121. 题目: Effective and mechanistic insights into reverse osmosis concentrate of landfill leachate treatment using coagulation-catalytic ozonation-bioaugmentation-based AnMBR
Landfill leachate membrane concentrates containing high concentrations of organics pose a major threat to the environment, and efficient treatment methods are urgent issue. In this study, a coagulation-catalytic ozonation-bioaugmentation-based anaerobic membrane bioreactor (CCOB-AnMBR) process was applied to treat reverse osmosis concentrate (ROC) of landfill leachate. Compared with polyaluminum ferric chloride (PAFC) and prefrontal cortex (PFC), coagulation using polyferric sulfate (PFS) effectively removed refractory contaminants including macro molecular organics (MMOs), benzene ring compounds (BRCs), humic acid (HA), and fulvic acid (FvA) in ROC of landfill leachate, with average 78.3%, 53.5%, 34.7% and 34.3%, respectively. Catalytic ozonation with MnOx-CeOx-Al2O3 increased the biodegradability index by degrading refractory organic compounds, which facilitated subsequent biological treatment of ROC. The oxidation of mostly occurs at the solid-liquid interface and the presence of MnOx-CeOx-Al2O3 nanocatalyst enhanced ozone decay and increased generation of hydroxyl radical (•OH) and singlet oxygen (1O2) in ROC. In addition, bioaugmentation using recombinant genetically engineered Desulfovibrio vulgaris expressing Sat and dsrAB (rGEDEV-sds) promoted metabolism of sulfate by driving transfer sulfate from the environment into the cell and sulfate dissimilation reduction process. Bioaugmentation-based AnMBR (Bio-AnMBR) caused complete degradation of the total organic carbon (TOC), enhanced degradation of leachate pollutions, and decreased the concentration of sulfate in ROC. The macro molecular organics, refractory organic contaminants, the residual coagulation-resistant substances (CRS), and heavy metal were effectively degraded in the Bio-AnMBR system. Furthermore, CCOB-AnMBR exhibits high processing efficiency in the degradation of the contaminants in ROC of landfill leachate. Overall, this excellent performance proves the feasibility and elucidates the mechanism of CCOB-AnMBR process for the removal of contaminants in ROC of landfill leachate.
122. 题目: Soil organic carbon stabilization is dominated by non-sorptive process among the subsoils from different parent material
123. 题目: Biochar as a negative emission technology: A synthesis of field research on greenhouse gas emissions
124. 题目: Influences of biochar with selenite on bacterial community in soil and Cd in peanut
Cadmium (Cd) pollution in crops seriously affects the ecosystem and human health. Effective measures should be employed to reduce the absorption and accumulation of cadmium in crops. Currently, there are many pieces of research on the application of biochar (BC) and selenium (Se) alone to the remediation of soil Cd pollution; however, few investigations have been devoted to the application of BC and Se together to the remediation of soil Cd pollution. The peanut was taken as the target crop to explore the effects of exogenous selenium and biochar on the remediation of soil Cd pollution. The response of the soil bacterial community to two levels of Cd concentration and its relationship with soil properties and Cd availability are methodically investigated. This study sets two cadmium pollution concentrations of low Cd (5 mg/ kg) and high Cd (20 mg/kg), as well as six treatments: blank, BC, soil Se, soil Se-BC, leaf Se, and leaf Se-BC. The achieved results revealed that both Se and BC could noticeably enhance the yield of peanut seeds and reduce the Cd content in peanut seeds. Among them, Se-BC treatment on soil exhibits the most influence, which reduces the Cd content by 47.86%. Se and BC also affect the physical and chemical properties of soil and remarkably magnify the content of soil available phosphorus, organic matter, soil pH, and soil conductivity. For instance, then effect is detected in the case of applying selenium biochar to soil, leading to an increase of about 64.38%, 72.62%, 2.64%, and 61.15%, respectively, and reducing the content of soil available cadmium by 21.02%. Redundancy analysis confirms that these properties enhance the abundance of dominant bacteria Actinobacteria, Proteobacteria, and Chloroflexi. The correlation analysis also indicates that Saccharimonadales, Bacillus, Arthrobacter, and other bacteria with the function of reducing the bioavailability of cadmium in soil reveal a considerable positive correlation with the variations of physical and chemical properties. In general, exogenous Se and BC incorporate to drop the content of available Cd in the soil through direct passivation, passivation caused by soil environmental change, and passivation caused by altering the soil microbial community structure; as a result, the migration and enrichment of Cd in peanut seeds are blocked and reduced. Moreover, the mixed application of BC and soil Se exhibits the best effect.
