论文检索

总访问量：4109498次

总访客量：170630人

所有论文

28541. 题目: Bioremediation of arsenic-contaminated groundwater by sequestration of arsenic in biogenic pyrite
文章编号: N18071911
期刊: Applied Geochemistry
作者: James A. Saunders, Ming-Kuo Lee, Prakash Dhakal, Shahrzad Saffari Ghandehari, Ted Wilson, M. Zeki Billor, Ashraf Uddin
更新时间: 2018-07-19
摘要: Pyrite (FeS2) is the most common sulfide mineral in the Earth's crust, and it commonly contains minor amounts of arsenic. Here we show that authigenic pyrite can remove arsenic from contaminated groundwater and this can be used as a new and relatively inexpensive remediation process. Laboratory batch experiments presented show that fine-grain natural pyrite is an effective sorber of dissolved arsenic. Arsenic sorption onto pyrite is shown to increase with increasing pH, particularly at pH > 5 and at elevated dissolved arsenic concentration. We also present results from a field experiment at an arsenic-contaminated industrial site, which demonstrates the results of stimulation of natural sulfate-reducing bacteria in groundwater by injection of a labile organic carbon source, iron, and sulfate. Within a week, bacterial sulfate reduction triggered the formation of biogenic pyrite nanoparticles, which sequestered arsenic by adsorption and co-precipitation. Microscopic and X-ray diffraction analyses confirmed that pyrite was the only iron-sulfide formed, and that no arsenic-only sulfide phase precipitated (e.g. orpiment or realgar). Pyrite occurs as either 1–10 μm euhedral crystals or similar-sized framboids both of which contain 500–4000 mg/kg arsenic. As a result, dissolved arsenic decreased from its initial concentration of 0.3–0.5 mg/L to below the regulatory clean-up standard for the site of 0.05 mg/L in a matter of weeks. In addition to the potential of this technique to remediate anthropogenic arsenic contamination, it is possible that it can be modified to inexpensively treat individual small drinking-water wells contaminated by natural sources of arsenic in many developing nations.

28542. 题目: Scenario modeling for spatial-temporal change detection of carbon storage and sequestration in a forested landscape in Northern Iran
文章编号: N18071910
期刊: Environmental Monitoring and Assessment
作者: Ardavan Zarandian, Jalil Badamfirouz, Roya Musazadeh, Alireza Rahmati, Seyedeh Bahareh Azimi
更新时间: 2018-07-19
摘要: The present study was conducted, based on scenario modeling approach, in the Do-hezar and Se-hezar forested landscape in the Mazandaran Province in Northern Iran in order to detect spatial-temporal changes of carbon storage and sequestration in four different carbon pools, i.e., aboveground and belowground biomasses, dead organic matter, and organic soils. For this purpose, firstly, the changing trend of land use/land cover (LULC) was detected by analyzing and comparing remotely sensed data of the landscape during the period of 1984–2016. Then, the impacts of future LULC changes on carbon storage and sequestration were predicted and valued using the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model under two future plausible scenarios of business as usual (BAU) and balanced development (BD). According to the results of BAU scenario, continuation of the current trend will lead to a significant reduction in the carbon sequestration and a huge amount of social cost due to the loss of carbon stored in the landscape and its release to the atmosphere. The BD scenario which refers to the principled and under control development of human settlements simultaneously with forest conservational and restoration activities, could potentially reverse the downtrend of carbon sequestration service and avoid future socioeconomic costs, hence add to the economic value of the forest landscape in terms of providing a better sink for carbon storage. The results of this research can facilitate the quantitative and accurate assessment of carbon storage and sequestration relying on more precise biophysical and economic data as well as provide insight for effective land-use planning.

28543. 题目: Soil aggregates: a scale to investigate the densities of metal and proton reactive sites of organic matter and clay phases in soil
文章编号: N18071909
期刊: European Journal of Soil Science
作者: L. Spadini, A. Navel, J. M. F. Martins, E. Vince , I. Lamy
更新时间: 2018-07-19
摘要: Determining site density of reactive sites of metals in the main soil phases remains a challenging task. This study aimed to show that densities of reactive sites in soil may be assessed by a fractionation procedure based on soil being spatially organized as aggregates. The method is described with copper as a model trace element and a common silty loam soil after applying a low energy fractionation method to maintain the integrity of soil aggregates. The reactivity of five soil size fractions (> 250, 250–63, 63–20, 20–2 and < 2 μm) to protons and copper was quantified by acid–base titrations. The total proton sorption capacities were assigned to the total concentration of copper reactive sites and fitted to a linear combination of the relevant reactivity data of each phase, namely the total contents of organic carbon, copper and acid‐extractable aluminium. Acid–base reactivity was linearly related to the distribution of copper, and differences between fractions were used to reconstruct the distribution of acid–base and copper‐complexing sites among the clay, organic and weakly reactive residual phases. In accordance with our hypothesis that key reactive phases are mainly organic materials and clays, we used this procedure to determine the site densities of (i) two size classes of particulate organic matter, (ii) strongly reactive organic matter (e.g. soil humic and fulvic acids) and (iii) clay. The site densities and the distributions of copper obtained were used to validate our conceptual model for predicting global soil reactivity to metals.

