论文检索

总访问量：5737697次

总访客量：393279人

所有论文

25141. 题目: Biochar counteracts nitrification inhibitor DMPP–mediated negative effect on spinach (Spinacia oleracea L.) growth
文章编号: N20012912
期刊: Ecotoxicology and Environmental Safety
作者: Jamal Sheikhi, Hossein Mirsyed Hosseini, Hassan Etesami, Aziz Majidi
更新时间: 2020-01-29
摘要: The use of nitrification inhibitors (NIs) such as 3,4–dimethylpyrazole phosphate (DMPP) has been suggested to diminish agricultural soil nitrate (NO₃⁻) loss and increase nitrogen (N) use efficiency (NUE). However, the yield of ammonium (NH₄⁺)–sensitive plants such as spinach (Spinacia oleracea L.) may be adversely affected by the application of NIs at high N levels and, on the other hand, the efficiency of the NIs may also be affected by soil amendments such as biochar. These two issues are still not adequately addressed. The aim of this study was to evaluate the effect of different N levels including DMPP or not in a calcareous soil with and without amendment of wheat straw biochar on spinach yield, NUE, nitrate concentration of spinach leaf, activity of enzymes nitrate reductase (NR) and nitrite reductase (NiR), and soil ammonium (NH₄⁺) and NO₃⁻ concentration under greenhouse conditions. This experiment was carried out with different N rates factor at seven levels (un–fertilized, N0; fertilized with 50 mg N kg⁻¹ soil, N50; fertilized with 75 mg N kg⁻¹ soil, N75; fertilized with 100 mg N kg⁻¹ soil, N100; fertilized with N50 + DMPP; fertilized with N75 + DMPP; and fertilized with N100 + DMPP) and biochar (BC) factor at two levels (0, 0%BC; and 2% (w/w), 2%BC) with six replications over a 56–day cultivation period of spinach. Results showed that the application of DMPP had no significant effect on the yield of spinach plant at low and medium levels of N (50 and 75 mg N kg⁻¹ soil), but decreased the yield of this plant at the higher level of N (100 mg N kg⁻¹ soil). However, application of BC decreased the negative effect of DMPP on spinach yield as the yield in spinach plants fertilized with N75 + DMPP and N100 + DMPP significantly increased. Both application of DMPP and addition of BC to soil decreased leaf NO₃⁻ concentration by 29.2% and 16.3% compared to control, respectively. Biochar compared to control decreased NR activity by 46.3%. With increasing N rate, NR and NiR activities increased, but DMPP decreased the activities of both enzymes. Biochar reduced the efficiency of DMPP as soil NH₄⁺ concentration was higher in the treatments containing DMPP without BC at 56 days after planting. Biochar and DMPP could increase the quality of spinach plant through decreasing the leaf NO₃⁻ concentration. In general, wheat straw biochar counteracted DMPP–mediated negative effect on growth of spinach plant at high level of N by decreasing the efficiency of this inhibitor. These results provide the useful information for managing the application rate of N fertilizers including DMPP in biochar–amended soil.

25142. 题目: Release and stability of water dispersible biochar colloids in aquatic environments: Effects of pyrolysis temperature, particle size, and solution chemistry
文章编号: N20012911
期刊: Environmental Pollution
作者: Jing Fang, Leilei Cheng, Rashida Hameed, Liang Jin, Dengjun Wang, Gary Owens, Daohui Lin
更新时间: 2020-01-29
摘要: Pathways for the physical disintegration of biochar (BC) and the release of water dispersible BC colloids (WDBC) have received much attention due to their unique impacts on carbon loss and contaminant. However, the current understanding of the mechanisms involved in WDBC formation and associated influencing factors is rather limited. This study systematically explored the effects of pyrolysis temperature, initial particle size, and solution chemistry on WDBC formation in aqueous solutions and examined the formation and colloidal stability of WDBC in natural solutions. Results showed that pyrolysis temperature determined the abrasion resistance of pyrolyzed BC, and the submicron fragment rate decreased in the order 400 °C (BC400) > 700 °C (BC700) > 200 °C (BC200). The WDBC yield decreased in the order BC400 (77.5–331 mg g⁻¹) > BC700 (33.5–173 mg g⁻¹) > BC200 (16.8–125 mg g⁻¹) depending on BC size at a solution ionic strength (IS) ≤ 1 mM, which was positively correlated with the submicron fragment rate of bulk BC. With the exception of BC200, increasing IS (0.1–20 mM) and decreasing pH (3.0–10.0) significantly inhibited WDBC yield. Release and sedimentation dominated the WDBC formation processes with the former being more susceptible to solution chemistry. Derjaguin-Landau-Verwey-Overbeek interactions properly explained the effect of IS on WDBC from BC400 and BC700, while the steric resistance of abundant dissolved organic carbon on BC200 was mainly responsible for the high formation of WDBC at high IS (20–50 mM). WDBC had high colloidal stability and could form and stabilize well in natural surface waters and soil solutions, suggesting the relevant risk of long-distance migration of WDBC in environments. These findings represent new knowledge regarding the physical decomposition and the fate of BC in the environment.
图文摘要:

25143. 题目: Chronic nitrogen addition promotes dissolved organic carbon accumulation in a temperate freshwater wetland
文章编号: N20012910
期刊: Environmental Pollution
作者: Rong Mao, Xin-Hou Zhang, Chang-Chun Song
更新时间: 2020-01-29
摘要: Temperate wetlands have been undergoing increased nitrogen (N) inputs in the past decades, yet its influence on dissolved organic carbon (DOC) dynamics is still elusive in these ecosystems. Here, using a field multi-level N addition (0, 6, 12, and 24 g N m⁻² year⁻¹) experiment, we investigated the changes in aboveground plant biomass, DOC production from plant litters, DOC biodegradation, and DOC concentration in surface water and soil pore water (0–15 cm depth) following 10 years of N addition in a freshwater marsh of Northeast China. We observed that, irrespective of N addition levels, N addition caused an increase in DOC production from plant litters under both non-flooded and flooded conditions. Conversely, DOC biodegradation was inhibited by N addition in both surface water and soil pore water. Because of enhanced DOC production from plant litters and declined DOC biodegradation, N addition elevated DOC concentration in surface water and soil pore water across the growing season. In addition, long-term N addition increased aboveground plant biomass, but decreased species richness. Our results suggest that long-term N enrichment promotes DOC accumulation through the contrasting effects on litter-derived DOC production and microbial decomposition of DOC in temperate wetlands.
图文摘要:

25144. 题目: Effects of acid, acid-ZVI/PMS, Fe(II)/PMS and ZVI/PMS conditioning on the wastewater activated sludge (WAS) dewaterability and extracellular polymeric substances (EPS)
文章编号: N20012909
期刊: Journal of Environmental Sciences
作者: Xiaoyang Fan, Yili Wang, Daxin Zhang, Yajie Guo, Shihui Gao, Enrui Li, Huaili Zheng
更新时间: 2020-01-29
摘要: The effects of four conditioning approaches: Acid, Acid-zero-valent iron (ZVI)/peroxydisulfate (PMS), Fe(II)/PMS and ZVI/PMS, on wastewater activated sludge (WAS) dewatering and organics distribution in supernatant and extracellular polymeric substances (EPS) layers were investigated. The highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS, and the optimum conditions were pH 3, ZVI dosage 0.15 g/g dry solid (DS), oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time (CST) and water content (Wc) as 19.67% and 8.49%, respectively. Four conditioning approaches could result in TOC increase in EPS layers and supernatant, and protein (PN) content in tightly bound EPS (TB-EPS). After conditioning, organics in EPS layers could migrate to supernatant. Polysaccharide (PS) was easier to migrate to supernatant than PN. In addition, Acid, Acid-ZVI/PMS or Fe(II)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v PO, v C-O-C, v C-O-P functional groups from TB-EPS. ESR spectra proved that both radicals of SO₄^-· and ·OH contributed to dewatering and organics transformation and migration. CST value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS, while it negatively correlated with TOC, PN content and PS content in TB-EPS, as well as PS content in supernatant and LB-EPS. BWC negatively correlated to zeta potential and TOC value, PN content, and HA content in supernatant.
图文摘要:

25145. 题目: The contribution of prokaryotes and terrestrial plants to Maldives inter-atoll sapropels: evidence from organic biomarkers
文章编号: N20012908
期刊: Organic Geochemistry
作者: Masatoshi Nakakuni, Keiko Takehara, Peter K. Swart, Shuichi Yamamoto
更新时间: 2020-01-29
摘要: The composition of organic matter in early Miocene sediment cores obtained from International Ocean Discovery Program Expedition 359 (IODP Exp. 359) was analysed using tetramethylammonium hydroxide (TMAH) thermochemolysis, a method used to determine concentrations of lignin phenols, fatty acids, sterols and hopanols. These early Miocene sediment cores contain thick sequences (∼100 m) of interbedded light (organic-poor) and dark (organic-rich) sedimentary layers. A total of 49 samples from cores between 704.4 mbsf to 803.95 mbsf (∼20–23 Ma) at Site U1466 (518 m water depth) was selected with particular emphasis placed on the dark layers, although the light layers were also sampled. While organic compounds were below detection limits in the lighter coloured sedimentary layers, the dark layers, with concentrations of organic carbon up to 20%, contained varying concentrations of all analysed compounds. Although sterols were present, hopanoids were more abundant in the dark layers. The contribution of prokaryotic organisms, estimated by (hopanols/[sterols + hopanols]), indicates that it was prokaryotic organisms rather than eukaryotic organisms that contributed the majority (∼90%) of the organic matter in the dark layers. In conjunction with this record, more negative δ¹⁵N values in the darker layers suggest that the prokaryotic organisms were nitrogen-fixing microorganisms (presumably cyanobacteria). The long-to-short fatty acid ratios, together with sterol distributions and the concentration of lignin phenols, suggest the input of terrestrial plant material occurred during a high total organic carbon (TOC) interval (∼770–810 mbsf), which coincides with more negative carbon isotope ratios. Additionally, the long-to-short fatty acid ratio in this interval was significantly higher in the dark layers than the light layers, suggesting that in terrestrial environments suitable for vegetation growth expanded during the interval represented by the dark layers. Furthermore, the ratio of cinnamyl lignin phenols to vanillyl lignin phenols (C/V) is relatively high during this interval. From these tracers, it is possible to speculate that the terrestrial vegetation was dominated by herbaceous plants adapted to frequent sea-level changes.

