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13301. 题目: Combining phytoextraction by Brassica napus and biochar amendment for the remediation of a mining soil in Riotinto (Spain)
文章编号: N19052913
期刊: Chemosphere
作者: G. Gascó, M.L. Álvarez, J. Paz-Ferreiro, A. Méndez
更新时间: 2019-05-29
摘要: Soil contamination in mining areas is an important environmental concern. In these areas, phytoremediation is often impeded because of the low fertility and pH. Assisted phytoremediation is increasingly being used in polluted areas. Biochar could assist plant growth via enhanced soil fertility. An experiment was performed in a mining soil (RIII) from the mining area of Riotinto (Spain) contaminated with Cu, Pb, Zn and As in order to study: (i) The effects of biochar on soil fertility; (ii) Biochar temperature of preparation effect and (iii) Effect of biochar on phytoremediation potential. A mesocosm experiment was designed using Brassica napus as test specie. Soil (RIII) was treated with rabbit manure biochars prepared at 450 °C (BM450) and 600 °C (BM600) at a rate of 10% in mass and incubated for 60 days with or without Brassica napus. Results showed that the combination of BM450 or BM600 with Brassica napus growth decreased the amount of As, Cu, Co, Cr, Se and Pb in the soil. Values of bioaccumulation factor (BAF) for Cd were particularly elevated (>10) in the unamended soil and reached values higher than 1 for other elements, indicating the potential of Brassica napus to accumulate several heavy metals. Translocation Factor (TF) was reduced for Co, Cr, Cd, Cu, Ni, Zn, Pb and As after biochar addition indicating root accumulation of these metals. In all cases, biochar addition increased biomass production. Finally, the addition of BM450 increased GMea index indicating also an improvement on soil quality.
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13302. 题目: Biochar properties and lead(II) adsorption capacity depend on feedstock type, pyrolysis temperature, and steam activation
文章编号: N19052912
期刊: Chemosphere
作者: Jin-Hyeob Kwak, Md Shahinoor Islam, Siyuan Wang, Selamawit Ashagre Messele, M. Anne Naeth, Mohamed Gamal El-Din, Scott X. Chang
更新时间: 2019-05-29
摘要: Biochar is a promising material for facilitating the reclamation of oil sands process water (OSPW); however, how biochar properties can be optimized for metal removal from OSPW is not well studied. This study was conducted to determine relationships among feedstock type, pyrolysis condition, biochar property, and lead(II) adsorption capacity to demonstrate the potential use of biochar for metal removal from a synthetic OSPW. Sawdust, canola and wheat straw, and manure pellet were pyrolyzed at 300, 500, and 700 °C, with or without steam activation. Increasing pyrolysis temperature increased, with a few exceptions, biochar pH, surface area, and carbon content, but decreased hydrogen and oxygen contents and surface functional groups. Steam activation increased surface area but did not affect other properties. For non-steam-activated biochars, canola and wheat straw biochars produced at 700 °C had the highest lead(II) adsorption capacity (Qmax_Pb), at 108 and 109 mg g−1, respectively. Increasing the pyrolysis temperature increased Qmax_Pb due to increased biochar pH, ash content, and surface area by increasing precipitation, ion exchange, and inner-sphere complexation of lead(II). Steam activation increased lead(II) adsorption capacity for most biochars mainly due to the increased surface area, with the highest Qmax_Pb at 195 mg g−1 for canola straw biochar pyrolyzed at 700 °C with steam activation. The adsorption with time followed a pseudo-second order kinetic model. The results of this study will help select most effective biochars that can be produced from locally available agricultural or forestry byproducts that are optimized for metal removal from synthetic OSPW.

13303. 题目: Organic amendments affect dissolved organic matter composition and mercury dissolution in pore waters of mercury-polluted paddy soil
文章编号: N19052911
期刊: Chemosphere
作者: Meng Li, Marios Drosos, Hualing Hu, Xiaosong He, Guoxi Wang, Hui Zhang, Zhengyi Hu, Beidou Xi
更新时间: 2019-05-29
摘要: Organic amendments (OA) have been applied in many mercury (Hg)-polluted paddy soils to meet increasing food demands with scarce land resources. However, little is known on the effects of different OAs on Hg dissolution and the composition of dissolved organic matter (DOM) in soil pore waters, both of which may be associated with Hg mobility. Consequently, DOM composition and Hg release levels were investigated in soil pore waters after applying food waste compost (FC), fulvic acids (FA) and humic acids (HA) to Hg-polluted paddy soils. FA and HA treatments promoted increased abundances of humic- and fulvic-like substances in pore water DOM while FC amendment increased soluble microbial by-products. FA amendment and high levels of both HA and FC amendments greatly promoted Hg dissolution in pore waters that could be attributed to the complexation of Hg with different DOM components. However, among all DOM components, only UVA fulvic and visible humic-like substances were positively correlated with Hg release levels and total organic carbon. These results indicate that discrepant DOM compositions are induced by different OA. Further, these differences may be associated with differential Hg dissolution in pore waters. Consequently, FA amendment and high level of FC or HA amendments should be limited to reduce potential Hg release into pore waters.