28544. 题目: Drivers of postfire soil organic carbon accumulation in the boreal forest
文章编号: N18071908
期刊: Global Change Biology
作者: Benjamin Andrieux, Julien Beguin, Yves Bergeron, Pierre Grondin, David Paré
更新时间: 2018-07-19
摘要: The accumulation of soil carbon (C) is regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the main drivers of soil C accumulation in the boreal forest of eastern North America. Ecosystem C pools were measured in 72 sites of fire origin that burned 2–314 years ago over a vast region with a range of mean annual temperature of 3°C and one of 500 mm total precipitation. We used a set of multivariate a priori causal hypotheses to test the influence of time since fire (TSF), climate, soil physico‐chemistry and bryophyte dominance on forest soil organic C accumulation. Integrating the direct and indirect effects among abiotic and biotic variables explained as much as 50% of the full model variability. The main direct drivers of soil C stocks were: TSF >bryophyte dominance of the FH layer and metal oxide content >pH of the mineral soil. Only climate parameters related to water availability contributed significantly to explaining soil C stock variation. Importantly, climate was found to affect FH layer and mineral soil C stocks indirectly through its effects on bryophyte dominance and organo‐metal complexation, respectively. Soil texture had no influence on soil C stocks. Soil C stocks increased both in the FH layer and mineral soil with TSF and this effect was linked to a decrease in pH with TSF in mineral soil. TSF thus appears to be an important factor of soil development and of C sequestration in mineral soil through its influence on soil chemistry. Overall, this work highlights that integrating the complex interplay between the main drivers of soil C stocks into mechanistic models of C dynamics could improve our ability to assess C stocks and better anticipate the response of the boreal forest to global change.

28545. 题目: Relationships between DOC and CDOM based on the total carbon‐specific fluorescence intensities for river waters across China
文章编号: N18071907
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ying Zhao, Kaishan Song
更新时间: 2018-07-19
摘要: Weak correlations between chromophoric dissolved organic matter (CDOM) absorption coefficient a(440) and dissolved organic carbon (DOC) were observed due to weak absorption for river waters especially in the Qinghai‐Tibetan Plateau and thus it is impossible to estimate DOC concentrations by CDOM absorption across China. Therefore, it is necessary to estimate DOC concentrations through the fluorescent fraction of CDOM (i.e., FDOM). FDOM was proposed as a new method for estimation of large‐scale DOC concentrations in river waters across China. A total of 301 water samples from eight river basins across China were selected to assess FDOM by excitation‐emission matrix (EEM) fluorescence. Five fluorescent regions were obtained by EEM coupled with fluorescence regional integration (FRI) (EEM‐FRI) method. However, weak correlations between the fluorescence intensities FR(1‐5), FSUM and DOC concentrations were observed for all water samples, respectively. Therefore, the total carbon‐specific fluorescence intensities FSUM/DOC were used to establish relationships between DOC and FDOM. All 301 water samples excluding five outliers with FSUM/DOC higher than 8000 nm·(mg L–1)–1), were divided into four groups based on the threshold values for FSUM/DOC and strong positive correlations between FSUM and DOC were observed in each group (R2 = 0.843, FSUM/DOC < 1000 nm·(mg L–1)–1; R2 = 0.928, 1000 < FSUM/DOC < 2000 nm·(mg L–1)–1; R2 = 0.964, 2000 < FSUM/DOC < 3000 nm·(mg L–1)–1; R2 = 0.953, 3000 < FSUM/DOC < 8000 nm·(mg L–1)–1), respectively. This result indicated the riverine DOC concentrations on large scale across China can be estimated directly by FDOM properties.

