 0.93, RMSEP = 100.61 mg kg−1), ROC (LCCP = 0.94, RMSEP = 0.70 g kg−1), and MBC (LCCP = 0.61, RMSEP = 58.12 mg kg−1) were superior to the other optimized models based on the independent validation. It was concluded that HSI spectroscopy coupled with CARS-SVMR is suitable for the high-resolution mapping of SOC and its labile C fractions in the intact paddy soil profiles.
6. 题目: Influences of arbuscular mycorrhizae, phosphorus fertiliser and biochar on alfalfa growth, nutrient status and cadmium uptake
The objective of the study was to explore the influences of arbuscular mycorrhizae (AM), phosphorus (P) fertiliser, biochar application (BC) and their interactions on Medicago sativa growth, nutrient, Cd content and AM fungi-plant symbioses. Applications of both P fertiliser and BC significantly increased total biomass and P and potassium (K) uptake, regardless of AM. When no P fertiliser or BC was used, the shoot biomass and nitrogen (N), P, and K contents in the +AM treatments were 1.39, 1.54, 4.53 and 2.06 times higher than those in the –AM treatments, respectively. AM fungi only elevated the total P uptake by 44.03% when P fertiliser was applied at a rate of 30 mg P kg−1 in the absence of BC addition. With BC application or high-P fertiliser input (100 mg P kg−1), the soil available P was significantly higher than that in the other treatments, and AM fungi significantly reduced the shoot biomass. The minimum Cd concentration occurred in the shoots of alfalfas treated with BC and high-P fertiliser inputs; this concentration was lower than the maximum permitted concentration in China. Although the BC and high-P inputs could eliminate the positive mycorrhizal response, the results suggested that BC application in combination with high-P fertiliser input could not only increase forage yields but also lower Cd concentrations to meet the forage safety standards by the dilution effect.
7. 题目: One-pot hydrothermal synthesis of NaLa(CO3)2 decorated magnetic biochar for efficient phosphate removal from water: Kinetics, isotherms, thermodynamics, mechanisms and reusability exploration
Phosphate elimination is vital for the remediation of eutrophication to avoid deterioration of water quality. Lanthanum (La) based adsorbents have been proven to have the potential for the removal of phosphate in contaminated water because of its strong affinity for phosphate. Herein, we report the high efficiency of NaLa(CO3)2 decorated magnetic biochar described as La-Fe-BC for the elimination of phosphate in water. The adsorbent was simply and facilely prepared through a one-pot hydrothermal method, and the characterization results confirmed the effective activation of biochar by KHCO3 and the successful infusion of NaLa(CO3)2 and Fe3O4 onto the surface of La-Fe-BC. The batch adsorption studies revealed that the La-Fe-BC exhibited an excellent monolayer phosphate uptake of 330.86 mg/g over a wide pH range of 3.0–8.0, undisturbed affinity to phosphate in the presence of various co-existing ions (e.g. , and ), prominent magnetic separation efficacy of 91%, superior reusability with more than 88% of desorption efficiency and 65% of phosphate uptake maintained after five adsorption-desorption recycles. Thermodynamic results presented a negative value of ΔG0, clearly indicative of a favorable and spontaneous reaction, while the positive values of ΔH0 and ΔS0 affirmed the endothermic characteristic of phosphate uptake onto La-Fe-BC with an increase in randomness. The La groups (i.e. and ) on La-Fe-BC are believed to enhance the phosphate binding owing to a combination of electrostatic attraction and inner-sphere complexation via ligand exchange. Overall, this study enables the omnidirectional enhancement of tailored adsorbents to the depollution of phosphate contaminated water.
