161. 题目: Insight into the adhesion propensities of extracellular polymeric substances (EPS) on the abiotic surface using XDLVO theory
期刊: Journal of Environmental Chemical Engineering
作者: Cheng-cheng Ji, Hu Zhou, Shao-kang Deng, Ke-yu Chen, Xiang-yu Dong, Xin-Hua Xu, Li-Hua Cheng
摘要: The microorganisms adhesion is ubiquitous and plays a central role in a wide spectrum of problems, including biomedical study, industrial application and environmental microbiology. To know more about mechanisms underlying microalgal early-stage adhesion, the soluble EPS (sEPS) and the bound EPS (bEPS) of Chlorella vulgaris were extracted and characterized for their adhesion behaviors on the hydrophilic polymethyl methacrylate (PMMA) and the hydrophobic polytetrafluoroethylene (PTFE) surfaces in this work. It was found that the sEPS and the bEPS were dominated by hydrophilic fractions (57.6%) and hydrophobic fractions (49.6%) respectively. As a result, the bEPS always showed a higher adhesion propensity than the sEPS, and the adhesion on PTFE was more significant than that on PMMA. According to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, the adhesion behavior was dominated by the Lewis acid-base interfacial free energy (∆GmwfAB) of algal EPS, and the bEPS could promote adhesive propensity, whereas the sEPS would repulse the hydrophilic surfaces. Additionally, the dissolved organic carbon (DOC) was shown to be a more suitable index for the description of EPS adhesion. This work presents evidence on the mechanisms of the EPS-mediated adhesion process in algal biofilm formation.
162. 题目: Quantitative contribution of minerals and organics in biochar to Pb(Ⅱ) adsorption: Considering the increase of oxygen-containing functional groups
期刊: Journal of Cleaner Production
作者: Liang Gao, Zhihe Li, Weiming Yi, Lihong Wang, Peng Zhang, Zhen Wan, Yufeng Li
摘要: An accurate method for understanding the contribution of minerals and organics in biochar to lead adsorption was proposed, while considering the effect of increased oxygen-containing functional groups (OFG). Biochar derived from cotton stalk was prepared by slow pyrolysis at 350 °C and 550 °C, and then the water-soluble matter (WM), acid-soluble matter (AM) and organic matter (OM) of biochar were separated by washing and pickling. Physicochemical properties and Pb2+ adsorption performance of pristine biochar (BC), water-washed biochar (WB) and acid-washed biochar (AB) have been investigated in detail. The order of the content of separated components in biochar was: OM＞AM＞WM, and the sequence of Pb2+ sorption capacity of biochar was: BC＞WB＞AB. The OFG content of all biochar before and after adsorption were quantified by Boehm titration, and the veracious sorption capacity of each fraction of biochar were acquired. The contribution of each component of biochar to Pb2+ sorption was ranked as: AM (69.49–72.69%)＞OM (23.93–27.51%)＞WM (3.00–3.39%). Furthermore, SEM-EDS, FTIR, XRD and other advanced technologies were used to characterize and analyze all biochar before and after adsorption, indicating that in the adsorption mechanism, minerals were related to ion exchange and precipitation, while organics were relevant to complexation and Pb2+-π interaction.
163. 题目: Nitrogen Recovery from Clear-Cut Forest Runoff Using Biochar: Adsorption–Desorption Dynamics Affected by Water Nitrogen Concentration
期刊: Water, Air, & Soil Pollution
作者: E. Kakaei Lafdani, Ari Laurén, Jovana Cvetkovic, Jukka Pumpanen, Taija Saarela, Marjo Palviainen
摘要: Forest regeneration operations increase the concentration of nitrogen (N) in watercourses especially outside the growing season when traditional biological water protection methods are inefficient. Biochar adsorption-based water treatment could be a solution for nutrient retention. We studied the total nitrogen (TN) and nitrate–nitrogen (NO 3 − –N) adsorption–desorption properties of spruce and birch biochar. The adsorption test was performed under four different initial concentrations of TN (1, 2, 3, and 4 mg L −1 ) using forest runoff water collected from ditch drains of boreal harvested peatland. The results showed that the TN adsorption amount increased linearly from the lowest to the highest concentration. The maximum adsorption capacity was 2.4 and 3.2 times greater in the highest concentration (4 mg L −1 ) compared to the lowest concentration (1 mg L −1 ) in spruce and birch biochar, respectively. The NO 3 − –N adsorption amount of birch biochar increased linearly from 0 to 0.15 mg NO 3 − –N g biochar −1 when the initial concentration of NO 3 − –N increased from 0.2 to 1.4 mg L −1 . However, in spruce biochar, the initial concentration did not affect NO 3 − –N adsorption amount. The results indicate that concentration significantly affects the biochar’s capacity to adsorb N from water. The desorption test was performed by adding biochar extracted from the adsorption test into the forest runoff water with low TN concentration (0.2 or 0.35 mg L −1 ). The desorption results showed that desorption was negligibly small, and it was dependent on the TN concentration for birch biochar. Therefore, biochar can be a complementary method supporting water purification in peatland areas.