28546. 题目: Is the adsorption of soil organic matter to haematite (α‐Fe2O3) temperature dependent?
文章编号: N18071906
期刊: European Journal of Soil Science
作者: M. L. Nguyen, W. C. Hockaday, B. L. T. Lau
更新时间: 2018-07-19
摘要: Soil organic matter interactions with minerals are a key determinant in the long‐term protection and sequestration of carbon in soils and sediments. Climate warming could potentially alter the dynamics of the Earth's largest carbon pools through processes controlling the formation of mineral–organic associations (MOAs). We studied the adsorption of Elliott soil humic acid (HA) and fulvic acid (FA) to the iron oxide mineral haematite (α‐Fe2O3) at temperatures from 15 to 35°C through batch sorption experiments. The ΔG°, ΔH° and ΔS° of sorption were derived for HA and FA and suggested that formation of MOAs was spontaneous and exothermic. The Langmuir sorption coefficients for HA and FA decreased with warming, but the maximum sorption capacities were not temperature dependent. The decrease in sorption coefficient was less when the temperature was increased from 30 to 35°C than from 15 to 30°C. Our infrared, ultraviolet and visible spectroscopy analysis of the bound and unbound HA and FA revealed preferential adsorption of oxygen‐ and hydrogen‐substituted aromatic and aliphatic carbon, which was independent of temperature. The adsorption of a hydrophobic probe molecule, Rose Bengal, to haematite increased with warming. Our results suggest that (i) MOAs in warmer climates might be less sensitive to temperature changes, (ii) the amount of iron oxide‐associated organic matter might remain unchanged with warming and (iii) hydrophobic interactions with iron oxides may be temperature dependent.

28547. 题目: Distinct changes in composition of soil organic matter with length of cropping time in subsoils of a Phaeozem and Chernozem
文章编号: N18071905
期刊: European Journal of Soil Science
作者: Y.‐L. Zhang, L.‐J. Li, S.‐H. Yao, J.‐D. Mao, K. Schmidt‐Rohr, D. C. Olk, X.‐Y. Cao, J.‐F. Cui, B. Zhang
更新时间: 2018-07-19
摘要: Deeper soil horizons might provide an opportunity to enhance C sequestration because soil organic matter (SOM) at depth is assumed to be stable. However, it is unknown whether the stable composition of organic carbon in subsoils changes with the length of cropping time and the type of soil. The objectives of this study were to determine the effects on the chemical structures of SOM of cropping time after conversion from grassland to arable land under a Phaeozem and Chernozem in northeast China. Near‐quantitative multiple cross‐polarization (multiCP) 13C nuclear magnetic resonance (NMR) spectroscopy was applied, and 11 types of carbon (C) functional groups were identified. Principal component analysis of these functional groups showed that the chemical composition of SOM was differentiated by soil type and depth. The Phaeozem and Chernozem profiles differed mainly in their relative proportions of aromatic C–C and (CH2)n groups: the Phaeozem contained relatively more aromatic C–C, whereas the Chernozem contained relatively more (CH2)n groups. The fused‐ring aromatic C–C carbon was probably derived from char‐like organic matter generated by burning of plant litter or from SOM humification, whereas the (CH2)n groups were likely to be from plant‐ or microbially‐derived residues. The main differences between top‐ and sub‐soils were the occurrence of more protonated C in the topsoils and more non‐protonated C in the subsoils. With increasing length of cropping time, aromatic C–C and C–O groups and COO/N–C=O groups increased, but (CH2)n groups decreased in the Phaeozem subsoils and increased in the Chernozem subsoils. Our findings suggested that leaching and soil moisture might influence the origin, redistribution and transformation of the recalcitrant components of SOM in the soil profile, resulting in changes in SOM composition under different climates and soil types.

28548. 题目: Dependency of Antarctic zooplankton species on ice algae‐produced carbon suggests a sea ice‐driven pelagic ecosystem during winter
文章编号: N18071904
期刊: Global Change Biology
作者: Doreen Kohlbach , Martin Graeve , Benjamin A. Lange , Carmen David , Fokje L. Schaafsma , Jan Andries van Franeker , Martina Vortkamp , Angelika Brandt , Hauke Flores
更新时间: 2018-07-19
摘要: How the abundant pelagic life of the Southern Ocean survives winter darkness, when the sea is covered by pack‐ice and phytoplankton production is nearly zero, is poorly understood. Ice‐associated (‘sympagic’) microalgae could serve as a high‐quality carbon source during winter, but their significance in the food web is so far unquantified. To better understand the importance of ice algae‐produced carbon for the overwintering of Antarctic organisms, we investigated fatty acid (FA) and stable isotope compositions of 10 zooplankton species, and their potential sympagic and pelagic carbon sources. FA‐specific carbon stable isotope compositions were used in stable isotope mixing models to quantify the contribution of ice algae‐produced carbon (αIce) to the body carbon of each species. Mean αIce estimates ranged from 4 to 67%, with large variations between species and depending on the FA used for the modeling. Integrating the αIce estimates from all models, the sympagic amphipod Eusirus laticarpus was the most dependent on ice algal carbon (αIce: 54‐67%), and the salp Salpa thompsoni showed the least dependency on ice algal carbon (αIce: 8‐40%). Differences in αIce estimates between FAs associated with short‐term versus long‐term lipid pools suggested an increasing importance of ice algal carbon for many species as the winter season progressed. In the abundant winter‐active copepod Calanus propinquus, mean αIce reached more than 50% in late winter. The trophic carbon flux from ice algae into this copepod was between 3 and 5 mg C m-2 d-1. This indicates that copepods and other ice‐dependent zooplankton species transfer significant amounts of carbon from ice algae into the pelagic system, where it fuels the food web, the biological carbon pump and elemental cycling. Understanding the role of ice algae‐produced carbon in these processes will be the key to predictions of the impact of future sea ice decline on Antarctic ecosystem functioning.

28549. 题目: Differential responses of carbon‐degrading enzymes activities to warming: implications for soil respiration
文章编号: N18071903
期刊: Global Change Biology
作者: Ji Chen, Yiqi Luo, Pablo García‐Palacios, Junji Cao, Marina Dacal, Xuhui Zhou, Jianwei Li, Jianyang Xia, Shuli Niu, Huiyi Yang, Shelby Shelton, Wei Guo, Kees Jan van Groenigen
更新时间: 2018-07-19
摘要: Extracellular enzymes catalyze rate‐limiting steps in soil organic matter decomposition, and their activities (EEAs) play a key role in determining soil respiration (SR). Both EEAs and SR are highly sensitive to temperature, but their responses to climate warming remain poorly understood. Here, we present a meta‐analysis on the response of soil cellulase and ligninase activities and SR to warming, synthesizing data from 56 studies. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in SR, while no such relationship was found for cellulase. The warming response of ligninase activity was more closely related to the responses of SR than a wide range of environmental and experimental methodological factors. Furthermore, warming effects on ligninase activity increased with experiment duration. These results suggest that soil microorganisms sustain long term increases in SR with warming by gradually increasing the degradation of the recalcitrant carbon pool.

28550. 题目: Effect of contrasting tillage and cropping systems on soil aggregation, carbon pools and aggregate‐associated carbon in rainfed Vertisols
文章编号: N18071902
期刊: European Journal of Soil Science
作者: J. Somasundaram, R. S. Chaudhary, D. Awanish Kumar, A. K. Biswas, N. K. Sinha, M. Mohanty, K. M. Hati, P. Jha, M. Sankar, A. K. Patra, R. Dalal, S. K. Chaudhari
更新时间: 2018-07-19
摘要: Worldwide, conservation agriculture practices involving minimal soil disturbances and retention of crop residue (>30%) have been practised increasingly and recognized to enhance soil health by optimizing key soil attributes. However, little information is available on the short‐term effects of conservation agriculture practices on soil properties under rainfed Vertisols of Central India. Thus, our aim was to study the short‐term effects of contrasting tillage treatments and cropping systems on soil aggregation, aggregate‐associated carbon (C), carbon pools and crop productivity. This study comprised three tillage systems (TS), reduced tillage (RT), no tillage (NT) with retention of crop residue and conventional tillage (CT), together with four cropping systems (CS), namely soya bean (Glycine max L.) + pigeon pea (Cajanus cajan L.) (2:1), soya bean–wheat (Titricum durum L.), maize (Zea mays L.) + pigeon pea (1:1), and maize–chickpea Cicer arietinum L.). The experiment was laid out in a split‐plot design with three replicates. Soil samples were collected at four depths: 0–5, 5–15, 15–30 and 30–45 cm from the experimental field after completion of four crop cycles. Results indicated that at depths 0–5 and 5–15 cm, tillage and cropping system had a significant effect on aggregate mean weight diameter (MWD). The MWDs of 0.97 and 0.94 mm were larger for NT than CT (0.77 and 0.83 mm) at 0–5‐ and 5–15‐cm depths, respectively. Water‐stable aggregates (WSAs) were also larger for NT (70.74%) and RT (70.09%) than CT (59.50%) at 0–5 cm. Tillage practice, cropping system and their interaction had a greater effect (P < 0.05) on the content of aggregate‐associated C for large macroaggregates (LM). There was more aggregate‐associated C for NT and RT at 0–5‐cm depth than for CT. Cropping system also had a significant effect (P < 0.05) on aggregate‐associated C at 0–5‐cm depth. Soil organic C (%) fractions were in the order of non‐labile >very labile >less labile >labile for 0–5‐ and 5–15‐cm depths after four crop cycles. Less labile and non‐labile C fractions contributed >50% of TOC, indicating a more recalcitrant form of carbon present in the soil. Tillage had no significant effect (P > 0.05) on crop yields after four crop cycles. Conservation agriculture can have a positive effect on aggregate stability, aggregate‐associated C and different carbon pools in a Vertisol.

28551. 题目: Ash and fire, char, and biochar in the environment
文章编号: N18071901
期刊: Land Degradation & Development
作者: Yakov Kuzyakov, Agustin Merino， Paulo Pereira
更新时间: 2018-07-19
摘要: Fire is an extreme event leading to rapid and dramatic losses of carbon (C), nutrients, and ballast elements from ecosystems and leaving ash and char on the soil surface. This affects soil processes, properties, and functions. Similar effects can be induced by applying biochar—the product of artificial pyrolysis of plant materials and organic wastes. The nutrients in ashes remaining after a fire or in biochar after pyrolysis will be leached within a few years, and only the highly condensed material will remain in the soil over centuries and millennia. This Special Issue (SI) is devoted to ash, fire, char, and biochar in the environment, with a special focus on soil processes and properties. We begin by comprehensively summarizing the positive and negative effects of fire, ash, char, and biochar on the physical, chemical, and biological properties of soils. We then review the 15 papers contributing to this SI. The first group of studies focuses on reconstructing fires during the Holocene and then linking them to human activities and land use. These studies clearly concluded that the fire frequency strongly increased with human invasion and occupation, and that charcoal properties are useful in reconstructing anthropogenic activities. The second group of studies is mainly devoted to changes in physical, chemical, and biological soil properties as well as to interactions between soil functions depending on fire, ash, and char properties. The final group describes the effects of biochar on soil properties and functions such as nutrient availability, C sequestration, microbial diversity and community structure, and heavy metal fixation. The overall conclusion is that fire and the remaining ash and char as well as the application of biochar have short‐ and long‐term consequences for soil. Despite the dramatic effects of fire on vegetation, these factors have many positive effects on soil properties and functions, whereby the influences extend from local, landscape, and regional scales to the global scale.

28552. 题目: Quantification of lipid biomarkers in sedimentary contexts: comparing different calibration methods
文章编号: N18071817
期刊: Organic Geochemistry
作者: Antonio V. Herrera-Herrera, Carolina Mallol
更新时间: 2018-07-18
摘要: The analysis of lipid biomarkers has gained increasing importance within environmental and archaeological fields because they are representative of particular plant and animal sources. Accurate quantification of such compounds is essential to obtaining significant information. In this paper, accuracy in the quantification of n-alkanes (as model compounds) in sedimentary contexts was studied using three different approaches: proportions of areas with regards to an internal standard, instrumental calibration and matrix-matched calibration. Alkanes were extracted by ultrasonic assisted solid-liquid extraction and analyzed by gas chromatography coupled to mass spectrometry. Instrumental calibration curves were obtained with determination coefficients (R2) higher than 0.9900. The matrix effect was studied (in the range between -100% and 140%) and matrix-matched calibration curves with R2 above 0.9904 were obtained. Matrix matched calibration provided the best results (percentages in the range 10-130%) when compared with instrumental calibration (1-142%) and no calibration (2-274%). Four sediment samples from an archaeological Neanderthal site were analyzed with the three quantification methods and a Student s t test demonstrated that the results obtained were significantly different: Concentrations were non-uniformly under- or overestimated, and the highest peak and the alkane profile varied with the different methods. According to these data, matrix-matched calibration should be the preferred method for quantification since results are more accurate with only a small amount of extra work. This method requires that control sediment samples are collected at the site under consideration.

28553. 题目: Influence of new agromining cropping systems on soil bacterial diversity and the physico-chemical characteristics of an ultramafic soil
文章编号: N18071816
期刊: Science of The Total Environment
作者: Ramez F. Saad, Ahmad Kobaissi, Guillaume Echevarria, Petra Kidd, Magdalena Calusinska, Xavier Goux, Emile Benizri
更新时间: 2018-07-18
摘要: Most of the research dedicated to agromining has focused on cultivating a single hyperaccumulator plant, although plant diversity has been shown to positively modify soil characteristics. Hence, we compared the effect of cropping a nickel-hyperaccumulator Alyssum murale with a legume (Vicia sativa) to A. murale's mono-culture, on the bacterial diversity and physico-chemical characteristics of an ultramafic soil. A pot experiment with 5 replicates was conducted in controlled conditions for 11 months. The treatments studied were: co-cropping and rotation vs. mineral fertilization controls and bare soil. The introduction of legumes induced a clearly positive effect on the soil's microbial biomass carbon and nitrogen. Arylsulfatase and urease activities tended to be enhanced in the co-cropping and rotation treatments and to be lessened in the mineral fertilization treatments. However, β-glucosidase and phosphatase activities were seen to decrease when legumes were used. Our results showed that the rotation treatment induced a higher organic matter content than the fertilized control did. Actinobacteria was the most-represented bacterial phyla and had lower relative abundance in treatments associating legumes. Conversely, the relative abundance of Acidobacteria and Gemmatimonadetes phyla increased but not significantly in treatments with legumes. The relative abundance of Chloroflexi phylum was shown to be significantly higher for the fertilized rotation control. The relative abundance of β-Proteobacteria subphylum increased but not significantly in treatments with legumes. NMDS analysis showed a clear separation between planted treatments and bare soil and between co-cropping and rotation and fertilized controls. Shannon index showed reduction in microbial diversity that was mainly due to chemical inputs in the soil. This study showed that these new cropping systems influenced both the bacterial diversity and the physico-chemical characteristics of an ultramafic soil. In addition, this study provides evidence that mineral fertilization can negatively impact bacterial communities and some of their functions linked to biogeochemical cycles.

28554. 题目: Towards a better understanding of the aggregation mechanisms of iron (hydr)oxide nanoparticles interacting with extracellular polymeric substances: Role of pH and electrolyte solution
文章编号: N18071815
期刊: Science of The Total Environment
作者: Di Lin, Peng Cai, Caroline L. Peacock, Yichao Wu, Chunhui Gao, Wanxi Peng, Qiaoyun Huang, Wei Liang
更新时间: 2018-07-18
摘要: Extracellular polymeric substances (EPS) are ubiquitous in the soil and water environment and interact strongly with mineral surfaces. However, these interactions and their impacts on the behavior and fate of minerals remain poorly understood. Here, for a better understanding of the colloidal stability of minerals in the environment, we investigated the aggregation of goethite (α-FeOOH) nanoparticles (NPs) in the presence of EPS from Bacillus subtilis under different environmental conditions (pH, ionic strength and ionic valence). Results showed that the aggregation processes of goethite NPs are determined by the solution chemistry, and the colloidal stability of goethite NPs is strongly influenced by the addition of EPS. In the absence of ionic strength, the addition of EPS promotes the aggregation of goethite NPs only when the pH (pH = 6) is less than the point of zero charge for the goethite nanoparticles (pHpzc ≈ 8). In the presence of ionic strength, the aggregation rate of goethite NPs increases with increasing concentration of NaCl, NaNO3 and Na2SO4 solutions, and after the addition of EPS solution, the critical coagulation concentrations (CCC) of goethite NPs are increased from 43.0, 56.7 and 0.39 mM to 168.0, 304.9 and 126.2 mM in the three electrolyte solutions, indicating that the addition of EPS inhibits the aggregation of goethite NPs. While in Na3PO4 solution, when the concentration of Na3PO4 solution ranged from 0 to 1 mM, the aggregation rate of goethite NPs increases first, followed by a decrease, and with the concentration of Na3PO4 solution exceeding 1 mM, the aggregation rate of goethite NPs increases again, due to the charge screening by sodium counter ions. This study provides a fundamental understanding of the behavior of goethite NPs in natural soil and water environments.

28555. 题目: Carbon-nitrogen removal in a structured-bed reactor (SBRRIA) treating sewage: Operating conditions and metabolic perspectives
文章编号: N18071814
期刊: Journal of Environmental Management
作者: Rafael B. Moura, Carla E.D. Santos, Dagoberto Y. Okada, Tiago H. Martins, Ant?nio Djalma N. Ferraz Júnior, Márcia H.R.Z. Damianovic, Eugenio Foresti
更新时间: 2018-07-18
摘要: The present study evaluated the efficiency of a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) to promote nitrogen and carbon removal from domestic sewage. The intermittent aeration and the recycling rate of 3 keeps the desired mixing degree inside the SBRRIA. Four different operational conditions were tested by varying the hydraulic retention time (HRT) from 12 to 8 h and aerated and non-aerated periods (A/NA) from 2 h/1 h and 3 h/1 h. At the THD of 8 h and A/NA of 2 h/1 h there was a decrease in the nitrification process (77.5%) due to the increase of organic matter availability, affecting the total-N removal performance. However, by increasing the aerated period from 2 h to 3 h, the nitrification efficiency rose to 91.1%, reaching a total-N removal efficiency of 79%. The system reached a maximum total-N loading removed of 0.117 kgN.m 3.d 1 by applying an HRT of 8 h and an intermittent aeration cycle of 3 h, aerated and 1 h non-aerated. The simultaneous nitrification and denitrification (SND) process was related to a complex interplay among microorganisms affiliated mostly to Acidovorax sp., Comamonas sp., Dechloromonas sp., Hydrogenophaga sp., Mycobacterium sp., Rhodobacter sp., and Steroidobacter sp.

28556. 题目: Dynamic contribution of microbial residues to soil organic matter accumulation influenced by maize straw mulching
文章编号: N18071813
期刊: Geoderma
作者: Xiao Liu, Feng Zhou, Guoqing Hu, Shuai Shao, Hongbo He, Wei Zhang, Xudong Zhang, Lijun Li
更新时间: 2018-07-18
摘要: Soil degradation is a serious problem in northeast China due to the routine removal of aboveground crop residues under conventional tillage systems; thus, crop residue retention becomes an essential approach for maintaining and improving soil organic matter (SOM) in this area. However, the impact of returning crop residue on microbial-driven SOM accumulation remains unclear. In this context, an 8-year field experiment with maize straw mulching (SM) was conducted in northeast China to evaluate how maize straw return may influence the dynamic contribution of microbial residues to SOM accumulation. Conventional cultivation was used as a control (CR), in which only 10 cm of aboveground maize biomass remained after the annual harvest. Soil samples (0–10 cm) were collected after the annual harvest for the measurement of soil organic carbon (SOC) and amino sugars (AS). Based on a first-order model, we found that soil microbial residue accumulation in this temperate arable soil might reach a steady state within decades under a specific agricultural management practice. Maize straw mulching both strengthened the retention ability of soil microbial residues and expanded their accumulation capacity. According to the glucosamine to muramic acid ratio, maize straw mulching facilitated the accumulation of fungal residues more than bacterial ones. Compared to maize residue removal, maize straw mulching accelerated the accumulation of microbial residues in SOM and enhanced the contribution of microbial residues to SOM sequestration in the surface soil, likely elucidating the pivotal mechanisms by which the “4/1000” initiative goal for agricultural soil will be met, at least for the first 10 years. Because bacterial residues are actively involved in SOM turnover while fungal residues dominantly contribute to SOM accrual enhanced by maize straw return compared to maize residue removal, we conclude that SOM in this arable field might be stabilized at a higher sequestration capacity under management with maize straw mulching.

28557. 题目: Carbon dynamics in surface and deep soil in response to increasing litter addition rates in an agro-ecosystem
文章编号: N18071812
期刊: Geoderma
作者: Tanvir Shahzad, Faiza Anwar, Sabir Hussain, Faisal Mahmood, Muhammad Saleem Arif, Amna Sahar, Muhammad Farrakh Nawaz, Nazia Perveen, Muhammad Sanaullah, Khadeeja Rehman, Muhammad Imtiaz Rashid
更新时间: 2018-07-18
摘要: Increasing atmospheric CO2 concentration and nitrogen deposition are predicted to increase fresh carbon (C) inputs in soils because of higher net primary productivity. However, relationship between soil C cycling and increased inputs of fresh C in soils is not clear. Moreover, most of the studies on soil organic carbon (SOC) focus on upper 20 cm although >50% SOC is present below this depth. We designed this study to unravel the response of SOC to 0% (control), 0.3%, 0.6%, 1.2% and 2.4% addition of maize litter (C4) to a surface (0–15 cm) and deep layers (55–75 cm) of a C3 soil. The isotopic difference between the maize litter and soil allowed distinguishing soil-derived (native) CO2-C from litter-derived CO2-C and calculating the priming effect (PE). Total respiration was measured over 78 d incubation whereas the PE was determined 39 d and 78 d after incubation. Our results showed that all the litter addition levels induced PE -stimulation of mineralization of the extant SOC in response to availability of fresh organic matter (FOM)- in surface and deep soil layers. Moreover, the PE was significantly higher in the deep than surface soil layer in response to all litter additions, except 2.4% treatment during the 2nd harvest. This result suggests that the deep SOC would mineralize at higher rates under similar supply of FOM to surface and deep soils in this agroecosystem. We also showed a significantly positive linear relationship between PE and litter addition rates for both soils implying continuous loss of SOC under increasing organic matter inputs. In conclusion, our study reveals that the deep soil C would be more vulnerable to priming effect in response to litter addition than the surface soil.

