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25861. 题目: Characteristics of organic phosphorus fractions in soil from water-level fluctuation zone by solution ³¹P-nuclear magnetic resonance and enzymatic hydrolysis
文章编号: N19092805
期刊: Environmental Pollution
作者: Ying Qu, Chao Wang, Jinsong Guo, Junjie Huang, Fang Fang, Yan Xiao, Wenjuan Ouyang, Lunhui Lu
更新时间: 2019-09-28
摘要: Phosphorus (P) is an essential nutrient element for biological growth that can contribute to eutrophication in aquatic ecosystems. Water trophic status and algae growth are primarily related to the content of bioavailable P, which is primarily related to enzymatically hydrolysable organic P(EHOP) and dissolved inorganic P(IP). In this study, soil samples from the water-level fluctuation zone (WLFZ) were collected from a tributary of the Three Gorges Reservoir (TGR) to characterize the properties of organic P(OP) fractions using solution ³¹P-nuclear magnetic resonance (NMR) and enzymatic hydrolysis. ³¹P-NMR showed that orthophosphate was the main part of the bioavailable P in the WLFZ soil and accounted for 80.4% of the NaOH-EDTA extractable total P (NaOH-EDTA TP), while phosphate monoester accounted for 60.5% of NaOH-EDTA extractable OP (NaOH-EDTA OP). The soil properties and replenishment from the mainstream of the Yangtze River to the Pengxi River have a certain effect on the content and distribution of P forms in the WLFZ soil of the tributary. The EHOP accounted for 28.1% of the NaOH-EDTA OP, and a significant positive correlation was observed between labile monoester P and EHOP and organic matter (OM). The water-soluble OP(H₂O-OP), bicarbonate-extractable OP(NaHCO₃-OP), and Fe- and Al-associated OP(Fe/Al-OP) were significantly hydrolyzed by phosphatase and thus exhibited great release potential. The ranking of the bioavailability of OP was Fe/Al-OP > H₂O-OP > NaHCO₃-OP. Phytate-like P were mainly found in H₂O-OP and NaHCO₃-OP, which indicated that periodic submersion–emersion cycles promoted the release of phytate-like P from Fe/Al-OP into the water column of the TGR. These observations suggest that when the external P input was effectively controlled, a huge risk of release of the internal OP from the WLFZ soil, and the biogeochemical cycling of the bioavailable P played an important role in maintaining the eutrophication of the reservoir.
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25862. 题目: Formation of microbial products by activated sludge in the presence of a metabolic uncoupler o-chlorophenol in long-term operated sequencing batch reactors
文章编号: N19092804
期刊: Journal of Hazardous Materials
作者: Fang Fang, Su-Na Wang, Ke-Yan Li, Jin-Yun Dong, Run-Ze Xu, Lu-Lu Zhang, Wen-Ming Xie, Jia-Shun Cao
更新时间: 2019-09-28
摘要: Metabolic uncouplers are widely used for reducing excess sludge in biological wastewater treatment systems. However, the formation of microbial products, such as extracellular polymeric substances, polyhydroxyalkanoate and soluble microbial products by activated sludge in the presence of metabolic uncouplers remains unrevealed. In this study, the impacts of a metabolic uncoupler o-chlorophenol (oCP) on the reduction of activated sludge yield and formation of microbial products in laboratory-scale sequencing batch reactors (SBRs) were evaluated for a long-term operation. The results show the average reduction of sludge yield in the four reactors was 17.40%, 25.80%, 33.02% and 39.50%, respectively, when dosing 5, 10, 15, and 20 mg/L oCP. The oCP addition slightly reduced the pollutant removal efficiency and decreased the formation of soluble microbial products in the SBRs, but stimulated the productions of extracellular polymeric substances and polyhydroxyalkanoate in activated sludge. Furthermore, the significant reduction of electronic transport system activity occurred after the oCP addition. Microbial community analysis of the activated sludge indicates dosing oCP resulted in a decrease of sludge richness and diversity in the SBRs. Hopefully, this study would provide useful information for reducing sludge yield in biological wastewater treatment systems and behaviors of activated sludge in the presence of uncouplers.
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25863. 题目: Occurrence, migration, and allocation of arsenic in multiple media of a typical semi-enclosed bay
文章编号: N19092803
期刊: Journal of Hazardous Materials
作者: Xiang Gu, Wei Ouyang, Ling Xu, Mats Tysklind, Chunye Lin, Mengchang He, Baodong Wang, Ming Xin
更新时间: 2019-09-28
摘要: Under the gradients of salinity and redox, the transportation and distribution of dissolved, particulate, and sedimentary arsenic present differences from estuary to bay. Samples of water, suspended particulate sediment (SPS), and sediment from the Jiaozhou Bay were analyzed. The concentrations of arsenic decreased significantly from the estuaries toward the bay. The sedimentary arsenic mostly existed as hydrous oxide-bound and residual fractions and tended to be attached to smaller particles. Sedimentary particles were more capable of absorbing arsenic than SPS and the capacity increased from the estuaries toward the bay. The spatial distribution of arsenic was impacted by the residual currents, resulting in higher contents of dissolved arsenic in the eastern coastal zone and higher concentrations of sedimentary arsenic in the inner bay. In water, total phosphorus (TP), dissolved organic carbon (DOC), and alkalinity had significant positive correlations with the dissolved arsenic. In sediments, Fe oxides and sediment organic matter (SOM) would promote adsorption of arsenic. The significant correlation between non-residual fractions and enrichment factors of arsenic indicated that the sedimentary arsenic was more likely to originate from anthropogenic sources, mainly impacted by riverine transport from the eastern urban regions and agricultural production in the western farmland.
