21. 题目: Tillage-induced surface soil roughness controls the chemistry and physics of eroded particles at early erosion stage
期刊: Soil and Tillage Research
作者: Tingyu Hou, Timothy R. Filley, Yanan Tong, Benjamin Abban, Sarmistha Singh, A.N. Thanos Papanicolaou, Kenneth M. Wacha, Christopher G. Wilson, Indrajeet Chaubey
摘要: Intensive row crop agriculture on loess mantled hillslopes in the upper Midwest, USA, accelerates soil erosion and the loss of organic matter by increasing soil aggregate breakdown, changing surface roughness patterns, and leaving soil exposed to rainfall and wind for much of the year. There is a knowledge gap, however, in relating how the dynamics of soil erosion on hillslopes control landscape heterogeneity in terms of particle size, surface soil organic chemistry and reactivity. Simulated rainfall experiments on intensively managed hillslopes in the Clear Creek, IA watershed, USA, revealed that tillage-induced, oriented roughness controls the amount and organic geochemistry of soil particles mobilized downhill. The average discharge rate of mobilized sediment was nearly 30-fold higher when the tillage orientation was parallel to the runoff direction compared to when the tillage orientation (i.e. contour tillage) was perpendicular to the runoff direction. Mobilized particles under contour tillage were higher in organic carbon (OC) content and were relatively less decomposed, based on lignin chemistry, compared to analogous particles under the parallel tillage orientation. Contour tillage increased deposition of denser particles within the furrows and increased the release of the finer, lighter, and organic-rich material during over-spilling and contour breach. Our findings have important implications for understanding how the interaction of tillage practices and event-based erosion influences the spatial heterogeneity of soil geochemistry and potentially soil health across agricultural landscapes as well as understanding what controls the geochemical signature of soil erosion into streams.
22. 题目: Sulfur-based Mixotrophic Vanadium (V) Bio-reduction towards Lower Organic Requirement and Sulfate Accumulation
期刊: Water Research
作者: Zhongli Wang, Baogang Zhang, Chao He, Jiaxin Shi, Mengxiong Wu, Jianhua Guo
摘要: Although remediation of toxic vanadium (V) [V(V)] pollution can be achieved through either heterotrophic or sulfur-based autotrophic microbial reduction, these processes would require a large amount of organic carbons or generate excessive sulfate. This study reported that by using mixotrophic V(V) bio-reduction with acetate and elemental sulfur [S(0)] as joint electron donors, V(V) removal performance was enhanced due to cooccurrence of heterotrophic and autotrophic activities. Deposited vanadium (IV) was identified as the main reduction product by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Based on 16S rRNA gene amplicon sequencing, qPCR and genus-specific reverse transcription qPCR, it was observed that V(V) was likely detoxified by heterotrophic V(V) reducers (e.g., Syntrophobacter, Spirochaeta and Geobacter). Cytochrome c, intracellular nicotinamide adenine dinucleotide and extracellular polymeric substances were involved in V(V) reduction and binding. Organic metabolites synthesized by autotrophs (e.g., Thioclava) with energy from S(0) oxidation might compensate electron donors for heterotrophic V(V) and sulfate reducers. Less sulfate was accumulated presumably due to activities of sulfur-respiring genera (e.g., Desulfurella). This study demonstrates mixotrophic microbial V(V) reduction can save organic dosage and avoid excessive sulfate accumulation, which will be beneficial to bioremediation of V(V) contamination.
23. 题目: Intense methane ebullition from urban inland waters and its significant contribution to greenhouse gas emissions
期刊: Water Research
作者: Gongqin Wang, Xinghui Xia, Shaoda Liu, Ling Zhang, Sibo Zhang, Junfeng Wang, Nannan Xi, Qianru Zhang
摘要: The evasions of methane (CH4) and carbon dioxide (CO2) from inland waters represent substantial fluxes of greenhouse gases into the atmosphere, offsetting a large part of the continental carbon sink. However, the CH4 and CO2 emissions from urban inland waters are less constrained. In particular, ebullitive CH4 emissions from these waters are poorly understood. Here, we measured the concentrations and fluxes of CH4 and CO2 in rivers and lakes in the megacity of Beijing, China, between 2018 and 2019. The CH4 concentration ranged from 0.08 to 70.2 µmol L−1 with an average of 2.5 ± 5.9 µmol L−1. The average CH4 ebullition was 11.3 ± 30.4 mmol m−2 d−1 and was approximately 6 times higher than the global average. The average total CH4 flux (14.2 ± 35.1 mmol m−2 d−1) was 3 times higher than the global average, with ebullition accounting for 80% of the flux. The high surface water CH4 concentrations and ebullitive fluxes were caused by high sediment organic carbon/dissolved organic carbon contents, high aquatic primary productivity and shallow water depths in the urban inland waters. The CH4 emissions accounted for 20% of CO2 emissions in terms of the carbon release and were 1.7 times higher in terms of CO2 equivalent emissions from Beijing inland waters. Furthermore, the CH4 ebullition and its contribution to the total carbon gas emissions increased exponentially with the water temperature, suggesting a positive feedback probably occurs between the greenhouse gas emissions from urban inland waters and climate warming. This study confirms the major role of CH4 ebullition from urban inland waters in the global carbon budget under the rapid progress of global urbanization.
24. 题目: Composition and Lability of Photochemically Released Dissolved Organic Matter from Resuspended Estuarine Sediments
期刊: Organic Geochemistry
作者: Jennifer L. Harfmann, G. Brooks Avery, Hugh D. Rainey, Ralph N. Mead, Stephen A. Skrabal, Robert J. Kieber, J. David Felix, John R. Helms, David C. Podgorski
摘要: Photochemically-released dissolved organic matter (PR-DOM) from resuspended sediments is an understudied flux of dissolved organic carbon (DOC) and nutrients that has the potential to influence estuarine microbial food webs. There is currently limited knowledge on the composition, lability, and biological alterations of this material once released into the water column. This study addresses the composition and fate of PR-DOM from resuspended sediments of the Cape Fear River estuary (CFRE) in southeastern North Carolina. Six-hour irradiation released 22-44% more DOC, and PR-DOM was of a different composition and enhanced lability relative to dark controls. Irradiation led to release of humic-like DOM, indicated by increased chromophoric and fluorescent dissolved organic matter, substantial increases in the humification index, and production of oxidized higher molecular weight compounds with higher aromaticity relative to dark controls. However, DOM of lower molecular weight and reduced aromaticity was produced as well – indicated by increased spectral slope (S275-295) and decreased specific ultraviolet absorbance at 254 nm (SUVA254) relative to dark controls. This latter pool of DOM may be linked to nitrogen-(N-) and sulfur-(S-)containing compounds that were photodegraded or biologically altered during irradiation experiments. In subsequent lability incubation experiments, degradation of PR-DOM was more rapid than DOM released from dark controls, especially for marine humic-like fluorophores. Incubation of PR-DOM led to an 8-fold increase in molecular formulas that were unique to light-exposed DOM relative to unexposed DOM, the majority of which were N- and S-containing compounds. Given that coastal sediments are typically enriched in these nutrients, N- and S-containing compounds appear to influence the lability of PR-DOM from estuarine resuspended sediments. Estimated lability of photoreleased DOC from resuspension events in the CFRE is comparable to previous bioavailable DOC estimates and suggest that episodic photochemical interactions with sediments may act as a previously unrecognized source of labile DOC to bacteria and plankton in these coastal waters.
25. 题目: Microwave-assisted catalytic pyrolysis of apple wood to produce biochar: Co-pyrolysis behavior, pyrolysis kinetics analysis and evaluation of microbial carriers
期刊: Bioresource Technology
作者: Changhao Liu, Xiaochen Liu, Yanhui He, Xiongfang An, Daidi Fan, Zhansheng Wu
摘要: This study investigated the behavior and kinetics of co-pyrolysis of apple wood (AW) with H3PO4 and K3PO4 as catalysts under microwave to prepare biochar as microbial absorbent. The kinetic studies indicate that the co-pyrolysis of AW with H3PO4 or K3PO4 can effectively improve the pyrolysis efficiency and enhance the biochar characteristics by reducing of the activation energy of the pyrolysis reaction. The kinetic parameters indicate that the activation energy of the mixtures in the main pyrolysis stage is lower than that of a single AW, which mean that the co-pyrolysis of AW with H3PO4 or K3PO4 shows excellent synergy. Biochar characterization showed that the yield of biochar reached the highest 58.6% when the ratio (H3PO4/AW) is 0.5. The adsorption results show that the bacteria SL-44 can be effectively loaded on the surface of the biochar, and the adsorption process is combined with Langmuir model and process can proceed spontaneously.
26. 题目: Dynamics of community structure and bio-thermodynamic health of soil organisms following subtropical forest succession
期刊: Journal of Environmental Management
作者: Jun Wang, Hongfang Lu, Yongbiao Lin, Daniel E. Campbell, Hongyue Cai, Hai Ren
摘要: Soil organisms play essential roles in maintaining multiple ecosystem processes, but our understanding of the dynamics of these communities during forest succession remains limited. In this study, the dynamics of soil organism communities were measured along a 3-step succession sequence of subtropical forests (i.e., a conifer forest, CF; a mixed conifer and broad-leaved forest, MF; and a monsoon evergreen broad-leaved forest, BF). The eco-exergy evaluation method was used as a complement to the classic community structure index system to reveal the holistic dynamics of the bio-thermodynamic health of soil organism communities in a forest succession series. Association between the self-organization of soil organisms, soil properties, and plant factors were explored through redundancy analyses (RDA). The results indicated that the biomass of soil microbes progressively increased in the dry season, from 0.75 g m−2 in CF to 1.75 g m−2 in BF. Microbial eco-exergy showed a similar pattern, while the community structure and the specific eco-exergy remained constant. Different trends for the seasons were observed for the soil fauna community, where the community biomass increased from 0.72 g m−2 to over 1.97 g m−2 in the dry season, but decreased from 3.94 g m−2 to 2.36 g m−2 in the wet season. Faunal eco-exergies followed a similar pattern. Consequently, the average annual biomass of the soil faunal community remained constant (2.17–2.39 g m−2) along the forest succession sequence, while the significant seasonal differences in both faunal biomass and eco-exergy observed at the early successional stage (CF) were insignificant in the middle and late forest successional stages (MF and BF). Both the dynamics of soil microbes and soil fauna were tightly correlated with tree biomass and with soil physicochemical properties, especially soil pH, moisture, total nitrogen, nitrate nitrogen, and organic matter content.
27. 题目: Repeated drying and rewetting differently affect abiotic and biotic soil phosphorus (P) dynamics in a sandy soil: A 33P soil incubation study
期刊: Soil Biology and Biochemistry
作者: Hao Chen, Klaus A. Jarosch, Éva Mészáros, Emmanuel Frossard, Xiaorong Zhao, Astrid Oberson
摘要: Soil drying and rewetting (DRW) events are expected to occur at higher frequencies because of alterations in climate patterns. Readily extractable inorganic and microbial soil phosphorus (P) pools may be affected due to rapid changes in soil water availability. We aimed to determine how soil P dynamics are affected by repeated soil DRW using a sandy grassland soil that regularly experiences DRW. In a laboratory soil incubation study, the soil was exposed to three DRW cycles, with each cycle consisting of a two-day drying phase, a three-day dryness phase and a four-day moist phase after rapid rewetting. The indicators of abiotic processes (P sorption) and biotic processes (respiration, microbial abundance, potential phosphatase enzyme activities) were regularly determined together with water-extractable P, resin-extractable P and microbial P in a 33P-labeled soil. During the first DRW cycle, microbial P was reduced by half and accompanied by a concomitant but not equivalent increase in water-extractable P and a slight as well as delayed increase in resin-extractable P. Thus, increases in water-extractable P were explained by microbial P released during drying but also by microbial P occupying soil P sorption sites, thereby decreasing soil P sorption. Changes in the 33P-isotopic composition of microbial P at the same time suggested that microorganisms did not respond homogenously to the DRW treatment and indicated an increased mineralisation of previously unavailable organic P compounds. However, during the second and third DRW cycles, only water-extractable P, soil P sorption and potential phosphatase activities were affected by the DRW treatment, whereas all other parameters remained similar in values to the constant moist treatment. The effects of DRW on soil P dynamics appeared to affect water-extractable P more long-lastingly, whereas microbial P and most of the biotic indicators quickly adjusted to the DRW treatment. We conclude that the current concepts suggesting an increased mobility of soil P towards other environmental compartments due to soil DRW should consider that abiotic and biotic soil P dynamics are not equally affected in the case of short repetition of DRW incidences.
28. 题目: Distribution of antibiotics in water, sediments and biofilm in an urban river (Córdoba, Argentina, LA)
期刊: Environmental Pollution
作者: Valdés M. Eugenia, H.M.L.M. Santos Lúcia, Rodríguez Castro M. Carolina, Giorgi Adonis, Barceló Damià, Rodríguez-Mozaz Sara, Amé M. Valeria
摘要: In this study, we evaluated the distribution of up to forty-three antibiotics and 4 metabolites residues in different environmental compartments of an urban river receiving both diffuse and point sources of pollution. This is the first study to assess the fate of different antibiotic families in water, biofilms and sediments under a real urban river scenario. Solid phase extraction, bead-beating disruption and pressurized liquid extraction were applied for sample preparation of water, biofilm and sediment respectively, followed by the quantification of target antibiotics by UPLC-ESI-MS/MS. Twelve antibiotics belonging to eight chemical families were detected in Suquía River samples (67% positive samples). Sites downstream the WWTP discharge were the most polluted ones. Concentrations of positive samples ranged 0.003-0.29 μg L-1 in water (max. cephalexin), 2-652 μg kg-1d.w. in biofilm (max. ciprofloxacin) and 2-34 μg kg-1d.w.in sediment (max. ofloxacin). Similar total antibiotic concentrations were found in water during wet and dry season. However, higher concentrations were detected in biofilm and sediments during the wet season. Fluoroquinolones, macrolides and trimethoprim were the most frequently detected antibiotics in the three compartments. However cephalexin was the prevalent antibiotic in water. Antibiotics exhibited preference for their accumulation from water into biofilms rather than in sediments (bioaccumulation factors > 1,000 L kg-1d.w. in biofilms, while pseudo-partition coefficients in sediments < 1,000 L kg-1d.w.). High water quality and organic carbon sediment content were associated with autotrophic communities in biofilm situated upstream WWTP. Instead, Downstream the WWTP there was an association of antibiotics levels in biofilms with ash-free dry weight a low water quality jointly with the increase of antibiotic concentrations and biofilm biomass (indicative of heterotrophic communities). Cephalexin and clarithromycin in river water were found to pose high risk for the aquatic ecosystem, while ciprofloxacin presented high risk for development of antimicrobial resistance. This study contributes to the understanding of the fate and distribution of antibiotic pollution in urban rivers, reveals biofilm accumulation as an important environmental fate, and calls for attention to government authorities to manage identified highly risk antibiotics. Antibiotics downstream urban WWTP and diffuse sources accumulate preferentially in river biofilms rather than sediments, posing environmental and resistance risk.
29. 题目: Rhizosphere effect and its associated soil-microbe interactions drive iron fraction dynamics in tidal wetland soils
期刊: Science of The Total Environment
作者: Shuyao Xiao, Min Luo, Yuxiu Liu, Jin Bai, Yang Yang, Zhifeng Zhai, Jiafang Huang
摘要: It is becoming increasingly clear that plants can affect iron (Fe) dynamics in tidal wetland soils, but whether this is rhizosphere effect-dependent remains unclear. To assess rhizosphere effects on soil Fe cycling, in-situ rhizosphere and bulk soil samples (0–60-cm) were collected from a tidal wetland across plant growth stages (regreening, shooting, and senescence). Changes in Fe fractions, the abundance of Fe-oxidizing/reducing bacteria (16S rRNA gene), root morphology traits, and soil and porewater geochemistry were examined. Overall, the rhizosphere effect decreased soil pH but increased the concentrations of dissolved organic carbon (DOC), porewater Fe2+, and bicarbonates (HCO3−). Both Fe-oxidizing and Fe-reducing bacteria were more enriched in the rhizosphere than those in the bulk soil. The rhizosphere effect increased the concentrations of amorphous and crystalline Fe(III), and also enhanced the proportion of amorphous Fe(III). The rhizosphere had higher concentrations of non-sulfidic ferrous iron [Fe(II)] but lower concentrations of ferrous sulfide (FeS) and pyrites (FeS2) than those in bulk soils, suggesting that the rhizosphere effect favors microbial Fe(III) reduction but suppresses microbial sulfate reduction. Moreover, the rhizosphere amorphous Fe(III) levels changed following the patterns of root porosity, which attained peak values at the root tips. The abundance of Fe-reducing bacteria was controlled by both DOC and amorphous Fe(III) concentrations, which were relatively higher during the regreening and shooting stages than those during the senescence stage. Taken together, our findings highlight that the rhizosphere effect transfer Fe from the bulk soil to the rhizosphere and especially redirects it from Fe–S associations to microbially-mediated Fe redox cycling. This rapid Fe redox cycling could be responsible for buffering soils and organisms from sulfide accumulation and stimulate C mineralization in the tidal wetland ecosystem.
30. 题目: Molecular characterization and environmental impacts of water-soluble organic compounds of bio-oil from the thermochemical treatment of domestic sewage sludge
期刊: Science of The Total Environment
作者: Minghao Shen, Xiangdong Zhu, Hua Shang, Fei Feng, Yong Sik Ok, Shicheng Zhang
摘要: Water-soluble organic compounds derived from bio-oil (WOCB) are regarded as potential risk sources of sludge thermochemical treatment. This study showed that 10.35 mg of water-soluble organic carbon and 1.32 mg of water-soluble organic nitrogen were released per gram of sludge when the final temperature of thermochemical treatment was 600 °C. WOCB was mainly formed at 300–500 °C. Furthermore, FT-ICR MS results indicated that high temperatures promoted deamination reactions, and low molecular weight (LMW) compounds with low oxygen number polymerized into aromatic compounds with increasing temperature. Noteworthily, WOCB released at 20–600 °C showed strong phytotoxicity to wheat. LMW compounds with lignin/carboxylic rich alicyclic molecules (CRAM)-like structures derived from low temperatures (200–400 °C) induced this inhibitory effect, but lipids containing nitrogen and sulfur from high temperatures (400–600 °C) can act as nutrients to promote wheat growth. This study provides theoretical support for the risk control and benefits assessments of sludge thermochemical treatment.
31. 题目: Developing Understanding of the Fate and Behaviour of Silver in Fresh Waters and Waste Waters
期刊: Science of The Total Environment
作者: D. Scott Smith, R. Nasir, Wayne Parker, A. Peters, G. Merrington, R. van Egmond, S. Lofts
摘要: The Windermere Humic Aqueous Model (WHAM) is often used for risk assessment of metals; WHAM can be used to estimate the potential bioavailability of dissolved metals, where metals complexed to dissolved organic matter (DOM) are expected to be less toxic than ionic forms. Silver is a potential metal of concern but WHAM has not been rigorously tested against experimental measurements. This study compares WHAM predictions to measured ionic silver during fixed pH (4, 8 or 10) argentometric titrations of DOM from diverse origins. There were almost two orders of magnitude variation in free silver between sources but, within model uncertainty, WHAM captured this variability. This agreement, between measurements and models, suggests that WHAM is an appropriate tool for silver risk assessment in surface receiving waters when DOM is predominantly in the form of humic/fulvic acids. In sewage samples WHAM dramatically underestimated silver binding by approximately 3 orders of magnitude. Simulations with additional specific strong silver binding sulphide-like binding sites could explain Ag binding at low loadings, but not at higher loadings. This suggests the presence of additional intermediate strength binding sites. These additional ligands would represent components of the raw sewage largely absent in natural waters unimpacted by sewage effluents. A revised empirical model was proposed to account for these sewage-specific binding sites. Further, it is suspected that as sewage organic matter is degraded, either by natural attenuation or by engineered treatment, that sewage organic matter will degrade to a form more readily modelled by WHAM; i.e., humic-like substances. These ageing experiments were performed starting from raw sewage, and the material did in fact become more humic-like, but even after 30 days of aerobic incubation still showed greater Ag+ binding than WHAM predictions. In these incubation experiments it was found that silver (up to 1000 μg/L) had minimal impact on ammonia oxidation kinetics.
32. 题目: Understanding of the mechanism of extracellular polymeric substances of aerobic granular sludge against tetracycline from the perspective of fluorescence properties
期刊: Science of The Total Environment
作者: Zhengwen Li, Chunli Wan, Xiang Liu, Li Wang, Duu-Jong Lee
摘要: Aerobic granular sludge (AGS) exhibited an excellent removal efficiency and a high tolerance in the treatment of antibiotics wastewater. Extracellular polymeric substances (EPS) of AGS with abundant binding sites might serve as the first barrier to prevent the direct contact of antibiotics and cells, thereby keeping the stability of AGS. In this study, the investigations in the fluorescence properties and the molecular weight of AGS-EPS after interaction with tetracycline (TC) were combined to reveal the resistance mechanism of AGS-EPS against TC. The two-dimensional correlation spectroscopy (2D-COS) was utilized to analyze the interaction priority of the AGS-EPS components with TC. Results showed that TC interacted with proteins and humic acid in AGS-EPS by forming a complex through hydrogen bond and van der Waals force. Compared with humic acid, TC could preferentially interact with proteins and form more stable complexes. Moreover, the components with the larger molecular weight in AGS-EPS interact with TC prior to which with smaller molecular weight. Significantly, TC exhibited the potential of binding with the divalent cation of AGS-EPS and caused the conformation changes of the protein. Therefore, AGS-EPS could resist the TC at a certain concentration range by trapping antibiotics, while over-loaded TC would cause the instability of AGS due to the limited interaction site of AGS-EPS and the destructive effect of antibiotics on AGS-EPS. This study provided a theoretical basis for understanding the interaction mechanism between antibiotics and AGS-EPS and offered a reference for AGS to maintain the stability of granules under the threat of antibiotics.
33. 题目: Soil organic carbon fractions, C-cycling hydrolytic enzymes, and microbial carbon metabolism in Chinese fir plantations
期刊: Science of The Total Environment
作者: Chaoqun Wang, Lin Xue, Yuhong Dong, Ruzhen Jiao
摘要: The mechanisms by which planting density affects soil organic carbon (SOC) fractions, C-cycling associated hydrolytic enzyme activities, and microbial carbon metabolism remain unclear. We evaluated the influences of five planting densities (D1: 1667 stems·ha−1, D2: 3333 stems·ha−1, D3: 4444 stems·ha−1, D4: 5000 stems·ha−1, and D5: 6667 stems·ha−1) on the concentrations of SOC, microbial biomass carbon (MBC), easily oxidizable carbon (EOC), and dissolved organic carbon (DOC), the activities of invertase, cellulase, and β-glucosidase, and microbial carbon metabolism activities in 5- and 35-year-old Chinese fir plantations. Generally, no significant differences in the SOC and DOC concentrations among five planting densities in 5-year-old plantations were found, but the SOC and DOC were significantly higher in high-density plantations (D3, D4, and D5) than in low-density plantations (D1 and D2) in 35-year-old plantations. The EOC concentration in low-density plantations was lower than that in high-density plantations in both 5- and 35-year-old plantations. The high planting density was associated with higher MBC, activities of invertase and β-glucosidase, and microbial carbon metabolism activity in 5-year-old plantations, but the opposite was found in 35-year-old plantations. The high-density plantations exhibited a significant decrease in cellulase activity in 35-year-old plantations. These results highlight that although increased planting density would enrich SOC storage after a long-term rotation of plantations, it also reduces microbial and enzymatic activities. This has important implications in the formulation of planting density management strategies to increase SOC stocks while maintaining soil fertility.
34. 题目: Integrated analyses of petroleum biomarkers and polycyclic aromatic compounds in lake sediment cores from an oil sands region
期刊: Environmental Pollution
作者: Alexandre P.J. Salat, David C. Eickmeyer, Linda E. Kimpe, Roland I. Hall, Brent B. Wolfe, Lukas J. Mundy, Vance L. Trudeau, Jules M. Blais
摘要: We examined polycyclic aromatic compounds (PACs) and petroleum biomarkers (steranes, hopanes, and terpanes) in radiometrically-dated lake sediment cores from the Athabasca oil sands region (AOSR) and the Peace-Athabasca Delta (PAD) region in Alberta (Canada) to determine whether contributions from petroleum hydrocarbons have changed over time. Two floodplain lakes in the PAD (PAD 30, PAD 31) recorded increased flux of alkylated PACs and increased petrogenic (petroleum-derived) hydrocarbons after ∼1980, coincident with a decline of sediment organic carbon content and a rise of bulk sedimentation rate, likely due to increased Athabasca River flow. A large expansion of upstream oilsands mining, upgrading, and refining may also have contributed to the observed shift to more petrogenic hydrocarbons to sediments since the 1980s. Alkylated PAC flux increased in the floodplain lake analyzed within the AOSR (Saline Lake) since the 1970s-1980s, coincident with a sharp rise in sediment organic carbon content and increased contributions of petrogenic hydrocarbons. These changes identify increased supply of petrogenic PACs occurred as Athabasca River floodwaters waned, and may implicate aerial contributions of petrogenic hydrocarbons from oilsands activity. PACs and petroleum biomarkers (steranes, hopanes, and terpanes) in sediment cores from Saline Lake, PAD 30 and PAD 31 revealed a predominance of petrogenic hydrocarbons in these lakes. In contrast, we recorded minimal petrogenic hydrocarbons in the reference lakes outside the surface minable area of the AOSR and PAD (Mariana Lake and BM11), though we noted slight increases in petrogenic contributions to modern (2010-2016) sediments. We show how a combined analysis of PACs and petroleum biomarkers in sediments is useful to quantify petrogenic contributions to lakes with added confidence and highlight the potential for petroleum biomarkers in lake sediment cores as a novel and effective method to track petroleum hydrocarbons in lake sediment.
35. 题目: Methane emissions respond to soil temperature in convergent patterns but divergent sensitivities across wetlands along altitude
期刊: Global Change Biology
作者: Dan Zhu, Ning Wu, Nabin Bhattarai, Krishna Prasad Oli, Huai Chen, Gopal Singh Rawat, Irfan Rashid, Maheshwar Dhakal, Srijana Joshi, Jianqing Tian, Qiu’an Zhu, Sunita Chaudhary, Kuenzang Tshering
摘要: Among the global coordinated patterns in soil temperature and methane emission from wetlands, a declining trend of optimal soil temperature for methane emissions from low to high latitudes has been witnessed, while the corresponding trend along the altitudinal gradient has not yet been investigated. We therefore selected two natural wetlands located at contrasting climatic zones from foothill and mountainside of Nepal Himalayas, to test: 1) whether the optimal temperature for methane emissions decreases from low to high altitude, and 2) whether there is a difference in temperature sensitivity of methane emissions from those wetlands. We found significant spatial and temporal variation of methane emissions between the two wetlands and seasons. Soil temperature was the dominant driver for seasonal variation in methane emissions from both wetlands, though its effect was perplexed by the level of standing water, aquatic plants and dissolved organic carbon, particularly in the deep water area. When integrative comparison was conducted by adding the existing data from wetlands of diverse altitudes, and the latitude‐for‐altitude effect was taken into account, we found the baseline soil temperatures decrease whilst the altitude rises with respect to a rapid increase in methane emission from all wetlands, however, remarkably higher sensitivity of methane emissions to soil temperature (apparent Q10) was found in mid‐altitude wetland. We provide the first evidence of an apparent decline in optimal temperature for methane emissions with increasing elevation. These findings suggest a convergent pattern of methane emissions with respect to seasonal temperature shifts from wetlands along altitudinal gradient, while a divergent pattern in temperature sensitivities exhibits a single peak in mid‐altitude.
36. 题目: Algal origin of sponge sterane biomarkers negates the oldest evidence for animals in the rock record
期刊: Nature Ecology & Evolution
作者: Ilya Bobrovskiy, Janet M. Hope, Benjamin J. Nettersheim, John K. Volkman, Christian Hallmann, Jochen J. Brocks
摘要: The earliest fossils of animal-like organisms occur in Ediacaran rocks that are approximately 571 million years old. Yet 24-isopropylcholestanes and other C30 fossil sterol molecules have been suggested to reflect an important ecological role of demosponges as the first abundant animals by the end of the Cryogenian period (>635 million years ago). Here, we demonstrate that C30 24-isopropylcholestane is not diagnostic for sponges and probably formed in Neoproterozoic sediments through the geological methylation of C29 sterols of chlorophyte algae, the dominant eukaryotes at that time. These findings reconcile biomarker evidence with the geological record and revert the oldest evidence for animals back into the latest Ediacaran.
37. 题目: Sulphate in freshwater ecosystems: A review of sources, biogeochemical cycles, ecotoxicological effects and bioremediation
期刊: Earth-Science Reviews
作者: Dominik Zak, Michael Hupfer, Alvaro Cabezas, Gerald Jurasinski, Joachim Audet, Andreas Kleeberg, Robert McInnes, Søren Munch Kristiansen, Rasmus Jes Petersen, Haojie Liu, Tobias Goldhammer
摘要: Sulphate (SO42-) concentrations in freshwaters have increased globally over the last decades even though a strong reduction in atmospheric sulphur (S) deposition has occurred across large parts of North America and Europe. However, the extent and effects of increased SO42- concentrations in freshwater and terrestrial ecosystems remain poorly understood regarding many aspects of ecosystem structure and functioning. Here, we review the sources of SO42- pollution, environmental impacts on freshwater ecosystems and bioremediation opportunites and we identify key knowledge gaps and future research needs. Natural sources of dissolved SO42- in freshwater ecosystems include mineral weathering, volcanic activity, decomposition and combustion of organic matter, oxidation of sulphides, and sea spray aerosols. Acid mine drainage, fertiliser leaching from agricultural soils, wetland drainage, agricultural and industrial wastewater runoff as well as sea level changes are the main direct and indirect sources of the anthropogenic SO42- input to waterbodies. Increasing SO42- concentrations in freshwater systems influence the biogeochemical processes of carbon, nitrogen and phosphorus. Similarly, iron availability can be critical in determining the adverse effects of SO42- on environmental receptors. The literature reviewed clearly demonstrates that SO42- pollution may have toxic effects on aquatic plants and animal organisms, including, among others, fishes, invertebrates and amphibians, and it may also have negative implications for human health. Bioremediation systems provide opportunities to mitigate the impacts of SO42-, but removal efficiencies range widely from 0% to 70% across treatment systems such as constructed wetlands, permeable reactive barriers and bioreactors. We conclude that examination of increased SO42- concentrations and fluxes at different spatial scales is urgently needed as the ongoing global perturbation of the S cycle is likely to be accelerated by climate change and human development activities. The adverse effects of this on freshwater organisms worldwide may prove detrimental to the future well-being of humans and ecosystems. Field-scale research to estimate the ecotoxicological effects of elevated SO42- concentrations is recommended as is widespread implementation of large-scale wetland restoration and bioremediation systems to reduce SO42- loads on freshwater ecosystems.
38. 题目: Combined applications of organic and synthetic nitrogen fertilizers for improving crop yield and reducing reactive nitrogen losses from China’s vegetable systems: a meta-analysis
期刊: Environmental Pollution
作者: Bin Liu, Xiaozhong Wang, Lin Ma, Dave Chadwick, Xinping Chen
摘要: The combined application of organic and synthetic nitrogen (N) fertilizers is being widely recommended in China’s vegetable systems to reduce reliance on synthetic N fertilizer. However, the effect of substituting synthetic fertilizer with organic fertilizer on vegetable productivity (yield, N uptake and nitrogen use efficiency) and reactive nitrogen (Nr) losses (N2O emission, N leaching and NH3 volatilization) remains unclear. A meta-analysis was performed using peer-reviewed papers published from 2000 to 2019 to comprehensively assess the effects of combined application of organic and synthetic N fertilizers. The results indicate that overall, the vegetable yield, N2O emission and NH3 volatilization were not significantly changed, whereas N leaching was reduced by 44.6% and soil organic carbon (SOC) concentration increased by 12.5% compared to synthetic N fertilizer alone. Specifically, when synthetic N substitution rates (SRs) were ≤70%, vegetable yields and SOC concentration were increased by 5.5%-5.6% and 13.1-18.0%, and N leaching was reduced by 41.6%-48.1%. At the high substitution rate (SR>70%), vegetable yield was reduced by 13.5%, N2O emission was reduced by 14.3%, and SOC concentration increased by 16.4%. Mixed animal-plant sources of organic N preferentially increased vegetable yield and SOC concentration, and reduced N2O emission and N leaching compared with single sources of organic-N. Greenhouse gas (GHG) emission was decreased by 28.4%-34.9% by combined applications of organic and synthetic N sources, relative to synthetic N fertilizer alone. We conclude that appropriate rates (SR≤70%) of combined applications of organic and synthetic N fertilizers could improve vegetable yields, decrease Nr and GHG emission, and facilitate sustainable development of coupled vegetable-livestock systems.
39. 题目: One-year measurements of secondary organic aerosol (SOA) markers in the Paris region (France): concentrations, gas/particle partitioning and SOA source apportionment
期刊: Science of The Total Environment
作者: G.M. Lanzafame, D. Srivastava, O. Favez, B.A.M. Bandowe, P. Shahpoury, G. Lammel, N. Bonnaire, L.Y. Alleman, F. Couvidat, B. Bessagnet, A. Albinet
摘要: Twenty-five biogenic and anthropogenic secondary organic aerosol (SOA) markers have been measured over a one-year period in both gaseous and PM10 phases in the Paris region (France). Seasonal and chemical patterns were similar to those previously observed in Europe, but significantly different from the ones observed in America and Asia due to dissimilarities in source precursor emissions. Nitroaromatic compounds showed higher concentrations in winter due to larger emissions of their precursors originating from biomass combustion used for residential heating purposes. Among the biogenic markers, only isoprene SOA marker concentrations increased in summer while pinene SOA markers did not display any clear seasonal trend. The measured SOA markers, usually considered as semi-volatiles, were mainly associated to the particulate phase, except for the nitrophenols and nitroguaiacols, and their gas/particle partitioning (GPP) showed a low temperature and OM concentrations dependency. An evaluation of their GPP with thermodynamic model predictions suggested that apart from equilibrium partitioning between organic phase and air, the GPP of the markers is affected by processes suppressing volatility from a mixed organic and inorganic phase, such as enhanced dissolution in aerosol aqueous phase and non-equilibrium conditions. SOA marker concentrations were used to apportion secondary organic carbon (SOC) sources applying both, an improved version of the SOA-tracer method and positive matrix factorization (PMF) Total SOC estimations agreed very well between both models, except in summer and during a highly processed Springtime PM pollution event in which systematic underestimation by the SOA tracer method was evidenced. As a first approach, the SOA-tracer method could provide a reliable estimation of the average SOC concentrations, but it is limited due to the lack of markers for aged SOA together with missing SOA/SOC conversion fractions for several sources.
40. 题目: Climatic warming enhances soil respiration resilience in an arid ecosystem
期刊: Science of The Total Environment
作者: Hongying Yu, Xiaodi Liu, Quanhui Ma, Zuotian Yin, Yuhui Wang, Zhenzhu Xu, Guangsheng Zhou
摘要: Precipitation plays a vital role in maintaining desert ecosystems in which rain events after drought cause soil respiration (Rs) pulses. However, this process and its underlying mechanism remain ambiguous, particularly under climatic warming conditions. This study aims to determine the magnitude and drivers of Rs resilience to rewetting. We conducted a warming experiment in situ in a desert steppe with three climatic warming scenarios—ambient temperature as the control, long-term and moderate warming treatment, and short-term and acute warming treatment. Our findings showed that the average Rs over the measurement period in the control, moderate and acute warming plots were 0.51, 0.30 and 0.30 μmol·CO2·m−2·s−1, respectively, and significantly increased to 1.72, 1.41 and 1.72 μmol·CO2·m−2·s−1, respectively, after rewetting. Both microbial and root respiration substantially increased by rewetting; microbial respiration contributed more than root respiration to total Rs. The Rs significantly increased with microbial biomass carbon and soil organic carbon (SOC) contents. The Rs increase by rewetting might be due to the greater microbial respiration relying heavily on microbial biomass and the larger amount of available SOC after rewetting. A trackable pattern of Rs resilience changes occurred during the daytime. The resilience of Rs in acute warming plots was significantly higher than those in both moderate warming and no warming plots, indicating that Rs resilience might be enhanced with drought severity induced by climatic warming. These results suggest that climatic warming treatment would enhance the drought resilience of soil carbon effluxes following rewatering in arid ecosystems, consequently accelerating the positive feedback of climate change. Therefore, this information should be included in carbon cycle models to accurately assess ecosystem carbon budgets with future climate change scenarios in terrestrial ecosystems, particularly in arid areas.