125. 题目: Contrasting controls of particulate organic carbon composition and age from riverine to coastal sediments of Eastern China Marginal Seas
Terrestrial organic carbon (OC) burial in marginal seas comprises an important marine carbon sink. However, controls on the evolution of OC during sediment transport within and beyond river basins remain poorly constrained. OC contents and isotopic compositions (δ13C and Δ14C), and specific surface areas (SSA) of river particles of the Changjiang (Yangtze River) and Huanghe (Yellow River) and surface sediments in the Eastern China Marginal Seas (ECMS) were determined to better understand controls of OC composition and age along these two major river sedimentary systems of China. Although petrogenic OC (OCpetro) content (0.02%) of particulate organic carbon (POC) in the Huanghe is lower than the Changjiang (0.09%), the radiocarbon age of Huanghe POC (4500 ± 420 yr) is significantly older than Changjiang POC (3230 ± 315 yr). Biospheric OC (OCbio) of POC in the Huanghe (0.32 ± 0.08%) is primarily derived from pre-aged soils in contrast to OCbio of Changjiang POC (0.87 ± 0.23%) - mainly from modern litter biomass. However, the age of OC in the Bohai Sea and Yellow Sea surface sediments is younger than those in the East China Sea (2335 ± 590 yr vs. 4135 ± 725 yr). Removal of most terrestrial OCbio during transport results in diagenetic aging in the Changjiang estuary (via frequent physical reworking in highly oxidized mobile-muds) and the remaining terrestrial OCbio experiences further aging during along-shore transport (i.e., transport time-associated aging). However, the continuous addition of young marine OC with little loss of the terrestrial OCbio occurs along the Huanghe system, which is mainly due to the relatively weak sediment dynamics and the high proportion of pre-aged OC in Huanghe POC. Compared with other globally significant river sedimentary systems, the evolution pattern of OC in the Huanghe system is similar to those of small mountain river-active margin systems, although it belongs to the passive margin system. By contrast, the Changjiang system acts like other large river-passive margins. Our findings further demonstrate that the alteration of OC composition and age in river sedimentary systems can be controlled by similar sediment dynamics and OC reactivities – across divergent continental margins.
126. 题目: Production of biochar from tropical fruit tree residues and ecofriendly applications – A review
Environmental contamination is considered a major issue with the growing urbanization and industrialization. In this context, the scientific society is engaged in searching for a sustainable, safe, and eco-friendly solution. Sustainable materials such as biochar play an important role in environmental contamination. It has some specific properties such as micropores which increase the surface area to bind the pollutants. This review endeavors to analyze the potential of fruit wastes especially tropical fruit tree residues as potential candidates for producing highly efficient biochar materials. The review discusses various aspects of biochar production viz. pyrolysis, torrefaction, hydrothermal carbonization, and gasification. In addition, it discusses biochar use as an adsorbent, wastewater treatment, catalyst, energy storage, carbon sequestration and animal feed. The review put forward a critical discussion about key aspects of applying biochar to the environment.
127. 题目: Soil organic matter content prediction using Vis-NIRS based on different wavelength optimization algorithms and inversion models
Visible and near-infrared reflectance spectroscopy has been proven to be an efficient method for predicting soil properties, and the wavelength optimization can improve the simulation accuracy of SOM (soil organic matter), but the best combination of wavelength optimization algorithms and inversion model is unknown for alpine ecosystem soil.
In this study, 269 topsoil samples were collected in the Three-Rivers Source Region of China and were used to build the inversion model of SOM content. Four kinds of wavelength optimization algorithms were conducted, i.e., correlation analysis, uninformative variable elimination (UVE), successive projection algorithm, and competitive adaptive reweighted sampling (CARS) after spectral pre-treatments. Then, partial least squares regression, support vector machine, and random forest (RF) were used to develop the inversion model of SOM content. Various combinations of wavelength optimization algorithms and inversion models were constructed, and the accuracies were compared.
