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12801. 题目: Optimisation in machine learning: An application to topsoil organic stocks prediction in a dry forest ecosystem
文章编号: N19072412
期刊: Geoderma
作者: Anika Gebauer, Victor M. Brito Gómez, Mareike Ließ
更新时间: 2019-07-24
摘要: Soil organic carbon (SOC) sequestration plays a key role in reducing the atmospheric greenhouse gas concentration. However, dry forest ecosystems in Ecuador are endangered to become a source of carbon emissions because of deforestation. Often spatial information, necessary to quantify potential carbon loss to the atmosphere, is missing. This particularly applies to remote areas of limited accessibility. This study aims to regionalise the SOC stocks of a small and poorly accessible dry forest ecosystem in southwestern Ecuador by using boosted regression tree (BRT) models. Resampling in a nested repeated k-fold cross validation approach was applied to develop robust models for a dataset of 118 samples with limited predictor information. To select an optimal set of model parameters, optimisation by differential evolution (DE) was applied for parameter tuning. Predictor selection was implemented using the same optimisation algorithm. This study demonstrates how the predictive performance of BRT models can be improved by applying an optimisation approach for parameter tuning and predictor selection. Model performance was improved by approximately 40% concerning the R2. Still, the results also demonstrated the difficulties of machine learning applications in small and highly heterogeneous natural areas. Very variable or even random factors were assumed to distort the relationship between predictor and response variables. We assume that the presented approach is particularly successful in the case of a real-valued multivariate space of tuning parameters. However, this requires testing in further machine learning applications and algorithms.

12802. 题目: Quantitative evaluation of n-alkanes, PAHs, and petroleum biomarker accumulation in beach-stranded tar balls and coastal surface sediments in the Bushehr Province, Persian Gulf (Iran)
文章编号: N19072411
期刊: Marine Pollution Bulletin
作者: Mehdi Dashtbozorg, Alireza Riyahi Bakhtiari, Mohammad Reza Shushizadeh, Lobat Taghavi
更新时间: 2019-07-24
摘要: Coastal areas within the Bushehr Province (BP), Persian Gulf, Iran, face great challenges due to the heavy organic contamination caused by rapid industrialization, and the presence of numerous oil fields. In addition, in 2014, a significant number of tar balls are found along the coasts of BP. A total of 96 samples (48 coastal sediments and 48 tar balls) were taken from eight sampling points at the BP coast during the summer of 2014. These samples were analyzed to identify the sources and characteristics of their organic matter using diagnostic ratios and fingerprint analysis based on the distribution of the source-specific biomarkers of n-alkanes, PAHs,1 hopanes and steranes. Mean concentration of n-alkanes (μg g1 dw) and PAHs (ng g1 dw) varied respectively from 405 to 220,626, and 267 to 23,568 in coastal sediments, while ranged respectively from 664 to 145,285 and 390 to 46,426 in tar balls. In addition, mean concentration of hopanes and steranes (ng g1 dw) were between 18.17 and 3349 and 184.66 to 1578 in coastal sediments, whereas in tar balls were 235–1899 and 520–1504, respectively. Pri/Phy2 ratio was 0.25 to 1.51 (0.65) and 0.36 to 1 (0.63) in coastal sediment and tar ball samples, respectively, and the occurrence of UCM3 in both matrices, reflecting the petrogenic OM4 inputs and chronic oil contamination, respectively. The C30 and C29 homologues followed Gammacerane were detected in both matrices, in particular those collected from intensive industrial activities, suggesting petrogenic sources of OM. The coastal sediment PAHs profiles were significantly dominated by HMW5-PAHs in the Bahregan Beach (BAB) (78% of total PAHs), Bandare-Genaveh (GP) (66%), and Bandare-Bushehr (BUB) (61%) stations, while the Bashi Beach (BSB) (40%), Bandare-Kangan (KP) (57%), and Bandare-Asaluyeh (AP) (51%) stations exhibited higher proportion of LMW6-PAHs. PCA7 indicated that the tar ball and coastal sediment samples deposited along the Southwest of the BP beaches are most likely originated from the Abuzar oil. Based on the intensity of the anthropogenic activities, NPMDS8 analysis revealed that the GP, BAB, NNP, AP, and KP sampling sites had a high concentration of detected organic pollutants. To the best of our knowledge, this is the first study that investigates oil pollution in costal sediments and tar balls in the BP, providing insights in to the fate of oil in the coastal areas of the Persian Gulf, Iran.