28558. 题目: Influencing factors on the removal of pharmaceuticals from water with micro-grain activated carbon
文章编号: N18071811
期刊: Water Research
作者: Thiago Caique Alves, Alba Cabrera-Codony, Damià Barceló, Sara Rodriguez-Mozaz, Adilson Pinheiro, Rafael Gonzalez-Olmos
更新时间: 2018-07-18
摘要: The removal efficiency of 6 micro-grain AC (μGAC) was examined for 23 selected pharmaceutical compounds, usually found at trace level in municipal wastewater treatment plant (WWTP) effluents. Two different sets of experiments were carried out using distilled water and a real WWTP secondary effluent in order to understand the adsorption mechanisms of pharmaceuticals, including the role of the presence of background organic matter. Physical and chemical properties of μGACs and target pollutants were checked for their potential to predict the pharmaceutical removal. Textural properties of μGACs, and especially the mesopore volume, seemed to play the most important role during the adsorption without background organic matter whereas the chemistry of the μGACs, such as the presence of surface oxygen groups and the point of zero charge, could have more influence in the experiments with WWTP effluent water. Positively charged molecules are better adsorbed due to the influence of the background organic matter and the presence of oxygenated groups in the surface of the μGACs. The UV254 removal correlated well with the pharmaceutical removal and it is confirmed as an indicator to control the performance of pharmaceuticals adsorption with μGACs in tertiary treatment.

28559. 题目: A horizontal permeable reactive barrier stimulates nitrate removal and shifts microbial ecology during rapid infiltration for managed recharge
文章编号: N18071810
期刊: Water Research
作者: Sarah Beganskas, Galen Gorski, Tess Weathers, Andrew T. Fisher, Calla Schmidt, Chad Saltikov, Kaitlyn Redford, Brendon Stoneburner, Ryan Harmon, Walker Weir
更新时间: 2018-07-18
摘要: We present results from field experiments linking hydrology, geochemistry, and microbiology during infiltration at a field site that is used for managed aquifer recharge (MAR). These experiments measured how a horizontal permeable reactive barrier (PRB) made of woodchips impacted subsurface nitrate removal and microbial ecology. Concentrations of dissolved organic carbon consistently increased in infiltrating water below the PRB, but not in un-amended native soil. The average nitrate removal rate in soils below the PRB was 1.5 g/m2/day NO3-N, despite rapid infiltration (up to 1.9 m/d) and a short fluid residence time within the woodchips (≤6 h). In contrast, 0.09 g/m2/day NO3-N was removed on average in native soil. Residual nitrate in infiltrating water below the PRB was enriched in δ15N and δ18O, with low and variable isotopic enrichment factors that are consistent with denitrification during rapid infiltration. Many putative denitrifying bacteria were significantly enhanced in the soil below a PRB; Methylotenera mobilis and genera Microbacterium, Polaromonas, and Novosphingobium had log2 fold-changes of +4.9, +5.6, +7.2, and +11.8, respectively. These bacteria were present before infiltration and were not enhanced in native soil. It appears that the woodchip PRB contributed to favorable conditions in the underlying soil for enhanced nitrate removal, quantitatively shifting soil microbial ecology. These results suggest that using a horizontal PRB could improve water quality during rapid infiltration for MAR.

28560. 题目: Cytostatic drug removal using electrochemical oxidation with BDD electrode: Degradation pathway and toxicity
文章编号: N18071809
期刊: Water Research
作者: Ewa Maria Siedlecka, Aleksandra Ofiarska, Agnieszka Fiszka Borzyszkowska, Anna Bia?k-Bielińska, Piotr Stepnowski, Aleksandra Pieczyńska
更新时间: 2018-07-18
摘要: In the presented study, electrochemical oxidation of five anticancer drugs (5-fluorouracil (5-FU), ifosfamide (IF), cyclophosphamide (CF), methotrexate (MTX), imatinib (IMB)) using boron doped diamond (BDD) electrode was investigated. In the first step the operating parameters of electrolysis were optimized. Studies have demonstrated a significant influence of applying current density, temperature, pH of solution and initial concentration of 5-FU on the process efficiency. A comparison of the decomposition rate of all the tested drugs showed a decrease in the pseudo-first order rate constants in the following order: k(IMB) > k(MTX) > k(CF) ≈ k(IF) > k(5-FU). Mineralization current efficiency (MCE) was determined for all the drugs based on the removal amount of total organic carbon (TOC) and their values decreased in the same order as values of drug degradation rate k. Based on the identified degradation products, electrochemical oxidation pathways of the decomposed drugs were proposed. In the case of CF, IF and 5-FU the degradation process occurred mainly through ketonization, hydroxylation and dehalogenation, while MTX and IMB were decomposed by attack of hydroxyl radicals on benzyl position in parent compounds. An important part of the research was the evaluation of eco-toxicity of electrochemically treated drug solutions against Lemna minor. Toxicity of initial 5-FU and MTX solutions towards L. minor were observed but after electrochemical treatment its toxicity decreased. The opposite trend was observed for CF and IF. In this case no significant toxicity was observed for the initial solutions of these drugs, while after electrochemical treatment an increase in growth inhibition of L. minor was found.