The combination of the UVE-CARS-RF achieved the highest simulation accuracy (R2 = 0.902, RPD = 3.218). For the single band selection method, the CARS algorithm has the highest simulation accuracy, especially the combination of CARS-RF (R2 = 0.899, RPD = 3.133).
Appropriate combination of the wavelength optimization algorithm and inversion model not only can significantly reduce computational load but improve the prediction precision. In total, RF obtained the best predication effect.
128. 题目: Effects of coastal wetland reclamation on soil organic carbon, total nitrogen, and total phosphorus in China: a meta-analysis
129. 题目: Organic matter degradation determines the concentrations of polybrominated diphenyl ethers in sediments. Multivariate learning on environmental and experimental models
Sediment organic matter (SOM) plays an important role in capturing polybrominated diphenyl ethers (PBDEs) due to its affinity to hydrophobic and lipophilic compounds. Previous publications about correlations between PBDE concentrations and SOM content showed discrepancies among the results, reporting either significant positive correlations or no correlations at all. This work aimed to provide a deeper insight into SOM characteristics that might determine the concentrations of PBDEs in sediments. Sediment samples from Mendoza province, Argentina, were analyzed to contrast two models, environmental and experimental, using multivariate learning methods. Mendoza has been going through increasing events of drought and water scarcity, hence the occurrence, transport, and fate of contaminants as PBDEs in aquatic environments is of superlative importance. Principal component analysis (PCA) and partial least squares regression (PLS) were used to evaluate the correlations between physicochemical properties of sediments, semi-quantitative Fourier transform infrared (FTIR) area ratios obtained from SOM spectra, and PBDE concentrations in sediments. Moreover, a linear model was proposed to determine SOM density using FTIR area ratios and it was used as an additional variable in multivariate analyses. The results obtained from PCA and PLS were consistent and revealed that PBDE concentrations in sediments were correlated with a more degraded SOM, characterized by shorter and more branched hydrocarbon chains. PBDE concentrations were also correlated with higher SOM density values, which in turn were correlated with SOM degradation. These findings extend previous understanding and emphasize that not only is the organic matter content a factor in determining PBDE concentrations in sediments, but also and more significantly, its degree of degradation.
130. 题目: Sludge-based activated biochar for adsorption treatment of real oil sands process water: Selectivity of naphthenic acids, reusability of spent biochar, leaching potential, and acute toxicity removal
Large volumes of oil sands process water (OSPW) containing naphthenic acids (NAs) and other contaminants are generated by oil sands operations. For the first time, pristine and zinc chloride-activated biochars from sludge from a municipal wastewater treatment plant are studied in the adsorption of NAs in real OSPW. By using activated biochar instead of pristine biochar, the adsorption capacity (qt) for total NAs (classical and oxidized NAs) increased from 2.3 to 26.6 mg/g. The increase in qt for activated biochar was related to the improvement of surface area from 7.9 to 513 m2/g, the abundance of mesopores (89% of pore volume), and the oxygen-containing surface groups. Equilibrium was reached at 2 h of contact time. Considering the thousands of structures of NAs in the OSPW, the activated biochar presented higher affinity for NAs with higher carbon and double bond equivalency numbers, therefore, NAs with more hydrophobic and higher cyclicity characteristics. Pore-filling, hydrogen bonding, and π-π interactions are the adsorption mechanisms. Thermal regeneration of spent activated biochar was studied, and in the fifth cycle of regeneration, the regenerated biochar had qt of 7.1 mg/g, which was 5 times higher than the adsorption capacity of fresh pristine biochar. Adsorption treatment of OSPW using activated biochar decreased the following parameters: metals Mg (7%), Ca (21%), Sr (27%), and Ba (60%), organic matter by means of DOC (63%) and COD (66%), acute toxicity towards V. fischeri (66%) and bioavailability of organics (91%). These findings promote circular economy as it presents an efficient adsorbent for NAs in OSPW developed from sludge, reducing the environmental impact associated with sludge disposal and allowing the efficient reclamation and reuse of OSPW.
