论文检索
总访问量：4853321次
总访客量：243018人
所有论文
28061. 题目: Organic carbon content controls the severity of water repellency and the critical moisture level across New Zealand pasture soils
文章编号: N18122206
期刊: Geoderma
作者: Cecilie Hermansen, Per Moldrup, Karin Müller, Peter Weber Jensen, Carlo van den Dijssel, Paramsothy Jeyakumar, Lis W. de Jonge
更新时间: 2018-12-22
摘要: Organic matter can render soil hydrophobic and cause soil water repellency (SWR) which has large implications for agriculture. Consequences such as fingered flow, uneven wetting patterns, and increased overland flow reduce irrigation efficiency and plant nutrient availability. The phenomenon of SWR is a transient soil property depending, inter alia, on soil water content (w). Soil can exhibit SWR from oven-dry w until the critical w where it again becomes fully wettable (wNON). The total SWR can be obtained from the nonlinear SWR-w relationship as the integrated trapezoidal area under the SWR-w curve (SWRAREA). We analyzed 78 soil samples, representing five dominant soil orders in the South Island of New Zealand. The soils had a large range in clay (0.000–0.520 kg kg−1) and organic carbon (OC) content (0.021–0.217 kg kg−1). The degree of SWR was measured on soils at air-dry conditions (SWRAD) and after heat-pretreatment at 60 (SWR60) and 105°C (SWR105). Further, SWR was measured in small w increments above air-dry w until wNON was reached. The SWR-w curves were either unimodal or bimodal, or no SWR occurred. SWRAREA ranged from 0.16 to 26.82 mN m−1 kg kg−1. Among the five soil orders tested, the Podzols exhibited the highest severity in SWR, whereas the Semiarid soils were the least hydrophobic soils. In conclusion, OC was the main factor for controlling the severity of SWR. Though, pH also had minor effects on SWR. Further, an upper limit critical water content was derived from the simple relationship between the wNON and OC, which could be applied to improve irrigation practices of pastoral soils. However, there is a need for further testing on different soils and land uses.
28062. 题目: Effects of composting and carbon based materials on carbon and nitrogen loss in the arable land utilization of cow manure and corn stalks
文章编号: N18122205
期刊: Journal of Environmental Management
作者: Ruixue Chang, Ying Yao, Wenchao Cao, Jue Wang, Xuan Wang, Qing Chen
更新时间: 2018-12-22
摘要: Recycling organic wastes to arable land as fertilizers has been recognized as a sustainable utilization to reduce environmental pollution. Techniques used for the treatment of organic wastes determine their nutrient contents and thus fertilizer efficiency for agricultural applications. The current study investigated the influences of composting and carbon based materials (biochar and woody peat), on carbon and nitrogen loss in the process of agricultural wastes utilization in the soil batch experiments. The results indicated composting process significantly strengthened the organic matter mineralization, increased the carbon loss rates from 33.46-38.96% to 60.54–86.15% and the nitrogen loss rates from 5.01-22.22% to 48.64–58.16%, dominant lost as carbon dioxide (CO2) and ammonia (NH3) emissions. Addition of carbon based materials could effectively reduce the carbon and nitrogen loss during both composting and soil incubation process. When the composted organic wastes were used in the soil batch experiments, woody peat was more effective to reduce nitrogen loss, while biochar was more effective to control carbon loss. When organic wastes were directly fertilized to soil, biochar could effectively reduce nitrogen loss. These results suggested that fertilizing raw agricultural wastes to with carbon based materials could reduce carbon and nitrogen losses, and increased the nutrient bioavailability in soil in comparison with their farmland application after composting.
28063. 题目: Graphene Oxide Quantum Dots Stimulate Indigenous Bacteria to Remove Oil Contamination
文章编号: N18122204
期刊: Journal of Hazardous Materials
作者: Li Mu, Qixing Zhou, Yujie Zhao, Xiaowei Liu, Xiangang Hu
更新时间: 2018-12-22
摘要: Oil spills occur frequently worldwide, resulting in severe damage to water and to human health. Polycyclic aromatic hydrocarbons (PAHs) are the primary toxic components in oil contamination. PAH-degrading microbes have attracted significant attention, but difficulty in their selection and proliferation limits their applications. Graphene oxide quantum dots (GOQDs) improve the proliferation of an indigenous PAH-degrading strain, Bacillus cereus, more effectively than large graphene oxide flakes. Bacillus cereus can metabolize a variety of xenobiotic aromatic compounds as carbon sources and is used in bioremediation. GOQDs contain a variety of aromatic hydrocarbon structures, explaining why the bacteria achieve strong tolerance to PAHs. GOQD-activated cytokinesis increases the secretion of substances important for biofilm formation (extracellular polymeric substances), which further accelerates PAH removal. Proteomic analysis reveals the molecular mechanisms underlying GOQD-induced microbial proliferation. GOQDs induce the overexpression of microbial divisomal proteins associated with division initiation, DNA replication and peptidoglycan hydrolysis/synthesis. Importantly, PAH removal mediated by GOQD-treated Bacillus cereus does not require the addition of GOQDs. The effects of GOQDs on a strain persist for at least 20 generations, suggesting their possible use in low-cost applications. This work proposes a strategy to remove oil contamination using an indigenous bacterial system enhanced by nanomaterials.
图文摘要:
28064. 题目: Fouling formation in membrane contactors for methane recovery from anaerobic effluents
文章编号: N18122203
期刊: Journal of Membrane Science
作者: Wichitpan Rongwong, Kunli Goh, G.S.M.D.P. Sethunga, Tae-Hyun Bae
更新时间: 2018-12-22
摘要: Fouling in membrane contactors for recovery of dissolved methane (CH4) was investigated in this work. Two types of effluents from anaerobic membrane bioreactor (AnMBR) and upflow anaerobic sludge blanket (UASB) were tested under a continuous operational mode. Due to the higher fouling propensity of the UASB effluent, membrane fouling was more drastic, leading to a greater decline in the CH4 desorption flux with respect to the operational time. Also, the flux was observed to be influenced by the gas-liquid contact time and declined more severely with increasing liquid velocity. Membrane characterization revealed cake layer formation as the source of membrane fouling while foulants characterization indicated that the majority of the foulants were protein-like-substances with fluorescence spectra showing signals close to that of extracellular polymeric substances. On this basis, a mass transfer analysis was performed to understand the fouling resistance exerted by the cake layer and identify a parameter which best described the fouling mechanism. It was found that cake thickness can be used to express the change in fouling resistance in the case of the AnMBR effluent, while cake porosity was a better parameter in the case of the UASB effluent.
28065. 题目: Biological sources of sedimentary organic matter in Neoproterozoic–Lower Cambrian shales in the Sichuan Basin (SW China): Evidence from biomarkers and microfossils
文章编号: N18122202
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Ning Wang, Meijun Li, Haitao Hong, Daofu Song, Xingwang Tian, Peng Liu, Ronghui Fang, Guo Chen, Maolin Wang
更新时间: 2018-12-22
摘要: Study of the occurrence and formation of sedimentary organic matter in the Sichuan Basin, southern China, provides valuable insights into the biological sources and compositions of Neoproterozoic to Lower Cambrian shales. Rock samples from two sets of shales in the Sichuan Basin and adjacent areas, including the Ediacaran Doushantuo shale and the Lower Cambrian Qiongzhusi shale in the Gaoshiti-Moxi and Ziyang-Weiyuan areas were collected and geochemically analyzed in this study.The distribution of biomarkers, stable carbon isotope compositions and microfossil characteristics reveal that eukaryotic algae including chlorophytes, pelagophyceae, dinoflagellates, diatoms (or their ancestors) and sponges proliferated widely during the Late Neoproterozoic to Early Cambrian in the Sichuan Basin. Cyanobacteria, some α-Proteobacteria, rhizobiales and aerobic methanotrophs also made a contribution to organic matter in the studied shales. Aerobic methanotrophs that utilize 13C-depleted substrates such as CH4 as carbon sources may have been the cause of anomalous 13C-depleted kerogen in the study area.
28066. 题目: Effect of temperature, pH and total organic carbon variations on microbial turnover of 13C315N-glyphosate in agricultural soil
文章编号: N18122201
期刊: Science of The Total Environment
作者: Angelica M. Muskus, Martin Krauss, Anja Miltner, Ute Hamer, Karolina M. Nowak
更新时间: 2018-12-22
摘要: Glyphosate is the best-selling and the most-used broad-spectrum herbicide worldwide. Microbial conversion of glyphosate to CO2 and biogenic non-extractable residues (bioNER) leads to its complete degradation. The degradation of glyphosate may vary in different soils and it depends on environmental conditions and soil properties. To date, the influence of temperature, soil pH and total organic carbon (TOC) on microbial conversion of glyphosate to bioNER has not been investigated yet. The pH or TOC of an agricultural original soil (pH 6.6, TOC 2.1%) was modified using sulfuric acid or farmyard manure (FYM), respectively. Each treatment: original (I), 3% TOC (II), 4% TOC (III), pH 6.0 (IV) and pH 5.5 (V) was amended with 13C315N-glyphosate and incubated at 10 °C, 20 °C and 30 °C for 39 days. The temperature was the main factor controlling the mineralization and the extractable 13C315N-glyphosate, whereas higher TOC content and lower pH resulted in enhanced formation of 13C-bioNER. After 39 days the cumulative mineralization of 13C-glyphosate was in the range of 12–22% (10 °C), 37–47% (20 °C) and 43–54% (30 °C). Extractable residues of 13C-glyphosate were in the range of 10–21% (10 °C) and 4–10% (20 °C and 30 °C); whereas those of 15N-glyphosate were as follows 20–32% (10 °C) and 12–25% (20 °C and 30 °C). The 13C-NER comprised about 53–69% of 13C-mass balance in soils incubated at 10 °C, but 40–50% in soils incubated at 20 °C and 30 °C. The 15N-NER were higher than the 13C-NER and varied between 62% and 74% at 10 °C, between 53% and 81% at 20 °C and 30 °C. A major formation of 13C-bioNER (72–88% of 13C-NER) at 20 °C and 30 °C was noted in soil amended with FYM. An increased formation of 15N-bioNER (14–17% of 15N-NER) was also observed in FYM-amended soil. The xenobiotic 15N-NER had a major share within the 15N-NER and thus need to be considered when assessing the environmental risk of glyphosate-NER.
图文摘要:
28067. 题目: Al/Fe mineral controls on soil organic carbon stock across Tibetan alpine grasslands
文章编号: N18122106
期刊: Journal of Geophysical Research: Biogeosciences
作者: Kai Fang, Shuqi Qin, Leiyi Chen, Qiwen Zhang, Yuanhe Yang
更新时间: 2018-12-21
摘要: Adequate understanding of the controlling factors of soil carbon (C) stock is crucial for improving the predictability of Earth System Models in exploring terrestrial C‐climate feedback. Current studies, however, mainly focus on climatic and edaphic variables, and rarely explore the effects of mineral protection in regulating soil organic C (SOC) stock over broad geographic scale. Particularly, the relative importance of mineral protection compared with other factors is unclear. Based on large‐scale soil inventory, here we filled this knowledge gap by exploring the effects of Al/Fe‐(hydr) oxides on SOC and three C fractions across Tibetan alpine grasslands via linear regression, partial correlation and variance partitioning analyses, and also comparing the degree of mineral protection in alpine grasslands with other ecosystems. Our results showed that SOC and C fractions across Tibetan alpine grasslands were regulated by Al/Fe‐(hydr) oxides, with the incorporation of mineral variables increasing the explained variations by 10.1% for SOC content, 13.4% for coarse particulate organic matter, 12.6% for microaggregate associated C, and 21.9% for silt and clay associated C. Moreover, the contribution of mineral effects exceeded that of climatic and edaphic factors, particularly in the silt and clay associated C fraction. In addition, about 15.8±12.0% of SOC pools was associated with Fe, which was equal or even higher than temperate and tropical‐subtropical ecosystems. Taken together, these results demonstrate the significant role of Al/Fe minerals in the stabilization of SOC across Tibetan alpine grasslands, highlighting the importance of incorporating C‐mineral interactions into ESMs for better understanding the terrestrial C‐climate feedback.
28068. 题目: The influence of sediment‐derived dissolved organic matter in the Vistula River Estuary/Gulf of Gdansk
文章编号: N18122105
期刊: Journal of Geophysical Research: Biogeosciences
作者: Heather E. Reader, Franziska Thoms, Maren Voss, Colin A. Stedmon
更新时间: 2018-12-21
摘要: Dissolved organic matter (DOM) concentrations in sediment porewaters are often orders of magnitude higher than in the overlying water column resulting in a diffusive flux of DOM from sediments. The intensity and fate of this DOM flux is poorly understood. The Gulf of Gdansk in the Southern Baltic Sea is dominated by the Vistula River, one of the largest and most anthropogenically impacted rivers in the Baltic Sea catchment. The sediment characteristics of the region are varied, from mixed sandy conditions near shore to mud sediments in the Gdansk Deep. We investigated the significance of sediment‐derived DOM in the Gulf of Gdansk in comparison to that supplied by the river. Sediment‐derived DOM in the region was found to have an organic matter fluorescence signature distinct from the DOM in the water column. The visible wavelength fluorescence could be used to distinguish organic matter from near shore sediments influenced by riverine sources and organic matter from deeper offshore sediments, influenced by more pelagic sources. UVA wavelength fluorescence dominated the sediment flux but was rapidly removed in bottom waters suggesting that it may contribute to bottom water oxygen consumption. While there is potential for DOM fluxes from sediments in the Gulf of Gdansk, the high background pelagic concentration of DOM in these waters and the much stronger influence of the Vistula River can mask the contributions from sediments.
28069. 题目: The microbial network in naturally fertile paddy soil possibly facilitates functional recruitment in the rice mature stage
文章编号: N18122104
期刊: Applied Soil Ecology
作者: Xuesong Luo, Shun Han, Xiaoqian Fu, Xiang Li, Li Wang, Shaobing Peng, Wenli Chen, Qiaoyun Huang
更新时间: 2018-12-21
摘要: How agriculture practice, especially the nitrogen fertilization, influences different paddy soil microbial ecosystems remains unclear. The bacterial communities in two paddy fields, which were distinguished by the natural fertility level, were utilized in this study. Each field held two control plots and two nitrogen-fertilized ones. The microbial communities mainly differed in their relative abundances of Proteobacteria and Chloroflexi between the two fields. However, they were very similar in the α-diversity and enzymatic functions, as well as their resistances indexes in response to the nitrogen fertilizers. Redundancy analysis indicated that phosphorus, nitrogen and potassium contents significantly explained the variability of the communities in the two fields total potassium (TK) plus nitrogen level and TK alone significantly explained the variation of the microbial communities in the high yield field and the low yield, respectively. Network analysis data showed that the microbial community in the high-yield field possessed a higher connectivity, which might facilitate recruiting more microbes that were predicted to drive organic matter decomposition, sulfate/iron reduction, nitrogen retention, and methane oxidation at the mature stage. The use of nitrogen fertilizer in the low yield field would help to recruit microbial functions similar to those in the high-yield at the stage. This ecological process possibly stimulated nutrient availability for rice production in the present case.
图文摘要:
28070. 题目: The influence of biochar and compost mixtures, water content, and gas flow rate, on the continuous adsorption of methane in a fixed bed column
文章编号: N18122103
期刊: Journal of Environmental Management
作者: Helen La, J. Patrick A. Hettiaratchi, Gopal Achari
更新时间: 2018-12-21
摘要: Biofiltration is an excellent alternative for the treatment of diffuse emissions of methane (CH4) that cannot be treated by physical/chemical means or recovered for energy. Despite the advances on CH4 biological treatment technologies, they are limited by the low aqueous solubility of CH4 into the biofilm where CH4 mineralization occurs. In this study, the CH4 adsorption kinetics, adsorption capacity and transport behavior of CH4 was studied in batch experiments and in a fixed-bed column by varying the biochar and compost mixtures under 5-levels, 3 different water contents (dry, 15% and 30% water holding capacity), and 2 inlet flow rates. Experimental results were formally tested using analysis of variance (ANOVA) in order to draw objective conclusions based on statistical inference. As CH4 biofiltration requires water addition to maintain microbial activity, these results indicate adsorption capacity is not lost with water addition if biochar content is the dominant packing material. The Langmuir isotherm described the data best (R2 = 0.99). Maximum adsorption capacity by monolayer adsorption, or qmax, is relatively similar with or without the addition of water as long as the biochar component is the dominant material at 3.5 mg CH4/g medium for a 7:1 biochar: compost, v/v mixture. Empirical regression models for qo, kTh, (Thomas model) and τ and KYN (Yoon-Nelson model) were developed for the break through curves of CH4. The current work demonstrates the applicability of utilizing biochar, a relatively inexpensive adsorbent, can compensate for the low solubility of CH4 and overcome the rate-limiting step of mass transfer from the gas phase and into the methanotrophic biofilm. Further, biochar may be a reliable back-up system for CH4 storage especially for fluctuating inlet loads that may be encountered in industrial applications adsorbing up to 13 mg CH4/g biochar under dry conditions.
图文摘要:
28071. 题目: Effect of water washing pretreatment on property and adsorption capacity of macroalgae-derived biochar
文章编号: N18122102
期刊: Journal of Environmental Management
作者: Patrick Boakye, Hai Nguyen Tran, Dae Sung Lee, Seung Han Woo
更新时间: 2018-12-21
摘要: The effects of water washing pretreatment process on the property and adsorption capacity of biochar were investigated at different biochar/water ratios from 1:5 to 1:100 (w/v). Saccharina japonica macroalgae-derived biochars (B300, B450, and B600) were prepared at 300 °C, 450 °C, and 600 °C, respectively. The optimal biochar/water ratio was obtained at 1:10. The results indicated that the washing pretreatment can contribute to dramatically increasing the specific surface area of biochars, but slightly increasing their porosity. The washed biochars were carbonaceous microporous materials (67–80% micropore volume), with their specific surface area and porosity being B600 (543 m2/g and 86%), B450 (521 m2/g and 75%), and B300 (188 m2/g and 80%), respectively. The unwashed biochars exhibited a significantly higher ash content (59%–65%) than washed biochars (26%–35%). Equilibrium adsorption study demonstrated that the Langmuir maximum adsorption capacity (Qomax) of crystal violet cationic dye decreased in the following order: unwashed-B450 (1719 mg/g) > washed-B450 (1277 mg/g) > commercial activated carbon (492 mg/g). The washing pretreatment can remove solute-inorganic minerals to prevent their release from biochar during the dye adsorption. The washed biochar with its excellent adsorption capacity can serve as a highly sustainable and industrially viable adsorbent for the removal of cationic dyes from waste bodies.
28072. 题目: Thiothrix eikelboomii Interferes Oxygen Transfer in Activated Sludge
文章编号: N18122101
期刊: Water Research
作者: Xianwei Wu, Ju Huang, Zichuan Lu, Gaofeng Chen, Jianmin Wang, Guoqiang Liu
更新时间: 2018-12-21
摘要: This study revealed that, Thiothrix eikelboomii, a well-known filamentous bacterium that causes sludge bulking, could also interfere oxygen transfer during wastewater treatment. The volumetric oxygen transfer coefficient (KLa) in filamentous-bulking sludge (FBS) was found to be 43% lower than that in floc-forming sludge (FFS) at similar biomass concentrations, partially because the filamentous bacteria had increased the sludge apparent viscosity. The KLa value for FBS, however, was still significantly lower than that for FFS even if both sludges had similar apparent viscosity. Numerous tiny and free-swimming filaments were observed to attach on the air bubble surface, presumably reducing the liquid film renewal and increasing the liquid film thickness. Moreover, the filaments were co-coated with extracellular polymeric substances of protein and polysaccharide, which could make them performing like “amphiphilic molecules” of surfactants to hinder oxygen transfer. Therefore, the particular surface property of filaments and their interaction with air bubbles could also impact oxygen transfer. Thiothrix eikelboomii was identified to be the responsible filamentous bacterium that lowered the KLa value, while other filamentous bacteria with short filaments did not interfere oxygen transfer. This study implies that controlling sludge bulking benefits not only sludge settling but also oxygen transfer.
图文摘要:
28073. 题目: Organic carbon quality, composition of main microbial groups, enzyme activities, and temperature sensitivity of soil respiration of an acid paddy soil treated with biochar
文章编号: N18122023
期刊: Biology and Fertility of Soils
作者: Junhui Chen, De Chen, Qiufang Xu, Jeffry J. Fuhrmann, Lianqing Li, Genxing Pan, Yongfu Li, Hua Qin, Chenfei Liang, Xuan Sun
更新时间: 2018-12-20
摘要: The role of soil organic C (SOC) quality affecting microbial community composition and function under biochar application is poorly understood. We investigated the relationship between the pool size and chemical composition of SOC; composition of main microbial groups; enzyme activities involved in C, N, and P cycling; and soil respiration in a rice paddy amended with biochar for 20 months in a laboratory experiment at 15, 25, and 35 °C. Soil labile and recalcitrant organic C pools were determined by a two-step sulfuric acid (H2SO4) hydrolysis method. The chemical composition of SOC was determined with 13C-nuclear magnetic resonance spectroscopy. The biochar amendment at 20 and 40 t ha−1 significantly decreased the soil labile C pool I (extracted by 5 N H2SO4), alkyl, and carbonyl C contents and increased the recalcitrant C pool (acid-resistant) and aromatic C contents and the aromatic C to O-alkyl C ratio. The phospholipid-fatty acid concentrations and soil enzyme activities were unchanged by biochar application at 10 and 20 t ha−1, but both were increased at 40 t ha−1. Biochar increased the ratio of gram-positive (G+) to gram-negative (G−) bacteria and decreased that of fungi to bacteria. The recalcitrant C pool and aromatic C contents were positively correlated to the G+ bacteria abundance and were important factors in shaping composition of the main microbial groups and improving enzyme activities. Biochar application at 40 t ha−1 lowered soil respiration rates at 15 and 25 °C by decreasing labile C pool and increasing C recalcitrancy while increased temperature sensitivities of soil respiration at 25/15 °C and 35/25 °C by stimulating microbial abundance and enzyme activities. Together, our results suggest that biochar soil amendment shifted microbial community composition and function through influencing the composition of SOC.
28074. 题目: Mercury adsorption to aged biochar and its management in China
文章编号: N18122022
期刊: Environmental Science and Pollution Research
作者: Shiqiu Zhang, Xue Yang, Meiting Ju, Le Liu, Kui Zheng
更新时间: 2018-12-20
摘要: Biochar is frequently applied for the reduction of mercury (Hg) migration in soil; however, most of the studies only focused on the adsorption capacity evaluation of fresh biochar. We investigated the Hg adsorption capacities of biochar prepared from wheat straw, corn straw, and sunflower seed shells. Biochar aging was simulated via natural aging, high-temperature aging, and freeze-thaw aging. The adsorption capacities of all the aged biochar were increased, and wheat straw biochar and seed shells biochar treated with high-temperature aging (wBC-Ha500 and sBC-Ha600) and corn straw biochar treated with freeze-thaw aging (cBC-Fta500) showed an observable improvement on the equilibrium adsorption amounts. The kinetics of the fresh biochar samples fitted the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, while the kinetics of the aged biochar samples fitted the pseudo-second-order kinetic model. Biochar adsorption capacity increased with higher initial concentrations and increasing temperatures. Elemental analysis, Fourier-transform infrared spectroscopy (FT-IR) spectra, cation-exchange capacity (CEC), surface area (SA), zeta potential, and X-ray photoelectron spectroscopy (XPS) showed that the aging mechanism consisted of hydroxylation and carboxylation caused by the functional groups on the biochar surface. According to the different climatic zones in China, wheat straw biochar and seed shell biochar are suitable for the tropical zone and the subtropical zone, while corn straw biochar is more suitable for the cold and the mid-temperate zones.
28075. 题目: Size Dependence of the Physical Characteristics of Particles Containing Refractory Black Carbon in Diesel Vehicle Exhaust
文章编号: N18122021
期刊: Environmental Science & Technology
作者: Chong Han, Shao-Meng Li, Peter Liu, Patrick Lee
更新时间: 2018-12-20
摘要: The number and mass size distributions of refractory black carbon (rBC) cores in particles emitted from a diesel vehicle were investigated as a function of particle mobility diameter (dmob) using a single particle soot photometer (SP2) and a differential mobility analyzer (DMA). The thickness and mass of coatings on the rBC cores were characterized. On the basis of the SP2 and DMA results, the physical properties of particles containing rBC, including effective density (ρeff), mass-mobility scaling exponent (Dm), dynamic shape factor (χ), and mass absorption cross section (MAC), were derived as a function of dmob. At each dmob, the count median diameter (CMD) of the rBC cores was essentially the same as their mass median diameter (MMD), which increased linearly with dmob. The mass of the rBC cores was proportional to the cubic of their dmob. However, coating thickness on rBC cores remained unchanged with dmob, with an average thickness of 28.72 ± 4.81 nm. For particles containing rBC, ρeff decreased and χ increased with dmob. The Dm of particles containing rBC was calculated to be 2.09. At 355 and 532 nm wavelengths, the MAC of the diesel particles containing rBC was inversely dependent on dmob.
图文摘要:
28076. 题目: Aerobic and Anaerobic Bacterial Mercury Uptake is Driven by Algal Organic Matter Composition and Molecular Weight
文章编号: N18122020
期刊: Environmental Science & Technology
作者: Vaughn Mangal, Benjamin R. Stenzler, Alexandre J. Poulain, Celine Guéguen
更新时间: 2018-12-20
摘要: The biological mobilization of mercury (Hg) into microbes capable of Hg methylation is one of the limiting steps in the formation of the neurotoxin methylmercury (MeHg). Although algal dissolved organic matter (DOM) has been associated with increased MeHg production, the relationship between bacterial Hg uptake and algal DOM remains unexplored. In this study, we aimed to address how the quantity and quality of DOM, freshly harvested from several algae, affected the bacterial uptake of Hg with the use of a biosensor capable of functioning both aerobically and anaerobically. We combined biosensor measurements with high-resolution mass spectrometry and field-flow fractionation to elucidate how DOM composition and molecular weight influenced microbial Hg uptake. We showed that freshly harvested DOM from Chlorophyte and Euglena mutabilis strongly inhibited aerobic and anaerobic Hg uptake, whereas DOM harvested from Euglena gracilis did not exhibit this same pronounced effect. Once fractionated, we found that amino acids and polyamines, most abundant in Euglena gracilis DOM, were positively correlated to increase Hg uptake, suggesting that these molecules are potentially underappreciated ligands affecting Hg bioavailability. As water quality is affected by eutrophication, algal community assemblages will change, leading to variations in the nature of autochthonous DOM released in aquatic systems. Our results highlight that variations in the emergent properties of DOM originating from varying algal species can have a profound effect on bacterial Hg uptake and thus methylation.
图文摘要:
28077. 题目: Effect of light intensity on the characteristics of algal-bacterial granular sludge and the role of N-acyl-homoserine lactone in the granulation
文章编号: N18122019
期刊: Science of The Total Environment
作者: Bing Zhang, Yuan Guo, Piet N.L. Lens, Zhiqiang Zhang, Wenxin Shi, Fuyi Cui, Joo Hwa Tay
更新时间: 2018-12-20
摘要: The effects of light intensity on the development of algal-bacterial granular sludge (ABGS) were investigated over a period of 12 weeks. The ABGS developed at low light intensity (142 ± 10 μmol m−2·s−1) exhibited excellent settling ability (SVI30 of 30.9 mL/g), COD and TN removal efficiencies (97.6% and 60.4%, respectively). High light intensity (316 ± 12 μmol m−2·s−1) accelerated granular biomass growth (5.3 g/L) and enhanced the TP removal efficiency (83.7%). Extracellular polymeric substance (EPS) analysis revealed that low light intensity induced more large weight distribution protein production (9–12 kDa and 50–150 kDa), predominantly tryptophan and aromatic proteins. Furthermore, N-acyl-homoserine lactones (AHLs) with a side chain ≤ C10 were commonly shared in the ABGS, and the ABGS developed at low light intensity had a higher C6- and 3OC8-HSL content, which effectively promoted the biofilm formation. The add-back studies showed that the AHLs facilitated the regulation of EPS synthesis. Statistical analysis indicated that the AHLs content had a close correlation with the EPS production, the 50th percentile of the particle size distribution and microbial community assembly, suggesting that AHLs-mediated quorum sensing have an important ecological role in EPS expression and algal-bacterial granulation. Overall, this study describes the ABGS development at different light intensities and the mechanisms of ABGS formation treating synthetic domestic wastewater.
图文摘要:
28078. 题目: Colloidal stability and aggregation kinetics of biochar colloids: Effects of pyrolysis temperature, cation type, and humic acid concentrations
文章编号: N18122018
期刊: Science of The Total Environment
作者: Wen Yang, Jianying Shang, Prabhakar Sharma, Baoguo Li, Kesi Liu, Markus Flury
更新时间: 2018-12-20
摘要: An understanding of biochar colloid aggregation and stability in aqueous environments is critical for assessing biochar fate and mobility in the soil. The aggregation kinetics of wheat straw-derived biochar colloids pyrolyzed at two temperatures 300 and 600 °C (WB300 and WB600 colloids, respectively) were investigated in monovalent and divalent electrolyte solutions in absence/presence of humic acid (HA). Results show that the critical coagulation concentrations (CCCs) of WB300 colloids in NaCl and CaCl2 solutions were 274 and 61.4 mM, which were higher than those (183 mM for NaCl and 38.1 mM for CaCl2) of WB600 colloids. WB300 had more oxygen-containing functional groups than WB600, which induced more negative surface charge on WB300. HA of 5 mg L−1 greatly increased the CCCs of WB300 and WB600 colloids to 1288 and 806 mM in NaCl solutions, but decreased the CCCs to 54.6 and 37.0 mM in CaCl2 solutions because of strong bridging between HA and Ca2+. In CaCl2 solutions with high salt concentrations (near to the CCCs), different HA concentrations caused distinct effects on the aggregation of biochar colloids. The aggregation of biochar colloids was accelerated by HA with the concentration higher than 5 mg L−1 through cation-bridging while the aggregation was inhibited in the presence of <2.5 mg L−1 HA. Our findings show that pyrolysis temperature used for biochar production had a large effect on the aggregation of biochar colloids in the aqueous environment and that cation type and dissolved natural organic matter are controlling variables.
图文摘要:
28079. 题目: Carbon input and the structural quality of soil organic matter as a function of agricultural management in a tropical climate region of Brazil
文章编号: N18122017
期刊: Science of The Total Environment
作者: Shirlei Almeida Assunção, Marcos Gervasio Pereira, Jean Sérgio Rosset, Ricardo Luiz Louro Berbara, Andrés Calderín García
更新时间: 2018-12-20
摘要: Carbon (C) stabilization and the quality of soil organic matter (SOM) in a tropical climate are key aspects regulating carbon dioxide emissions and maintaining the C cycle. Soil management influences the accumulation of C, regulating the balance between mineralization and/or the humification of SOM. This study aimed to quantify inputs of different chemical forms of C into soil and to evaluate the structural chemical characteristics of humified SOM. Four management systems were established: Forest (F), Pasture (P), Conventional tillage (T), and No-tillage (NT). Total organic carbon (TOC) and nitrogen (TN) by depth, chemical forms of organic matter input, and spectroscopic characterization of SOM in the form of humic acids (HA) were analyzed. The results obtaining by PCA-13C NMR show that the forest accumulated a high amount of C on the surface (surpassing 20 Mg ha−1), favoring the formation of aliphatic HA (CAlkyl-H,R; CAlkyl-O,N; CAlkyl-O). In the NT management that increases biomass in the soil (14 Mg ha−1), the mineralization process occurred to a greater extent, allowing HA to form with a predominance of aromatic structures (CArm-H,R and CArm-O,N). The PCA-FTIR analysis showed that the P system contributed to the formation of similar HA to those under F management. The T management system incorporated the least TOC and TN, with different HA types being formed in these soils than what was found in other managements. Thus, minimally managed and more stabilized systems in tropical climates form HA of structural and compositional similarity, regardless of the nature of C (C3 or C4). In contrast, soils subjected to agricultural uses that promote higher or lower C inputs, form HA that are structurally different from P and F. This study demonstrates the need for developing experiments for model building to elucidate the relationships among C input, management type, and the formation of humic substances.
图文摘要:
28080. 题目: Tracing the sources of nitrate in the rivers and lakes of the southern areas of the Tibetan Plateau using dual nitrate isotopes
文章编号: N18122016
期刊: Science of The Total Environment
作者: Mingming Hu, Yuchun Wang, Pengcheng Du, Yong Shui, Aimin Cai, Cong Lv, Yufei Bao, Yanhui Li, Shanze Li, Panwei Zhang
更新时间: 2018-12-20
摘要: Based on a quantitative analysis of nitrate concentrations, the nitrate sources and temporal variability of the rivers, lakes, and wetlands of Tibet were assessed for the first time using dual isotope technology. Water samples were collected once in July 2017 for analysis of nitrate concentration and isotopic composition. The overall values of δ15N-NO3− and δ18O-NO3− ranged from +1.8‰ to +23.0‰, and from −6.3‰ to +22.2‰ respectively. Duel isotopic composition suggested that nitrification of soil organic nitrogen was the main source of nitrate in the Yalu Tsangpo River. Furthermore, anthropogenic nitrogen inputs become more important in downstream than upstream because of intensive agricultural activities and urban input. In the rivers of the Ngari District, nitrate is mainly derived from desert deposits, manure and sewage, and chemical fertilisers. Different rivers show different characteristics of nitrate sources depending on the location, topography, landform, and climate of the river basins. Animal manure, nitrification of soil organic matter, and desert deposits are mainly responsible for the shifting of nitrate isotopic signatures in lakes, which are minimally affected by human activities. In wetlands, biological nitrification and denitrification could be the main processes of nitrogen migration and transformation. These results provide useful information in revealing the fate of nitrate in different aquatic ecosystems and different areas of Tibet.
图文摘要:
