8181. 题目: Duxite - fossil resin of Miocene age
期刊: Organic Geochemistry
作者: Martina Havelcová, Vladimír Machovič, Ivana Sýkorová, Ladislav Lapčák, Alexandra Špaldoňová, Karel Mach, Zdeněk Dvořák
摘要: A series of Miocene fossil resin from the northwest part of the Czech Republic, called duxite, has been analyzed by elemental, microscopic, gas chromatography (GC/MS), pyrolysis-gas chromatography, Fourier Transform infrared (FTIR), and Raman techniques. The set of samples consisted of museum, contemporary and artificially altered samples. The results of GC/MS revealed fine variances in chemical structure among the samples, which could be attributed to the geologic paleosituation during resin deposition, as was verified by alteration of a sample under different conditions. Sesquiterpenes, including α-cedrene and cuparene, were identified in sample extracts and sample pyrolysates together with diterpenoid members abietanes, pimaranes, and dehydroabietanes. The distribution and intensity of functional groups of FTIR spectra also confirmed that the duxite samples were fossilised exudates from a member of the Cupressaceae conifer family. Raman spectra supported this record indicating aromatic character of duxite and higher maturity of the samples.. The chemical composition indicated that duxite is a member of Class IV resins of the fossil resin classification system. Members of this group do not have a polymeric structure. This nonpolymerizable behaviour was confirmed by their excellent solubility in an organic solvent and the low softening point of the material. Our results therefore provide a valuable insight into the duxite-producing process and its potential for evaluating the geological environment and diagenetic conditions.
8182. 题目: Influence of biochars on the accessibility of organochlorine pesticides and microbial community in contaminated soils
期刊: Science of The Total Environment
作者: Neelum Ali, Sardar Khan, Yaying Li, Ningguo Zheng, Huaiying Yao
摘要: Biochar can be used as a promising potential substance to reduce the availability of toxic elements and compounds in contaminated soils but its effects on the accessibility of pesticides and microbiological interactions still remain unclear. Here, 65 day incubation experiments were conducted to investigate the efficacy of biochars on the accessibility of 21 different organochlorine pesticides (OCPs), and also to evaluate their influence on soil microbial community. The tested soil was collected from an agricultural field, containing loamy sand texture, and historically contaminated with high concentrations of OCPs. The soil was amended with four different kinds of biochars: sewage sludge biochar (SSBC), peanut shells biochar (PNBC), rice straw biochar (RSBC), and soybean straw biochar (SBBC). The results indicated that biochar-amendments had strong effects upon OCP accessibility over time and can act as super sorbent. Despite greater persistence of OCPs in soil, the application of selected biochars significantly (p < 0.01) reduced the accessibility of ∑OCPs in the amended soil in the order of SSBC (8–69%), PNBC (11–75%), RSBC (6–67%), and SBBC (14–86%), as compared to the control soil during 0–65 d incubation period. Moreover, the findings from total phospholipid acid (PLFA) and Illumina next-generation sequencing revealed that the incorporation of biochar have altered the soil microbial community structure over time. Higher abundances of Proteobacteria, firmicutes, Gemmatimonadetes, and Actinobacteria were found in biochar amendments. However, the relative abundances of Acidobacteria and Chloroflexi decreased, following biochar addition. The findings of these experiments suggest that biochar addition to soil at the rate of 3% (w/w) could be advantageous for decreasing accessibility of OCPs, enhancing the soil microbial communities, and their subsequent risk to environment and food chain contamination.
8183. 题目: The use of calcium carbonate-enriched clay minerals and diammonium phosphate as novel immobilization agents for mercury remediation: Spectral investigations and field applications
期刊: Science of The Total Environment
作者: Jianxu Wang, Ying Xing, Yuanyan Xie, Yong Meng, Jicheng Xia, Xinbin Feng
摘要: We used calcium carbonate-enriched clay minerals (CECM) and diammonium phosphate (DAP) as immobilization agents for mercury (Hg) immobilization. The effects of CECM, DAP, or both in different amounts and ratios, as well as pH and initial Hg concentrations, on Hg removal from solutions were investigated. The removal mechanism was revealed using transmission electron microscope with energy-dispersive X-ray (TEM-EDX) spectroscopy, and extended X-ray absorption fine structure spectroscopy (EXAFS). The performance of CECM and DAP under field conditions was also studied. The results showed that application of CECM and DAP at a ratio of 50:1 (w/w) removed over 90% of Hg from solutions containing 1.8 μM Hg2+, which was 9- or 2.6-fold higher than solely DAP (<10%) or CECM (34%<), respectively. Mercury removal by CECM and DAP was weakly affected by pH values between 4 and 10, and their maximum Hg removal capacity was 37 mg g−1. Both TEM-EDX and EXAFS results showed that the precipitate of Hg with phosphorus-associated minerals might be the primary mechanism of Hg removal by CECM and DAP. Results from the field trial showed that application of CECM and DAP decreased soil bioavailable Hg contents, but did not affect contents of organic matter bound Hg or residual Hg fractions, as compared with control and initial soils. Application of CECM and DAP resulted in dramatic reductions (40%–53%) of Hg in the edible tissues of Brassica chinensis and Raphanus raphanistrum in comparison to the non-treated control. We conclude that CECM and DAP offer a promising method for in situ remediation of Hg-contaminated farmlands in southwest of China.