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13304. 题目: Co-transport of U(VI), humic acid and colloidal gibbsite in water-saturated porous media
文章编号: N19052910
期刊: Chemosphere
作者: Junwei Yang, Mengtuan Ge, Qiang Jin, Zongyuan Chen, Zhijun Guo
更新时间: 2019-05-29
摘要: The release of uranyl from uranium tailing sites is a widely concerned environmental issue, with limited investigations on the effect of coexistence of various colloids. Gibbsite colloids extensively exist, together with ubiquitous humic substances, in uranium polluted waters at tailing sites, due to high concentration of dissolved Al in acid mine drainage. In this context, we investigated the co-transport of U(VI), gibbsite colloids and humic acid (HA) as a function of pH and ionic strength at a U(VI) concentration (5.0 × 10−5 M) relevant within mine tailings and related waste. It was found that, owing to electrostatic attraction, gibbsite colloids and HA associated with each other and transported simultaneously regardless of U(VI) presence. Besides the impact of pH and ionic strength, whether gibbsite colloids facilitated U(VI) transport depended on HA concentration. Gibbsite colloids impeded U(VI) transport at relatively low HA concentration (≤5 mg L−1), because associated colloids loaded with U(VI) were positively charged which favored colloid retention on negatively charged quartz sand in the column. U(VI) together with gibbsite colloids and low concentration HA was completely blocked at natural pH and/or high ionic strength. At relatively high HA concentration (20 mg L−1), however, the associated colloids showed negative zeta potential which facilitated U(VI) transport because of repulsion between negatively charged colloids and quartz sand. Meanwhile, high concentration of HA dramatically accelerated the transport of gibbsite colloids. These results implied that gibbsite colloids might imped U(VI) migration at uranium tailing sites unless the aquifers are enriched with abundant humic substances.
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13305. 题目: Persulfate and zero valent iron combined conditioning as a sustainable technique for enhancing dewaterability of aerobically digested sludge
文章编号: N19052909
期刊: Chemosphere
作者: Bing-Jie Ni, Xiaofang Yan, Jing Sun, Xueming Chen, Lai Peng, Wei Wei, Dongbo Wang, Shun Mao, Xiaohu Dai, Qilin Wang
更新时间: 2019-05-29
摘要: Aerobic digestion followed by dewatering is a widely applied method for sludge stabilization and reduction in decentralized wastewater treatment plants. It is important to enhance the sludge dewaterability of the aerobically digested sludge due to its considerable impact on cost of sludge disposal and management. In this study, an innovative technique is developed for improving the dewaterability of aerobically digested sludge by combined conditioning with persulfate (PS) and zero valent iron (ZVI). The results demonstrated that the dewaterability of aerobically digested sludge could be significantly enhanced with the PS and ZVI dosage in the range of 0–0.5 g/gTS and 0–0.4 g/gTS, respectively. The highest improvement was achieved at 0.05 g ZVI/g TS with 0.1 g PS/g TS, and the capillary suction time was reduced by ∼80%. The extracellular polymeric substances (EPS) characterization revealed that the combined PS-ZVI treatment could largely reduce proteins, polysaccharides and humic acids-like compounds in the tightly bounded EPS of the aerobically digested sludge, leading to bound water releasing from sludge flocs. The recovery of the ZVI particles could reach around 45%–80% after the treatment, further proved the sustainability of the approach. The proposed PS-ZVI conditioning would not have significant impact on the final choice of sludge disposal and the mainstream wastewater treatment. However, plant-scale test are still required for better assessing the proposed technique.