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25864. 题目: Soil organic carbon fractions and ¹⁴C ages through 70 years of cropland cultivation
文章编号: N19092802
期刊: Soil and Tillage Research
作者: Xia Yu, Weijian Zhou, Peng Cheng, Yunqiang Wang, Yaoyao Hou, G.S. Burr, Xiaohu Xiong, Ya Wang, Ling Yang, John Dodson
更新时间: 2019-09-28
摘要: Understanding the biogeochemistry of soil organic carbon (SOC) and SOC components is essential to assess soil quality and management practices in reclaimed croplands. Here we study the radiocarbon (¹⁴C) ages in profiles to a depth of 500 cm for five cultivation timespans: 5, 15, 35, 60, and at least 70 years from the Gutun watershed on the Chinese Loess Plateau. We isolated an acid-extractable SOC component (F1), three temperature stepped-combustion SOC components: F2 (400 °C), F3 (600 °C), and F4 (900 °C), and measured their ¹⁴C ages. Our results show that SOC stocks in reclaimed soils declined from cultivation times of 5 years (R5) to 15 years (R15), then increased with longer cultivation times, until 70 years (R70). The SOC content of the F2 and F3 fractions was higher than F1 and F4 over the past 60 years, while the F4 fraction in R70 had the highest value. Since the newly reclaimed croplands were heavily fertilized, R5 had high SOC and carbon management index (CMI) values, and ¹⁴C ages close to the other SOC fractions in the surface soil. The ¹⁴C ages of SOC fractions in deep soils were older than others, indicating a weak capacity to fix fresh C that infiltrated the deeper soils in R5. R70 contained the highest SOC stocks, but with a large proportion of old, non-labile SOC that contributed to relatively low SOC quality and CMI. Therefore, we predict that the R70 site would be unable to sustain optimal maize productivity. The SOC stocks under R35 were significantly lower than those from R5 and R70, but contained a high proportion of labile SOC, with relatively young ¹⁴C ages (compared to R60), even to a depth of 500 cm. This observation suggests that planting forest nurseries can improve SOC quality and promote SOC sequestration even in relatively deep soils. This study demonstrates the efficacy of labile SOC content and ¹⁴C ages as measures of SOC quality, and our findings offer useful guidance for the management of reclaimed croplands.

25865. 题目: Human activities determine quantity and composition of dissolved organic matter in lakes along the Yangtze River
文章编号: N19092801
期刊: Water Research
作者: Dong Liu, Yingxun Du, Shujie Yu, Juhua Luo, Hongtao Duan
更新时间: 2019-09-28
摘要: Dissolved organic matter (DOM) plays important roles in the aquatic biogeochemical cycle and the global carbon cycle. However, it is highly spatially and temporally varied due to complex sources from the catchment (allochthonous) and from within the system (autochthonous). Satellite remote sensing provides the ability to monitor DOM and identify the spatio-temporal variations in lakes on a global or regional scale. In this study, field work was conducted in 55 lakes in August 2012 along the middle and lower reaches of the Yangtze River (MLR-YR), where most lakes were characterized by eutrophication due to intense human activities. The results showed that both colored DOM (CDOM) and total DOM differed significantly by and were linearly related to the human-induced trophic state index (TSI), with R² = 0.41 and 0.61, respectively. Autochthonous substances by phytoplankton contributed to 38.5% of CDOM and 35.2% of DOM, and allochthonous terrestrial substance indexed by land cover change and aquaculture contributed to almost half, with 49.7% of CDOM and 49.8% of DOM. In total, human activities explained as much as 81.7% and 87.5% of the variations in CDOM and DOM, respectively. Finally, a flowchart for estimating DOM from satellite-derived TSI was proposed. This study has great significance for synchronously monitoring and managing aquatic environment quality in regional eutrophic lakes around the world.
