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28521. 题目: Optimization of integrated ultrasonic-Fenton system for metal removal and dewatering of anaerobically digested sludge by Box-Behnken design
文章编号: N18072006
期刊: Science of The Total Environment
作者: Jannatul Rumky, Mohamed Chaker Ncibi, Rutely C. Burgos-Castillo, Anjan Deb, Mika Sillanp??
更新时间: 2018-07-20
摘要: This study reveals the optimization of ultrasonic-Fenton process for the treatment of sludge taken from a local municipal wastewater treatment plant after anaerobic digestion. Box-Behnken design (BBD), a common approach of response surface methodology (RSM), was applied to evaluate and optimize the individual and interactive effects of three process variables, namely Fe2+ dose, H2O2 amount and sonication time for Fenton-ultrasonication method. Five dependent parameters including total organic carbon (TOC), extracellular polymeric substances (EPS), as LB-EPS and TB-EPS, and metals such as Zn and Cu were considered as the responses to investigate. According to the results of analysis of variances (ANOVA), five modelling equations are proposed that can be used to operate the design space with high regression coefficient R2. Modelling results suggest that Fenton parameters, such as: H2O2 and Fe2+ dosage had the significant effects on the overall removal of TOC; whereas, sonication improved the metal removal from the sludge sample. Based on response surface methodology, best performance is achievable under the following conditions: 36 mM of Fe2+, 320 mM H2O2 with 30 min of sonication respectively for all of the responses.
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28522. 题目: 20th century increase in body size of a hypoxia-tolerant bivalve documented by sediment cores from the northern Adriatic Sea (Gulf of Trieste)
文章编号: N18072005
期刊: Marine Pollution Bulletin
作者: Tomá? Fuksi, Adam Toma?ov?ch, Ivo Gallmetzer, Alexandra Haselmair, Martin Zuschin
更新时间: 2018-07-20
摘要: An increase in the frequency of hypoxia, mucilages, and sediment pollution occurred in the 20th century in the Adriatic Sea. To assess the effects of these impacts on bivalves, we evaluate temporal changes in size structure of the opportunistic bivalve Corbula gibba in four sediment cores that cover the past ~500 years in the northern, eutrophic part and ~10,000 years in the southern, mesotrophic part of the Gulf of Trieste. Assemblages exhibit a stable size structure during the highstand phase but shift to bimodal distributions and show a significant increase in the 95th percentile size during the 20th century. This increase in size by 2–3 mm is larger than the northward size increase associated with the transition from mesotrophic to eutrophic habitats. It coincides with increasing concentrations of total organic carbon and nitrogen, and can be related to enhanced food supply and by the tolerance of C. gibba to hypoxia.

28523. 题目: Interactions between aged biochar, fresh low molecular weight carbon and soil organic carbon after 3.5-years soil-biochar incubations
文章编号: N18072004
期刊: Geoderma
作者: Xinyu Jiang, Xiangping Tan, Jiong Cheng, Michelle L. Haddix, M. Francesca Cotrufo
更新时间: 2018-07-20
摘要: Biochar has been considered a stable additive for long-term soil carbon (C) storage and climate change mitigation. However, our understanding of the long-term interactions between aged biochar, soil organic C (SOC), and fresh low molecular weight C compounds (LMW-C) is still limited. In addition to the changes in the chemical properties of biochar and the SOC after aging, biochar stability and C sequestration potentials might be affected by the LMW-C availability. After 3.5 years of incubation, aged soils and aged soil-biochar mixtures (4 atom‰ 13C enriched grass-derived biochar, 10% addition rate) of two different soil types were used in this study, with or without the addition of LMW-C. The 13C natural abundance of the LMW-C was manipulated by mixing cane sucrose (C4) and beet sugar (C3) to make it different from or equal to the native SOC isotopic signature of the two soil types, which allowed the partitioning of the LMW-C and biochar C from the SOC in non-biochar and biochar addition treatments, respectively. We traced the 13C in the cumulative CO2, microbial biomass C (MBC), and dissolved organic C (DOC) at the beginning and the end of the 28 days of incubation. Results indicated that this aged biochar was not as effective for SOC protection as it was when fresh. Aged biochar caused significant increases in the native SOC-derived CO2 compared to non-biochar treatment during the 3.5 years of aging. Within the 28 days of incubation, aged biochar not only promoted the total CO2 emission but also did not limit the priming effect of LMW-C on native SOC mineralization. SOC-derived DOC in the aged soil-biochar mixture was significantly higher than that in the aged soil, which further increased the SOC loss. A decline in the SOC stability with aged biochar might be associated with the attenuated sorption of SOC on aged biochar, the decline in bulk density with the high biochar addition rate, and a modified microbial community. The priming of aged SOC mineralization with the addition of LMW-C might be associated with the enhanced microbial N demand in aged soils and soil-biochar mixtures. The effect of aged biochar on the soil DOC and the effect of LMW-C on the aged biochar and SOC stabilities should be further investigated in field conditions, under continuous fresh C inputs, to better evaluate the effects of biochar on long-term SOC storage.