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13306. 题目: Environmental drivers of benthic community structure in a deep sub-arctic fjord system
文章编号: N19052908
期刊: Estuarine, Coastal and Shelf Science
作者: Èric Jordà Molina, Marc J. Silberberger, Valentin Kokarev, Henning Reiss
更新时间: 2019-05-29
摘要: Fjords are unique geomorphological features that are found globally along (previously) glaciated coasts. They are characteristic for the entire Norwegian coast, where growing human populations and economic development increasingly impact the associated fjord ecosystems, and accordingly basic knowledge about ecosystem structure and functioning is needed. Knowledge about benthic systems within deep basins (over 400 m) of sub-Arctic fjords is currently missing and it remains questionable whether our understanding of similarly deep temperate fjords or shallower sub-arctic fjords is directly transferable to such systems. This study aims to investigate the patterns of soft-bottom benthic communities within a northern Norwegian deep multibasin fjord system and relate them to the prevailing environmental conditions, following a sampling strategy of many-sites with one-sample each. Here we show that oxygen content of the water and organic matter gradients in the sediment, structure the benthic communities of the fjord reflecting the main basins. We found that the community of the deepest basin (>700 m) of this sub-Arctic fjord is similar to the community just outside of Tysfjord at the same depth but differ from other communities within the fjord. Furthermore, the deep basin community reflects deep communities of temperate fjords and the deep Skagerrak. The community within the innermost basin is well adapted to periodic hypoxia with low quality or degraded food supply. Our results demonstrated that fjord specific multibasin topography and the corresponding environmental factors are important drivers of ecological processes, which resulted in distinct benthic communities in each of the three basins. The management of such heterogeneous fjord ecosystems should take an adaptive approach and apply measures that take the differences of these benthic communities into account.

13307. 题目: Soil organic matter pools under management intensification of loblolly pine plantations
文章编号: N19052907
期刊: Forest Ecology and Management
作者: Samantha Mosier, Keith Paustian, Christian Davies, Michael Kane, M. Francesca Cotrufo
更新时间: 2019-05-29
摘要: Early thinning of loblolly pine plantations can potentially deliver sustainable feedstocks for biofuel/bioenergy. However, the management intensification for increased productivity and the removal of additional biomass from these plantations could reduce carbon (C) inputs belowground and therefore reduce overall ecosystem C storage. Increased fertilization could also affect C stocks, and their relative distribution between soil organic matter (SOM) fractions. We analyzed soil C stocks as a function of soil type and different pine plantation management systems across the Western Gulf region of the United States. Additionally, we analyzed SOM fractions with inherently different stabilization mechanisms and potential C persistence. We found no significant differences in bulk soil C stocks across management intensities or soil types. The early thinning treatment had no effect on the C distribution across each soil organic matter fraction. However, proportionally more C was found in mineral-associated organic matter and less in particulate organic matter in the more intensive management regime treatment, possibly due to higher below ground nutrient inputs and enhanced microbial activity. Our results suggest that management intensification to support biofuel production from loblolly pine plantations will not affect soil C stocks, but may increase their persistence. This study demonstrates that, from a soil C perspective, early thinning of intensively managed loblolly pine plantations has potential as a sustainable biofuel feedstock.

13308. 题目: Effects of biochar amendments on antibiotic resistome of the soil and collembolan gut
文章编号: N19052906
期刊: Journal of Hazardous Materials
作者: Jing Ding, Yue Yin, An-Qi Sun, Simon Bo Lassen, Gang Li, Dong Zhu, Xin Ke
更新时间: 2019-05-29
摘要: A diverse array of ARGs has been detected in the guts of soil fauna residing in farmland soil. Biochar has been widely used in farmland for soil remediation and improvement of soil quality; however, the effects of biochar amendment on the gut-associated ARGs of soil fauna remain unclear. In the present study, collembolans were cultivated in soils amended with 6 types of biochars. High-throughput qPCR was used to establish ARG profiles of the collembolan guts as well as the surrounding soils. A total of 73 and 162 subtypes of ARGs were detected in the collembolan guts and soils, respectively. Biochar amendment significantly altered the ARG compositions of the collembolan guts and soils, in a biochar quality-dependent manner. However, only manure-derived biochar, which contained elevated concentrations of heavy metals, increased the relative abundance of gut-associated ARGs. Changes in the gut microbial community, MGEs and biochar properties explained 84% of the total ARG variations in the collembolan guts. The findings of this study suggested that biochar properties should receive more attention, as high doses of heavy metals in biochar could increase the abundance of ARGs in collembolan guts, thereby contributing to the spread of ARGs in the environment through collembolan movement.
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13309. 题目: Organic matter rather than salinity as a predominant feature changes performance and microbiome in methanogenic sludge digesters
文章编号: N19052905
期刊: Journal of Hazardous Materials
作者: Qihong Lu, Zehui Yu, Sining Yu, Zhiwei Liang, Haocong Li, Lianpeng Sun, Shanquan Wang
更新时间: 2019-05-29
摘要: Due to low digestibility and long retention time of anaerobic sludge digestion, pre-treatment with alkaline/acid has been widely employed to enhance the rate and extent of sludge digestion. Nonetheless, effects of gradient concentrations of alkaline/acid pre-treatments and resulting salinity on digestion performance and sludge microbiome remain poorly understood. To elucidate these effects, both batch- and reactor-experiments were setup with varied feeding sludge. Significant digestion improvement and sludge microbiome changes were observed with alkaline/acid sludge pre-treatment, compared to non-pretreatment controls, e.g., ˜88% increase of carbon removal in sludge digesters. Surprisingly, with the same concentration of influent sludge, no notable change in digestion performance and sludge microbiome was observed in digesters when increasing alkaline/acid concentrations from 0.25 to 0.8 mol/L, and in batch serum bottles with or without NaCl amendment. Consequently, organic compounds dissolved in sludge pre-treatment could be a predominant selective pressure driving the performance and microbiome changes. By contrast, salinity as a consequence of the alkaline/acid pre-treatment could only enrich specific lineages, without altering the overall community profile and function. Together, this study provided insights into specific impacts of major factors on digester performance and sludge microbiome, and shed lights on optimization of sludge digestion.

13310. 题目: Eisenia fetida and biochar synergistically alleviate the heavy metals content during valorization of biosolids via enhancing vermicompost quality
文章编号: N19052904
期刊: Science of The Total Environment
作者: Muhammad Bilal Khan, Xiaoqiang Cui, Ghulam Jilani, Ugit Lazzat, Afsheen Zehra, Yasir Hamid, Bilal Hussain, Lin Tang, Xiaoe Yang, Zhenli He
更新时间: 2019-05-29
摘要: Impact of different biochars supplemented (10% w/w) to promote vermicomposting of sewage sludge (SS) and kitchen waste (KW) mixture (SS + KW, 70:30) was studied on the growth, reproduction and survival of earthworms, and ultimately the quality of vermicompost. Four types of biochar used as secondary material for preincubation (16 days) and vermicomposting (30 days) were: pine tree biochar (PTB), poplar plant biochar (PPB), wetland plant biochar (WPB) and yard waste biochar (YWB). Preincubation and vermicomposting of biomass mixture were undertaken in 60 L and 2 L capacity round-shaped bioreactors, respectively. Samples of biomass undergoing degradation were drawn after every 2 days during preincubation and with 5 days interval during vermicomposting to analyze them for plant nutrients and heavy metals contents. Amendment of vermicompost substrate (SS + KW) with biochars; PTB, PPB, WPB and YWB increased the reproduction rate of earthworms (Eisenia fetida) by 44.6, 53.9, 29.3 and 38.8%, respectively as compared to control (no biochar, NB). There has been significant reduction in total content of Cd (0.2–5.1%), Cr (7.3–10.8%), Cu (3.1–7.4%), Mn (3.2–8.4%), Pb (9.0–45.9%) and Zn (1.1–5.7%) by the application of different biochars as compared to NB after vermicomposting. The SEM/EDS images also reflected reduced concentration of these heavy metals in the final vermicompost as compared to initial mixtures. Progressively, biochar amendments increased the concentration of all macronutrients, viz., TN (15.8–31.0%), TP (8.6–9.9%), TK (2.8–17.3%), Ca (4.1–9.9%) and Mg (0.8–12.2%); while, reduced the pH (1.9–2.3%), content of Na (6.6–22.3%), TOC (6.6–15.4%), OM (5.0–8.2%) and C:N ratio (2.6–18.9%). Earthworm body accumulation factor (BAF) of heavy metals was: Cd > Zn > Pb > Cu > Mn > Cr at the termination stage of experiment. In conclusion, amending the SS + KW mixture with 10% (w/w) PPB for vermicomposting rendered higher count of cocoons, growth rate and reproduction rate of earthworms, which ultimately produce nutrients-rich vermicompost lower in heavy metals.
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13311. 题目: Integrated ultrafiltration–capacitive-deionization (UCDI) for enhanced antifouling performance and synchronous removal of organic matter and salts
文章编号: N19052903
期刊: Separation and Purification Technology
作者: Shuai Liang, Min Li, Jun Cao, Kuichang Zuo, Yanhong Bian, Kang Xiao, Xia Huang
更新时间: 2019-05-29
摘要: The crises of water scarcity and energy shortage evoked a desire for compact and energy-efficient water treatment technologies. The present study proposed a novel integrated ultrafiltration–capacitive-deionization (UCDI) process, which achieved a simultaneous removal of organic matter and inorganic salts from wastewater. The organic matter was removed through size exclusion (by the ultrafiltration component) and/or electro-catalytic oxidation, while the inorganic salts were retained via electrosorption by the CDI component. Systematic experiments were conducted to investigate the UCDI behavior. Consequently, the UCDI process achieved an enhanced antifouling performance in both the ultrafiltration and CDI aspects. Besides, the organic matter facilitated the removal of Ca2+- and Mg2+-based ion pairs probably via complexation interaction, but hindered the electrosorption of Na+- and K+-based ion pairs due to site competition. During the desalination, the UCDI system could achieve an up to 100% removal of foulants through electro-catalytic oxidation, suggesting promising applications in various areas.
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13312. 题目: Effects of biochar on the phenol treatment performance and microbial communities shift in sequencing batch reactors
文章编号: N19052902
期刊: Water Research
作者: Shengnan Shi, Jiaxin Liu, Jin Xu, Qianzhi Zeng, Yuan Hou, Bei Jiang
更新时间: 2019-05-29
摘要: The extensive application of biochar (BC) attracts concerns regarding its environmental effect. Wastewater treatment systems are potential BC recipients; however, the impacts of BC on these systems are still unclear. In this study, effects of BC on the phenol treatment performance and shift in microbial communities in sequencing batch reactor (SBR) were investigated. The phenol degradation rates were enhanced in all BC-treated SBRs during the whole operation due to promotion of key enzymes involved in phenol degradation. The decrease in abundance of intracellular reactive oxygen species (ROS) in SBRs indicated that BC protected microorganisms by ameliorating phenol toxicity, leading to a decrease in the secretion of extracellular polymeric substances (EPS). The functional groups, protein (C=O, –CO–NH), polysaccharide (C–OH, C–O–C, C–O), and nucleic acids (O–P–O) associated bonds of EPS decreased or disappeared in BC-treated SBRs. Miseq sequencing revealed significant decrease in bacterial diversity and remarkable changes in the bacterial community structure in BC-treated SBRs. Abundances of Comamonas and Cupriavidus increased significantly upon BC exposure, which contributed to phenol degradation. Treatment with relatively high BC dosage exhibited considerable inhibition on Thauera. Canonical correspondence analysis (CCA) indicated that the shift in abundances of these genera was closely associated with BC dosage. This study suggested that BC exerted protective effects on sludge microbes of phenol wastewater treatment systems, while it affected the bacterial community structure and diversity at test concentrations. Thus, this study elucidates the comprehensive effects of BC on wastewater treatment process.

13313. 题目: Developing surrogate indicators for predicting suppression of halophenols formation potential and abatement of estrogenic activity during ozonation of water and wastewater
文章编号: N19052901
期刊: Water Research
作者: Yu Huang, Shi Cheng, Ya-Ping Wu, Ji Wu, Yan Li, Zong-Li Huo, Ji-Chun Wu, Xian-Chuan Xie, Gregory V. Korshin, Ai-Min Li, Wen-Tao Li
更新时间: 2019-05-29
摘要: This study focused on developing surrogate indicators for predicting oxidation of phenolic groups in dissolved organic matter (DOM), suppression of halophenols' formation potential and abatement of estrogenic activity during ozonation of water and wastewater. The evolution of pH-dependent differential absorbance spectra suggests that O3 preferentially reacts with the DOM phenolic moieties and less so with the aromatic carboxylic groups with increasing O3/DOC (dissolved organic carbon) ratios and changes of UV absorbance and fluorescence. When ozonation used as pretreatment, the formation of halophenols in subsequent chlorination decreased linearly with increasing O3 doses or changes of UV absorbance until it reached 85% suppression of the halophenols' formation from unaltered DOM. The thresholds of decreases of UVA254, UVA280 and humic-like fluorescence corresponding to 85% suppression of halophenols’ formation were in the range of 25%–30%, 30%–35% and 30%–45%, respectively. Pre-ozonation also showed a moderate suppression of haloacetic acids (HAAs) formation potentials, ≤26.5% for reverse osmosis isolate of Suwannee River natural organic matter and ≤31.5% for Yangtze River at applied O3 doses. Measurement of changes of estrogenic activity during ozonation of water and wastewater showed that to attain a >90% abatement of estrogenic activity, the corresponding thresholds of decreases of UVA254, UVA280 and humic-like fluorescence were ∼30%, ∼40%, and ∼70%, respectively. Bromate formation was also suppressed to below 10 μg/L before these thresholds. This study suggests that optimal ozonation conditions and a balance between control of disinfection byproducts (halophenols, HAAs and bromate) and elimination of estrogenic activity can be reached based on online data.
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13314. 题目: Degradation of iohexol by Co2+ activated peroxymonosulfate oxidation: Kinetics, reaction pathways, and formation of iodinated byproducts
文章编号: N19052804
期刊: Chemical Engineering Journal
作者: Hengxuan Zhao, Yuefei Ji, Deyang Kong, Junhe Lu, Xiaoming Yin, Quansuo Zhou
更新时间: 2019-05-28
摘要: Iodinated X-ray contrast media (ICM) are a group of tri-iodinated aromatic compounds used in medical imaging of soft tissues. They are regarded as emerging contaminants, and widely detected in the effluents of wastewater treatment plants, surface water, and groundwater. In the present study, degradation of iohexol, a typical ICM agent, was systematically investigated in a Co2+ activated peroxymonosulfate (Co2+/PMS) oxidation process at neutral conditions. Experimental data revealed that the apparent rate of iohexol degradation was first-order with respect to the concentrations of both Co2+ and PMS. SO4 was found to induce the oxidative degradation of iohexol primarily. Presence of humic acid (HA) significantly inhibited the iohexol degradation, while the influence of Cl was negligible. A total of 11 intermediates were identified by HPLC-MS/MS and three transformation pathways, i.e., cleavage of side chain, H-abstraction from side chain, and oxidative deiodination, were proposed. The degradation started with the oxidation of the side chains in iohexol molecule and followed by deiodination on the aromatic ring. Following the degradation of iohexol, formation of free iodine and iodinated disinfection byproducts (I-DBPs) was found. When 50 µM was treated with 1 mM PMS and 1 µM Co2+, the yields of iodoform and triiodoacetic acid reached 38.12 and 577.99 µg/L, respectively, in 12 h. In addition, the formation of I-DBPs was prominently enhanced by the presence of HA. Because I-DBPs are highly toxic, this study suggests the potential risks when SO4 is applied to degrade ICM compounds.
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13315. 题目: Paleogeographic reconstruction of the Tar – San Martín lacustrine system during late Pleistocene to early Holocene: Landscape availability and hunter-gatherer circulation (Santa Cruz, Argentina)
文章编号: N19052803
期刊: Quaternary International
作者: Luis Rubén Horta, Juan Bautista Belardi, Sergio M. Georgieff, Flavia Carballo Marina
更新时间: 2019-05-28
摘要: This paper presents the paleogeographic reconstructions of flooded areas of the Tar - San Martín lacustrine system during the late Pleistocene - Holocene. The dimensions of lacustrine and glaciolacustrine levels of this basin are higher than the current levels of the lakes. The organic matter of lake levels recorded on stratigraphic profiles was described, sampled and dated using AMS, while other paleobathymetric indicators were also identified (height of the fan-delta apex and paleo-coast levels). Deriving out of the reconstruction of flooded areas it was established that the lake system was formed before 28 ka ago and would have reached its maximum expansion around 12 ka ago. The first hunter-gatherer occupation of the basin (11 ka) corresponds to the period of initial contraction of the lake system and the composition of the current configuration of the coastlines. This scenario would have allowed the exploration of western areas and the gradual incorporation of the forest to the action range of hunter-gatherer populations. Similarly, the levels of lakes Tar and San Martín would not have hindered the movement of human populations through the steppe throughout the Holocene.

13316. 题目: The fate of leaf-litter N under contrasting pedo-climatic conditions in south-western Siberia
文章编号: N19052802
期刊: Soil Biology and Biochemistry
作者: Félix Brédoire, Bernd Zeller, Zachary E. Kayler, Pavel A. Barsukov, Polina Nikitich, Olga Rusalimova, Mark R. Bakker, Alexander Bashuk, Julien Sainte-Marie, Serge Didier, Arnaud Legout, Delphine Derrien
更新时间: 2019-05-28
摘要: Nitrogen (N) made available through the decomposition of organic matter is a major source for plants in terrestrial ecosystems. N cycling in Siberia is however poorly documented despite the region representing a substantial surface area of the globe.We studied the influence of pedo-climate (using two forest-steppe and two southern taiga sites) and vegetation type (aspen forest and grassland) on the redistribution of N released from decomposing 15N-labelled leaf-litter in south-western (SW) Siberia. A model of N dynamics was fit to field measurements that yielded estimates of N mean residence time (MRT) within litter and soil layers, as well as the proportion of N transferred from one layer to another.The release of N from the aspen litter was slower in the forest-steppe (MRT in litter: 2.9–4.6 years) than in the southern taiga (0.9–1.5 years), likely because winter soil freezing and summer drought slowed decomposition in the forest-steppe. In contrast, no difference between the bioclimatic zones was observed for the grass litter (MRT 1.2–1.6 years), suggesting litter chemistry outweighs pedo-climate in these zones. While most of the vertical transfer of N down the soil profile occurred during the vegetative season, important losses were observed after snow-melt. Over three years, the transfer of N within the soil profile was deeper in the southern taiga sites than in the forest-steppe, and in forest than in grassland. In the topsoil, the MRT of N was longer in grassland (4.9–9.4 years) than in forest (1.5–2.1 years) but there were no pronounced differences between bioclimatic zones.The detailed and quantitative view of current N cycling in SW Siberia provided in this study may serve as the basis for informing ecosystem models that anticipate future climate and land-use changes.
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13317. 题目: Fire influences needle decomposition: Tipping point in Pinus radiata carbon chemistry and soil nitrogen transformations
文章编号: N19052801
期刊: Soil Biology and Biochemistry
作者: E. Stirling, R.J. Smernik, L.M. Macdonald, T.R. Cavagnaro
更新时间: 2019-05-28
摘要: As climate change proceeds, a change in the frequency and intensity of fire events is expected to affect soil organic matter (SOM) transformations within forestry systems. A likely consequence is the development of post-fire litter layers composed of thermally altered non-senescent materials that have fallen during a fire event. In this study, Pinus radiata needles were thermally altered to determine the effect of changes in carbon chemistry on needle decomposition and nitrogen cycling. Live needles were collected and dried at 40 °C before being further heated for 1 h in a muffle furnace at a range of temperatures >40 °C (max. = 320 °C) to simulate a range of canopy temperatures that can occur during a fire, and then coarsely ground and screened (0.5–1.0 mm fraction retained). These needles were characterized for carbon and nitrogen content, and carbon chemistry (solid-state 13C NMR spectroscopy); they were also used in an incubation experiment (14 days) which was performed to assess the impact of heating on nitrogen transformations. Soil respiration and extractable nitrogen pools (mineral, potentially mineralizable, and microbial biomass) were measured throughout the incubation. During the incubation, cumulative respiration and nitrogen absorption capacity decreased with increasing thermal alteration. The results indicate a step change in the response of nitrogen pools to thermal alteration of pine needles, with a critical change occurring at or before 200 °C. This step change in nitrogen response may be due to the thermal degradation of light fraction organic matter, simple polysaccharides, or both. From this experiment it is clear that a post fire litter layer can have distinctly different effects on the soil environment depending on canopy temperature conditions during the fire with post fire litters composed of low temperature needles absorbing most mineral nitrogen that they contact. This will in turn affect post-fire plant recovery and therefore ecological succession.

13318. 题目: Review: mine tailings in an African tropical environment—mechanisms for the bioavailability of heavy metals in soils
文章编号: N19052706
期刊: Environmental Geochemistry and Health
作者: Belinda K. Kaninga, Benson H. Chishala, Kakoma K. Maseka, Godfrey M. Sakala, Murray R. Lark, Andrew Tye, Michael J. Watts
更新时间: 2019-05-27
摘要: Heavy metals are of environmental significance due to their effect on human health and the ecosystem. One of the major exposure pathways of Heavy metals for humans is through food crops. It is postulated in the literature that when crops are grown in soils which have excessive concentrations of heavy metals, they may absorb elevated levels of these elements thereby endangering consumers. However, due to land scarcity, especially in urban areas of Africa, potentially contaminated land around industrial dumps such as tailings is cultivated with food crops. The lack of regulation for land-usage on or near to mine tailings has not helped this situation. Moreover, most countries in tropical Africa have not defined guideline values for heavy metals in soils for various land uses, and even where such limits exist, they are based on total soil concentrations. However, the risk of uptake of heavy metals by crops or any soil organisms is determined by the bioavailable portion and not the total soil concentration. Therefore, defining bioavailable levels of heavy metals becomes very important in HM risk assessment, but methods used must be specific for particular soil types depending on the dominant sorption phases. Geochemical speciation modelling has proved to be a valuable tool in risk assessment of heavy metal-contaminated soils. Among the notable ones is WHAM (Windermere Humic Aqueous Model). But just like most other geochemical models, it was developed and adapted on temperate soils, and because major controlling variables in soils such as SOM, temperature, redox potential and mineralogy differ between temperate and tropical soils, its predictions on tropical soils may be poor. Validation and adaptation of such models for tropical soils are thus imperative before such they can be used. The latest versions (VI and VII) of WHAM are among the few that consider binding to all major binding phases. WHAM VI and VII are assemblages of three sub-models which describe binding to organic matter, (hydr)oxides of Fe, Al and Mn and clays. They predict free ion concentration, total dissolved ion concentration and organic and inorganic metal ion complexes, in soils, which are all important components for bioavailability and leaching to groundwater ways. Both WHAM VI and VII have been applied in a good number of soils studies with reported promising results. However, all these studies have been on temperate soils and have not been tried on any typical tropical soils. Nonetheless, since WHAM VII considers binding to all major binding phases, including those which are dominant in tropical soils, it would be a valuable tool in risk assessment of heavy metals in tropical soils. A discussion of the contamination of soils with heavy metals, their subsequent bioavailability to crops that are grown in these soils and the methods used to determine various bioavailable phases of heavy metals are presented in this review, with an emphasis on prospective modelling techniques for tropical soils.