164. 题目: Selective As( v ) capture by a novel magnetic green Fe-biochar composite in a packed column: an application of central composite design
期刊: Environmental Science: Water Research & Technology
作者: Ghazi Mohd Sawood, Shobhit Dixit, Gaurav Mishra, S. K. Gupta
摘要: Arsenic contamination in groundwater is a prominent global issue due to its substantial toxicological impacts on the environment and human health. Herein, a fixed-bed column experiment was carried out for feasibility analysis of using a novel Fe-impregnated Azadirachta indica biochar matrix for arsenate removal. The adsorbent was characterized by SEM, EDAX, BET, XRD, TGA, VSM, and XPS analysis. Statistical RSM with central composite design is applied to examine the synergistic effects of process parameters on the adsorption of arsenate. A high R2 value of 0.994 predicted by ANOVA established the adequate regression of the proposed model. At a bed height of 18.0 cm, flow rate of 3.0 mL min−1, pH 7 and initial arsenate concentration of 500 μg L−1, the arsenate uptake capacity of Fe-AIB was found to be 149 μg g−1. Various mathematical models including the Thomas, Yoon Nelson, Adams–Bohart and BDST models were used to analyse the column experiment data. The Thomas model best defines the nature of the breakthrough curves at various conditions. The BDST model manifested good agreement with experimental results and obtained high R2 values, showing the significant applicability of this model for the current fixed-bed column system. The regeneration of columns was conducted using 10% NaOH.
165. 题目: Acid-base properties of Synechococcus-derived organic matter
期刊: Geochimica et Cosmochimica Acta
作者: Logan Swaren, Daniel S. Alessi, George W. Owttrim, Kurt O. Konhauser
摘要: Marine cyanobacteria play an important role in trace metal cycling in the oceans. However, the influence of bacterial detritus following cell lysis - that includes both particulate organic matter (POM) and dissolved organic matter (DOM) - is less understood. Previous investigations have shown that the ratio of bacterial detritus to living cells increases significantly with ocean depth, indicating that the former plays a central role in trace metal cycling and eventual sequestration in deep marine sediments. Thus, in this study we produced detritus from the mechanical lysis of the common marine cyanobacterium Synechococcus sp. PCC 7002 (referred to as cyPOM and cyDOM), and then measured their buffering capacity through proton adsorption and release via potentiometric acid-base titrations. Both cyPOM and cyDOM were best modelled using a 2-site non-electrostatic protonation model. The cyPOM fraction possessed ligands with pKa values of 5.78 (±0.07) and 9.01 (±0.29) with corresponding site concentrations of 41.8 (±8.15) µmol g-1 and 41.2 (±5.28) µmol g-1, while cyDOM had pKa values of 4.89 (±0.22) and 6.80 (±0.22) and corresponding site concentrations of 42.8 (±14.6) µmol g-1 and 37.3 (±16.5) µmol g-1. As a comparison, intact Synechococcus cells were previously reported to be best modelled by invoking 3-sites with overall ligand densities more than double that of cyPOM and cyDOM. Trace metal (Cd, Co, Cu, Ni, and Zn) adsorption experiments indicate that cyPOM has a lower affinity towards trace metals than intact Synechococcus cells, evidenced by lower trace metals adsorption per gram of dry mass and therefore less trace metal sequestration potential. This implies that intact Synechococcus cells are chiefly responsible for trace metal sequestration, even at high cyPOM proportions (10:1 – cyPOM:Synechococcus) that are more representative of POM that reaches the seafloor. The cyDOM-trace metal association could not be determined experimentally; thus we applied existing thermodynamic data from modern marine DOM studies acquired via potentiometric titrations and metal-binding constants. Unlike cyPOM, metal speciation is almost entirely accounted for in the dissolved fraction (>99.9%). These results further the view that DOM is the most important microbial fraction in controlling metals speciation in the water column.
166. 题目: Organic Chloramines Formation from Algal Organic Matters: Insights from Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry
期刊: Water Research
作者: Da Sheng, Lingjun Bu, Shumin Zhu, Yangtao Wu, Jue Wang, Shiqing Zhou
摘要: Release of algal organic matter (AOM) from algae poses great threats to drinking water safety. As organic nitrogen in AOM is relatively higher compared to natural organic matter (NOM), the organic chloramine formation during chlorination cause overestimation of effective chlorine, which may lead to a biological risk. This study compared the organic chloramine formation from AOM and NOM, and confirmed that AOM tend to form more organic chloramines during chlorination. Furthermore, it was found that hydrophilic fraction and high molecular weight (>100 kDa) fraction of AOM generated major organic chloramines due to a high content of protein. Based on the results of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), Spearman's rank correlation was used to analyze the relationship between molecular composition of AOM and organic chloramine formation. Notably, molecules with high correlation to organic chloramine formation located in a triangle region of van Krevelen diagram, which is a typical area of peptides. Therefore, it indicates that the precursors of organic chloramine in AOM are mainly proteins/peptides, and appropriate treatment processes (e.g., biological treatment or membrane filtration) should be addressed to effectively remove the precursors before chlorination.
167. 题目: The effect of coagulation on the removal of algogenic organic matter and the optical parameters for predicting disinfection byproducts
期刊: Separation and Purification Technology
作者: Lingfei Ma, Fangyuan Peng, Yi Lu, Zhaoguang Yang, Bo Qiu, Haipu Li
摘要: Algae-derived disinfection byproducts (DBPs) are receiving increasing attention. Coagulation is the first water treatment section in removing algogenic organic matter (AOM). However, there is a significant knowledge gap in the effects of coagulation on DBPs produced from AOM. In this study, in view of the multi-component AOM, several analysis methods were combined to investigate the changes in AOM of Microcystic aeruginosa during the coagulation treatment, including ultraviolet-visible absorbance, multi-peaks Gaussian fitting method based on differential absorption spectroscopy, Excitation-emission matrix, and Fourier transform infrared spectroscopic analysis. To identify the characteristic parameters that could indicate the formation of DBPs, the yields of twenty-one DBP species produced from the residual AOM after the coagulation treatment were investigated. The correlations between DBPs and the spectral parameters were also analyzed. The results showed that aluminum salt coagulant could significantly remove protein-like compounds, chlorophyll, and phycocyanin in AOM, but it had a limited ability to precipitate AOM. With the increase of aluminum sulfate coagulant, the yields of DBPs produced from the residual extracellular organic matter decreased, while those produced from the residual intracellular organic matter decreased firstly and then gradually increased. The Pearson’s correlation results showed that the combination of fluorescent regions of protein-like, humic acid-like, and humic acid-like could be used as an optical surrogate for predicting the formation of DBPs.
168. 题目: Labile substrate stoichiometry alters microbial respiration and bacterial community dynamics across four different ecosystems
期刊: Soil Biology and Biochemistry
作者: Xiao Jun Allen Liu, Michaela Hayer, Rebecca L. Mau, Egbert Schwartz, Paul Dijkstra, Bruce A. Hungate
摘要: Microbes decompose soil organic matter (SOM), yet it is unclear how substrate inputs (i.e., stoichiometry) directly mediate microbial respiration and community dynamics. We hypothesized that C + N input has the largest effect on microbial respiration and community structure, followed by C input and N input. Soils were collected from four ecosystems (grassland, piñon-juniper, ponderosa pine, mixed conifer) and amended with NH4NO3 (N only; 100 μg g−1 wk−1), 13C-glucose (C only; 1000 μg g−1 wk−1), or C + N in a five-week laboratory incubation. We found that C + N input induced the greatest total respiration while C input induced the greatest SOM-derived respiration (i.e., priming effect) across ecosystems. Shifts in community composition were the largest with C + N input, followed by C input, and showed little response to N input. C only and C + N inputs increased both of the relative and absolute abundances of Actinobacteria and Proteobacteria (α, β, γ), but reduced the relative abundances of Verrucomicrobia and δ-Proteobacteria. C + N input increased the relative abundances of Bacillales, Rhizobiales, Burkholderiales and of 9 families, and reduced the relative abundances of Myxococcales and of 12 families, but showed little effect on the absolute abundances of these bacterial taxa. N input reduced the absolute abundances of Actinobacteria, Proteobacteria, and Verrucomicrobia but did not affect their relative abundances in the mixed conifer soil; by contrast, N input reduced relative abundances of δ-Proteobacteria and increased the relative abundances of γ-Proteobacteria but did not affect their absolute abundances in the ponderosa pine soil. We also found that substrate inputs were the main driver of SOM decomposition, microbial respiration and diversity, while soil ecosystem was the main driver of community composition and abundances of most bacterial phyla. Our work suggests that substrate stoichiometry has predictable effects on soil carbon cycling, microbial diversity and community composition, but has variable effects on microbial abundances, and that incorporating bacterial gene copies in abundance calculations can help more accurately estimate microbial responses across taxonomic levels and ecosystems.
169. 题目: Total phosphorus records in coastal Antarctic sediments: Burial and evidence of anthropogenic influence on recent input
期刊: Marine Chemistry
作者: Felipe S. Freitas, Rosalinda C. Montone, Eunice C. Machado, César C. Martins
摘要: Total phosphorus (TP) records reflect variations in input and burial of organic matter (OM) in coastal and shelf sediments. At Antarctic regions, TP levels are often derived from natural sources; however, with emergent human pressure at these regions, anthropogenic sources of TP may play an important role. At the Antarctic Peninsula, Admiralty Bay attracts great scientific and touristic interest, especially during austral summer months, thus being vulnerable to human activities. Currently, only scarce spatial distributions of TP are available for this key region, whereas no vertical distributions have been determined. To fill this gap, we investigated short (< 20 cm) sediment cores in ten areas along Admiralty Bay for TP contents. We produced the first TP vertical distributions and established site-specific background values (from 492 ± 13 to 932 ± 17 μg g−1), which are related to hydrodynamics, sedimentology, and natural inputs of P. We observed a gradual surface TP enrichment at all sites, mainly due to input of fresh OM. Benefiting from our background values, we employ the Phosphorus Pollution Index (PPI) to assess possible human impacts. Generally, the increase of PPI suggests natural inputs of P. However, PPI ≥ 1.3 found at the nearby Comandante Ferraz Research Station (Brazil) can be linked to recent (past 2–3 decades) treated sewage inputs in Martel Inlet. We suggest PPI as a proxy for preliminary assessments of anthropogenic impacts in coastal Antarctic regions experiencing increased human pressure.
170. 题目: Geochemical dynamics and depositional history from mangrove sediments within the Pearl River estuary
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Yiying Sun, Haixian Xiong, Man-Ting Lee, Chris Brodie, Yongqiang Zong
摘要: This study investigated the geochemical dynamics of sediment organic matter (OM) and examined the usefulness of sedimentary OM δ13C, TOC and C/N proxies for reconstructions of the depositional history from mangrove sediments in a coastal site of the Pearl River mouth region. The analyses of the δ13C, TOC and C/N from plant leaves and sediment OM of three mangrove vegetation zones (mudflat with macro-algae, mangrove forest and supratidal mixed forest) across a mangrove wetland indicate significant exchanges of mangrove OM with marine aquatic algal OM and mixed forest plant OM caused by tidal currents and freshwater discharge in both landward and seaward directions. Despite the OM exchanges, the δ13C, TOC and C/N of modern surface sediments show values distinctive between mudflat, mangrove and mixed forest zones. Specifically, these three signatures appear as −24.3 ± 0.5‰, 1.6 ± 0.2% and 4.4 ± 1.3 for mudflat sediment, −26.8 ± 0.4‰, 3.1 ± 0.7% and 8.6 ± 1.6 for mangrove sediment, and −28.5 ± 0.5‰, 8.4 ± 2.2% and 11.9 ± 2.0 for mixed forest sediment. Such clear divisions of sediment OM signatures between vegetational zones confirm their usefulness as coastal environmental proxies. Together with the chronologies based on radiocarbon, 210Pb and 137Cs analyses, these proxies were successfully applied to sediment cores to reconstruct the mangrove wetland's depositional history in the past century. This study has enhanced our understanding on organic geochemical dynamics in mangrove environments, and the improved reconstruction provides new insights into environmental responses to natural and anthropogenic drivers.
171. 题目: Selecting environmental factors to predict spatial distribution of soil organic carbon stocks, northwestern Iran
期刊: Environmental Monitoring and Assessment
作者: Kamal Khosravi Aqdam, Nafiseh Yaghmaeian Mahabadi, Hassan Ramezanpour, Salar Rezapour, Zohreh Mosleh
摘要: Knowledge of environmental factors controlling soil organic carbon (SOC) stocks can help predict spatial distribution SOC stocks. So, this study was carried out to select the best environmental factors to model and estimate the spatial distribution of SOC stocks in northwestern Iran. Soil sampling was performed at 210 points by multiple conditioned Latin Hypercube method (cLHm) and SOC stocks were measured. Also, environmental factors, including terrain attributes, moisture index, and normalized difference vegetation index (NDVI), were calculated. SOC stocks were modeled using random forest (RF) and partial least squares regression (PLSR) models. Modeling SOC stocks by RF model showed that the efficient factors for estimating the SOC stocks were slope height (slph), terrain surface texture (texture), standardized height (standh), elevation, relative slope position (rsp), and normalized height (normalh). Also, the PLSR model selected standardized height (standh), relative slope position (rsp), slope, and channel network base level (chnl base) to model SOC stocks. In both RF and PLSR methods, the standh and rsp factors were suitable parameters for estimating the SOC stocks. Predicting the spatial distribution of SOC stocks using environmental factors showed that the R2 values for RF and PLSR models were 0.81 and 0.40, respectively. The result of this study showed that in areas with complex land features, terrain attributes can be good predictors for estimating SOC stocks. These predictors allow more accurate estimates of SOC stocks and contribute considerably to the effective application of land management strategies in arid and semiarid area.
172. 题目: Shaping of soil microbial communities by plants does not translate into specific legacy effects on organic carbon mineralization
期刊: Soil Biology and Biochemistry
作者: Eve Hellequin, Françoise Binet, Olivier Klarzynski, Sara Hallin, Jaanis Juhanson, Virginie Daburon, Cécile Monard
摘要: Plants shape soil microbial communities through their root architecture, their rhizodeposits and return of dead plant material to the soil. These interactions can have a strong influence on the soil organic carbon dynamics. However, it is unclear whether the plant species effects on the soil microbial community could influence the organic carbon mineralization through plant legacy effects. Therefore, we examined how and to what extent a short-term plant growing phase affected the total and active soil microorganisms and through a possible plant legacy, also the mineralization of soil organic carbon, a central ecosystem function. Using a controlled pot experiment, we first showed that the two phylogenetically distinct plants, Arabidopsis thaliana and Triticum aestivum, differently shaped the soil microbial communities when recruiting from the same soil community. Although both plants recruited plant-growth promoting bacteria in the vicinity of their roots, A. thaliana had a stronger effect than T. aestivum and also recruited saprophytic fungi, while inhibiting fungal pathogens. Due to plant legacy effects on the soil microbial communities, different microbial successions occurred in the two previously planted soils when subjected to plant litter. By contrast, plant legacy effects on soil basal respiration were not plant-specific, with basal respiration increasing similarly in both cases and moreover did not translate to changes in litter carbon mineralization in the short-term of 49 days. Our results suggest that the soil nutrient dynamics rather than changes in soil microbial community composition drive the organic carbon mineralization of added litter. The present study brings new insights in how the relationships between plants, microorganisms and soil nutrient dynamics affect litter carbon cycling.
173. 题目: Particulate organic carbon dynamics in the Gulf of Lion shelf (NW Mediterranean) using a coupled hydrodynamic–biogeochemical model
作者: Gaël Many, Caroline Ulses, Claude Estournel, Patrick Marsaleix
摘要: The Gulf of Lion shelf (GoL, NW Mediterranean) is one of the most productive areas in the Mediterranean Sea. A 3D coupled hydrodynamic–biogeochemical model is used to study the mechanisms that drive the particulate organic carbon (POC) dynamics over the shelf. A set of observations, including temporal series from a coastal station, remote sensing of surface chlorophyll a, and a glider deployment, is used to validate the distribution of physical and biogeochemical variables from the model. The model reproduces the time and spatial evolution of temperature, chlorophyll a, and nitrate concentrations well and shows a clear annual cycle of gross primary production and respiration. We estimate an annual net primary production of ∼ 200 × 104 t C yr−1 at the scale of the shelf. The primary production is marked by a coast-slope increase with maximal values in the eastern region. Our results show that the primary production is favoured by the inputs of nutrients imported from offshore waters, representing 3 and 15 times the inputs of the Rhône in terms of nitrate and phosphate. In addition, the empirical orthogonal function (EOF) decomposition highlights the role of solar radiation anomalies and continental winds that favour upwellings, and inputs of the Rhône River, in annual changes in the net primary production. Annual POC deposition (27 × 104 t C yr−1) represents 13 % of the net primary production. The delivery of terrestrial POC favours the deposition in front of the Rhône mouth, and the mean cyclonic circulation increases the deposition between 30 and 50 m depth from the Rhône prodelta to the west. Mechanisms responsible for POC export (24 × 104 t C yr−1) to the open sea are discussed. The export off the shelf in the western part, from the Cap de Creus to the Lacaze-Duthiers canyon, represents 37 % of the total POC export. Maximum values are obtained during shelf dense water cascading events and marine winds. Considering surface waters only, the POC is mainly exported in the eastern part of the shelf through shelf waters and Rhône inputs, which spread to the Northern Current during favourable continental wind conditions. The GoL shelf appears as an autotrophic ecosystem with a positive net ecosystem production and as a source of POC for the adjacent NW Mediterranean basin. The undergoing and future increase in temperature and stratification induced by climate change could impact the trophic status of the GoL shelf and the carbon export towards the deep basin. It is crucial to develop models to predict and assess these future evolutions.
174. 题目: Harvesting of different microalgae through 100-μm-pore-sized screen filtration assisted by cationic polyacrylamide and specific extracellular organic matter
期刊: Separation and Purification Technology
作者: Qijia Cai, Kezheng Song, Pei Cai, Cuicui Tian, Chunbo Wang, Bangding Xiao
摘要: Cationic polyacrylamide (CPAM) can induce efficient harvest of microalgae at low dosages (0.5-2 mg/L), and the large flocs that form as a result are beneficial for later screen filtration. However, flocculation is dependent on the microalgae species, especially their extracellular organic matter (EOM). In this study, harvesting of microalgae with CPAM flocculation and screen filtration (100-μm pore size) was compared, using four cyanobacteria species (Microcystis aeruginosa, M. wesenbergii, Cylindrospermopsis raciborskii, and Phormidium ambiguum) and three green algae species (Chlorella vulgaris, Scenedesmus quadricauda, and Pediastrum duple). The influence of EOM concentration and characteristics (i.e. charge density and molecular weight) was of particular focus in this study. All cyanobacteria were effectively flocculated with 1-2 mg/L CPAM, though the retention of C. raciborskii (78%) was significantly lower than the others (>90%). For green algae, only Ch. vulgaris could be effectively flocculated with retention >90%, but a higher CPAM dosage (4 mg/L) was required. When mixed with EOM of other microalgae, the retention of S. quadridcauda and P. duple increased to >78%. Successful retention was highly correlated with high molecular weight (MW) and negative charge density of the EOM. The >100 kDa EOM fractions were responsible for effective retention of cyanobacteria and 30-100 kDa EOM fractions for Ch. vulgaris, while these fractions were rarely present in the EOM of S. quadricauda and P. duple. Though effective for cyanobacteria, the application of CPAM flocculation and screen filtration for harvesting some green algae is limited due to a lack of high-MW and negatively charged EOM components.
175. 题目: Adsorption isotherms and kinetics for the removal of algal organic matter by granular activated carbon
期刊: Science of The Total Environment
作者: Ziming Zhao, Wenjun Sun, Madhumita B. Ray
摘要: Seasonal algal blooms in surface water release a significant amount of algal organic matter (AOM), which alters the composition of dissolved organic matter (DOM). AOM affects the drinking water treatment processes and finished water quality. In this study, the relative removal efficiency of AOM and humic acid by granular activated carbon (GAC) adsorption was determined. Batch experiments were conducted to evaluate the adsorption capacity of GAC, which varied from 4.235–31.45 mg/g for AOM originated from different algae. Freundlich isotherm models fitted the adsorption equilibrium data, and the adsorption kinetics data were fitted well using a pseudo-second order kinetic model. The calculated thermodynamics parameters (∆G0, ∆H0 and ∆S0) indicated that GAC adsorption for DOM removal was endothermic and spontaneous in nature.
176. 题目: Combined biochar and double inhibitor application offsets NH3 and N2O emissions and mitigates N leaching in paddy fields
期刊: Environmental Pollution
作者: Tiehu He, Junji Yuan, Jian Xiang, Yongxin Lin, Jiafa Luo, Stuart Lindsey, Xia Liao, Deyan Liu, Weixin Ding
摘要: The effects of combined biochar and double inhibitor application on gaseous nitrogen (N; nitrous oxide [N2O] and ammonia [NH3]) emissions and N leaching in paddy soils remain unclear. We investigated the effects of biochar application at different rates and double inhibitor application (hydroquinone [HQ] and dicyandiamide [DCD]) on NH3 and N2O emissions, N leaching, as well as rice yield in a paddy field, with eight treatments, including conventional urea N application at 280 kg N ha−1 (CN); reduced N application at 240 kg N ha−1 (RN); RN + 7.5 t ha−1 biochar (RNB1); RN + 15 t ha−1 biochar (RNB2); RN + HQ + DCD (RNI); RNB1 + HQ + DCD (RNIB1); RNB2 + HQ + DCD (RNIB2); and a control without N fertilizer. When compared with N leaching under RN, biochar application reduced total N leaching by 26.9–34.8% but stimulated NH3 emissions by 13.2–27.1%, mainly because of enhanced floodwater and soil NH4+-N concentrations and pH, and increased N2O emission by 7.7–21.2%, potentially due to increased soil NO3−-N concentrations. Urease and nitrification inhibitor addition decreased NH3 and N2O emissions, and total N leaching by 20.1%, 21.5%, and 22.1%, respectively. Compared with RN, combined biochar (7.5 t ha−1) and double inhibitor application decreased NH3 and N2O emissions, with reductions of 24.3% and 14.6%, respectively, and reduced total N leaching by up to 45.4%. Biochar application alone or combined with double inhibitors enhanced N use efficiency from 26.2% (RN) to 44.7% (RNIB2). Conversely, double inhibitor application alone or combined with biochar enhanced rice yield and reduced yield-scaled N2O emissions. Our results suggest that double inhibitor application alone or combined with 7.5 t ha−1 biochar is an effective practice to mitigate NH3 and N2O emission and N leaching in paddy fields.
177. 题目: Effective prediction of soil organic matter by deep SVD concatenation using FT-NIR spectroscopy
期刊: Soil and Tillage Research
作者: Hanli Qiao, Xiubo Shi, Huazhou Chen, Jingyi Lyu, Shaoyong Hong
摘要: Soil organic matters (SOM), specifically carbon and nitrogen, bring numerous benefits to soil’s physical and chemical properties. In this paper, we employ spectral data obtained by Fourier transform near-infrared (FT-NIR) spectroscopy to predict the content of organic carbon (OC) and total nitrogen (TN) in mineral soils. To address the limitation generated by massive hyperparameters on convolution neural network (CNN), we substitute using a technique named SVD concatenation to learn features. The proposed model combines the layers of fully connected and regression to complete the prediction task. We abbreviate it as SVD-CNN, which is capable provide a multi-tasks output simultaneously. In experiments, we study the prediction performances of SVD-CNN on two datasets of FT-NIR and LUCAS 2009 topsoil. Based on different situations, the highest performance of R2 achieves 0.8891 for OC and 0.9048 for TN on the FT-NIR dataset. Similarly, the most prominent results on the LUCAS 2009 topsoil dataset are R2 = 0.9304, RMSE = 3.6014 for OC and R2 = 0.9319, RMSE = 0.2733 for TN. Furthermore, we also evaluate the results obtained by solely using SVD concatenation, which reveals SVD-CNN performs a better generalization ability.
178. 题目: Sources of riverine mercury across the Mackenzie River Basin; inferences from a combined Hg C isotopes and optical properties approach
期刊: Science of The Total Environment
作者: Audrey Campeau, Karin Eklöf, Anne L. Soerensen, Staffan Åkerblom, Shengliu Yuan, Holger Hintelmann, Magdalena Bieroza, Stephan Köhler, Christian Zdanowicz
摘要: The Arctic terrestrial environment harbors a complex mosaic of mercury (Hg) and carbon (C) reservoirs, some of which are rapidly destabilizing in response to climate warming. The sources of riverine Hg across the Mackenzie River basin (MRB) are uncertain, which leads to a poor understanding of potential future release. Measurements of dissolved and particulate mercury (DHg, PHg) and carbon (DOC, POC) concentration were performed, along with analyses of Hg stable isotope ratios (incl. ∆199Hg, δ202Hg), radiocarbon content (∆14C) and optical properties of DOC of river water. Isotopic ratios of Hg revealed a closer association to terrestrial Hg reservoirs for the particulate fraction, while the dissolved fraction was more closely associated with atmospheric deposition sources of shorter turnover time. There was a positive correlation between the ∆14C-OC and riverine Hg concentration for both particulate and dissolved fractions, indicating that waters transporting older-OC (14C-depleted) also contained higher levels of Hg. In the dissolved fraction, older DOC was also associated with higher molecular weight, aromaticity and humic content, which are likely associated with higher Hg-binding potential. Riverine PHg concentration increased with turbidity and SO4 concentration. There were large contrasts in Hg concentration and OC age and quality among the mountain and lowland sectors of the MRB, which likely reflect the spatial distribution of various terrestrial Hg and OC reservoirs, including weathering of sulfate minerals, erosion and extraction of coal deposits, thawing permafrost, forest fires, peatlands, and forests. Results revealed major differences in the sources of particulate and dissolved riverine Hg, but nonetheless a common positive association with older riverine OC. These findings reveal that a complex mixture of Hg sources, supplied across the MRB, will contribute to future trends in Hg export to the Arctic Ocean under rapid environmental changes.
179. 题目: Freeze-thaw controlled aggregation mechanism of humic acid-coated goethite: Implications for organic carbon preservation
作者: Sensen Wu, Chengshuai Liu, Xiaoguang Li, Baohua Xiao, Qingyang Hu
摘要: Organic carbon sequestered in soil aggregate contributes significantly to the carbon preservation on the earth’s surface. However, the turnover of soil aggregate in high latitudes and cold zones is strongly affected by the frequency of freeze–thaw cycles and may be disturbed by climate change. Although the effects of recurrent freeze–thaw cycles on the size, structure, and stability of soil aggregate have been well studied, the aggregation of individual mineral particles adsorbed by organic carbon and its mechanism are not yet conclusive. Here, we report that more than 97 wt% of the humic acid-coated goethite (goethite-HA) particles can aggregate into aggregates of different sizes and morphologies through one freeze–thaw cycle (freezing at −24°C for 12 h and thawing at 4 °C for 12 h). Combining electron microscopy, infrared absorption spectroscopy and thermogravimetric analysis, we revealed that goethite-HA particles could strongly complex with each other after one freeze–thaw cycle. Compared with previous studies, our results showed that both electrostatic repulsion and steric hindrance (known to prevent aggregation) were overcome by the internal thrust of ice exclusion during freezing, then goethite-HA particles could be interconnected through the carboxyl-iron and hydrogen bonding to form aggregates. We believe that aggregates formed during the freeze–thaw cycles in soils rich in iron (hydr)oxides can serve as shelters for soil organic carbon and may reduce CO2 emissions in these soils.
180. 题目: Lignin-derived biochar to support CoFe2O4: Effective activation of peracetic acid for sulfamethoxazole degradation
期刊: Chemical Engineering Journal
作者: Jie Dong, Weihua Xu, Shaobo Liu, Youzi Gong, Ting Yang, Li Du, Qiang Chen, Xiaofei Tan, Yunguo Liu
摘要: The conversion of biomass wastes to highly efficient biochar-based catalysts has attracted more and more attention because it meets the environmental protection concept of waste recycling. In this work, a novel magnetic catalyst (CoFe2O4@BC) was developed by using alkaline lignin, the dominant by-products of papermaking industry, as feedstock for biochar. More importantly, PAA (CH3C(=O) OOH) was successfully activated by CoFe2O4@BC nanoparticles for sulfamethoxazole (SMX) elimination. The catalytic activity of CoFe2O4@BC on PAA activation was systematically studied. When PAA was 825 μM and CoFe2O4@BC was 100 mg/L, 10 mg/LSMX could be completely degraded. The cycle of Co3+/Co2+ of CoFe2O4@BC prompted the generation of acetyl(per)oxyl groups (CH3C(O)O• and CH3C(O)OO•), which were believed to be the dominant reactive substances for SMX degradation. The degradation of SMX was promoted under near-neutral pH conditions, and was inhibited when humic acid and HCO3− were added, while the Cl− showed a negligible influence. According to the analysis of oxidation products, three main transformation pathways of SMX were illustrated. The remarkable stability and magnetic separability of CoFe2O4@BC make it have a wider application prospect in the treatment of various wastewater.