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17581. 题目: Satellite-based estimation of particulate organic carbon export in the northern South China Sea
文章编号: N18102107
期刊: Journal of Geophysical Research: Oceans
作者: Teng Li, Yan Bai, Xianqiang He, Yuyuan Xie, Xiaoyan Chen, Fang Gong, Delu Pan
更新时间: 2018-10-21
摘要: Knowledge of particulate organic carbon (POC) export flux (EP) is the key to understanding the marine biological carbon pump. In this paper, a satellite remote sensing algorithm based on the food‐web model established by Siegel et al. (2014) was used to estimate EP in the northern South China Sea (NSCS), which consists of the direct sinking flux of large phytoplankton and associated aggregates by gravity and flux of zooplankton feces by grazing. This is the first time to unveil the fine spatiotemporal variation of satellite‐derived EP in the NSCS. Compared with the results on 1° spatial scale products, the model results based on the satellite products with 1/3° and 1/12° resolution showed better consistency with the observations. Validation with in situ EP showed that the model exhibited a good performance in the NSCS basin, but the predicted EP in the shelf regions were smaller compared with the measurements. The satellite‐derived annual mean EP in the shelf areas was 8.47 mmol C·m^‐2·d^‐1 and 5.56 mmol C·m^‐2·d^‐1 in the NSCS basin, on the 1/3° spatial scale, with the relative difference from observations were about ‐50% and ‐15% for the shelf and basin, respectively. The flux of feces from zooplankton grazing, especially that from micro‐zooplankton grazing, might account for the major fraction of EP in the NSCS. Accurate products of OPP, empirical coefficients in the food web (e.g., export efficiencies of zooplankton grazing, specific mortality rate of non‐grazing phytoplankton) suitable for the NSCS are essential in the performance improvement of the satellite‐based EP model.

17582. 题目: Sedimentary profiles of pollution marker chemicals along a large tributary of Chesapeake Bay (mid-Atlantic USA)
文章编号: N18102106
期刊: Journal of Soils and Sediments
作者: Gregory D. Foster, Cassi Walls, Phillip R. McEachern, Thomas B. Huff, Randolph McBride
更新时间: 2018-10-21
摘要: Purpose: Molecular markers in environmental geochemistry include natural product or pollutant chemicals in sediments that are indicative of discharge sources or emission pathways. Four classes of molecular marker compounds, including fatty acids, sterols, PCBs, and PAHs, in surficial sediments (top 2 cm) collected along a downstream transect of the Potomac River within the US mid-Atlantic region were analyzed and correlated with potential pollution discharge sources in close proximity to the sampling sites. Materials and methods: Thirty-five surficial sediment samples were collected using a petite Ponar grab sampler along a 320-km longitudinal transect of the Potomac River (mid-Atlantic USA), a major tributary of Chesapeake Bay, ranging from the upland fluvial river to its confluence with the Bay. The sediments were collected along the transect at approximately equidistant points. The marker chemicals were extracted from sediments using microwave-assisted extraction and quantified on a dry weight basis by gas chromatography or gas chromatography-mass spectrometry. Sediment moisture, texture, and organic carbon and nitrogen content were also determined. Results and discussion: Fatty acids and sterols were well correlated with ecological factors in the Potomac River, while the sterol ratio epi+brassicasterol/stigmasterol showed moderate spatial correlation with nearby waste treatment plants (WTPs) and city locations, especially in the upland and tidal freshwater river. The fecal sterol coprostanol also showed moderate spatial correlation with some WTPs in both the upland and tidal river. PCB and PAH concentrations were primarily correlated with urban and large military installations. PCBs in sediments appeared to be predominantly derived from Aroclors while PAHs showed a strong pyrogenic origin. Retene and perylene were unique markers for PAHs in sediment and were indicative of aged organic matter in sediments. Conclusions: The marker chemicals had utility in identifying pollution emission sources and pathways in the Potomac River. For PCB pollutants, sediment profiles reflected localized source emissions from industrial sites. PAHs showed a downstream plume effect derived from urban Washington, DC. Fatty acids and sterols were most useful for identifying ecological shifts (i.e., terrestrial versus aquatic origin), but showed spatial correlations with wastewater treatment plants and cities.

