14221. 题目: Removal of nitrogen from low pollution water by long-term operation of an integrated vertical-flow constructed wetland: Performance and mechanism
期刊: Science of The Total Environment
作者: Ying Liu, Xiaohui Liu, Ke Li, Shaoyong Lu, Xiaochun Guo, Jian Zhang, Beidou Xi
摘要: The efficiency of nitrogen removal and its mechanism, aquatic organism distribution characteristics and regeneration capability of zeolite from an integrated vertical-flow constructed wetland (IVFCW) for low pollution water treatment were evaluated after steady and continuous operation for eight years. After running for eight years, better than average COD and NH4+-N removal were observed in the IVFCW. The NH4+-N removal rate in this system was controlled by ammoxidation and adsorption and ion exchange of zeolite. The low total nitrogen (TN) removal efficiency was due to NO3−-N accumulation and zeolite desorption. In addition, this phenomenon indicated that because of poor organic carbon sources, nitrification was stronger than denitrification, consistent with the distribution of the functional genes for nitrification and denitrification. The biological activity in this system was abundant, especially that of spirogyra and navicula. The saturated adsorption capacity of zeolite was as high as 1.35 mg g−1 with a desorption rate of <20%. There were no obvious differences among the effects of aeration, water cleaning, drained reoxygenation and steam stripping for zeolite regeneration (adsorption capacity of >50%). However, the drained reoxygenation performance of was better due to zero energy consumption and regeneration in situ.
14222. 题目: Pharmaceuticals and pesticides in secondary effluent wastewater: Identification and enhanced removal by acid-activated ferrate(VI)
期刊: Water Research
作者: Kyriakos Manoli, Lucas M. Morrison, Mark W. Sumarah, George Nakhla, Ajay K. Ray, Virender K. Sharma
摘要: The emergence of resistance to antibacterial drugs and pesticides in water is unprecedented. This may have adverse consequences to human health and ecological systems. This paper first sought the identification of a wide range of pharmaceuticals and pesticides in two secondary effluent wastewaters (SEW) of different quality characteristics, followed by their removal by ferrate(VI) (Fe(VI), FeO42-). Screening for 22 pharmaceuticals and 32 pesticides, revealed that 11 pharmaceuticals and 3 pesticides in SEW of plant A, and 14 pharmaceuticals and 5 pesticides in SEW of plant B were present at concentrations higher than the liquid chromatography mass spectrometry method quantitation limit. The concentrations of pharmaceuticals and pesticides ranged from 0.15 ng/L-413.03 ng/L. Investigation of the removal of these pharmaceuticals and pesticides by Fe(VI) showed that some had recalcitrant activity towards their oxidation. Acid-activated Fe(VI) resulted in enhanced oxidation (12.6%-56.2% degradation efficiency) of 6 and 7 pharmaceuticals in SEW of plant A and plant B, respectively, at a shorter time than Fe(VI) without activation (i.e. 3-5 min versus 15-30 min). The degradation of 1 and 3 pesticides in SEW of plant A and plant B respectively, has also been enhanced by activating Fe(VI) (13.8%-86.2% degradation efficiency). Results on testing of organic matter characterization of treated SEW with and without acid-activated Fe(VI) treatment are also presented. Acid-activated Fe(VI) treatment has potential in enhancing the removal of micropollutants in real wastewater.