131. 题目: Insight into mechanisms of biochar-fertilizer induced of microbial community and microbiology of nitrogen cycle in acidic soil
Biochar has been shown to affect the nitrogen (N) cycle in soil, however, it is unknown how this occurs. Therefore, we used metabolomics, high-throughput sequencing, and quantitative PCR to explore biochar and nitrogen fertilizer effects on the mitigation mechanisms of adverse environments in acidic soil. In the current research, we used acidic soil and maize straw biochar (pyrolyzed at 400 °C with limited oxygen). Three maize straw biochar levels (B1; 0t ha−1, B2; 45 t ha−1, and B3; 90 t ha−1) along with three N fertilizer (urea) levels (N1; 0 kg ha−1, N2; 225 kg ha−1 mg kg−1, and N3; 450 kg ha−1 mg kg−1) were employed in a sixty-day pot experiment. We found that the formation of NH+ 4-N was faster at 0–10 days, while the formation of NO- 3-N occurred at 20–35 days. Furthermore, the combined application of biochar and N fertilizer most effectively boosted soil inorganic N contents compared to biochar and N fertilizer treatments alone. The B3 treatment increased the total N and total inorganic N by 0.2–24.2% and 55.2–91.7%, respectively. Soil microorganism, N fixation, and nitrification capabilities increased with biochar and N fertilizer addition in terms of N-cycling-functional genes. Biochar-N fertilizer had a greater impact on the soil bacterial community and their diversity and richness. Metabolomics revealed 756 distinct metabolites, including 8 substantially upregulated metabolites and 21 significantly downregulated metabolites. A significant amount of lipids and organic acids were formed by biochar-N fertilizer treatments. Thus, biochar and N fertilizer triggered soil metabolism by affecting bacterial community structure, and N-cycling of the soil micro-ecological environment.
132. 题目: Catalytic mechanism of N-containing biochar on volatile-biochar interaction for the same origin pyrolysis
Nitrogen, as a common element, is widely present in biomass. The effects of nitrogenous substances on the same origin pyrolysis of biomass and the consequences of N-containing biochar on the catalytic process of volatiles are important for further analyzing the pyrolysis mechanism of biomass. In this research, N-containing biochar was prepared under different conditions, and the interaction between N-containing biochar and biomass pyrolysis volatiles at 400–700 °C was studied. The results show that N-containing biochar can simultaneously participate in reactions as adsorbents, catalysts, and reactants. Its catalytic effect is obviously different for various N configurations. Pyridinic N and pyrrolic N can promote the cracking of lignin into methoxy phenol compounds and promote the further cracking of 5-hydroxymethylfurfural. Graphitic N and oxidized N can promote the further decomposition of phenol and the conversion of D-xylose into small-molecule ketones. In addition, oxidized N can also inhibit the cracking of lignin to produce guaiacol. In the long-term interaction, the highly active pyridinic N tends to convert to a more stable graphitic N.
133. 题目: OrgAlkCalc: Estimation of organic alkalinity quantities and acid-base properties with proof of concept in Dublin Bay
The presence and influence of organic species is generally omitted in total alkalinity (TA) analysis. This has direct implications to calculated carbonate system parameters and to key descriptors of ocean acidification, especially in coastal waters where organic alkalinity (OrgAlk) can contribute significantly to TA. As titratable charge groups of OrgAlk can act as unknown seawater acid-base systems, the inclusion of the total concentration and apparent dissociation constants of OrgAlk in carbonate calculations involving TA is required to minimise uncertainty in computed speciation. Here we present OrgAlkCalc, an open-source Python based programme that can be used in conjunction with simply modified Global Ocean Acidification Observing Network (GOA-ON) TA titration apparatus to measure TA and OrgAlk, as well as return estimations of associated acid-base properties. The modified titration apparatus and OrgAlkCalc were tested using samples collected from the transitional waters of Dublin Bay, Ireland over a 8 month period (n = 100). TA values ranged from 2257 to 4692 μmol·kg−1 and indicated that freshwater inputs pose a significant source of carbonate alkalinity to Dublin Bay. OrgAlk values ranged from 46 to 234 μmol·kg−1 and were generally observed to be higher in more saline waters, with elevated levels in the Autumn/Winter period. The dissociation constants of two distinct OrgAlk charge groups were identified, with pK values in agreement with previously reported values for humic substances. The majority of OrgAlk charge group concentrations were associated with carboxyl-like charge groups.
134. 题目: Spectroscopic fingerprints profiling the polysaccharide/protein/humic architecture of stratified extracellular polymeric substances (EPS) in activated sludge
Extracellular polymeric substances (EPS), with a stratified structure including tightly-bound EPS (TB-EPS), loosely-bound EPS (LB-EPS), and soluble EPS (S-EPS) surrounding the microbial cells, are known to vitally affect the physicochemical and biological functions of activated sludge in wastewater treatment. Polysaccharides (PS), proteins (PN), and humic acids (HA) are key components of EPS but their roles in constructing the multi-layer architecture are still unclear. This study explored the EPS characteristics in relation to the components using spectroscopic fingerprinting techniques. Ultraviolet-visible (UV-vis) spectra demonstrated stark difference between TB-EPS and other EPS. Fluorescence excitation-emission matrix (FEEM) and apparent quantum yield revealed further detailed differences. Fluorescence quotient analysis highlighted the dominance of TB-EPS, LB-EPS, and S-EPS in the excitation/emission wavelength (Ex/Em) region of Em = 350–400 nm, Em > 400 nm, and low-Stokes shift band (Em − Ex < 25 nm), respectively. Wavelength-wise prediction of the FEEM intensity was achieved through multiple linear regression against the chemical composition and variance partitioning analysis witnessed binary interactions of PS × HA and PS × PN in S-EPS, PN × HA and PS × PN in LB-EPS, and ternary interaction of PS × PN × HA in TB-EPS as well as the wavelength-specific fluorescence responses of these interactions. Further, X-ray photoelectron spectroscopy, infrared spectra, and circular dichroism corroborated the differences in primary, secondary, and tertiary structures across the EPS layers. Ultrahigh-performance liquid chromatography-mass spectrometry detected molecular fragments confirming the multi-component hybridization among PS, PN, and HA. This study demonstrates a spectroscopic approach to sensitively fingerprint the fine structure of EPS, which has the potential for rapid monitoring of EPS and related sludge properties in wastewater treatment systems.
135. 题目: The contradictory roles of tightly bound and loosely bound extracellular polymeric substances of activated sludge in trimethoprim adsorption process
Extracellular polymeric substances (EPS) of activated sludge are a mixture of high molecular weight polymers secreted by microorganisms, which have the double structure of tightly-bound EPS (TB-EPS) in inner layer and loosely-bound EPS (LB-EPS) in outer layer. The characteristic of LB- and TB-EPS were different, which would affect their adsorption of antibiotics. However, the adsorption process of antibiotics on LB- and TB-EPS was still unclear yet. Therefore, in this work, the roles of LB-EPS and TB-EPS in adsorption of a typical antibiotic-trimethoprim (TMP) at environmentally relevant concentration (25.0 μg/L) were investigated. The results showed the content of TB-EPS was higher than that of LB-EPS, which was 17.08 and 10.36 mg/g VSS, respectively. The adsorption capacity of raw, LB-EPS extracted and both LB- and TB-EPS extracted activated sludges for TMP were 5.31, 4.65 and 9.51 μg/g VSS, respectively, which indicated LB-EPS had positive effect on TMP removal, while TB-EPS had negative effect. The adsorption process can be well described by a pseudo-second-order kinetic model (R2 > 0.980). The ratio of different functional groups was calculated and the CO and C–O bond might be responsible for the adsorption capacity difference between LB- and TB-EPS. The fluorescence quenching results indicated that tryptophan protein-like substances in LB-EPS provided more binding sites (n = 0.36) than that of tryptophan amino acid in TB-EPS (n = 0.1). Furthermore, the extend DLVO results also demonstrated that LB-EPS promoted the adsorption of TMP, while TB-EPS inhibited the process. We hope the results of this study were helpful for understanding the fate of antibiotics in wastewater treatment systems.
136. 题目: Revealing the potential of organo-mineral complexes in agricultural application using bibliometrics
Organo-mineral complexes (OMCs) are referred to as biogeochemical black boxes and are widely thought to contribute to the long-term preservation of organic matter. However, the history and potential research directions of OMC research, as well as the deep applications of OMCs, have not been fully investigated. We conducted a comprehensive bibliometric study based on the Science Citation Index core database publications from 1959 to 2020 to fill this research gap in OMC studies. The results showed that a total of 751 publications involving OMCs (OMCPs) were published. There was a significant positive correlation between the frequency of international associations and the number of OMCPs. A dendrogram containing six categories and 130 keywords was constructed to represent the research content of OMCPs. In particular, the keyword co-occurrence analysis and a laboratory-scale practice jointly verified the feasibility of using silicate minerals and manure compost to produce synthetic OMCs. The life span prediction analysis revealed that the research on OMCs is in the climax stage, while the current number of studies is still less than 50% of the saturation amount. The two most potentially promising research directions are the use of OMCs in agriculture and pollutant control, which currently account for less than 30% and 25% of the saturation amount, respectively. This report clarified the research gap and predicted the development trend of OMC research using bibliometrics for the first time, and highlighted the importance of OMCs in improving agricultural production while stabilizing pollutant migration in agricultural soil.
137. 题目: Novel Fe/N co-doping biochar based electro-Fenton catalytic membrane enabling enhanced tetracycline removal and self-cleaning performance
Designing a highly-active electro-Fenton (EF) catalytic membrane without the additional chemicals and iron sludge formation was a challenge for antibiotics treatment. In this study, we constructed Fe/N co-doping biochar (Fe-g-C3N4/biochar) based ultrafiltration membranes for degradation of tetracycline (a common antibiotic) and membrane fouling control under electro-assistance. The results showed that membranes presented high electro-Fenton catalytic activity because the presence of rich oxygen functional groups (high C–O/CO ratio) and nitrogen species (pyridinic N and pyrrolic N) promoted H2O2 generation and accelerated Fe(III)/Fe(II) cycle. Moreover, H3PO4 activation of biochar endowed the EF catalytic membrane with higher electrocatalytic activity, while it was opposite using biochar with higher pyrolysis temperature (600–700 °C). In particular, owing to the oxidative degradation by electro-generated •OH and •O2−, Fe-g-C3N4/ABC-600/Graphite/PVDF (600 represented the pyrolysis temperature) membrane presented 100% tetracycline removal within 0.749 min of residence time, excellent self-cleaning performance (flux recovery = 100%) at neutral pH and low energy consumption (0.199 W·h/L) for the reclamation of synthetic municipal wastewater effluent. In addition, membrane self-cleaning mechanism was closely related to the synergy between partial mineralization and reduced fouling potential of foulants. Besides, the EF membrane also exhibited good reusability and stability, which was promising to apply in antibiotics removal.
138. 题目: Soil carbon sequestration in paddy field and its simultaneous mineralization to supply available nutrients for the crops are affected by no-tillage with straw management: A meta-analysis
No-tillage with straw management is an effective method to improve soil organic carbon (SOC) storage and to sustain soil health, but the impact of tillage with straw management on carbon (C) sequestration remains inconclusive. Therefore, a meta-analysis was conducted based on 319 observations from 95 research publications to assess the relevant effect of no-tillage with straw management on SOC storage and its mineralization. The results indicated that no-tillage significantly increases SOC and microbial biomass carbon (MBC), dehydrogenase (DHA), β-glucosidase (BG), and alkaline phosphatase (AlP), while significantly decreases global warming potential (GWP). The SOC is positively correlated to MBC, total nitrogen (TN), BG, and methane (CH4) emissions under no-tillage practice. SOC increases more over the treatment duration, particularly reaches a much higher level within the medium-term (5–10 years) under no-tillage practice. The response of SOC exhibits significant variations with a reduction from upper to lower soil layers under no-tillage when straw retention is only considered. We also found that no-tillage can promote SOC storage by increasing microbial biomass regardless of whether straw is removed, while the increment of SOC, owing to its simultaneous more mineralization under straw retention is lower than that under straw removal. Our findings suggest that no-tillage with straw management facilitates SOC storage and also provides more available nutrients for crop uptake and microbial utilization.
139. 题目: Phosphorus release characterization of biochar loaded with inherent and exogenous phosphorus and impact on soil Pb immobilization
Phosphorus (P)-laden biochar has been widely used for environmental lead (Pb) remediation, but the P release risk and their adsorption and immobilization effect on soil potentially toxic elements (PTEs) between inherent P-laden biochar and exogenous P-laden biochar are rarely investigated. In this study, two biochars loaded with low and moderate inherent P (LPIB and MPIB) and two biochars loaded with moderate and high exogenous P (MPEB and HPEB) were produced by wheat straws with total P concentrations of 2.53, 4.71, 5.24, and 10.8 mg g−1, respectively. Water-extractable P was dominated in LPIB (49.5%), MPIB (35.9%), and MPEB (42.1%), while residual P was predominant in HPEB (43.5%). Meanwhile, labile P in MPEB (3002 mg kg−1) was 1.32 times higher than that in MPIB (2272 mg kg−1). Maximum P release capacity followed the order: LPIB (1.53 mg g−1) < MPIB (2.13 mg g−1) < MPEB (2.65 mg g−1) < HPEB (4.37 mg g−1), which was more suitable for the pseudo-second-order model. Lower pH, common anions (Cl−, NO3−, SO42−, HCO3−) and cations (Na+, K+) significantly promoted P release from biochar, but Ca2+ and Mg2+ inhibited P release. Langmuir sorption isotherms were better fitted the sorption of Pb2+ by the four biochars and the maximum adsorption capacities followed the order of HPEB (116 mg g−1) > LPIB (105 mg g−1) ≈ MPEB (104 mg g−1) ≈ MPIB (103 mg g−1). Four biochars applications significantly increased soil pH by 0.66–0.68 and decreased CaCl2-extractable Pb and exchangeable Pb by 72.1–92.7% and 27.3–33.0%, promoting Pb bounding to carbonate and organic matter by 57.2–60.9% and 367–467%, respectively. HPEB application increased labile P by 25.6% and 37.2% compared to MPIB and MPEB applications. This study implies that biochar loaded with exogenous P has higher P release risk than that loaded with inherent P when they have similar Pb adsorption and immobilization effects.
140. 题目: Slash and burn management and permanent or rotation agroforestry systems: A comparative study for C sequestration by century model simulation
Understanding the effects of agroforestry systems (AFs) on soil organic carbon (SOC) requires long-term experiments, but scenarios simulations can anticipate the potential of these systems to sequester or lose carbon (C). This study aimed to simulate the SOC dynamics in slash and burn management (BURN) and AFs using the Century model. Data from a long-term experiment implemented in the Brazilian semiarid region were used to simulate SOC dynamics under BURN and AFs situations, and the natural vegetation (NV) “Caatinga” as a reference. BURN scenarios considered different fallow periods (0, 7, 15, 30, 50 and 100 years) among cultivation of the same area. The two types of AFs (agrosilvopastoral-AGP and silvopastoral-SILV) were simulated in two contrasting conditions: (i) each one of the AFs and also NV area were permanently conducted with no rotation among these areas; and (ii) the two AFs and NV rotated among them every 7 years. The correlation coefficients (r), coefficients of determination (CD) and coefficients of residual mass (CRM) showed adequate performance, meaning that the Century model is able to reproduce the SOC stocks in the slash and burn management and AFs situations. The equilibrium points of NV SOC stocks stabilized around 30.3 Mg ha−1, as similar to the measured average of 28.4 Mg ha−1 at field conditions. The adoption of BURN without a fallow period (0 years) resulted in a reduction of 50% of SOC, approximately 20 Mg ha−1, after the first 10 years. Permanent (p) and rotating (r) AFs management systems recovered (in 10 years) fast to the original SOC stocks, resulting in higher SOC stocks than NV SOC at equilibrium. The fallow period of 50 years is necessary to recovery SOC stocks in the Caatinga biome. The simulation shows that the AFs systems increase more SOC stocks than observed in natural vegetation in long-term.