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25866. 题目: Soil organic matter prevails over heavy metal pollution and vegetation as a factor shaping soil microbial communities at historical Zn–Pb mining sites
文章编号: N19092712
期刊: Chemosphere
作者: Anna M. Stefanowicz, Paweł Kapusta, Szymon Zubek, Małgorzata Stanek, Marcin W. Woch
更新时间: 2019-09-27
摘要: This study examined the effects of soil heavy metals, macronutrients, texture and pH as well as plant species richness and composition on soil respiration, enzymatic activity, microbial biomass, metabolic quotient (qCO₂) and arbuscular mycorrhizal fungi (AMF) at sites of historical Zn–Pb mining. The study was conducted both on a large scale (65 heaps scattered over the area of 750 km²) and on a small scale (25 plots along two 48 m transects extending from heaps to adjacent fallow fields). Total concentrations of metals exceeded 400 (Cd), 20,000 (Pb) and 80,000 (Zn) mg kg⁻¹ at the most polluted sites. Although they decreased along the heap-fallow direction, they still remained above environmental standards in fallow soils. In contrast, some soluble metal forms increased with the increasing distance from heaps. Soil organic matter had the strongest positive effect on most microbial parameters. Total and/or available heavy metals exhibited significant negative effects on microbial biomass, enzymatic activity and AMF, and a positive effect on qCO₂. Organic matter alleviated negative effects of heavy metals on microorganisms; they were not observed where the increase in the contamination was accompanied by the increase in organic matter content. Plant species richness affected positively enzymatic activity and mycorrhization level. Plant species composition possibly contributed to the formation of soil microbial communities, but its effect was entangled in that of heavy metals as plant communities changed along pollution gradients (from metal-tolerant grasslands dominated by Festuca ovina to calcareous grasslands and ruderal communities at less polluted sites).
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25867. 题目: Quantitative forecasting black (pyrogenic) carbon in soils by chemometric analysis of infrared spectra
文章编号: N19092711
期刊: Journal of Environmental Management
作者: José M. De la Rosa, Marco A. Jiménez-González, Nicasio T. Jiménez-Morillo, Heike Knicker, Gonzalo Almendros
更新时间: 2019-09-27
摘要: A detailed and global quantitative assessment of the distribution of pyrogenic carbon (PyC) in soils remains unaccounted due to the current lack of unbiased methods for its routine quantification in environmental samples. Conventional oxidation with potassium dichromate has been reported as a useful approach for the determination of recalcitrant C in soils. However, its inaccuracy due to the presence of residual non-polar but still non-PyC requires additional analysis by ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy, which is expensive and time consuming. The goal of this work is to examine the possibility of applying infrared (IR) spectroscopy as a potential alternative. Different soil type samples (paddy soil, Histic Humaquept, Leptosol and Cambisol) have been used. The soils were digested with potassium dichromate to determine the PyC content in environmental samples. Partial Least Squares (PLS) regression was used to build calibration models to predict PyC from IR spectra. A set of artificially produced samples rich in PyC was used as reference to observe in detail the IR bands derived from aromatic structures resistant to dichromate oxidation, representing black carbon. The results showed successful PLS forecasting of PyC in the different samples by using spectra in the 1800–400 cm⁻¹ range. This lead to significant (P < 0.05) cross-validation coefficients for PyC, determined as the aryl C content of the oxidized residue. The Variable Importance for Projection (VIP) traces for the corresponding PLS regression models plotted in the whole IR range indicates the extent to which each IR band contributes to explain the aryl C and PyC contents. In fact, forecasting PyC in soils requires information from several IR regions. In addition to the expected IR bands corresponding to aryl C, other bands are informing about the patterns of oxygen-containing functional groups and the mineralogical composition characteristic of the soils with greater black carbon storage capacity. The VIP traces of the charred biomass samples confirm that aromatic bands (1620 and 1510 cm⁻¹) are the most important in the prediction model for PyC-rich samples. These facts suggest that the mid-IR spectroscopy could be a potential tool to estimate the black carbon.

25868. 题目: Waste-derived compost and biochar amendments for stormwater treatment in bioretention column: Co-transport of metals and colloids
文章编号: N19092710
期刊: Journal of Hazardous Materials
作者: Yuqing Sun, Season S. Chen, Abbe Y.T. Lau, Daniel C.W. Tsang, Sanjay K. Mohanty, Amit Bhatnagar, Jörg Rinklebe, Kun-Yi Andrew Lin, Yong Sik Ok
更新时间: 2019-09-27
摘要: Bioretention systems, as one of the most practical management operations for low impact development of water recovery, utilize different soil amendments to remove contaminants from stormwater. For the sake of urban sustainability, the utilization of amendments derived from waste materials has a potential to reduce waste disposal at landfill while improving the quality of stormwater discharge. This study investigated the efficiency of food waste compost and wood waste biochar for metal removal from synthetic stormwater runoff under intermittent flow and co-presence of colloids. Throughout intermittent infiltration of 84 pore volumes of stormwater, columns amended with compost and biochar removed more than 50–70% of influent metals, whereas iron-oxide coated sand was much less effective. Only a small portion of metals adsorbed on the compost (< 0.74%) was reactivated during the drainage of urban pipelines that do not flow frequently, owing to abundant oxygen-containing functional groups in compost. In comparison, co-existing kaolinite enhanced metal removal by biochar owing to the abundance of active sites, whereas co-existing humic acid facilitated mobilization via metal-humate complexation. The results suggest that both waste-derived compost and biochar show promising potential for stormwater harvesting, while biochar is expected to be more recalcitrant and desirable in field-scale bioretention systems.