17583. 题目: Cellulose and lignin regulate partitioning of soil phosphorus fractions and alkaline phosphomonoesterase encoding bacterial community in phosphorus-deficient soils
文章编号: N18102105
期刊: Biology and Fertility of Soils
作者: Qi Sun, Husen Qiu, Yajun Hu, Xiaomeng Wei, Xiangbi Chen, Tida Ge, Jinshui Wu, Yirong Su
更新时间: 2018-10-21
摘要: Crop straw retention is believed to effectively promote soil phosphorus (P) availability. However, little is known about how specific components of crop straw, such as cellulose and lignin, regulate soil P availability, which depends on several processes, including the reactions catalyzed by phosphomonoesterase activities. Of the genes encoding alkaline phosphomonoesterase, phoD are ubiquitous in soil. Here, we studied the effects of cellulose and lignin on soil P fractions and phoD-harboring bacterial community in P-deficient upland and paddy soils. In the upland soil, cellulose amendment significantly increased microbial P assimilation and decreased soil citrate-P and HCl-P fractions, suggesting that cellulose mediated the conversion of soil P fractions from the non-labile to the labile P pool (e.g., microbial P) via microbial enrichment. Lignin significantly increased soil Olsen-P content, but scarcely influenced P-related microbial parameters after incubation for 60 days. Therefore, lignin directly increased soil available P via competitive P adsorption by lignin functional groups, rather than by altering soil microbial processes. Compared to upland soil, a smaller effect of both cellulose and lignin on phoD gene abundance, alkaline phosphomonoesterase activity, and phoD-harboring bacterial community was observed in paddy soil, suggesting that the carbon inputs may be unable to promote organic P availability under oxygen-deficient conditions. Our results highlight the contrasting mechanisms of soil P availability regulation via cellulose or lignin in P-deficient soils.

17584. 题目: Responses of soil organic carbon, soil respiration, and associated soil properties to long‐term thinning in a semi‐arid spruce plantation in northwestern China
文章编号: N18102104
期刊: Land Degradation & Development
作者: Zhi‐Bin He, Long‐Fei Chen, Jun Du, Xi Zhu, Peng‐Fei Lin, Jing Li, Yang‐Zhou Xiang
更新时间: 2018-10-21
摘要: Silvicultural thinning using whole‐tree harvesting (WTH) has been an important and common forest management practice for Picea crassifolia plantations in the Qilian Mountains of China. However, consequences of this silvicultural practice are still not well‐known. We examined the influence of three thinning levels on long‐term soil carbon storage, soil respiration (Rs), and soil properties. Our results showed that soil carbon stocks decreased significantly with increasing thinning intensity at a soil depth of 0‐70 cm, while soil water storage increased, especially in the deep soil layers (30‐70 cm). Mean Rs rates during the growing season increased significantly with increasing thinning intensity, and the dynamics of Rs coincided with that of soil temperature. Generally, 65 to 73% of the variation in Rs rates in three thinning levels was explained by the changes in soil temperature. WTH significantly increased soil bulk density at the 0‐30 cm and soil pH at the 0‐20 cm depths, and significantly decreased soil nitrogen and C:N ratio in the 0‐20 cm layers. As no significant effect of WTH was detected on fine root biomass, we attributed the elevated soil respiration to accelerated decomposition of organic matter as a result of elevated soil temperature and substrate quality. Our results demonstrate the potential for WTH to relieve water deficits in spruce plantations in semi‐arid regions, while suggest that WTH has a negative impact on carbon sequestration.

17585. 题目: Coastal halophytes alter properties and microbial community structure of the saline soils in the Yellow River Delta, China
文章编号: N18102103
期刊: Applied Soil Ecology
作者: Changliang Jing, Zongchang Xu, Ping Zou, Qi Tang, Yiqiang Li, Xiangwei You, Chengsheng Zhang
更新时间: 2018-10-21
摘要: Soil microbial community and extracellular enzymes play an important role in soil biochemical reactions and biogeochemical cycles. In this study, we evaluated the influence of cultivated halophytes on soil enzyme activity and soil microbial composition in the Yellow River area. We selected two local halophytes—Atriplex triangularis and Suaeda glauca—as models. We initially investigated the effects of cultivation of the two halophytes on soil properties and enzyme activities. Subsequently, we evaluated the effects on the bacterial community structure using 16S rRNA gene sequencing studies. Soil salinity, organic matter, and Na⁺ concentration were significantly higher in the rhizosphere than in the bulk soil for both halophytes studied. Significantly higher urease and dehydrogenase activities were observed in the rhizosphere of A. triangularis than in that of S. glauca. Significant differences in bacterial community structure between the rhizosphere of S. glauca and the associated bulk soil mainly involved the phyla Acidobacteria, Proteobacteria, Bacteroidetes, and Chloroflexi. In the case of A. triangularis, these differences involved Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Acidobacteria. In conclusion, cultivation of these two halophytes could assist in desalinization, altered rhizosphere and bulk soil properties, altered enzyme activities, and shifts in bacterial populations. The results contributed to our understanding of the effects of halophyte cultivation on coastal ecosystem phytoremediation, specifically in the context of the Yellow River Delta.

17586. 题目: Oxidation of 2,4-bromophenol by UV/PDS and formation of bromate and brominated products: A comparison to UV/H₂O₂
文章编号: N18102102
期刊: Chemical Engineering Journal
作者: Congwei Luo, Jing Gao, Daoji Wu, Jin Jiang, Yongze Liu, Weiwei Zhou, Jun Ma
更新时间: 2018-10-21
摘要: The sustained massive use of bromophenols in industrial products leads to their especially pernicious in aquatic environments. This study explored the oxidation kinetics of 2,4-bromophenol (2,4-DBP) and formation potential of bromate (BrO₃⁻) and brominated polymeric products of concern during water treatment by UV/persulfate (PDS) and UV/hydrogen peroxide (H₂O₂). 2,4-DBP exhibited appreciable reactivity toward sulfate radical (SO₄⁻) and hydroxyl radical (HO). The second-order rate constants of SO₄⁻ and/or HO with 2,4-DBP at pH 9 were higher than those at pH 5 and 7. It is mainly due to the deprotonation of the hydroxyl group in 2,4-DBP when pH > pKa (pKa = 7.79). The chloride ions (Cl⁻) significantly inhibited 2,4-DBP degradation in UV/PDS process, which showed little inhibition in the UV/H₂O₂ process. Carbonate/bicarbonate (CO₃²⁻/HCO₃⁻) and natural organic matters (NOM) significantly retarded 2,4-DBP degradation in both processes. BrO₃⁻ formation in UV/PDS process in the presence of 2,4-DBP (as organic carbon model compound) exhibited biphasic kinetics, i.e., BrO₃⁻ was undetectable in the lag phase and rapid generated in the secondary rapid phase. However, BrO₃⁻ was not detected throughout UV/H₂O₂ process. According to the analysis by electrospray ionization-triple quadruple mass spectrometry, tentative oxidation pathway was proposed. The results showed that brominated polymeric products in the reaction of 2,4-DBP with SO₄⁻ and/or HO were readily produced by electrophilic addition and coupling reactions. Given the enhanced toxicological effects of these BrO₃⁻ and brominated polymeric products compared with the bromophenols precursors, it is important to better understand their reactivities and fates when UV/PDS or UV/H₂O₂ is applied for the oxidative treatment of bromophenols-containing waters.
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17587. 题目: Exploring pore water biogeochemical characteristics as environmental monitoring proxies for a CO₂ storage project in Pohang Basin, South Korea
文章编号: N18102101
期刊: Marine Pollution Bulletin
作者: Meilian Chen, Myongho Park, Ji-Hoon Kim, Young Jae Shinn, Yun Kyung Lee, Jin Hur
更新时间: 2018-10-21
摘要: Biogeochemical parameters of pore waters, including dissolved organic matter, nutrients, sulfate, alkalinity, and chloride are explored as convenient and sensitive proxies to monitor the CO₂ geological storage sites. Five sites for a CO₂ storage project in the Pohang Basin of the East Sea in South Korea were investigated for the pre-injection biogeochemical conditions of these sites. Higher dissolved organic carbon (~36 mg L⁻¹), chromophoric and fluorescent dissolved organic matter, nutrients, and alkalinity were observed in a fluvially affected acoustic blanking site with geological faults. A general increasing downcore trend of measured DOM parameters, nutrients, and alkalinity with depth was found at the acoustic blanking site affected by riverine runoff with significant correlations among the parameters (R²: ~0.4–0.8), highlighting the impact of geological features and external inputs on the downcore biogeochemical properties. The results presented in this study suggest that DOM could be utilized as a robust and complementary biogeochemical parameter.