8184. 题目: Influence of consecutive integrated rice-crayfish culture on phosphorus fertility of paddy soils
期刊: Land Degradation & Development
作者: Qingman Li, Lei Xu, Lijing Xu, Yiguang Qian, Yang Jiao, Yonghong Bi, Tanglin Zhang, Wen Zhang, Yanjie Liu
摘要: China has experienced an increase in integrated rice‐crayfish (Procambarus clarkii) culture (IRCC) in rice paddies. However, whether the current regime degrades phosphorus (P) fertility in rice paddies remains unclear. To assess changes in P fertility, the surface soil (0‐20cm) of high‐yield rice paddies with 3, 6 and 10 consecutive years of IRCC were sampled in Honghu County in the Jianghan Plain region, China. Adjacent fields planted with long‐term rotations of rice and dry‐season crops (RRD) were also sampled. Total P (TP), available P (Pa), organic P (Po) compounds and P fractions in soils were intensively assessed using chemical digestion, NaHCO3 extraction, 31P nuclear magnetic resonance (31PNMR) and sequential chemical extraction (SEDEX). IRCC significantly increased organic matter, total nitrogen, TP, Fe (II) and S2− contents of rice paddy soils and nutrient concentrations in in the surface water, with a distinct decrease in total Fe and pH. Consecutive IRCC greatly influenced P fertility. Continuous P accumulation in paddy soils accelerated greatly, with a mean increase of ca. 43 mg·kg−1·y −1. Compared to RRD, Pa was 67% higher after 3 years of IRCC but 78% lower after 10 years. Consecutive IRCC induced a decrease in Po compounds, with a mean decrease in TPo of ca. 20 mg·kg−1·y−1. Long‐term consecutive IRCC increased transformation of Pa, Fe (II)‐P and Po into Ca‐P and Fe (III)‐P, increasing mean Ca‐P and Fe (III)‐P concentrations by ca. 69 and 7 mg·kg−1·y−1, respectively. Our results suggested that long‐term consecutive IRCC degrades P fertility in rice paddies, and implementing IRCC in high‐yield rice paddies is not recommended.
8185. 题目: Phenanthrene adsorption on soils from the Yangtze River Delta region under different pH and temperature conditions
期刊: Environmental Geochemistry and Health
作者: Lifeng Ping, Yongming Luo
摘要: The phenanthrene (PHE) adsorption on soils from the Yangtze River Delta region under different pH and temperature conditions was studied in the laboratory. Results showed that the sorption of PHE on all soils was nonlinear and fitted to the Freundlich isotherm. The PHE adsorption on the soils is related to the content of organic carbons and the environmental conditions. There was a positive correlation (the correlation coefficient was 0.956) between the PHE adsorption and the soil organic carbon content. Adsorption on the soils at 15 °C ambient temperature was higher than at 25 °C, which was related to PHE solubility enthalpy. Adsorption on the soils in background solution at pH 5.0 was higher than in those at pH 6.2 and 7.5, which may be related to alteration of the hydrophobic character of humic substances. This study showed that intrinsic organic carbons influenced the adsorption of PHE, which was affected by environmental conditions, such as pH and temperature. Therefore, the characteristics of soil organic carbon should be considered first for implementing effective schemes for the remediation of contaminated soils and in the formulation of soil environmental quality standards.
