81. 题目: DNA pyrimidine bases in water: Insights into relative reactivity, byproducts formation and combined toxicity during chlorination
期刊: Science of The Total Environment
作者: Shisheng Zhang, Tao Lin, Han Chen, Wei Chen, Hang Xu, Hui Tao
摘要: Soluble microbial products (SMPs), as precursors of disinfection byproducts (DBPs) in water treatment, are composed of polysaccharides, humic acid, proteins and DNA, and have caused widespread concerned. Pyrimidine bases (cytosine and thymine) are significant nitrogenous constituents of DNA, which could pose an adverse impact on water quality during chlorination. This study focused on the correlation between relative reactivity, formation of DBPs and combined toxicity in the chlorination of a binary pyrimidine base mixture. The relative reactivities of cytosine and thymine were quite different at a low disinfectant concentration; cytosine reacted more actively with chlorine than thymine did, at the chlorine/total pyrimidine bases molar ratio = 10. The chlorination of binary pyrimidine bases can produce both carbonous DBPs (C-DBPs) and nitrogenous DBPs (N-DBPs). In particular, the total yields of trichloromethane (TCM) and trichloronitromethane (TCNM) were lower than the additive yields of monadic cytosine and monadic thymine (“monadic” refers to “separate”), whereas the total yields of haloacetic acids (HAAs) and haloacetonitriles (HANs) were promoted evidently. High reactivity of cytosine with chlorine, greater potential of cytosine to produce specific DBPs and the alkylation of transformation products of thymine may synthetically account for the diversity in total DBPs yields, especially the increased formation of HAAs and HANs. In our toxicity trial, even though the antagonistic effect predominated at fa > 0.4 (fa refers to the affected fraction), the synergism at low concentration levels could enhance the combined toxicity by promoting the yields of N-DBPs.
82. 题目: Differential responses of soil hydrolytic and oxidative enzyme activities to the natural forest conversion
期刊: Science of The Total Environment
作者: Gang Xu, Zhijian Long, Peng Ren, Chengjie Ren, Ying Cao, Yan Huang, Shanglian Hu
摘要: Effects of natural forest conversion (NFC) on soil nutrient turnover are substantially mediated by soil microbial extracellular hydrolytic enzymatic activities (Hy-EEAs) and oxidative enzymatic activities (Ox-EEAs). Yet it remains largely unknown the indicative links between soil Hy- and Ox-EEAs and soil carbon (C), nitrogen (N) and phosphorus (P) supplies based on economic theories of microbial metabolism under NFC. Here we used a meta-analysis approach to synthesize the responses of the soil C-, N-, P-degrading Hy-EEAs and Ox-EEAs, soil microbial biomass, soil organic C, total N, P and available P parameters to natural forest conversion from 51 peer-reviewed studies. Our results showed that NFC notably decreased soil Hy-EEAs but statistically insignificant reduction of soil Ox-EEAs. The changes of soil Hy- and Ox-EEAs were significantly and positively associated with soil organic C, available P as well as microbial biomass C and N but significantly and negatively correlated with soil pH, whereas the changes of soil C/N impacted on soil Ox-EEAs remarkably but not for soil Hy-EEAs. The depletion of soil organic carbon stimulated soil microbial secretion of Hy- and Ox-EEAs. The soil total N scarcity only provoked soil microbial Hy-EEAs rather than Ox-EEAs. The soil total P dearth quickened the soil Ox-EEAs, however, the plenitude of soil available P suppressed soil Hy- and Ox-EEAs. Moreover, the eco-enzymatic stoichiometry of soil Hy-EEAs indicated that soil N and P nutrient limitation after NFC restricted soil microbial N- and P-acquiring enzymes secretion, which ultimately reduced resources availability for C acquisition. Altogether, the distinct responses of soil Hy- and Ox-EEAs depended on substrate availability peculiarly for soil N and P gains of microorganisms for further enzymatic ability on soil C decomposition and highlighted the abundant or absent supply of soil N and P for positive or negative enzymatic activities on metabolic requirement of soil edaphons.
83. 题目: Biochar sorption of PFOS, PFOA, PFHxS and PFHxA in two soils with contrasting texture
作者: Matthew Askeland, Bradley O. Clarke, Sardar Alam Cheema, Ana Mendez, Gabriel Gasco, Jorge Paz-Ferreiro
摘要: The ability to immobilise PFAS in soil may be an essential interim tool while technologies are developed for effective long-term treatment of PFAS contaminated soils. Serial sorption experiments were undertaken using a pine derived biochar produced at 750 °C (P750). All experiments were carried out either in individual mode (solution with one PFAS at 5 μg/L) or mix mode (solution with 5 μg/L of each: PFOS, PFOA, PFHxS and PFHxA), and carried out in 2:1 water to soil solutions. Soils had biochar added in the range 0–5% w/w. Kinetic data were fitted to the pseudo-second order model for both amended soils, with equilibrium times ranging 0.5–96 h for all congeners. PFOS sorption was 11.1 ± 4.5% in the loamy sand compared to 69.8 ± 4.9% in the sandy clay loam. While total sorption was higher in the unamended loamy sand than sandy clay loam for PFHxA, PFOA and PFOS, the effect of biochar amendment for each compound was found to be significantly higher in amended sandy clay loam than in amended loamy sand. Application of biochar reduced the desorbed PFAS fraction of all soils. Soil type and experimental mode played a significant role in influencing desorption. Overall, the relationship between sorbent and congener was demonstrated to be highly impacted by soil type, however the unique physiochemical properties of each PFAS congener greatly influenced its unique equilibrium, sorption and desorption behaviour for each amended soil and mode tested.
84. 题目: Redox reactions between chromium(VI) and hydroquinone: Alternative pathways for polymerization of organic molecules
期刊: Environmental Pollution
作者: Yu-Min Tzou, Kai-Yue Chen, Ching-Yun Cheng, Way-Zen Lee, Heng Yi Teah, Yu-Ting Liu
摘要: Chromium (VI) reduction by organic compounds is one of the major pathways to alleviate the toxicity and mobility of Cr(VI) in the environment. However, oxidative products of organic molecules receive less scientific concerns. In this study, hydroquinone (H2Q) was used as a representative organic compound to determine the redox reactions with Cr(VI) and the concomitant oxidative products. Spectroscopic analyses showed that Cr(III) hydroxides dominated the precipitates produced during redox reactions of Cr(VI) and H2Q. For the separated filtrates, the acidification induced the oxidative polymerization of organic molecules, accompanied with the complexation with Cr(III). The aromatic domains dominated the chemical structures of the black and fluffy organic polymers, which was different to the natural humic acids due to the shortage of aliphatic chains. Results of linear combination fitting (LCF) for Cr K-edge X-ray absorption near edge structure (XANES) spectra demonstrated that up to 90.4% of Cr inventory in precipitates derived after the acidification of filtrates was Cr(III) complexed with humic-like polymers, suggesting that Cr(III) possibly acted as a linkage among organic molecules during the polymerization processes of H2Q. This study demonstrated that Cr(VI) may lead to the polymerization of organic molecules in an acidic solution, and thus, it could raise scientific awareness that the oxidative decomposition of organic molecules may not be the only pathway while interacting with the strong oxidant of Cr(VI).
85. 题目: Chemical-free cleaning of fouled reverse osmosis (RO) membranes derived from bis(triethoxysilyl)ethane (BTESE)
期刊: Journal of Membrane Science
作者: Suhaina M. Ibrahim, Hiroki Nagasawa, Masakoto Kanezashi, Toshinori Tsuru
摘要: The aim of this work was to study the fouling and cleaning behavior of bis(triethoxysilyl)ethane (BTESE)-derived organosilica membranes, which is a new class of RO membranes that feature chlorine tolerance and thermal stability. The foulants used in this study included bovine serum albumin (BSA) and sodium alginate (SA), which are typical examples of effluent organic matter (EOM). Sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB) surfactants served as typical industrial waste. With the EOM foulants, BSA fouling occurred at a pH that approximated its iso-electric point (IEP), and the fouling became more severe with the addition of electrolytes into the SA solution. In both cases, however, the fouled BTESE membrane was recovered with the use of deionized water (DIW). The fouling was more pronounced in the presence of DTAB by comparison with SDS surfactants. Surprisingly, in all tests, within 30 min and without the need of chemical agents, the integrity of the fouled BTESE membranes was recovered by applying water at a temperature of at least 80 °C.
86. 题目: Combined ditch buried straw return technology in a ridge–furrow plastic film mulch system: Implications for crop yield and soil organic matter dynamics
期刊: Soil and Tillage Research
作者: Yüze Li, Duanpu Song, Pengfei Dang, Lina Wei, Xiaoliang Qin, Kadambot H.M. Siddique
摘要: A ridge–furrow plastic film mulch (RP) configuration can increase crop and straw yields in semiarid areas of China. This study advocated for a novel soil tillage practice (ditch buried straw return) in a ridge–furrow plastic film mulch system. There were three treatments: (i) flat cultivation, CK; (ii) ridge–furrow plastic film mulch with no straw return (RP−S); and (iii) ridge–furrow plastic film mulch with ditch buried straw return (RP+S). Field experiments were conducted from 2015 to 2018 on the Loess Plateau of China to study the effects of straw incorporation on maize growth, biomass, water use efficiency, soil organic carbon, and total nitrogen sequestration capacity in RP systems. The mean rate of straw decomposition in RP+S reached 81 % at harvest of each year. The RP systems provided suitable hydrothermal conditions for maize growth. Both RP treatments promoted maize growth, particularly biomass accumulation and plant height under RP+S. The RP+S treatment also had greater concentrations of soil organic carbon and total nitrogen in surface soil at harvest, higher total nitrogen accumulation, nitrogen content and crude protein in maize grain, and higher maize yields and water use efficiencies than the other two treatments. In summary, the introduction of ditch buried straw return to RP is an effective measure for promoting the sustainable development of film mulching systems in semiarid regions of China by improving soil fertility and increasing crop yields.
87. 题目: Characterization and biogas production potentials of aqueous phase produced from hydrothermal carbonization of biomass – Major components and their binary mixtures
期刊: Chemical Engineering Journal
作者: Muhammad Usman, Shuang Ren, Mengyuan Ji, Sompong O-Thong, Yichao Qian, Gang Luo, Shicheng Zhang
摘要: Hydrothermal carbonization aqueous phase (HTC-AP) can be used for methane production by anaerobic digestion (AD). However, it generally had low conversion efficiency due to the formation of complex dissolved organic matters, which depends upon the components of biomass. The present study investigated the characteristics, methane potentials, and recalcitrant chemicals of HTC-AP produced from different combinations of model compounds carbohydrate (α-cellulose, C) and protein (bovine serum albumin, BSA) with mass ratios of 1:0, 0.75:0.25, 0.5:0.5, 0.75:0.25 and 0:1. The methane yields of samples 1:0 (pure C) and 0:1 (pure BSA) were 192 mL/g COD and 187 mL/g COD, respectively, while it was decreased to 105.5 CH4 mL/g COD for sample 0.75:0.25 (C/BSA), indicating more recalcitrant organics were produced with the combination of C and BSA. It was found that the mean MW (209157) of sample 0.75:0.25 was much higher than the other samples (<7000 Da). While the highest percentage (51%) of hard bio-degradable hydrophobic DOC, humics, and building blocks organics were also observed in this sample by LC-OCD-OND analysis. Furthermore, a high value of SUVA index 2.56 was noted, indicating the presence of a large number of aromatic compounds. In addition, fluorescent compounds mainly relating to humic-like substances were also detected by 3D-EEM. GC–MS analysis showed higher concentrations of pyrazine and its derivatives were present in sample 0.75:0.25, which indicated the occurrence of a serious Maillard reaction. The continuous experiment further verified the lower biodegradability of sample 0.75:0.25 with a methane yield of 108 mL/g COD. It also showed that only 18.9% of the fluorescent components were degraded and 13 recalcitrant chemicals were identified to be hard bio-degradable organics in AD process.
88. 题目: Removal of tetracycline from an aqueous solution using manganese dioxide modified biochar derived from Chinese herbal medicine residues
期刊: Environmental Research
作者: Qibin Shen, Zhaoyue Wang, Qiao Yu, Yang Cheng, Zidan Liu, Taiping Zhang, Shaoqi Zhou
摘要: Biochar (BC) derived from Chinese herbal medicine residues has been investigated for its performance as a potential adsorbent in tetracycline (TC) removal. In the present study, a chemical co-precipitation method was carried out to prepare manganese dioxide modified biochar (Mn-BC) to increase its sorption capacity. The properties of the modified biochar were characterized for further enhancing TC removal from an aqueous solution. Mn-BC was successfully synthesized and resulted in a much higher specific surface area, total pore volume and pore diameter. The sorption kinetics of TC on Mn-BC was described by the pseudo-second-order model. The sorption data of Mn-BC were fitted by Langmuir and Freundlich models. The study findings revealed a maximum adsorption capacity of Mn-BC (1:10) to TC was up to 131.49 mg/g. The adsorption process was endothermic and spontaneous. The degradation of TC was further enhanced by MnO2 acting as an oxidizer on Mn-BC. Overall, the modified biochar derived from Chinese herbal medicine residues is a superior alternative for the removal of TC from an aqueous solution.