8. 题目: Contrasting responses of macro- and meso-fauna to biochar additions in a bioenergy cropping system
Combining bioenergy land use with biochar production could represent a win-win management strategy to increase energy production whilst reducing greenhouse gas emissions. However, a fuller understanding of the effects that these changes in land use and soil amendment could have on soil biodiversity and processes is needed. We performed a 2-year field experiment to determine the consequences of adding three different amounts of biochar (10 t ha−1, 25 t ha−1 and 50 t ha−1) to a commercial Miscanthus bioenergy plantation on soil invertebrate community structure and abundances of enchytraeids, collembolans, mites and earthworms. We also used stable isotope analyses to determine shifts in feeding preferences and to quantify C assimilation by those soil organisms most likely to be affected by soil amendments (i.e. soil ingesters: earthworms and enchytraeids). Results showed that biochar additions to the soil had a negative effect on larger-sized soil fauna (earthworms) significantly reducing their population sizes and species richness whereas, in contrast, mesofauna appeared to benefit from the input of the biochar. Although significant assimilation of new C by anecic earthworms was observed, it was clearly insufficient to support population growth and, more importantly, the dominant ecological group in these agricultural soils (endogeics) showed the lowest assimilation values. These results indicate that biochar additions might result in the loss of some of the ecosystem services provided by earthworms, an important concern in these intensively managed agricultural soils. Finally, our findings highlight the need for more field research at species level to fully elucidate the mechanisms driving the biological responses of these types of ecosystem management.
9. 题目: Effect of extracellular polymer substances on the tetracycline removal during coagulation process
In this study, the effect of extracellular polymer substances on the tetracycline removal under hydroxyl aluminium treatment was investigated, and the molecular mechanisms of extracellular polymeric substances mediated coagulation of tetracycline were also explored. The results show that the presence of extracellular polymeric substances could significantly enhance the removal efficiency of tetracycline in hydroxyl aluminium coagulation. Findings suggest that tyrosine and tryptophan in extracellular proteins acted as binding sites to capture tetracycline. Evidences provided by the density functional theory calculations in combination with spectroscopy analysis indicated that two main mechanisms accounted for tetracycline removal in the presence of extracellular polymeric substances and polyaluminum chloride: (1) amino group in proteins and carbonyl in tetracycline were bridged by Al3+; (2) benzene rings in tryptophan and tyrosine were π–π stacked with tetracycline, and the amino group in complexes were further coordinated with Al3+.
10. 题目: Sustainable remediation with electroactive biochar system: Mechanisms and perspectives
11. 题目: Characteristic of dissolved organic matter polar fractions with variable sources by spectrum technologies: Chemical properties and interaction with phenoxy herbicide
Dissolved organic matter (DOM) is ubiquitous with high biological and chemical activity. The large intake of DOM from compost, plant residues or soil can modify the behaviors of agrochemicals. Phenoxy herbicide is the third widely used herbicide around the world with both aromaticity and polarity. However, how the diverse fractions of DOM interacting with phenoxy herbicide and the underlying mechanisms remain unknown. Thus, it is crucial to investigate the heterogeneous chemical properties of DOM fractions from variable sources and explore the interactive mechanisms. In this study, polar DOM derived from compost, rice straw and soil were fractionated, and the chemical properties of fractions were analyzed by spectrum technology and the complex interaction with phenoxy herbicide was assessed by infrared spectroscopy. Results showed that hydrophobic acid (HOA) was the largest component (49.6%) in compost DOM, while hydrophilic matter (HIM) was the main component in the polar DOM from rice straw and soil. The 4-chloro-2-methylphenoxyac etic acid (MCPA) as one representative of phenoxy herbicides was used in our study, and the results showed the interaction between different DOM fractions and MCPA was heterogeneous. HOA containing abundant fulvic-like component and polar groups resulted a greatly complex interaction with MCPA mainly via hydrophobic force, ligand exchange and hydrogen bonding. Hydrophobic neutral fraction and acid-insoluble matter showed a medium interaction with MCPA as a result of enrichment with the high aromatic humic-like molecules. Inversely, no significant interaction between HIM and MCPA was observed. Our research revealed that the aromatic framework associated with polar groups in DOM dominated the interaction with phenoxy herbicide, which might affect the bioavailability, toxicity, and mobility of phenoxy herbicide.