13319. 题目: Changes in soil organic matter stability with depth in two alpine ecosystems on the Tibetan Plateau
文章编号: N19052705
期刊: Geoderma
作者: Yanhui Hou, Ying Chen, Xiao Chen, Keyi He, Biao Zhu
更新时间: 2019-05-27
摘要: Soil organic carbon (SOC) decomposition can potentially feedback to climate change. However, the biotic, abiotic and inherent factors controlling the stability of soil carbon, and changes in these factors with soil depth, remain poorly understood. In this study, we combined a number of complementary methods to quantify the biological, thermal, chemical, molecular and isotopic indices of soil organic matter (SOM) stability along the soil profile (0–70 cm) in two contrasting alpine ecosystems (meadow and shrubland) on the Tibetan Plateau. Firstly, we conducted an aerobic lab–incubation experiment on root–free, sieved soils. The number of days to respire 5% of initial SOC, a biological index of SOM stability, decreased with soil depth. Moreover, the temperature at which half of SOM mass loss (TG–T50), a thermal index of SOM stability, increased with soil depth. Additionally, hot–water extractable organic carbon (HWEOC) per gram SOC, a chemical index of SOM stability, showed weak (meadow) and little (shrubland) declining trend with depth. Further, we used Fourier–transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy to characterize the molecular composition of SOM. The index of recalcitrance of FTIR spectra and the combined index of aliphaticity and aromaticity of NMR spectra both increased with depth, suggesting that the molecular composition of SOM was more complex with increasing depth. Finally, the isotopic values of SOM (13C and 15N) and the 14C–based SOC turnover time both increased with depth, indicating that the isotopic indices of SOM stability also increased with depth. Overall, our results suggest that the thermal, chemical, molecular and isotopic indices of SOM stability were mutually correlated and all showed increasing trend with increasing soil depth in the two alpine ecosystems, although the biological index (as measured by aerobic incubation of root–free sieved soils) showed the opposite results.

13320. 题目: Revealing chlorinated ethene transformation hotspots in a nitrate-impacted hyporheic zone
文章编号: N19052704
期刊: Water Research
作者: John J. Weatherill, Stefan Krause, Sami Ullah, Nigel J. Cassidy, Amir Levy, Falko P. Drijfhout, Michael O. Rivett
更新时间: 2019-05-27
摘要: Hyporheic zones are increasingly thought of as natural bioreactors, capable of transforming and attenuating groundwater pollutants present in diffuse baseflow. An underappreciated scenario in the understanding of contaminant fate hyporheic zones is the interaction between point-source trichloroethene (TCE) plumes and ubiquitous, non-point source pollutants such as nitrate. This study aims to conceptualise critical biogeochemical gradients in the hyporheic zone which govern the export potential of these redox-sensitive pollutants from carbon-poor, oxic aquifers. Within the TCE plume discharge zone, discrete vertical profiling of the upper 100 cm of sediment pore water chemistry revealed an 80% increase in dissolved organic carbon (DOC) concentrations and 20–60 cm thick hypoxic zones (<2 mg O2 L−1) within which most reactive transport was observed. A 33% reduction of nitrate concentrations coincided with elevated pore water nitrous oxide concentrations as well as the appearance of manganese and the TCE metabolite cis-1,2-dichloroethene (cDCE). Elevated groundwater nitrate concentrations (>50 mg L−1) create a large stoichiometric demand for bioavailable DOC in discharging groundwater. With the benefit of a high-resolution grid of pore water samplers investigating the shallowest 30 cm of hypoxic groundwater flow paths, we identified DOC-rich hotspots associated with submerged vegetation (Ranunculus spp.), where low-energy metabolic processes such as mineral dissolution/reduction, methanogenesis and ammonification dominate. Using a chlorine index metric, we show that enhanced TCE to cDCE transformation takes place within these biogeochemical hotspots, highlighting their relevance for natural plume attenuation.
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