17588. 题目: Hypoxia and nutrient dynamics affected by marine aquaculture in a monsoon-regulated tropical coastal lagoon
文章编号: N18102011
期刊: Environmental Monitoring and Assessment
作者: Jing Zhang, ZhuoYi Zhu, Wen Yuan Mo, Su Mei Liu, Dao Ru Wang, Guo Sen Zhang
更新时间: 2018-10-20
摘要: The Laoyehai (lagoon) is located at the east coast of Hainan Island in the South China Sea and has been subject to perturbations from human activities, notably marine aquaculture, and has eutrophic surface and hypoxic near-bottom waters. A lack of knowledge of hydrodynamic and biogeochemical processes is a challenge to the sustainable management of lagoon at the ecosystem level in science. Five field campaigns, including three during the southwest monsoon and two in the northeast monsoon periods, were carried out at the Laoyehai in 2008–2011. The aim of this study is to investigate the impacts of dynamic processes of hydrography and human activities on nutrient geochemistry and their relationships to the system eutrophication and hypoxia in the lagoon. In this coastal system, high levels of ammonium relative to nitrate are found, elevated phosphate skews the DIN/DIP relative to the Redfield ratio, and the dissolved silicate concentration is high because of submarine groundwater discharge. The organic fraction in the Laoyehai accounts for a large proportion of the total nutrients associated with the release of wastes from marine aquaculture. The hypoxia of near-bottom waters in the Laoyehai is created and maintained by heterotrophic processes that are fueled by organic matter, which are exacerbated by poor water exchange as a consequence of the geomorphology and weak tidal circulation.

17589. 题目: Biochar Modulates Methanogenesis through Electron Syntrophy of Microorganisms with Ethanol as a Substrate
文章编号: N18102010
期刊: Environmental Science & Technology
作者: Hai-Yan Yuan, Long-Jun Ding, Eric Fru Zama, Pan-Pan Liu, Wael N. Hozzein, Yong-Guan Zhu
更新时间: 2018-10-20
摘要: Biochar has the potential to influence methanogenesis which is a key component of global carbon cycling. However, the mechanisms governing biochar’s influence on methanogenesis is not well understood, especially its effects on interspecies relationships between methanogens and anaerobic bacteria (e.g., Geobacteraceae). To understand how different types of biochar influence methanogenesis, biochars derived from rice straw (RB), wood chips (WB), and manure (MB) were added to the methanogenic enrichment culture system of a paddy soil. Compared to the nonbiochar control, RB and MB additions accelerated methanogenesis remarkably, showing 10.7 and 12.3-folds higher methane production rate, respectively; while WB had little effect on methanogenesis. Using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electrochemical methods, RB and MB also had higher redox-active properties or charging and discharging capacities than WB, and the functional groups, mainly quinones, on the biochar surface played an important role in facilitating methanogenesis. Quantitative polymerase chain reaction results demonstrated that electronic syntrophy did exist between methanogens and Geobacteraceae. RB and MB stimulate methanogenesis by facilitating direct interspecies electron transfer between methanogens and Geobacteraceae. Our findings contribute to a better understanding of the effects of biochars from different feedstocks on methanogenesis and provide new evidence to the mechanisms of stimulating methanogenesis via biochar.
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17590. 题目: Pathways of mineral‐associated soil organic matter formation: integrating the role of plant carbon source, chemistry, and point‐of‐entry
文章编号: N18102009
期刊: Global Change Biology
作者: Noah W Sokol, Jonathan Sanderman, Mark A Bradford
更新时间: 2018-10-20
摘要: To predict the behavior of the terrestrial carbon cycle, it is critical to understand the source, formation pathway, and chemical composition of soil organic matter (SOM). There is emerging consensus that slow‐cycling SOM generally consists of relatively low molecular weight organic carbon substrates that enter the mineral soil as dissolved organic matter and associate with mineral surfaces (referred to as ‘mineral‐associated OM’, or MAOM). However, much debate and contradictory evidence persists around: (1) whether the organic C substrates within the MAOM pool primarily originate from aboveground versus belowground plant sources, and (2) if C substrates directly sorb to mineral surfaces or undergo microbial transformation prior to their incorporation into MAOM. Here, we attempt to reconcile disparate views on the formation of MAOM by proposing a spatially‐explicit set of processes that link plant C source with MAOM formation pathway. Specifically, because belowground versus aboveground sources of plant C enter spatially distinct regions of the mineral soil, we propose that fine‐scale differences in microbial abundance should determine the probability of substrate‐microbe versus substrate‐mineral interaction. Thus, formation of MAOM in areas of high microbial density (e.g. the rhizosphere and other microbial hotspots) should primarily occur through an in vivo microbial turnover pathway, and favor C substrates that are first biosynthesized with high microbial carbon‐use efficiency prior to incorporation in the MAOM pool. In contrast, in areas of low microbial density (e.g. certain regions of the bulk soil), MAOM formation should primarily occur through the direct sorption of intact or partially oxidized plant compounds to un‐colonized mineral surfaces, minimizing the importance of carbon use efficiency, and favoring C substrates with strong ‘sorptive affinity’. Through this framework, we thus describe how the primacy of biotic versus abiotic controls on MAOM dynamics are not mutually exclusive, but rather spatially dictated. Such an understanding may be integral to more accurately modeling soil organic matter dynamics across different spatial scales.

17591. 题目: Dynamics of maize straw residue 13 C incorporation into aggregates of a Mollisol as affected by long-term fertilization
文章编号: N18102008
期刊: Journal of Soils and Sediments
作者: Ming Li, Yang Wang, Fan Ding, Yingde Xu, Ping Zhu, Xueli Ding, Jingkuan Wang
更新时间: 2018-10-20
摘要: Purpose: Soil aggregates play a crucial role in the sequestration of soil organic carbon (SOC). Returning crop residues to soil is known to strongly influence soil C stocks, but the specific contribution of crop residues to soil aggregates influenced by long-term fertilization remains largely unknown. This study investigated the effects of long-term fertilization on the distribution of ¹³C-labeled maize straw residue in different aggregate size fractions and their retention in soils over a 1-year incubation. Materials and methods: The dynamic variation and the distribution of maize straw-derived ¹³C in soil aggregates were monitored using a ¹³C stable isotope mass-balance approach. The following three fertilization treatments were selected: (1) without fertilization (CK), (2) mineral fertilizer (NPK), and (3) cow manure with mineral fertilizer (NPKM). Soil samples were collected from the surface layer (0–20 cm) of a long-term field experiment of Mollisols (Luvic Phaeozem) in 2015 at Gongzhuling, Jilin Province, China, which was established in 1980. Soils were incubated for 360 days at 25 °C, with or without ¹³C-labeled maize straw and destructively collected on the days of 45, 90, 135, 180, and 360. Soil aggregates were separated into two fractions (macroaggregates, > 250 μm; microaggregate, < 250 μm) by wet sieving. Results and discussion: The NPK treatment retained the most of maize straw ¹³C in macroaggregates (28.49%), but more maize straw ¹³C was incorporated in microaggregates for NPKM soil (4.02%) than NPK and CK on day 45. The highest amount of maize straw ¹³C was incorporated in macroaggregate on the days of 90, 135, and 180, and in microaggregate on the days of 135, 45, and 135 for CK, NPK, and NPKM, respectively. Organic manure-amended soil tended to sequester more maize straw ¹³C in the microaggregate fractions as compared with the NPK and CK treatments throughout the incubation. The maize straw ¹³C remaining in both of macro- and microaggregates followed the order of NPKM > NPK > CK for all soil aggregates after the 360-day incubation. Conclusions: Our results illustrated that long-term application of manure with mineral fertilizer helps to stabilize or increase the retention of exogenous C in the soil aggregates.

17592. 题目: Linking oral bioaccessibility and solid phase distribution of potentially toxic elements in extractive waste and soil from an abandoned mine site: Case study in Campello Monti, NW Italy
文章编号: N18102007
期刊: Science of The Total Environment
作者: Neha Mehta, Tatiana Cocerva, Sabrina Cipullo, Elio Padoan, Giovanna Antonella Dino, Franco Ajmone-Marsan, Siobhan Fiona Cox, Frederic Coulon, Domenico Antonio De Luca
更新时间: 2018-10-20
摘要: Oral bioaccessibility and solid phase distribution of potentially toxic elements (PTE) from extractive waste streams were investigated to assess the potential human health risk posed by abandoned mines. The solid phase distribution along with micro-X-ray fluorescence (micro-XRF) and scanning electron microscopy (SEM) analysis were also performed. The results showed that the total concentrations of PTE were higher in <250 μm size fractions of waste rock and soil samples in comparison to the <2 mm size fractions. Mean value of total concentrations of chromium(Cr), copper (Cu), and nickel (Ni) in waste rocks (size fractions <250 μm) were found to be 1299, 1570, and 4010 mg/kg respectively due to the parent material. However, only 11% of Ni in this sample was orally bioaccessible. Detailed analysis of the oral bioaccessible fraction (BAF, reported as the ratio of highest bioaccessible concentration compared with the total concentration from the 250 μm fraction) across all samples showed that Cr, Cu, and Ni varied from 1 to 6%, 14 to 47%, and 5 to 21%, respectively. The variation can be attributed to the difference in pH, organic matter content and mineralogical composition of the samples. Non-specific sequential extraction showed that the non-mobile forms of PTE were associated with the clay and Fe oxide components of the environmental matrices. The present study demonstrates how oral bioaccessibility, solid phase distribution and mineralogical analysis can provide insights into the distribution, fate and behaviour of PTE in waste streams from abandoned mine sites and inform human health risk posed by such sites .
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17593. 题目: Characteristics of atmospheric bacterial and fungal communities in PM_2.5 following biomass burning disturbance in a rural area of North China Plain
文章编号: N18102006
期刊: Science of The Total Environment
作者: Min Wei, Caihong Xu, Xianmang Xu, Chao Zhu, Jiarong Li, Ganglin Lv
更新时间: 2018-10-20
摘要: Biomass burning (BB) in North China Plain has been urgent issue in recent years due to the severe environmental impaction. Bacteria and fungi are ubiquitous in particulate matter. Their taxonomic composition, concentration, ecophysiological functions have potentially important implications in atmospheric biochemical cycle and human health. However, current knowledge about airborne microbes during biomass burning period is scant. Here we investigated bacterial and fungal community composition, abundance and potential function in Yucheng, the center of the North China Plain during summer harvest season in 2014. Monthly field observation suggested serious pollution with high concentration of PM_2.5 and water-soluble ions during biomass burning period. Elevated total bacterial and fungal concentration determined by real-time quantitative PCR was observed for samples during burning events. The predominant bacterial taxa were gram-negative, e.g. Acinetobacter, Cyanobacterium, Janthinobacterium, Massilia, Pseudomonas, accounted for 70.9% of total bacteria. The filamentous fungi Alternaria, Aspergillus, Cladosporium and Penicillium were predominant fungal genera. Metastats analysis showed significant disparity in terms of carbohydrate, amino acids metabolism, human and plant disease predicted by PICRUSt analysis between BB and non-BB events. Microbial community structure were mainly influenced by organic carbon and water-soluble ions (magnesium and potassium) suggested by redundancy analysis (RDA) and co-occurrence analysis. Our data yielded insights into microbial community dynamics following biomass burning disturbance. This study may provide potentially important reference for environmental, agricultural and health management.
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17594. 题目: Trace metal availability in soil horizons amended with various urban waste composts during 17 years – Monitoring and modelling
文章编号: N18102005
期刊: Science of The Total Environment
作者: Philippe Cambier, Aurélia Michaud, Remigio Paradelo, Myriam Germain, Vincent Mercier, Annie Guérin-Lebourg, Agathe Revallier, Sabine Houot
更新时间: 2018-10-20
摘要: Recycling organic residues in agrosystems presents several benefits but faces the question of contaminants, among them a few trace metals which eventually accumulate in soils following regular applications of organic waste products (OWP) and represent an ecological risk. The increase of total trace metal contents in amended topsoils can be predicted by a mass balance approach, but the evolution of their available fractions is a more intricate issue. We aimed at modelling this evolution by using the dataset of a long-term field experiment of OWP applications (manure and three urban waste composts). Two operationally-defined fractions of 6 trace metals have been quantified in the OWP and amended topsoils between 2002 and 2015: the soluble and potentially available metals, extracted in 0.01 M CaCl₂ and 0.05 M EDTA solutions, respectively.The potentially available metals have progressively increased in amended topsoils, at rates depending on elements and types of OWP. For Zn, these increases corresponded in average to inputs of potentially available Zn from OWP. But the soil stocks of potentially available Cu increased faster than from the inputs of EDTA-extractable Cu, showing linear regression slopes between 1.4 and 2.5, depending on OWP type. The influence of OWP has been provisionally interpreted in the light of their efficiency to increase soil organic matter and their inputs of reactive oxides.Soluble copper has increased with repeated amendments. But soluble cadmium, nickel and zinc have generally decreased, as they are influenced by changing soil variables such as pH and organic matter. Statistic models were used to unravel the relationships between soluble and EDTA-extractable metals and other soil variables. For Cu, the most satisfactory models just relate soluble and potentially available Cu. Developing such models could contribute to predict the long-term effects of a precise scenario of agricultural OWP recycling upon available trace metals in soils.
