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17521. 题目: Elevated carbon dioxide and temperature imparted intrinsic drought tolerance in aerobic rice system through enhanced exopolysaccharide production and rhizospheric activation
文章编号: N18091410
期刊: Agriculture, Ecosystems & Environment
作者: S.R. Padhy, S. Nayak, P.K. Dash, M. Das, K.S. Roy, A.K. Nayak, S. Neogi, P. Bhattacharyya
更新时间: 2018-09-14
摘要: Elevation in atmospheric carbon dioxide (CO2) concentration and temperature coupled with moisture stress is anticipated by most of the climate change prediction models (IPCC, 2014). Climate change results in atmospheric warming that trigger water stress to rice and could influence soil health, functioning and biological activities. Therefore, it is required to quantify indicative parameters like soil-exopolysaccharides which indicates greater water holding capacity of soil and imparted drought tolerance to rice. Carbon pools and related soil enzymes are also indicative of soil health status. We designed one field study in open top chambers (OTCs) to assess the impact of elevated CO2, temperature and deficit moisture stress on rice. There were two replicated CO2 enrichment treatment in OTCs, namely, ambient CO2 (394 ± 20 ppm and ambient temperature; a-CO2) and elevated CO2 (550 ± 20 ppm) with temperature (2 °C ± 0.3 more than ambient; e-CO2T). Three aerobic rice (grown in saturated soil moisture condition) cultivars (CR-143-2-2, APO and CR Dhan 201) were grown in separate blocks in each OTCs with adequate nutrient level and water stress (−40 kPa). Total soil and colloidal exopolysaccharides (EPSs), soil labile carbon (C) pools, soil enzymes (dehydrogenase, Fluorescein diacetate and β-glucosidase) and plant enzymes (catalase, peroxidase and super oxide dismutase) were measured as indicators of the soil health, functioning and intrinsic drought tolerance to the system. Total soil EPS (29%), colloidal EPS (37%), microbial biomass C (30%), readily mineralizable C (29%), dehydrogenase (15%), FDA (38%), and β-glucosidase (13%) activities were significantly higher under elevated CO2 and temperature (e-CO2T) to that of ambient condition (a-CO2). The total and colloidal EPS, soil labile C pools and soil enzymatic activities were found higher at panicle initiation (PI) and grain filling (GF) stage than other physiological growth stages of rice. On the other hand, plant stress enzymes like catalase, peroxidise and superoxide dismutase (SOD) were decreased under e-CO2T by 24, 20 and 32%, respectively, as compared to a-CO2. All these indicated e-CO2T could impart additional intrinsic drought tolerance to tropical aerobic rice system (aerobic rice cultivars grown with adequate nutrient supply) in future climate change scenario.
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17522. 题目: High-resolution reconstruction of historical flood events in the Changjiang River catchment based on geochemical and biomarker records
文章编号: N18091409
期刊: Chemical Geology
作者: Rui Zhang, Tiegang Li, James Russell, Yurou Zhou, Fan Zhang, Zhiyong Liu, Minglei Guan, Qi Han
更新时间: 2018-09-14
摘要: Extreme hydrologic events such as floods have caused catastrophic losses to modern human society, especially in highly developed coastal areas. However, high-resolution reconstructions of extreme flood events are scarce due to a paucity of suitable proxies in marginal seas. Here we present a high-resolution record of extreme flood events in the Changjiang River catchment during the last 110 years using samples from the subaqueous delta of Changjiang River estuary. We used a multi-proxy approach including Sr-Nd isotopes, Zr/Rb ratio and biomarkers (branched GDGTs, i.e. brGDGTs, and crenarchaeol, and the ratio of the two as calculated by the BIT index) as proxies for the evolution of extreme floods in the Changjiang River catchment. Rapid shifts in these proxies agreed with the timing of floods on the Changjiang River. We also tested the reliability of biomarker indices to reconstruct paleoflood events in this area. The results indicated that the abundances of GDGTs fluctuated in concert with historical floods. Cross-spectral analyses revealed that historical floods in the Changjiang River catchment were consistent with ENSO variance.

