1. 题目: Characterization and adsorption applications of composite biochars of clay minerals and biomass
期刊: Environmental Science and Pollution Research
作者: Lihui Gao, Jillian L. Goldfarb
摘要: Composite mineral-biochars of a homogeneous biomass (cellulose) and heterogeneous biomass (oak leaves) were fabricated with either 5 wt% or 10 wt% minerals (montmorillonite (MMT), kaolinite, and sand) and then pyrolyzed at 600 °C for 60 min. Characterizations including proximate analysis, ultimate analysis, surface area and porosity, morphology, and surface chemistry confirmed that minerals were present on the surface of biochar, and MMT/kaolinite-biochar composites showed a strengthening in the chars’ aromatic structures, as well as increases in oxygen-containing surface functional groups. Methylene blue adsorption isotherms indicated that the MMT/kaolinite-biochars had higher adsorption capacities than pure biomass or biomass-sand biochars (110 mgMB/gchar and 24 mgMB/gchar for MMT-cellulose char and cellulose char, respectively). A multilinear model relating adsorption capacity and adsorbent properties was developed to measure the relative contribution of biochar properties to adsorption behavior. The model indicates that pore volume and hydrogen bonding were the dominant properties in controlling the adsorption of methylene blue onto the biochars. Findings from this work indicate that composite biochars prepared from biomass and inexpensive clay minerals are a promising adsorbent for remediating organic contaminants from water.
2. 题目: Dissolved organic carbon removal and CX3R-type byproduct formation during the peroxymonosulfate pre-oxidation followed by coagulation
期刊: Chemical Engineering Journal
作者: Tiantian Chen, Shengkun Dong, Xueping Guo, Wenhai Chu, Ting Xu, Daqiang Yin
摘要: Hydroxyl radicals (HO·) and sulfate radicals (SO4￼−) can be generated when ferric-based coagulants are coupled with the potential alternative pre-oxidant peroxymonosulfate (PMS). Although HO·, SO4￼− and PMS may oxidize most organic matter, they could also react with chloride stemming from chloride-containing coagulants, generating reactive chlorine species that may further react with organic matter to produce unwanted byproducts. CX3R-type [X = H or Cl, R = H, CN, C(OH)2 or CONH2] byproducts have cytotoxicity and genotoxicity. Therefore, the dissolved organic carbon (DOC) removal and CX3R-type byproduct formation during the PMS pre-oxidation followed by coagulation (PPFC) (ferric sulfate [Fe2(SO4)3], ferric chloride (FeCl3), aluminium sulfate [Al2(SO4)3] or aluminium chloride (AlCl3)) were investigated. Results showed that PPFC could remove DOC higher compared to PMS pre-oxidation or coagulation alone. The DOC removal efficiency followed the order of Fe2(SO4)3 > FeCl3 > Al2(SO4)3 > AlCl3 during the PPFC. During the PPFC, FeCl3 and AlCl3 resulted in the formation of CX3R-type byproduct that posed significant calculated toxicity induction, while Fe2(SO4)3 and Al2(SO4)3 did not. Compared to AlCl3, FeCl3 resulted in higher CX3R-type byproduct concentration and finished water toxicity, which both decreased as the pre-oxidation duration extended, and increased as the PMS concentration increased. The CX3R-type byproduct formation and finished water toxicity increased and then decreased as both sedimentation time and coagulant dosage increased. Compared to PMS and SO4￼−, HO· played a more significant role in the formation of CX3R-type byproduct and induction of toxicity of finished water during the PPFC (FeCl3). Therefore, Fe2(SO4)3 was the more suitable coagulant when PMS was used as the pre-oxidant.