25146. 题目: Impact of living mulch on soil C:N:P stoichiometry in orchards across China: A meta-analysis examining climatic, edaphic, and biotic dependency
文章编号: N20012907
期刊: Pedosphere
作者: Guo CHEN, Shibin LIU, Yangzhou XIANG, Xiaolu TANG, Haitao LIU, Bin YAO, Xuqiang LUO
更新时间: 2020-01-29
摘要: The use of living mulch in orchards is a widely accepted management strategy for improving soil quality and enhancing tree productivity. Although the effects of living mulch on soil organic carbon (C) and nutrients have been previously investigated, changes in the stoichiometric ratios of C, soil total nitrogen (N), and soil total phosphorous (P) under different climatic, edaphic, and biotic conditions are currently unknown. These factors are important indicators of elemental balance associated with ecological interactions. In order to examine the effects of living mulch in orchards on soil C:N:P stoichiometry under different conditions, a meta-analysis was undertaken. The results showed that in general, living mulch significantly (P < 0.05) increased C:P and N:P ratio, while the impact on C:N ratio was not significant, a result that was related to the coupled increase of C and N. Phosphorous limitation occurred shortly after the addition of living mulch; after four years this effect receded. In contrast, an increase in C occurred simultaneously with N increase at all stages. Specifically, the treatment effect was context-dependent. The living mulch did not change soil stoichiometry in orchards with old trees (> 10 years), an occurrence which may be related to changes in the amount of fungi. Grass life history also had a significant influence on the treatment effect on soil stoichiometry, while N-fixing characteristics did not. The treatment effect was significant in areas with moderate mean annual temperature and mean annual precipitation, which might be related to the litter ratio of grass and trees. Effects on stoichiometric ratios were significant in the top soil layer (0–20 cm), in contrast to the deep soil layers. Therefore, grass species and management practices, such as fertilization, should be selected according to the specific soil and climatic conditions of the management area.

25147. 题目: Are humic substances soil microbial residues or unique synthesized compounds? A perspective on their distinctiveness
文章编号: N20012906
期刊: Pedosphere
作者: Sen DOU, Jun SHAN, Xiangyun SONG, Rui CAO, Meng WU, Chenglin LI, Song GUAN
更新时间: 2020-01-29
摘要: Humic substances (HS), which are defined as a series of highly acidic, relatively high-molecular-weight, and yellow to black colored substances formed during the decay and transformation of plant and microbial remains, ubiquitously occur in nature. Humic substances represent the largest stable organic carbon pool in terrestrial environments and are the central characteristic of the soil. However, the validity of the HS concept and the justification of their extraction procedure have been recently debated. Here, we argue that the traditional humic paradigm is still relevant. Humic substances are distinctive and complex because the extracted HS formed during the humification are chemically distinct from their precursors and are heterogeneous among soils. By reviewing the concept, formation pathways, and stabilization of HS, we propose that the key question facing soil scientists is whether HS are soil microbial residues or unique synthesized compounds. Without revealing the distinctiveness of HS, it is impossible to address this question, as the structure, composition, and reactivity of HS are still poorly known owing to the heterogeneity and geographical variability of HS and the limits of the currently available analytical techniques. In our view, the distinctiveness of HS is fundamental to the soil, and thus further studies should be focused on revealing the distinctiveness of HS and explaining why HS hold this distinctiveness.