17523. 题目: Calcite precipitation induced by Bacillus cereus MRR2 cultured at different Ca2+ concentrations: Further insights into biotic and abiotic calcite
文章编号: N18091408
期刊: Chemical Geology
作者: Dingxiang Zhuang, Huaxiao Yan, Maurice E. Tucker, Hui Zhao, Zuozhen Han, Yanhong Zhao, Bin Sun, Dan Li, Juntong Pan, Yanyang Zhao, Ruirui Meng, Guanghe Shan, Xinkang Zhang, Rongzhen Tang
更新时间: 2018-09-14
摘要: A key problem of how to distinguish between biotic and abiotic carbonate minerals in nature and/or in the laboratory has confused researchers for some time. Although numerous studies have been performed to explore the formation mechanism and the unique characteristics of biotic minerals, the issue needs to be studied further. Here, biotic calcite precipitation was induced by the microorganism Bacillus cereus MRR2 (GenBank KY810857), while organogenic and inorganogenic calcite was investigated in parallel. The results indicate that carbonic anhydrase (CA, a common enzyme of bacteria) promoted carbon dioxide hydration to release HCO3 and CO32− in the process of calcite precipitation; the pH increased from 7.2 to 8.9 as a result of the combination effect of the released ammonia by B. cereus MRR2 and the HCO3 and CO32− ions originating from the CA reaction. Glutamic acid is the most abundant amino acid in the extracellular polymeric substances of the bacteria, and its free carboxyl ions with a large number of negative charges in the alkaline environment facilitated the adsorption of calcium ions. The biotic calcite has a series of unique characteristics different from the organogenic and inorganogenic calcites, such as particular morphologies, P element composition and a variety of organic functional groups. Intracellular amorphous nanospheres without any crystal structure are also recorded. Stable carbon isotope analyses show that the biotic calcite (−20.9‰) has more negative δ13C values than the organogenic calcite (−15.6‰) and inorganogenic calcite (−11.7‰), indicating that microbial activity strongly affected the carbon isotope composition of biotic calcite. More importantly, the crystallinity and activation energy of the biotic calcite are clearly higher than those of organogenic calcite, suggesting that the thermal stability of biotic calcite is much higher. Thus, this study provides important insights into understanding the mechanisms of microbial biomineralization and the processes of biotic calcite formation, especially the roles microbes played in mineral nucleation and growth, as well as the unique characteristics of the resulting minerals. This study may provide useful evidence for further recognizing biotic and abiotic calcite in the geological record.
图文摘要:

17524. 题目: Advanced biofilm staining techniques for TEM and SEM in geomicrobiology: Implications for visualizing EPS architecture, mineral nucleation, and microfossil generation
文章编号: N18091407
期刊: Chemical Geology
作者: Jenine McCutcheon, Gordon Southam
更新时间: 2018-09-14
摘要: Microbial biofilms and mats have long been studied for their role in mineral precipitation reactions in natural environments. Scanning electron microscopy (SEM) is often used to characterize biofilms and their associated precipitates, however, conventional SEM sample preparation methods do not typically preserve the structure of the extracellular polymeric substances (EPS), which account for a large portion of biofilm material and play critical roles in biofilm function and mineral nucleation. In the present investigation, three biofilm fixation and staining protocols were test with regards to their ability to preserve, and aiding the visualization of, EPS using transmission electron microscopy (TEM). Although these protocols were initially developed for preserving complex tissue samples of eukaryotic organisms, the heterogeneous, three-dimensional nature of the biofilms make them suitable candidates for these sample processing methods. The results suggest that cryofixation provides the best preservation of cyanobacteria-dominated biofilm structures. A staining protocol including six different pre-embedding stains allowed for TEM visualization of the EPS matrix that encompasses biofilm cells and precipitate. Of the stains used, uranyl acetate appears to be critical in avoiding biofilm deformation during sample processing. Using these staining protocols, cell-EPS-mineral relationships were observed, including the precipitation of hydromagnesite [Mg5(CO3)4(OH)2·4H2O] on the EPS adjacent to the cyanobacteria cell exterior. Beachrock-associated biofilms were characterized using both TEM of ultrathin sections, as well as SEM of resin embedded osmium stained biofilms prepared as petrographic thin sections. Combining these two approaches enabled characterization of both the micrometer-scale cell-carbonate mineral contacts, as well as the larger scale microbial colony-mineral cement relationships. These results suggest that sample preparation techniques developed for rapid preservation of eukaryotic tissue samples can be used to preserve and characterize biofilm architecture. These findings have applications to understanding mineral nucleation in biofilms, and the preservation of biofilms as microfossils in the rock record.
图文摘要:

17525. 题目: Biochar does not attenuate triclosan's impact on soil bacterial communities
文章编号: N18091406
期刊: Chemosphere
作者: Vienvilay Phandanouvong-Lozano, Wen Sun, Jennie M. Sanders, Anthony G. Hay
更新时间: 2018-09-14
摘要: Triclosan, a broad-spectrum antimicrobial, has been widely used in pharmaceutical and personal care products. It undergoes limited degradation during wastewater treatment and is present in biosolids, most of which are land applied in the United States. This study assessed the impact of triclosan (0–100 mg kg−1) with and without biochar on soil bacterial communities. Very little 14C-triclosan was mineralized to 14CO2 (<7%) over the course of the study (42 days). While biochar (1%) significantly lowered mineralization of triclosan, analysis of 16S rRNA gene sequences revealed that biochar impacted very few OTUs and did not alter the overall structure of the community. Triclosan, on the other hand, significantly affected bacterial diversity and community structure (alpha diversity, ANOVA, p < 0.001; beta diversity, AMOVA, p < 0.01). Dirichlet multinomial mixtures (DMM) modeling and complete linkage clustering (CLC) revealed a dose-dependent impact of triclosan. Non-Parametric Metastats (NPM) analysis showed that 150 of 734 OTUs from seven main phyla were significantly impacted by triclosan (adjusted p < 0.05). Genera harboring opportunistic pathogens such as Flavobacterium were enriched in the presence of triclosan, as was Stenotrophomonas. The latter has previously been implicated in triclosan degradation via stable isotope probing. Surprisingly, Sphingomonads, which include well-characterized triclosan degraders were negatively impacted by even low doses of triclosan. Analyses of published genomes showed that triclosan resistance determinants were rare in Sphingomonads which may explain why they were negatively impacted by triclosan in our soil.