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25869. 题目: Biochar-supported nanoscale zero-valent iron as an efficient catalyst for organic degradation in groundwater
文章编号: N19092709
期刊: Journal of Hazardous Materials
作者: Zhe Li, Yuqing Sun, Yang Yang, Yitong Han, Tongshuai Wang, Jiawei Chen, Daniel C.W. Tsang
更新时间: 2019-09-27
摘要: High-efficiency and cost-effective catalysts are critical to completely mineralization of organic contaminants for in-situ groundwater remediation via advanced oxidation processes (AOPs). The engineered biochar is a promising method for waste biomass utilization and sustainable remediation. This study engineers maize stalk (S)- and maize cob (C)-derived biochars (i.e., SB300, SB600, CB300, and CB600, respectively) with oxygen-containing functional groups as a carbon-based support for nanoscale zero-valent iron (nZVI). Morphological and physiochemical characterization showed that nZVI could be impregnated within the framework of the synthesized Fe-CB600 composite, which exhibited the largest surface area, pore volume, iron loading capacity, and Fe⁰ proportion. Superior degradation efficiency (100% removal in 20 min) of trichloroethylene (TCE, 0.1 mM) and fast pseudo-first-order kinetics (k_obs =22.0 h⁻¹) were achieved via peroxymonosulfate (PMS, 5 mM) activation by the Fe-CB600 (1 g L⁻¹) under groundwater condition (bicarbonate buffer solution at pH = 8.2). Superoxide radical and singlet oxygen mediated by Fe⁰ and oxygen-containing group (i.e., CO) were demonstrated as the major reactive oxygen species (ROSs) responsible for TCE dechlorination. The effectiveness and mechanism of the Fe/C composites for rectifying organic-contaminated groundwater were depicted in this study.
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25870. 题目: Ferrous ion mitigates the negative effects of humic acid on removal of 4-nitrophenol by zerovalent iron
文章编号: N19092708
期刊: Journal of Hazardous Materials
作者: Hejie Qin, Daqiang Yin, Joel Z. Bandstra, Yuankui Sun, Guomin Cao, Xiaohong Guan
更新时间: 2019-09-27
摘要: In this study, Fe²⁺ addition was employed to overcome the negative effects of humic acid (HA) on contaminant removal by zerovalent iron (ZVI), and its feasibility to improve electron efficiency of ZVI was also tested. HA at high concentrations suppressed the removal of 4-nitrophenol (4-NP) by ZVI, while the addition of 0.25–1.0 mM Fe²⁺ could greatly mitigate this inhibitory effect and enhance 4-NP reduction. Specifically, with a mixed-order model, global fitting results showed that the addition of Fe²⁺ increased the rate constant from 0.124 × 10⁻²–0.219 × 10⁻² mM/min to 0.227 × 10⁻²–0.417 × 10⁻² mM/min and shortened lag period from 19.7–47.9 min to 8.0–15.2 min for 4-NP removal. The mechanistic investigation revealed this trend could be explained by the following aspects: i) Fe²⁺ can facilitate the generation of Fe(II)-containing oxides, which can act as an electron mediator or direct electron donor for 4-NP reduction; ii) the presence of Fe²⁺ could lead to aggregation of HA particles and accordingly reduced its coverage on ZVI surface. But the results of respike experiments indicate that Fe²⁺ addition did not show remarkable effect on the electron efficiency of 4-NP by ZVI, which should be associated with that Fe²⁺ was not able to favor the enrichment of 4-NP on ZVI surface.
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25871. 题目: Seasonal and spatial variability in the optical characteristics of DOM in a temperate shelf sea
文章编号: N19092707
期刊: Progress in Oceanography
作者: Nealy Carr, Clare E. Davis, Sabena Blackbird, Lucie R. Daniels, Calum Preece, Malcolm Woodward, Claire Mahaffey
更新时间: 2019-09-27
摘要: The Celtic Sea is a productive temperate sea located on the Northwest European Shelf. It is an important pathway for the delivery of land-derived material to the North Atlantic Ocean, including dissolved organic matter (DOM). The aim of this study was to determine the seasonal and spatial variability in the magnitude, source and composition of DOM at three sites representing on shelf, central shelf and shelf edge regions in the Celtic Sea, using observations collected during the UK Shelf Sea Biogeochemistry (SSB) research programme (November 2014 – August 2015). The concentration of dissolved organic carbon (DOC) alongside DOM absorbance and fluorescence indices were measured and fluorescence Excitation and Emission Matrices (EEMs) combined with Parallel Factor Analysis (PARAFAC) were used to assess DOM composition and lability. The PARAFAC model identified four unique fluorescent components for autumn (November 2014), winter (March 2015), spring (April 2015) and summer (July 2015) consisting of two humic-like components attributed to terrestrial (C1) and marine sources (C2), and two protein components identified as tyrosine-like (C3) and tryptophan-like (C4) attributed to in situ production. DOC varied seasonally and there were strong cross shelf trends. The protein components (C3 and C4) exhibited large seasonal and within season variability particularly during productive periods. In contrast, there were persistent cross shelf gradients in the CDOM absorption coefficient at 305 nm (a305), the UV specific absorbance at 280 nm (SUVA₂₈₀), the humification index (HIX), and the humic-like fluorescent components (C1 and C2), which were higher in the on shelf region and decreased towards the shelf edge. The humic-like components and the slope ratio (SR) were significantly correlated with salinity throughout all seasons, indicating a strong influence of terrestrially-derived organic matter in the Celtic Sea, with potentially up to 35% of DOC in the central shelf during winter originating from terrestrial inputs. Results from this study illustrate the importance of monitoring DOM quantitatively and qualitatively for a better understanding of the supply, production, cycling and export of this dynamic organic carbon pool in shelf seas.