8186. 题目: Soil Conditions Following Hydrologic Restoration in Cypress Dome Wetlands
作者: Megan K. Bartholomew, Christopher J. Anderson, Jacob Berkowitz
摘要: Soil characteristics and decomposition rates were investigated in 12 geographically isolated wetlands (cypress domes) across a gradient of hydrologic alteration (altered, marginally altered and least altered sites) seven years after passive recovery from historic groundwater withdrawals. Above- and belowground decomposition rates were determined in transition (seasonally flooded) and outer deep (semi-permanently) hydrologic zones. Flood duration, frequency, redox conditions, pH, and soil organic matter were measured to potentially explain patterns across the alteration gradient. Despite the reduction in groundwater withdrawals, altered sites exhibited fewer days of inundation in transition and outer deep zones compared to marginally altered and least altered wetlands. Over a 56 week period, altered wetlands displayed greater decomposition in the aboveground outer deep zone (73.3 ± 4.0% mass remaining) and in the belowground transition zone (62.0 ± 4.5% mass remaining) compared to marginally and least altered sites. Analyses indicated that marginally altered wetlands were more comparable to least altered wetlands however differences in altered wetland soils (including decomposition) persist. Although wetland hydrology has been partially restored, additional time and/or further site augmentation may be needed for altered sites to be functionally equivalent to least altered wetlands and in some cases (e.g., excessive subsidence) the degree of past alteration may limit restoration potential.
8187. 题目: Improved methane production from waste activated sludge by combining free ammonia with heat pretreatment: Performance, mechanisms and applications
期刊: Bioresource Technology
作者: Xuran Liu, Qiuxiang Xu, Dongbo Wang, Jianwei Zhao, Yanxin Wu, Yiwen Liu, Bing-Jie Ni, Qilin Wang, Guangming Zeng, Xiaoming Li, Qi Yang
摘要: Anaerobic digestion of waste activated sludge (WAS) is often limited by low hydrolysis efficiencies and poor methane potentials. This work presents a novel pretreatment technology for WAS anaerobic digestion, i.e., combining free ammonia with heat pretreatment (CFHP). Experimental results showed that compared with control, solo free ammonia (135.4 mg NH3-N/L) and solo heat (70 °C) pretreatment, the combined free ammonia and heat (135.4 mg NH3-N/L with 70 °C) obtained 52.2%, 25.5% and 30.2% faster in hydrolysis rate and 25.2%, 17.9% and 16.5% higher in biochemical methane potential, respectively. Mechanism investigations showed that the combined pretreatment not only largely facilitated the disintegration of WAS but also increased the proportion of biodegradable organic matters, thereby providing better contract between biodegradable organics and the anaerobic microbes for methane production. Considering its effectiveness and renewability, the combined pretreatment is an attractive technology for the application in real-world situations.
8188. 题目: A microscopic simulation of particle flux in ocean waters: application to radioactive pair disequilibrium
期刊: Geochimica et Cosmochimica Acta
作者: F. De Soto, E. Ceballos-Romero, M. Villa-Alfageme
摘要: The biological carbon pump, a fundamental component of the global carbon cycle, is a mechanism comprised of biological processes that transfer large amounts of organic carbon from the upper ocean to the ocean’s interior. It sequesters CO2 for weeks to hundreds or even millions of years through the sinking of a complex mix of biogeo-chemical material. As particles sink the flux of particulate organic carbon attenuates and only a fraction of the flux reaches the ocean’s depth. Quantifying the attenuation of sinking particulate carbon flux is key to assess the amount of carbon sequestered in the twilight zone. Current knowledge of the particle flux attenuation relies on a reduced number of direct measurements, usually fitted to a power law, that tries to describe the result of a large variety of biological, physical and chemical processes involved. We present a stochastic simulation for particle production, sinking and degradation in the oceans that includes most of the essential ingredients to ultimately describe the sinking carbon flux in the ocean and where all the complex biogeochemical behavior is captured by macroscopic parameters. The algorithm proposed interprets these phenomena probabilistically and is an ideal framework to describe the observed patterns of particle flux attenuation in depth. Particles are randomly produced and degraded with depth-dependent functions, which reproduces the variability of these processes in nature. Hence, the simulation proposed provides a suitable approach to analyse sinking carbon when different particle sizes or speeds are used. Furthermore, production and degradation phenomena are time-dependent, this way their seasonal evolution can be additionally explored and the simulation results in an ideal test-bed for the assessment of both steady and non-steady state situations. In addition, the theoretical formulation proposed provides a simple frame to include particle-metals interactions through adsorption and desorption processes. In this paper we relate typical parametrizations of the flux attenuation curve to their corresponding degradation rate and propose an alternative parametrization to model the flux degradation function which is negligible at very large depths, therefore producing a constant residual flux, and remains finite in the euphotic zone. This degradation function is implemented in the simulation and applied to estimate the scavenging of the naturally occurring radioisotopes 234Th and 210Po. We use the results to estimate effective adsorption and desorption rate constants for both isotopes. We found that the degradation rate, rather than the half-life, controls the depth at which the parent and daughter reach equilibrium. Thus, this depth is ruled by a combination of the degradation rate and the particle sinking velocity.