17526. 题目: Coupling continuous sand filtration to ultrafiltration for drinking water treatment: Improved performance and membrane fouling control
文章编号: N18091405
期刊: Journal of Membrane Science
作者: Yuanqing Guo, Langming Bai, Xiaobin Tang, Qiaojin Huang, Binghan Xie, Tianyu Wang, Jinlong Wang, Guibai Li, Heng Liang
更新时间: 2018-09-14
摘要: In order to alleviate the membrane fouling, a short flow drinking water process coupled the continuous sand filtration (CSF) to ultrafiltration (UF) was developed to treat the micro-polluted surface water and the membrane fouling mechanism was further discussed. The results indicated that the CSF process significantly enhanced the removal of ammonia (NH4+-N), accounting to an average removal of more than 70%. Furthermore, the natural organic matters (NOM) were also efficiently removed, with CODMn, UV254 and DOC reduced by approximately 30%, 17% and 18%, respectively. After 2 months of operation, the biological activity developed gradually within the CSF, which sparked an efficient removal performance of Fe and Mn. Besides, three dimensional fluorescence parallel factor analysis (PARAFAC) was employed to trace and characterize membrane fouling and a significantly positive correlation between the fluorescent foulants and irreversible fouling was observed. In addition, further simulations indicated that cake layer formation should be responsible for the trans-membrane pressure (TMP) increase. In order to gain a deep insight to the membrane fouling, the composition of foulants in the chemical backwash water was characterized, and humic substances and metal ions (i.e. Fe, Mn, Ca and Mg) were the main components, which demonstrated that the irreversible membrane fouling should be related to the synergistic effects of inorganic ion precipitates and humic substances. Overall, coupling CSF to UF filtration can significantly enhance its removal performance and control the membrane fouling, which is expected to be a promising alternative based on the principle of aquatic ecosystems for the micro-polluted raw water.
图文摘要:

17527. 题目: Influences of isolated fractions of natural organic matter on adsorption of Cu(II) by titanate nanotubes
文章编号: N18091404
期刊: Science of The Total Environment
作者: Tong Zheng, Ting Wang, Ruoqi Ma, Wen Liu, Feng Cui, Weiliang Sun
更新时间: 2018-09-14
摘要: With different functional groups and hydrophobic/hydrophilic properties, natural organic matters (NOMs) displayed different combining capacities with metal ions. By using XAD-4 and DAX-8 resins, NOMs in natural lake were isolated into three fractions, i.e., HoB (hydrophobic base), HoA (hydrophobic acid) and HiM (hydrophilic matter). Afterwards, influences on Cu(II) adsorption onto titanate nanotubes (TNTs) were compared with varying NOMs and initial pH. As results, HoB can significantly control Cu(II) adsorption at pH 5, with the adsorption capacity increased 15% for 0.5 mg L−1 of HoB (ca. 120 mg g−1), which could be attributed to the formation of HoB-Cu complexation and electrostatic bridge effect of HoB with optimal concentration. Due to the easier ionization and complexation with Cu(II) at lower pH, HoA showed more obvious impaction on Cu(II) adsorption at pH 2. While HiM can influence Cu(II) adsorption at all pH ranges due to its hydrophilic groups and weak affinity to both TNTs and Cu(II). Furthermore, HoB dramatically changed the Langmuir model, with sharp increase of adsorption capacity as equilibrium Cu(II) increased, suggesting its significant involvement in Cu(II) adsorption. X-ray photoelectron spectroscopy (XPS) analysis revealed the absorbed Cu(II) existed in the form of TNTs‑OCu, TNTs‑COOCu and Cu(OH)2, proving Cu(II) adsorption mechanism including both direct adsorption by TNTs and bridging connection with NOMs. Moreover, the CO and OCO groups content ranked as HiM > HoB > HoA, while TNTs‑COOCu content ranked as HoA > HoB > HiM, suggesting HoB had the moderate connection with both TNTs and Cu(II), thus the impact on Cu(II) adsorption was remarkable.