28524. 题目: Evaluation of coastal wetland soil properties in a degrading marsh
文章编号: N18072003
期刊: Estuarine, Coastal and Shelf Science
作者: Jacob F. Berkowitz, Christine M. VanZomeren, Candice D. Piercy, John R. White
更新时间: 2018-07-20
摘要: Coastal salt marshes consist of a mosaic of vegetated and open water features, which naturally evolve and change over time. However, the rapid expansion of open water areas has been associated with marsh degradation and there is a growing need for detailed studies as coastal wetlands continue to degrade under increasing rates of sea level rise and related stressors. Yet, few studies investigate soil physicochemical and biogeochemical properties within different marsh landscape features, which could provide insight into mechanisms of the formation and expansion of open water areas. The current study compared wetland soil physical and microbial properties observed in vegetated areas with shallow open water areas called pannes, identifying a number of significant differences. Panne soils possessed lower bulk density, total C, N, P, SOC, DOC, and SRP compared with vegetated marsh areas, suggesting a shift in nutrient pools as vegetated areas transition into shallow open water features. Panne features also displayed significantly lower microbial pool sizes and processing rates than vegetated marsh soils, suggesting reduced capacity for nutrient processing in open water areas. Further, extractable NH4-N was highest in the panne soils suggesting that the absence of macrophytes decreased N uptake in open water areas. Also related to the lack of vascular plants, extractable DOC in pannes averaged less than half the concentration found in vegetated marsh areas, despite a smaller difference in soil total C. Results underscore the importance of incorporating heterogeneous landscape soil conditions when evaluating marsh degradation and considering potential restoration activities.

28525. 题目: High oxygen reduction reaction performance nitrogen-doped biochar cathode: A strategy for comprehensive utilizing nitrogen and carbon in water hyacinth
文章编号: N18072002
期刊: Bioresource Technology
作者: Jiaxiang Liang, Diyong Tang, Li Huang, Yifei Chen, Wei Ren, Jie Sun
更新时间: 2018-07-20
摘要: In this study, a novel nitrogen-doped biochar oxygen reduction reaction cathode-water hyacinth carbon, was prepared by ZnCl2 molten salt carbonization without additional nitrogen source, which displayed a high performance in electro-Fenton (E-Fenton) process. The BET result shows that water hyacinth carbon achieved a much larger specific surface area (829 m2·g-1) than non-melt salt carbonized one (323 m2·g-1) and graphite powder (28 m2·g-1). Furthermore, characterization by XPS and EIS shows that both pyridinic-N (43.24%) and graphitic-N (56.75%) existed in water hyacinth carbon and Warburg constant was only 0.051. Because of a high H2O2 producing yield 1.7 mmol·L 1 and corresponding current efficiency 81.2 ± 2.5% in molten salt carbonized water hyacinth biochar, a high kinetic constant 0.318 min-1 in DMP degradation was achieved, which was 4 times higher than graphite powder (0.076 min-1). The TOC removal achieved 86.8% in 30 min and the corresponding energy consumption reached a low level 60.15 kW·h·kgTOC-1.
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28526. 题目: Influence of soil temperature and moisture on the dissolved carbon, nitrogen, and phosphorus in organic matter entering lake ecosystems
文章编号: N18072001
期刊: Biogeochemistry
作者: Brittni L. Bertolet, Jessica R. Corman, Nora J. Casson, Stephen D. Sebestyen, Randy K. Kolka, Emily H. Stanley
更新时间: 2018-07-20
摘要: Concentrations of terrestrially derived dissolved organic matter (DOM) have been increasing in many north temperate and boreal lakes for over two decades. The concentration of DOM in lakes is influenced by a number of environmental factors, but there is still considerable debate about how the availability of terrestrial DOM, and associated dissolved nitrogen and phosphorus, may be affected by drivers of climatic change. Using experimental and observational methods, we considered how changes in soil temperature and moisture affected the composition of carbon, nitrogen, and phosphorus entering freshwater lakes. In our experiment, organic soil cores were collected from the wetland shoreline of a darkly-stained seepage lake in northern Wisconsin, USA and manipulated in laboratory with temperature and moisture treatments. During the 28-day study, soil leachate was sampled and analyzed for optical properties of DOM via UV/Vis absorbance, as well as concentrations of dissolved organic carbon (DOC), total dissolved nitrogen, and total dissolved phosphorus (TDP). DOM optical properties were particularly sensitive to moisture, with drier scenarios resulting in DOM of lower molecular weight and aromaticity. Warmer temperatures led to lower DOC and TDP concentrations. To consider long-term relationships between climate and lake chemical properties, we analyzed long-term water chemistry data from two additional Wisconsin lakes from the long term ecological research (LTER) project in a cross correlation analysis with Palmer drought severity index data. Analysis of the LTER data supported our experimental results that soil moisture has a significant effect on the quality of DOM entering lakes and that climate may significantly affect lake chemical properties. Although unexpected in terms of DOM loading for climate change scenarios, these results are consistent with patterns of decomposition in organic soils and may be attributed to an increase in soil DOM processing.

28527. 题目: Effect of modified coconut shell biochar on availability of heavy metals and biochemical characteristics of soil in multiple heavy metals contaminated soil
文章编号: N18071925
期刊: Science of The Total Environment
作者: Huakang Liu, Fei Xu, Yanluo Xie, Can Wang, Akang Zhang, Lingling Li, Heng Xu
更新时间: 2018-07-19
摘要: On account of the potential in immobilizing metals and improving soil environment, various biochar materials have been extensively applied in environmental remediation. The purpose of this experiment was to evaluate the effect of modified coconut shell biochar (MCSB) on the availability of metals and soil biological activity in multi-metals (cadmium (Cd), nickel (Ni) and zinc (Zn)) contaminated soil. MCSB was obtained from coconut shell biochar (CSB) by hydrochloric acid pickling and ultrasonication, which has significantly improved its surface functional groups and microcosmic pore structure. Sandy soil samples were incubated at 25 °C amended with MCSB or CSB by 0%, 2.5% and 5% addition for 63 days, respectively. The results showed that the acid soluble Cd, Ni and Zn decreased by 30.1%, 57.2% and 12.7%, respectively, in groups with 5% MCSB addition, which indicated MCSB had a better effect on immobilizing metals compared with CSB. In addition, higher soil biological activities were detected in different treatments compared with control (CK). Especially, the maximum bacterial number was found in 5% MCSB treatment, which increased by 149.43% compared with CK. Accordingly, our results suggested that MCSB could be used as an ameliorant to immobilize heavy metals in contaminated soils and improve soil physicochemical and biological properties.

28528. 题目: Factors influencing the ecological and human health risks of DDTs in soils and air at the isomeric and enantiomeric levels
文章编号: N18071924
期刊: Journal of Hazardous Materials
作者: Lili Niu, Chao Xu, Siyu Zhu, Hangjun Zhang, Weiping Liu
更新时间: 2018-07-19
摘要: Even though the application of dichlorodiphenyltrichloroethanes (DDTs) has been restricted for over 30 years, their ubiquitous existence still poses profound adverse impacts on ecosystem and human health. In this study, simultaneous soil and air sampling campaigns at different functional areas were conducted in warm and cold seasons. Based on the residue levels and enantiomeric signatures of DDT and its metabolites in soils and air, the parameters influencing ecological and human health risks were explored. ΣDDT concentrations in soils correlated positively with organic matter (OM) and negatively with pH, whereas atmospheric DDT levels were primarily facilitated by increased temperature. High temperature and low soil pH were also favorable for the transformation of DDT into its metabolites. The inhabitants living in agricultural regions or in areas with higher soil OM or pH < 7 were exposed to higher existing and potential health risks of soil DDTs. In addition, at lower temperatures, the existing and potential carcinogenic risks of DDTs from soil exposure were higher, whereas risks from air inhalation were lower. Health risks would be increased when considering the enantioselective toxicity of o,p’-DDT and o,p’-DDD. The results from this study could provide baseline support for risk control and avoidance of DDTs.

28529. 题目: Distribution of soil organic carbon in Wadi Al-Thulaima, Saudi Arabia: A hyper-arid habitat altered by wastewater reuse
文章编号: N18071923
期刊: CATENA
作者: Mohamed A. El-Sheikh, Salman A. Al-Oteiby, Ahmed H. Alfarhan, Damia Barcelo, Yolanda Picó, Abdulrahman A. Alatar, Saad B. Javed, Ebrahem M. Eid
更新时间: 2018-07-19
摘要: The carbon cycle is being altered as a result of human-induced changes in the Earth's system. Therefore, ecosystems such as wetlands, authentic CO2 sinks, are becoming especially important. Little information exits on the soil organic carbon (SOC) stock for the middle east-countries man-made wetlands making wadis permanent with the outflow of wastewater treatment plants. This paper presents the vertical distribution of SOC content, soil bulk density (SBD) and SOC density in soil of vegetated and bare sites in Wadi Al-Thulaima, one of the artificial wetlands in central Saudi Arabia. The mean distribution of SBD in the vegetated and bare sites increased significantly with depth. Inversely, the SOC content declined significantly with depth, from 17.1 g C kg-1 at 0–3 cm depth to 3.3 g C kg-1 at 15–18 cm depth in vegetated sites and from 4.7 g C kg-1 at 0–3 cm depth to 0.7 g C kg-1 at the 15–18 cm depth in bared sites. Vegetation significantly affected the SOC pool, the total mean SOC pool of the vegetated sites (2.0 kg C m-2) was higher than that of the bare sites (0.5 kg C m-2). Therefore, arid regions could contribute to carbon sequestration with appropriate management, which would result in the enhancement of soil quality.

28530. 题目: Pedogenic and microbial interrelations to regional climate and local topography: New insights from a climate gradient (arid to humid) along the Coastal Cordillera of Chile
文章编号: N18071922
期刊: CATENA
作者: Nadine Bernhard, Lisa-Marie Moskwa, Karsten Schmidt, Ralf A. Oeser, Felipe Aburto, Maaike Y. Bader, Karen Baumann, Friedhelm von Blanckenburg, Jens Boy, Liesbeth van den Brink, Emanuel Brucker, Burkhard Büdel, Rafaella Canessa, Michaela A. Dippold, Todd A. Ehlers, Juan P. Fuentes, Roberto Godoy, Patrick Jung, Ulf Karsten, Moritz K?ster
更新时间: 2018-07-19
摘要: The effects of climate and topography on soil physico-chemical and microbial parameters were studied along an extensive latitudinal climate gradient in the Coastal Cordillera of Chile (26°–38°S). The study sites encompass arid (Pan de Azúcar), semiarid (Santa Gracia), mediterranean (La Campana) and humid (Nahuelbuta) climates and vegetation, ranging from arid desert, dominated by biological soil crusts (biocrusts), semiarid shrubland and mediterranean sclerophyllous forest, where biocrusts are present but do have a seasonal pattern to temperate-mixed forest, where biocrusts only occur as an early pioneering development stage after disturbance. All soils originate from granitic parent materials and show very strong differences in pedogenesis intensity and soil depth. Most of the investigated physical, chemical and microbiological soil properties showed distinct trends along the climate gradient. Further, abrupt changes between the arid northernmost study site and the other semi-arid to humid sites can be shown, which indicate non-linearity and thresholds along the climate gradient. Clay and total organic carbon contents (TOC) as well as Ah horizons and solum depths increased from arid to humid climates, whereas bulk density (BD), pH values and base saturation (BS) decreased. These properties demonstrate the accumulation of organic matter, clay formation and element leaching as key-pedogenic processes with increasing humidity. However, the soils in the northern arid climate do not follow this overall latitudinal trend, because texture and BD are largely controlled by aeolian input of dust and sea salts spray followed by the formation of secondary evaporate minerals. Total soil DNA concentrations and TOC increased from arid to humid sites, while areal coverage by biocrusts exhibited an opposite trend. Relative bacterial and archaeal abundances were lower in the arid site, but for the other sites the local variability exceeds the variability along the climate gradient. Differences in soil properties between topographic positions were most pronounced at the study sites with the mediterranean and humid climate, whereas microbial abundances were independent on topography across all study sites. In general, the regional climate is the strongest controlling factor for pedogenesis and microbial parameters in soils developed from the same parent material. Topographic position along individual slopes of limited length augmented this effect only under humid conditions, where water erosion likely relocated particles and elements downward. The change from alkaline to neutral soil pH between the arid and the semi-arid site coincided with qualitative differences in soil formation as well as microbial habitats. This also reflects non-linear relationships of pedogenic and microbial processes in soils depending on climate with a sharp threshold between arid and semi-arid conditions. Therefore, the soils on the transition between arid and semi-arid conditions are especially sensitive and may be well used as indicators of long and medium-term climate changes. Concluding, the unique latitudinal precipitation gradient in the Coastal Cordillera of Chile is predestined to investigate the effects of the main soil forming factor – climate – on pedogenic processes.

28531. 题目: Rates of anthropogenic transformation of soils in the Botanical Garden of Jagiellonian University in Kraków (Poland)
文章编号: N18071921
期刊: CATENA
作者: ?ukasz Musielok, Marek Drewnik, Mateusz Stolarczyk, Magdalena Gus, Sylwia Bartkowiak, Krzysztof Ko?yczkowski, Jakub Lasota, Alicja Motak, Karolina Szczechowska, Miko?aj W?t?y
更新时间: 2018-07-19
摘要: Soils in botanical gardens play a crucial role as they condition the growth and vegetation of huge diversity of plant species on relatively small areas. Creating favourable habitats for the planted vegetation's development frequently leads to the formation of soils with thick surface horizons with a very well developed structure, rich in organic matter and nutrients, described as hortisols. Despite significant human influence, the environments of botanical gardens are often considered to be seminatural enclaves in urban areas. The main objectives of the presented paper were to explain soil cover differentiation noted across the Botanical Garden of Jagiellonian University in Kraków and determine the share of natural and anthropogenic features in the studied soils. Moreover, the usefulness of the WRB system in the evaluation of the rate of anthropogenic transformation in soils was tested. All the investigated soils showed significant evidences of anthropogenic transformations. Both digging and overbuilding with allochthonous material rich in artefacts caused disturbances in soil morphology. On the other hand, formerly intensive liming and fertilizing with organic materials has resulted in the homogenization of soil chemical properties in the studied botanical garden. No significant relationships between the spatial differentiation of soil properties and diversity of planted vegetation or time span from the area's inclusion to the botanical garden were detected. The results of the bonitation of specific soil properties not considered by the classification system (e.g. thickness of soil profile overheap) were compatible with the WRB 2015 systematic position. This confirmed good definition of actual WRB criteria for soils disturbed by human activity and undergoing natural development.

28532. 题目: Soil organic carbon stabilization changes with an altitude gradient of land cover types in central Himalaya, India
文章编号: N18071920
期刊: CATENA
作者: J. Dinakaran, Abhishek Chandra, K.P. Chamoli, Jyotishman Deka, K.S. Rao
更新时间: 2018-07-19
摘要: Soil organic carbon (SOC) stabilization in a mountain forest ecosystem is a key component of the global carbon cycle to mitigate the rising level of atmospheric carbon dioxide. We investigated the effects of different types of land cover at different altitudes on SOC stabilization in the Himalayan region, India. We chose four different land covers at different altitudes, viz., pasture land (~2500 m), mixed cover (~2200 m), chirpine (~950 m) and agricultural land (~950 m). Organic carbon (OC), total nitrogen (N), and total microbial activity (MAt) in soils up to depths of 100 cm and under different types of land cover were assessed to study the impact of vegetation cover on the storage of SOC and N. Hydrofluoric acid (HF) soluble carbon, FeDCB/AlDCB oxides and stable carbon isotopes (δ13C) were determined in the soils under different types of land cover to evaluate the amounts of mineral-associated carbon and understand the organic carbon stabilization process. The maximum SOC stock was observed under a mixed land cover (281.86 t ha-1), followed by pasture land cover (229.61 t ha-1), chirpine (182.16 t ha-1) and agricultural land cover (70.20 t ha-1) up to a depth of 100 cm. Higher SOC contents, N contents and MAt were closely linked to the surface layers (0–30 cm), while HF-soluble carbon, FeDCB and AlDCB oxides were linked to sub-surface layers (30–100 cm) of soils under different types of land cover. HF-soluble carbon was more abundant in mixed and pasture land covers compared with chirpine and agricultural land covers. The linear relationship between δ13C values and HF-soluble carbon, FeDCB/OC, δ13C, AlDCB/OC and δ13C in soils under mixed and pasture land covers confirmed that the subsurface soil constituted more decomposed carbon and its associated FeDCB/AlDCB minerals. Nevertheless, this trend was not observed in other types of land cover located at lower altitudes and might be due to the root exudates and/or mixing of young and old carbon. These results suggest that the land cover types at higher altitudes in central Himalaya may be considered as a potential sink for the sequestration of atmospheric carbon and as potential sites for the stabilization of sequestered carbon in soils. However, land cover types at lower altitudes in central Himalaya must be managed by better soil management practices to sequester and stabilize more carbon in soils.

28533. 题目: Contributions of Condensable Particulate Matter to Atmospheric Organic Aerosol over Japan
文章编号: N18071919
期刊: Environmental Science & Technology
作者: Yu Morino, Satoru Chatani, Kiyoshi Tanabe, Yuji Fujitani, Tazuko Morikawa, Katsuyuki Takahashi, Kei Sato, and Seiji Sugata
更新时间: 2018-07-19
摘要: Because emission rates of particulate matter (PM) from stationary combustion sources have been measured without dilution or cooling in Japan, condensable PM has not been included in Japanese emission inventories. In this study, we modified an emission inventory to include condensable PM from stationary combustion sources based on the recent emission surveys using a dilution method. As a result, emission rates of organic aerosol (OA) increased by a factor of 7 over Japan. Stationary combustion sources in the industrial and energy sectors became the largest contributors to OA emissions over Japan in the revised estimates (filterable-plus-condensable PM), while road transport and biomass burning were the dominant OA sources in the previous estimate (filterable PM). These results indicate that condensable PM from large combustion sources makes critical contributions to total PM2.5 emissions. Simulated contributions of condensable PM from combustion sources to atmospheric OA drastically increased around urban and industrial areas, including the Kanto region, where OA concentrations increased by factors of 2.5–6.1. Consideration of condensable PM from stationary combustion sources improved model estimates of OA in winter but caused overestimation of OA concentrations in summer. Contributions of primary and secondary OA should be further evaluated by comparing with organic tracer measurements.

28534. 题目: 13C isotopic signature and C concentration of soil density fractions illustrate reduced C allocation to subalpine grassland soil under high atmospheric N deposition
文章编号: N18071918
期刊: Soil Biology and Biochemistry
作者: Matthias Volk, Seraina Bassin, Moritz F. Lehmann, Mark G. Johnson, Christian P. Andersen
更新时间: 2018-07-19
摘要: We followed soil C fluxes in a subalpine grassland system exposed to experimentally increased atmospheric N deposition for 7 years. Earlier we found that, different from the plant productivity response, the bulk soil C stock increase was highest at the medium, not the high N input as hypothesized. This implies that a smaller N-deposition rate has a greater potential to favor the biological greenhouse gas-sink. To help elucidate the mechanisms controlling those changes in SOC in response to N deposition, we produced four soil density fractions and analyzed soil organic C concentration [SOC], as well as δ13C signatures (δ13CSOC) of SOC components. Soil respired CO2 (δ13CCO2) was analyzed to better distinguish seasonal short term dynamics from N-deposition effects and to identify the predominant substrate of soil respiration. Both at the start of the experiment and after 7 years we found a strong, negative correlation between [SOC] and δ13CSOC of the soil density fractions in the control treatment, consistent with an advanced stage of microbial processing of SOC in fractions of higher density. During the experiment the [SOC] increased in the two lighter density fractions, but decreased in the two heavier fractions, suggesting a possible priming effect that accelerated decomposition of formerly recalcitrant (heavy) organic matter pools. The seasonal pattern of soil δ13CCO2 was affected by weather and canopy development, and δ13CCO2 values for the different N treatment levels indicated that soil respiration originated primarily from the lightest density fractions. Surprisingly, [SOC] increases were significantly higher under medium N deposition in the <1.8 fraction and in bulk soil, compared to the high N treatment. Analogously, the depletion of δ13CSOC was significantly higher in the medium compared to the high N treatment in the three lighter fractions. Thus, medium N deposition favored the highest C sequestration potential, compared to the low N control and the high N treatment. Clearly, our results show that it is inappropriate to use plant productivity N response as an indicator for shifts in SOC content in grassland ecosystems. Here, isotopic techniques illustrated why atmospheric N deposition of 14 kg N ha-1 yr-1 is below, and 54 kg N ha-1 yr-1 is above a threshold that tips the balance between new, assimilative gains and respiratory losses towards a net loss of [SOC] for certain soil fractions in the subalpine grassland.

28535. 题目: Metagenomic and 13C tracing evidence for autotrophic atmospheric carbon absorption in a semiarid desert
文章编号: N18071917
期刊: Soil Biology and Biochemistry
作者: Zhen Liu, Yanfei Sun, Yuqing Zhang, Wei Feng, Zongrui Lai, Keyu Fa, Shugao Qin
更新时间: 2018-07-19
摘要: Atmospheric carbon dioxide (CO2) absorption by desert soils has received increasing interests in recent years; however, the underlying physical and chemical mechanisms are not commonly acceptable. Here, we hypothesised that autotrophic carbon fixation of soil microbes contributes to this process. To test this postulate, we investigated the genomic and biochemical potential of autotrophic carbon fixation and traced atmospheric autotrophic carbon absorption using metagenomics and 13CO2 labelling approaches in the Mu Us Desert in northern China. More than 30000 genes involved in the six carbon fixation pathways (approximately 2% of the assembled metagenomes, in relative abundance) were found in the metagenome of the desert soil, and the relative abundance for genes encoding for the reductive citrate cycle was the highest among the six pathways. The main autotrophic microbes employing the six pathways belong to Actinobacteria, Proteobacteria, Chloroflexi, Acidobacteria, Gemmatimonadetes, Firmicutes, Thaumarchaeota, Nitrospirae, Planctomycetes, and Bacteroidetes, respectively. 13CO2 labelling revealed that the contents of microbially incorporated soil organic carbon (13C-SOC) and dissolved organic carbon were 0.572–1.45 mg kg-1 and 0.290–0.914 mg kg-1, respectively. Further, the 13C-SOC correlated with the relative abundance of genes of the total six pathways, reductive citrate cycle, 3-hydroxypropionate bi-cycle, and reductive acetyl-CoA pathway. Another in situ labelling experiment showed a significant increase in δ13C of SOC, and the incorporated carbon (13C) in SOC accounted for 3.85% of total atmospheric carbon absorption. These results showed that desert soil microbes containing genetic potential for autotrophic carbon fixation spread over a broad taxonomic range, and incorporated atmospheric carbon into organic components, which contributed to atmospheric carbon absorption. Although more research is required to accurately evaluate the portions of autotrophic carbon in the amount of atmospheric carbon absorption, the biotransformation of carbon from the atmosphere to soil via autotrophic carbon fixation represents a microbial pathway for persistent atmospheric CO2 absorption in desert soils, and further implicates an important carbon biochemical cycle for carbon accumulation in oligotrophic desert soils.

28536. 题目: Nitrogen removal in pilot-scale partially saturated vertical wetlands with and without an internal source of carbon
文章编号: N18071916
期刊: Science of The Total Environment
作者: Nancy B. Martínez, Allan Tejeda, Aarón Del Toro, Martha P. Sánchez, Florentina Zurita
更新时间: 2018-07-19
摘要: The aim was to evaluate and compare total nitrogen (TN) removal in pilot-scale partially saturated vertical wetlands (PSVWs) with and without an internal solid source of organic carbon (corncob) in order to distinguish the role of nitrification-denitrification and ANAMMOX in the removal process. The height of the free-drainage zone (FDZ) was 40 cm and the saturated zone (SZ) was 30 cm in system I (SI) and system II (SII) and 40 cm in system III (SIII) and system IV (SIV). In SII and SIV, approximately 30 kg of dry, 5 cm–length corncob was added. The systems were evaluated during two periods, that is, P1 and P2. Measurements of water quality parameters including BOD5, COD, organic nitrogen (Org-N), ammonium, nitrate and nitrite were taken in the influent and effluents on a weekly basis; nitrate measurements were also taken at the interface. Measurements of pH, dissolved oxygen (DO) and oxidation-reduction potential (ORP) were taken in the SZ. The height of both SZ (40 cm vs. 30 cm in P1) and FDZ (40 vs. 25 and 30 cm in SI/SIII in P2) did not affect the efficiencies (p > 0.05) but the presence or absence of corn cob did (p < 0.05). Thus, SII and SIV were superior when compared to SI and SIII (p < 0.05) with TN average removal efficiencies of 72.9% and 73.2% in P1, and 59.8% and 64.2% in P2, respectively; showing a tendency to lower values when the biodegradable organics supplied by the corncob diminished. In SI and SIII, TN removals were 47.6% and 40.3% in P1, and 46.1% and 44.1% in P2, respectively. In SII and SIV, denitrification took place in both the lower semi-saturated part of the FDZ (probably also ANAMMOX) and SZ; whereas in SI and SIII, ANAMMOX took place in the lower semi-saturated part of the FDZ.

28537. 题目: Treatment of oil sands produced water using combined electrocoagulation and chemical coagulation techniques
文章编号: N18071915
期刊: Science of The Total Environment
作者: Laleh Shamaei, Behnam Khorshidi, Basil Perdicakis, Mohtada Sadrzadeh
更新时间: 2018-07-19
摘要: Hybrid electrocoagulation-chemical coagulation (EC-CC) process has attracted a growing attention for the removal of various types of wastewaters contaminants. In this paper, the feasibility of EC-CC technique as an alternative to conventional chemical processes for the treatment of steam assisted gravity drainage (SAGD) produced water has been systematically studied. Eight parameters, namely electrode material, cell configuration, pH and temperature of the solution, chemical coagulant dosage, intensity of the electrical current, mixing rate, and treatment time were studied. To explore the synergistic effect of the design parameters, the experimental trials were arranged using Taguchi method. Analysis of variance (ANOVA) was performed to evaluate the effect of each design parameter on the organic matter removal from the SAGD produced water. It was found that all parameters except the electrode arrangement had a significant effect on the removal efficiency of the EC-CC process. Among these parameters, the chemical coagulant and the treatment time had the most significant contribution to the efficiency by 40% and 26%, respectively. The optimum condition for the highest TOC removal efficiency (39.8%) was obtained by applying 0.34 A to Al electrode in a bipolar (BP) configuration when the pH, temperature, coagulant concentration, mixing rate, and reaction time were set to 8, 60 °C, 200 mg/L, 700 rpm, and 90 min, respectively. Moreover, a second-order polynomial regression model was proposed to predict the removal efficiency in terms of design parameters. An excellent agreement between the model predictions and experimental data was obtained with the adjusted R2 of about 99%.

28538. 题目: Determining the effects of polyaluminum chloride alkalinities and dosage treatments on various microalgal growth phases for the treatment of microalgae-laden water
文章编号: N18071914
期刊: Separation and Purification Technology
作者: Cheng Yan, Xiaoqing Song, Miao Yu, Yifei Tong, Weijun Zhang
更新时间: 2018-07-19
摘要: Harmful algal blooms have become critical threats to human health as they have occurred with increasing frequency and intensity in various water bodies. In the People’s Republic of China, thousands of people are exposed to water bodies heavily contaminated with microalga Microcystis aeruginosa and thus at grave risk of microcystin poisoning. This study investigated the characteristics of extracellular organic matters (EOMs), floc morphology, and microcystin in each microalgal growth phase for the treatment of microalgae-laden water. The characterization was performed under different alkalinities and dosage treatments of polyaluminum chloride (PAC). Results suggested fulvic-like and humic-like acids, C=C, and unsaturated aldehyde ketones were present in the supernatant liquor and dissolved EOM (dEOM) solution under logarithmic and stationary phase treatments for EOM. However, the same components along with aromatic protein and amidogen were detected in the supernatant liquor and dEOM solution under the decline phase treatments. The EOM of the supernatant liquor and dEOM solution nearly resembled willmigerl, which was different from bound extracellular organic matter (bEOM) in the three growth phases. Nonetheless, the highest particle size and most compact and roughest flocs were observed in the stationary phase. Meanwhile, no significant difference (P>0.05) was observed among the microcystin concentrations of microalgal cells before and after coagulation, although the concentrations increased after the coagulating treatment. Therefore, coagulation pH of 2.0 and 50 mg L-1 dose of PAC was a good practical application to treat microalgae laden water at the stationary growth phase.

28539. 题目: Polyvinyl chloride (PVC) ultrafiltration membrane fouling and defouling behavior: EDLVO theory and interface adhesion force analysis
文章编号: N18071913
期刊: Journal of Membrane Science
作者: Wanyi Fu, Lan Wang, Fangjuan Chen, Xuezhi Zhang, Wen Zhang
更新时间: 2018-07-19
摘要: To unravel fouling and defouling mechanisms of protein, saccharides and natural organic matters (NOM) on polymeric membrane during filtration, this study investigated filtration characteristics on polyvinyl chloride (PVC) ultrafiltration membranes with bovine serum albumin, dextran, humic acid as model foulants. Membrane fouling and defouling performances were analyzed through monitoring the flux decline during filtration and flux recovery during physical backwash. Physico-chemical properties (e.g., hydrophobicity and surface charge) of PVC membrane and foulants were characterized, which were used in the extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) theory to calculate the interaction energies between membrane-foulant and foulant-foulant. The results showed that at the later filtration stages the fouling rate was strongly correlated with the deposition rate, which was determined by the interaction energy profile calculated by EDLVO. Moreover, the adhesion forces of membrane–foulant and foulant–foulant were further measured by atomic force microscopy (AFM) with modified colloidal probes. A positive correlation (R2 = 0.845) between particle detachment rate (determined by adhesion force) and defouling rate was developed for BSA and HA foulants that led to cake layer formation. By contrast, dextran defouling rate was off this correlation as dextran partially clogged membrane pores due to its smaller size.

28540. 题目: Alteration of organic matter during remediation of acid sulfate soils
文章编号: N18071912
期刊: Geoderma
作者: Angelika K?lbl, Petra Marschner, Luke Mosley, Rob Fitzpatrick, Ingrid K?gel-Knabner
更新时间: 2018-07-19
摘要: When acid sulfate soils with hypersulfidic material dry, oxidation of pyrite can cause strong acidification due to formation of sulfuric (pH < 4) material. Re-saturation of acid sulfate soils containing sulfuric material can lead to re-formation of pyrite and pH increase through activity of sulfate reducing bacteria, which require available organic carbon (OC). In the Lower River Murray region in Australia, a clayey acid sulfate soil had acidified during the severe “Millennium” drought between 2007 and early 2010. We investigated why it has not recovered for over a decade after being reflooded. We hypothesized that the low quality and availability of OC limits the activity of sulfate reducing bacteria. A long-term anoxic incubation experiment was conducted to test if OC additions can help to overcome OC limitation. Small-scale incubation vessels were used, allowing investigating general biochemical phenomena under controlled laboratory conditions. Pre-incubated acid sulfate soil with sulfuric material (approx. pH 3.5) was submerged and pre-adjusted to pH 5.0. We used different rates of wheat straw and cattle manure application to test different organic matter quantities and qualities. Both substrates were added in two portions, at the beginning of the experiment and after 190 days. With every addition, we added two different amounts of organic matter (2 mg g 1 soil and 9 mg g 1 soil), equivalent to approx. 10% and 50% of the native soil OC content. A control treatment without OC addition was also included. CO2 production as well as redox and pH values were monitored weekly over a year. At the start and the end of incubation, we determined OC concentrations and the proportion of available, non mineral-associated OC. OC composition was analyzed by solid-state 13C NMR spectroscopy to assess its chemical degradation. The pH values increased rapidly in treatments with high OC supply, reaching pH ≥ 6.0 within 3 weeks after the second OC addition. Treatments with low OC additions showed slower pH increases, reaching values between pH 5.5 and 6.0 after one year. The control treatment had pH values <5.0 at the end of the experiment. After one year of anoxic incubation, the control treatment lost 10% of the native OC. Treatments with OC additions lost between 13 and 19% of total OC (native + added OC), with higher percentage loss in treatments with high OC additions. Highest losses were observed for the non mineral-associated OC fraction (up to 69% in treatments with high OC additions), with up to 20% being converted to the mineral-associated OC. OC composition changed little compared to the start of the experiment, showing slightly reduced proportions of carbohydrates (≤10% loss) and slightly higher proportions of lipids and lignin. Best remediation success was achieved by adding 50% of the native soil OC as wheat straw, resulting in fast pH neutralization, strongly reducing conditions, and decreased sulfur and iron concentrations in the soil solution. However, the amount of bioavailable OC was reduced to one third after the incubation period. Repeated OC addition is therefore recommended to keep the total amount of bioavailable, undecomposed plant residues high and to ensure long-term remediation success.