12. 题目: XPS and two-dimensional FTIR correlation analysis on the binding characteristics of humic acid onto kaolinite surface
The stabilization and preservation of soil organic matter have been attributed to the strong reactive sites of mineral surfaces that cause physical isolation and chemical stabilization due to the organic-mineral interface. However, much of the micro-scale knowledge about interactions between organic ligands and minerals largely remains at the qualitative level, and neglects the heterogeneity of functional groups of organic matter. Here, we report the use of molecular-scale technologies of two-dimensional FTIR Correlation Spectroscopy (2D-FTIR-CoS) and X-ray Photoelectron Spectroscopy (XPS) to directly measure the binding processes of humic acid (JGHA) groups onto kaolinite surface. The spectroscopy results showed that the carboxylate groups, aliphatic OH and aromatic structure participate in the binding of JGHA on kaolinite surface. The carboxylic and phenolic hydroxyl interact with kaolinite surface through the interfacial COAl/Si bonds. Kaolinite prefers to adsorb C-groups at pH 4.0 and O-groups at pH 8.0. The interaction of COO– group at 1566 cm−1 of JGHA leads to the formation of inner-sphere complex first and then outer-sphere complex with increasing contact time. The interaction of COOH group at 1261 cm−1 with the AlOH2+ of kaolinite was could be ascribed to ligand exchange and/or electrostatic attraction, whose contribution was evaluated to be 13.90%, 7.65% and 0% at pH 4.0, 6.0 and 8.0, respectively. These results of molecular binding provide quantitative mechanistic insights into organic-mineral interactions and expound the effect of functional groups of HA on binding mechanisms, and thus bring important clues for better understanding the mobility and transformation of land‑carbon including mineral-bound carbon.
13. 题目: The release of organic matter, nitrogen, phosphorus and heavy metals from erythromycin fermentation residue under heat-activated persulfate oxidation conditioning
Erythromycin fermentation residue (EFR) is one kind of biological waste with high organic matter content. The recycling of EFR is not only beneficial to the environmental protection, but also to the economic development. In this study, the release of organic matter, nitrogen (N), phosphorus (P) and heavy metals (HMs) from EFR under heat-activated persulfate (PS) oxidation conditioning was investigated. Results indicated that oxidation conditioning promoted the release of soluble chemical oxygen demand (SCOD). Heat-activated PS oxidation conditioning boosted the release of total nitrogen (TN), ammonia‑nitrogen (NH4+-N) and nitrate‑nitrogen (NO3−-N) into the supernatant, as well as the decomposition of organic nitrogen (ON). Concurrently, heat-activated PS oxidation conditioning facilitated the release of total phosphorus (TP), orthophosphate (PO43−-P) and organic phosphorus (OP) into the supernatant, and the decomposition of OP. Furthermore, heat-activated PS oxidation conditioning resulted in the increase of release efficiencies of HMs. Therefore, heat-activated PS oxidation conditioning was beneficial to the release of organic matter, nutrients and HMs.
14. 题目: Effects of ZnO nanoparticles on aerobic denitrifying bacteria Enterobacter cloacae strain HNR
The aerobic denitrification process is a promising and cost-effective alternative to the conventional nitrogen removal process. Widely used ZnO nanoparticles (NPs) will inevitably reach wastewater treatment plants, and cause adverse impacts on aerobic denitrification and nitrogen removal. Therefore, a full understanding of the responses and adaption of aerobic denitrifiers to ZnO NPs is essential to develop effective strategies to reduce adverse effects on wastewater treatment. In this study, the responses and adaption to ZnO NPs were investigated of a wild type strain (WT) and a resistant type strain (Re) of aerobic denitrifying bacteria Enterobacter cloacae strain HNR. When exposed to 0.75 mM ZnO NPs, the nitrate removal efficiency of Re was 11.2% higher than that of WT. To prevent ZnO NPs entering cells by adsorption, the production of extracellular polymeric substances (EPS) of WT and Re strains increased 13.2% and 43.9%, respectively. The upregulations of amino sugar and carbohydrate-related metabolism contributed to the increase of EPS production, and the increased nitrogen metabolism contributed to higher activities of nitrate and nitrite reductases. Interestingly, cationic antimicrobial peptide resistance contributed to resist Zn (II) released by ZnO NPs, and many antioxidative stress-related metabolism pathways were upregulated to resist the oxidative stress resulting from ZnO NPs. These findings will guide efforts to improve the aerobic denitrification process in an environment polluted by NPs, and promote the application of aerobic denitrification technologies.
15. 题目: Distribution and source identification of potentially toxic elements in agricultural soils through high-resolution sampling
Accumulation of potentially toxic elements (PTEs) in agricultural soils has become an increasingly global issue driven by industrialization. A credible knowledge of their distribution and diverse sources in soils is essential to developing effective measures of identifying accumulation of PTEs in rural and periurban environments. However, the assessment of PTE pollution levels and discrimination of anthropogenic and natural sources remain a serious challenge. In China, most studies are focused on highly industrialized and/or urbanized regions, while limited attention has been given to agricultural areas where diffuse source contamination prevails. Therefore, a large dataset of 5207 surface soil samples (1 × 1 km) and 1311 subsoil samples (2 × 2 km) were collected from an agriculturally dominated region in eastern China. Soil total concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were analyzed along with additional edaphic variables relevant to PTE accumulation in soils (e.g., pH, SOC). Concentrations of Cr, Ni, Pb and Zn, for all sites were lower than those of the risk-screening values. However, elevated concentrations of Cd and Hg observed in surface soils were associated with anthropogenic activities. Land use pattern had a significant impact on the spatial variation of PTEs. Elevated levels of Cd were uniquely associated with high phosphorus and soil organic matter (SOM) contents, and elevated Hg was associated with coal-fired power plants and historical application of fertilizer and Hg-containing pesticides. The data presented herein indicate that geogenic process likely caused a net depletion of As, Cr, Cu, Ni, Pb and Zn in topsoil, despite surface deposition from anthropogenic sources. The result of this study revealed that using subsoil concentrations of PTEs to establish background or reference concentrations might lead to an erroneous assessment of pollution levels in surface soils.
16. 题目: Enhancement of PPCPs removal by shaped microbial community of aerobic granular sludge under condition of low C/N ratio influent
The frequent occurrence of pharmaceuticals and personal care products (PPCPs) in domestic wastewater has caused great concern. In this study, the removal of two typical pharmaceuticals (Roxithromycin, ROX; Sulfamethoxazole, SMZ) in aerobic granular sludge (AGS) reactors was investigated under condition of different C/N (carbon to nitrogen) ratios. Results showed that higher removal efficiencies of ROX and SMZ (95.2 % and 92.9 %) were achieved in the AGS reactor fed with low C/N influent. Batch experiments further revealed that the removal of ROX was influenced by the adsorption ability of the AGS while SMZ removal was mainly enhanced by biodegradation process. Analysis of extracellular polymeric substances (EPS) showed that the humic acid-like substances were enriched under low C/N condition, which was in accordance with dynamic change of microbial community. The microbes, like Thauera spp. and Xanthomonadaceae, were highly enriched in the reactor with high nitrogen loading rate and functioned as refractory organics degrader. Overall, the AGS process could achieve enhanced pharmaceuticals removal performance by the regulation of microbial community under low C/N influent, which provides insights into a feasible solution for simultaneous removal of nitrogen and trace organic pollutants in AGS reactor.
17. 题目: Comprehensive investigation of the relationship between organic content and waste activated sludge dewaterability
The relationship between sludge organic fraction and its dewaterability is well known in practice. However, the formal study to reveal the underlying reason is limited. To improve understanding of the nature of organic content on sludge dewatering process, this study systematically evaluated the effects of sludge organic content on its dewaterability and revealed the underlying mechanism. Analysis of 10 waste activated sludge (WAS) samples with varying organic contents showed that capillary suction time (CST) increased linearly from 34.90 ± 0.10 s to 104.90 ± 0.30 s (R2 = 0.92, p < 0.01), whereas the solid content of centrifuge cake decreased from 21.23 %±0.45 % to 12.52 %±0.14 % (R2 = 0.89, p < 0.01) when organic fractionincreased from 35.72 % to 61.11 %. These results first confirmed that WAS dewatering performance was negatively correlated to its organic content. Then, the underlying mechanism was revealed by studying the basic physicochemical properties of WAS with various organic content. The results showed that sludge with a higher organic content generally had greater extracellular polymeric substances (EPS) content, lower density and higher negative zeta potential, which hinder the aggregation and flocculation of floc particles. These properties endow the WAS with a higher organic content generally possessed more bound water content, small pores, poorer fluidity, and stronger network strength. These characteristics can hamper the separation of water from sludge cake during dewatering. Based on which, this study discussed the potential of organic fraction as a surrogate of EPS for evaluating WAS dewaterability and indicated the organic fraction can be a useful and strong indicator of WAS dewaterability.