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17528. 题目: Projections of water, carbon, and nitrogen dynamics under future climate change in an alpine tundra ecosystem in the southern Rocky Mountains using a biogeochemical model
文章编号: N18091403
期刊: Science of The Total Environment
作者: Zheng Dong, Charles T. Driscoll, John L. Campbell, Afshin Pourmokhtarian, Anne M.K. Stoner, Katharine Hayhoe
更新时间: 2018-09-14
摘要: Using statistically downscaled future climate scenarios and a version of the biogeochemical model (PnET-BGC) that was modified for use in the alpine tundra, we investigated changes in water, carbon, and nitrogen dynamics under the Representative Concentration Pathways at Niwot Ridge in Colorado, USA. Our simulations indicate that future hydrology will become more water-limited over the short-term due to the temperature-induced increases in leaf conductance, but remains energy-limited over the longer term because of anticipated future decreases in leaf area and increases in annual precipitation. The seasonal distribution of the water supply will become decoupled from energy inputs due to advanced snowmelt, causing soil moisture stress to plants during the growing season. Decreases in summer soil moisture are projected to not only affect leaf production, but also reduce decomposition of soil organic matter in summer despite increasing temperature. Advanced future snowmelt in spring and increasing rain to snow ratio in fall are projected to increase soil moisture and decomposition of soil organic matter. The extended growing season is projected to increase carbon sequestration by 2% under the high radiative forcing scenario, despite a 31% reduction in leaf display due to the soil moisture stress. Our analyses demonstrate that future nitrogen uptake by alpine plants is regulated by nitrogen supply from mineralization, but plant nitrogen demand may also affect plant uptake under the warmer scenario. PnET-BGC simulations also suggest that potential CO2 effects on alpine plants are projected to cause larger increases in plant carbon storage than leaf and root production.
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17529. 题目: Removal of inert COD and trace metals from stabilized landfill leachate by granular activated carbon (GAC) adsorption
文章编号: N18091402
期刊: Journal of Environmental Management
作者: Ehsan Mohammad-pajooh, Ariel E. Turcios, Graham Cuff, Dirk Weichgrebe, Karl-Heinz Rosenwinkel, M.D. Vedenyapina, L.R. Sharifullina
更新时间: 2018-09-14
摘要: Landfills in Germany are currently approaching stabilization phase; as a result removal of inert organics and potentially toxic elements in the leachate is becoming a primary concern. Dissolved air floatation (DAF) at the secondary stage reduces only 27% of the residual chemical oxygen demand (COD) in the investigated treatment systems; downstream granular activated carbon (GAC) units are required to further reduce COD concentration by 40–56% to meet indirect discharge or direct discharge limits respectively. Therefore, in this study performance in terms of COD and trace metals adsorption of different types of granular activated carbon were compared over different contact times and dosages. GAC 1 with Brunauer-Emmett-Teller (BET) surface area of 719.5 ± 2.1 m2/g and average pore diameter (D) of 4.81 nm was identified to be inappropriate for treatment of leachate from this landfill. GAC 2 (with BET of 1513.7 ± 6.4 m2/g and D of 3.50 nm) was feasible for COD reduction from DAF-pretreated leachate, while GAC 3 (with BET of 644.5 ± 2.6 m2/g and D of 5.65 nm) can be coupled either with biological step alone, or as a tertiary step after the DAF unit. Moreover, as COD is the primary remaining contaminant of interest after secondary and tertiary treatment, spectrometer probes provide a close estimation of COD concentration for use in online monitoring. Beside COD removal, GAC 3 also confirmed the effectiveness of trace metals adsorption even at trace level, as it removed 66, 64, 48, 47, 43, and 25% of copper, cobalt, chromium, manganese, nickel, and zinc, respectively.
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17530. 题目: Mechanisms for increasing soil resistance to acidification by long-term manure application
文章编号: N18091401
期刊: Soil and Tillage Research
作者: Ren-yong Shi, Zhao-dong Liu, Yu Li, Taiming Jiang, Minggang Xu, Jiu-yu Li, Ren-kou Xu
更新时间: 2018-09-14
摘要: Soil pH buffering capacity (pHBC) plays a crucial role in determining soil acidification rates and the amount of lime required to ameliorate soil acidity. However, it remains poorly understood how soil organic matter affects soil pHBC. Here, Alfisol and Ultisol samples from long-term fertilization experiments (control, chemical N, P, and K (NPK), manure only (M), 1/2 NPK plus 1/2 M (1/2NPKM), and NPK plus M (NPKM)) were used to investigate the effects and underlying mechanisms of manure application on the pHBC and soil resistance to acidification through simulated acidification experiments. The results indicated that the application of manure increased pHBC and the resistance of soils to acidification in both the Alfisol and Ultisol. The pHBC of the Alfisol in the M and NPKM treatments was increased by 81 and 60% compared with the control, respectively. Similarly, the pHBC of the Ultisol in the NPKM treatment was 66% higher than that of the control. The extent of protons consumption by the Alfisol followed the order: M > NPKM > 1/2NPKM > NPK ≈ control during stimulated acidification, which was consistent with their pHBC. These results suggested that manure application increased the resistance of the Alfisol to acidification by increasing soil pHBC. The protonation of organic anions from the dissociation of weakly acidic functional groups on soil organic matter to form neutral molecules was the main mechanism responsible for the increase in pHBC and soil resistance to acidification induced by manure application. During this process, some exchangebale base cations were released from negatively charged sites on organic matter into soil solution. This mechanism was confirmed by the experimental observations: the release of base cations from soils increased, while soil exchangeable base cations and effective CEC decreased as soil pH decreased. The results are of fundamental significance for understanding the role of organic matter in retarding soil acidification through long-term manure application.