图文摘要:

12803. 题目: Paleohydrological changes in southeastern China from 13.1 to 2.5 ka based on a multi-proxy peat record
文章编号: N19072410
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Xinxin Wang, Xianyu Huang
更新时间: 2019-07-24
摘要: Investigating the hydrological changes in the East Asian monsoon regions of China during the Holocene could provide important insights into the mechanism and future variability of the East Asian summer monsoon (EASM) rainfall. However, existing studies have revealed large inconsistencies in the spatiotemporal pattern of the hydrological changes in East China, probably due to different climatic sensitivities of various proxies, the uncertainties of sedimentary chronologies and unevenness of proxy record distributions. Thus, multi-proxy records with precise dating are needed, especially in southeastern China which is one of the key places to determine the spatiotemporal pattern with few hydrological records available. In this study, hopanoid flux, humification degree, the concentration of total organic carbon (TOC) and the atomic ratio between total organic carbon and total nitrogen (C/N) of organic matter were applied on Shuizhuyang (SZY) peat cores retrieved from southeastern China to reconstruct the paleohydrological changes spanning from 13.1 to 2.5 ka. Results of these proxies reveal a moderately dry period during 13.1–11.6 ka, followed by an interval of increasing aridity from 11.6 to 8.6 ka. The Holocene optimum (referred here as an effective moisture maximum) occurred at 8.6–4.4 ka before the climate became drier from 4.4 to 2.5 ka. The hydrological changes in SZY during the Holocene with a mid-Holocene Holocene optimum are consistent with the regional climate records in southeastern China. Such an overall arid-wet-arid pattern in Southeast China during the Holocene closely tracked the variations in the west-to-east sea surface temperature (SST) gradient in tropical Pacific. We preliminarily concluded the ENSO state and the western Pacific subtropical high (WPSH) position associated with variations in the thermal state of the tropical Pacific were primarily responsible for the hydrological changes in Southeast China during the Holocene. Our study added new evidence to the spatiotemporal pattern of hydrological changes in eastern China during the Holocene.

12804. 题目: Urban black carbon - source apportionment, emissions and long-range transport over the Brahmaputra River Valley
文章编号: N19072409
期刊: Science of The Total Environment
作者: Neeldip Barman, Sharad Gokhale
更新时间: 2019-07-24
摘要: This research investigates whether the vehicular black carbon emissions originated in the North-Eastern city of Guwahati are transported over and in the Brahmaputra River Valley and the Himalayas. The total black carbon was apportioned between the fossil fuel and biomass burning by real-time measurements of black carbon concentrations at two distinct locations having different traffic volumes in 2016–17. The average observed BC concentrations were 20.58, 6.42, 3.50 and 5.29 μg/m3 at the low traffic location and 22.44, 17.14, 9.2 and 16.87 μg/m3 at the high traffic location in winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. Temperature, wind speed, and solar radiation were found to have significant negative correlations with BC concentrations, while relative humidity had positive correlations. It was found that vehicles contributed over 85% of the ambient black carbon at both locations. Black carbon emission from this dominant source was estimated for 2018, which showed that from vehicles it increased to 0.44–0.55 Gg in 2018 from 0.29 to 0.33 Gg in 2011, which may result in the adverse impacts on the eco-sensitive Brahmaputra River Valley and the Himalayas. The transport and deposition of black carbon under different climatic seasons was modelled using HYSPLIT. The results showed that black carbon particulates are being transported and deposited all-round the year in the Himalayas and the surrounding region. Pre-monsoon and monsoon seasons contributed to the largest amounts of deposition, and a clear relation was found between deposition and rainfall. The total BC deposited in the Brahmaputra River Valley and the Himalayas during one year was 22,142.69 kg and 1566.53 kg with average deposition rates of 0.6452 μgm−2 day−1 and 0.0182 μgm−2 day−1, respectively.
图文摘要:

12805. 题目: The effectiveness of soil amendments, biochar and lime, in mitigating cadmium bioaccumulation in Theobroma cacao L
文章编号: N19072408
期刊: Science of The Total Environment
作者: Gideon Ramtahal, Pathmanathan Umaharan, Anand Hanuman, Carisa Davis, Leon Ali
更新时间: 2019-07-24
摘要: Cocoa (Theobroma cacao L.) is an important neotropical tree crop grown for its seeds or beans used in global chocolate and confectionary industries. Following studies showing ill effects of long-term dietary exposure of cadmium (Cd) on human health, a number of countries including the European Union (EU) have developed stringent regulations to protect consumers from exposure to cadmium. Cocoa is capable of bioaccumulating Cd in the cocoa beans when grown in soils high in cadmium and hence livelihood of cocoa farmers can be at risk if methods to mitigate the bioaccumulation of Cd are not developed. In vitro, greenhouse and field experiments were established with four, three and three replications respectively to evaluate the effectiveness of soil amendments, biochar and lime, at various application rates (0, 0.5×, 1×, 1.5× and 2× of the recommended rate), on soil pH, Cd phytoavailability and Cd bioaccumulation in Theobroma cacao L. For the in vitro study, Cd-containing soil was amended with 5 levels of biochar and lime, while for the greenhouse and field study four application rates were tested. The study showed that while lower rates were effective under in vitro conditions as you progressed from in vitro to greenhouse to field conditions the application rates and application frequency had to be increased, as the effectiveness and longevity of the treatments were compromised by environmental factors. Our study implies that the two amendments were complementary in their action and can be used in the recommended rated to reduce Cd bioaccumulation. However further studies are required on the placement of amendments to improve their effectiveness and longevity particularly under field conditions.
