21. 题目: Interactions of Moisture Content, pH, and HA on the Immobilization of Pb and Zn in Paddy Soil Using Magnetic-chitosan Hydrochar
期刊: Water, Air, & Soil Pollution
作者: Ming Wu, Yitong Dan, Jing Miao, Xiaoxia Wang, Feihong Liu, Wenjing Sang
摘要: The pollution of composite heavy metals in paddy soil is a challenging issue, and there is little information on the interactions of typical environmental factors on hydrochar in-situ remediation of composite heavy metals. In the current research, the effects of three different environmental factors (moisture content, pH, and dissolved organic matter (DOM)) on magnetic-chitosan hydrochar (MCH) in-situ immobilized Pb and Zn in paddy soil with European Community Bureau of Reference (BCR) extraction method were investigated. Next, the interactions between different moisture content (70% and 100%), initial soil pH (6.5 and 8.0), and humic acid (HA) dosage (5% and 10%) were assessed using a second-order polynomial nonlinear fitting model. The BCR results indicated that increasing soil moisture content and pH successfully transformed exchangeable Pb and Zn into stable Pb and Zn and improved the immobilization efficiency of MCH for Pb and Zn. Besides, the percentage of residual Pb and Zn increased significantly as HA dosage increased from 0 to 5% after 60 days. However, there was an unremarkable change of residual Pb and Zn at 5% HA (65.8%, 67.9%) and 10% HA (65.2%, 65.9%), which indicated that 5% HA dosage was the most efficient. According to the fitting model, HA had a major impact on the growth rate of MCH-immobilized Pb and Zn. Additionally, there were great synergistic interactions among three factors in the immobilization of Pb and Zn using MCH. In particular, 5% HA promoted surface complexation, ion exchange, electrostatic adsorption, surface complexation, and precipitation, resulting in nearly 56.58% Pb and 37.66% Zn that were transformed from exchangeable into stable forms under high moisture and neutral conditions. In summary, HA played a crucial role in the process of MCH-immobilized Pb and Zn in soil, and there were synergistic interactions on the effective immobilization of Pb and Zn in paddy soil among HA and moisture content and initial pH.
22. 题目: Examining the influence of bare soil UAV imagery combined with auxiliary datasets to estimate and map soil organic carbon distribution in an erosion-prone agricultural field
期刊: Science of The Total Environment
作者: James Kobina Mensah Biney, Jakub Houška, Jiří Volánek, David Kwesi Abebrese, Jakub Cervenka
摘要: Soil organic content (SOC), an indicator of soil fertility, can be estimated quickly and accurately with remote sensing (RS) datasets; however, the issue of vegetation cover on the field still remains a major concern. In order to minimize the effects of vegetation cover, studies relating reflectance spectra to SOC may require bare soil. However, acquiring satellite images devoid of vegetation is still an enormous challenge for RS techniques. This is because the area that may have been accurately predicted at a targeted date is sometimes limited since many pixels are covered by vegetation. The study goal was to assess the impact of using UAV-borne imagery coupled with auxiliary datasets, which include spectral indices (SPIs) and terrain attributes (TAs) (at 20 cm and 30 m resolution), singly or merged, to estimate and map SOC in an erosion-prone agricultural field. Both field samples and UAV imagery were acquired while the fields were bare. Using a grid sampling design, 133 soil surface samples were collected. The models used include partial least square regression (PLSR), extreme gradient boosting (EGB), multivariate adaptive regression splines (MARS), and regularised random forest (RFF). The models were evaluated using the root mean squared error (RMSE), the coefficient of determination (R2), ratio of performance to interquartile distance (RPIQ), and the mean absolute error (MAE). For prediction, the three merged datasets (R2val = 0.86, RMSEval = 0.13, MAEval = 0.11, RPIQval = 4.19) outperformed the best separate dataset (R2val = 0.82, RMSEval = 0.15, MAEval = 0.10, RPIQval = 2.08). Though all datasets detected both low and high estimates of soil SOC, the three merged datasets with EGB showed a less extreme prediction error. This study demonstrated that SOC can be estimated with high accuracy using completely bare soil UAV imagery with other auxiliary data, and it is thus highly recommended.