14223. 题目: Chemical Oceanography of the Arabian Gulf
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Faiza Al-Yamani, S.W.A. Naqvi
摘要: Most of the available information about basin-wide chemical processes in the Arabian Gulf is based on observations made during the expeditions of the Research Vessels Meteor (1965), Atlantis II (1977) and Umitaka-Maru (1993–1994) with the ongoing national programs in shallow territorial waters largely focusing on local environmental issues. Despite the acute paucity of data, it is clear that the Gulf's biogeochemistry and ecosystems are experiencing massive changes resulting from human activities. The two key components of these changes are a reduction in river runoff that has caused a large increase in salinity in the northern part of the Gulf, and an increase in nutrient loading largely through sewage discharge from the sprawling urban centers along the coasts. The change from a pristine, oligotrophic state to a human-perturbed, eutrophic system is not so clear from the long-term nutrient and chlorophyll trends, presumably because of rapid uptake of nutrients by the phytoplankton and consumption of the photosynthesized organic matter by the heterotrophs. However, eutrophication has led to large increases in the frequency and intensity of phytoplankton blooms since the 1990s. It may also account for the high total organic carbon (TOC) concentration in the water column and the recent development of summer-time hypoxia in near-bottom waters of the central Gulf, which have important implications for the future evolution of the oxygen minimum zone of the North-Western Indian Ocean. The high atmospheric dust deposition maintains high dissolved trace metal concentrations in seawater. There are several intriguing and hitherto unresolved aspects of nutrient budgets in the Arabian Gulf, mostly arising from the differences between nutrient concentrations in the inflowing and outflowing currents, highlighting the unknown roles and strengths of the local sources and sinks. However, even though the latter are being modified by human activities, the N:P concentrations in the deeper part of the Gulf vary in Redfieldian proportion. An interesting feature of nitrogen biogeochemistry in the Gulf is the accumulation of high nitrite in the euphotic zone. The relative contributions of nitrification and assimilatory nitrate reduction by phytoplankton to the nitrite build up are not known. Dissolved nitrous oxide concentrations are slightly above saturation. The extremely high thermohaline variability and biogenic carbonate production within the Gulf also make inorganic carbon cycling in the Gulf quite unusual. However, this remains one of the least studied topics of research in the Gulf. Another subject of disproportionately high significance is benthic biogeochemistry due to shallow depths and high temperatures within the Gulf. Since the small-sized Gulf is shared by eight countries, active regional cooperation is essential to understand its processes and come up with measures to address the serious threats faced by its biogeochemistry and ecosystem from human activities.
14224. 题目: Lowest Elevation of Plant Growth and Soil Characteristics in Natural Drawdown Areas in the Jiangjin Section of the Yangtze River
作者: Mingzhi Liu, Yuanyuan Liu, Bo Zeng, Hangang Niu, Songping Liu, Xiaojiao Pan, Jiaojiao Xie, Shaohua Shi, Feng Lin
摘要: This study explores the effect of flooding on the vegetation and soil of the water level fluctuation zone (WLFZ) in the Jiangjin section of the Yangtze River. The vegetation community and physical and chemical soil properties at water level elevations of 188–200 m above mean sea level (a.m.s.l) were studied using the belt transect method and the quadrat method when the section was at its lowest water level, with the nonfluctuating zone above 200 m a.m.s.l as a control. Perennial and flood-resistant species, such as Phalaris arundinacea, were dominant in the herbaceous community from 193 to 200 m, and the apparent lowest elevation of plant growth was from 188 to 193 m. From 193 to 206 m, soil bulk density decreased with increasing elevation but increased with soil layer depth. The soil nitrogen (N), phosphorus (P) and potassium (K) in the nonfluctuating zone were higher than those in the WLFZ zone. However, the soil organic matter from 193 to 200 m was higher than that in the nonfluctuating zone. The soil N, P and K from 188.06 to 188.09 m were higher than those from 188.3 to 189 m, except for hydrolysable N. The lowest elevation of plant growth did not result from a lack of soil fertility due to long-term submergence.
14225. 题目: Benthic hotspots in the pelagic zone: Light and phosphate availability alter aggregates of microalgae and suspended particles in a shallow turbid lake
期刊: Limnology and Oceanography
作者: Bregje W. Brinkmann, J. Arie Vonk, Sebastiaan A. M. van Beusekom, Maria Ibanez, Miguel A. de Lucas Pardo, Ruurd Noordhuis, Erik M. M. Manders, Jolanda M. H. Verspagen, Harm G. van der Geest
摘要: Limnetic aggregates from a turbid delta lake with low dissolved nutrient availability were studied in relation to light and dissolved nutrient availability. Quick light‐attenuation restricts the euphotic zone to the top surface layer of the water column, whereas mineralization processes in the sediment specifically provide dissolved nutrients near the lakebed. This suggests neither the pelagic nor the benthic zone provides the combination of resources required for microalgal growth. Nutrient mineralization in aggregates could bridge this apparent spatial gap in light and nutrients by providing dissolved nutrients in the euphotic zone, promoting microalgal growth. To explore this, aggregates obtained from turbid and phosphate‐limited lake Markermeer (The Netherlands) were exposed in the laboratory to phosphate‐replete and phosphate depleted conditions, at high‐light and low‐light availability. Confocal microscopy revealed that aggregates exhibited alkaline phosphatase activity and contained microalgae, other microbes, and extracellular polymeric substances. The spatial distribution of the phosphatase activity in aggregates largely matched that of chlorophyll a (Chl a)‐lacking microbes, suggesting that these microbes were responsible for the activity. Colorimetric quantification revealed that aggregates exhibited over 1.9‐fold higher phosphatase activity than surrounding water. Two‐day exposure to different light and phosphate availabilities affected aggregate composition. Phosphate depleted conditions resulted in more Chl a‐lacking microbes and more phosphatase activity than phosphate‐replete conditions. Low‐light intensity resulted in higher abundance of extracellular polymeric substances than high‐light intensity. In contrast to aggregates from deep stratified systems, Markermeer aggregates were not enriched with dissolved phosphorus. These results suggest that P‐cycling in aggregates differs between shallow turbid and deep stratified ecosystems.
14226. 题目: Abundance and characteristics of microplastics in the mangrove sediment of the semi-enclosed Maowei Sea of the south China sea: New implications for location, rhizosphere, and sediment compositions
期刊: Environmental Pollution
作者: Ruilong Li, Linlin Zhang, Baoming Xue, Yinghui Wang
摘要: Microplastic pollution of intertidal mangrove ecosystems is receiving growing attention, and scientists suspect that the microplastic pollution of semi-enclosed seas is significantly different from that of other coastal types because of their unique geographical features. However, data on the distributions and characteristics of microplastics in the mangrove sediment of semi-enclosed seas are very limited. This study selected the Maowei Sea, a typical semi-enclosed sea, as its representative study site. The analysis revealed that the microplastic abundances in the river estuaries were much lower than those at the oceanic entrance zones, with values ranging from 520 ± 8 to 940 ± 17 items/kg. Polyethylene (PE)/polypropylene (PP)/polystyrene (PS), white/transparent, and <1 mm were the dominant type, colour, and size of the microplastics, respectively, in the observed mangrove sediments. Moreover, some other factors, including the rhizosphere/non-rhizosphere and the proportion of organic matter, codetermined the distribution and characteristics of microplastics. Specifically: (1) the percentage of colorful microplastics were higher in the rhizosphere due to the microbial activities and (2) positive linear relationships were found between the pore volume (PV) values of the free particulate organic matter (FPOM), occluded particulate organic matter (OPOM) (1.6–2.0 g/cm3 and >2.0 g/cm3), and the abundance of very small microplastics (<1 mm).
14227. 题目: The impact of wildfire on microbial C:N:P stoichiometry and the fungal-to-bacterial ratio in permafrost soil
作者: Xuan Zhou, Hui Sun, Jukka Pumpanen, Outi-Maaria Sietiö, Jussi Heinonsalo, Kajar Köster, Frank Berninger
摘要: Wildfires thaw near-surface permafrost soils in the boreal forest, making previously frozen organic matter available to microbes. The short-term microbial stoichiometric dynamics following a wildfire are critical to understanding the soil element variations in thawing permafrost. Thus, we selected a boreal wildfire chronosequence in a region of continuous permafrost, where the last wildfire occurred 3, 25, 46, and > 100 years ago (set as the control) to explore the impact of wildfire on the soil chemistry, soil microbial stoichiometry, and the fungal-to-bacterial gene ratio (F:B ratio). We observed the microbial biomass C:N:P ratio remained constant in distinct age classes indicating that microbes are homeostatic in relation to stoichiometric ratios. The microbial C:N ratios were independent of the shifts in the fungal-to-bacterial ratio when C:N exceeded 12. Wildfire-induced reduction in vegetation biomass positively affected the fungal, but not the bacterial, gene copy number. The decline in microbial biomass C, N, and P following a fire, primarily resulted from a lack of soil available C and nutrients. Wildfire affected neither the microbial biomass nor the F:B ratios at a soil depth of 30 cm. We conclude that microbial stoichiometry does not always respond to changes in the fungal-to-bacterial ratio and that wildfire-induced permafrost thawing does not accelerate microbial respiration.
14228. 题目: Soil CO 2 emission, microbial biomass, and microbial respiration of woody and grassy areas in Moscow (Russia)
期刊: Journal of Soils and Sediments
作者: Sofia Sushko, Nadezhda Ananyeva, Kristina Ivashchenko, Vyacheslav Vasenev, Valeriy Kudeyarov
摘要: Purpose: Urbanization significantly changes the carbon balance of the terrestrial ecosystem, an important component of which is soil CO2 emission. One of the main sources of soil CO2 emission is microbial decomposition of soil organic matter. In this regard, we hypothesized a relationship between soil CO2 emission and soil microbial properties (biomass, respiratory activity) in Moscow megapolis areas. Materials and methods: Soil CO2 emission was measured monthly (May–October) from the surface (or soil respiration, RS) and after the sequential removal of the two top 10-cm soil layers at woody (forest park, public garden) and grassy (grassland, arable) areas. Soil temperature (ST) and soil water content were recorded in 0–10-, 10–20-, and 20–30-cm layers, from which samples were taken to measure microbial biomass carbon (Cmic) and basal (microbial) respiration (BR). Results and discussion: RS ranged from 0.3 to 14.7 μmol СО2 m−2 s−1, with average values of 1.0, 5.4, 7.5, and 8.8 μmol СО2 m−2 s−1 for arable, forest park, public garden, and grassland, respectively. Removing the topsoil layer in woody areas resulted in higher CO2 release to the atmosphere than in grassy ones. Topsoil Cmic was on average 110, 331, 517, and 549 μg C g−1 and BR was 0.42, 0.87, 0.47, and 0.92 μg C-СО2 g−1 h−1 for arable, forest park, public garden, and grassland, respectively. Subsoil Cmic and BR were 1.5–3 times and 30–62% lower than in topsoil. RS in woody areas was more strongly dependent on ST than in grassy areas. Strong positive correlation between RS and topsoil Сmic and Corg (R2 = 0.98–0.99) was found. Conclusions: The RS of different Moscow’s areas might be predicted on the base of soil Cmic or Corg experimental data.
14229. 题目: Impacts of maricultural activities on characteristics of dissolved organic carbon and nutrients in a typical raft-culture area of the Yellow Sea, North China
期刊: Marine Pollution Bulletin
作者: Hongmei Li, Yongyu Zhang, Yantao Liang, Jing Chen, Yucheng Zhu, Yuting Zhao, Nianzhi Jiao
摘要: Ailian Bay is an integrated multi-trophic aquaculture bay with approximately 60 years maricultural activities in North China. The floating raft culture of kelp and shellfish is the unique mariculture mode. In this study, the impacts of intensive mariculture activities on seasonal carbon and nutrient dynamics in Ailian Bay were systematically analysed via seasonal surveys between 2015 and 2016. The dissolved inorganic nitrogen and silicon reached the maximum concentrations during summer, which were mainly attributed to the release of shellfish metabolic by-products and their filter-feeding effects on diatoms. Dissolved organic carbon (DOC) concentrations were significantly elevated when kelps were rotting in summer and kelp seeding were occurring in winter. Meanwhile, the fluorescence intensity of humic-like chromophoric dissolved organic matter was relatively high in kelp mariculture zone. As most humic-like DOC are potentially refractory substances, we propose that kelp mariculture would contribute importantly to the increase of refractory DOC pool in oceans.
14230. 题目: Rhizosphere interactions between earthworms and arbuscular mycorrhizal fungi increase nutrient availability and plant growth in the desertification soils
期刊: Soil and Tillage Research
作者: Yanmei Li, Shaojun Wang, Mei Lu, Zhe Zhang, Minkun Chen, Shaohui Li, Run Cao
摘要: Earthworms (E) and arbuscular mycorrhizal fungi (AM) as the key components of belowground organisms can form highly complex interactions in soil food web. However, little is known about the direction and power of interactive effects on plant growth and soil fertility in nutrient-limited soils. The objectives aimed to explore the interaction of AM (Claroideoglomus etunicatum) and E (Amynthas divergens yunnanensis) and its effecting mechanism on the plant (Photinia fraseri Dress) growth and nutrient availability in the desertification soils in Karst area. A 2 × 2 factor block design was completely randomly arranged for the treatments in a pot experiment. The four treatments were no E and AM, E inoculation, AM inoculation and inoculations with both E and AM. We confirmed the hypotheses tested about a positive effect of combined inoculations and a more pronounced increase in the plant height (12.5–13.4%), base diameter (24–27%), root colonization (50%) and hyphal length density (312%) compared with separate inoculation. Whereas the inoculation with E or AM had an effect only on the plant height, and AM inoculation only on the hyphal length density. The combined inoculations resulted in a greater reduce in soil pH and a higher increase in soil organic matter and readily oxidizable organic carbon. The effect of combined inoculations on the growth of base diameter, root mycorrhizal colonization and hyphal length density was closely associated with the increase in soil organic matter and soil readily oxidizable organic carbon. In contrast, the effect of separate inoculation on plant height was related with the increase in pH, total nitrogen and phosphorus, plant available nitrogen and phosphorus in soils. Earthworms and AM fungi can create different nutritional niches for plants: E had greater increase in N availability, while AM fungi in P availability. Therefore, we conclude that the combined effects have a greater potential in increasing plant growth, through the complementary and interactive mechanisms of E and AM on modifying nutrient availability in the nutrient-poor soils in Karst stony desertification land.