8189. 题目: Biomarker signatures of the iconic Glossopteris plant
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Anuradha Tewari, Ashalata D'Rozario, Sharmila Bhattacharya, Ahinsuk Barua, Meghma Bera, Subir Bera, Suryendu Dutta
摘要: Glossopteris is the quintessential marker plant that dominated the forests of the Southern Hemisphere continents during the Permian before their abrupt extinction at the close of the Palaeozoic. Fossilized leaf and stem remains of Glossopteris plants, collected from the Permian succession of eastern India, were analysed to recognize the molecular signatures of solvent-extractable and non-extractable organic matter. Lipid-derived aliphatic and aromatic biomarkers were studied using GC–MS and GC × GC-TOFMS, while tetramethylammonium hydroxide (TMAH) thermochemolysis with GC–MS and GC × GC-TOFMS was used to reveal lignin precursors. The thermal maturity indices indicate low thermal rank for both samples. The presence of aromatic diterpanes in the leaf extract suggests that the Glossopteris plant was able to biosynthesize abietic acid and related plant terpenoids. The thermochemolysis products (thermochemolysates) of the samples contain monomethoxy-, and dimethoxybenzene derivatives produced from p‑hydroxyphenyl and guaiacyl units of lignin, respectively, which are the main constituents of extant gymnosperm lignin. The thermochemolysates indicate that lignin biosynthesis had evolved in Glossopteris.
8190. 题目: Interrelationship of biomass yield, carbon input, aggregation, carbon pools and its sequestration in Vertisols under long-term sorghum-wheat cropping system in semi-arid tropics
期刊: Soil and Tillage Research
作者: Ashim Datta, Biswapati Mandal, Shrikant Badole, Krishna Chaitanya A., S.P. Majumder, Dhaneshwar Padhan, Nirmalendu Basak, Arijit Barman, Ritesh Kundu, W.N. Narkhede
摘要: We investigated dynamics of soil organic carbon (SOC) i.e. total soil organic carbon (TOC), oxidisable organic carbon (OC) and its different pools viz. very labile (CVL), labile (CL), less labile (CLL) and non-labile (CNL), and various sized aggregate associated carbon (AAC) and also its sequestration along depth (0-0.15, 0.15-0.30, and 0.30 -0.45 m) in a typical Vertisols under hot semi-arid agro-climatic conditions. Such dynamics were studied under different soil management practices viz., control, NPK (100% recommended doses of N, P and K fertilizers, RDF), NPK + FYM (50% N and whole of the RDF and 50% N through FYM) and fallow using a 28 year old long-term experiment with sorghum (Sorghum bicolour L.) – wheat (Triticum aestivum L.) cropping system. On average, a higher proportion (70% of TOC) of SOC was found in passive pool (less labile + non labile) than active one (very labile + labile) throughout the profile. The proportion of active pool was, however, higher under balanced (NPK) and integrated nutrient management practices (NPK + FYM) over the others followed. Long-term intensive cropping with NPK (15.1%) and NPK + FYM (22%) caused a net enrichment in SOC stock over the control. To offset the loss of C and maintain the SOC level, a critical amount of 0.96 Mg C ha−1yr−1 was needed to be incorporated into the soil. Out of the total water stable aggregates (WSA), mesoaggregates (0.25–2.0 mm) predominated (73.6%) followed by micro (16.4%), and macroaggregates (10.7%) at surface soil. Amount of carbon associated with different sized aggregates had the following trend: mesoaggregate (52.3%) > coarse microaggregate (13.7%)> coarse macroaggregate (13.5%)> (silt + clay) sized aggregate (13.1%)> fine microaggregate (12.2%). Balanced fertilization with organics thus provided not only higher yield but also increased C sequestration in Vertisols even with intensive cropping of sorghum-wheat system under hot semi-arid conditions.
8191. 题目: Microbial diversity associated to the intestinal tract of soil invertebrates
期刊: Applied Soil Ecology
作者: Dayana da Silva Correia, Samuel Ribeiro Passos, Diogo Neves Proença, Paula Vasconcelos Morais, Gustavo Ribeiro Xavier, Maria Elizabeth Fernandes Correia
摘要: Interactions between saprophagous invertebrates and microbes are essential for the maintenance and functioning of soil ecosystems, as they directly affect the degradation of organic matter and the nutrient cycle. The intestinal tract of invertebrates is inhabited by a diversity of microbes, and it is closely associated with the food ingested. The aim of this work was to evaluate the profile of prokaryotes associated with the intestinal tract of three invertebrate species. The species of invertebrates Trigoniulus corallinus was collected and incubated in the experiment, after 5 days of incubation we observed the uninduced colonization of two invertebrate species Cubaris murina and Pycnoscelus surinamensis. Therefore, the three species were evaluated in the same way, after 60 days of incubation. The diet supplied comprised different vegetal residues, with distinct carbon/nitrogen compositions. Six treatments were evaluated. After 60 days, five individuals of each species were randomly selected, by removing the posterior third of the intestinal tract. These specimens were next subjected to DNA extraction. The PCR/DGGE analysis was carried out using the 16S rDNA, for the domain Bacteria and the phylum Actinobacteria. DGGE bands were cloned and sequenced using the Bacterial domain. In multivariate analyzes, individuals of the same species after 60 days of incubation, were strongly grouped. These results may be in accordance with the environmental criteria of the host itself, stage of development, phylogeny and diet. Thus, the investigation of the intestinal microbiota, provides relationships between invertebrates and their intestinal bacterial communities. In view of this information, we used the technique of sequencing cloned DGGE bands to quantify the diversity of microorganisms present in the intestinal tract of the studied invertebrates. The phylum Firmicutes, Bacteroidetes, and Proteobacteria were identified by sequencing the cloned bands; Proteobacteria presented the highest number of genera, comprising Enterobacter, Buttiauxella, Serratia, Kluyvera, and Pantoea.
8192. 题目: Iron isotope pathways in the boreal landscape: role of the riparian zone
期刊: Geochimica et Cosmochimica Acta
作者: Johan Ingri, Sarah Conrad, Fredrik Lidman, Fredrik Nordblad, Emma Engström, Ilia Rodushkin, Don Porcelli
摘要: Stable Fe isotope compositions have been measured in water samples of the subarctic Kalix River, a first-order stream, and soil water samples from a riparian soil profile adjacent to the first-order stream (Northern Sweden). In the first-order stream, dominated by forest, both the particulate (>0.22µm) and dissolved (< 0.22µm) phase showed negative δ56Fe values (relative to IRMM-14) during base flow and meltwater discharge in May (-0.97 to -0.09‰). The Fe isotope composition in the water from the riparian soil profile varied between -0.20 and +0.91‰ with sharp gradients near the groundwater table. A linear correlation between the δ56Fe values and the TOC/Febulk ratio was measured during snowmelt in the unfiltered river waters (δ56Fe from -0.02 to +0.54‰), suggesting mixing of two Fe components. Two groups of Fe aggregates, with different Fe isotope compositions, are formed in the boreal landscape. We propose that carbon-rich aggregates, Fe(II)(III)-OC, have negative δ56Fe values and Fe-oxyhydroxides have positive δ56Fe values. A mixture of these two components can explain temporal variations of the Fe isotope composition in the Kalix River. This study suggests that stable Fe isotopes can be used as a tool to track and characterize suspended Fe-organic carbon aggregates during transport from the soil, via first-order streams and rivers, to coastal sediment. Furthermore, the differences in Fe isotope values in the Kalix River and the first-order stream during base flow conditions suggest that the primary Fe sources for river water change throughout the year. This model is combining the Fe isotope composition of first-order streams and rivers to weathering and transport processes in the riparian soil.
8193. 题目: Pathways of inorganic and organic contaminants from land to deep sea: The case study of the Gulf of Cagliari (W Tyrrhenian Sea)
期刊: Science of The Total Environment
作者: Stella Tamburrino, Salvatore Passaro, Mattia Barsanti, Antonio Schirone, Ivana Delbono, Fabio Conte, Roberta Delfanti, Maria Bonsignore, Marianna Del Core, Serena Gherardi, Mario Sprovieri
摘要: In continental margins, canyons appear to act as natural conduits of sediments and organic matter from the shelf to deep basins, providing an efficient physical pathway for transport and accumulation of particles with their associated land-produced contaminants. However, these mechanisms have not been yet sufficiently explored by geochemical markers. The continental slope of the south Sardinia has been used as a natural laboratory for investigating mechanisms and times of transfer dynamics of contaminants from land to sea and from shelf to deep sea through an articulated system of submarine canyons. Here, dynamics of contaminants have been investigated in a pilot area of the central Mediterranean basin (Gulf of Cagliari, S Sardinia) where important industrial plants are sited since beginning of the last century. Five sediment cores dated by 210Pb and 137Cs reveal: i) a complex dynamics of organic and inorganic contaminants from point source areas on land to the deep sea and ii) a crucial role played by canyons and bottom morphology as primary pathway conveying sediments and associated contaminants from sources to very far deep sea environments. In particular, this study provides new integrated tools to properly understand mechanisms of connection between coastal sectors and deep sea. This is challenging mostly in regions where coastal pollution could represent critical threats for larger areas of the Mediterranean Sea.
8194. 题目: Investigating the use of synthetic humic-like acid as a soil washing treatment for metal contaminated soil
期刊: Science of The Total Environment
作者: Ting Yang, Mark E. Hodson
摘要: Humic acid can effectively bind several metals and is regarded as a promising soil washing agent. Previous studies indicate that carboxylic groups dominate metal binding to humic acid. In this study, a synthetic humic-like acid (SHLA) with high COOH content (5.03 mmol/g) was used as a washing agent to remove metals (Cu, Zn, Ni, Pb, As) from two contaminated agricultural soils (Soil 1 (pH: 6.17 ± 0.11; organic carbon: 5.91 ± 0.40%; Cu: 302.86 ± 3.97 mg/kg; Zn: 700.45 ± 14.30 mg/kg; Pb 323.56 ± 4.84 mg/kg; Ni: 140.16 ± 1.59 mg/kg) and Soil 2 (pH: 9.83 ± 0.01; organic carbon: 2.52% ± 0.25%; Cu: 242.81 ± 10.66 mg/kg; Zn: 841.00 ± 22.31 mg/kg, Pb 451.21 ± 1,92 mg/kg, As: 242.23 ± 5.24 mg/kg)). The effects of solution pH (4 to 11), liquid/solid ratio (L/S ratio, 5:1 (mL:g) to 80:1 (mL:g)), SHLA concentration (100 mg/L to 2000 mg/L), and contact time (0 to 1440 min) on % metal removal were investigated and optimum conditions identified: pH of 9, L/S ratio of 1:80, SHLA concentration of 1500 mg/L at 25 °C for 4 h. Under optimum conditions, a single washing removed 45.2% of Cu, 34.6% of Zn. 42.2% of Ni and 15.6% of Pb from Soil 1, and 30.6% of Cu, 28.1% of Zn. 14.6% of As and 18.1% of Pb from Soil 2. A modified BCR extraction of the two soils before and after washing indicated that the SHLA mainly removed metals in the exchangeable and acid soluble fraction and reducible fraction, which could effectively reduce bioavailability and environmental risk of metals. On a molar basis, SHLA was a more effective washing agent than commercial humic acid, Na2EDTA, citric acid and tartaric acid. Overall, SHLA shows great potential for use as a soil washing agent.
8195. 题目: Cellular and non-cellular mineralization of organic carbon in soils with contrasted physicochemical properties
期刊: Soil Biology and Biochemistry
作者: Benoit Kéraval, Sébastien Fontaine, Audrey Lallement, Sandrine Revaillot, Hermine Billard, Gaël Alvarez, Fernando Maestre, Christian Amblard, Anne-Catherine Lehours
摘要: It has been recently demonstrated that soil organic carbon (SOC) mineralization is supported by intracellular respiration of heterotrophic microorganisms and by non-cellular oxidative processes. However, little is known about the prevalence and drivers of non-cellular SOC mineralization among soils. In this study, untreated and gamma-irradiated soils sampled along a latitudinal gradient and exhibiting contrasted physicochemical properties were incubated in order to quantify potential non-cellular SOC mineralization and to identify its sensibility to soil properties. In sterilized and unsterilized soils, CO2 emission mirrored O2 consumption signifying the presence of several coupled redox reactions transferring electrons from organic C to intermediate acceptors and to O2. This supports the idea that non-cellular mineralization results from extracellular oxidative metabolisms catalyzed by soil enzymes and/or abiotic catalysts. Our findings also show that non-cellular SOC mineralization is ubiquitous and contributes to 24% of soil respiration on average. Cellular and non-cellular SOC mineralization are positively linked but the contribution of non-cellular processes to soil CO2 emissions increases with dissolved organic carbon concentration.
8196. 题目: Abatement of 2,4-D by H2O2 solar photolysis and solar photo-Fenton-like process with minute Fe(III) concentrations
期刊: Water Research
作者: Anna Serra-Clusellas, Laura De Angelis, Chung-Ho Lin, Phuc Vo, Mohamed Bayati, Lloyd Sumner, Zhentian Lei, Nathalia B. Amaral, Liliana M. Bertini, Jose Mazza, Luis R. Pizzio, Jorge D. Stripeikis, Julián A. Rengifo-Herrera, María M. Fidalgo de Cortalezzi
摘要: The Photo-Fenton-like (PF-like) process with minute Fe(III) concentrations and the Hydrogen Peroxide Photolysis (HPP), using Xe-lamp or solar light as sources of irradiation, were efficiently applied to eliminate the herbicide 2,4-D from water. PF-like experiments concerning ferric and H2O2 concentrations of 0.6 mg L−1 and 20 mg L−1 respectively, using Xenon lamps (Xe-lamps) as a source of irradiation and 2,4-D concentrations of 10 mg L−1 at pH 3.6, exhibited complete 2,4-D degradation and 77% dissolved organic carbon (DOC) removal after 30 min and 6 h of irradiation respectively whereas HPP (in absence of ferric ions) experiments showed a 2,4-D reduction and DOC removal of 90% and 7% respectively after 6 h of irradiation. At pH 7.0, HPP process achieved a 2,4-D abatement of approximately 75% and a DOC removal of 4% after 6 h. PF-like exhibited slightly improved 2,4-D and DOC removals (80% and 12% respectively) after the same irradiation time probably due to the low pH reduction (from 7.0 to 5.6). Several chlorinated-aromatic intermediates were identified by HPLC-MS. These by-products were efficiently removed by PF at pH 3.6, whereas at neutral PF-like and acid or neutral HPP, they were not efficiently degraded. With natural solar light irradiation, 10 and 1 mg L−1 of 2,4-D were abated using minor H2O2 concentrations (3, 6, 10 and 20 mg L−1) and iron at 0.6 mg L−1 in Milli-Q water. Similar results to Xe-lamp experiments were obtained, where solar UV-B + A light H2O2 photolysis (HPSP) and solar photo-Fenton-like (SPF-like) played an important role and even at low H2O2 and ferric concentrations of 3 and 0.6 mg L−1 respectively, 2,4-D was efficiently removed at pH 3.6. Simulated surface water at pH 3.6 containing 1 mg L−1 2,4-D, 20 mg L−1 H2O2 and 0.6 mg L−1 Fe(III) under natural sunlight irradiation efficiently removed the herbicide and its main metabolite 2,4-DCP after 30 min of treatment while at neutral pH, 40% of herbicide degradation was achieved. In the case of very low iron concentrations (0.05 mg L−1) at acid pH, 150 min of solar treatment was required to remove 2,4-D.
8197. 题目: Singlet Oxygen Phosphorescence as a Probe for Triplet-State Dissolved Organic Matter Reactivity
期刊: Environmental Science & Technology
作者: Paul R. Erickson, Kyle J. Moor, Jeffrey J. Werner, Douglas E. Latch, William A. Arnold, Kristopher McNeill
摘要: Triplet-state chromophoric dissolved organic matter (3CDOM*) plays an important role in aquatic photochemistry, yet much remains unknown about the reactivity of these intermediates. To better understand the kinetic behavior and reactivity of 3CDOM*, we have developed an indirect observation method based on monitoring time-resolved singlet oxygen (1O2) phosphorescence kinetics. The underpinning principle of our approach relies on the fact that O2 quenches almost all triplets with near diffusion limited rate constants, resulting in the formation of 1O2, which is kinetically linked to the precursors. A kinetic model relating 1O2 phosphorescence kinetics to triplet excited states produced from isolated humic substances and in whole natural-water samples (hereafter referred to as 3CDOM*) was developed and used to determine rate constants governing 3CDOM* natural lifetimes and quenching by oxygen and 2,4,6-trimethylphenol (TMP), a common triplet probe molecule. 3CDOM* was found to exhibit smaller O2 and TMP quenching rate constants, ∼9 × 108 and ∼8 × 108 M–1 s–1, respectively, compared with model sensitizers, such as aromatic ketones. Findings from this report shed light on the fundamental photochemical properties of CDOM in organic matter isolates and whole waters and will help refine photochemical models to more accurately predict pollutant fate in the environment.
8198. 题目: Microbial biomass, metabolic functional diversity, and activity are affected differently by tillage disturbance and maize planting in a typical karst calcareous soil
期刊: Journal of Soils and Sediments
作者: Dan Xiao, Shuangshuang Xiao, Yingying Ye, Wei Zhang, Xunyang He, Kelin Wang
摘要: Purpose: Cultivation can affect soil microbial activities, with consequences for microorganisms that metabolize soil organic carbon and release CO2 to the atmosphere. Nevertheless, there is limited understanding of the short-term effects that tillage disturbance, maize planting, or their interactions exert on microbial biomass and metabolic function in a typical karst calcareous soil. A 1-year simulation experiment quantified the impacts of tillage disturbance and maize planting on soil microorganisms. Materials and methods: Four treatments (2 × 2 m plot size), comprising conventional tillage with (CTM) and without maize (CT), and non-tillage with (NTM) and without (NT) maize, were conducted. Microbial biomass carbon (MBC), carbon metabolic function (Biolog profiles), CO2 flux, soil organic carbon (SOC), and dissolved organic carbon (DOC) were measured after 1-year tillage disturbance and maize planting. Results and discussion: DOC was significantly lower in CTM, NTM, and CT than in NT, but SOC was slightly higher in NTM than in CTM and NT. Annual cumulative CO2 fluxes were significantly higher in CTM and NTM than in CT, which in turn was significantly higher than NT. Principal component analysis (PCA) suggests microbial community catabolic function differs in all treatments. CT showed significantly decreased MBC compared with NT, but significantly increased microbial metabolic activity and Simpson index (D). Compared with NT, NTM showed significantly increased microorganism metabolic activity, Shannon index (H), and D, but no significant difference in MBC. The interactions between maize planting and tillage disturbance had no significant effect on MBC or metabolic function diversity. Conclusions: Microbial biomass appears sensitive to tillage disturbance, while microbial metabolic activity is sensitive to maize planting. Maize planting with no tillage would increase CO2 emissions through enhanced microbial activity, but, at the same time, mitigate SOC loss due to an increase in C input by crop residues and roots left in the soil.
8199. 题目: Nitrogen cycling and origin of ammonium during infiltration of treated wastewater for managed aquifer recharge
期刊: Applied Geochemistry
作者: Matthew Silver, Kay Knöller, Johanna Schlögl, Christine Kübeck, Christoph Schüth
摘要: As more regions in the world look to replenish depleted aquifers, treated wastewater (TWW) is increasingly infiltrated in managed aquifer recharge (MAR) schemes. While MAR is a promising emerging technology, it also has the potential to generate pollutants along the infiltration flow path. In this study, we infiltrated treated wastewater through an organic-rich soil in column experiments operated with wetting and drying cycles. Ammonium, which was present only in trace concentrations in the TWW, increased in concentration with depth and exceeded the EU Water Framework Directive limit of 0.5 mg/L for up to a year, depending on the sampling depth. Pore water samples collected at the end of drying periods showed very high nitrate concentrations, indicating nitrification of some of the ammonium. Oxidation reduction potential often exceeded 200 mV during drying periods, showing conditions for nitrification, but dropped to below −100 mV during wetting periods, creating several possible pathways for ammonium production. Potential sources of ammonium are (1) dissolved organic nitrogen in the TWW, (2) nitrate in the TWW, and (3) organic nitrogen in the soil. δ15N in ammonium in pore water samples (mean 4.7‰) was slightly higher than δ15N the soil (2.4‰), indicating that the soil was likely the major source but also that nitrate (mean 17.2‰) may have been the source of some of the ammonium. Fractionation of 15N in nitrate as well as high concentrations of acetate (a labile organic carbon source) also indicate that dissimilatory nitrate reduction to ammonium may have formed some of the NH4+.
8200. 题目: Soil quality assessment in Yellow River Delta: Establishing a minimum data set and fuzzy logic model
作者: Chunsheng Wu, Gaohuan Liu, Chong Huang, Qingsheng Liu
摘要: The Yellow River Delta has abundant land resources, but the land exhibits heavy degeneration because of long-term exposure to harsh natural conditions and improper human activities, and the soil quality is poor in some areas. All these factors have adversely affected agricultural development and ecological protection in the Yellow River Delta. This study selected multiple physical and chemical indicators and used principal component analysis (PCA) to construct a minimum data set (MDS) to determine a comprehensive set of indicators for assessing soil quality in the Yellow River Delta. Moreover, a fuzzy logic model was used to assess soil quality and analyze the spatial distribution of the primary land use types in different soil quality grades. The results indicate that the MDS includes six soil indicators: total nitrogen (TN), available phosphorus (AP), available potassium (AK), soil organic matter (SOM), soil salinity (SS) and pH. According to the spatial distribution maps of the indicators, SS gradually declined from the coast to the inland areas, while TN and AP had opposite characteristics. AK and pH were evenly distributed around the study area, and SOM was highest in the center and gradually declined toward the edge of the study area. The soil quality was higher in inland areas than in coastal areas, and most of the study area was classified as grade III. Most of the farmland, forest, and garden plots were distributed in high-grade soil levels, but some of these plots were distributed in areas classified as grades V or VI. Many areas with high soil quality were unused, which indicated that the land resources of the study area should be planned reasonably.