23. 题目: Performance Enhancement of Biogenetic Dulfidated Zero-Valent Iron for Trichloroethylene Degradation: Role of Extracellular Polymeric Substances
期刊: Environmental Science & Technology
作者: Anqi Wang, Jun Hou, ChunMei Tao, Lingzhan Miao, Jun Wu, Baoshan Xing
摘要: Chemical sulfidation has been considered as an effective strategy to improve the reactivity of zero-valent iron (S-ZVI). However, sulfidation is a widespread biogeochemical process in nature, which inspired us to explore the biogenetic sulfidation of ZVI (BS-ZVI) with sulfate-reducing bacteria (SRB). BS-ZVI could degrade 96.3% of trichloroethylene (TCE) to acetylene, ethene, ethane, and dichloroethene, comparable to S-ZVI (97.0%) with the same S/Fe ratio (i.e., 0.1). However, S-ZVI (0.21 d–1) exhibited a faster degradation rate than BS-ZVI (0.17 d–1) based on pseudo-first-order kinetic fitting due to extracellular polymeric substances (EPSs) excreted from SRB. Organic components of EPSs, including polysaccharides, humic acid-like substances, and proteins in BS-ZVI, were detected with 3D-EEM spectroscopy and FT-IR analysis. The hemiacetal groups and redox-activated protein in EPS did not affect TCE degradation, while the acetylation degree of EPS increased with the concentration of ZVI and S/Fe, thus inhibiting the TCE degradation. A low concentration of HA-like substances attached to BS-ZVI materials promoted electron transport. However, EPS formed a protective layer on the surface of BS-ZVI materials, reducing its TCE reaction rate. Overall, this study showed a comparable performance enhancement of ZVI toward TCE degradation through biogenetic sulfidation and provided a new alternative method for the sulfidation of ZVI.
24. 题目: Linking pharmaceutical residues to dissolved organic matter and aquatic bacterial communities in a highly urbanized bay
期刊: Science of The Total Environment
作者: Ziyan Ke, Jianfeng Tang, Lei Yang, Jing Sun, Yaoyang Xu
摘要: Pharmaceuticals are causing environmental concerns associated with their widespread distribution in aquatic ecosystems. The environmental fate and behavior of pharmaceutical residues are related to dissolved organic matter and bacterial communities, both of which are strongly influenced by human activities. However, the relationships among pharmaceutical pollution, dissolved organic matter pool, and bacterial community structure under the pressure of human activities are still unclear, especially in highly urbanized bay areas. In this study, we investigated the occurrence and distribution of 35 pharmaceuticals in a typical urbanized bay (Hangzhou Bay) in Eastern China, and analyzed their relationships with dissolved organic matter and aquatic bacterial community structure. The target pharmaceuticals were ubiquitously detected in surface water samples, with their concentrations ranging from undetectable to 263 ng/L. The detected pharmaceuticals were mostly sulfonamides, macrolides, antidepressants, and metabolites of stimulants. Significant positive correlations were observed between the concentrations of pharmaceuticals and the intensity of human activities. Strong correlations also emerged between the concentration of antidepressants and the speed of urban expansion, as well as between the concentration of cardiovascular drugs and the population density or nightlight index. Three fluorescent components (protein-like C1, terrestrial humic-like C2, protein tryptophan-like C3) were significantly positively correlated with the total concentration of pharmaceuticals. Pharmaceutical pollution reshaped aquatic bacterial communities, based on the close correlation observed between pharmaceutical concentration and bacterial community structure. The results elucidate the potential dynamics of dissolved organic matter pool and aquatic bacterial communities in response to pharmaceutical pollution in urbanized bay ecosystems.
25. 题目: Iron–organic carbon associations stimulate carbon accumulation in paddy soils by decreasing soil organic carbon priming
期刊: Soil Biology and Biochemistry
作者: Xun Duan, Zhe Li, Yuhong Li, Hongzhao Yuan, Wei Gao, Xiangbi Chen, Tida Ge, Jinshui Wu, Zhenke Zhu
摘要: Iron-bound organic carbon (Fe-OC) complexes are important for stabilizing soil organic carbon (SOC) against biodegradation. However, it is unclear how the stabilization of OC and its release from Fe minerals subsequently affect the priming effect on SOC mineralization. To address the knowledge gap, we incubated typical paddy soil for 60 days by adding 2-line ferrihydrite (2LFh) or 6-line Fh (6LFh)-bound glucose, each with both high and low amounts of glucose, under anaerobic conditions. Approximately 21% more CO2 was derived from 2LFh-bound glucose than from 6LFh-bound glucose. Glucose addition alone stimulated SOC mineralization and caused a positive priming effect (0.27% of SOC). In contrast, 2LFh- and 6LFh-bound glucose inhibited SOC mineralization to both CO2 and CH4 and subsequently induced a negative priming effect, ranging from −0.33% to −0.55% SOC. Compared to 2LFh-bound glucose, 6LFh-bound glucose induced a lower priming effect on CO2 emissions (2-fold lower), which was attributed to the lower Fe-reduction rate of 6LFh and OC released. In addition, the available nutrients adsorbed by 6LFh were more difficult to release than those by 2LFh, which aggravated microbial nutrient limitation, and further decreased microbial activity. The priming effect for CH4 emissions was directly proportional to the glucose level loaded. The Fe reduction rates were higher in Fh-bound high amount of glucose than that in the Fh-bound low amount of glucose, which subsequently provided more available C sources for methanogens. Thus, Fe minerals have a high capacity for SOC accumulation, as they prevent bound OC from mineralization and decrease native SOC priming. Moreover, the protection of SOC by Fe minerals depended on its crystalline structure and the amount of OC loading. Our results show that promoting the transformation from weakly crystalline Fe oxides to more crystalline forms would increase SOC accumulation and stability over the complete rice-growing period.