25872. 题目: Response of oxidative stability of aggregate-associated soil organic carbon and deep soil carbon sequestration to zero-tillage in subtropical India
文章编号: N19092706
期刊: Soil and Tillage Research
作者: Kingshuk Modak, Avijit Ghosh, Ranjan Bhattacharyya, Dipak Ranjan Biswas, Tapas Kumar Das, Shrila Das, Geeta Singh
更新时间: 2019-09-27
摘要: Conservation agriculture (CA) practices have been recognized to enhance soil health by optimizing key soil attributes and are being implemented worldwide. But, the potential of CA to soil organic carbon (SOC) sequestration and enhancing its oxidative stability (OXS) in deep layers and aggregates are less highlighted. Thus, our aim was to study the long-term (9 years) effects of contrasting tillage treatments and residue addition on soil aggregation, OXS in bulk soils (0–5, 5–15, 15–30 and 30–60 cm) and aggregates (0–5 and 5–15 cm), and C pools and sequestration (0–5, 5–15, 15–30 and 30–60 cm). For this an experiment was laid out in a split plot design with two tillage practices in main plots (zero-tillage: ZT and conventional tillage: CT) and four residue management practices in sub-plots (No residue: NR, wheat residue: WR, soybean residue: SR and wheat + soybean residue: WR + SR) in 2008. Soil samples collected from 0–5, 5–15, 15–30 and 30–60 cm layers were analyzed. The ZT plots had ∼26 and 15% higher macroaggregate associated C than CT plots in 0–5 and 5–15 cm soil layers, respectively. In macroaggregates of first two soil layers, recalcitrant C was (a) ∼57, 76 and 63%; and (b) 85, 59 and 40% greater in WR + SR, SR and WR plots over NR, respectively. Similar trend was observed for microaggregate associated recalcitrant C. The OXS of C in ZT was ∼21% more than CT, but residue addition had no impact on OXS. In 15–30 and 30–60 cm soil layers, OXS in WR + SR plots were ∼28 and 31% greater than NR. Although deep soil layers (15–60 cm) accounted for ∼68% of sequestered C, tillage had no impact on deep soil C sequestration. About ∼85% of total SOC stock was accumulated in soil aggregates of topsoil. Contrarily, of total sequestered SOC in top soil, only ∼30% was sequestered by aggregates of that layer indicating the role of silt + clay fraction in SOC sequestration in tropical Inceptisol. Thus, SOC sequestration in tropical soil is very sluggish and would require long time to meet saturation deficit. Interestingly, crop yield was significantly influenced by active and labile C of bulk soils and aggregates, but not by recalcitrant C in ZT plots. Thus, ZT in combination with crop residue retention has great potential in enhancing deep soil C sequestration and C stability of soil aggregates to sustain soil health and crop production.

25873. 题目: No-tillage did not increase organic carbon storage but stimulated N₂O emissions in an intensively cultivated sandy loam soil: A negative climate effect
文章编号: N19092705
期刊: Soil and Tillage Research
作者: Yuhui Niu, Yanjiang Cai, Zengming Chen, Jiafa Luo, Hong J Di, Hongyan Yu, Anning Zhu, Weixin Ding
更新时间: 2019-09-27
摘要: Although numerous studies have been conducted on the effects of no-tillage on carbon (C) sequestration in agricultural systems, there is still no consensus on the balance between the potential of C sequestration and nitrous oxide (N₂O) or nitric oxide (NO) emissions. A no-tillage field experiment in the North China Plain was established in 2006 and the influence of no-tillage on N₂O and NO emissions was monitored under an annual wheat-maize cropping system. The study included four treatments: no-tillage (NT) and conventional tillage (CT) soils amended with N fertilizer at a rate of 225 kg N ha^–1 for wheat and 195 kg N ha^–1 for maize (NTN and CTN) and without N fertilizer (NT0 and CT0). Three years of no-tillage significantly (p < 0.05) increased soil organic C (SOC) content by 12.2% in the 0–5 cm soil layer, possibly due to the surface aggregation of organic C derived from crop roots and exudates, but did not alter SOC pool in the 0–30 cm profile. Annual N₂O emissions in the NT0 and CT0 treatments were 0.53 and 0.57 kg N₂O-N ha^–1, respectively, and were significantly (p < 0.05) increased to 0.96 kg N₂O-N ha^–1 in CTN and to 1.23 kg N₂O-N ha^–1 in NTN. Remarkable differences in N₂O emissions between CTN and NTN were observed during the maize growing season. In contrast, NO emissions were not affected by the tillage regimes regardless of N fertilization. The mean ratios of NO/N₂O fluxes in N-unfertilized plots were 0.26–0.29 and 1.79–2.11 for the maize and wheat season, respectively, indicating that both NO and N₂O were primarily derived from denitrification during the maize growing season and from nitrification under wheat cultivation. Under N-fertilized plots, the ratios increased to 1.44–2.02 and 5.00–6.03 for the maize and wheat season, respectively, with significantly (p < 0.05) lower values in NTN plots than in CTN plots. The N₂O emission factors for N applied in the wheat-maize rotation system were 0.16% and 0.09% for NTN and CTN, respectively, which was far lower than the IPCC Tier 1 default value (1.0%), primarily due to the absence of irrigation after fertilization in maize season and low temperature in wheat season. The results suggest that the 3-year no-tillage regime with residue removal did not substantially increase C storage in the 0–30 cm profile, but stimulated N₂O emissions primarily by increasing denitrification.