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12806. 题目: Effects of chlorine disinfection on the membrane fouling potential of bacterial strains isolated from fouled reverse osmosis membranes
文章编号: N19072407
期刊: Science of The Total Environment
作者: Yun-Hong Wang, Yin-Hu Wu, Tong Yu, Xue-Hao Zhao, Xin Tong, Yuan Bai, Zheng-Yang Huo, Hong-Ying Hu
更新时间: 2019-07-24
摘要: Biofouling of reverse osmosis (RO) membranes is an inevitable issue in wastewater reclamation and limits the application of RO systems. Chlorine disinfection is widely used as a pretreatment to control biofouling. However, the extracellular polymeric substances (EPS) and cellular inclusions released during chlorine disinfection might also cause membrane fouling. Furthermore, little is known regarding the chlorine resistance of bacterial strains found on fouled RO membranes. In this study, four bacterial strains isolated from fouled RO membranes were used as testing subjects to investigate the bacterial inactivation performance of chlorine disinfection. The effects of chlorine disinfection on the RO membrane fouling potential of these strains were also revealed. The chlorine resistance ability of Sphingopyxis sp. BM1-1 was strongest among the four strains as it secretes the highest amount of EPS per cell. The log inactivation efficiency of this strain was 1-log by 0.2 mg-Cl2/L in 30 min, which was one to three orders of magnitude lower than that of the other strains. Although chlorine disinfection inactivated most bacterial cells (>90%), the reaction with chlorine significantly increased the RO membrane fouling potential of all bacterial solutions. To elucidate the main mechanism behind the increase in the fouling potential, we further investigated the changes in the properties of EPS, and the release of EPS and cellular inclusions during chlorine disinfection. Chlorine disinfection did not significantly affect the RO membrane fouling potential of the EPS secreted by these bacterial strains. However, dissolved organic carbon (DOC), protein, polysaccharide, and DNA concentration of all bacterial solutions increased by one to nine times after chlorine disinfection. These results indicate that large amounts of EPS and cellular inclusions were released into the solutions after the reaction with chlorine, which was the main cause of the increase in RO membrane fouling potential of the bacterial solution after chlorine disinfection.
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12807. 题目: Molecular changes of soil organic matter induced by root exudates in a rice paddy under CO2 enrichment and warming of canopy air
文章编号: N19072406
期刊: Soil Biology and Biochemistry
作者: Li Xiong, Xiaoyu Liu, Giovanni Vinci, Riccardo Spaccini, Marios Drosos, Lianqing Li, Alessandro Piccolo, Genxing Pan
更新时间: 2019-07-24
摘要: While crop productivity and carbon flux/partitioning in agroecosystem have been widely addressed, potential changes in organic matter composition through root deposition are still unknown under climate change. In this study, root exudates of rice and rhizospheric topsoil were collected in a paddy field under 6 years of simulated climate changes respective of CO2 enrichment, canopy air warming, and their combination as compared to the control. The molecular composition of root exudates was analyzed with liquid chromatography/mass spectrometry (LC/MS) while soil organic matter (SOM) was analyzed with pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), along with a phospholipid fatty acid analysis (PLFA) for characterizing soil microbial community. Compared to control, root exudation under elevated CO2 was enhanced but the exudate composition remained unchanged. On the other hand, root exudation rate under warming was unaffected, but the exudate composition was changed. Relative abundance of phenolic compounds in root exudates under warming, was decreased by 26% but that of amino acids was increased by 53%. However, neither root exudation nor the exudate composition was altered under combined CO2 and temperature elevation. Furthermore, increases in abundance of heterocyclic nitrogen compounds, phenolic acids and phenols (by 37%, 65%, and 26%, respectively) in SOM were relevant to the increase in bacterial/fungal (B/F) ratio under elevated CO2. This accumulation was possibly attributed to preferential utilization of the increased root exudates by bacteria. However, the overall reduction of some highly hydrophobic SOM compounds (fatty acids, phenols, and phenolic acids) by 14%, could be induced by accelerated decomposition in line with significant decrease in B/F ratio under warming. Indeed, the decreased relative abundance of phenolic compounds such as p-coumaric acid (by 49%) in root exudates lead to fungal increase, which accelerated SOM decomposition. Yet, the molecular composition of SOM was hardly changed under the combination of elevated CO2 and temperature. Overall, our findings suggested that in a rice paddy CO2 enrichment increased root exudation and B/F ratio, while air warming altered the root exudate composition and decreased B/F ratio, resulting in changes of SOM composition. These results indicate that root exudates are a key component for the regulation of SOM dynamics under climate change scenarios.
图文摘要:

12808. 题目: Characterization of aquatic organic matter: Assessment, perspectives and priorities of research
文章编号: N19072405
期刊: Water Research
作者: Morgane Derrien, Simona Retelletti Brogi, Rafael Gonçalves-Araujo
更新时间: 2019-07-24
摘要: Organic matter (OM) refers to the largest reactive reservoir of carbon-based compounds on Earth. Aside of its role as a source of carbon, OM is also actively involved in a wide range of ecological functions. It also plays an important role in the solubility, toxicity, bioavailability, mobility and distribution of pollutants. Therefore, OM is a key component in the local and global carbon cycle. About 12,000 articles containing organic matter in the title were published during the past decade, with a continuous increasing number each year (ISI Web of Science). Although this topic was widely explored and its interest has significantly increased, some limitations remain. These limitations can be technical (e.g., pre-treatment processes, low-resolution instrument, data handling) and can be related to the current approach. In this review, we first present the current strategies and tools to characterize the organic matter in the aquatic environment, then we tackle several aspects of current characterization limitations. Finally, we suggest new perspectives and priorities of research to improve the current limitations. From our point of view, simultaneous studies of particulate and dissolved OM fractions should be prioritized and multi-disciplinary approach, creation of databases, controlled experiments and collaborative works should be the next targets for future OM research priorities.
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12809. 题目: The distribution of Pb(II)/Cd(II) adsorption mechanisms on biochars from aqueous solution: Considering the increased oxygen functional groups by HCl treatment
文章编号: N19072404
期刊: Bioresource Technology
作者: Jiawen Wu, Tao Wang, Yongsheng Zhang, Wei-Ping Pan
更新时间: 2019-07-24
摘要: The adsorption mechanisms of Pb(II) and Cd(II) in aqueous solution using camellia seed husk biochars pyrolyzed at different temperatures were studied. The adsorption of Pb(II) and Cd(II) on biochars are mainly controlled by ion exchange, oxygen functional groups (OFGs) complexation, Pb(II)/Cd(II)–π interactions, and precipitation with minerals. Compared to the raw biochars, both carboxyl and phenolic hydroxyl groups increased in the biochars washed with HCl. However, the previous research ignored the effect of the increased OFGs. Thus, a revised method was proposed from this study to more accurately calculate the contribution of four different mechanisms. Precipitation with minerals was the dominant mechanism for Pb(II) and Cd(II) removal, accounting for 80.61–89.03% and 53.57–75.84%, respectively, of the total adsorption as the pyrolysis temperature increased from 300°C to 700°C. As for oxygen functional groups complexation, the percentage of Pb(II) and Cd(II) removal were 4.76-8.55% and 11.34-29.59%, respectively.
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12810. 题目: Comparative production of biochars from corn stalk and cow manure
文章编号: N19072403
期刊: Bioresource Technology
作者: Ziyun Liu, Yuanhui Zhang, Zhidan Liu
更新时间: 2019-07-24
摘要: The aim of the present work was to compare corn stalk (CS) and cow manure (CM) for hydrochar production at different reaction temperatures (180–260°C) and retention times (1–4 h). CM and CS resulted in hydrochars with significantly different physicochemical properties; however, both led to similar yields (30–65%). CM-derived hydrochar had a lower carbon content but a higher nitrogen and ash content than CS-derived hydrochar. CM-derived hydrochar demonstrated potential as a soil amendment due to its higher content of nitrogen, the presence of surface functional groups and higher specific surface area in comparison to CS-derived hydrochar. In comparison, CS-derived hydrochar demonstrated suitability as a solid fuel due to its high heating value and low ignition temperature. This study revealed that the composition of lignocellulose significantly impacted the properties and thus potential applications of hydrochar.