25148. 题目: Responses of soil microbial communities and functions associated with organic carbon mineralization to nitrogen addition in a Tibetan grassland
文章编号: N20012905
期刊: Pedosphere
作者: Ruyi LUO, Jiafa LUO, Jianling FAN, Deyan LIU, Jin-Sheng HE, Nazia PERVEEN, Weixin DING
更新时间: 2020-01-29
摘要: Alpine grasslands with a high soil organic carbon (SOC) storage on the Tibetan Plateau are experiencing rapid climate warming and anthropogenic nitrogen (N) deposition; this is expected to substantially increase the soil N availability, which may impact carbon (C) cycling. However, little is known regarding how N enrichment influences soil microbial communities and functions relative to C cycling in this region. We conducted a 4-year field experiment on an alpine grassland to evaluate the effects of four different rates of N addition (0, 25, 50, and 100 kg N ha⁻¹ year⁻¹) on the abundance and community structure (phospholipid fatty acids, PLFAs) of microbes, enzyme activities, and community level physiological profiles (CLPP) in soil. We found that N addition increased the microbial biomass C (MBC) and N (MBN), along with an increased abundance of bacterial PLFAs, especially Gram-negative bacterial PLFAs, with a decreasing ratio of Gram-positive to Gram-negative bacteria. The N addition also stimulated the growth of fungi, especially arbuscular mycorrhizal fungi, reducing the ratio of fungi to bacteria. Microbial functional diversity and activity of enzymes involved in C cycling (β-1,4-glucosidase and phenol oxidase) and N cycling (β-1,4-N-acetyl-glucosaminidase and leucine aminopeptidase) increased after N addition, resulting in a loss of SOC. A meta-analysis showed that the soil C/N ratio was a key factor in the response of oxidase activity to N amendment, suggesting that the responses of soil microbial functions, which are linked to C turnover relative to N input, primarily depended upon the soil C/N ratio. Overall, our findings highlight that N addition has a positive influence on microbial communities and their associated functions, which may reduce soil C storage in alpine grasslands under global change scenarios.

25149. 题目: Humic acid modified nano-ferrous sulfide enhances the removal efficiency of Cr(VI)
文章编号: N20012904
期刊: Separation and Purification Technology
作者: Youru Yao, Na Mi, Cheng He, Huan He, Yong Zhang, Yongcai Zhang, Li Yin, Jing Li, Shaogui Yang, Shiyin Li, Lixiao Ni
更新时间: 2020-01-29
摘要: The dissolved hexavalent chromium (Cr(VI)) in natural water system poses a significant risk for public health and the environment. Nanoscale ferrous sulfide (FeS) has been widely used to treat soils, sediments, groundwater, and natural waters contaminated with Cr(VI), but the reactivity of FeS can be significantly reduced due to its easy agglomeration and therefore decreased the remove rate of the dissolved Cr(VI). To overcome this problem, the present study used humic acid (HA) to modify FeS in order to reduce its agglomeration and increase stability. Results showed that the HA modified FeS (HA-FeS) had good stability and reduced FeS agglomeration. The hydrodynamic diameter of HA-FeS was between 235 and 241 nm, which was much smaller than that of the unmodified FeS. The maximum removal quantity of Cr(VI) by HA-FeS was 7.74 and 2.35 times higher that of HA and the unmodified FeS, respectively, and the maximum removal quantity of HA-FeS was 675.03 mg/g. Further, HA-FeS performed better efficiency in removing the dissolved Cr(VI) with high or low concentration. With an increasing concentration of Ca²⁺ and Mg²⁺, the efficiency of HA-FeS to remove Cr(VI) showed a decreasing trend. The removal mechanism of Cr(VI) mainly relies on the reducibility of Fe²⁺ and S^2-. XPS and XRD measurements further revealed that 95.03% of Cr(VI) was converted to Cr(III) (FeCr₂O₄, Cr(OH)₃ and Cr₂O₃), and another 4.58% of Cr(VI) was adsorbed by HA-FeS. Therefore, this study demonstrated an efficient method to improve the nano-FeS stability and reactivity for the rapid repair of Cr(VI) contamination in natural water.
图文摘要:

25150. 题目: Short-term casting activity of earthworm Pontoscolex corethrurus (Oligochaeta: Glossoscolecidae) after biochar additions
文章编号: N20012903
期刊: Soil Biology and Biochemistry
作者: Solomon Kamau, Edmundo Barrios, Nancy K. Karanja, Fredrick O. Ayuke, Johannes Lehmann
更新时间: 2020-01-29
摘要: Conversion of forests to cultivated farms through slash-and-burn or chop-and-char practices often results in rapid loss of soil organic matter (SOM) or conversion of inherent SOM into pyrogenic organic matter (PyOM). However, there is little knowledge about the short-term changes in soil macrofauna that may occur when large amount of biochar are added to the soil. A thirty-day microcosm study was conducted to assess effects of biochar derived from two trees, Croton megalocarpus Hutch. and Zanthoxylum gilletii (De Wild.) P.G.Waterman, on the activity of a geophagous earthworm, Pontoscolex corethrurus. A portion of the biochar was leached with either acetone or 2 M HCl, to remove easily mineralizable organic matter and ash contents, respectively. Each of the biochar types was mixed with soil at a rate equivalent to 5, 10 and 25 Mg ha⁻¹. Casts were collected after 30 days and used as a measure of earthworms’ activity. Casts dry weight was affected more by amount than the type of biochar. The highest cast weight (188.1 g and 176.5 g) was recorded in microcosm that received 5 Mg ha⁻¹ of C. megalocarpus and Z. gilletii biochar, respectively. Notably, the weight decreased with increasing biochar additions. Cast weight decreased by 4% in microcosms that received 10 Mg of C. megalocarpus biochar ha⁻¹ and by 15% in microcosms that received the same biochar type at a rate of 25 Mg ha⁻¹. Similarly, there was a 6% decline in cast weight in microcosms that received 10 Mg of Z. gilletii biochar ha⁻¹ and an 8% decline in microcosms amended with 25 Mg ha⁻¹ of the same biochar type. Easily mineralizable organic matter or nutrients were not responsible for the observed differences in cast production since leaching with acetone or HCl did not change the effects. The C and N in casts and bulk soil were not significantly different, an indication that earthworms did not seek out biochar, but rather indiscriminately utilised the soil rich in biochar.

25151. 题目: Release of phosphorus and silicon from minerals by soil microorganisms depends on the availability of organic carbon
文章编号: N20012902
期刊: Soil Biology and Biochemistry
作者: Emanuel Brucker, Sarmite Kernchen, Marie Spohn
更新时间: 2020-01-29
摘要: Microorganisms release nutrients from minerals. However, this process is not yet well understood despite its importance for soil fertility. The aim of this study was to determine which factors control microbial phosphorus (P) and silicon (Si) release from apatite and weathered rock, and to analyze which microbial-mediated processes cause P and Si solubilization. For this purpose, we conducted a series of incubation experiments with apatite and saprolite (weathered bedrock) and soil extracts of four soils that are located along a climate gradient in the Coastal Cordillera of Chile and differ in soil P fractions and degree of weathering. We developed an approach that allowed us to measure the release of P from apatite and the release of Si from saprolite by microbial consortia in soil solution. The microbial consortia of all soil extracts caused release of P from apatite. The addition of carbon (C) and nitrogen (N) to the soil solution increased the rate of microbial P solubilization from apatite by a factor of about 10 in all soil depth increments. The pH decreased strongly during the incubations. In the depth increments 0.1–0.2 and 0.4–0.6 m, the P solubilization rates were negatively correlated with the pH measured at the end of the incubation (r² = 0.55 and 0.76, respectively, both p < 0.01). Nine organic acids were detected throughout the experiment. The total concentration of carboxyl groups was positively correlated with the P solubilization rate (r² = 0.94, p < 0.01). The addition of dissolved inorganic P to the soil extracts did not significantly decrease the P solubilization rates. The rate of microbial Si solubilization from saprolite increased strongly with the surface area of the saprolite. We conclude that microbial solubilization of P from apatite was limited by the availability of easily decomposable C and that microbial solubilization of P from apatite was not affected by P availability, indicating that this process is not or not exclusively controlled by microbial need for P. In conclusion, our results indicate that microbial weathering of bedrock is strongly constrained by the availability of organic C and by the specific surface area of the saprolite.

25152. 题目: A meta-analysis of global cropland soil carbon changes due to cover cropping
文章编号: N20012901
期刊: Soil Biology and Biochemistry
作者: Jinshi Jian, Xuan Du, Mark S. Reiter, Ryan D. Stewart
更新时间: 2020-01-29
摘要: Including cover crops within agricultural rotations may increase soil organic carbon (SOC). However, contradictory findings generated by on-site experiments make it necessary to perform a comprehensive assessment of interactions between cover crops, environmental and management factors, and changes in SOC. In this study, we collected data from studies that compared agricultural production with and without cover crops, and then analyzed those data using meta-analysis and regression. Our results showed that including cover crops into rotations significantly increased SOC, with an overall mean change of 15.5% (95% confidence interval of 13.8%–17.3%). Whereas medium-textured soils had highest SOC stocks (overall means of 39 Mg ha⁻¹ with and 37 Mg ha⁻¹ without cover crops), fine-textured soils showed the greatest increase in SOC after the inclusion of cover crops (mean change of 39.5%). Coarse-textured (11.4%) and medium-textured soils (10.3%) had comparatively smaller changes in SOC, while soils in temperate climates had greater changes (18.7%) than those in tropical climates (7.2%). Cover crop mixtures resulted in greater increases in SOC compared to mono-species cover crops, and using legumes caused greater SOC increases than grass species. Cover crop biomass positively affected SOC changes while carbon:nitrogen ratio of cover crop biomass was negatively correlated with SOC changes. Cover cropping was associated with significant SOC increases in shallow soils (≤30 cm), but not in subsurface soils (>30 cm). The regression analysis revealed that SOC changes from cover cropping correlated with improvements in soil quality, specifically decreased runoff and erosion and increased mineralizable carbon, mineralizable nitrogen, and soil nitrogen. Soil carbon change was also affected by annual temperature, number of years after start of cover crop usage, latitude, and initial SOC concentrations. Finally, the mean rate of carbon sequestration from cover cropping across all studies was 0.56 Mg ha⁻¹ yr⁻¹. If 15% of current global cropland were to adopt cover crops, this value would translate to 0.16 ± 0.06 Pg of carbon sequestered per year, which is ∼1–2% of current fossil fuels emissions. Altogether, these results indicated that the inclusion of cover crops into agricultural rotations can enhance soil carbon concentrations, improve many soil quality parameters, and serve as a potential sink for atmosphere CO₂.