3. 题目: Characterisation of clays from Alicante province (SE Spain) for use in the recovery of degraded soils
期刊: Environmental Geochemistry and Health
作者: J. D. Jordá, J. E. Tent-Manclús, M. Cerdán, A. Sánchez-Sánchez, P. Jaramillo, M. M. Jordán
摘要: The goal of this paper is the characterisation of seven clays of the province of Alicante (SE Spain) and their possible use to improve the fertility, water absorption and contaminant-retaining capacity of degraded soils. Three soils affected by the dumping of construction debris were also studied to diagnose the problems and possible recovery strategies. Several physicochemical properties were measured, such as the water holding capacity, soil organic matter, lime, pH, EC and CEC. A high correlationship between mineralogical and elemental composition was obtained. Illite was present in all clays and soils. Some of the samples also contained kaolinite and significant amounts of lime. The CEC, as expected, was more closely related to the organic matter content. Soil organic matter was detected in the second derivative of the FTIR spectra by the signals of the CH2 groups at 2850 and 2919. This way, the FTIR spectrum for the soils of the area would make it possible to estimate both the organic matter content and the CEC. Despite their origin, soils did not show heavy metal pollution; however, salinisation risk seemed to be the most probable cause of degradation. According to the organic matter, lime and illite content, two clays were selected as the most suitable for soil degradation recovery. Furthermore, organic matter additions may help to improve the self-depurative ability of the soil.
4. 题目: Effectiveness of Water Management in Producing Cadmium-Safe Rice in Soils of Different Contamination Levels and Physicochemical Properties
期刊: Water, Air, & Soil Pollution
作者: Weisheng Lu, Dongqin Li, Ying Liu, Guijie Li, Yang Zhao, Qiuhua Zhang, Zulei Zeng, Huaxing Li, Guikui Chen
摘要: The effectiveness of water management in reducing cadmium (Cd) accumulation in rice grain has mainly been investigated in slightly and moderately contaminated soils but seldom in heavily contaminated soils. In addition, how soil physicochemical properties influence the effectiveness of water management merits investigation. In this study, a pot experiment was performed using six soils of slight (S1), moderate (S2–S5), and heavy (S6) Cd contamination levels and of different properties. Three water managements, flooding until full tillering (W1), flooding until full tillering and reflooding after 7–10-day drying (W2), and continuous flooding without drying (W3), were implemented for each soil. Cadmium content in rice grain was significantly decreased (by 60% on average) in W2 and further decreased (by 82% on average) in W3 as compared with W1 in all the six soils. Grain Cd contents in the W3 treatments were decreased to below the Chinese food safety standard of 0.2 mg kg−1 in all the six soils except in S6 (0.36 mg kg−1). For all the three water management regimes, the lowest grain Cd content was observed in S3 which had high contents of organic matter, sulfur, and iron. The results indicate that extended flooding can effectively decrease rice grain Cd accumulation in soils of various contamination levels especially those rich in organic matter, sulfur, and iron. But for heavily contaminated soils, water management may need to combine with other approaches to further decrease grain Cd content to meet food safety standard.
5. 题目: Comparison of Multiple Linear Regression and Biotic Ligand Models to Predict the Toxicity of Nickel to Aquatic Freshwater Organisms
期刊: Environmental Toxicology and Chemistry
作者: Kelly Croteau, Adam Ryan, Robert Santore, David DeForest, Christian Schlekat, Elizabeth Middleton, Emily Garman
摘要: Toxicity modifying factors can either be modeled empirically with linear regression models or mechanistically, such as with the Biotic Ligand Model (BLM). The primary factors affecting the toxicity of nickel to aquatic organisms are hardness, dissolved organic carbon (DOC), and pH. Interactions between these terms were also considered. This article develops multiple linear regressions (MLRs) with stepwise regression for 5 organisms in acute exposures, 4 organisms in chronic exposures, and pooled models for acute, chronic, and all data, and compares the performance of the Pooled‐All MLR model to the performance of the BLM. Independent validation data was used for evaluating model performance, which for pooled models included data for organisms and endpoints not present in the calibration dataset. Hardness and DOC were most often selected as the explanatory variables in the MLR models. An attempt was also made at evaluating the uncertainty of the predictions for each model; predictions that showed the most error tended to show the highest levels of uncertainty as well. The performance of the two models were largely equal, with differences in performance becoming more apparent when looking at the performance within subsets of the data.
