17341. 题目: Catalytic ozonation of organic contaminants in petrochemical wastewater with iron-nickel foam as catalyst
期刊: Separation and Purification Technology
作者: Yuanxing Huang, Mengyu Luo, Zhihua Xu, Daofang Zhang, Liang Li
摘要: This work investigated the removal of organic contaminants in actual petrochemical wastewater by catalytic ozonation with iron-nickel foam as catalyst. Under different conditions, the DOC removal percentages ranged from 40% to 61%, the sCOD removals were from 73% to 96% in the reaction time of 120 min. Two thirds of the 66 detected organic compounds disappeared in the treated wastewater. The biodegradability of the petrochemical wastewater was greatly improved after catalytic ozonation. TP, TN, NO3-N, Cl- and some heavy metals in the petrochemical wastewater were also removed to some extent. The influence of pH and initial organic matter concentration on the performance of catalytic ozonation was limited. Increase of aqueous ozone concentration and catalyst dosage was advantageous for organic contaminants removal. The probable mechanism of catalytic ozonation was proposed as that the iron-nickel foam was oxidized by ozone into the mixture of oxides, hydroxides, and hydroxyoxides. On one hand, the hydroxyl groups on the catalyst surface motivated the formation of •OH. On the other hand, the electrons transferred among different valences of transition metals facilitated the decomposition of ozone. The generated •OH diffused into bulk solution, working together with ozone to degrade the organic contaminants. From theoretical modeling, the residue ozone in the off gas can be reduced from 98% to 11% by using iron-nickel foam as the catalyst.
17342. 题目: Prioritization of unregulated disinfection by-products in drinking water distribution systems for human health risk mitigation: A critical review
期刊: Water Research
作者: Haroon R. Mian, Guangji Hu, Kasun Hewage, Manuel J. Rodriguez, Rehan Sadiq
摘要: Water disinfection involves the use of different types of disinfectants, which are oxidizing agents that react with natural organic matter (NOM) to form disinfection by-products (DBPs). The United States Environmental Protection Agency (USEPA) has established threshold limits on some DBPs, which are known as regulated DBPs (R-DBPs). The human health risks associated with R-DBPs in drinking water distribution systems (DWDSs) and application of stricter regulations have led water utilities to switch from conventional disinfectant (i.e., chlorination) to alternative disinfectants. However, the use of alternative disinfectants causes formation of a new suit of DBPs known as unregulated DBPs (UR-DBPs), which in many cases can be more toxic. There is a growing concern of UR-DBPs formation in drinking water. This review prioritizes some commonly occurring UR-DBP groups and species in DWDSs based on their concentration level, reported frequency, and toxicity using an indexing method. There are nine UR-DBPs group and 36 species that have been identified based on recent published peer-reviewed articles. Haloacetonitriles (HANs) and haloacetaldehydes (HALs) are identified as important UR-DBP groups. Dichloroacetonitrile (DCAN) and trichloroacetaldehye (TCAL) are identified as critical UR-DBPs species. The outcomes of this review can help water regulators to identify the most critical UR-DBPs species in the context of drinking water safety and provide them with useful information to develop guidelines or threshold limits for UR-DBPs. The outcomes can also help water utilities in selecting water treatment processes for the mitigation of human health risk posed by UR-DBPs through drinking water.
17343. 题目: Heterotrophic microbes upgrade food value of a terrestrial carbon resource for Daphnia magna
期刊: Limnology and Oceanography
作者: Yali Tang, Xiaoqin Yang, Ruohua Xu, Xiufeng Zhang, Zhengwen Liu, Yongdong Zhang, Henri J. Dumont
摘要: Terrestrial carbon resources are generally regarded as inferior‐quality food for zooplankton due to a lack of essential biomolecules (e.g., polyunsaturated fatty acids). However, recent stable isotopic studies have suggested terrestrial carbon to be substantial resource for zooplankton, though the mechanisms of assimilation are not well understood. Here, we consider the possibility that heterotrophic microbes can upgrade the nutritional value of terrestrial carbon and thereby support the somatic growth and reproduction of zooplankton. To test this hypothesis, a simplified experimental food chain was established. Aquatic microbes were raised under dark laboratory conditions on a terrestrial carbon source, decaying corn straw (Zea mays L.), and the resulting degradation products were supplied as food to Daphnia magna. Significant increases in microbial abundance and concomitant increases in polyunsaturated fatty acid were observed during the degradation of corn straw. Furthermore, experiments indicated that the somatic growth and reproduction of D. magna was supported exclusively by the products of corn straw decay. Our results indicate a pathway for the assimilation of terrestrial carbon by zooplankton, in which heterotrophic microbes serve as trophic links.
17344. 题目: Accumulation of organic carbon and its association with macro-aggregates during 100 years of oasis formation
作者: Chenhua Li, Yan Li, Jiangbo Xie, Yan Liu, Yugang Wang, Xuecan Liu
摘要: The maintenance and accumulation of soil organic carbon (SOC) is critical to the agricultural sustainability and environmental stability in oasis-desert belts. The objective of this study was to determine the effects of oasis formation on SOC and aggregate structure, as well as the linkage between them, throughout a 0–200 cm soil profile. The investigation was conducted in five oases at the northern foot of the Tianshan Mountains in Central Asia. Oasis farmlands reclaimed 3, 5, 10, 20, 50, and >100 years ago were compared with the desert pairs they originated from. The SOC content significantly increased throughout the whole profile after 20 years of reclamation, despite a loss in the first 10 years of reclamation. The values reached maxima at 50 years of reclamation, which increased by 67–135% compared to initial values. The macro-aggregate (diameter > 0.25 mm) fraction with high carbon (C) concentration significantly increased throughout the soil profile after reclamation, and showed the greatest variation during oasis formation, compared with the other aggregate fractions (0.25–0.053 and <0.053 mm). These changes were significantly correlated with increases in soil nutrients and microbial biomass and decreases in soil pH and salt during oasis formation. In conclusion, the oasis formation enhanced SOC accumulation not only in topsoil but also in deep soil, and soil aggregate structure was improved by increased macro-aggregates. The formation of macro-aggregates and the increase in their associated C had significant correlations with SOC accumulation. Fertilization, especially inorganic nitrogen, very likely promoted the SOC accumulation and soil aggregation in concert with annual input of crop residues into the originally poor desert soils during oasis formation.
17345. 题目: Seasonal and spatial distributions of euphotic zone and long-term variations in water transparency in a clear oligotrophic Lake Fuxian, China
期刊: Journal of Environmental Sciences
作者: Qichao Zhou, Yunlin Zhang, Kaidi Li, Licheng Huang, Fengle Yang, Yuanyang Zhou, Junjun Chang
摘要: To assess the seasonal and spatial variations and long-term trends in water optical properties in Lake Fuxian, investigations based on field work in four seasons and a long-term analysis of data from 1980 to 2014 were conducted. The results show that there was no significant variation in the euphotic depth (Zeu) across the four seasons, and no significant correlations between Zeu and potential influencing factors in seasons other than summer, suggesting that the water itself may be a major factor regulating the Zeu in general. Nevertheless, significant differences in Zeu between the north region (NR) and the south region (SR) were observed in all seasonal tests except spring. This finding relates to a higher abundance of chromophoric dissolved organic matter (CDOM) in the NR due to runoff, especially in the rainy seasons (summer and autumn). CDOM and its terrigenous component had an important impact on Zeu in summer, with the highest precipitation, and impacts from suspended solids and non-algal particles were also found in the NR in summer. The Secchi disk depth in the lake decreased clearly over the years, with significantly negative correlations with the increasing permanganate index and air temperature, implying that organic contaminants (CDOM and/or phytoplankton) are important regulators of water transparency. We estimate that the combined effects of climate warming and changes in land use and land cover are also indirect regulating factors. These findings should be considered in the protection of Lake Fuxian, owing to the importance of light penetration in aquatic ecosystems.
17346. 题目: Manganese limitation as a mechanism for reduced decomposition in soils under atmospheric nitrogen deposition
期刊: Soil Biology and Biochemistry
作者: Emily D. Whalen, Richard G. Smith, A. Stuart Grandy, Serita D. Frey
摘要: Long-term atmospheric nitrogen (N) deposition has been shown to reduce leaf litter and lignin decomposition in temperate forest soils, leading to an accumulation of soil carbon (C). Reduced decomposition has been accompanied by altered structure and function of fungal communities, the primary decomposers in forest ecosystems; however, a mechanistic understanding of fungal responses to chronic N enrichment is lacking. A reduction in soil and litter manganese (Mn) concentrations under N enrichment (i.e., Mn limitation) may help explain these observations, because Mn is a cofactor and regulator of lignin-decay enzymes produced by fungi. We conducted a laboratory study to evaluate the effect of Mn availability on decomposition dynamics in chronically N-enriched soils. We measured litter mass loss, lignin relative abundance, and lignin-decay enzyme activities, and characterized the litter fungal community by ITS2 metabarcoding. We observed a significant positive correlation between Mn availability and lignin-decay enzyme activities. In addition, long-term (28 years) N enrichment increased the relative abundance of ‘weak’ decomposers (e.g., yeasts), but this response was reversed with Mn amendment, suggesting that higher Mn availability may promote fungal communities better adapted to decompose lignin. We conclude that Mn limitation may represent a mechanism to explain shifts in fungal communities, reduced litter decomposition, and increased soil C accumulation under long-term atmospheric N deposition.
17347. 题目: Mapping future soil carbon change and its uncertainty in croplands using simple surrogates of a complex farming system model
作者: Zhongkui Luo, Sandra Eady, Bharat Sharma, Timothy Grant, De Li Liu, Annette Cowie, Ryan Farquharson, Aaron Simmons, Debbie Crawford, Ross Searle, Andrew Moore
摘要: Soil organic carbon (SOC) in agricultural soils is vital for soil fertility for sustainable agricultural production and climate change resilience. Process-based farming system models are widely used to predict SOC dynamics in agricultural soils, but their application at regional scales is largely limited by computational requirements, data availability, and uncertainties in model predictions. Here we present an approach of combining a farming system model and a simplified surrogate model that emulates and mimics the behaviour of complex process-based models to predict SOC change (∆SOC) and its uncertainty in Australian dryland cropping regions under anticipated climate change. We first calibrated and validated the farming system model APSIM for simulating ∆SOC (0–30 cm soil) using data from 90 farming-system trials at 28 sites across the study regions. Next we conducted a comprehensive simulation across the region using the validated APSIM model to predict ∆SOC over the period 2009–2070. Then simple surrogate models were developed based on the APSIM outputs. The surrogate models were able to explain >96% of the variation in APSIM-predicted ∆SOC. Last the surrogate models were applied across the regions at the resolution of 1 km. In our simulations, Australian dryland cropping soils under farmers' common management practices and future climate conditions were a net carbon source (0.66 Mg C ha−1 with the 95% confidence interval ranging from −5.79 to 8.38 Mg C ha−1) during the 62-year period. Across the regions, simulated ∆SOC exhibited great spatial variability ranging from −108.8 to 9.89 Mg C ha−1 at the resolution of 1 km, showing significant (P < 0.05) negative correlation with baseline SOC level, temperature and rainfall, and positive correlation with pasture frequency (the duration of pasture in the rotation divided by the whole duration of the rotation) and nitrogen application rate. The uncertainty in ∆SOC and the underlying drivers were also assessed. This study presented a novel approach to efficiently predict future SOC dynamics and their uncertainty at fine resolutions, facilitating the development of site-specific management strategies for soil carbon sequestration.
17348. 题目: Changes in sorption and bioavailability of herbicides in soil amended with fresh and aged biochar
作者: Beatriz Gámiz, Pilar Velarde, Kurt A. Spokas, Rafael Celis, Lucía Cox
摘要: Knowledge of long-term pesticide behavior in biochar (BC) amended soil is still contradictory. In this work, we compared the sorption of three highly persistent and ionizable pesticides [two anionic (imazamox and picloram) and one weak base (terbuthylazine)] on both fresh and field-aged BC as well as on a soil amended with these biochars. The aging process was performed by burying the biochar at 10 cm in a silt loam soil [Upper Midwest USA (Wisconsin)] for six months. Field aged BC removed the three pesticides from solution to a higher extent (>85%) than the fresh BC (<16%). This removal was attributed to water-soluble components on the biochar. Laboratory incubation experiments demonstrated that dissipation in soil and biochar mixtures were both a function of pesticide and biochar type. The amounts of soil extractable (i.e, bioavailable) pesticide were inversely related to the extent of sorption. Similar dissipation and sorption of imazamox was observed in unamended and BC-amended soils. Terbuthylazine dissipated similarly in all treatments, but sorption increased with incubation time in the aged BC-amended soil. Conversely, picloram dissipated to a higher extent in aged BC-amended soil when compared to unamended or fresh BC-amended soil. This work demonstrates temporal variability of biochar sorption capacities due to soil exposure, which alters the efficacy and bioavailability of soil applied pesticides.
17349. 题目: Effect of UV irradiation on iodinated trihalomethane formation during post-chloramination
期刊: Water Research
作者: Ying Xia, Yi-Li Lin, Bin Xu, Chen-Yan Hu, Ze-Chen Gao, Yu-Lin Tang, Wen-Hai Chu, Tong-Cheng Cao, Nai-Yun Gao
摘要: Ultraviolet (UV) irradiation has been widely used in drinking water treatment processes, but its influence on the formation of disinfection by-products (DBPs), especially the emerging iodinated trihalomethanes (I-THMs) during post-chloramination remains unclear. This study evaluated the impact of low pressure (LP) UV treatment on the formation of I-THMs during post-chloramination through two pathways. The first pathway is through the transition of DOM structure and composition during UV-chloramination, resulting significant increase of I-THM formation with increasing UV dosage in different dissolved organic matter (DOM)-containing water (49.7% – 90.5% at 1160 mJ/cm2). With the application of excitation emission matrix-parallel factor analysis (EEM-PARAFAC), we found that I-THM formation in UV-chloraminated water correlated well with two ratios of three PARAFAC humic-like components (C3/C2 and C1/C2, R2 = 0.958 – 1.000), suggesting that the ratios of fluorescent components can be used as reliable indicators for I-THM formation. Moreover, the shift in these fluorescent components is crucial for I-THM formation during UV-chloramination. Another pathway for UV irradiation to affect I-THM formation during post-chloramination is through the transformation of iodine species. Large amounts of reactive iodine species (HOI/I2 and I3-) can be generated directly in the mixed iodine system by UV light, leading to the enhancement of iodine utilization factor (IUF) (up to 0.040) after post-chloramination. These results suggest that UV application to DOM-containing water may induce changes in organic precursors and iodine species so as to enhance I-THM formation during post-chloramination.
17350. 题目: Organic matter accumulation in the Upper Devonian Duvernay Formation, Western Canada Sedimentary Basin, from sequence stratigraphic analysis and geochemical proxies
期刊: Sedimentary Geology
作者: Nicholas B. Harris, Julia M. McMillan, Levi J. Knapp, Maria Mastalerz
摘要: We present a model for organic carbon accumulation in the Upper Devonian Duvernay Formation of the Western Canada Sedimentary Basin, relating total organic carbon (TOC) concentrations to a high resolution geochemical and organic petrologic database and comparing these to a core-based sequence stratigraphic interpretation. Many previous source rock studies have suggested that organic matter is enriched in transgressive systems tracts or at maximum flooding surfaces, an observation that is commonly attributed to an assumed relationship between water depth and oxygen levels. Our data set enables us to associate total organic matter content and organic assemblages with particular systems tracts and to examine how the organic assemblages change across the basin, tested against proxies for redox conditions and bioproductivity to relate relative sea level to specific mechanisms for organic accumulation. The Duvernay Formation comprises three third-order depositional sequences, superimposed on a second-order late transgressive systems tract and early highstand systems tract. Sequences are composed almost entirely of transgressive systems tracts and highstand systems tracts, with a lowstand systems tract only at the base of the upper cycle that marks the second-order sea level turnaround. Depositional facies generally vary from bioturbated carbonate-rich siltstones to siliceous mudstones from the platform margins to basin center. Organic petrologic analysis records predominantly amorphous organic matter and solid bitumen, with much less abundant vitrinite and inertinite. Organic matter type indicated by Rock-Eval analysis shows that in most cases, high total organic carbon (TOC) content is associated with better quality organic matter (high hydrogen index) and vice versa, indicating more reducing conditions or higher bioproductivity were responsibility for organic enrichment. However, near carbonate reefs, hydrogen index is uncorrelated with TOC, indicating that here, dilution by carbonate minerals was the primary control on organic enrichment. Across most of the basin, highest TOCs are recorded just above the second-order maximum flooding surface. Secondary peaks in TOC are recorded above the maximum flooding surface in the upper third-order cycle and in the transgressive systems tract of lower third-order cycle. Low TOC values are recorded in the lowstand systems tract and in the middle and upper third-order transgressive systems tracts almost up to the maximum flooding surfaces.Throughout much of the basin, proxies for relative sea level, restriction of water masses (Mo/TOC), redox conditions (Mo/Al and S/Fe) and bioproductivity (biogenic silica) coincide. These relationships demonstrate that organic carbon accumulation resulted from influxes of nutrient-rich upwelled water during high sea level; thus, TOC values are highest in the upper part of transgressive systems tracts and lower highstand systems tracts. Anoxia typically developed as a result of bioproductivity and enhanced organic matter accumulation but was not itself a trigger for organic sedimentation. Near carbonate reefs, however, varying sea level regulated carbonate sedimentation rate and organic matter dilution, and bioproductivity had less impact on organic matter concentrations; thus, TOC was high when carbonate deposition was low during transgressions, which forced carbonate reefs to backstep, limiting carbonate sedimentation in deeper water area.