25153. 题目: Earthquake slip surfaces identified by biomarker thermal maturity within the 2011 Tohoku-Oki earthquake fault zone
文章编号: N20012811
期刊: Nature Communications
作者: Hannah S Rabinowitz, Heather M Savage, Pratigya J Polissar, Christie D Rowe, James D Kirkpatrick
更新时间: 2020-01-28
摘要: Extreme slip at shallow depths on subduction zone faults is a primary contributor to tsunami generation by earthquakes. Improving earthquake and tsunami risk assessment requires understanding the material and structural conditions that favor earthquake propagation to the trench. We use new biomarker thermal maturity indicators to identify seismic faults in drill core recovered from the Japan Trench subduction zone, which hosted 50 m of shallow slip during the Mw9.1 2011 Tohoku-Oki earthquake. Our results show that multiple faults have hosted earthquakes with displacement ≥ 10 m, and each could have hosted many great earthquakes, illustrating an extensive history of great earthquake seismicity that caused large shallow slip. We find that lithologic contrasts in frictional properties do not necessarily determine the likelihood of large shallow slip or seismic hazard.

25154. 题目: CONTRASTING PATTERNS OF LABILE AND SEMI‐LABILE DISSOLVED ORGANIC CARBON FROM CONTINENTAL WATERS TO THE OPEN OCEAN
文章编号: N20012810
期刊: Journal of Geophysical Research: Biogeosciences
作者: R. LaBrie, J.‐F. Lapierre, R. Maranger
更新时间: 2020-01-28
摘要: Marine and freshwater prokaryotes feed primarily on bioavailable labile dissolved organic carbon (BDOC_L), as well as the bioavailable fraction of the semi‐labile DOC (BDOC_SL) pool. These fractions are operationally defined here as the DOC consumed within a month and greater than a month to a year and a half, respectively. Organic matter from these different pools comes from various autochthonous and allochthonous sources, but their relative bioavailability is unknown across aquatic ecosystems. To fill this gap, we compiled literature information that included 655 batch culture DOC biodegradation experiments across eight aquatic ecosystem types over the past 20 years. We show that the proportion of BDOC_L across all aquatic ecosystems was surprisingly consistent (6.1%) despite a two orders of magnitude variation in initial DOC concentrations, suggesting an overall tight balance between carbon supply and consumption. A higher proportion of BDOC_L, 16.3% on average, was observed in high productivity ecosystems. BDOC_SL, on the other hand, gradually decreased from 16.0% in lakes to 7.2% in estuaries to undetectable in the open ocean, suggesting that terrestrial connectivity regulates BDOC_SL across the continuum. Our results support that recent primary production fuels short‐term prokaryotic DOC needs with an increasing reliance on the abundant BDOC_SL pool as ecosystems approach the land–water interface. Batch culture experiments show that BDOC_SL is metabolizable in freshwater and coastal environments, but not in the open ocean. We estimate that BDOC_SL can sustain 62% of total prokaryotic biomass in inland waters and coasts, and an estimated total of 16.7% across aquatic biomes.