25874. 题目: Changes in humus carbon fractions in paddy soil given different organic amendments and mineral fertilizers
文章编号: N19092704
期刊: Soil and Tillage Research
作者: Wenhai Mi, Yan Sun, Qiang Gao, Mingyue Liu, Lianghuan Wu
更新时间: 2019-09-27
摘要: The effects of 4 years of combined application of mineral fertilizer with a variety of organic materials on soil humus carbon fractions were evaluated in a low-fertility paddy soil. Five treatments were selected: (1) no fertilizer, (2) mineral fertilizer alone, (3) mineral fertilizer plus green manure at 3.6 Mg ha⁻¹, (4) mineral fertilizer plus cattle manure at 4.7 Mg ha⁻¹, and (5) mineral fertilizer plus rice straw at 3.0 Mg ha⁻¹. The following properties were determined: water soluble substance carbon, water floating substance carbon, humic acid carbon, fulvic acid carbon, total alkali-extractable humic carbon, and humin carbon. The ratio of humic acid carbon / fulvic acid carbon and precipitation ratio (the percentage of humic acid in the sum of humic acid and fulvic acid) were calculated. The results indicated that application of mineral fertilizer with organic amendments respectively increased the concentrations of humic acid carbon and total alkali-extractable humic carbon by 18.3 − 31% and 11.7 − 21.3% in 0 − 5 cm, humin carbon by 14.9 − 22.5% in 5 − 10 cm, compared to mineral fertilizer alone. However, no differences in fulvic acid carbon concentration were recorded among the fertilization treatments in 0 − 5 cm. Furthermore, organic inputs exhibited minor influences on humus carbon fractions (−4.2 − 22% and 2.8 − 8% for humic acid carbon; −0.6 − 13% and 1.6 − 4.4% for total alkali-extractable humic carbon; 0.3 − 9.5% and −0.4 − 4.4% for humin carbon; −0.7 − 5.3% and 0.4 − 1.3% for fulvic acid carbon) in 10 − 20 cm and 20 − 30 cm, respectively. Among the three organic amendments, surface placement of cattle manure resulted in the highest concentrations of water soluble substance carbon (0.26 g kg⁻¹, 0.22 g kg⁻¹, and 0.21 g kg⁻¹), humic acid carbon (4.6 g kg⁻¹, 3.2 g kg⁻¹, and 2.1 g kg⁻¹), total alkali-extractable humic carbon (7.1 g kg⁻¹, 5.6 g kg⁻¹, and 4.2 g kg⁻¹), and humin carbon (11.4 g kg⁻¹, 11 g kg⁻¹, and 7.8 g kg⁻¹) in upper soil layer (0 − 5 cm, 5 − 10 cm, and 10 − 20 cm). In addition, the precipitation ratio value tended to be significantly higher (23.2% in 0 − 5 cm, 24.6% in 5 − 10 cm, and 16.5% in 10 − 20 cm, P < 0.05) in mineral fertilizer with cattle manure additions than mineral fertilizer alone. There were significant correlations between rice grain yield and total soil organic carbon (R² = 0.72, n = 15, P < 0.01), humic acid carbon (R² = 0.79, n = 15, P < 0.001), and humin carbon (R² = 0.59, n = 15, P < 0.05) in the 0−5 cm soil depth. In summary, our results showed that combined application of mineral fertilizer with cattle manure was the most effective management practice to increase humus carbon pool, which could be regarded as a useful indicator of the carbon sequestration process in paddy soil.