89. 题目: Total soil organic carbon increases but becomes more labile after afforestation in China’s Loess Plateau
期刊: Forest Ecology and Management
作者: Qingyin Zhang, Xiaoxu Jia, Xiaorong Wei, Mingan Shao, Tongchuan Li, Qiang Yu
摘要: Afforestation of cropland is recommended as an effective approach to enhance soil organic carbon (SOC) sequestration and labile organic C fractions. However, the stabilization of SOC and its labile organic C fractions on the Loess Plateau is largely unknown. Our objective was to quantify total SOC concentration and labile organic C fractions in the 0–20 cm soil depth for four land use types on the Loess Plateau, including cropland and three afforested areas (composed of R. pseudoacacia forests, P. tabuliformis forests, and R. pseudoacacia + P. tabuliformis mixed forests). Total SOC concentration, particulate organic C (POC), dissolved organic C (DOC), microbial biomass C (MBC), and potassium permanganate-oxidizable C (KMnO4-C) were measured. Carbon management index (CMI) was also calculated. Afforestation showed a significant positive effect on total SOC and labile organic C fractions, compared with cropland. Afforestation with R. pseudoacacia, P. tabuliformis, and R. pseudoacacia + P. tabuliformis significantly increased POC by 57.4%, 22.2%, and 44.4% in the 0–5 cm soil layer; and similar increases were observed in the 5–10 cm and 10–20 cm layers. Similar trends to those observed for POC in response to afforestation were also seen for DOC, MBC, and KMnO4-C. Afforestation with R. pseudoacacia resulted in the highest total SOC concentrations and labile organic C fractions among the three afforestation treatments. These findings suggested that although afforestation can significantly promote total SOC accumulation, especially with R. pseudoacacia, SOC may become more labile following afforestation in the future.
90. 题目: Soil acidification as an additional driver to organic carbon accumulation in major Chinese croplands
作者: Xinmu Zhang, Jingheng Guo, Rolf David Vogt, Jan Mulder, Yajing Wang, Cheng Qian, Jingguo Wang, Xiaoshan Zhang
摘要: Significant increase in soil organic carbon (SOC) has been found in Chinese croplands. Current literature largely attributes this to the increased organic C inputs from manure, crop straw and root. However, using a meta-analysis of 185 long-term trials and 6669 spatial data pairs across China, we show here that soil acidification is an additional significant cause for the SOC accumulation. Results from long-term experiments showed that soil acidification due to excessive N fertilization coincided with, and significantly (p < 0.01) contributed to, the observed SOC accrual. Spatially, the amount of SOC increase caused by soil acidification decreased with increasing initial content. In addition, the soil’s basal respiration rate (SBRR), microbial metabolic quotient (MMQ) and the percentage of dissolved organic carbon (DOC) relative to total SOC decreased significantly (p < 0.01) with soil pH decline. This indicates that soil acidification depresses the decomposition of organic matter, both by decreasing microbial activity and by increasing protection of SOC by mineral phases. Thus, N-induced soil acidification promotes the SOC accumulation in Chinese croplands, by increasing its stability. In contrast to the current view emphasizing the importance of organic C inputs, our meta-analysis reveals an alternative mechanism connecting N-fertilization and the resulting SOC accumulation in agricultural ecosystems. More research is needed to further clarify its operating processes, relative importance, and agro-environmental consequences.