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12811. 题目: Enhanced anaerobic degradation of quinoline, pyriding, and indole with polyurethane (PU), Fe3O4@PU, powdered activated carbon (PAC), Fe(OH)3@PAC, biochar, and Fe(OH)3@biochar and analysis of microbial succession in different reactors
文章编号: N19072402
期刊: Bioresource Technology
作者: Kun Li, Jingxin Shi, Yuxing Han, Chunyan Xu, Hongjun Han
更新时间: 2019-07-24
摘要: The study was to explore the feasibility of polyurethane (PU), Fe3O4@PU, powdered activated carbon (PAC), Fe(OH)3@PAC, biochar, and Fe(OH)3@biochar as biological carriers in strengthening anaerobic degradation of quinoline, pyridine, and indole. When the concentrations of pollutants were 25 mg/L and 50 mg/L, reactors based on PAC and Fe(OH)3@PAC had higher degradation ratios than the other reactors. However, when the concentrations of pollutants were 75 mg/L and 100 mg/L, with the addition of PU and Fe3O4@PU, reactors began to show their superiority in the degradation of the selected NHCs. Among these, the reactor based on Fe3O4@PU had the optimal degradation ratio on quinoline, pyridine, and indole. PU, PAC, Fe(OH)3@PAC, biochar, and Fe(OH)3@biochar benefited the enrichment of Acinetobacter, Comamonas, Levilinea, Longilinea, and Desulfomicrobium. The reactor with the carrier of Fe3O4@PU had some specificity, which benefited the enrichment of Zoogloea, Thiobacillus, Anaeromyxobacter, Sphingobium, Terrimonas, Parcubacteria genera incertae sedis, Bdellovibrio, Rhizobium, and Acidovorax.

12812. 题目: Sorption process of municipal solid waste biochar-montmorillonite composite for ciprofloxacin removal in aqueous media
文章编号: N19072401
期刊: Chemosphere
作者: Ahmed Ashiq, Binoy Sarkar, Nadeesh Adassooriya, Janitha Walpita, Anushka Upamali Rajapaksha, Yong Sik Ok, Meththika Vithanage
更新时间: 2019-07-24
摘要: This study evaluates a novel adsorbent for ciprofloxacin (CPX) removal from water using a composite derived from municipal solid waste biochar (MSW-BC) and montmorillonite (MMT). The composite adsorbent and pristine materials were characterized using powder X-Ray Diffraction (PXRD), Fourier-Transform Infrared (FTIR) spectroscopy, and Scanning Electron Microscope (SEM) before and after the adsorption. Batch experiments were conducted to study the mechanisms involved in the adsorption process. Ciprofloxacin sorption mechanisms were interpreted in terms of its pH-dependency and the distribution coefficients. The SEM images confirmed the successful binding of MMT onto the MSW-BC through flaky structure along with a porous morphology. Encapsulation of MMT onto MSW-BC was exhibited through changes in the basal spacing of MMT via PXRD analysis. Results from FTIR spectra indicated the presence of functional groups for both pristine materials and the composite that were involved in the adsorption reaction. The Hill isotherm model and pseudo-second-order and Elovich kinetic models fitted the batch sorption data, which explained the surface heterogeneity of the composite and cooperative adsorption mechanisms. Changes made to the MSW-BC through the introduction of MMT, enhanced the active sites on the composite adsorbent, thereby improving its interaction with ionizable CPX molecules giving high sorption efficiency.
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12813. 题目: Sunflower stalk–derived biochar enhanced thermal activation of persulfate for high efficient oxidation of p-nitrophenol
文章编号: N19072314
期刊: Environmental Science and Pollution Research
作者: Peng Sun, Kaikai Zhang, Jianyu Gong, Aimal Khan, Yu Zhang, Md. Suzaul Islama, Yanrong Zhang
更新时间: 2019-07-23
摘要: Sunflower stalk–derived biochars (BC) were prepared at various temperatures (i.e., 500, 650, and 1000 °C) and demonstrated as a highly efficient catalyst in persulfate (PS) activation for the oxidation of p-nitrophenol (PNP) at 60 °C. The apparent PNP oxidation rate constant in the BC500 (0.1543 L mol−1 S−1), BC650 (0.6062 L mol−1 S−1), or BC1000 (2.1379 L mol−1 S−1) containing PS system was about 2, 8 and 28 times higher than that in PS/PNP (0.0751 L mol−1 S−1) system, respectively. The effect of reaction temperature on PNP oxidation was also investigated. Furthermore, the radical quenching tests and electron paramagnetic resonance spectroscopy (EPR) were employed to investigate the sulfate and hydroxyl radicals for PNP oxidation. The Raman results suggested that the defective sites on biochars possess vital role for oxidation of PNP in PS system. The possible activation pathway of PS/BC was proposed that the defective sites on BC were involved for weakening the O–O bond in PS and subsequently cleaving O–O bond by heat to generate sulfate radical. The oxidation of PNP at low concentration (below 100 μg L−1) was completely removed in urban wastewater by PS/BC system within 30 min. This work would provide new insights into PS activation by BC catalyst and afford a promising method for organic pollutant removal in high-temperature wastewater.

12814. 题目: Performance of Physically and Chemically Activated Biochars in Copper Removal from Contaminated Mine Effluents
文章编号: N19072313
期刊: Water, Air, & Soil Pollution
作者: Flavia Lega Braghiroli, Hassine Bouafif, Carmen Mihaela Neculita, Ahmed Koubaa
更新时间: 2019-07-23
摘要: The increasing global demand for metals and minerals justifies the intensive study of treatment options for contaminated mine effluents. The present study evaluated the conversion of wood residues into physically and chemically activated biochars and their subsequent use in the treatment of Cu in synthetic and actual contaminated mine drainage. First, wood residues were converted into biochar by fast pyrolysis. Then, physical (using steam or CO2) or chemical (using KOH) activation was carried out in a homemade pilot-scale furnace. After activation, highly microporous (KOH materials) and micro/mesoporous activated biochars (CO2 and steam materials) were obtained. Batch adsorption testing was first conducted with synthetic effluents. Results showed that CO2-activated biochar was the most Cu effective adsorbent (99% removal) at low concentrations (5–20 mg L−1). The mechanisms of Cu2+ adsorption involved physical and chemisorption for biochars and CO2-activated biochar, while chemisorption for KOH-activated biochars was probably due to the high proportion of functional groups connected to their surface. In multi-metal acid mine drainage, metal adsorption capacities deteriorated for most of the materials, probably due to the effects of ion competition. However, KOH-activated biochar decreased Cu2+ concentrations to below the authorized monthly mean allowed by Canadian law (0.3 mg L−1) and decreased Co, Pb, and Mn concentrations up to 95%. These findings indicate that high porosity and oxygenated functional groups connected to the surface of activated biochars are important properties for the enhancement of interactions between carbon materials and metals from mine effluents, as well as for their performance improvement in mine drainage treatment.

12815. 题目: Organic phosphorus mineralization characteristics in sediments from the coastal salt marshes of a Chinese delta under simulated tidal cycles
文章编号: N19072312
期刊: Journal of Soils and Sediments
作者: Junhong Bai, Lu Yu, Xiaofei Ye, Zibo Yu, Yanan Guan, Xiaowen Li, Baoshan Cui, Xinhui Liu
更新时间: 2019-07-23
摘要: Purpose: Sediment organic phosphorus (OP) mineralization plays an important role in phosphorus cycling in coastal salt marshes. However, information on OP mineralization characteristics in sediments under tidal cycles is limited. Materials and methods: Sediment cores were collected from salt marshes which were exposed to tidal cycles. A laboratory manipulation experiment was conducted under simulated tidal flooding cycles. After the completion of each incubation experiment, the inorganic phosphorus (IP) and OP fractions were analyzed and net phosphorus mineralization rates were calculated to investigate the sediment OP mineralization process. Sediment microbial characteristic and chemical properties were determined to identify factors that affect the mineralization of OP in the Yellow River Delta. Results and discussion: During the first 2 days of incubation, the tidal cycles significantly increased the microbial biomass in the sediments, which accelerated the assimilation of IP by microorganisms and the transformation of IP into OP in their bodies, thereby causing a significant increase in OP in the sediments. After 2 days of incubation, the mineralization and immobilization of OP entered the adaptation stage and gradually reached the dynamic balance of various phosphorus fractions in sediments. The path analysis showed that microbial biomass phosphorus and carbon (MBP and MBC) and the activity of alkaline phosphatase (AKP) are the direct factors influencing OP mineralization in sediments. The indirect effects of soil organic matter (SOM), water content (WC), exchangeable aluminum (Al0), and exchangeable iron (Fe0) on net phosphorus mineralization rate were relatively high. Conclusions: In the laboratory experiments, we showed that the recovery of tidal cycles caused a fluctuation in OP mineralization and immobilization in sediments, which reached equilibrium over time. The tidal effect was conducive to maintaining the stability of phosphorus in sediments of coastal salt marshes. The findings of this study can contribute to protecting water quality and improving primary productivity in coastal salt marshes by regulating the tidal cycles and the key environmental factors (e.g., SOM, WC, Al0, and Fe0) influencing OP mineralization.

12816. 题目: Organic fertilizers have divergent effects on soil N 2 O emissions
文章编号: N19072311
期刊: Biology and Fertility of Soils
作者: Tiehu He, Junji Yuan, Jiafa Luo, Weijin Wang, Jianling Fan, Deyan Liu, Weixin Ding
更新时间: 2019-07-23
摘要: A field experiment was conducted in a subtropical tea (Camellia sinensis (L.) O. Kuntze) plantation in Jiangsu Province, China, including the following treatments: no nitrogen (N) fertilizer (control), conventional mineral N fertilizer (urea) (CN), soybean cake fertilizer (SF), pig manure (PM), cattle manure (CaM), chicken manure (CM), and CM + biochar (CMB). Cumulative nitrous oxide (N2O) and nitric oxide (NO) emissions were 4.8 ± 0.1 and 3.7 ± 0.3 kg N ha−1 year−1 under CN, respectively, and increased to 5.4 ± 0.2 and 4.6 ± 0.3 kg N ha−1 year−1 under SF (P < 0.05), respectively. Treatments with livestock manures (PM, CaM, and CM) reduced N2O (41.4–49.6%) and NO (46.5–59.8%) emission in comparison to CN. Combined amendment of CM and biochar more effectively reduced N2O emissions than CM treatment alone. Based on a meta-analysis of 26 global paired measurements in acid soils, the threshold of C/N ratios of organic fertilizers between the positive and negative responses of N2O emissions to organic fertilizers was 8.6 with a range of 4.5–22.3 (95% confidence interval), indicating that reduced N2O emission under PM, CaM and CM was potentially due to their C/N ratios compared to the threshold. Organic fertilizer application did not influence tea yield, while combined application of CM and biochar increased tea yield and resulted in the least yield-scaled N2O emission. N2O and NO emission factors for N fertilizers applied under CN were 1.9 ± 0.1% and 1.5 ± 0.2%, respectively, and reduced to 0.08 ± 0.04% and 0.12 ± 0.04% under CMB, respectively. The results suggest that tea plantations in the subtropical region are hotspots for N2O and NO emissions. Combined application of chicken manure and biochar could mitigate N gas emissions and increase yield in the tea plantation systems.

12817. 题目: Effects of residual ozone on the performance of microorganisms treating petrochemical wastewater
文章编号: N19072310
期刊: Environmental Science and Pollution Research
作者: Liya Fu, Changyong Wu, Yuexi Zhou, Jiane Zuo, Guangqing Song
更新时间: 2019-07-23
摘要: This study investigated the effects of residual ozone on the performance of microorganisms treating petrochemical wastewater using batch experiments with low and high ozone dosages (5.0 mg/L and 50.0 mg/L, respectively). The results indicated that the low residual ozone concentration significantly increased COD removal by 24.21% in the biological process compared to control group with no ozone residual, while the high residual ozone concentration showed the opposite effect. In the reactor with low residual ozone concentration (0.45 mg/L), the amount of loosely bound (LB)-extracellular polymeric substances (EPS) in the activated sludge decreased by 23.23%, while the amount of tightly bound (TB)-EPS increased by 129.16% compared to the none-ozone residual reactor. In addition, the low residual ozone was found to improve the bioactivity of activated sludge by 139.73% in the first 30 min of the biological process. In the reactor with high residual ozone concentration (0.91 mg/L), both LB- and TB-EPS of the activated sludge increased, while bioactivity decreased. This implies that low residual ozone in a bio-reactor can enhance microbial activity by increasing contact between the pollutants and cells by removing LB-EPS covering the outer layer of the sludge. The microorganisms in the sludge samples could be classified into three groups representing those that are susceptible to ozone, tolerant to low dose of residual ozone, and resistant to high dose of residual ozone. The resistant bacteria Gemmatimonadaceae uncultured became predominant, with a relative abundance of 11.37%, under low residual ozone conditions, while it decreased at high ozone concentrations. The results showed that a certain amount of residual ozone could stimulate the activity of microorganisms by altering the EPS fraction and structure of the microbial community, and thus it is important for the removal of refractory organics from wastewater in the ozone-biological process.

12818. 题目: In situ immobilization of Cr and its availability to maize plants in tannery waste–contaminated soil: effects of biochar feedstock and pyrolysis temperature
文章编号: N19072309
期刊: Journal of Soils and Sediments
作者: Muhammad Imran Rafique, Adel R. A. Usman, Munir Ahmad, Abdelazeem Sallam, Mohammad I. Al-Wabel
更新时间: 2019-07-23
摘要: Purpose: Tannery waste–contaminated soil has a high amount of several toxic chemicals and heavy metals including chromium (Cr), which makes it unsuitable for agriculture practices. Majority of studies have reported the use of biochar (BC) as an amendment to restore contaminated soil. The efficiency of BC to immobilize Cr depends on its pretreatment and feedstock. This study aimed to investigate the potential of using BC for Cr immobilization and reducing its availability to maize plants in tannery waste–contaminated soil. The effect of BC on plant growth and heavy metal (Cr, Cu, Zn, Pb, Fe, and Mn) contents of maize shoots was also investigated. Materials and methods: The soil was collected from landfill areas of Riyadh city (N 24° 25′, E 46° 34′). BCs were produced by pyrolyzing jujube (Ziziphus spina-christi) leaves (JL) and manure (M) waste at 300 and 700 °C. Collected soil and produced materials were characterized physically and chemically by following standard procedure. A greenhouse pot experiment was conducted with unamended tannery waste–contaminated soil and soil amended with the obtained BCs (JLBC-300, JLBC-700, MBC-300, and MBC-700) at an application rate of 50 g kg−1 and cultivated with maize (Zea mays L.). Before cultivation, soil-soluble Cr was measured in five leachate cycles. Dry matter and heavy metal (Cr, Cu, Zn, Pb, Fe, and Mn) contents of maize shoots were measured after harvesting. Results and discussion: The results show that BCs produced at 700 °C showed the highest decrease in the concentrations of soil-soluble Cr and reduced its cumulative concentrations in soil leachates by about 93% and 59.0% for MBC-700 and JLBC-700 compared with the control soil, respectively. Overall, the highest decrease in cumulative soluble Cr was pronounced for MBC-700 followed by JLBC-700. For heavy metal contents in shoots, Cr concentrations were under detection limit in all treatments. However, BC amendments showed significant differences from the control for Cu, Mn, and Fe. Conclusions: From findings, it could be concluded that application of BCs pyrolyzed at 700 °C (especially for MBC-700) could be used as an amendment for reducing Cr mobility in tannery waste–contaminated soil and may create favorable conditions for crop production.