18. 题目: Biochar-loaded Ce3+-enriched ultra-fine ceria nanoparticles for phosphate adsorption
Biochar-loaded Ce3+-enriched ultra-fine ceria nanoparticles (Ce-BC) was prepared by a facile impregnation-precipitation-pyrolysis process and applied as adsorbents to adsorb phosphate from water. The crystal size of ceria nanoparticles in the Ce-BC was as small as 2-5 nm and the concentration of Ce3+ was high to 59.6%, which was benefited from the rapid precipitation, N2 pyrolysis atmosphere and the presence of the biochar during preparation. Ce-BC exhibited a fast adsorption kinetics for phosphate and the adsorption equilibrium could be reached within 10 min. The maximum phosphate adsorption capacity was up to 77.7 mg P g-1 at pH 3.0. Based on Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis, Ce3+ of ceria was demonstrated playing the vital role on phosphate removal and the formation of CePO4 nanocrystals was the main adsorption mechanism. This work provides a facile strategy for preparing high Ce3+ contenting materials and shows a great potential application for the phosphate removal for its high-effective and high stability.
19. 题目: Simultaneous removal of toxic ammonia and lettuce cultivation in aquaponic system using microwave pyrolysis biochar
This study examined an aquaponic approach of circulating water containing ammonia excretions from African catfish grown in an aquaculture tank for bacterial conversion into nitrates, which then acted as a nutrient substance to cultivate lettuce in hydroponic tank. We found that microwave pyrolysis biochar (450 g) having microporous (1.803 nm) and high BET surface area (419 m2/g) was suitable for use as biological carrier to grow nitrifying bacteria (63 g of biofilm mass) that treated the water quality through removing the ammonia (67%) and total suspended solids (68%), resulting in low concentration of remaining ammonia (0.42 mg/L) and total suspended solid (59.40 mg/L). It also increased the pH (6.8), converted the ammonia into nitrate (29.7 mg/L), and increased the nitrogen uptake by the lettuce (110 mg of nitrogen per plant), resulting in higher growth in lettuce (0.0562 %/day) while maintaining BOD5 level (3.94 mg/L) at acceptable level and 100% of catfish survival rate. Our results demonstrated that microwave pyrolysis biochar can be a promising solution for growing nitrifying bacteria in aquaponic system for simultaneous toxic ammonia remediation and generation of nitrate for growing vegetable in aquaculture industry.
20. 题目: Response of methane emissions to litter input manipulation in a temperate freshwater marsh, Northeast China
Plant litter plays an important role in regulating CH4 emission in wetland ecosystems. Our knowledge of the impacts of plant litter on CH4 budget is important for understanding the response and feedbacks of wetland ecosystems to climate warming. Nevertheless, the effects of plant litter on CH4 emission and temperature sensitivity (Q10) are not clear under the background of global change. In this study, a field litter inputs manipulation experiment with four treatments including no aboveground litter (NL), standing litter removal (AR), doubled litter input (DL) and controls (CK) was conducted to study the effects of litter manipulations on CH4 emission in a seasonal inundated freshwater marsh over two growing seasons of 2015 and 2016 in the Sanjiang Plain, Northeast China. Results showed that CH4 emission was significantly associated with altered litter input over the observation period. Compared with CK, the cumulative CH4 emission increased by 105.83%, 42.20% and 42.50% for NL, AR and DL treatments, respectively, in 2015, and the values were 199.04%, 115.55% and 17.55%, in 2016. Variances of CH4 emission were more sensitive to litter removal effects. Altered litter input also significantly affected the dissolved organic carbon (DOC) concentration ([DOC]) in surface pore water. DL and CK treatments with lower soil temperature had lower [DOC] than litter removal treatments of NL and AR. The abundance of methanogens among the four treatments exhibited synchronous change with DOC over the observation period. The Q10 values of CH4 emission didn't show consistent changing patterns with those of DOC among different litter input treatments, which was probably due to the different temperature sensitivity of dominant methanogen types. Due to its great effects on soil microclimate, substrate availability and the concomitant variation in temperature sensitivity, our results highlighted that plant litter effects should be incorporated into the current process-based CH4 biogeochemical models to predict future CH4 fluxes from natural wetlands under the background of global change.