91. 题目: Innovative spherical biochar for pharmaceutical removal from water: Insight into adsorption mechanism
期刊: Journal of Hazardous Materials
作者: Hai Nguyen Tran, Fatma Tomul, Ha Thi Hoang Nguyen, Dong Thanh Nguyen, Eder C. Lima, Giang Truong Le, Chang-Tang Chang, Vhahangwele Masindi, Seung Han Woo
摘要: In this study, we developed innovative biochars with high porosity and excellent paracetamol (PRC) adsorption capacity. The optimal pyrolysis temperatures of spherical biochar (derived from pure glucose) and non-spherical biochar (from pomelo peel wastes) were obtained at 900 °C and 700 °C, respectively. Various advanced techniques were applied to characterize the prepared biochars. Spherical and non-spherical biochars exhibited large specific surface area (1292 and 1033 m2/g) and high total pore volume (0.704 and 1.074 cm3/g), respectively. The adsorption behavior of PRC onto two biochars was conducted utilizing batch experiments. Results demonstrated that the adsorption process was slightly affected by the change of solution pH (2–11) and addition of NaCl (0.05–1.0 M) and was able to achieve fast equilibrium (∼120 min). The maximum adsorption capacity of spherical biochar (286 mg/g) for PRC was approximately double that of non-spherical biochar (147 mg/g). The signal of thermodynamic parameters was negative ΔG° and ΔH° values, but positive ΔS° value. The adsorption mechanism consisted of pore-filling, hydrogen bonding formations, n-π and π-π interactions, and van der Waals force. The adsorption capacities of two biochar were insignificantly dependent on different real water samples containing PRC. Consequently, the biochars can serve as a green and promising material for efficiently removing PRC from water.
92. 题目: Microbial extracellular polysaccharide production and aggregate stability controlled by switchgrass (Panicum virgatum) root biomass and soil water potential
期刊: Soil Biology and Biochemistry
作者: Yonatan Sher, Nameer R. Baker, Don Herman, Christina Fossum, Lauren Hale, Xing-Xu Zhang, Erin Nuccio, Malay Saha, Jizhong Zhou, Jennifer Pett-Ridge, Mary Firestone
摘要: Deep-rooting perennial grasses are promising feedstocks for biofuel production, especially in marginal soils lacking organic material, nutrients, and/or that experience significant water stress. Perennial grass roots influence surrounding soil conditions and microbial activities, and produce extracellular polymeric substances (EPS) composed primarily of extracellular polysaccharides (EPSac). These polymers can alleviate microbial moisture and nutrient stress, and enhance soil characteristics through improved water retention and aggregate stability—which may in turn enhance carbon persistence. In this study we used a 13CO2 greenhouse tracer experiment to examine the effect of switchgrass cultivation on EPSac production and origin in a marginal soil with five fertilization/water treatments (control, +N, +NP, +P, low water), and compared these results with measurements of field soils collected after long-term switchgrass cultivation. Soils with added nitrogen and phosphorus (+NP) had the highest root biomass, EPSac and percentage of water-stable soil aggregates. Multiple linear regression analyses revealed that root biomass and soil water potential were important determinants of soil EPSac production, potentially by controlling carbon supply and diurnal changes in moisture stress. Path analysis showed that soil aggregation was positively correlated with bulk soil EPSac content and also regulated by soil water potential. High mannose content indicated the majority of EPSac was of microbial origin and 13CO2 labeling indicated that 0.18% of newly fixed plant carbon was incorporated into EPSac. Analysis of field soils suggests that EPSac is significantly enhanced after long-term switchgrass cultivation. Taken as a whole, our greenhouse and field results demonstrate that switchgrass cultivation can promote microbial production of EPSac, providing a mechanism to enhance aggregation in marginal soils.
93. 题目: Converting industrial waste cork to biochar as Cu (II) adsorbent via slow pyrolysis
期刊: Waste Management
作者: Qihang Wang, Zongyuan Lai, Jun Mu, Demiao Chu, Xiaorong Zang
摘要: Cork is light, porous, carbon-rich, and renewable, which leads to competitive advantages in the preparation of biochar, as compared to other biomass material. In this work, we propose to convert cork powder into cork-based biochar as Cu (II) adsorbent via slow pyrolysis, thereby providing a reliable and simple method for recycling cork industrial waste. The physicochemical properties of cork-based biochar prepared under different pyrolysis temperatures (450, 550, 650, and 750 °C) and pyrolysis time (0.5, 1.0, 1.5, and 2.0 h) were characterized by elemental analysis, FT-IR, XRD, N2 adsorption and SEM. The adsorption capacity of cork-based biochar on heavy metal ions was further evaluated by Cu ion adsorption testing. Results showed that the cork-based biochar produced under conditions of higher pyrolysis temperature and time, has higher aromaticity and lower polarity, larger specific surface area, and enhanced Cu ion adsorption capacity. The maximum specific surface area of cork-based biochar prepared at 750 °C for 0.5 h was 392.5 m2/g, which surpasses most other biochars reported in previous studies, which are beneficial to the application of wastewater management. The SEM image demonstrated that the biochar retains the special hollow polyhedral cell structure of raw material cork. Furthermore, a large number of pores formed on the cell wall after high temperature pyrolysis, and the cells are connected with each other through these open pores. Finally, cork-based biochar exhibits superior Cu ion adsorption capacity (18.5 mg/g) with a shorter equilibrium time (4 h), which gives it a competitive advantage to similar adsorbents.