12819. 题目: Leaf wax n-alkane pattern and compound-specific δ13C of plants and topsoils from semi-arid Mongolia
文章编号: N19072308
期刊: Biogeosciences
作者: Julian Struck, Marcel Bliedtner, Paul Strobel, Jens Schumacher, Enkhtuya Bazarradnaa, and Roland Zech
更新时间: 2019-07-23
摘要: n-Alkane pattern and their compound-specific δ13C signatures are valuable proxies for paleoenvironmental reconstructions. So far, their potential has not been investigated in semi-arid to arid regions. We have therefore analysed the leaf wax n-alkanes and their compound-specific δ13C of five plant species (Poaceae, Cyperaceae, Artemisia spp., Caragana spp. and Larix sp.), and topsoils (0–5 cm) along two transects in central and southern Mongolia. Grasses depict a distinct dominance of the n-C31 homologue, whereas Caragana spp. and Artemisia spp. are dominated by n-C29. Larix sp. is characterized by the mid-chain n-alkanes n-C23 and n-C25. From plant to soil, n-alkane homologue pattern show the potential to differentiate between grass covered sites from those covered by Caragana spp. n-Alkane concentrations and OEP values of the topsoils are distinctly influenced by mean annual temperature, mean annual precipitation and aridity, likely reflecting the degree of n-alkane degradation and biomass production. In contrast, the n-alkane average chain-length and the n-alkane ratio (n-C31 / n-C29 + n-C31) are not affected by climatic parameters. The compound-specific δ13C signatures are strongly corelated to climate, showing a significant enrichment with increasing aridity, indicating the effect of water use efficiency. Our calibration results suggest that long-chain n-alkanes and their compound-specific δ13C signatures have great potential to reconstruct paleoenvironmental and -climatic conditions when used in sediment archives from Mongolia.

12820. 题目: Understanding the granulation of partial denitrification sludge for nitrite production
文章编号: N19072307
期刊: Chemosphere
作者: Shenbin Cao, Rui Du, Hanyu Zhang, Yongzhen Peng
更新时间: 2019-07-23
摘要: Partial-denitrification (PD) has previously been demonstrated to be another pathway for nitrite production, which provides a cost-effective approach for nitrate (NO3-N) removal through combing with anammox. In this study, the formation of PD granules was firstly investigated in a sequencing batch reactor (SBR) with influent nitrate of 60 mg N/L. The granulation process was explored via the physicochemical and biological characterization. Sludge granulation initiated within the first 20 days with an average size of 93.7 μm in diameter, it experienced a developing, shaping and matured periods, with a maximum size of 709.3 μm obtained. High nitrite production of PD was always maintained during the granulation with a mean nitrate-to-nitrite transformation ratio (NTR) of 88.3%, and in-situ maximum NO3–N reduction rate of 84.9 mg N/h/g VSS was obtained. Mature PD granules hold an excellent settling property with 5-min sludge volume index (SVI5) of 32.0 mL/g MLSS obtained and smooth surface with large amounts of rod bacteria covered. CaCO3 precipitates formed in the PD process played a vital role in the initial granulation, acting as the nucleus for cell attachment. Extracellular polymeric substances (EPS), mainly the proteins (PN) content, was found to be of supreme importance in granules developing and maintaining its structural stability. Besides, the abundance of Flavobacterium and norank_p__Gracilibacteria were revealed to be in accordance with the change of granules size, seemed to contribute to sludge granulation. The developed granule-based PD integrated with anammox process provides an engineering-feasible and economic-favorable solution for industrial nitrate wastewater treatment.
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