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17531. 题目: Rapid quantification of humic components in concentrated humate fertilizer solutions by FTIR spectroscopy
文章编号: N18091315
期刊: Journal of Soils and Sediments
作者: Evgeniya Karpukhina, Ivan Mikheev, Irina Perminova, Dmitry Volkov, Mikhail Proskurnin
更新时间: 2018-09-13
摘要: Purpose: The use of humic substances is under thorough discussion of state-of-the-art agricultural science. They are marketed mostly as concentrated aqueous solutions of potassium or sodium humates, which are produced by alkali extraction of raw organic matter such as lignite, leonardite, or peat. Due to the presence of clay minerals in the raw materials, humate solutions are characterized with a substantial content of silicates. At the same time, rapid quantification techniques for selective determination of humic components and silicates in humate solutions are missing. The aim of this work was to develop an IR spectroscopic technique for rapid quantification of humic substances (HSs) and silicates in concentrated humate solutions with the minimum sample preparation, which could be used for quality control of humic fertilizers. Materials and methods: Sodium humate from Sigma-Aldrich and two potassium humate fertilizers available on the market were used for the experiments. For FTIR measurements, thin-layer open-cell (DialPath) transmission and attenuated total reflectance (ATR) accessories were used. The secondary focus of this work was the use of a compact portable IR spectrometer, which can be used in the field. Total carbon analyzer and ICP-AES for determination of silicon and aluminum contents were used. Results and discussion: FTIR spectra were registered for both dry samples and aqueous solutions of the humates. The most intense bands in IR spectra of HS were characterized with linear concentration dependences in the range of concentrations of 2–200 g L−1 of HS. The most sensitive band was shown to be 1560 cm−1. It corresponded to carboxyl groups (COO) of humates (limits of detection [recalculated to carbon] for transmission and ATR modes are 3 and 1 g L−1, respectively). The band at 1015 cm−1 was attributed to silicate. It did not overlap with the bands of organic constituents and could be used for silicate quantification. The proposed technique can identify different trademarks of the fertilizers by the amount of both HS and silicate. Conclusions: Rapid determination of humate and silicate components comprising three samples of humic fertilizers was proposed without isolation of the analytes from solution.

17532. 题目: Formation characteristics of carbonaceous and nitrogenous disinfection by-products depending on residual organic compounds by CGS and DAF
文章编号: N18091314
期刊: Environmental Science and Pollution Research
作者: Minsoo Maeng, Nirmal Kumar Shahi, Gwyam Shin, Heejong Son, Dongheui Kwak, Seok Dockko
更新时间: 2018-09-13
摘要: Allogenic organic matter (AOM) composed of extracellular and intracellular organic matter (EOM and IOM) is a major precursor of halogenated carbonaceous and nitrogenous disinfection by-products (C-DBPs and N-DBPs) upon chlorination. The EOM and IOM extracted from Microcystis aeruginosa were analyzed based on bulk parameters and organic fractions with different molecular weight by liquid chromatography with organic carbon detection (LC-OCD). It investigated the efficiency of a conventional gravity system (CGS) and dissolved air flotation (DAF) in the removal of organic precursors, together with measurement of the formation of four major trihalomethanes (THMs) and haloacetonitriles (HANs) in treated water upon chlorination. The results showed that EOM accounted for 59% of building blocks and humic substances, whereas for IOM, 54% were low molecular weight (LMW) neutrals. Both CGS and DAF showed 57–59% removal of dissolved organic carbon (DOC) from EOM and IOM. Regarding DON removal, DAF was found to be more effective, i.e., 8% higher than CGS for EOM. Moreover, the removal of LMW acids and neutrals (not easy to remove and are major precursors of DBPs) from EOM and IOM by DAF was higher than from CGS. The amounts of DBPs measured in all the samples treated for interchlorination were much lower than in the samples for prechlorination. Although the precursors of EOM had a higher concentration than in IOM, THMs and HANs were detected for IOM at a higher concentration, which might be attributed to higher amounts of aromatic, aliphatic moisture and protein compounds in the IOM. Comparatively, DAF showed lower THM and HAN values than CGS water, particularly for IOM. Also, DAF showed a sharp decrease in THMs and an insignificant increase in HANs according to time.

17533. 题目: Seasonal effect of land use type on soil absolute and specific enzyme activities in a Brazilian semi-arid region
文章编号: N18091313
期刊: CATENA
作者: Érica de Oliveira Silva, Erika Valente de Medeiros, Gustavo Pereira Duda, Mario Andrade Lira Junior, Michel Brossard, Julyana Braga de Oliveira, Uemeson José dos Santos, Claude Hammecker
更新时间: 2018-09-13
摘要: Tropical environments are considerable contributors to overall soil carbon loss to the atmosphere. Land use effects on soil chemical attributes have been well documented mainly in humid environments; however, less attention has been paid to the changes in soil enzymatic activities in dry ecosystems that is a sensitive indicator in ecological processes, due to its importance in soil dynamics and microbial activity. The present study is part of interdisciplinary project that investigated the effect of land cover type and seasonal variation on absolute and specific enzymatic activities per unit of soil organic carbon (SOC) and per microbial biomass carbon (MBC). We assessed five different land use type (Tropical dry forest-TDF, protected area with Angico –ANA, protected area with Ipê-TAB, Scrub area-SCR and agricultural area with maize-M) and five areas of each land use in three layers: 0–0.05, 0.05–0.10 and 0.10–0.20 m. The samples were collected at rainy season 1 in April 2014 (RS1), dry season October 2015 (DS) and rainy season 1 April 2016 (RS2). The conversion of the preserved area provided a reduction in absolute enzymatic activities, especially in the SCR and M. The reductions were of 76% for β-glucosidase, 95% for urease and 72% for acid phosphatase. The specific enzymatic activities per unit of MBC increased with the change of soil use, except in M. The enzymatic activity per unit of SOC in the TDF area was higher in relation to the other areas evaluated, except for specific activity of acid phosphatase. The land use type influenced the absolute and specific soil enzyme activities, but not show a clear trend of seasonal effect.

17534. 题目: Using Chromate to Investigate the Impact of Mineral-Organic Contact Time on the Surface Reactivity of Goethite
文章编号: N18091312
期刊: Environmental Science: Processes Impacts
作者: Stacey Nicole Hales-Messenger, Andrew Swindle
更新时间: 2018-09-13
摘要: Chromate was used as a chemical probe to investigate the impact of mineral-organic contact time on the surface reactivity of two different sizes of goethite particles. A series of goethite-chromate sorption batch reactions were conducted in the presence and absence of Suwannee River humic acid (HA) and natural organic matter (NOM) using nano- and micro-scale goethite particles. In experiments with added organics the amount of time allowed for goethite-organic matter interaction (i.e. contact time) was varied from less than 1 minute, up to 24 hours prior to the addition of chromate. Results indicated that nano- and micro-scale goethite in the absence of organics sorbed nearly identical amounts of chromate on a per mass basis, despite the greater surface area of the smaller particles. Results also indicated that the presence of ~10 mg/L of HA and a contact time of less than 1 minute reduced the amount of chromate sorbed by both nano- and micro-scale goethite. Increasing the contact time resulted in greater decreases in chromate sorption. Experiments using NOM produced similar results. While chromate sorption was most rapid during the first hour of the experiments, goethite particles continued to sorb additional chromate over a period of up to 7 days. Additionally, a noticeable impact in chromate sorption due to increased contact time was present over that time period.

17535. 题目: National soil organic carbon estimates can improve global estimates
文章编号: N18091311
期刊: Geoderma
作者: U.W.A. Vitharana, Umakant Mishra, R.B. Mapa
更新时间: 2018-09-13
摘要: Global inventories of spatial and vertical distribution of soil organic carbon (SOC) stocks are being used in national and global initiatives targeted to mitigate climate change and land degradation impacts. Yet, national level high-resolution estimates of SOC stocks can be useful for improving the accuracy of global SOC inventories. We estimated spatially resolved SOC stocks of surface 0–30 cm and subsurface 30–100 cm layers at a spatial resolution of 30 m in tropical Island, Sri Lanka using a legacy harmonized soil database of 122 soil profiles. The national estimates were compared with two global estimates derived from WISE30sec and SoilGrids250m. The tropical Island (land area = 64,610 km2) occupying 0.03% of global land area showed a considerable heterogeneity in SOC stocks ranging from 2.0–342.5 Mg ha−1 and 2.7–391.7 Mg ha−1 in the surface and subsurface soil layers, respectively. We found, elevation, precipitation and slope angle as main environmental controllers of the spatial distribution of SOC stocks under tropical climate. Incorporating the pedogenic information (derived from soil series level legacy map, soil orders and suborders) with environmental controllers resulted in better regression models of predicting surface (R2 = 0.61) and subsurface (R2 = 0.81) SOC stocks. Geographically weighted regression kriging derived maps of SOC stocks revealed that 0–100 cm soil layer of the tropical Island stored 500 Tg C contributing for 0.04% of the global SOC stocks. The validation results of our estimates showed low Mean Estimation Error (MEE: surface −1.6 and subsurface −1.6 Mg ha−1) and Root Mean Square Error (RMSE: surface 29.5 and subsurface 24.9 Mg ha−1) indicating a low bias and satisfactory predictions. The relative improvement of the prediction accuracy of the SOC stocks of our geospatial estimates in the 0–30 cm layer in comparison to SoilGrids250m and WISE30sec data derived SOC stocks were 51.7% and 35.2%, respectively. The SOC stocks predictions of the 30–100 cm soil layer showed even better relative improvement compared to SoilGrids250m (78.4%) and WISE30sec (57.4%) SOC estimates. Compared to estimates of total SOC stocks resulted in this study, WISE30sec data derived SOC stock maps showed 30% over estimation of the C stock in surface 0–30 cm (332 Tg C) and 41% overestimation in 30–100 cm layer (343 Tg C). The over estimation of total SOC stocks by the SoilGrids250 SOC stocks map for the surface 0–30 cm layer was 122% (567 Tg C) and for the 30–100 cm layer it was 209% (750 Tg C). We conclude that the fusion of legacy soil information of SOC stocks with appropriate environmental covariates and pedogenic information derived from legacy area-class soil maps at national level can produce more accurate inventories of spatial and vertical distribution of SOC stocks. These national inventories have a great potential of upgrading global inventories of SOC stocks.

17536. 题目: Dynamics of soil respiration and microbial communities: Interactive controls of temperature and substrate quality
文章编号: N18091310
期刊: Soil Biology and Biochemistry
作者: Rana Shahbaz Ali, Christian Poll, Ellen Kandeler
更新时间: 2018-09-13
摘要: Soil microbial communities mediate soil feedbacks to climate; a thorough understanding of their response to increasing temperatures is therefore central to predict climate-induced changes in carbon (C) fluxes. However, it is unclear how microbial communities will change in structure and function in response to temperature change and to the availability of organic C which varies in complexity. Here we present results from a laboratory incubation study in which soil microbial communities were exposed to different temperatures and organic C complexity. Soil samples were collected from two land-use types differing in climatic and edaphic conditions and located in two regions in southwest Germany. Soils amended with cellobiose (CB), xylan, or coniferyl alcohol (CA, lignin precursor) were incubated at 5, 15 or 25 °C. We found that temperature predominantly controlled microbial respiration rates. Increasing temperature stimulated cumulative respiration rates but decreased total microbial biomass (total phospholipid fatty acids, PLFAs) in all substrate amendments. Temperature increase affected fungal biomass more adversely than bacterial biomass and the temperature response of fungal biomass (fungal PLFAs, ergosterol and ITS fragment) depended upon substrate quality. With the addition of CB, temperature response of fungal biomass did not differ from un-amended control soils, whereas addition of xylan and CA shifted the fungal temperature optima from 5 °C to 15 °C. These results provide first evidence that fungi which decompose complex C substrates (CA and xylan) may have different life strategies and temperature optima than fungal communities which decompose labile C substrate (CB). Gram-positive and gram-negative bacteria differed strongly in their capacity to decompose CB under different temperature regimes: gram-positive bacteria had highest PLFA abundance at 5 °C, while gram-negative bacteria were most abundant at 25 °C. Bacterial community composition, as measured by 16S rRNA gene abundance, and PLFAs showed opposite temperature and substrate decomposition trends. Using multivariate statistics, we found a general association of microbial life strategies and key members of the microbial community: oligotrophic Alphaproteobacteria and Acidobacteria were associated with complex substrates and copiotrophic Actinobacteria with labile substrates. Our study provides evidence that the response of C cycling to warming will be mediated by shifts in the structure and function of soil microbial communities.

17537. 题目: Soil carbon and nitrogen accumulation following agricultural abandonment in a subtropical karst region
文章编号: N18091309
期刊: Applied Soil Ecology
作者: Peilei Hu, Shujuan Liu, Yingying Ye, Wei Zhang, Xunyang He, Yirong Su, Kelin Wang
更新时间: 2018-09-13
摘要: Vegetation restoration following agricultural abandonment is an effective method for soil organic carbon (SOC) sequestration. However, SOC dynamics during post-agriculture succession in different soil layers, and its regulation by soil nitrogen (N), are not well understood. We investigated SOC and soil N dynamics during post-agriculture succession at soil depths of 0–10, 10–20, 20–30, and 30–50 cm in a subtropical karst area in southwest China. The succession sequence included grassland (∼9 years), shrubland (∼25 years), secondary forest (∼52 years), and primary forest, with cropland as a reference. In the 0–50 cm soil profile, the SOC and soil N stocks will recover to the primary forest level in ∼74 years at a rate of 112.35 g C m−2 yr−1 and in ∼100 years at a rate of 12.07 g N m−2 yr−1, respectively. The accumulation rate of SOC and soil N was higher in the topsoil (0–20 cm) than in the subsoil (20–50 cm). The estimated time for SOC stock to recover to the primary forest level in topsoil and subsoil was similar (72 and 76 years, respectively), whereas that for soil N stock require more time in topsoil than in subsoil (106 and 89 years, respectively). The higher rate of relative N stock change than that of SOC suggests that progressive N limitation does not occur in the long term following agricultural abandonment. Our results highlight the importance of soil depth and soil N in determining SOC change for secondary succession. Furthermore, the results suggest that, compared to that of previous studies, which considered only surface soil in the karst regions of southwest China, the recovery period of C and N in soil profile may be longer than that assumed previously.

