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17341. 题目: Enhanced phosphate scavenging with effective recovery by magnetic porous biochar supported La(OH)3: Kinetics, isotherms, mechanisms and applications for water and real wastewater
文章编号: N20101504
期刊: Bioresource Technology
作者: Ying Zhang, Modupe Sarah Akindolie, Xue Tian, Bin Wu, Qi Hu, Zhao Jiang, Lei Wang, Yue Tao, Bo Cao, Jianhua Qu
更新时间: 2020-10-15
摘要:

Herein, La(OH)3 decorated magnetic porous biochar (MPBC) was synthesized via KHCO3 activation and hydrothermal processes. The La-to-MPBC mass ratio of 3:1 described as La3-MPBC possessed a monolayer phosphate adsorption capacity of 116.08 mg/g across a pH range of 3.0–6.0 with fast attainment of adsorption equilibrium in 150 min. Moreover, the phosphate adsorption was substantially stable during the interference of various co-existing ions with over 92% of phosphate removal and 77% of desorption efficiency maintained after four recycles. And La3-MPBC was easily separated by magnet force with negligible La and Fe leakages within the pH range of 3.0–10.0. Furthermore, La3-MPBC was supported to achieve phosphate binding through the synergistic actions of electrostatic attraction, ligand exchange, inner-sphere complexation and weak precipitation. Significantly, La3-MPBC exhibited a high performance for decontaminating low-concentration phosphate to meet regulatory requirements. All these results suggested La3-MPBC to be an ideal candidate for phosphate removal in real applications.

17342. 题目: Biochar and activated carbon enhance ethanol conversion and selectivity to caproic acid by Clostridium kluyveri
文章编号: N20101503
期刊: Bioresource Technology
作者: Stef Ghysels, Sara Buffel, Korneel Rabaey, Frederik Ronsse, Ramon Ganigué
更新时间: 2020-10-15
摘要:

Syngas from biomass or steel mills can be fermented into a dilute stream of ethanol and acetic acid, which requires energy intensive distillation for product recovery. This can be circumvented by selective secondary fermentation of the syngas fermentation effluent to caproic acid as easier recoverable platform chemical with Clostridium kluyveri. Here, we explore the impact of biochar and activated carbon on this process. Changes during the fermentation with biochar or activated carbon were monitored, different doses were tested and the recyclability of biochar and activated carbon was assessed. Biochar decreased the lag phase and increased the caproic acid production rate (up to 0.50 g·L-1·h-1). Upon recycling for subsequent fermentation, biochar retained this property largely. Activated carbon addition, especially at high dose, could potentially increase the conversion and selectivity towards caproic acid to 14.15 g·L-1 (control: 11.01 g·L-1) and 92% (control: 84%), respectively.

17343. 题目: The dynamics and stoichiometry of dissolved organic carbon release by kelp
文章编号: N20101502
期刊: Ecology
作者: Brooke L. Weigel, Catherine A. Pfister
更新时间: 2020-10-15
摘要: Canopy‐forming kelps are foundational species in coastal ecosystems, fixing tremendous amounts of carbon, yet we know little about the ecological and physiological determinants of dissolved organic carbon (DOC) release by kelps. We examined DOC release by the bull kelp, Nereocystis luetkeana, in relation to carbon fixation, nutrient uptake, tissue nitrogen content, and light availability. DOC release was approximately 3.5 times greater during the day than at night. During the day, N. luetkeana blades released an average of 16.2% of fixed carbon as DOC. Carbon fixation increased with light availability but DOC release did not, leading to a lower proportion of fixed carbon released as DOC at high light levels. We found no relationship between carbon fixation and DOC release rates measured concurrently. Rather, DOC release by N. luetkeana blades declined with marginal significance as blade tissue nitrogen content increased and with experimental nitrate addition, supporting the role of stoichiometric relationships in DOC release. Using a stable isotope (13C) tracer method, we demonstrated that inorganic carbon is rapidly fixed and released by N. luetkeana blades as 13DOC, within hours. However, recently fixed carbon (13DOC) comprised less than 20% of the total DOC released, indicating that isotope studies that rely on tracer production alone may underestimate total DOC release, as it is decoupled from recent kelp productivity. Comparing carbon and nitrogen assimilation dynamics of the annual kelp N. luetkeana with the perennial kelp Macrocystis pyrifera revealed that N. luetkeana had significantly higher carbon fixation, DOC production and nitrogen uptake rates per unit dry mass. Both kelp species were able to perform light‐independent carbon fixation at night. Carbon fixation by the annual kelp N. luetkeana is as high as 2.35 kg C m‐2 yr‐1, but an average of 16% of this carbon (376 g C m‐2 yr‐1) is released as DOC. As kelp forests are increasingly viewed as vehicles for carbon sequestration, it is important to consider the fate of this substantial quantity of DOC released by canopy‐forming kelps.

17344. 题目: Characterization of graphene/pine wood biochar hybrids: Potential to remove aqueous Cu2+
文章编号: N20101501
期刊: Environmental Research
作者: Hasara Samaraweera, Charles U. Pittman, Rooban Venkatesh K G Thirumalai, El Barbary Hassan, Felio Perez, Todd Mlsna
更新时间: 2020-10-15
摘要:

Biochar-based hybrid composites containing added nano-sized phases are emerging adsorbents. Biochar, when functionalized with nanomaterials, can enhance pollutant removal when both the nanophase and the biochar surface act as adsorbents. Three different pine wood wastes (particle size < 0.5 mm, 10 g) were preblended with 1 wt% of three different graphenes in aqueous suspensions, designated as G1, G2, and G3. G1 (SBET, 8.1 m2/g) was prepared by sonicating graphite made from commercial synthetic graphite powder (particle size 7–11 μm). G2 (312.0 m2/g) and G3 (712.0 m2/g) were purchased commercial graphene nanoplatelets (100 mg in 100 mL deionized water). These three pine wood-graphene mixtures were pyrolyzed at 600 °C for 1 h to generate three graphene-biochar adsorbents, GPBC-1, GPBC-2, and GPBC-3 containing 4.4, 4.9, and 5.0 wt% of G1, G2, and G3 respectively. Aqueous Cu2+ adsorption capacities were 10.6 mg/g (GPBC-1), 4.7 mg/g (GPBC-2), and 5.5 mg/g (GPBC-3) versus 7.2 mg/g for raw pine wood biochar (PBC) (0.05 g adsorbent dose, Cu2+ 75 mg/L, 25 mL, pH 6, 24 h, 25 ± 0.5 °C). Increased graphene surface areas did not result in adsorption increases. GPBC-1, containing the lowest nanophase surface area with the highest Cu2+ capacity, was chosen to evaluate its Cu2+ adsorption characteristics further. Results from XPS showed that the surface concentration of oxygenated functional groups on the GPBC-1 is greater than that on the PBC, possibly contributing to its greater Cu2+ removal versus PBC. GPBC-1 and PBC uptake of Cu2+ followed the pseudo-second-order kinetic model. Langmuir maximum adsorption capacities and BET surface areas were 18.4 mg/g, 484.0 m2/g (GPBC-1) and 9.2 mg/g, 378.0 m2/g (PBC). This corresponds to 3.8 × 10−2 versus 2.4 × 10−2 mg/m2 of Cu2+ removed on GPBC-1 (58% more Cu2+ per m2) versus PBC. Cu2+ adsorption on both these adsorbents was spontaneous and endothermic.

17345. 题目: Prediction of soil organic carbon and the C:N ratio on a national scale using machine learning and satellite data: A comparison between Sentinel-2, Sentinel-3 and Landsat-8 images
文章编号: N20101414
期刊: Science of the Total Environment
作者: Tao Zhou, Yajun Geng, Cheng Ji, Xiangrui Xu, Hong Wang, Jianjun Pan, Jan Bumberger, Dagmar Haase, Angela Lausch
更新时间: 2020-10-14
摘要:

Soil organic carbon (SOC) and soil carbon-to-nitrogen ratio (C:N) are the main indicators of soil quality and health and play an important role in maintaining soil quality. Together with Landsat, the improved spatial and temporal resolution Sentinel sensors provide the potential to investigate soil information on various scales. We analyzed and compared the potential of satellite sensors (Landsat-8, Sentinel-2 and Sentinel-3) with various spatial and temporal resolutions to predict SOC content and C:N ratio in Switzerland. Modeling was carried out at four spatial resolutions (800 m, 400 m, 100 m and 20 m) using three machine learning techniques: support vector machine (SVM), boosted regression tree (BRT) and random forest (RF). Soil prediction models were generated in these three machine learners in which 150 soil samples and different combinations of environmental data (topography, climate and satellite imagery) were used as inputs. The prediction results were evaluated by cross-validation. Our results revealed that the model type, modeling resolution and sensor selection greatly influenced outputs. By comparing satellite-based SOC models, the models built by Landsat-8 and Sentinel-2 performed the best and the worst, respectively. C:N ratio prediction models based on Landsat-8 and Sentinel-2 showed better results than Sentinel-3. However, the prediction models built by Sentinel-3 had competitive or better accuracy at coarse resolutions. The BRT models constructed by all available predictors at a resolution of 100 m obtained the best prediction accuracy of SOC content and C:N ratio; their relative improvements (in terms of R2) compared to models without remote sensing data input were 29.1% and 58.4%, respectively. The results of variable importance revealed that remote sensing variables were the best predictors for our soil prediction models. The predicted maps indicated that the higher SOC content was mainly distributed in the Alps, while the C:N ratio shared a similar distribution pattern with land use and had higher values in forest areas. This study provides useful indicators for a more effective modeling of soil properties on various scales based on satellite imagery.

17346. 题目: Methylmercury formation in boreal wetlands in relation to chemical speciation of mercury(II) and concentration of low molecular mass thiols
文章编号: N20101413
期刊: Science of the Total Environment
作者: Van Liem-Nguyen, Ulf Skyllberg, Erik Björn
更新时间: 2020-10-14
摘要:

Methylmercury (MeHg) is a neurotoxin formed from inorganic divalent mercury (HgII) via microbial methylation, and boreal wetlands have been identified as major sources of MeHg. There is however a lack of studies investigating the relationship between the chemical speciation of HgII and MeHg formation in such environments, in particular regarding to role of thiol compounds. We determined HgII methylation potentials, kmeth, in boreal wetland soils using two HgII isotope tracers: 198Hg(OH)2(aq) and HgII bonded to thiol groups in natural organic matter, 200HgII–NOM(ads), representing HgII sources with high and low availability for methylation. The 198Hg(OH)2(aq) tracer was consistently methylated to a 5-fold higher extent than 200HgII–NOM(ads), independent of environmental conditions. This suggests that the concentration of HgII in porewater was a decisive factor for HgII methylation. A comprehensive thermodynamic speciation model (including HgII complexes with inorganic sulfide (H2S), polysulfides (H2Sn), thiols associated with natural organic matter (NOM–RSH) and specific low molecular mass thiols (LMM–RSH) provided new insights on the speciation of HgII in boreal wetland porewaters, but did not demonstrate any clear relationship between kmeth and the calculated chemical speciation. In contrast, significant positive relationships were observed between kmeth and the sum of LMM thiol compounds of biological origin. We suggest two possible mechanisms underlying these correlations: 1) LMM thiols kinetically control the size and composition of the HgII pool available for microbial uptake, and/or 2) LMM thiols are produced by microbes such that the correlation reflects a relation between microbial activity and MeHg formation.

17347. 题目: Membrane fouling control by UV/persulfate in tertiary wastewater treatment with ultrafiltration: A comparison with UV/hydroperoxide and role of free radicals
文章编号: N20101412
期刊: Separation and Purification Technology
作者: Fangshu Qu, Zhimeng Yang, Xiaolian Li, Huarong Yu, Zhihui Pan, Gongduan Fan, Junguo He, Hongwei Rong
更新时间: 2020-10-14
摘要:

The membrane fouling caused by effluent organic matter (EfOM) is a bottleneck for application of ultrafiltration (UF) in tertiary wastewater treatment. In this study, two ultraviolet-based oxidation pretreatments, i.e., ultraviolet/persulfate (UV/PS) and ultraviolet/hydrogen peroxide (UV/H2O2), were used to alleviate EfOM fouling at a low UV dose of 2.36×103 mJ cm-2, in consideration of the widely use of UV radiation for disinfection in wastewater treatment plants. Effects of the pretreatments on characteristics of EfOM were investigated in terms of fluorescence spectrum, molecular weight distribution, and hydrophobicity. Moreover, filtration tests were performed to assess impacts of the oxidation pretreatments on flux decline, fouling reversibility, and fouling mechanisms. The results showed that the UV/PS pretreatment substantially reduced flux decline and improved fouling reversibility during filtration of the secondary effluent, attributed to efficient degradation (∼67%, in terms of UV254) and partial mineralization (∼39%, in terms of DOC) of EfOM. In particular, the irreversible resistance was decreased by nearly one order of magnitude at the PS dose of 1.0 mM. UV/H2O2 was not effective in EfOM fouling control under the conditions investigated. The UV/PS pretreatment resulted in a shift of mechanisms for EfOM fouling from successive pore blocking and cake filtration to single standard blocking, attributing to preferential degradation of macromolecular components in EfOM and a weakened role of cake interception. The radical quenching experiment showed that the sulfate radicals played a dominant role in EfOM fouling control by UV/PS, and that transformation of sulfate radicals into hydroxyl radicals negatively affected EfOM fouling control.

17348. 题目: Spatial and temporal variability of trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, Pb), iron and copper speciation, and electroactive Fe-binding humic substances in surface waters of the eastern Gulf of Mexico
文章编号: N20101411
期刊: Marine Chemistry
作者: Travis Mellett, Kristen N. Buck
更新时间: 2020-10-14
摘要:

The concentrations of bioactive trace metals (Fe, Cu, Mn, Zn, Co, Ni, Cd, and Pb), Fe-and Cu-binding organic ligands, and electroactive Fe-binding humic substances were measured in surface waters across the West Florida Shelf in the eastern Gulf of Mexico in June 2015 and in February-March 2018. Seasonal differences in dust deposition were associated with increased concentrations of Fe, Mn and Pb in offshore surface waters in June 2015 compared to Feb-Mar 2018. Total concentrations of Fe-binding ligands offshore were similar between seasons, and this ambient ligand pool acted to stabilize a portion of Fe delivered via dust deposition within the dissolved fraction. Apparent photoreduction of Cu-binding organic ligands in offshore summer surface waters led to bioavailable Cu2+ concentrations that could potentially inhibit the growth of some cyanobacteria species. The concentrations of Fe-binding humic-like ligands were better correlated with Cu-binding ligands than Fe-binding ligands, suggesting that terrestrially derived photoactive ligands may have a significant influence on the cycling of Cu-binding ligands across the West Florida Shelf. Intrusion of the Loop Current into the study region was observed in June 2015 and appeared to entrain bands of low salinity water from the northern Gulf of Mexico. This process brought elevated trace metals and Fe-binding humic-like ligands to the outer West Florida Shelf, which may then be delivered to the North Atlantic via the Loop Current-Florida Current-Gulf Stream system.

17349. 题目: The influence of native soil organic matter and minerals on ferrous iron oxidation
文章编号: N20101410
期刊: Geochimica et Cosmochimica Acta
作者: Chunmei Chen, Aaron Thompson
更新时间: 2020-10-14
摘要:

Fe(II) oxidation by O2 is an important process generating Fe (oxyhydr)oxides, which play sorptive, structural and electron-transfer roles in soils. Here we explored how native minerals and organic matter (OM) affect the rate of Fe(II) oxidation and resulting de novo Fe(III) minerals in soil slurries. A topsoil was collected from Luquillo tropical forest, and a topsoil and subsoil were collected from Calhoun cultivated site. We oxidized 57Fe(II) in these soils either untreated or with OM and/or Fe (oxyhydr)oxides removed. We measured Fe oxidation kinetics by tracking the loss of Fe(II) and characterized the de novo Fe(III) solids using 57Fe Mossbauer spectroscopy. We find that OM retarded Fe(II) oxidation, while pre-existing Fe (oxyhydr)oxides played a significant role in catalyzing Fe(II) oxidation. The non-extractable (residual) soil minerals (i.e.phyllosilicates and quartz) after removing Fe (oxyhydr)oxides, had a minor effect on oxidation rates. In the topsoils, OM resulted in a lower-crystallinity Fe(III) minerals, including nanogoethite and highly-disordered Fe phases, relative to OM-removal treatment. Goethite with varying crystallinity was promoted by the pre-existing Fe (oxyhydr)oxides in all soils, in contrast to homogenous oxidation where lepidocrocite was formed. Compared to the topsoils, Fe(II) oxidation resulted in large-particle goethite with the highest crystallinity in the Calhoun subsoil that was more enriched in native crystalline Fe-(oxyhydr)oxides and more depleted in OM. Crystalline hematite, was also formed in the Calhoun subsoil, most likely due to a templating effect of pre-existing hematite. These findings suggest that the nature of de novo formed Fe minerals in soils and sediments may depend strongly on resident existing soil OM and Fe phases. This study extends from previous synthetic systems to complex soils and thus constitutes a significant step forward in understanding Fe transformation in natural environments.

17350. 题目: Organic Sulfones In The Brine Of Lake Vida (East Antarctica)
文章编号: N20101409
期刊: Geochimica et Cosmochimica Acta
作者: Luoth Chou, Alison E. Murray, Fabien Kenig
更新时间: 2020-10-14
摘要:

Located in a closed basin in the McMurdo Dry Valleys, East Antarctica, Lake Vida brine is a cold (-13°C), hypersaline, interstitial, anoxic, and aphotic ecosystem trapped within 27+ m of ice. This brine is not in contact with the atmosphere, and currently hosts a slow-growing, cold-limited bacteria-dominated ecosystem that have persisted for at least ∼2800 years. Analysis of the dichloromethane extractable fraction of dissolved organic matter of Lake Vida brine revealed the presence of seven novel organic sulfones, tentatively identified on the basis of mass spectral fragmentation, as well as eight sulfones that have been structurally described in previous chemistry studies. A total of fifteen organic sulfones, and others that have yet to be identified, were observed in Lake Vida brine, most of which have never been previously detected in any other natural ecosystems. Results suggest that these compounds may be derived from a lake system in which a dissolved organic carbon pool may have been oxidized in lake waters in contact with the atmosphere. Alternative hypotheses on the origin of these sulfones, involving potential abiotic alterations of dissolved organic sulfur as a consequence of long-term brine-rock reactions that generated reactive oxygen species, are also considered. Understanding the origin and formation mechanisms of these organic sulfones may reveal an important pathway that influence the dissolved organic sulfur constituent, not only of Antarctic aquatic systems, but also potentially the global marine environment, as well as extraterrestrial hypersaline, subzero habitats.

17351. 题目: Coexistence of polyethylene microplastics and biochar increases ammonium sorption in an aqueous solution
文章编号: N20101408
期刊: Journal of Hazardous Materials
作者: Xiaona Li, Xin Jiang, Yang Song, Scott X. Chang
更新时间: 2020-10-14
摘要:

Biochar is used to remove ammonium (NH4+) from wastewater, where microplastics are emerging pollutants. However, whether microplastics can adsorb NH4+ or how they will affect the sorption of NH4+ by biochars have not been studied. Here, batch sorption kinetics and isotherm experiments were conducted to elucidate the sorption of NH4+ on a manure biochar (MBC), a straw biochar (SBC), a wood sawdust biochar (WBC), a polyethylene microplastic (PE), and their combination. The results showed that PE had a smaller sorption capacity (Qmax = 3.29 mg g−1) but a faster adsorption rate (ks = 0.08 g (mg min)−1) for NH4+ than biochars (Qmax = 5.67 ~ 20.54 mg g−1; ks = 0.02 ~ 0.04 g (mg min)−1). When PE and biochars coexisted in an aqueous solution, the NH4+ sorption capacity was increased by 17.0% in PE+SBC, 7.1% in PE+MBC, and 8.6% in PE+WBC, which likely due to the deprotonation of functional groups and the decreases in small molecular-size dissolved organic carbon. We conclude that microplastics can adsorb NH4+; moreover, they can enhance the NH4+ sorption capacity of biochars. Therefore, when biochar is used for NH4+ removal from wastewater, the interaction of biochar and microplastics needs to be considered.

17352. 题目: Characterisation and Performance of three Kenaf coagulation products under different operating conditions
文章编号: N20101407
期刊: Water Research
作者: Benjamin U. Okoro, Soroosh Sharifi, Mike Jesson, John Bridgeman, Rodrigo Moruzzi
更新时间: 2020-10-14
摘要:

The Sustainable Development Goal (SDG) 6.1, established by the United Nations General Assembly in 2015, targets universal and equitable access to safe and affordable drinking water for all by 2030. An essential factor in achieving this goal is the harnessing of green coagulants – naturally occurring, environmentally friendly materials which are effective coagulants for use in water treatment, with good availability in developing countries, inherent renewable properties and ease of biodegradation. In order to gain from these benefits, it is essential to fully understand how such coagulants may best be utilised, particularly concerning their practical application in developing countries. In this study, three different plant-based coagulation products (PCPs), namely Hexane (HxKP), saline (StKP) and crude (CrKP) extracts of Kenaf plant seed (Hibiscus cannabinus, a species of the Hibiscus plant), were applied to high (HTW), medium (MTW) and low (LTW) turbidity water in order to determine their performance and coagulation ability. The ability of the three Kenaf coagulant products (KCPs) to remove hydrophobic fractions of natural organic matter (NOM) was measured. The impact of KCPs on the treated water organic matter content (a known disinfection by-product (DBP) precursor) was examined using known surrogates of natural organic matter (NOM) i.e. the dissolved organic carbon (DOC), ultraviolet absorbance at 254 (UV254) and specific ultraviolet absorbance (SUVA254). Results obtained quantify the implications of using these coagulants during the water disinfection process. A parametric study, measuring the effect of different operating parameters, such as untreated water turbidity, pH, dosages, retention time, and KCP storage time, was completed. Turbidity removal performance for HxKP and StKP was very good with > 90% removal recorded for HTW and MTW, respectively, at pH seven within 2 hours retention time. Images obtained from scanning electron microscopy (SEM) analysis revealed a high likelihood of the coagulation mechanism of KCPs to be adsorption-interparticle bridging brought about by their flake-like structures and surfaces charges. Varying pH had no measurable influence on the coagulation performance of the KCPs. Comparing their efficiency with Moringa Oleifera (MO, a previously researched PCP) and alum showed that HxKP had a negligibly different particle removal as MO. StKP turbidity removal performance was below HxKP by 1% for HTW and LTW and 2% for MTW but performed higher than the CrKP by 5% and 7% in HTW and MTW, respectively. The optimum dosage of HxKP and StKP reduced DBP surrogate values, indicating that its precursor is also minimized, although a slight shift from this optimum dosage showed a significant rise in their concentration thus signifying a potential increase in DBPs during disinfection.

17353. 题目: Aggregation kinetics of fragmental PET nanoplastics in aqueous environment: Complex roles of electrolytes, pH and humic acid
文章编号: N20101406
期刊: Environmental Pollution
作者: Shunan Dong, Wangwei Cai, Jihong Xia, Liting Sheng, Weimu Wang, Hui Liu
更新时间: 2020-10-14
摘要:

The aggregation kinetics of fragmental polyethylene glycol terephthalate (PET) nanoplastics under various chemistry conditions in aqueous environment were firstly investigated in this work. The aggregation of PET nanoplastics increased with increasing electrolyte concentrations and decreasing solution pH, which became stronger with the presence of divalent cations (e.g. Ca2+ and Mg2+) than that of monovalent cations (e.g. Na+ and K+). The effect of cations with the same valence on the aggregation of PET nanoplastics was similar. The measured critical coagulation concentrations (CCC) for PET nanoplastics at pH 6 were 55.0 mM KCl, 54.2 mM NaCl, 2.1 mM CaCl2 and 2.0 mM MgCl2, which increased to 110.4 mM NaCl and 5.6 mM CaCl2 at pH 10. In addition, the aggregation of PET nanoplastics was significantly inhibited with the presence of humic acid (HA), and the CCC values increased to 558.8 mM NaCl and 12.3 mM CaCl2 (1 mg L-1 HA). Results from this study showed that the fragmental PET nanoplastics had the quite higher CCC values and stability in aqueous environment. In addition, the aggregation behaviors of PET nanoplastics can be successfully predicted by the Derjguin Landau Verwey Overbeek (DLVO) theory.

17354. 题目: Assessing the priming effect of dissolved organic matter from typical sources using fluorescence EEMs-PARAFAC
文章编号: N20101405
期刊: Chemosphere
作者: Wan-E Zhuang, Wei Chen, Qiong Cheng, Liyang Yang
更新时间: 2020-10-14
摘要:

Priming effect (PE) is increasingly recognized as an important mechanism in the microbial degradation of dissolved organic matter (DOM) from freshwater to the ocean. However, potential PE during the mixing of DOM from different sources and the effects on different DOM constituents are still largely unknown. This study examined the PE after adding DOM from typical natural and anthropogenic sources (rainwater, fresh plant, leaf litter, and wastewater) into pre-aged river DOM, using dissolved organic carbon (DOC) measurement, absorption spectroscopy, and fluorescence excitation-emission matrices-parallel factor analysis (EEMs-PARAFAC). The plant-derived DOM had a low humic content and was dominated by benzoic acid-like and tyrosine-like fluorescent components (C4 and C5), which showed a high DOC bioavailability of 80%. DOC in rainwater and wastewater also had high bioavailabilities (45%–50%), while DOM in the leaf litter leachate showed high aromaticity, average molecular weight, and humic content but low DOC bioavailability (12%). There was generally limited PE (<5% of the initial values) on the degradation of DOC and chromophoric DOM (CDOM) for most samples. Two humic-like components (C2 and C3) showed little PE, while the humic-like C1 and C6, tyrosine-like C5, and tryptophan-like C7 showed variable PE after adding rainwater, wastewater, and plant leachate. Overall, the results revealed that the DOM from typical natural and anthropogenic sources had different composition and bioavailability, and their inputs to aquatic environments would result in variable PE on the bulk DOC and different DOM components.

17355. 题目: Application of macroalgal biomass derived biochar and bioelectrochemical system with Shewanella for the adsorptive removal and biodegradation of toxic azo dye
文章编号: N20101404
期刊: Chemosphere
作者: Ranjit Gurav, Shashi Kant Bhatia, Tae-Rim Choi, Yong-Keun Choi, Hyun Joong Kim, Hun-Suk Song, Sun Mi Lee, Sol Lee Park, Hye Soo Lee, Joonseok Koh, Jong-Min Jeon, Jeong-Jun Yoon, Yung-Hun Yang
更新时间: 2020-10-14
摘要:

The present study aimed towards adsorptive removal of the toxic azo dye onto biochar derived from Eucheuma spinosum biomass. Characterization of the produced biochar was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET). Eucheuma spinosum biochar (ES-BC) produced at 600 °C revealed a maximum adsorption capacity of 331.97 mg/g towards reactive red 120 dye. The adsorption data fitted best to the pseudo-second order kinetics (R2 > 0.99) and Langmuir isotherm (R2 > 0.98) models. These adsorption models signified the chemisorption mechanism with monolayer coverage of the adsorbent surface with dye molecules. Furthermore, the adsorption process was mainly governed by electrostatic interaction, ion exchange, metal complexation, and hydrogen bonding as supported by the solution pH, FTIR, XPS, and XRD investigation. Nevertheless, alone adsorption technology could not offer a complete solution for eliminating the noxious dyes. Therefore, the bioelectrochemical system (BES) equipped with previously isolated marine Shewanella marisflavi BBL25 was intended for the complete remediation of azo dye. The BES II demonstrated highest dye decolorization (97.06%) within 48 h at biocathode where the reductive cleavage of the azo bond occurred. Cyclic voltammetry (CV) studies of the BES revealed perfect redox reactions taking place where the redox mediators shuttled the electrons to the dye molecule to accelerate the dye decolorization. Besides, the GC-MS analysis revealed biotransformation of the dye into less toxic metabolites as tested using a phyto and cytogenotoxicity.

17356. 题目: Long-term soil organic carbon dynamics in temperate cropland-grassland systems
文章编号: N20101403
期刊: Agriculture, Ecosystems and Environment
作者: Thomas Guillaume, Luca Bragazza, Clément Levasseur, Zamir Libohova, Sokrat Sinaj
更新时间: 2020-10-14
摘要:

Increasing soil organic carbon (SOC) in agroecosystems enables to address simultaneously multiple goals such as climate change adaptation and mitigation as well as food security. As croplands are depleted in SOC, they offer a great potential to sequester atmospheric carbon (C). Nonetheless, croplands are still losing SOC under most of the current agricultural systems. Although many factors driving SOC dynamics have already been identified, their relative importance has not been quantified yet. Using one of the densest European soil monitoring networks with 250 sites established in western Switzerland, in the present study we (i) assessed long-term (over 30 years) SOC dynamics in croplands (CR), permanent grasslands (PG) and mountain pastures (MP), and (ii) prioritized the importance of land use, soil characteristics and sites conditions in driving SOC dynamics. The SOC levels in PG and MP were similar when clay content was accounted for, whereas CR were depleted in SOC by 3.9 mg C mg−1 clay as compared to PG. The majority (61 %) of CR had SOC:clay ratio below 1:10, but only 16 % of PG and MP sites reached this threshold. By contrast, soil organic matter stoichiometry (C:N:Porg ratios) was similar in CR and PG for comparable SOC content. The increase of C:Porg ratio with SOC content (dilution effect) and the high total P in CR and PG (legacy effect) indicate the possibility to sequester atmospheric C at reduced nutrient sequestration costs. SOC changes ranged from -0.61 to 1.32 mg g-1 soil yr−1 and were the highest in sites that experienced land-use changes. No PG were losing SOC, while CR sites exhibited both SOC gains and losses. Because of the predominance of the initial SOC content on SOC dynamics, land-use history must be accounted for when assessing the effect of management practices. The main manageable factors driving SOC dynamics were the time under temporary or permanent grasslands along with the soil total P. As PG already are rich in SOC and total P, organic amendments should be partly redirected to CR.

17357. 题目: Differences in the quantity and quality of organic matter exported from Greenlandic glacial and deglaciated watersheds
文章编号: N20101402
期刊: Global Biogeochemical Cycles
作者: Andrea J. Pain, Jonathan B. Martin, Ellen E. Martin, Shaily Rahman, Philip Ackermann
更新时间: 2020-10-14
摘要:

Riverine input of terrestrial dissolved organic matter (DOM) is an important component of the marine carbon cycle and drives net carbon dioxide production in coastal zones. DOM exports to the Arctic Ocean are likely to increase due to melting of permafrost and the Greenland Ice Sheet (GrIS), but the quantity and quality of DOM exports from deglaciated watersheds in Greenland, as well as expected changes with future melting, are unknown. We compare DOM quantity and quality in Greenland over the melt seasons of 2017‐2018 between two rivers directly draining the GrIS (meltwater rivers) and four streams draining deglaciated catchments that are disconnected from the ice (non‐glacial streams). We couple these data with discharge records to compare dissolved organic carbon (DOC) exports. DOM sources and quality differ significantly between watershed types: fluorescence characteristics and organic molar C:N ratios suggest that DOM from deglaciated watersheds is derived from terrestrial vegetation and soil organic matter, while that in glacial watersheds contains greater proportions of algal and/or freshly produced biomass and may be more reactive. DOC specific yield is similar for non‐glacial streams (0.1‐1.2 Mg/km2/yr) compared to a glacial meltwater river (0.2‐1.1 Mg/km2/yr), despite orders of magnitude differences in instantaneous discharge. Upscaling based on land cover leads to an estimate of total DOC contributions from Greenland between 0.2‐0.5 Tg/year, much of which is derived from deglaciated watersheds. These results suggest that future warming and ice retreat may increase DOC fluxes from Greenland with consequences for the Arctic carbon cycle.

17358. 题目: Annual net community production of particulate and dissolved organic carbon from a decade of biogeochemical profiling float observations in the Northeast Pacific
文章编号: N20101401
期刊: Global Biogeochemical Cycles
作者: W. Z. Haskell, A. J. Fassbender, J. S. Long, J. N. Plant
更新时间: 2020-10-14
摘要:

Carbon export out of the surface ocean via the biological pump is a critical sink for atmospheric carbon dioxide. This process transports organic carbon to the deep ocean through sinking particulate organic carbon (POC) and the downward transport of suspended POC and dissolved organic carbon (DOC). Changes in the relative contribution of each pathway can significantly affect the magnitude and efficiency of carbon export to depth. Net community production (NCP), an analog of carbon export under steady state assumptions, is typically estimated using budgets of biologically important chemical tracers in the upper ocean constrained by ship‐board or autonomous platform observations. In this study, we use measurements from biogeochemical profiling floats, the Ocean Station Papa mooring, and recently‐developed algorithms for carbonate system parameters to constrain budgets for three tracers (nitrate, dissolved inorganic carbon, and total alkalinity) and estimate NCP in the Northeast Pacific from 2009‐2017. Using our multiple‐tracer approach, and constraining end‐member nutrient ratios of the POC and DOC produced, we not only calculate regional NCP throughout the annual cycle and across multiple depth horizons, but also partition this quantity into particulate and dissolved portions. We also use a particle backscatter‐based approach to estimate POC attenuation with depth and present a new method to constrain particle export across deeper horizons and estimate in situ export efficiency. Our results agree well with previously published estimates of regional carbon export annually and suggest that the approaches presented here could be used to assess the magnitude and efficiency of carbon export in other regions of the world's oceans.

17359. 题目: The cotreatment of old landfill leachate and domestic sewage in rural areas by deep Subsurface Wastewater Infiltration System (SWIS): Performance and Bacterial community
文章编号: N20101304
期刊: Environmental Pollution
作者: Fengming Chen, Guowen Li, Xiaoguang Li, Hongqiang Wang, Huabin Wu, Jiaxi Li, Caole Li, Wei Li, Lieyu Zhang, Beidou Xi
更新时间: 2020-10-13
摘要:

In this work, two deep subsurface wastewater infiltration systems (SWISs) were constructed and fed with domestic sewage (control system, S1) and mixed wastewater consisting of old landfill leachate and domestic sewage (experimental system, S2). S1 and S2 exhibited favorable removal efficiencies, with TP (98.8%, 98.7%), COD (87.6%, 86.9%), NH4+-N (99.8%, 99.9%) and TN (99.2%, 98.9%). Even when increasing the pollutant load in S2 by adding old landfill leachate, the almost complete removal performance could be maintained in terms of low effluent concentrations and even increased in terms of load removal capabilities, which included COD (19.4, 25.9 g·m-2·d-1), NH4+-N (8.2, 19.9 g·m-2·d-1), TN (8.9, 20.6 g·m-2·d-1). To investigate the transformation of dissolved organic matter along depth, Three-Dimensional Excitation Emission Matrix fluorescence spectroscopy combined with Fluorescence Regional Integration analysis was applied. The results showed that PI,n and PII,n (the proportions of biodegradable fractions) increased gradually from 6.59% and 21.8% at S2_20 to 10.8% and 27.7% at S2_110, but PIII,n and PV,n (the proportions of refractory organics) declined from 23.1% and 27.8% at S2_20 to 21.1% and 16.4% at S2_110, respectively. In addition, high-throughput sequencing technology was employed to observe the bacterial community at different depths, and the predicted functional potential of the bacterial community was analyzed by PICRUSt. The results showed that the genera Flavobacterium, Pseudomonas, Vogesella, Acinetobacter and Aquabacterium might be responsible for refractory organic degradation and that their products might serve as the carbon source for denitrifiers to achieve simultaneous nitrate and refractory organic removal. PICRUSt further demonstrated that there was a mutual response between refractory organic degradation and denitrification. Overall, the combined treatment of domestic sewage and old leachate in rural areas by SWIS is a promising approach to achieve comprehensive treatment.

17360. 题目: Light exposure interferes with electroactive biofilm enrichment and reduces extracellular electron transfer efficiency
文章编号: N20101303
期刊: Water Research
作者: Mingrui Sui, Yi Li, Yiying Jiang, Yuhang Zhang, Longfei Wang, Wenlong Zhang, Xin Wang
更新时间: 2020-10-13
摘要:

Light plays a vital role in shaping the structure of natural biofilms, but the effect of light on electroactive biofilm (EAB) has not been systematically studied. Herein, the influence of light on the formation of EAB was investigated. The EAB grown in darkness was more electroactive (EAB-0) with a peak current of ∼4.5 A/m2, which was 196 and 5556 times higher than EABs formed under light intensities of 600 (EAB-600) and 1200 lux (EAB-1200). A thin EAB (30 μm) with spherical pink aggregates was obtained after 13 days in the darkness, comparing to a dense and flat biofilm when exposed to light. Although the biomass in EAB-1200 (38.5 ± 1.6 mg/L) was 3 times larger than that in EAB-0 (11.4 ± 1.8 mg/L), the degradation of substrate was not sufficient. EAB-0 contained 85% Geobacter species, while the Rhodopseudomonas species made up 66% and 75% of EAB-600 and EAB-1200, respectively. EABs exposed to light produced more extracellular polysaccharides, which resulted in a low electron transfer capacity of the extracellular polymeric substances (EPS). Our findings confirmed that the light exposure limited the electroactivity of EAB by altering the microbial components as well as biofilm morphology, which can be used in predictions of the formation and properties of engineered EAB in outdoor environments.

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