25875. 题目: Spatio-temporal assessment of topsoil organic carbon stock change in Hungary
文章编号: N19092703
期刊: Soil and Tillage Research
作者: Gábor Szatmári, Béla Pirkó, Sándor Koós, Annamária Laborczi, Zsófia Bakacsi, József Szabó, László Pásztor
更新时间: 2019-09-27
摘要: We compiled maps for the topsoil (0–30 cm) organic carbon (SOC) stock and its prediction uncertainty in Hungary at 100 m resolution for the years 1992 and 2010 using a machine learning algorithm, namely, quantile regression forest. 10-fold cross-validation was used for checking the accuracy of the spatial predictions and uncertainty quantifications for both years. The performance of the spatial predictions and uncertainty quantifications was appropriate, which was verified by the computed biases (0.15 and 0.30 for 1992 and 2010), root mean square errors (21.99 and 21.39 for 1992 and 2010), accuracy plots and the G statistics (0.96 for both years) as well. Based on the compiled SOC stock maps, we assessed the spatio-temporal change of SOC stocks on the territory of Hungary. A scheme was elaborated based on the quantified prediction uncertainties for identifying and delimiting significant and tendentious changes of SOC stock during the respective period. The total SOC stock in the topsoil was found to be 424.41 Tg (1 teragram = 10¹² grams) in 1992 and 451.59 Tg in 2010. Thus SOC stock increased by 27.18 Tg over the respective period. On those areas where the land use types did not change, we observed that the SOC stock increased under forests (by 16.29 Tg) and pastures (by 2.48 Tg), decreased under wetlands (by 0.49 Tg) and did not change under agricultural areas. On those areas where the land use has been changed during the 18-year period, we found that afforestation has increased the SOC stock, whereas cultivation of pastures has decreased it. Due to soil sealing 34,000 ha of soil have been lost resulting in approximately 1.7 Tg carbon loss. We compared our own total SOC stock estimate and map referring to 1992 with other estimates and maps provided by global and continental initiatives. The comparisons have pointed out that the SOC stock map of 1992 outperformed these maps. We recommend applying the SOC stock map of 1992 as a baseline for Hungary.
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25876. 题目: Carbon-nutrient stoichiometry drives phosphorus immobilization in phototrophic biofilms at the soil-water interface in paddy fields
文章编号: N19092702
期刊: Water Research
作者: Junzhuo Liu, Pengfei Sun, Rui Sun, Sichu Wang, Bo Gao, Jun Tang, Yonghong Wu, Jan Dolfing
更新时间: 2019-09-27
摘要: Phototrophic biofilms are distributed widely at the sediment/soil-water interfaces (SWI) in paddy fields, where they immobilize phosphorus, thereby reducing its runoff loss. However, how soil carbon, nutrient availability and nutrient ratios drive the phototrophic biofilm community and its contribution to phosphorus cycling is largely unknown. A large scale field investigation in Chinese paddy fields reported here shows that soil organic carbon (SOC) and soil total nitrogen (STN) contents rather than soil total phosphorus (STP) triggered phosphorus immobilization of paddy biofilms, as they changed algal diversity and EPS production. High C: P and N: P ratios favored phosphorus immobilization in biofilm biomass via increasing the abundance of green algae. The C: N ratio on the other hand had only a weak effect on phosphorus immobilization, being counteracted by SOC or STN. Results from this study reveal how the in-situ interception of phosphorus in paddy fields is driven by soil carbon, nutrient availability and nutrient ratios and provide practical information on how to reduce runoff losses of phosphorus by regulating SOC and STN contents.
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25877. 题目: Synergistic removal of tylosin/sulfamethoxazole and copper by nano-hydroxyapatite modified biochar
文章编号: N19092701
期刊: Bioresource Technology
作者: Zhen Li, Miao Li, Qi Che, Yandan Li, Xiang Liu
更新时间: 2019-09-27
摘要: Antibiotics and heavy metals are frequently detected simultaneously in aquatic environment. In this study, we investigated the removal performance of biochar modified with nano-hydroxyapatite (nHAP, nHAP@biochar) on tylosin (TYL) /sulfamethoxazole (SMX) and Cu(II) simultaneously. Six nHAP@biochars were prepared with different feedstock and nHAP and biomass ratios. The influences of feedstock and nHAP and biomass ratios, interaction of TYL/SMX and Cu(II) and thermodynamic study were investigated. The adsorption quantities on nHAP@biochars prepared by wood-processing residues were higher than by Chinese medicine residues. The adsorption amounts of TYL decreased with the addition of Cu(II), while the adsorption quantities of SMX increased. The adsorptions of Cu(II) were promoted by TYL and changed slightly with the increasing of SMX. Specific surface area and pore size were two of the main factors influencing the adsorption capacities of nHAP@biochars. According to density functional theory, nHAP@biochar-TYL-Cu and nHAP@biochar-Cu-SMX were more existed in the systems.