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17595. 题目: Molecular structure-reactivity correlations of humic acid and humin fractions from a typical black soil for hexavalent chromium reduction
文章编号: N18102004
期刊: Science of The Total Environment
作者: Jia Zhang, Huilin Yin, Hui Wang, Lin Xu, Barnie Samuel, Jingjie Chang, Fei Liu, Honghan Chen
更新时间: 2018-10-20
摘要: Different soil humus fractions are structurally distinct from each other molecularly, however, the relationship between their microscopic molecular structures and the macroscopic reduction of Cr(VI) is still unknown, especially for the humin fraction. In this study, different humus fractions (HA, humic acid; HMi, humin linked to iron oxides; HMc, humin linked to clay; and HMr, humin residue) were sequentially extracted from a typical black soil and well characterized. It was found that HA, HMi and HMc were the same type of humus with similar molecular structures, while HMr was structurally different from the other fractions with a high cellulose content. The removal rate of Cr(VI) in solution decreased with progressive humus fractionation, namely, HA > HMi > HMc > HMr. Based on the two-dimensional correlation spectroscopic analysis (2DCOS) of the FTIR data, the changing functional groups of all humus fractions during reacting with Cr(VI) followed a similar order: carboxyl > phenol > hydroxyl > methyl > methylene. According to the correlation analysis, Cr(VI) reduction rates by different humus fractions were mainly determined by the content of phenol (R² = 0.99) instead of carboxyl (R² = 0.28). Except for HMr, the Cr(VI) reduction rates of different humus fractions were also positively correlated with surface and bulk polarity (R² = 0.98 and 0.99) but not with aromaticity or aliphaticity (R² = 0.21).
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17596. 题目: Enhanced removal of Cr(VI) by silicon rich biochar-supported nanoscale zero-valent iron
文章编号: N18102003
期刊: Chemosphere
作者: Linbo Qian, Xiao Shang, Bo Zhang, Wenying Zhang, Anqi Su, Yun Chen, Da Ouyang, Lu Han, Jingchun Yan, Mengfang Chen
更新时间: 2018-10-20
摘要: Silicon-rich biochar-supported nanoscale zero-valent iron (nZVI) was studied to evaluate enhanced removal of hexavalent chromium (Cr(VI)) in solution. The compositional structures of the nZVI and biochar-supported nZVI were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectra before and after Cr(VI) reaction. The removal amount of Cr(VI) by nZVI-RS700 (rice straw pyrolyzed at 700 °C) was considerably greater than that by nZVI and other biochar-supported nZVI samples. Upon the silicon was removed from RS700 (nZVI-RS700(-Si)), a significant decreased removal of Cr(VI) was observed. It was revealed that nZVI supported by silicate particles of biochar and the promotion of iron oxidation by SiO₂ both contribute to the enhanced Cr(VI) removal. We found that the reduction and adsorption both contributed to the removal of Cr(VI), ferrous chromite (FeCr₂O₄) was observed on the surface of the nZVI-RS700 composite. The formation of FeCr₂O₄ is attributed to the reduction of Cr(VI) by nZVI and the adsorption of chromium oxide with iron on the surface of RS700. Therefore, RS700-supported nZVI can be used as a potential remediation reagent to treat Cr(VI)-contaminated groundwater.
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17597. 题目: Immobilization of uranium(VI) in a cementitious matrix with nanoscale zerovalent iron (NZVI)
文章编号: N18102002
期刊: Chemosphere
作者: Youngho Sihn, Sungjun Bae, Woojin Lee
更新时间: 2018-10-20
摘要: We developed a novel solidification and stabilization process using a nanoscale zerovalent iron (NZVI)-cement system for reductive immobilization of hexavalent uranium (U(VI)) in a soil–cement matrix. The NZVI suspension without cement demonstrated high removal efficiency (100% in 2 h) and fast removal kinetics (53.7 Lm⁻²d⁻¹), which surpassed those of other Fe-containing minerals (i.e., green rust, mackinawite, magnetite, and pyrite). Significant removal of aqueous U(VI) was observed in NZVI-cement slurries and minimal adsorbed U was desorbed by a bicarbonate/carbonate (CARB) solution. Surface analysis using scanning electron microscopy and X-ray photoelectron spectroscopy revealed U distributed homogeneously on the surface of the NZVI-cement and transformed considerably from U(VI) to reduced U species by coupled oxidation of Fe(0)/Fe(II) to Fe(III). Furthermore, the increase in pH and NZVI concentration, and presence of humic acid resulted in the enhanced U(VI) reduction in NZVI-cement slurries. The NZVI-cement system was tested with a soil matrix, resulting in successful immobilization of aqueous U(VI) in both batch and column experiments. Moreover, the U(VI) removed in the NZVI-cement system was not leached out by the CARB solution during long-term experiments. The results suggest an NZVI-cement system could represent a promising remediation alternative for effective and stable immobilization of U(VI) in contaminated sites.