25155. 题目: Efficient Removal of Cr(VI) from Aqueous Solution by Fe-Mn Oxide-Modified Biochar
文章编号: N20012809
期刊: Water, Air, & Soil Pollution
作者: Yiyang Zhu, Wencan Dai, Kai Deng, Ting Pan, Zhijie Guan
更新时间: 2020-01-28
摘要: Removal of Cr(VI) is of great concern due to its high mobility and toxicity in the natural environment. In this study, Fe-Mn oxide-modified biochar composite (FMBC) was prepared by impregnation to remove Cr(VI) from aqueous systems. The effect of Fe/Mn ratio, adsorbent dosage, solution pH, initial Cr(VI) concentration, and temperature were investigated on the Cr(VI) removal efficiency. Results showed that F1M3BC (with an Fe/Mn ratio of 1:3) had the maximum Cr(VI) adsorption capacity of 118.03 mg g⁻¹ at pH 2.0. The removal efficiency of Cr(VI) by F1M3BC (91.79%) was higher than that by the pristine BC (32.17%). Experimental data fitted well with the Langmuir model and the pseudo-second-order kinetics equation. Thermodynamic studies showed that the adsorption process was endothermic and spontaneous. Multiple techniques including BET, SEM, FTIR, and XPS were used to analyze the possible adsorption mechanisms. It was found that the increased adsorption of Cr(VI) on F1M3BC, mainly occurred due to electrostatic attraction and Cr(VI) reduction, together with Cr(III) complexation. Furthermore, regeneration studies indicated that F1M3BC could be recycled for up to six cycles without loss of activity. Therefore, F1M3BC may be promising for environmental applications removing Cr(VI) from aqueous systems.

25156. 题目: Analysis of urban land cover influence to organic carbon and nutrients in surface water via impacted groundwater
文章编号: N20012808
期刊: Environmental Monitoring and Assessment
作者: Katarzyna Puczko, Elżbieta Jekatierynczuk-Rudczyk
更新时间: 2020-01-28
摘要: This paper presents an object-oriented approach for analysing and characterising the urban landscape structure and its influence on the quality of surface waters and shallow groundwater. We investigated springs, streams and ponds from an urban area. The land cover classification was adopted with the conceptual framework of urban land cover (HERCULES model). This study has demonstrated that water quality in the urban area is strongly related to land cover, and the degree of its transformation is not the same in all types of waters. The land with forests and shrubs does not have many extreme values in water chemical characteristics. Statistical analyses indicated that the main environmental factors influencing water chemistry are impermeable surfaces such as buildings. They are an essential element which deteriorates water quality. The patches with buildings and pavements were characterised by a wide gradient of nutrient concentration in rivers and ponds. Shallow groundwater had a limited effect on surface water quality.

25157. 题目: Emerging investigator series: Control of membrane fouling by dissolved algal organic matter using pre-oxidation with coagulation as seawater pretreatment
文章编号: N20012807
期刊: Environmental Science: Water Research & Technology
作者: Bhaskar Deka, Jiaxin Guo, Sanghyun Jeong, Manish Kumar, Alicia Kyoungjin An
更新时间: 2020-01-28
摘要: Marine algae produce organic matter, namely algal organic matter (AOM), especially during a harmful algal bloom. AOM has been recognised as a key cause for the formation of organic fouling on membranes in seawater desalination applcations. In this study, pre-oxidation of AOM by potassium permanganate (KMnO4) and sodium hypochlorite (NaOCl) was investigated. In addition, ferric (Fe3+) and alum (Al3+) coagulants were used for subseqent coagulation. Two different operational modes, conventional coagulation-flocculation-sedimentation (CFS) and coagulation-flocculation-dissolved air flotation (CF-DAF) processes, were used to evaluate pretreatment performance using synthetic AOM with an initial dissolved organic carbon (DOC) of around 4.8 mg C L-1 (turbidity ≈ 4.47 NTU, pH ≈ 8). Pre-oxidation with coagulation removed more AOM, compared to oxidation or coagulation alone. The removal of DOC by NaOCl-Fe3+ is relatively high when compared to other combinations of oxidant and coagulant because of in-situ ferrate (Fe6+) generation, which was detected by the ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid))-ultraviolet visible (UV-Vis) method. Pre-oxidation with 1.5 mg L-1 NaOCl followed by coagulation with 2.5-3.0 mg L-1 Fe3+ achieved a maximum DOC removal of 65-76% during the CFS treatment; while, the DOC removal could further increased up to 83-85% by introducing CF-DAF . Particularly, the NaOCl-Fe3+ treatment generated 1.31 mg L-1 of in-situ ferrate (Fe6+). Finally, pre-oxidation and coagulation coupled with DAF sucessfully reduced fouling and lowered flux decline in a microfiltration (MF) membrane. Non-invasive optical coherence tomography (OCT) was performed to monitor the fouling development on the MF membrane before and after pretreatment.