14231. 题目: Soil compaction effects on litter decomposition in an arable field: Implications for management of crop residues and headlands
期刊: Applied Soil Ecology
作者: Lea Carlesso, Andrew Beadle, Samantha M. Cook, Jess Evans, Graham Hartwell, Karl Ritz, Debbie Sparkes, Lianhai Wu, Phil J. Murray
摘要: Soil compaction is a major threat to agricultural soils. Heavy machinery is responsible for damaging soil chemical, physical and biological properties. Among these, organic matter decomposition, which is predominantly mediated by the soil biota, is a necessary process since it underpins nutrient cycling and the provision of plant nutrients. Understanding factors which impact the functionality of the biota is therefore necessary to improve agricultural practices. To better understand the effects of compaction on the soil system, we determined the effects of soil bulk density and soil penetration resistance on the decomposition rates of litter in three distinct field zones: a grass margin, sown at the edge of the field adjacent to the crop, tramlines in the crop:margin interface, and crop. Three litters of different quality (ryegrass, straw residues and mixed litter) were buried for 1, 2, 4 and 6 months in litter bags comprising two different mesh sizes (0.02 and 2 mm). Bulk density and soil penetration resistance were greater in the compacted tramline than in the margin or the crop. The greatest amount of litter remaining in the bags after 6 months was found in the tramline, and the least in the grass margin. Differences between treatments increased with burial time. No significant differences in mass loss between the two mesh sizes was detected before the fourth month, implying that microbial activities were the main processes involved in the early stages of decomposition. Decomposition in the tramline was clearly affected by the degradation of soil structure due to heavy compaction. This study shows that soil conditions at the edges of arable fields affect major soil processes such as decomposition. It also reveals the potential to mitigate soil degradation by managing the headland, the crop residues and the machinery traffic in the field.
14232. 题目: Carbonization and ball milling on the enhancement of Pb(II) adsorption by wheat straw: Competitive effects of ion exchange and precipitation
期刊: Bioresource Technology
作者: Yaoyao Cao, Weihua Xiao, Guanghui Shen, Guanya Ji, Yang Zhang, Chongfeng Gao, Lujia Han
摘要: Straw biomass is a promising adsorbent for the removal of heavy metals. To improve its Pb(II) adsorption capacity and elucidate competition of adsorption mechanisms (e.g., ion exchange and precipitation), the Pb(II) adsorption mechanisms for wheat straw (WS-CK), wheat straw-biochar (WS-BC), and ball-milled wheat straw-biochar (WS-BC+BM) samples were investigated in detail by EDX, XRD, and FTIR. The results implied that the Pb(II) adsorption capacities at an adsorbent dosage of 0.2 g/L onto WS-CK, WS-BC, and WS-BC+BM were 46.33, 119.55, and 134.68 mg/g, respectively. This indicates that carbonization and ball milling are efficient techniques for improving the adsorption capacity of Pb(II) onto wheat straw, as WS-BC and WS-BC+BM exhibited adsorption capacities comparable to other commonly used bioadsorbents. Carbonization contributed significantly to precipitation (e.g., PbCO3 and Pb3(CO3)2(OH)2). Furthermore, competition existed between ion exchange and precipitation during the Pb(II) adsorption process. With relative lower adsorbent dosages, carbonization and ball milling enhanced ion exchange capacity.
14233. 题目: Adsorption characteristics of ammonium ion onto hydrous biochars in dilute aqueous solutions
期刊: Bioresource Technology
作者: Ruemei Fan, Ching-lung Chen, Jui-yen Lin, Jing-hua Tzeng, Chih-pin Huang, Chengdi Dong, C.P. Huang
摘要: This research aims at studying the characteristics of ammonium adsorption onto hydrous bamboo biochar. Results showed that pH played the most important role in ammonium adsorption. High ionic strength enhanced the ammonium adsorption capacity of bamboo biochar. Ammonium adsorption was exothermic and spontaneous. FTIR results showed shift, disappearance, or appearance of specific functional groups on the bamboo biochar surface. Surface precipitation and complex formation contributed to the adsorption of ammonium onto hydrous bamboo biochar. Biochar can be an effective adsorbate for ammonium removal from water. Additionally, the formation of nitrogen containing precipitates on the biochar surface, potentially, leads to the in-situ synthesis of slow-release fertilizer.
14234. 题目: Sedimentary and elemental dynamics as a function of the elevation profile in a semi-arid mangrove toposequence
作者: Carine Bourgeois, Andrea C. Alfaro, Audrey Leopold, Rémi Andréoli, Estelle Bisson, Anne Desnues, Jean Louis Duprey, Cyril Marchand
摘要: The effect of elevation and seasonal variations on the elemental status of sediments was investigated along a semi-arid mangrove profile in the Heart of Voh, New Caledonia. As other mangroves in the world, this mangrove site experienced an increase of tidal range that led to the recent colonisation of salt flats at the highest elevations landward by Avicennia marina (Forsk.) Vierh subsp. australasica (Walp.) J. Everett. This young Avicennia stand was compared with an old Avicennia stand at lower elevations on its edge. Down the elevation profile, the sediment properties of a short Rhizophora stylosa Griff stand were compared with a taller Rhizophora stand seaward that experienced longer immersion periods. Our results show that centimetre-scale variation in elevation significantly affects all sediment properties along the semi-arid profile and induces a strong seasonal variation in reduction potential and pH at high elevations over the year. We suggest that during the dry season, the oxygenated sediments enhanced the oxidation of organic matter (OM), which led to the dissolution of Fe-S compounds and the subsequent acidification of the sediments. This in turn induced a loss of metal content (Fe, Cu Ni, Mn) compared to the sediments at lower elevation. Moreover, our results show that the accumulation of OM during the colonisation phase by Avicennia coincided with higher water content and higher total and exchangeable concentrations of N, P, Mg and K within the surface sediments than in the old Avicennia stand. The tall Rhizophora stand at the borders of the channel was characterized by an increase in elevation, denser sediments and a depletion of elements in several horizons of the depth profile compared to the short Rhizophora landward. These results provide a better understanding of i) the impact of elevation differences on major and minor elements in a semi-arid mangrove ecosystem, and ii) the changes of sediment properties mediated by a pioneer species within the early phase of succession in hypersaline mangroves.
14235. 题目: C-modified TiO2 using lignin as carbon precursor for the solar photocatalytic degradation of acetaminophen
期刊: Chemical Engineering Journal
作者: A. Gómez-Avilés, M. Peñas-Garzón, J. Bedia, J.J. Rodriguez, C. Belver
摘要: This work deals with the removal of emerging pollutants in water by solar light with photocatalysts based on C-modified TiO2 materials, using lignin as carbonaceous precursor and acetaminophen as target compound. This provides a way of lignin valorization, a large-scale by-product from the pulp and paper industry and the future lignocellulosic biorefinery. Several C-modified TiO2 materials were prepared following a hydrothermal method and a further thermal treatment in different atmospheres (air or nitrogen). The resulting catalysts were fully characterized by different techniques to learn on the structure-photoactivity relation. Complete acetaminophen conversion was achieved after only 1 h under solar irradiation with the photocatalysts calcinated under air atmosphere (C-Ti-400air and C-Ti-500air), being OH and O2− radicals the main reactive oxygen species involved in the acetaminophen photodegradation. These photocatalysts yielded the highest activity, which was maintained upon four successive uses. These findings are discussed with a focus on the development of active photocatalysts under solar light for the photodegradation of emerging pollutants.
14236. 题目: Effect of UV/TiO2 pretreatment on fouling alleviation and mechanisms of fouling development in a cross-flow filtration process using a ceramic UF membrane
期刊: Chemical Engineering Journal
作者: Tao Yang, Houfeng Xiong, Fen Liu, Qiyong Yang, Bingjie Xu, Changchao Zhan
摘要: In the application of ultrafiltration (UF) for removal of natural organic matter (NOM) from water, membrane fouling has always been considered a big issue. The influence of UV/TiO2 photocatalysis as pretreatment to mitigate cross-flow ceramic UF membrane fouling caused by humic acid (HA) and the involved mechanisms of fouling development were investigated. The characterization of dissolved organic carbon (DOC), specific ultraviolet absorbance (SUVA), excitation-emission matrix (EEM), molecular weight (MW), hydrophilicity, fouling resistance, scanning electron microscopy (SEM) and model fitting using Hermia blocking models were performed. The dominant membrane fouling patterns can be predicated by the initial intermediate pore blocking, transition fouling and the final stage of limited cake growth. With extended UV/TiO2 pretreatment time, a significant reduction of cake filtration coefficients and a slight decrease in pore blocking coefficients were observed. Longer UV/TiO2 pretreatment achieved the remarkable effect of reversible fouling elimination as a result of reaching the final stage of limited cake growth earlier and aggregation forming a porous cake layer by TiO2 particles mixed with more hydrophilic (HPI) and high MW (>50 kDa) humic-like substances. However, photocatalytic pretreatment exhibited a slight effect on the mitigation of irreversible fouling that was mainly dominated by HPI fractions, especially tryptophan-like protein (5–50 kDa) organics attaching to and/or blocking the membrane pores.
14237. 题目: Attribution of crop yield responses to application of organic amendments: A critical review
期刊: Soil and Tillage Research
作者: Corinne Celestina, James R. Hunt, Peter W.G. Sale, Ashley E. Franks
摘要: Soil organic matter affects soil physical, chemical and biological properties and is thus agronomically important because these factors affect crop yields. Organic amendments such as manures, composts and plant residues are frequently used in crop production systems as alternatives to inorganic fertilizers, to restore degraded soils and ameliorate physicochemical constraints. Crop yield responses to the application of organic amendments can be due to the amelioration of soil constraints, plant nutrients contained in the amendment, or both factors acting in concert. Because of the way in which many organic amendment experiments are conducted, these factors can be confounded due to poor experimental design leading to difficulties in accurately ascribing crop yield responses to these different factors. In this review we consider three scenarios where organic amendments are used as fertilizers, soil restorative agents and soil ameliorants to highlight common limitations of these experiments that prevent attribution of crop yield response. To overcome these limitations, we provide guidelines for the design, conduct and analysis of organic amendment experiments which will allow the attribution of yield responses to nutrition, alleviation of physicochemical constraints, or other factors. To achieve these aims, field experiments must (1) identify a genuine constraint to crop yield at the experimental site; (2) incorporate proper treatments to control for the effects of nutrient content and method of placement; (3) use appropriate sampling protocols to assess treatment differences; (4) carry out suitable soil and plant analyses; and (5) be conducted over several sites and years. Controlled environment experiments and modelling approaches may also be used to overcome some of the limitations of field experiments and provide a detailed mechanistic understanding of the crop yield response.
14238. 题目: Membrane fouling in aerobic granular sludge (AGS)-membrane bioreactor (MBR): effect of AGS size
期刊: Water Research
作者: Wenxiang Zhang, Feng Jiang
摘要: The main goal of the current study was to investigate the membrane fouling mechanism of aerobic granular sludge (AGS) from a self-cultivated AGS membrane bioreactor (MBR) with various AGS sizes. In this regard, AGSs were sieved into 6 levels: 0∼0.5, 0.5∼0.7, 0.7∼1, 1∼1.2, 1.2∼1.7 mm and larger than 1.7 mm, then filtrated by a small filtration cell. Interestingly, there appeared a critical AGS size (1∼1.2 mm) for membrane fouling. Above 1.2 mm, flux increased and fouling reduced with size, due to the loose cake layer and high permeability caused by larger AGS. Below 1 mm, for smaller AGS, higher flux and lower fouling appeared, because less extracellular polymeric substance (EPS) formed and adhered onto AGS foulants. In the critical size, membrane fouling was serious to the most extent, on account of the dual role of the compact structure of cake fouling layer and the adhesion of EPS. Moreover, this critical AGS size also possessed the highest cake layer, pore blocking and irreversible fouling, which generally existed in various operational conditions. Besides, the results of SEM, AFM, hydrophilicity and ATR-FTIR also proved that the existence of the maximum membrane fouling at the critical AGS size. This study provides a deep understanding of the membrane fouling mechanisms of AGS in MBR and is beneficial for developing a new membrane fouling mitigation strategy by terms of regulating AGS size.
14239. 题目: Application of fractional-order derivative in the quantitative estimation of soil organic matter content through visible and near-infrared spectroscopy
作者: Yongsheng Hong, Yaolin Liu, Yiyun Chen, Yanfang Liu, Lei Yu, Yi Liu, Hang Cheng
摘要: The spectral preprocessing method has become an integral component of soil analysis through visible and near-infrared (Vis-NIR) spectroscopy. Various spectral pretreatment techniques are applied to improve model accuracy by removing undesired side effects, such as spectral noise, baseline shift, and light scattering, and by accentuating spectral features. Conventional integer-order derivatives (i.e., first and second derivatives), which represent specific cases of fractional-order derivatives (FODs), may neglect some detailed spectral information related to target variables. The objective of this study was to compare the performance of FOD in the estimation of soil organic matter (SOM) with that of conventional first and second derivatives. A total of 258 soil samples (180 for calibration and 78 for validation) were collected from Jianghan Plain, Central China. The reflectance spectra and SOM concentrations of the samples were obtained in the laboratory. Two regression techniques, namely, partial least squares (PLS) and PLS–support vector machine (PLS–SVM), and eight FOD transformation processes for spectral data were combined and compared. Results indicated that as the derivative order increased, the details of the FOD spectra changed and the spectral resolution of reflectance curves improved; the intensity of the spectral signals, however, weakened. The correlation between SOM and FOD spectra was enhanced at some specific wavelengths (e.g., the absolute value of the best one-dimensional correlation coefficient of the 1.25-order derivative spectra could reach 0.65 but that of the original reflectance spectra was only 0.47). In most cases, the PLS–SVM models performed better in SOM estimation than the PLS models. The PLS–SVM model with the 1.25-order derivative spectra exhibited the best model performance and provided the validation R2 and ratio of performance to an interquartile range of 0.79 and 3.03, respectively. FOD offers greater advantages in balancing the spectral resolution and the magnitude of spectral strength than traditional integer-order derivatives. Furthermore, the FOD algorithm has strong application potential in soil Vis-NIR spectroscopy and other types of spectroscopy.
14240. 题目: Disentangling temperature effects on leaf wax n-alkane traits and carbon isotopic composition from phylogeny and precipitation
期刊: Organic Geochemistry
作者: Jia Wang, Yunping Xu, Liping Zhou, Minrui Shi, Ergu Axia, Yufu Jia, Zixun Chen, Jiazhu Li, Guoan Wang
摘要: Leaf wax n-alkanes are terrestrial plant biomarkers that have characteristics that are widely employed as proxies for climatic conditions. Understanding the relation of different environmental factors to the amounts and types of leaf wax n-alkanes in modern plants is crucial for the application of these proxies to paleoenvironmental reconstructions. However, the effects of climate conditions on plant wax characteristics remain complicated due to the interactions among temperature, precipitation and phylogeny. To evaluate the effect of temperature with minimized interfering factors, we collected 106 Artemisia plants across a 15 °C mean annual temperature gradient along the 400 mm isohyet in China. Both total n-alkane concentration (∑alk) and carbon preference index (CPI) varied greatly but did not correlate with temperature. Average chain length (ACL) increased with temperature, especially summer temperature (TJJA, June–August), indicating that ACL could be used as proxy for temperature. The stable carbon isotope compositions of n-C27, n-C29 and n-C31 were very similar in each plant (−38.2‰ to −30.0‰, −39.0‰ to −30.2‰, −38.7‰ to −30.5‰, respectively), which reflects a similar biosynthetic process for all three n-alkane homologues of Artemisia. There was a positive relation between δ13C of bulk leaf tissues (δ13Cbulk) and of n-alkanes (δ13Calk), and the average offset of δ13C29 relative to δ13Cbulk (εC29/bulk) was −7.1‰. Increasing trends in both δ13Cbulk and δ13C29 were found with temperature. However, correlation of δ13Cbulkwith temperature (R2 = 18%) was much weaker than that of δ13C29 with temperature (R2 = 60%). Therefore, δ13C29 appears to be a better proxy of paleotemperature than δ13Cbulk.