25878. 题目: The Role of Dissolved Organic Matter Composition in Determining Photochemical Reactivity at the Molecular Level
文章编号: N19092611
期刊: Environmental Science & Technology
作者: Stephanie M. Berg, Quinn T. Whiting, Joseph A. Herrli, Ronan Winkels, Kristine H. Wammer, Christina K. Remucal
更新时间: 2019-09-26
摘要: Dissolved organic matter (DOM) composition influences its ability to form photochemically produced reactive intermediates (PPRI). While relationships have been established between bulk DOM properties and triplet DOM (3DOM) and singlet oxygen (1O2) quantum yields, contradictory evidence exists for hydroxyl radical (•OH) and hydroxylating species. Furthermore, little is known about these relationships at the molecular level. We evaluated DOM composition and photochemical reactivity of water samples from a wastewater treatment plant and the St. Louis River in Minnesota and Wisconsin, U.S.A. Bulk characterization using ultraviolet–visible spectroscopy demonstrates that color and apparent size of DOM decrease downstream, while molecular composition analysis using Fourier-transform ion cyclotron resonance mass spectrometry reveals that saturation and chemodiversity is highest near Lake Superior. 3DOM quantum yield coefficients and 1O2 quantum yields increase downstream and correlate strongly with saturated formulas. Similar results are observed for carbon-normalized photodegradation rate constants of atorvastatin, carbamazepine, and venlafaxine, which react primarily with 3DOM and 1O2. In contrast, •OH quantum yields are lowest downstream and correlate with less saturated, more oxygenated DOM, suggesting that 3DOM is not its major precursor. Mixed relationships are observed for DEET, which reacts with multiple PPRI. Molecular-level compositional data reveal insights into the differing formation pathways of individual PPRI, but information about specific contaminants is needed to predict their photochemical fate.

25879. 题目: Sorption and Desorption Mechanisms of Cationic and Zwitterionic Per- and Polyfluoroalkyl Substances in Natural Soils: Thermodynamics and Hysteresis
文章编号: N19092610
期刊: Environmental Science & Technology
作者: Feng Xiao, Bosen Jin, Svetlana A. Golovko, Mikhail Y. Golovko, Baoshan Xing
更新时间: 2019-09-26
摘要: Sorption linearity and reversibility are implicit in models for the fate and transport of per- and polyfluoroalkyl substances (PFAS). In this study, however, we found that the sorption of cationic and zwitterionic PFAS in natural soils was highly nonlinear. The nonlinearity was so severe that it led to a variation in the coefficient of sorption by several orders of magnitude over the experimental concentration range. This implies a considerable increase in sorption as concentration falls in the natural environment. Sorption of cationic PFAS correlated strongly with the soil organic matter (SOM) content and was reversible in all soils. Sorption of zwitterionic PFAS, on the other hand, displayed concentration-dependent hysteresis in soils with a low SOM content. The irreversibility, which was associated with neither SOM, pore deformation, nor surface complexation, was likely caused by the entrapment of molecules in porous structures within inorganic components of soil aggregates. Furthermore, electrostatic interactions with negatively charged soil constituents and the hydrophobic effect were found to be major sorption driving forces for cationic/zwitterionic PFAS at low and high concentrations, respectively. The maximum electrostatic potential of PFAS ions, computed using density functional theory, was found to be a useful predictor of the sorption of ionic PFAS species.

25880. 题目: The potential role of sediment organic phosphorus in algal growth in a low nutrient lake
文章编号: N19092609
期刊: Environmental Pollution
作者: Zhaokui Ni, Shengrui Wang, Jingjing Cai, Hong Li, Alan Jenkins, Stephen C. Maberly, Linda May
更新时间: 2019-09-26
摘要: The role of sediment–bound organic phosphorus (P_o) as an additional nutrient source is a component of internal P budgets in lake system that is usually neglected. Here we examined the relative importance of sediment P_o to internal P load and the role of bioavailable P_o in algal growth in Lake Erhai, China. Lake Erhai sediment extractable P_o accounted for 11–43% (27% average) of extractable total P, and bioavailable P_o accounted for 21–66% (40%) of P_o. The massive storage of bioavailable P_o represents an important form of available P, essential to internal loads. The bioavailable P_o includes mainnly labile monoester P and diester P was identified in the sequential extractions by H₂O, NaHCO₃, NaOH, and HCl. 40% of H₂O−P_o, 39% of NaHCO₃−P_o, 43% of NaOH−P_o, and 56% of HCl−P_o can be hydrolyzed to labile monoester and diester P, suggesting that the bioavailability of P_o fractions was in decreasing order as follows: HCl−P_o > NaOH−P_o > H₂O−P_o > NaHCO₃−P_o. It is implied that traditional sequential fractionation of P_o might overestimate the availability of labile P_o in sediments. Furthermore, analysis of the environmental processes of bioavailable P_o showed that the stabler structure of dissloved organic matter (DOM) alleviated the degradation and release of diester P, abundant alkaline phosphatase due to higher algal biomass promoted the degradation of diester P. The stability of DOM structure and the degradation of diester P might responsible for the spatial differences of labile monoester P. The biogeochemical cycle of bioavailable P_o replenishs available P pools in overlying water and further facilitate algal growth during the algal blooms. Therefore, to control the algal blooms in Lake Erhai, an effective action is urgently required to reduce the accumulation of P_o in sediments and interrupt the supply cycle of bioavailable P_o to algal growth.
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