26. 题目: Spatial predictors and temporal forecast of total organic carbon levels in boreal lakes
期刊: Science of The Total Environment
作者: Camille Crapart, Anders G. Finstad, Dag O. Hessen, Rolf D. Vogt, Tom Andersen
摘要: Browning of Fennoscandian boreal lakes is raising concerns for negative ecosystem impacts as well as reduced drinking water quality. Declined sulfur deposition and warmer climate, along with afforestation, other climate impacts and less outfield grazing, have resulted in increased fluxes of Total Organic Carbon (TOC) from catchments to freshwater, and subsequently to coastal waters. This study assesses the major governing factors for increased TOC levels among several catchment characteristics in almost 5000 Fennoscandian lakes and catchments. Normalized Difference Vegetation Index (NDVI), a proxy for plant biomass, and the proportions of peatland in the catchment, along with surface runoff intensity and nitrogen deposition loading, were identified as the main spatial predictors for lake TOC concentrations. A multiple linear model, based on these explanatory variables, was used to simulate future TOC concentration in surface runoff from coastal drainage basins in 2050 and 2100, using the forecasts of climatic variables in two of the Shared Socio-economic Pathways (SSP): 1-2.6 (+2 °C) and 3-7.0 (+4,5 °C). These scenarios yield contrasting effects. SSP 1-2.6 predicts an overall decrease of TOC export to coastal waters, while SSP 3-7.0 in contrast leads to an increase in TOC export.
27. 题目: Smoldering fire impacts on pore water quality of disturbed peatland soils
期刊: Science of The Total Environment
作者: Haojie Liu, Dominik Zak, Nerijus Zableckis, Antje Cossmer, Nicole Langhammer, Björn Meermann, Bernd Lennartz
摘要: Climate change may increase the overall susceptibility of peatlands to fire. Smoldering fires in peatlands can cause substantial emissions of greenhouse gases. It is, however, less clear how smoldering affects the soil pore water quality. In this study, soil samples were collected from agricultural fen and disturbed bog study sites in Germany and Lithuania to quantify the effect of peat burning on pore water composition. The samples were air dried and smoldered under ignition temperature (approximately 200 °C) with different durations (0, 2, 5, and 10 h). Pore water samples were extracted from the soil to determine dissolved organic carbon (DOC) concentrations, dissolved organic matter (DOM) fractions, fluoride, extractable organically bound fluorine (EOF), and sulfate concentrations. The results showed that soil smoldering changes the peat pore water chemistry and that changes differ between fens and bogs. The smoldering duration is likewise influential. For fen grasslands, 2 and 5 h of smoldering of peat caused a >10-fold increase in DOC (up to 1600 mg L−1) and EOF concentrations. The fluoride (up to 60 mg L−1) and sulfate concentrations substantially exceeded WHO drinking water guidelines. In contrast, the temperature treatment decreased the DOC concentrations of samples from raised bogs by 90 %. The fluoride concentrations decreased, but sulfate concentrations increased after smoldering of the bog samples. DOC, fluoride, and sulfate concentrations of bogs varied significantly between the smoldering duration treatments. For all peat samples, the extracted DOM was dominated by humic-like substances before smoldering, but the fraction of low molecular weight substances increased after smoldering combustion. In conclusion, smoldering alters the biogeochemical processes in both peatland types and possibly impair the water quality of adjacent water resources especially in fen peat landscapes.
28. 题目: Does biocide treatment for mosquito control alter carbon dynamics in floodplain ponds?
期刊: Science of The Total Environment
作者: Caroline Ganglo, Clara Mendoza-Lera, Alessandro Manfrin, Rossano Bolpagni, Verena Gerstle, Sara Kolbenschlag, Eric Bollinger, Ralf Schulz, Andreas Lorke
摘要: Shallow lentic aquatic ecosystems, such as ponds, are important repositories of carbon (C) and hotspots of C cycling and greenhouse gas emission. Tube-dwelling benthic invertebrates, such as chironomids, may be key players in C dynamics in these water bodies, yet their role in the C-budget at ecosystem level remains unclear. We tested whether a 41 % reduction in chironomid abundance after application of the mosquito control biocide Bacillus thuringiensis israelensis (Bti) had implications for the C-fluxes to the atmosphere, C-pools, and C-transformations (i.e. organic matter decomposition) in ponds. Data were collected over one year in the shallow, deep and riparian zones of 12 experimental floodplain pond mesocosms (FPMs), half of them treated with Bti. The C-fluxes were measured as CO2 and CH4 emissions, atmospheric deposition, and emerging insects. Pools of C were measured as dissolved inorganic and organic C in surface and porewater, sediment organic C, plants, and macroinvertebrate biomass. Despite seasonal variability, treated FPMs, for which higher CH4 emissions have been reported, showed a trend towards less dissolved organic C in porewater, while no effect was observed for all remaining components of the C budget. We attribute the effect of Bti on the C budget to the reduction in macroinvertebrates biomass, the increase in CH4 emissions, and the input of C from the Bti excipient. This finding suggests that changes in tube-dwelling macroinvertebrates have a weak influence on C-cycling in ponds and confirms the existence of long-lasting effects of Bti on specific components of C budgets.
29. 题目: Experimental drought increased the belowground sink strength towards higher topsoil organic carbon stocks in a temperate mature forest
作者: Melanie Brunn, Jaane Krüger, Friederike Lang
摘要: Reduced carbon assimilation by trees is often considered to lower the overall carbon sink function of drought-stressed forests. However, soil organic carbon (SOC) stocks may respond differently to drought than ecosystem carbon flux dynamics, leading to imprecise predictions of soil carbon sequestration when one value is inferred from the other. As a major component of soil organic matter, SOC is the largest actively cycling terrestrial carbon reservoir, and thus fulfills various important ecosystem services. Yet, there is uncertainty about how SOC quantity and quality respond to drought in temperate forests. This study addressed the depth distribution of SOC stocks and soil organic matter stability in a forest exposed to artificial drought for five consecutive growing seasons below clusters of temperate mature deciduous beech (Fagus sylvatica L.) and coniferous spruce (Picea abies (L.) Karst.). In addition to SOC stock determination, we measured concentrations of water-extractable organic carbon (WEOC), performed density fractionation, and determined beta values of SOC (slopes of linear regressions between δ13C of soil and log-transformed SOC content throughout soil depth profiles). Following drought, SOC stocks down to 30 cm depth increased by a factor of 1.5 under P. abies while they did not change with drought under F. sylvatica. Under both species, SOC stocks in the mineral topsoil (0–5 cm soil depth) increased by >80 % with drought, increasing the relative contribution of this thin depth section to total SOC from 5 % to >30 %. At 5–15 cm soil depth, SOC stocks decreased with drought under F. sylvatica but not under P. abies. With drought, carbon in the free light fraction (fLF) increased under F. sylvatica but declined marginally under P. abies. Results from density fractionation and beta values suggest decreased soil organic matter stability under F. sylvatica and increased stability under P. abies. Greater SOC accumulation suggests that the belowground carbon sink strength of drought-stressed forests increases, which contrasts with reduced ecosystem carbon uptake under drought.
30. 题目: Effects of regional climate, hydrology and river impoundment on long-term patterns and characteristics of dissolved organic matter in semi-arid northern plains rivers
期刊: Science of The Total Environment
作者: Md Noim Imtiazy, Kristine Hunter, Jeff Sereda, Leah Dirk, Jeff J. Hudson
摘要: Diverse environmental and anthropogenic factors, such as the ongoing reservoir constructions may influence riverine dissolved organic matter (DOM) properties. This has important implications for river water quality, particularly when reservoirs are a source of drinking water. Simultaneous studies of multidecadal trends in dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) are scarce. We studied the patterns in DOC and DON concentration in two major rivers of the South Saskatchewan River (SSR) basin over a 42-year period (1978–2019). We also examined the impact of a large reservoir on riverine DOC properties. Contrary to many studies, we did not find a long-term increase in DOC and DON concentration, and DOC and DON patterns were not always synchronous. In an agriculture dominated watershed like the SSR basin, agricultural land use (e.g., nitrogen-fertilizer application) could influence DOC and DON concentration differently, potentially resulting in asynchronous patterns over time. River discharge was an important driver of DOM patterns. Regional precipitation in the lower SSR basin may also influence DOM patterns in locations where runoff contribution is greater. These regional factors explained greater variability in DOM compared to global scale indices (e.g., Pacific decadal oscillation) due to their direct control on DOM. A travel time corrected approach to account for the lengthy reservoir turnover time showed that a large reservoir caused a reduction in allochthonous DOC characteristics through photodegradation and perhaps, an increase in autochthonous characteristics. Our results illustrate: 1) the increase in DOM concentrations seen in the northern hemisphere is not present in semi-arid prairie rivers, 2) Controls on different DOM components could be different, and 3) large reservoirs may modify riverine DOC composition due to longer water residence time.
31. 题目: Seasonal variation and provenance of organic matter in the surface sediments of the three gorges reservoir: Stable isotope analysis and implications for agricultural management
期刊: Science of The Total Environment
作者: Heng Xiao, Changping Mao, Shuai Wang, Zhimin Jia, Wenbo Rao
摘要: The construction of the Three Gorges Dam has altered the hydrology and increased the trapping of sediment in the reservoir. This has also changed the composition and export of particulate organic matter in the Yangtze River. To understand the seasonal variations and sources of organic matter in sediments, total organic carbon (TOC), total nitrogen (TN), δ13Corg and δ15N in surface sediment samples from the mainstream and tributaries of the Three Gorges Reservoir were measured in the summer (July) and winter (December) of 2017, respectively. The results showed that the concentrations of TOC and TN in the surface sediments of the Three Gorges Reservoir were 0.79 %–1.46 % and 0.07 %–0.13 %, respectively. The ranges of δ13Corg and δ15N were − 26.35 ‰ to−24.70 ‰ and 2.59 ‰ to 5.67 ‰, respectively. According to δ13Corg and the TOC/TN ratio, the source range of organic matter was determined, and the contributions of different organic matter sources were quantified using a Bayesian mixed model. The results showed that soil organic matter and river plankton were the main sources of surface sediment organic matter in summer, whereas soil organic matter and aquatic vascular plants were the main sources in winter. The source of organic matter is related to biological factors in summer, whereas it is mainly caused by hydrodynamic conditions in winter. The analysis of δ15N further reveals that there are obvious external pollutants in the Three Gorges Reservoir, mainly related to artificial nitrogen fertiliser and domestic sewage. This study highlights the influence that soil nitrogen loss may be an important reason for the impact of agricultural non-point source pollution in the reservoir area, showing seasonal differences which were mainly affected by rainfall in summer and controlled by impoundment in winter. Hence, fine nitrogen management is required to reduce pollution in the Three Gorges Reservoir.
32. 题目: Assistant effects of spent mushroom substrate and its derived biochar on soil phytoremediation
期刊: Journal of Soils and Sediments
作者: Andong Wang, Dongsheng Zou, Patrick O’Connor, Bin Chen, Jingchen Zou, Yuqi Zhou, Hua Wang, Manyun Zhang
摘要: Purpose The massive applications of fertilizers and unreasonable management have resulted in serious soil degradation. Spent mushroom substrate (SMS) could be used as the raw material to produce biochar, and the SMS and SMS-derived biochar applications might affect the phytoremediation performances of contaminated soils. This study aimed to reveal the differences in functional mechanisms of SMS and SMS-derived biochar affecting the phytoremediation of soil heavy metal contamination. Materials and methods Alfalfa (Medicago sativa L.) was used to remediate the agricultural soil contaminated with cadmium (Cd), arsenic (As), and copper (Cu), and the effects of SMS and SMS-derived biochar applications on alfalfa phytoremediation, contaminant phytoextractions, microbial activities, and antibiotic and heavy metal resistance genes and were quantified. Results and discussion Relative to the alfalfa alone, extra biochar application reduced soil available Cd contents by 44% and enhance the phytoremediation performances via enhancements in plant biomass. The combined applications of SMS and biochar significantly enhanced soil urease, β-glucosidase, and phosphatase activities increased As resistance gene abundance by 264% but had negligible impact on antibiotic resistance gene abundance, relative to the alfalfa alone. The alfalfa phytoremediation with the SMS applications significantly enhanced the relative abundances of Proteobacteria and Bacteroidetes and significantly changed the community structures of microorganisms containing heavy metal resistance genes. Conclusions Our study suggested that the SMS-derived biochar reduced the soil’s available Cd content and enhanced the phytoremediation performance, and the SMS application could enhance microbial resistances to heavy metals and stimulate microbial activities in contaminated soil.
33. 题目: Magnetic pyro-hydrochar derived from waste cartons as an efficient activator of peroxymonosulfate for antibiotic dissipation
期刊: Separation and Purification Technology
作者: Yang Wu, Hai-yuan Xu, Zhi-hao Li, Jing-ying Zhu, Jia-wen Bai, Yi-fan Shao, Chia-Cheng Lin, Chung-Yu Guan
摘要: Owing to the current emphasis of achieving carbon neutrality, the valorization of waste biomass has drawn global attention. Using sequential hydrothermal and pyrolytic procedures, we synthesized a magnetic pyro-hydrochar catalyst doped with Fe and nitrogen (Fe@N-PHC) from waste cartons. The characterization results revealed that Fe@N-PHC had a specific surface area of up to 220 m2/g, a defect structure with an abundance of functional groups, and good magnetic properties. Fe@N-PHC exhibited good adsorption capability and could effectively activate peroxymonosulfate to remove ofloxacin (OFX) and oxytetracycline (OTC) over a broad pH range. Specifically, the segmented phase removed OFX at varied pH levels at ∼85% and OTC at ∼96% during 105 min, with the highest iron exudation concentration not exceeding ∼0.35 mg/L. Furthermore, the magnetic separation of Fe@N-PHC is feasible and could be reused multiple times. Possible transformation products and ecotoxicity were predicted using LC-MS/MS and the ecological structure-activity relationship (ECOSAR) predictive model software. In addition, the removal of total organic carbon from the system was assessed. According to radical quenching experiments and electron paramagnetic resonance investigations, the catalytic dissipation process involves the formation of both radicals (SO4•–, HO•, and O2•–) and a nonradical species (1O2). This exploratory study reconsiders the environmental value of waste cartons as part of a “waste into treasure” strategy. However, ongoing efforts should be made to optimize pyro-hydrochar modification and improve its catalytic capacity to remove various classes of emerging pollutants.
34. 题目: Effect of lignocellulosic biomass composition on the performance of biochar for the activation of peroxymonosulfate to degrade diclofenac
期刊: Separation and Purification Technology
作者: Lijie Xu, Ziyu Ye, Yuwei Pan, Ying Zhang, Han Gong, Xiang Mei, Weichuan Qiao, Lu Gan
摘要: In this study, poplar flour (PF) and walnut shell flour (WSF) with different proportions of lignocellulosic composition were selected as representative plant-based biomass precursors to prepare biochars (PB and WSB) for the activation of peroxymonosulfate (PMS). The structure of biochars and the removal performance of diclofenac (DCF) were examined in detail. Generally, the PB derived from PF that contained higher ratio of cellulose outperformed the WSB derived from WSF that contained higher ratio of lignin in the adsorption and degradation of DCF due to the more graphitized and aromatic structure of PB than that of WSB. Moreover, the adsorption and catalytic performance of two kinds of biochars were improved with the increase of pyrolysis temperature. The superior porosity property, abundant oxygen containing functional groups and good electrical conductivity of PB1000 led to the stronger capability than that of WSB1000. Nonradical oxidation mechanism including the singlet oxygen (1O2) and electron transfer was found to contribute to DCF degradation. Moreover, the PB1000 also demonstrated stronger adaptability to complex water environment than WSB1000. The findings of this work may provide enlightenment in the selection of lignocellulosic bio-wastes to prepare biochar for the degradation of organic pollutants.
35. 题目: Enhanced recovery of phosphorus in sewage sludge-derived biochar with CaCO3: phosphorus speciation and slow-release phosphorus behavior
期刊: Separation and Purification Technology
作者: Yuhan Zhu, Qian Zhao, Dongyue Li, Jun Li, Wei Guo
摘要: The recovery of phosphorus (P) from sewage sludge through pyrolysis is one of the most promising alternatives to alleviate the shortage of P supply in the future. Adding calcium additives is beneficial to the conversion of available P and helps improve the recovery and utilization efficiency of P in biochar. This study thoroughly examined the influence of CaCO3 on the speciation and slow-release behavior of P in sludge during pyrolysis at 500 and 700 °C. The addition of CaCO3 could enhance the conversion of non-apatite inorganic phosphorus (NAIP) into more accessible apatite phosphorus (AP). We observed that adding CaCO3 to raw sludge at 500 °C increased the proportion of AP in inorganic phosphorus (IP) from 65.2 to 97.3% but did not increase the concentration of AP, which remained between 31.03 and 31.64 mg/g. At 700 °C, introducing CaCO3 boosted the AP content from 35.08 to 41.38 mg/g and increased the proportion of AP in IP from 67.7 to 98.6%. Moreover, irrespective of the pyrolysis temperature being 500 °C or 700 °C, the final main form of P in biochar with CaCO3 was Ca5(PO4)3OH, according to experimental characterization results (X-ray photoelectron spectroscopy and X-ray diffraction) and thermochemical calculations. Additionally, the efficacy of citric acid (CA) in releasing biochar-bearing P was tested in a laboratory extraction experiment for 21 days. CaCO3-amended biochar showed a significantly slower total phosphorus (TP) release than the biochar without CaCO3 daily, and the amount of TP decreased with increasing amounts of added CaCO3. The finding of this study indicates that biochar generated by adding 10% CaCO3 has the highest AP concentration (41.38 mg/g) at 700 °C, and its TP-release efficiency in CA is 0.29–1.98 mg/g in 21 days, which shows remarkable potential as a soil fertilizer with slow P release.
36. 题目: Supporting nanoscale zero-valent iron onto shrimp shell-derived N-doped biochar to boost its reactivity and electron utilization for selenite sequestration
作者: Mingyu Wu, Xin Teng, Xingtang Liang, Yanjun Zhang, Zuqiang Huang, Yanzhen Yin
摘要: Nanoscale zero-valent iron (nZVI) has been widely used in the reductive removal of contaminants from water, yet it still fights against the inherent passive cover and the raise of medium pH. In this study, nZVI was supported onto a nitrogen-doped biochar (NBC) that was prepared by pyrolyzing shrimp shell for efficiently sequestrating aqueous selenite (Se(IV)). The resultant composite (NBC-nZVI) revealed a higher reactivity and electron utilization efficiency (EUE) than the bare nZVI in Se(IV) sequestration because of the positive charge, the buffering effect and the good conductivity of NBC. The kinetic rate and EUE of NBC-nZVI were increased by 143.4% and 15.3% compared to the bare nZVI, respectively, at initial pH of 3.0. The high removal capacity of 605.4 mg g−1 for NBC-nZVI was obtained at Se(IV) concentration of 1000 mg L−1, initial pH of 3.0, NBC-nZVI dosage of 1.0 g L−1 and contact time of 12 h. Moreover, NBC-nZVI exhibited a strong tolerance to solution pHs and coexisting compounds (e.g., humic acid) and could reduce the Se(IV) concentration from 5.0 mg L−1 to below the limit of drinking water (50 μg L−1) in real-world samples. This work exemplified a utilization of shrimp shell-derived NBC to simultaneously enhance the reactivity and EUE of nZVI for reductively removing contaminants.
37. 题目: Molecular insights into transformation of dissolved organic matter in landfill leachate nanofiltration concentrate during Fe2+/HClO electrochemical Fenton-type process
期刊: Separation and Purification Technology
作者: Dongyuan Chu, Zhaoji Zhang, Zhi-long Ye, Hui Zhang, Xianzhi Meng, Xiangnong Chen, Yichuang Lin, Shaohua Chen
摘要: Dissolved organic matter (DOM) transformations in complex electrochemical oxidation system, subjecting to simultaneous action of coexisting processes in the system and complexity of DOM, remain quite unexplored. In the present study, electrodialysis treated landfill leachate nanofiltration concentrate (LLNC-ED) was used to individually investigate DOM molecular transformations induced by three coexisting processes in electrochemical Fe2+/HClO system (anodic oxidation (AO), active chlorine (ACl), and electrochemical Fenton-type (EFT) processes) to unveil their competition and/or cooperation mechanisms on DOM transformation, using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and fluorescence excitation-emission matrix with parallel factor (EEM-PARAFAC). DOM transformations during AO underwent three steps: the addition of M(•OH) (heterogeneously formed •OH) in aromatics, the decomposition of fluorescent moieties and accumulation of aliphatic compounds, and the H abstraction in aliphatic compounds. In comparison, aromatic compounds more readily reacted with ACl species by electrophilic substitution and phenolic moiety oxidation after introducing the ACl process, followed by the formation of Cl-containing and quinone-type moieties, respectively. The EFT process could efficiently degrade non-chlorinated compounds but chlorinated organic molecules remained. Given that the chlorinated organic molecules were mainly formed by electrophilic aromatic substitution, preoxidation aimed at deconstructing aromatic moieties is proposed to prevent the generation of Cl-containing moieties to improve DOM mineralization efficiency. This study provides valuable reference for unveiling DOM transformation in electrochemical oxidation systems with various coexisting processes.
38. 题目: Elevational variation in soil phosphorus pools and controlling factors in alpine areas of Southwest China
作者: Jinsheng Li, Baoyun Wu, Dandan Zhang, Xiaoli Cheng
摘要: As an important life element in the Earth’s ecosystem, soil phosphorus (P) is of great significance to stability and sustainable development of terrestrial ecosystems. However, seasonal variations in different soil P pools and their regulatory mechanisms along elevations are not fully understood. Here, we investigated seasonal variations in soil P pools including total P (TP), available P (AP), inorganic P (IP), organic P (OP), labile P, moderately labile P, and stable P in topsoil (0–15 cm) along different elevations (2600–3900 m) in the Yulong Snow Mountain. The associated drivers including leaf nutrient contents, soil properties, micro-climate, and microbial parameters were also examined. We found that all soil P fractions reached a maximum at mid-elevations (2,900 m and 3,200 m), possibly due to the more active microorganisms and suitable soil climatic conditions for advancing P weathering. Meanwhile, soil AP pool was also observed to be tightly related to the leaf P content along elevations. Unexpectedly, most soil P pools did not show seasonal changes, except for AP showing significantly higher level in the wet season than in the dry season, owing to the high temperature and microbial activity for promoting P release in the wet season. Consequently, we found that microbial P, acid phosphatase and dissolved organic carbon had a stronger influence on different P pools than other soil factors. Moreover, there was a strong interaction of labile P and moderately labile P with soil environments (i.e. soil moisture, temperature, dissolved organic carbon). Collectively, our results revealed the elevational shifts in soil P pools and potential mechanisms in Yulong Mountain, and provided an important theoretical basis for soil P dynamics in response to environments in mountain ecosystems.
39. 题目: Size exclusion chromatography and stable carbon isotopes reveal the limitations of solid phase extraction with PPL to capture autochthonous DOM production
期刊: Marine Chemistry
作者: Gabriel Dulaquais, Pierre Fourrier, Jean François Maguer, Corentin Denis, Matthieu Waeles, Ricardo Riso
摘要: The study of the elemental and carbon isotopic composition of dissolved organic matter (DOM) is of great interest in deciphering the origin and transformations of organic matter in estuarine and coastal environments. Styrene-divinylbenzene copolymer (PPL) sorbent is currently the most commonly used material for the isolation of DOM from environmental samples. It is notably used for the development of molecular formula-based indices used to study DOM reactivity. However, any extraction procedure (including with PPL) will fractionate the DOM. If this fractionation is not well constrained it can lead to biased interpretations of the biogeochemical processes affecting DOM. In this work we investigate the fractionation effects of the PPL sorbent on the size class distribution of DOM and the carbon isotopic composition of the PPL retentate. The use of size exclusion chromatography, that does not require a pre-concentration step, allows a precise study of the fractionation of DOM (including aromaticity) by the PPL resin. Extractions performed on two types of humic substances dissolved in artificial seawater, using the PPL resin, showed high extraction yield (> 85%) and the stable isotopic carbon composition (δ13C) of these compounds was successfully recovered. These results indicate that salinity is not a parameter affecting extraction yield on PPL sorbent. For a hydrophilic compound (atropine) the extraction efficiency was low (33%) and δ13C signature was underestimated. Size exclusion chromatography measurements, in samples collected along a salinity gradient, demonstrate that the PPL sorbent strongly fractionates DOM. Although the DOM size class distributions in freshwaters and marine waters were initially different, their retentates were marked by similar size class distributions. This work demonstrates that PPL resin captures DOM compounds with less nitrogenous content and it seems to have a lower affinity for aromatic compounds of marine origin than of terrigenous origin. The study of DOM distribution in a macro-tidal estuary demonstrated the limitations of PPL resin extraction in capturing an internal N-rich DOM production event at the time of sampling. Futhermore, the isotopic composition of the PPL resin retentate appears to depend on the extraction efficiency of the more hydrophobic compounds which changed along the salinity gradient. This study recommends careful interpretations of data that only rely on PPL extractions, particularly for works tracking the origin of DOM in estuaries and comparing DOM composition across ocean biogeochemical domains.
40. 题目: An Assessment of Vertical Carbon Flux Parameterizations Using Backscatter Data From BGC Argo
期刊: Geophysical Research Letters
作者: Bin Wang, Katja Fennel
摘要: Model parameterizations of particulate organic carbon (POC) flux are critical for simulating the strength and future evolution of the biological carbon pump (BCP) but remain poorly constrained because direct observations are sparse. Here, we ask whether the Biogeochemical (BGC)-Argo proxy observations of POC can help distinguish between these parameterizations by objectively comparing two common parameterizations, which reproduce the observed slowdown of flux attenuation with depth by either decreasing the remineralization rate or increasing the sinking velocity. Both can well reproduce the BGC-Argo observations in top 1,000 m but predict different POC concentration below, making them possible to be distinguished if BGC-Argo observations were available there. Therefore, an integration of backscatter sensors into the Deep Argo program is recommended to provide full depth proxy measurements. If the parameterization is known, POC flux can be determined from POC concentration. Thus, the BGC-Argo proxy observations of POC concentration provide new insights into the BCP.