17351. 题目: Diversity of nitrogen fixing bacterial communities in the coastal sediments of southeastern Arabian Sea (SEAS)
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Thajudeen Jabir, Yousuf Jesmi, Puthiya Veettil Vipindas, Mohamed Hatha AA
摘要: The present study depicts diversity, abundance and activity of nitrogen (N2) fixing bacterial communities in the coastal sediments of southeastern Arabian Sea (SEAS). The diversity of N2 fixing bacterial community was determined by clone library analysis of nifH gene, the culturable N2 fixing bacteria was determined by 16s rRNA and nifH gene analysis. The nitrogen fixation rate in the sediments was also estimated by acetylene reduction assay method. The nifH clone library analysis revealed that fifteen putative diazotrophs, belonging to alpha-, beta-, gamma-, delta-, epsilon- Proteobacteria and Firmicutes. The predominant operational taxonomic units (OTUs) among these were related to α-Proteobacteria (with 16% of total sequences); β-Proteobacteria (10% sequences); γ-Proteobacteria (29% sequences); δ-Proteobacteria (11% sequences); ε-Proteobacteria (21% sequences); Firmicutes (3% of sequences) and percent of some sequences remained unknown. The 16s rRNA gene based identification of culturable N2 fixing bacteria revealed the presence of seven nitrogen fixing bacterial species namely Acinetobacter johnsonii, Rhizobium rosettiformans, Bacillus megaterium, B. circulans, B. flexus, B. oceanisediminis and B. subtilis. The observed N2 fixation rate in the sediments ranged from 0.12 to 0.36 nmol N g−1 h−1. Canonical correspondence analysis (CCA) revealed significant influence of the environmental variables such as sediment type, total nitrogen (TN), total organic matter (TOM), total organic carbon (TOC), iron (Fe), manganese (Mn), total sulphur (TS), nitrite (NO2) and nitrate (NO3) on the diversity of N2 fixing bacteria and N2 fixation rate. The observations of the current study provide a better understanding of N2 cycling in coastal sediments of the SEAS and sources of fixed nitrogen.
17352. 题目: Predator-induced changes in dissolved organic carbon dynamics
作者: Romana Limberger, Julia Birtel, Hannes Peter, Núria Catalán, Daniel da Silva Farias, Rebecca J Best, Jakob Brodersen, Helmut Bürgmann, Blake Matthews
摘要: The fate of dissolved organic carbon (DOC) is partly determined by its availability to microbial degradation. Organisms at upper trophic levels could influence the bioavailability of DOC via cascading effects on primary producers and bacteria. Here we experimentally tested whether the presence of fish in aquatic food webs can indirectly affect the composition of the DOC pool. We found that fish had strong positive effects on phytoplankton biomass that affected the dynamics of DOC composition. Specifically, fish increased protein-like, algae-derived DOC mid-experiment, concurrent with the strongest fish-induced increase in phytoplankton biomass. Fish also increased bacterial abundance, altered the community composition and diversity of bacteria, and temporarily increased DOC compounds with fluorescence properties indicative of microbially-reprocessed organic matter. Overall, our experiment revealed that fish can positively influence the substrate (algae-produced DOC) and the key players (bacteria) of the microbial carbon pump. Consequently, fish could contribute to carbon sequestration by stimulating both the production of bioavailable DOC and the microbial degradation of bioavailable to persistent DOC. We propose this as a novel mechanism whereby the loss of predators from global ecosystems could alter carbon cycling. This article is protected by copyright. All rights reserved.
17353. 题目: Carbonaceous components and major ions in PM10 from the Amazonian Basin
期刊: Atmospheric Research
作者: Danilo Custodio, Célia Alves, Yendry Jomolca, Pérola de Castro Vasconcellos
摘要: Air pollution mainly resulting from deforestation and agricultural activities has become one of the major concerns in the Amazonian Basin. A detailed analysis of the PM10 chemical composition is critical for devising pollution control measures and improving climate models. In this study, daily 24-h filter samples were collected and analyzed in different sites of the Amazon Basin between 2008 and 2016 (over 200 samples). The six sampling sites were classified into two groups, one in South Amazonia, a region with strong influence of land occupation, and another in a remote forest region to the North. The high mean concentrations of PM10 and the occurrences of extreme events at the Southern site denote air pollution episodes. High correlations between the temporal trends of PM10 and primary species linked to soil re-suspension and biomass burning highlight the contribution of these sources of air pollution in the region. Significant differences between PM10 in the South and North regions were observed, for which levels of 72.6 ± 66.5 μg m−3 and 8.9 ± 4.2 μg m−3, respectively. The average concentrations of organic carbon (OC) and elemental carbon (EC) in the aerosol were 5.81 ± 4.18 μg m−3, 2.43 ± 1.65 μg m−3 and 5.17 ± 5.54 μg m−3, 0.51 ± 0.41 μg m−3, respectively, for the Southern and Northern Amazonia sampling sites. The aerosol was largely composed of inorganic species in Southern Amazonia, whose carbonaceous matter accounted for 16% of the gravimetrically measured PM10. However, in the forest region, the contribution of carbonaceous species, mainly OC, accounted for >90% and remained more constant throughout the seasons. Na+ was the dominant water soluble ion in samples from the Southern region, followed by SO4−2, NO3−, Ca2+ and K+. High levels of carbonate (CC) were also observed for these samples. For the Northern region, SO4−2 was the dominant soluble ion, followed by K+ and NH4+. Some of these species exhibited a clear seasonal trend during the study period. This study provides a better understanding of the current state of air pollution in diversified Amazon basin sites.
17354. 题目: Resilience of benthic ecosystem C-cycling to future changes in dissolved oxygen availability
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Carol M White, Clare Woulds, Greg L Cowie, Andrew Stott, Hiroshi Kitazato
摘要: In marine sediments, the availability, cycling and burial of organic carbon (OC), the size and composition of the faunal community, and the availability of dissolved oxygen (DO) are closely coupled. In light of expected expansions in marine hypoxia and of oxygen minimum zones (OMZs) in particular, it is now necessary to de-convolve DO from the frequently co-varying factors OC concentration and faunal biomass, in order to understand the effect of changing dissolved oxygen (DO) concentrations on the magnitude and pattern of biological processing of organic carbon (OC). This is especially important on the continental slope, a significant location for C cycling and burial.In this study, stable isotope tracer experiments were conducted at three sites with contrasting ambient DO concentrations of 0.5, 2.8 and 21.2 μM (at depths of 530m, 812m and 1140m respectively) on the Indian continental margin. Experiments were conducted both at ambient DO concentrations, and also, for the first time, under manipulated DO concentrations both 5% above and below ambient. The 13C label was added as algal detritus, and traced through the processes of respiration, and uptake into bacterial biomass, and into metazoans and foraminifera.Total C biological processing under ambient DO conditions was similar across all three sites, suggesting that benthic communities are well adapted to local conditions, such that OC processing is optimised even at severely hypoxic sites.DO manipulation produced changes in the pattern of OC processing by the benthic community. Oxygen manipulations in both directions resulted in decreases in total community respiration, except at the most hypoxic site. Bacterial uptake, in contrast, increased in response to all DO manipulations. Faunal 13C uptake tended to increase with increased DO. At the most hypoxic site (0.5 μM) this was attributable to increased foraminiferal activity, whereas at the most oxygenated site (21.2 μM) it was the metazoans that showed increased biomass-specific 13C uptake. Similarly, decreases in DO tended to reduce faunal 13C uptake, with metazoans disproportionately affected where they were already living at the lower end of their DO tolerance (i.e. 2.8 μM). Thus, the taxa most affected by DO manipulation depended on antecedent DO conditions. The total capacity of the benthic community to process freshly deposited OC (i.e. respiration plus uptake by bacterial and different fauna) increased following upwards manipulation of DO at the 0.5 μM site, but was not adversely affected by downwards manipulation of DO. Thus, results suggest that benthic communities possess some functional resilience, and that future expansion of marine hypoxia, while impacting benthic ecosystem structure, may not have as marked an effect on biological C processing.
17355. 题目: Comparative effect of compost and technosol enhanced with biochar on the fertility of a degraded soil
期刊: Environmental Monitoring and Assessment
作者: Rubén Forján, Alfonso Rodríguez-Vila, Beatriz Cerqueira, Emma F. Covelo, Purificación Marcet, Verónica Asensio
摘要: A large number of studies on the reclamation of mine soils focused on the problem caused by metals and did not explore in depth the issue of nutrients and vegetation after the application of organic materials. The aim of this study was to compare the effect of two treatments made of wastes and vegetated with Brassica juncea L. on the fertility of a settling pond mine soil. The first treatment was compost, biochar, and B. juncea (SCBP) and the second treatment was technosol, biochar, and B. juncea (STBP). This study evaluated the effect of the treatments on the soil nutrient concentrations and fertility conditions in the soil amendment mixtures, after 11 months of greenhouse experiment. Total carbon and nitrogen concentrations were higher in treatment SCBP than in treatment STBP after 7 months but, after 11 months, carbon concentration was higher in STBP. The used technosol could have forms of carbon more stable than compost, which could be released slower than in the compost-amended soils. Both compost and technosol mixed with biochar also increased the concentration of calcium, potassium, magnesium, and sodium in exchangeable form in the mine soil.
17356. 题目: Degradation of organic contaminants through activating bisulfite by cerium(IV): A sulfate radical-predominant oxidation process
期刊: Chemical Engineering Journal
作者: Hongyu Dong, Jie Chen, Liying Feng, Weixian Zhang, Xiaohong Guan, Timothy J. Strathmann
摘要: In this study, the activation of bisulfite by cerium(IV) (Ce(IV)/HSO3− process) is proposed for the first time to degrade organic contaminants. Experiments show that carbamazepine (CBZ), a representative recalcitrant contaminant of emerging concern, is oxidized by Ce(IV)/HSO3− treatment at pHini 3.0–7.0 when O2(aq) is present to promote HSO3− autoxidation. SO4−, HO, and SO5− were identified as active oxidants of CBZ based on the ESR spectra and the results of alcohol quenching experiments. Quantitative analysis indicates that SO4− plays a major role, while HO and other species play minor roles in the degradation of CBZ in the Ce(IV)/HSO3− process. SO4− radicals are derived from the reaction of SO5− with HSO3− and the activation of hydrogen peroxomonosulfate (HSO5−) by Ce(IV). Five degradation pathways of CBZ are proposed based on transformation products identified by UPLC-QToF-MS/MS, and proposed sites for radical attack are supported by the results of frontier electron density calculations. Elevated concentrations of Cl−, Fe(III), and humic acid (HA) inhibit CBZ degradation, while other non-target solutes have minimal effects on CBZ degradation in the Ce(IV)/HSO3− process. Finally, experiments demonstrating degradation of a suite of other organic contaminants suggests that the Ce(IV)/HSO3− system can be applied as a new advanced oxidation process for wastewater treatment.
17357. 题目: Evaluation of chemical extractants to assess metals phytoavailability in Brazilian municipal solid waste composts
期刊: Environmental Pollution
作者: Verónica Asensio, Cassio H. Abreu-Junior, Fábio César da Silva, José Carlos Chitolina
摘要: Municipal solid wastes (MSW) can be composted to become an organic fertilizer. However, besides plant nutrients, it can also contain high concentration of some toxic metals than can pollute agricultural soils, contaminate food, animals and human being. A greenhouse experiment was carried out for two purposes: i) to evaluate the concentrations of cadmium, copper, chromium, nickel, lead and zinc in four Brazilian MSW composts, and, ii) to know which is the best solution for extracting those metals in phytoavailable form from the composts. In order to evaluate the phytoavailability of metals, they were extracted with six chemical extractants: i) water, ii) 0.05 mol L−1 Ca(NO3)2, iii) 0.1 mol L−1 HCl, iv) 0.005 mol L−1 DTPA at pH 7.3, v) 0.05 mol L−1 CaCl2 and vi) Mehlich 3 solution. In addition, lettuces were cultivated as a test plant in pots containing 1.8 kg of MSW compost as substrate. Fifty-six days later, lettuce plants were harvested. New lettuces were then planted for a second cycle, and then harvested after fifty-six days. Semi-total concentration of metals in composts and total in plants was also determined through an extraction with nitric-perchloric acid. Semi–total concentration of Cd and Pb exceeded the intervention limits from Brazil in the four studied composts, and lettuce plants were polluted by those two elements. Therefore, compost made of MSW must be characterized before being used for agricultural soils. Copper and nickel in phytoavailable were effectively extracted with the strongest chelating agents used, HCl and Mehlich 3, probably because most metal is bound to organic matter in the compost. Cadmium, chromium, lead and zinc were no efficiently extracted with any of the tested extractants.
17358. 题目: Biochar application alleviates unbalanced nutrient uptake caused by N deposition in Torreya grandis trees and seedlings
期刊: Forest Ecology and Management
作者: Rui Zhang, Yuxin Zhao, Jianhong Lin, Yuanyuan Hu, Heikki Hänninen, Jiasheng Wu
摘要: Foliar nitrogen: phosphorus (N:P) ratio is a valuable indicator of nutrient limitation in forest ecosystems. The ratio is currently dramatically affected by the increasing anthropogenic N deposition in China. Biochar, a soil amendment, has profound benefits for improving soil N and P availability. However, little is known about N and P uptake and nutrient balance of plants growing on biochar-amended soils under N deposition. Here, we conducted a two-year N addition and biochar application factorial experiment with Torreya grandis trees and seedlings, and the responses of concentrations of foliar N and P and the foliar N:P ratio were evaluated. N addition alone increased foliar N concentration, but did not change foliar P concentration, and thus increased foliar N:P ratio. Biochar application alone increased concentrations of both foliar N and P but did not cause any change in the N:P ratio. Most importantly, when applying N and biochar together, the concentration of foliar P increased and the foliar N:P ratio decreased, relative to each N treatment alone. This novel result suggests that biochar application can serve as an effective forest management tool, which can not only enhance the availability of N and P nutrients, but also alleviate the imbalanced uptake of nutrients indicated by the high foliar N:P ratios under increasing N deposition.
17359. 题目: Understanding the potential for selective natural organic matter removal by ion exchange
期刊: Water Research
作者: P. Finkbeiner, J. Redman, V. Patriarca, G. Moore, B. Jefferson, P. Jarvis
摘要: Dissolved organic carbon (DOC) removal from a river water source was investigated using ion exchange (IEX), coagulation and membrane filtration. This research linked the variable charge characteristics of the organic compounds present in the source water with removal by IEX and coagulation. The raw water charge density fluctuated considerably (between 5.4 to 10.7 meq mgDOC-1) and controlled removal of the charge loading. Importantly, charge density was not correlated with the organic carbon concentration. The combined IEX and coagulation process reduced the specific DBP-FP (sDBP-FP) of the final water, with values as low as 18 μg mgDOC-1 for both haloacetic acids and trihalomethanes. IEX removed a particular fraction of NOM that 1) enhanced coagulation efficiency, providing increased removal of overall DOC; and 2) enabled coagulation to subsequently remove higher levels of specific components of NOM that have a high DBP-FP. The component of NOM removed by IEX that had a positive impact on coagulation was identified to be charged low molecular weight organic compounds of all hydrophobicity levels, resulting in a reduced specific DBP-FP compared to coagulation alone.
17360. 题目: Different responses of soil organic carbon fractions to additions of nitrogen
期刊: European Journal of Soil Science
作者: H. Chen, D. Li, W. Feng, S. Niu, A. Plante, Y. Luo, K. Wang
摘要: Carbon–nitrogen (C–N) interactions in terrestrial ecosystems regulate climate–C cycle feedbacks. How additions of N affect soil C sequestration and then regulate climate change, however, are not fully understood. Previous studies have assessed effects of N on bulk soil organic C (SOC) but have not yet carefully examined its effects on different SOC fractions, which determine how fast the N‐regulated C cycle feeds back to climate. Here we synthesized data from 36 studies with 296 observations by a meta‐analysis to evaluate the responses of SOC fractions to N additions. We hypothesized that additions of N might increase both labile and non‐labile C fractions. The SOC that was separated by density fractionation increased by 18.3% for free light fractions and by 3.0% for heavy density fractions without change in the occluded light fraction under N addition compared with the control. The SOC that was separated by aggregate fractionation increased by 4.4% for macroaggregate‐associated fractions and by 6.5% for aggregate mineral‐associated fractions without change in the microaggregate‐associated fraction under N additions. When bulk SOC was separated by chemical permanganate oxidation, the oxidizable fraction increased by 10.4%, whereas the unoxidizable fraction increased by 4.5%. The changes in different soil C fractions were related to the mechanisms of SOC stabilization. Because of the significant increases in non‐labile SOC fractions, our findings suggest that on a global scale, increased additions of N might promote SOC accumulation and slow down climate change in the long term. Our results will be useful in model development for better prediction of SOC sequestration under additions of N.