6. 题目: Distribution, source and burial of sedimentary organic carbon in Kermadec and Atacama trenches
期刊: Journal of Geophysical Research: Biogeosciences
作者: Yunping Xu, Xinxin Li, Min Luo, Wenjie Xiao, Jiasong Fang, Harunur Rashid, Yongbo Peng, Wenpeng Li, Frank Wenzhöfer, Ashley A. Rowden, Ronnie N. Glud
摘要: Knowledge of sedimentary organic carbon (OC) in hadal trenches, the deepest ocean realm, is rudimentary. Here we conducted a comprehensive analysis of total OC (TOC), stable and radio‐carbon isotopes (δ13C and Δ14C) and biomarkers (e.g., n‐alkanes, n‐alkanols and n‐fatty acids) in 12 sediment cores collected from hadal (trench axis) and non‐hadal (abyssal plains and slopes) settings of the Kermadec Trench (Southwestern Pacific) and Atacama Trench (Southeastern Pacific) regions. Our results show that the TOC in the Atacama Trench region (0.86 ± 0.69%) is significantly higher than that of the Kermadec Trench region (0.29 ± 0.08%), likely related to different surface primary productivity. In both trench regions, the hadal sites are generally characterized by more negative δ13C, higher TOC/TN ratio and similar or higher abundance ratio of terrigenous/marine biomarkers as compared to the non‐hadal sites, suggesting the selective preservation of terrigenous biogenic/fossil OC at the hadal trench axis. The linear increase in 14C age with sediment depth in non‐hadal cores reflects steady depositional conditions, whereas 7 out of 8 hadal sediment cores show 14C age reversals presumably due to occasional mass‐transport deposits. Our results suggest (1) a strong heterogeneity in sedimentary OC characteristics between trenches and within each trench; and (2) relatively high accumulation rates of terrigenous OC in both the Kermadec Trench (0.35 ± 0.04 g m‐2 yr‐1) and the Atacama Trench (1.4 ± 0.5 g m‐2 yr‐1). Thus, hadal trenches appear to represent an important environment for terrigenous carbon deposition in the deep ocean.
7. 题目: Heterotrophic nitrogen fixation in response to nitrate loading and sediment organic matter in an emerging coastal deltaic floodplain within the Mississippi River Delta plain
期刊: Limnology and Oceanography
作者: Song Li, Robert R. Twilley, Aixin Hou
摘要: Increasing nitrate (NO3−) loading in rivers due to agricultural fertilization alters benthic nitrogen (N) cycling and shifts coastal wetlands from being a net source to net sink of reactive N. Heterotrophic N2 fixation that converts N2 to reactive N is often assumed negligible in eutrophic ecosystems and excluded in coastal N budget evaluations. We investigated N2 fixation and denitrification in response to increasing NO3− loading (0, 10, and 100 μM) and sediment organic matter (OMsediment) concentrations in the emerging Wax Lake Delta. Continuous flow‐through incubations with 30N2 addition was applied to measure N2 fixation. The variation of N2 fixation rates from 0 to 437 μmol N m−2 h−1 among different NO3− and OMsediment concentrations were comparable to the estimated denitrification rates of 141–377 μmol N m−2 h−1. Increasing overlying NO3− concentrations reduced N2 fixation rates and facilitated denitrification rates at each OMsediment concentration. However, 100 μM of overlying NO3− did not thoroughly inhibit N2 fixation rates in sites with intermediate and higher OMsediment concentrations (189 and 99 μmol N m−2 h−1, respectively). Both N2 fixation and denitrification increased with increasing OMsediment concentrations, but the relative importance of these processes was impacted mostly by overlying NO3− concentration as increasing NO3− switched the dominance of N2 fixation to denitrification in benthic N cycling. This study highlights the importance of heterotrophic N2 fixation in coastal deltaic floodplains and emphasizes the necessity of including N2 fixation quantification in coastal N budget evaluation, not only in oligotrophic environment but also in eutrophic environment.
8. 题目: Impacts of continuous biochar application on major carbon fractions in soil profile of North China Plain’s cropland: In comparison with straw incorporation
期刊: Agriculture, Ecosystems & Environment
作者: Tongping Lu, Xiujun Wang, Zhangliu Du, Lipeng Wu
摘要: Although the increase of soil organic carbon (SOC) in biochar-amended soil has been well documented, there is a lack of understating on the responses of soil inorganic carbon (SIC) to biochar application in soil profile. Here, we conducted a field study to investigate the effects of 10-year application of biochar at 4.5 Mg ha−1 yr−1 (B4.5) and 9.0 Mg ha−1 yr−1 (B9.0), and straw return (SR) of 15 Mg ha−1 yr−1 on SOC and SIC and their dissolved fractions. Our results showed significant difference in SOC content over 0–20 cm, with an order of B9.0 (8.46 g kg−1) > B4.5 (7.58 g kg−1) > SR (6.81 g kg−1) > control (5.26 g kg−1). However, SIC content was significantly lower under biochar (1.0–2.0 g kg−1) and control (1.0–2.0 g kg−1) than straw incorporation (3.2–3.7 g kg−1) over 0–40 cm. On average, DOC:SOC ratio (an index of SOC desorption) was significantly lower under biochar (~2.0%) and SR (2.6%) treatments than under control (3.1%), implying that both biochar and straw amendments can enhance SOC stability. Over the ten years, 62–81% of biochar-C was converted to SOC in the 0–100 cm layer, which was significantly higher than that (21%) of straw-C. Our estimation suggested that total carbon loss rate was 51–53% under biochar amendment and 70% with straw incorporation. This study highlights that biochar application has great potential for carbon sequestration in cropland of north China.
9. 题目: The advantages and limitations of global datasets to assess carbon stocks as proxy for land degradation in an Ethiopian case study
作者: Stefania Cerretelli, Laura Poggio, Getahun Yakob, Shiferaw Boke, Mulugeta Habte, Malcolm Coull, Alessandro Peressotti, Helaina Black, Alessandro Gimona
摘要: Land degradation leads to ecosystem degradation, reducing ecosystem functioning and depleting ecosystems' resilience. The majority of factors linked to land degradation are closely related with the depletion of below- and above-ground stocks of organic carbon. Organic carbon stock is important for climate change mitigation and for restoring soil functions such as those crucial to support food security. In this study, we mapped carbon stocks to infer land degradation in a small area in the Ethiopian Great Rift Valley. The study aimed to assess carbon stock status and to identify limitations and advantages of using global data in mapping at local scale relative to using local data. Two different datasets were developed; i) a “global dataset” characterised by data from datasets with global coverage data, and ii) a “hybrid dataset” that coupled data from global datasets, soil data derived from a local survey, and land cover data derived from a supervised classification of satellite images. The results showed that i) global datasets introduced inaccuracy that must be taken into account for advocating interventions at a local scale, and ii) global datasets could be used at a small catchment level for decision-making, if a simple rank of values is sufficient, but they might provide an optimistic picture of land degradation because they overestimate stocks.
10. 题目: Nitrogen deposition accelerates soil carbon sequestration in tropical forests
期刊: Proceedings of the National Academy of Sciences
作者: Xiankai Lu, Peter M. Vitousek, Qinggong Mao, Frank S. Gilliam, Yiqi Luo, Benjamin L. Turner, Guoyi Zhou, Jiangming Mo
摘要: Terrestrial ecosystem carbon (C) sequestration plays an important role in ameliorating global climate change. While tropical forests exert a disproportionately large influence on global C cycling, there remains an open question on changes in below-ground soil C stocks with global increases in nitrogen (N) deposition, because N supply often does not constrain the growth of tropical forests. We quantified soil C sequestration through more than a decade of continuous N addition experiment in an N-rich primary tropical forest. Results showed that long-term N additions increased soil C stocks by 7 to 21%, mainly arising from decreased C output fluxes and physical protection mechanisms without changes in the chemical composition of organic matter. A meta-analysis further verified that soil C sequestration induced by excess N inputs is a general phenomenon in tropical forests. Notably, soil N sequestration can keep pace with soil C, based on consistent C/N ratios under N additions. These findings provide empirical evidence that below-ground C sequestration can be stimulated in mature tropical forests under excess N deposition, which has important implications for predicting future terrestrial sinks for both elevated anthropogenic CO 2 and N deposition. We further developed a conceptual model hypothesis depicting how soil C sequestration happens under chronic N deposition in N-limited and N-rich ecosystems, suggesting a direction to incorporate N deposition and N cycling into terrestrial C cycle models to improve the predictability on C sink strength as enhanced N deposition spreads from temperate into tropical systems.
11. 题目: Anaerobic methane oxidation sustains soil organic carbon accumulation
期刊: Applied Soil Ecology
作者: Yaohong Zhang, Fangyuan Wang, Weiwei Xia, Weiwei Cao, Zhongjun Jia
摘要: The intensified input of anthropogenic nitrogen (N) fertilizers has accelerated the transformation of active N species (e.g., N2O, NO3− and NO2−) and the coupled methane (CH4) cycling on a global scale, but the impact of N-mediated CH4 metabolism on soil carbon accumulation, which is crucial for agricultural sustainability, remains poorly understood. In this study, we show that more than 60% of the CH4-C were converted to soil organic matter during anaerobic oxidation in two paddy soils with a parent material origin of river and marine sediments. The anaerobic enrichment of 13C in organic matter and inorganic CO2 indicated that the net 13C conversion of CH4 could reach up to 120 and 49 nmol g−1 in two paddy soils, respectively, and these processes were further stimulated significantly by up to 1.8–3.1 fold under denitrifying conditions by reactive N species (N2O, NO3− and NO2−) acting as electron acceptors. Denitrifying methanotrophy is already recognized as the major CH4 sink in marine and freshwater ecosystems, and we now identify this process as a source of soil organic matter in agriculture as well.
12. 题目: Size-segregated aerosols over a high altitude Himalayan and a tropical urban metropolis in Eastern India: Chemical characterization, light absorption, role of meteorology and long range transport
期刊: Atmospheric Environment
作者: Abhinandan Ghosh, Anil Patel, Neeraj Rastogi, Sudhir Kumar Sharma, Tuhin Kumar Mandal, Abhijit Chatterjee
摘要: A study has been conducted focusing on the chemical and optical characterization of water soluble inorganic and organic components of aerosols at different sizes, over a high altitude Himalayan station, Darjeeling (27.1o N and 88.15o E, 2200 m amsl) and a tropical urban metropolis, Kolkata (22.5° N, 88.3° E, ∼6 m amsl) for two-year long period (March 2016-February 2018). It was observed that local meteorology and long range transport of pollution plumes have played the pivotal role in governing the temporal variation of the mass distribution and concentration of aerosols and its various components over both the sites. The aerosol mass-size distributions were found to be bimodal in nature with the relative dominance of accumulation mode (0.1-1.0 μm) over coarse mode (1.8-10 μm) over both the stations, indicating dominance of the anthropogenic emissions. Among the size classes, accumulation mode aerosols alone contributed 55-75 % over Darjeeling and 40-60% over Kolkata to PM10. The coarse mode aerosols were mainly consisted of primary inorganic species over Kolkata and water soluble organic carbons (WSOC) over Darjeeling whereas the fine mode aerosols (accumulation: 0.1-1.0 μm) were primarily composed of the secondary inorganic aerosols for both the stations. Irrespective of the seasons and stations, SO42– and NH4+ exhibited peaks in the mass-size distribution at 1.0-0.1 μm whereas that of NO3- varied with the seasons. The photochemical oxidation and the aqueous phase oxidation of SO2 (g) were the pathways for SO42- formation over Darjeeling whereas the later dominated over Kolkata. Concentration weighted trajectory (CWT) model has revealed that the secondary inorganic aerosols and WSOC were local/regional in origin over Kolkata megacity whereas Darjeeling was influenced by mixed sources. The accumulation mode aerosols were found to be the highest light absorbing over both the stations irrespective of the seasons. Over Darjeeling, the absorption coefficient (babs_365) and the mass absorption efficiency (MAE) of WSOC were maximum for local biomass burning aerosols than the transported plumes whereas those over Kolkata were maximum for transported biomass burning plumes from Eastern Ghats.
13. 题目: Evaluation of the nutrients cycle, humification process, and agronomic efficiency of organic wastes composting enriched with phosphate sludge
期刊: Journal of Cleaner Production
作者: Ayoub Haouas, Cherkaoui El Modafar, Allal Douira, Saâd Ibnsouda-Koraichi, Abdelkarim Filali-Maltouf, Abdelmajid Moukhli, Soumia Amir
摘要: Composting is now at the core of the environmental policy and the circular economy as one of the best options for recycling organic waste leading to a high-value final product. However, composting organic waste suffers from several drawbacks in the resulting product, such as insufficient maturity, unstable organic matter (OM), accumulation of phytotoxic substances, and low amounts of nutrients. This study investigated the effectiveness of adding phosphate sludge (PS) to improve the green waste (GW) composting process, as well as its effectiveness when combined or not with sugar beet waste (SBW), GW, and oil mill waste (OMW) in the composting process of food waste (FW). The impact on the fertilizer quality of final products was also assessed. Composting treatments and controls were conducted in large-scale trials for 150 days. The composting process parameters, nutrient dynamics, phytotoxic effect, and agronomic capacity of the compost product were evaluated. The physicochemical analyses demonstrated that the addition of PS increased the pile temperature and prolonged thermophilic period by two weeks compared to controls. The PS addition brought pH, electrical conductivity (EC), and carbon to nitrogen ratio (C/N) values of FW and GW composts to maturity acceptable level. The results also indicate that adding PS alone or in combination stimulated the nitrification process in FW composting with a nitrate concentration of 69.91 mg/L recorded in the treatment received the combined addition of PS and GW. The results of Fourier-transform infrared (FT-IR) spectroscopy analysis showed a significant increase in humification by adding PS in mixtures of FW and GW. The resulting treated composts showed high total content of nutrients, no phytotoxic effect on seed germination, and growth enhancement of tomato plant compared to control compost, NPK fertilizer, and no amended soil.
14. 题目: Comparative study on characterization and adsorption properties of phosphoric acid activated biochar and nitrogen-containing modified biochar employing Eucalyptus as a precursor
期刊: Journal of Cleaner Production
作者: Ze Lu, Hua Zhang, Asfandyar Shahab, Kang Zhang, Huiting Zeng, Aziz-Ur-Rahim Bacha, Iqra Nabi, Habib Ullah
摘要: As a green adsorbent, biochar has attained progressive attention due to its advantages such as high carbon content, high surface area, stable structure, and heavy metals removal through cation exchange capacity. Biochar can be synthesized from the feedstock, agricultural, and organic waste. In this study, the activated biochar (AC) and ammonia modified biochar (NAC) were prepared from Eucalyptus waste by acid activation. The adsorption properties of pure AC and NAC were compared for aqueous Cr(VI) removal. Advanced characterization techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were used to examine the morphology, elemental composition, and functional groups. Several influencing factors on adsorption processes such as solution pH, adsorption dosage, contact time, and initial concentration were investigated. The ammonia modified biochar (NAC) could remove 85.67% of Cr (VI), whereas 76.73% removal rate was observed for the activated biochar (AC) at an initial concentration of 300 mg/L at pH 2.0 and 25 °C with a dosage of 0.025 g/25 mL. The pseudo-second-order kinetic and Freundlich isotherm adsorption models showed close-fitting for the activated biochar (AC) and the ammonia modified biochar (NAC) adsorption in Cr(VI) equilibrium state. Cr (VI) oxidizes nitrogen and oxygen functional groups on NAC following the conversion into Cr (III). The removal and adsorption mechanism was the coexistence of physical adsorption and chemical reduction examined by FTIR and XPS illustrating Cr(VI) removal.
15. 题目: Seagrass ( Halophila stipulacea ) invasion enhances carbon sequestration in the Mediterranean Sea
期刊: Global Change Biology
作者: Marlene Wesselmann, Nathan R. Geraldi, Carlos M. Duarte, Jordi Garcia‐Orellana, Rubén Díaz‐Rúa, Ariane Arias‐Ortiz, Iris E. Hendriks, Eugenia T. Apostolaki, Núria Marbà
摘要: The introduction and establishment of exotic species often result in significant changes in recipient communities and their associated ecosystem services. However, usually the magnitude and direction of the changes are difficult to quantify because there is no pre‐introduction data. Specifically, little is known about the effect of marine exotic macrophytes on organic carbon sequestration and storage. Here, we combine dating sediment cores (210Pb) with sediment eDNA fingerprinting to reconstruct the chronology of pre‐ and post‐arrival of the Red Sea seagrass Halophila stipulacea spreading into the Eastern Mediterranean native seagrass meadows. We then compare sediment organic carbon storage and burial rates before and after the arrival of H. stipulacea and between exotic (H. stipulacea) and native (C. nodosa and P. oceanica) meadows since the time of arrival following a Before‐After‐Control‐Impact (BACI) approach. This analysis revealed that H. stipulacea arrived at the areas of study in Limassol (Cyprus) and West Crete (Greece) in the 1930s and 1970s, respectively. Average sediment organic carbon after the arrival of H. stipulacea to the sites increased in the exotic meadows twofold, from 8.4 ± 2.5 g Corg m−2 year−1 to 14.7 ± 3.6 g Corg m−2 year−1, and, since then, burial rates in the exotic seagrass meadows were higher than in native ones of Cymodocea nodosa and Posidonia oceanica. Carbon isotopic data indicated a 50% increase of the seagrass contribution to the total sediment Corg pool since the arrival of H. stipulacea. Our results demonstrate that the invasion of H. stipulacea may play an important role in maintaining the blue carbon sink capacity in the future warmer Mediterranean Sea, by developing new carbon sinks in bare sediments and colonizing areas previously occupied by the colder thermal affinity P. oceanica.
16. 题目: No effect of long-term soil warming on diffusive soil inorganic and organic nitrogen fluxes in a temperate forest soil
期刊: Soil Biology and Biochemistry
作者: Jakob Heinzle, Wolfgang Wanek, Ye Tian, Steve Kwatcho Kengdo, Werner Borken, Andreas Schindlbacher, Erich Inselsbacher
摘要: Climate warming affects nitrogen (N) cycling in forest soils, but implications for plant available N have remained unclear. We estimated in situ diffusive fluxes of amino acids and inorganic N in a temperate forest soil after 14 years of soil warming. Results from four sampling campaigns (n = 1152 microdialysis samples) during the growing season showed no effect of warming on diffusive N fluxes. Diffusive NH4+ fluxes increased from spring towards autumn while NO3- fluxes followed an opposite trend. Overall, the proportion of amino acids in the total diffusive N flux was low (13 - 30%) in this carbonate soil compared to other temperate and boreal forest soils.
17. 题目: Improving the accuracy of soil organic carbon content prediction based on visible and near-infrared spectroscopy and machine learning
期刊: Environmental Earth Sciences
作者: Mingxing Xu, Xianyao Chu, Yesi Fu, Changjiang Wang, Shaohua Wu
摘要: Choosing appropriate multivariate calibration and preprocessing transformation techniques is important in the determination of soil organic carbon (SOC) content based on visible and near-infrared (Vis–NIR) spectroscopy. The performance levels of partial least-squares regression (PLSR), support vector machine regression (SVMR), and wavelet neural network (WNN) calibration methods coupled with different preprocessing approaches were compared using three kinds of criteria, including the coefficient of determination (R2), root mean square error (RMSE), and residual prediction deviation (RPD). A total of 328 soil samples collected from the south bank of Hangzhou Bay were used as the dataset for the calibration–validation procedure and SOC content inversion. The effects of spectra preprocessing transformation methods were evaluated for raw spectra, Savitzky–Golay smoothing with the first derivatives of reflectance (FDR) and Savitzky–Golay smoothing with logarithm of reciprocal of the reflectance (log R−1). The results indicate that the SVMR is superior to the PLSR, and WNN models for SOC content prediction. The combination of the SVMR model with FDR provided the best prediction results for the SOC content, with R2p = 0.92, RPDP = 2.82, RMSEP = 0.36%, and a kappa correlation coefficient of interpolation as high as 0.97. The FDR of Vis–NIR spectroscopy combined with the SVMR model is recommended over the PLSR and WNN modeling techniques for the high-accuracy determination of the SOC content.
18. 题目: Selective removal of common cyanotoxins: a review
期刊: Environmental Science and Pollution Research
作者: Shulian Wang, Yiying Jiao, Zhi Rao
摘要: The development of cyanobacterial blooms can have adverse effects on water bodies and may produce cyanotoxins. Several physical and chemical methods have been applied to remove cyanotoxins, but they have been significantly challenged due to extensive energy footprint and over-used chemicals, which limits practical application on a large scale. Selective removal has been regarded as the most promising approach recently for the elimination of prevalent and major bloom-forming cyanotoxins (e.g., microcystins and cylindrospermopsin) as natural organic matters and radical scavengers are ineluctably present in real scenarios. This paper reviews current advancements in research on selective oxidation and adsorption of cyanotoxins. Its goal is to provide comprehensive information on the treatment mechanism and the process feasibility involved in the cyanotoxin removal from real-world waters. Moreover, perspectives of cyanotoxin control and in situ selective elimination approaches are also reviewed. It is expected that the information gathered and discussed in this review can provide a useful and novel reference and direction for future pilot-scale applications.
19. 题目: Enhanced adsorption capacity of tetracycline on tea waste biochar with KHCO3 activation from aqueous solution
期刊: Environmental Science and Pollution Research
作者: Bin Li, Yingying Huang, Zixin Wang, Jiale Li, Zhuo Liu, Shisuo Fan
摘要: Activation is an important pathway that can enhance the adsorption capacity of biochar. In this study, a modified tea waste biochar (MTWBC) was prepared via a two-step pyrolysis approach with KHCO3 activation. Pristine tea waste biochar (TWBC) was also produced as control via one-step pyrolysis without activation. Various characterizations were undertaken to investigate the influence of modification on the morphology, composition, carbon structure, surface area, and functional group of biochar, including scanning electron microscope (SEM), surface area and pore analyzer, element analysis, point of zero charge (pHPZC), X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). After KHCO3 activation treatment, the surface area, total pore volume, and micropore volume of MTWBC reached 1981 m2·g-1, 0.8547 cm3·g-1, and 0.6439 cm3·g-1 which were 7.34-fold, 7.27-fold, and 7.30-fold increases, respectively, compared with TWBC. The aromaticity, hydrophilicity, and polarity of the MTWBC increased after modification. More graphitization with less defective structures occurred in MTWBC after modification. The C-, O-, and N-containing groups in MTWBC also changed after the reaction of KHCO3. The pseudo-second-order and Freundlich models best described the adsorption process on biochar. The maximum adsorption capacity of tetracycline (TC) on MTWBC reached 293.46 mg·g-1, which was 15-fold more than that of TWBC (19.68 mg·g-1). An alkaline environment decreased the TC adsorption on biochars. The presence of Na+, K+, Ca2+, and Mg2+ inhibited TC adsorption onto biochars. The influence of Cu2+ on TC adsorption by biochars depends on its initial concentration. The enhanced adsorption capacity of TC on MTWBC was mainly attributable to the large surface area, the improved pore volume, and more aromatic structure. The adsorption mechanism was based on pore filling and π-π EDA interaction. Therefore, KHCO3 activated biochar has the potential to remove TC from aquatic environments.
20. 题目: Trace-element behaviour in sediments of Ugandan part of Lake Victoria: results from sequential extraction and chemometrical evaluation
期刊: Environmental Earth Sciences
作者: Nils Ribbe, Kenneth Arinaitwe, Tallent Dadi, Kurt Friese, Wolf von Tümpling
摘要: Lake Victoria is the second largest freshwater lake and the largest tropical lake in the world. The transboundary lake has the fastest growing population in its catchment, which can impact the water and sediment quality. To determine the extent of anthropogenic effects on sediment quality in the Ugandan part of Lake Victoria, the contents and binding behaviour of trace elements were analysed, as well as organic matter and phosphorus in different sediment layers of both deep and coastal sediments near the coastal cities of Entebbe, Kampala and Jinja. The data were assessed using the German LAWA criteria for trace-element pollution, the Geo-Index, Cluster- and Factor analyses. Mostly, no critical trace-element contamination in the sediments of the investigated area was observed. However, changes in element distributions caused by anthropogenic influences from around the lake were detected, like higher contents of Cu, Ti and V in near shore sediments with urban surrounding. Near Jinja, industrial wastewaters caused particularly elevated contents of Cu in the sediments (70–121 mg/kg, 3.5–6 times the geogenic background), exceeding the LAWA criteria and potentially harming the aquatic habitat. In addition, temporally growing organic matter contents in the lake sediments near the estuary of River Nzoia (from 4.2 to 17.6% in around 60 years) due to increased soil erosion in the river’s catchment area and blooms of the water hyacinth became visible. This study demonstrates that the whole catchment area is responsible to ensure a healthy aquatic ecosystem in Lake Victoria.