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17598. 题目: Unraveling the multiple bottom-up supplies of an Antarctic nearshore benthic community
文章编号: N18102001
期刊: Progress in Oceanography
作者: L. Zenteno, L. Cárdenas, N. Valdivia, I. Gómez, J. Höfer, I. Garrido, LM. Pardo
更新时间: 2018-10-20
摘要: Disentangling the bottom-up controls of natural ecosystems is key to understanding the capacity of local communities to resist natural and anthropogenic disturbances. Here, we used carbon and nitrogen stable isotope ratios with a Bayesian multiple source mixing model to trace diverse food sources supporting the benthic trophic network in Fildes Bay (South Shetland Island, Western Antarctic Peninsula). Individuals of 16 species of consumers and five potential food sources (e.g. inter- and subtidal macroalgae, suspended and sinking particulate organic matter, and particulate organic matter from sediment) were collected during January and February 2017. The results showed that benthic organisms of Fildes Bay assimilate a broad range of available organic matter: most of the energy channeled to upper trophic consumers comes from organic matter in the surface sediment, whereas energy moving among lower trophic consumers comes largely from macroalgae and pelagic primary food sources. Overall, our evidence indicates that the present-day nearshore benthic community of Fildes Bay relies on different primary food sources, channeling bottom-up supplies through multiple pathways, which leads to highly stable systems in the face of current scenarios of global change.

17599. 题目: Distribution and isotopic signature of deep gases in submerged soils in an island of the Lower Delta of the Paraná River, Argentina
文章编号: N18101905
期刊: Environmental Monitoring and Assessment
作者: Romina Sanci, Héctor Osvaldo Panarello
更新时间: 2018-10-19
摘要: Subsoil CH₄ and CO₂ concentrations, δ¹³C-CH₄ and δ¹³C-CO₂ signatures, total organic carbon (TOC) and δ¹³C-TOC, together with C/N ratio of organic matter, were evaluated throughout a soil profile up to the atmosphere to understand the dynamics of CH₄ and CO₂ in the waterlogged environment of an island of the Lower Delta of the Paraná River, Argentina. The analysis of the vertical profile showed that a significant fraction of CH₄ exists as gas trapped within the sediment column, compared to CH₄ dissolved in soil solution. CH₄ concentration measurements in sub-saturated soils showed that free CH₄ is 1 order of magnitude smaller than CH₄ recovered from soil cores by ultrasonic degassing. The highest concentrations of CH₄ occurred at the 90–120-cm layer. At this depth, δ¹³C-CH₄ values resulting from methanogenesis were around − 71‰, which is well within the range of CH₄ produced from CO₂ reduction, and δ¹³C values of the associated CO₂ were enriched (~ − 7‰). Isotope mass balance models used to calculate the fraction of oxidized CH₄ indicated that around 30% of the CH₄ produced was oxidized prior to atmospheric release. In contrast to methanogenesis, during oxidation processes δ¹³C-CH₄ shifts to more positive values. The mineralogical, textural, isotopic, and geochemical characterization of subsoil sediments with abundant organic matter, like Paraná Delta, demonstrated that CH₄ storage capacity of the soil, production, consumption, and transport are the main factors in regulating the actual flux rates of CH₄ to the atmosphere.

17600. 题目: Molecular Characterization of Organics Removed by a Covalently Bound Inorganic–Organic Hybrid Coagulant for Advanced Treatment of Municipal Sewage
文章编号: N18101904
期刊: Environmental Science & Technology
作者: Chun-Xiang Geng, Na Cao, Wei Xu, Chen He, Zi-Wen Yuan, Jin-Wei Liu, Quan Shi, Chun-Ming Xu, Si-Tong Liu, Hua-Zhang Zhao
更新时间: 2018-10-19
摘要: Coagulation is an important process to remove organics from water. The molecular composition and structure of organic matter influence water quality in many ways, and the lack of information regarding the organics removed by different coagulants makes it challenging to optimize coagulation processes and ensure reclaimed water safety. In this paper, we investigated coagulation of secondary biological effluent from a municipal sewage treatment plant with different coagulants. We emphasized investigation of organics removal characteristics at the molecular level using Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI). We found that conventional coagulants can only partially remove condensed polycyclic aromatics and polyphenols with low H/C (H/C < 0.7) and highly unsaturated and phenolic compounds and aliphatic compounds with high O/C (O/C > 0.6). A new coagulant, CBHyC, had better removal efficiencies for all organics with different element compositions and molecular structures, especially organics that are resistant to conventional coagulants such as highly unsaturated and phenolic compounds and aliphatic compounds located in 0.3 < O/C < 0.8 and 1.0 < H/C < 2.0 regions and sulfur-containing compounds with higher O/C (e.g., anionic surfactants and their metabolites or coproducts). This study provides molecular insights into the organics removed by different coagulants and provides data supporting the possible optimization of advanced wastewater treatment processes.
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