94. 题目: Land-use controls on nutrient loads in aquifers draining agricultural and mixed-use karstic watersheds
期刊: Environmental Monitoring and Assessment
作者: G. V. Tagne, C. Dowling
摘要: Agricultural nonpoint source pollution from the upper areas of the Upper Mississippi, Missouri, and Ohio River basins accounts for the majority of the excess nitrogen that leads to the Gulf of Mexico’s hypoxic zone. However, agriculture landscapes across the USA, Europe, and China are undergoing major changes related to the proliferation of confined animal feeding operations (CAFOs) that account for a greater proportion of point source contamination. Mitigating long-term nutrient inputs at a large scale (Mississippi River Basin) requires understanding these microscale changes at the small watershed level (less than 100 km2). To assess the control of land-use and subsurface hydrological processes on nutrient fate and transport, temporal patterns in nutrient concentrations in a mixed land-use karstic watershed were analyzed. To assess the control of differential land-use sources on total inorganic nitrogen (TIN) loads within the watershed, 4 months of weekly water sampling was performed at a spring location and at two underground conduit locations. The observed temporal variations in nutrient concentrations are primarily associated with seasonal changes in land-use associated with corn growth. Data show that land-use sources explain much of the temporal variability of TIN at the spring when weighted against the hydrological factor. End-member-mixing analysis of dissolved organic carbon (DOC) shows a progressive increase in the contribution of DOC-enriched sources and a more labile form of carbon toward the harvest time. Overall, during high flow, nonpoint source infiltration from manure-fertilized croplands in the northern branch (NB) dominate DOC loads. Because conduit-dominated karstic aquifers are more susceptible to contamination from direct and fast (< 7 h) subsurface infiltration during late summer rainfall period (July to August), a slight advance in the timing of manure application could substantially reduce nutrient loads to local groundwater. A combined evaluation of subsurface hydrological processes and land-use factors controlling nutrients at the scale of small watersheds is crucial to developing site-specific nutrient management plans and managing the Gulf of Mexico’s hypoxic zone.
95. 题目: Heterogeneous Fenton oxidation of trichloroethylene catalyzed by sewage sludge biochar: Experimental study and life cycle assessment
作者: Yu-Fong Huang, Yu-Yang Huang, Pei-Te Chiueh, Shang-Lien Lo
摘要: Heterogeneous Fenton oxidation of trichloroethylene (TCE) catalyzed by sewage sludge biochar was studied. The highest TCE removal efficiency was 83% at pH 3.1, catalyzed by 300 W biochar. The biochars produced at higher microwave power levels provided better catalytic effect, due to higher iron contents and specific surface areas. Reactivity of sewage sludge biochar maintained after several uses, which provides an advantage for using as a permeable reactive barrier to remediate groundwater pollution. Chromium, copper, nickel, lead, and zinc were found in the leachate generated from sewage sludge biochar, and most of the concentrations were lower than the standards for non-drinking water use. Besides, copper, zinc, and iron were found in the reaction solutions of Fenton oxidation. Because of the highest dosage required for Fenton oxidation, the environmental impact caused by 200 W biochar is highest. The environmental impact caused by 300 W biochar is lowest. Among the four endpoint impact categories in the life cycle assessment (LCA), human health is the highest concern, whereas ecosystem quality is the least. According to experimental and LCA results, the optimum microwave power level would be 300 W. The primary impact source is microwave pyrolysis because of high energy usage.
96. 题目: Microalgae carbon fixation integrated with organic matters recycling from soybean wastewater: Effect of pH on the performance of hybrid system
作者: Chunfeng Song, Xiaoxuan Han, Yiting Qiu, Zhengzheng Liu, Shuhong Li, Yutaka Kitamura
摘要: Microalgae have been considered as promising alternative for CO2 fixation and wastewater purification. In our previous work, a hybrid microalgae CO2 fixation concept has been put forward, which initially used carbonate solution absorb CO2, and then provided obtained bicarbonate as nutrition for microalgae growth to avoid the challenge of low CO2 solubility and carbon fixation efficiency in the conventional process. In this work, the proposed hybrid system was further intensified via integrating soybean wastewater nutrition removal with bicarbonate-carbon (NH4HCO3 and KHCO3) conversion. The investigation results indicated that the maximum biomass productivity (0.74 g L−1) and carbon bioconversion efficiency (46.9%) were achieved in low-NH4HCO3 concentration system with pH adjusted to 7. pH adjustment of different bicarbonate systems also enhanced total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD) removal efficiency up to 87.5%, 99.5% and 77.6%, respectively. In addition, maximum neutral lipid (14.4 mg L−1·d−1) and polysaccharide (14.5 mg L−1·d−1) productivities could be obtained in the KHCO3 systems, while higher crude protein productivity (48.1 mg L−1·d−1) was yielded in the NH4HCO3 systems.
97. 题目: Drivers of benthic extinction during the early Toarcian (Early Jurassic) at the northern Gondwana paleomargin: Implications for paleoceanographic conditions
期刊: Earth-Science Reviews
作者: Wolfgang Ruebsam, Matías Reolid, Abbas Marok, Lorenz Schwark
摘要: During the early Toarcian multiple environmental perturbations led to the genesis of the Toarcian Oceanic Anoxic Event (T-OAE), expressed by the widespread occurrence of black shales that were formed under oxygen-deficient conditions. Factors promoting organic matter preservation also drove benthic extinction due to low aqueous O2 levels and habitats poisoned by H2S. However, the development of benthic barren intervals in oxygenated shelf areas, lacking black shales, indicates that even in these areas benthic communities experienced a crisis. To understand environmental changes and to determine factors driving benthic extinction we applied paleontological and geochemical techniques to the organic matter-lean Ratnek El Kahla section (Saharan Atlas, Algeria). During the Early Jurassic the study site was located at the northern Gondwana paleomargin, belonging to the southern West Tethys Shelf. The benthic barren interval coincides with the climax of the T-OAE that correlates with a major carbon cycle perturbation, expressed by a negative carbon isotope excursion. Compared to background values, sediments of the benthic barren interval are enriched in organic matter and redox-sensitive metals. In combination with the enhanced preservation of intact bacterial lipids and increased rates of organic matter sulfurization, data attest to a decline in pore water O2 and increased H2S concentration. It is thus reasonable to propose that, similar to northern shelf areas, benthic communities suffered from prolonged oxygen-deficient conditions. Absence of benthic activity and less intensive sediment reworking in combination with enhanced organic matter sulfurization favored organic matter preservation. Productivity proxies and δ15N data indicate moderate primary productivity rates. Lowered aqueous O2 levels did not result from excessive aerobic organic matter breakdown. Seafloor anoxia was rather promoted by rising seawater temperatures and sluggish ocean circulation during a transition from icehouse into a greenhouse climate. These conditions may have been a pre-requirement for genesis of the T-OAE.
98. 题目: Simulated photocatalytic aging of biochar in soil ecosystem: Insight into organic carbon release, surface physicochemical properties and cadmium sorption
期刊: Environmental Research
作者: Guixiang Quan, Qinya Fan, Liqiang Cui, Andrew R. Zimmerman, Hailong Wang, Zhiyuan Zhu, Bin Gao, Limin Wu, Jinlong Yan
摘要: Photochemical/photocatalytic reaction, one of the aging pathway of biochar in soil, not only changed the physicochemical properties of biochar, but also affected the migration and transformation of pollutants. Wheat straw biochar was photocatalytic aged in a Fenton-like system using organic acid as buffer solution under light sources, the organic carbon release and surface chemical changes of biochar were investigated to illustrate the adsorption behaviors. With Fe(III) or α-Fe2O3 added, the total organic carbon (TOC) of aged biochar solution was influenced more by buffer system than light sources, with the highest of 420.59 mg L−1 in citric acid system. The production of the hydroxyl radical (OH·) at citric/Fe(III) system was higher than the oxalic/Fe(III) system under the Hg lamp and showed an increasing trend with time. With light exposure, the porous structure of the biochar altered and surface area increased from 7.613 to 29.74 m2 g−1. Meanwhile, the adsorption of cadmium ion by biochar aged in citric/Fe(III) system also showed an increased adsorption capacity with a maximum of 73.54 mg g−1. So, a well understanding of biochar physicochemical properties changes under natural ecosystem was undoubtedly useful for scientific assessment the long-term feasibility of biochar as soil remediation.
99. 题目: Model averaging for mapping topsoil organic carbon in France
作者: Songchao Chen, Vera Leatitia Mulder, Gerard B.M. Heuvelink, Laura Poggio, Manon Caubet, Mercedes Román Dobarco, Christian Walter, Dominique Arrouays
摘要: The soil organic carbon (SOC) pool is the largest terrestrial carbon (C) pool and is two to three times larger than the C stored in vegetation and the atmosphere. SOC is a crucial component within the C cycle, and an accurate baseline of SOC is required, especially for biogeochemical and earth system modelling. This baseline will allow better monitoring of SOC dynamics due to land use change and climate change. However, current estimates of SOC stock and its spatial distribution have large uncertainties. In this study, we test whether we can improve the accuracy of the three existing SOC maps of France obtained at national (IGCS), continental (LUCAS), and global (SoilGrids) scales using statistical model averaging approaches. Soil data from the French Soil Monitoring Network (RMQS) were used to calibrate and evaluate five model averaging approaches, i.e., Granger-Ramanathan, Bias-corrected Variance Weighted (BC-VW), Bayesian Modelling Averaging, Cubist and Residual-based Cubist. Cross-validation showed that with a calibration size larger than 100 observations, the five model averaging approaches performed better than individual SOC maps. The BC-VW approach performed best and is recommended for model averaging. Our results show that 200 calibration observations were an acceptable calibration strategy for model averaging in France, showing that a fairly small number of spatially stratified observations (sampling density of 1 sample per 2500 km2) provides sufficient calibration data. We also tested the use of model averaging in data-poor situations by reproducing national SOC maps using various sized subsets of the IGCS dataset for model calibration. The results show that model averaging always performs better than the national SOC map. However, the Modelling Efficiency dropped substantially when the national SOC map was excluded in model averaging. This indicates the necessity of including a national SOC map for model averaging, even if produced with a small dataset (i.e., 200 samples). This study provides a reference for data-poor countries to improve national SOC maps using existing continental and global SOC maps.
100. 题目: Development of pedotransfer functions by machine learning for prediction of soil electrical conductivity and organic carbon content
作者: K.K. Benke, S. Norng, N.J. Robinson, K. Chia, D.B. Rees, J. Hopley
摘要: The pedotransfer function is a mathematical model used to convert direct soil measurements into known and unknown soil properties. It provides information for modelling and simulation in soil research, hydrology, environmental science and climate change impacts, including investigating the carbon cycle and the exchange of carbon between soils and the atmosphere to support carbon farming. In particular, the pedotransfer function can provide input parameters for landscape design, soil quality assessment and economic optimisation. The objective of the study was to investigate the feasibility of using a generalised pedotransfer function derived with a machine learning method to predict soil electrical conductivity (EC) and soil organic carbon content (OC) for different regional locations in the state of Victoria, Australia. This strategy supports a unified approach to the interpolation and population of a single regional soils database, in contrast to a range of pedotransfer functions derived from local databases with measurement sets that may have limited transferability. The pedotransfer function generation was based on a machine learning algorithm incorporating the Generalized Linear Mixed Model with interactions and nested terms, with Residual Maximum Likelihood estimation, and a predictor-frequency ranking system with step-wise reduction of predictors to evaluate the predictive errors in reduced models. The source of the data was the Victorian Soil Information System (VSIS), which is a database administered for soil information and mapping purposes. The database contains soil measurements and information from locations across Victoria and is a repository of historical data, including monitoring studies. In total, data from 93 projects were available for inputs to modelling and analysis, with 5158 samples used to derive predictors for EC and 1954 samples used to derive predictors for OC. Over 500 models were tested by systematically reducing the number of predictors from the full model. Five-fold cross-validation was used for estimation of model mean-squared prediction error (MSPE) and mean-absolute percentage error (MAPE). The results were statistically significant with only a gradual reduction in error for the top-ranked 50 models. The prediction errors (MSPE and MAPE) of the top ranked model for EC are 0.686 and 0.635, and 0.413 and 0.474 for OC respectively. The four most frequently occurring predictors both for EC and OC prediction across the full set of models were found to be soil depth, pH, particle size distribution and geomorphological mapping unit. The possible advantages and disadvantages of this approach were discussed with respect to other machine learning approaches.