17538. 题目: Effect of aging in field soil on biochar's properties and its sorption capacity
文章编号: N18091308
期刊: Environmental Pollution
作者: Xinhao Ren, Hongwen Sun, Fei Wang, Peng Zhang, Hongkai Zhu
更新时间: 2018-09-13
摘要: Due to its high sorption capacity for different kinds of contaminants, biochar is advocated as a novel remediation strategy for contaminated soils. However, it is not clear how long this extraordinary sorption capacity will be maintained after the biochar is applied to the soil. In this study, a commercial biochar was applied to an agricultural soil, and the sorption of atrazine and phenanthrene on biochar amended soils with different aging periods ranging from 0 to 2 y was investigated. The application of fresh biochar in soil led to an obvious enhancement of the sorption coefficients (Kd) of atrazine and phenanthrene (by 3.13 and 2.93 times at Ce = 0.01 Sw, respectively) compared with the untreated soil. The surface area of biochar first increased and then decreased with aging time. Correspondingly, the sorption of atrazine and phenanthrene on the biochar amended soils first increased and then decreased markedly. Based on the changing trend of the Kd values with aging time, it could be predicted that the sorption capacity of biochar amended soils will decrease to the level of the untreated soil after 2.5 y.
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17539. 题目: Rice root exudates affect microbial methylmercury production in paddy soils
文章编号: N18091307
期刊: Environmental Pollution
作者: Jia-Yin Zhao, Zhi-Hong Ye, Huan Zhong
更新时间: 2018-09-13
摘要: Microbial methylmercury (MeHg) production in contaminated soil-rice systems and its accumulation in rice pose health risks to consumers, especially those in Asia. However, the mechanism responsible for microbial MeHg production in paddy soils is far from clear. While previous studies examined the effect of soil and microbial factors on soil MeHg levels, in this work we explored the impact of rice cultivation itself on microbial MeHg production, focusing on the root exudate organic matter as a potential source of electron donors for microbial methylators. Effects of the cultivation of two rice cultivars, Heigu246 (H-rice) and Neiwuyou8015 (N-rice), on MeHg production in soils were therefore investigated in pot and batch incubation experiments. Soil MeHg levels measured in H-rice treatment during the heading and harvest stages were 18–49% higher than in the control and 23–108% higher than in N-rice treatment. Consequently, MeHg levels in grain, straw, and root were 38%, 81%, and 40% higher in H-rice than those in N-rice, which was mainly attributed to cultivar-specific MeHg production in soils. Results of the batch experiments suggested that root exudate organic matter could be responsible for MeHg production in soils during rice cultivation, by increasing the abundances of potential microbial methylators. For instance, root exudate organic matter increased copy numbers of Hg methylation genes (hgcA) in soils 4.1-fold. Furthermore, the 211% higher concentration of acetate (a key electron donor for microbial methylators) in the root exudate of H-rice could account for the higher MeHg production under H-rice than N-rice cultivation. Our results suggest that root exudate organic matter, especially acetate, as its key component, contributes to the elevated soil MeHg concentrations during rice cultivation. The proposed mechanism provides new insights into the elevated risk of MeHg production in contaminated soil-rice systems, as well as cultivar-specific MeHg bioaccumulation.
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17540. 题目: Dynamic variations in dissolved organic matter and the precursors of disinfection by-products leached from biochars: Leaching experiments simulating intermittent rain events
文章编号: N18091306
期刊: Environmental Pollution
作者: Mi-Hee Lee, Yong Sik Ok, Jin Hur
更新时间: 2018-09-13
摘要: Biochar-leached dissolved organic matter may have a substantial impact on the water quality of receiving water surrounded by biochar-amended fields. In this study, we tracked variations in the spectroscopic characteristics and the disinfection by-products formation potentials of dissolved organic matter (DOM) leached during sequential extraction for three different biochars (BCs), which simulates DOM from BC-amended fields during intermittent rain events. The optical properties of DOM were more dependent on the BC types with different origins (sludge, corn, and rice) rather than on the extraction time. A large amount of DOM was released during the initial period of the extraction (1 day), which was equivalent to 52–60% of the total cumulative organic carbon during 17 days of extraction. The relative contribution of the initial extraction to the total cumulative amounts was greater for the formation potential of trihalomethanes (THMs) per BC (71–82%) compared to those of haloacetic acids (HAAs) or dissolved organic carbon (DOC), suggesting that the leaching behaviors of disinfection byproducts (DBP) precursors from BCs may be different from those of DOC (i.e., bulk DOM). Among the three BCs, corn BC-derived DOM exhibited the highest formation potentials of THMs and HAAs per BC for both the initial and the total cumulative extraction. The specific (or DOC-normalized) THMs formation potential was positively correlated with the ratios of terrestrial humic-like to fulvic-like components, implying condensed aromatic structures could operate as a surrogate for THMs formation of BC-derived DOM. This study provided insight into dynamic leaching behaviors of DOM from BCs and the formation potentials for THMs and HAAs in BC-amended fields under intermittent rainfall.
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