25158. 题目: New insights into filamentous sludge bulking: The potential role of extracellular polymeric substances in sludge bulking in the activated sludge process
文章编号: N20012806
期刊: Chemosphere
作者: Wei-Ming Li, Xi-Wen Liao, Jin-Song Guo, Yu-Xin Zhang, You-Peng Chen, Fang Fang, Peng Yan
更新时间: 2020-01-28
摘要: The control of filamentous sludge bulking has been regarded as an important issue in the activated sludge process due to there is still a lack of understanding of the bulking mechanisms. In this study, changes in the extracellular polymeric substances (EPS) and metabolic profile of bulking sludge based on the proteomics level was investigated to reveal the potential role of EPS in deteriorating sludge floc stability and structure during filamentous bulking. The results showed that the EPS content gradually decreased from 210.23 mg/g volatile suspended solids (VSS) to 131.34 mg/g VSS during sludge bulking. The protein (PN) content of the EPS significantly decreased from 173.33 mg/g VSS to 95.42 mg/g VSS during sludge bulking. However, a gradual increase in polysaccharides (PS) was observed. Bacterial aggregation was hindered by the changes in the EPS and its components. The excessive proliferation of filamentous bacteria had a significant effect on the molecular functions of the extracellular PN and metabolic pathways of the EPS. The proteins associated with the hydrophobic amino acid synthesis decreased, whereas the proteins associated with the hydrophilic amino acid synthesis increased during sludge bulking. Electric repulsion was the key factor affecting the aggregation and flocculation ability of the bacteria during sludge bulking. The changes in the EPS and its components induced by the excessive proliferation of filamentous bacteria resulted in a loose floc structure and poor settling performance during sludge bulking. These findings provide new insights into sludge bulking during the activated sludge process.
图文摘要:

25159. 题目: Molten salt induced nitrogen-doped biochar nanosheets as highly efficient peroxymonosulfate catalyst for organic pollutant degradation
文章编号: N20012805
期刊: Environmental Pollution
作者: Yi Xie, Wanrong Hu, Xuqian Wang, Wenhua Tong, Panyu Li, Hui Zhou, Yabo Wang, Yongkui Zhang
更新时间: 2020-01-28
摘要: Advanced oxidation processes based on carbon catalysis is a promising strategy possessing great potential for environmental pollution degradation. Herein, nitrogen-doped biochar nanosheets (NCS-x) were synthesized using a nitrogen-rich biomass (Candida utilis) as sole precursor. The involvement of environmental-friendly molten salt (NaCl and KCl) in pyrolysis process not only facilitated the exfoliation of biochar, but also favored the retention of N element in biochar. When applying as catalyst for peroxymonosulfate activation, the as-obtained NCS-6 exhibited outstanding performance in catalytic degradation of bisphenol A (BPA). A 100% removal efficiency was observed in 6 min with fast reaction kinetic (k = 1.36 min⁻¹). Based on quenching test and in-situ electron paramagnetic resonance analysis, both radical pathway and non-radical pathway were suggested to be involved in BPA degradation, while singlet oxygen was identified as the dominant reactive oxygen species. Furthermore, the ecotoxicity evaluation using Chlorella vulgaris as ecological indicator indicated that BPA solution after degradation was less toxic than the original solution. It is expected that this green and facile strategy holds great promise for value-added conversion of nitrogen-rich biomass to highly efficient biochar nanosheets for environment remediation.
图文摘要:

25160. 题目: NOM mitigates the phytotoxicity of AgNPs by regulating rice physiology, root cell wall components and root morphology
文章编号: N20012804
期刊: Environmental Pollution
作者: Xitong Huang, Yong Li, Ke Chen, Haiyan Chen, Fei Wang, Xiaomin Han, Beihai Zhou, Huilun Chen, Rongfang Yuan
更新时间: 2020-01-28
摘要: Natural organic matter (NOM) affects the environmental behaviors of AgNPs, which may change their phytotoxicity to plants. However, more evidence can be provided to illustrate how NOM influences AgNPs-induced phytotoxicity. In this study, using rice (Oryza sativa) as a model, the effects of NOM, Suwannee River humic acid (SRHA) and fulvic acid (FA), on the dissolution and phytotoxicity of AgNPs were investigated. Silver ions decreased in both AgNPs and AgNO₃ solution in the presence of NOM, and the effect of SRHA was stronger than FA. Image-XRF (iXRF) results showed that Ag mainly remained in the root rather than the shoot of rice seedling exposed to AgNPs. NOM mitigated the negative effects of AgNPs and AgNO₃ on rice with lower germination inhibition rate, less chlorophyll reduction, more relative biomass and less O₂^•− content. Moreover, NOM improved root cell viability according to FDA fluorescent dye as well as maintained the normal root morphology. Interestingly, the neutral sugars content from pectin, hemicellulose 1, hemicellulose 2 and cellulose of root cell wall in AgNPs and AgNO₃ treatments differed from the control, while it was close to the regular content in AgNPs/AgNO₃+SRHA/FA groups, which implied that NOM regulated the changes. Besides, SRHA led to less germination and less relative biomass than FA due to different chemical characters. Thus, NOM needs to be considered when studying the phytotoxicity of AgNPs.
图文摘要: