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23521. 题目: Variations in soil organic carbon decompositions of different land use patterns on the tableland of Loess Plateau
文章编号: N19121306
期刊: Environmental Science and Pollution Research
作者: Mengyun Liu, Mengmeng Liu, Peng Li, Jinghan Yang, Jing Wang, Qingrui Chang
更新时间: 2019-12-13
摘要: Land use patterns are one of the critical factors affecting soil carbon sequestration or decomposition and greenhouse gas emissions. The accurate evaluation of its change is particularly crucial for the carbon cycle of the terrestrial ecosystem and global climate change. This paper examined the dynamic soil respiration by means of the indoor airtight culture method and static box-gas chromatography under the land uses of the farmland, natural grassland, shrub forestland, arbor and shrub mixed forestland, and arbor forestland on the tableland of Loess Plateau. The results showed that soil organic carbon mineralization and soil respiration rate were influenced by the land use type. (1) The content and rate of soil mineralizable carbon in grassland were significantly higher than that in forestland and farmland, and that in forestland significantly higher than that in the farmland (P < 0.05). The trend of organic carbon mineralization was rapid in the initial stage of culture (by the rate of 30.02~238.56 mg kg⁻¹ h⁻¹ in the first 0.5 h) and slowed down in the later stage (by the rate of 1.07~1.95 mg kg⁻¹ h⁻¹ in 1575 h). In the soil of grassland, the accumulation of mineralizable organic carbon in the 0–5-cm layer was 1.20~1.64 times that in the soil of forestland and 1.82 times that of farmland. Compared with the 0–5-cm soil layer, there were decreases in the 5–20-cm soil layer under all land uses, with a decline of up to 48% in farmland. (2) The soil carbon mineralization potential of different land use types ranged from 0.81 to 2.70 mg kg⁻¹, that of grassland was significantly higher than that of farmland (P < 0.05), and the soil organic carbon decomposition rate constant (k) under shrub forestland was significantly higher than that under other land use types (P < 0.05). The highest organic carbon mineralization capacity and the lowest sequestration were in the soil of farmland, while that in grassland had the lowest organic carbon mineralization capacity and the highest sequestration. (3) The cumulative amount of soil respiration was highest under the natural grassland, followed by the shrub forestland, and lowest under the farmland. The soil respiration rate was positively correlated with soil temperature, and its correlation with soil water content was positive in the wet season (May through October) and negative in the dry season (November through April in the following year). (4) The soil respiration rate showed obvious seasonal differences. After the conversion of farmland to forestland, it would be rising in the content of soil organic carbon and labile organic carbon, and be going down in the temperature sensitivity (Q₁₀). In summary, by converting farmland to forestland or grassland, the sequestration of soil organic carbon had greatly been enhanced, and the possibility of soil greenhouse gas emissions had reduced on the tableland of Loess Plateau.

23522. 题目: Spatial variability of sediment methane production and methanogen communities within a eutrophic reservoir: Importance of organic matter source and quantity
文章编号: N19121305
期刊: Limnology and Oceanography
作者: Megan E. Berberich, Jake J. Beaulieu, Trinity L. Hamilton, Sarah Waldo, Ishi Buffam
更新时间: 2019-12-13
摘要: Freshwater reservoirs are an important source of the greenhouse gas methane (CH₄) to the atmosphere, but global emission estimates are poorly constrained (13.3–52.5 Tg C yr⁻¹), partially due to extreme spatial variability in emission rates within and among reservoirs. Spatial heterogeneity in the availability of organic matter (OM) for biological CH₄ production by methanogenic archaea may be an important contributor to this variation. To investigate this, we measured sediment CH₄ potential production rates, OM source and quantity, and methanogen community composition at 15 sites within a eutrophic reservoir in Ohio, USA. CH₄ production rates were highest in the shallow riverine inlet zone of the reservoir, even when rates were normalized to OM quantity, indicating that OM was more readily utilized by methanogens in the riverine zone than in the transitional or lacustrine zones. Sediment stable isotopes and C:N indicated a greater proportion of terrestrial OM in the particulate sediment of this zone. Methanogens were present at all sites, but the riverine zone contained a higher relative abundance of methanogens capable of acetoclastic and methylotrophic methanogenesis, likely reflecting differences in decomposition processes or OM quality. While we found that methane potential production rates were negatively correlated with autochthonous carbon in particulate sediment OM, rates were positively correlated with indicators of autochthonous carbon in the porewater dissolved OM. It is likely that both dissolved and particulate sediment OM affect CH₄ production rates, and that both terrestrial and aquatic OM sources are important in the riverine methane production hot spot.

23523. 题目: Variations in stable carbon and nitrogen isotopes of particulate organic matter in surface waters of water-receiving area of Eastern Route of South-to-North Water Transfer Project, China
文章编号: N19121304
期刊: Environmental Science and Pollution Research
作者: Wei Hou, Shaohua Sun, Mingquan Wang, Binhe Gu, Xiang Li, Chengxiao Zhang, Ruibao Jia
更新时间: 2019-12-13
摘要: The purpose of this study was to assess the water quality and variations in stable carbon and nitrogen isotopes of particulate organic matter (δ¹³C_POM and δ¹⁵N_POM), as well as to evaluate the sources of carbon and nitrogen that contribute to the POM pools in lakes and reservoirs located in the water-receiving area of the Eastern Route of South-to-North Water Transfer Project (SNWTP) in Northern China. During each season from October 2013 to July 2014, samples of POM from 14 lakes and reservoirs in Northern China were collected. The lakes and reservoirs were meso-eutrophic with considerably high brackish ions (SO₄²⁻, 173 mg/L; Cl⁻, 296 mg/L) in Yangtze River lake, and high total nitrogen: total phosphorus ratio (averaged with 772) or dissolved inorganic nitrogen: soluble reactive phosphorus molar ratios (averaged with 1077) in mountainous reservoirs. The δ¹³C_POM, δ¹⁵N_POM, carbon to nitrogen (C/N) ratios showed significant seasonal variation, with ranges of − 32.5 to − 17.4‰, − 3.6 to 13.5‰, and 5.1–13.2, respectively, while they were hard to be distinguished among types of water sources. Principal component analysis (PCA) indicated that brackish ions, nutrients, and their molar ratios were the main factors influencing variations in δ¹³C_POM and δ¹⁵N_POM. δ¹³C_POM and C/N ratios suggested autochthonous primary production mainly contributed to POM during from April to October, while exogenous organic matter might mainly contribute these carbon pools in January. The low values of δ¹⁵N_POM (< 0‰) and negative correlation between δ¹⁵N_POM and TN suggested discharge of agricultural waste water (e.g., fertilizers, irrigation tailwater) in Bailanghe, Xinan, and Taihe Reservoir during the fertilization season, while higher values indicated domestic sewage input to waterbodies (e.g., Mishan, Gengjing, Donghai Reservoir). Our results suggested that the aquatic ecosystem in water-receiving area of SNWTP would be potentially affected by the inter-basin water diversion, and thus, ecosystem-based strategies were also presented accordingly.

23524. 题目: Influence of humic acid and its different molecular weight fractions on sedimentation of nanoscale zero-valent iron
文章编号: N19121303
期刊: Environmental Science and Pollution Research
作者: Yanan Wu, Haoran Dong, Lin Tang, Long Li, Yaoyao Wang, Qin Ning, Bin Wang, Guangming Zeng
更新时间: 2019-12-13
摘要: The effects of humic acid (HA) and its different molecular weight (MW) fractions on the sedimentation of nanoscale zero-valent iron (NZVI) in the absence and presence of cations (i.e., Na⁺/Mg²⁺/Ca²⁺) were investigated. Ultrafiltration (UF) was used as the method of fractionation to obtain four different MW fractions (separated by ultrafiltration membranes of 10 kDa, 50 kDa, and 100 kDa). Differing sedimentation behavior was observed for NZVI with different MW fractions of HA. Generally, the degree of settling of NZVI particles in the presence of high MW fractions of HA was lower than that of low MW fractions of HA and that without HA. The results were mainly attributed to the steric stabilization provided by the high MW fractions of HA. The presence of Na⁺/Mg²⁺/Ca²⁺ alone had insignificant influence on the settling of NZVI, but both Mg²⁺ and Ca²⁺ exerted an obvious influence on the settling of NZVI in the co-presence of HA. The settling behavior of NZVI was further examined in the co-presence of different MW fractions of HA and Ca²⁺. The co-presence of low MW HA fractions and Ca²⁺ led to a lower settling of NZVI. This might be due to the formation of a layer of HA-Ca²⁺ complex on the particle surface, providing stronger steric stabilization. Nevertheless, in the co-presence of high MW HA fractions and Ca²⁺, the settling of NZVI was initially reduced but accelerated with time, which might be due to the gradual aggregation of NZVI with time resulted from the bridging effect of HA-Ca²⁺ complex.

23525. 题目: Compositional dynamics of suspended sediment in the Rhine River: sources and controls
文章编号: N19121302
期刊: Journal of Soils and Sediments
作者: Marcel van der Perk, Alvaro Espinoza Vilches
更新时间: 2019-12-13
摘要: Purpose: Information on the geochemical composition of suspended sediments in rivers is crucial to identify sediment source type or area. In large river basins, however, the relation between sediment composition and its controlling factors is often obscured. This study aims to assess and improve the conceptual understanding on the factors and mechanisms that control the composition of suspended sediments in the River Rhine, one of the large European rivers, and to identify the dominant source types of elements. Materials and methods: We performed log-linear regression analysis and principal component analysis (PCA) on bi-weekly monitoring data of suspended sediment composition, supplemented with daily measurements of suspended sediment concentrations (SSC) and discharge at the Lobith monitoring station near the German-Dutch border for the period 2011–2016. Results and discussion: The statistical analyses show a consistent grouping of elements that display contrasting temporal variation or different responses to increased discharge. The contrasting behaviour also becomes manifest in the results from the PCA. A first component that explains about the half of the total variance in the entire dataset reflects the variation in clay content in the suspended sediment. A second component reflects anthropogenic pollution and explains about a quarter of the total variance. A third component probably reflects variation in sediment provenance. Conclusions: The majority of the temporal variation in suspended sediment composition can be attributed to variations in grain size (clay content), organic matter content, and anthropogenic pollution. Only a minority of the variation can be attributed to variations in the contributions from different upstream source areas. This variation represented by the third and higher components from the PCA can potentially be used for sediment provenance analysis.

23526. 题目: Impacts of anthropogenic forcing on source variability of sedimentary organic matter in the Yellow River estuary over the past 60 years
文章编号: N19121301
期刊: Marine Pollution Bulletin
作者: Rui Xiao, Xiuning Wu, Jinzhou Du, Bing Deng, Lei Xing
更新时间: 2019-12-13
摘要: To evaluate changes in the source of sedimentary organic matter (OM) in the Yellow River estuary, a sediment core collected in eastern Laizhou Bay was analyzed for total organic carbon (TOC), stable carbon isotopes of TOC, and biomarkers. The results showed a decreasing trend in terrestrial OM (TOM), but an increasing trend in marine OM (MOM) over the past 60 years. TOM was subdivided into soil OM and plant OM in a three end-member mixing model. The soil OM gradually decreased over the past 60 years, with a significant decline since the 1980s, while the plant OM gradually increased. This reveals that the reduction in TOM was caused mainly by the decreased input of soil OM. The reduced TOM contribution can be attributed primarily to dam construction and a decline in precipitation, whereas the elevated MOM contribution was caused by enhanced marine productivity driven by a rise in nutrient inputs.

23527. 题目: Fundamental drivers of dissolved organic matter composition across an Arctic effective precipitation gradient
文章编号: N19121212
期刊: Limnology and Oceanography
作者: Anne M. Kellerman, Ana Arellano, David C. Podgorski, Ellen E. Martin, Jonathan B. Martin, Kelly M. Deuerling, Thomas S. Bianchi, Robert G. M. Spencer
更新时间: 2019-12-12
摘要: The standard model for aquatic ecosystems is to link hydrologic connectivity to dissolved organic carbon (DOC) concentration and dissolved organic matter (DOM) composition and, ultimately, reactivity. Studies across effective precipitation gradients have been suggested as models for predicting how carbon cycling will change in Arctic aquatic ecosystems with projected drying (i.e., reduced hydrologic connectivity). To evaluate links between DOM dynamics and hydrologic connectivity, 41 stream samples from Greenland were analyzed across an effective precipitation gradient for DOM optical properties and elemental composition using ultrahigh‐resolution mass spectrometry. Sites with negative effective precipitation and decreased hydrologic connectivity exhibited elevated specific conductivity (SpC) and DOC concentrations as well as DOM composition indicative of decreased hydrologic connectivity, for example, lower aromaticity, assessed using carbon‐specific UV absorbance at 254 nm, decreased relative abundances of polyphenolic and condensed aromatic compounds, and increased relative abundances of highly unsaturated and phenolic compounds. Allochthonous inputs decreased as the summer progressed as exhibited by decreases in aromatic compounds. A decrease in molecular richness and N‐containing compounds coincided with the decrease in allochthonous inputs. DOC concentrations increased over the summer but more slowly than SpC, suggesting degradation processes outweighed combined evapoconcentration and production. The patterns in DOM composition suggest evapoconcentration and photodegradation are dominant controls. However, when hydrologic connectivity was high, regardless of effective precipitation, DOM reflected allochthonous sources such as snowmelt‐fed wetlands. These results highlight the challenges of modeling carbon cycling in aquatic ecosystems across effective precipitation gradients, particularly those with strong seasonality and regional variability in hydrologic inputs.

23528. 题目: Linking stream microbial community functional genes to dissolved organic matter and inorganic nutrients
文章编号: N19121211
期刊: Limnology and Oceanography
作者: Christina Fasching, Christian Akotoye, Mina Bižić, Jeremy Fonvielle, Danny Ionescu, Sabateeshan Mathavarajah, Luca Zoccarato, David A. Walsh, Hans‐Peter Grossart, Marguerite A. Xenopoulos
更新时间: 2019-12-12
摘要: There is now increasing evidence for the importance of microbial regulation of biogeochemical cycling in streams. Resource availability shapes microbial community structure, but less is known about how landscape‐mediated availability of nutrients and carbon can control microbial functions in streams. Using comparative metagenomics, we examined the relationship between microbial functional genes and composition of dissolved organic matter (DOM), nutrients, and suspended microbial communities in 11 streams, divided into three groups based on the predominant land cover category (agriculture, forested, or wetland). Using weighted gene co‐occurrence network analysis, we identified clusters of functions related to DOM composition, agricultural land use, and/or wetland and forest land cover. Wetland‐dominated streams were characterized by functions related to nitrogen metabolism and processing of aromatic carbon compounds, with strong positive correlations with dissolved organic carbon concentration and DOM aromaticity. Forested streams were characterized by metabolic functions related to monomer uptake and carbohydrates, such as mannose and fructose metabolism. In agricultural streams, microbial functions were correlated with more labile, protein‐like DOM, PO₄, and NO₃, likely reflecting functional adaptation to labile DOM and higher nutrient concentrations. Distinct changes in the functional composition and loss of functional diversity of microorganisms became evident when comparing natural to agricultural catchments. Although all streams showed signs of functional redundancy, loss of species richness per function in agricultural catchments suggests that microbial functions in natural catchments may be more resilient to disturbance. Our results provide new insight into microbial community functions involved in nutrient and carbon biogeochemical cycles and their dependence on specific environmental settings.

23529. 题目: Carbonization of Plant Residues Decreased their Capability of Reducing Hexavalent Chromium in Soils
文章编号: N19121210
期刊: Water, Air, & Soil Pollution
作者: Bo Li, Junxing Yang, Wentao Sun, Yibing Ma
更新时间: 2019-12-12
摘要: The mechanism of Cr(VI) immobilization in soils by organic substances are not well understood. In the present study, two crop residues (maize stalk and peanut shell) and their biochars obtained at various pyrolysis temperatures were prepared to investigate their influences on the immobilization of Cr(VI) in two contaminated soils via an incubation test and a bioassay. The results showed that Cr(VI) immobilization in soils was ascribed to dominant reduction (52–99%) coupled with secondary surface adsorption (1.2–48%) by organic substances. The maximum reduction capacity (Y_m, 238 mg/kg) was found in an acidic brown soil with maize stalk amendment, secondly, with peanut shell amendment (Y_m, 231 mg/kg). Their biochars presented a weaker capacity in reducing Cr(VI) to Cr(III) of soils than raw crop residues since carbonization accelerated the decomposition of oxygen-containing functional groups of organic substances. Soil properties, mainly soil pH, were negatively related to Cr(VI) reduction in soils remarkably, while concomitant anions in soils mainly the phosphate could compete with Cr(VI) for surfaces of soil particles and decrease Cr(VI) adsorption and subsequent reduction. The bioassay in pots with wheat seedlings further validated that maize stalk was a better organic substance for Cr(VI) immobilization and subsequent decrease of its bioavailability in contaminated soils than its biochar according to the results of wheat biomass and Cr contents in shoots and roots. Accordingly, to develop a cost-effective method for immobilizing Cr(VI) in contaminated soils, the raw maize stalk is more advantageous than the carbonaceous counterparts because no pyrolysis is required for the application.

23530. 题目: Biochar applied to consolidated land increased the quality of an acid surface soil and tobacco crop in Southern China
文章编号: N19121209
期刊: Journal of Soils and Sediments
作者: Jiuquan Zhang, Yilan Huang, Jianqi Lin, Xue Chen, Caibin Li, Jiguang Zhang
更新时间: 2019-12-12
摘要: Purpose: Soil needs to be ameliorated after land consolidation because this process might decrease soil fertility, soil physical properties, and the growth of microbes, and the application of biochar is one of the soil amelioration methods. However, up to date, no relevant study has been conducted by any field experiment. The objective of this study was to investigate the biochar effect on soil improvement and crop quality. Materials and methods: A field experiment with 5 corn stover biochar application rates (0, 1, 5, 10, 20 Mg ha⁻¹) was conducted in an acid soil (Kandiudult soil in US taxonomy) with flue-cured tobacco as representative crop. Results and discussion: The results showed that in comparison with 0 Mg ha⁻¹ biochar treatment, the application of biochar decreased the soil bulk density by 13.22%, increased the > 2-mm water-stable soil aggregates by 27.38%, and the 0.25 to 2.00-mm soil aggregates by 45.57% at most. The soil pH, organic carbon, labile organic carbon, and exchangeable Ca and Mg contents increased with increasing biochar application rate. The application of biochar was also beneficial for soil microbial activities. For example, the abundance of actinomyces increased with the biochar application rate, and the maximum increase of 342.28% was recorded at the biochar application rate of 20 Mg ha⁻¹. The application of biochar decreased the total sugar and reducing sugar contents and increased the leaf K content, thus greatly improving the leaf quality of flue-cured tobacco. Conclusions: Biochar applied to consolidated acid soil can play a positive role in flue-cured tobacco production and soil amelioration with regard to soil physical properties and soil nutrient supply capacity. On consolidated land, this is the first study about the effect of biochar application on quality of acid soil and crop, which strengthens the understanding about the role of biochar in soil improvement on consolidated land.

23531. 题目: Impacts of agricultural land use change on soil aggregate stability and physical protection of organic C
文章编号: N19121208
期刊: Science of The Total Environment
作者: Lingke Guo, Jie Shen, Bing Li, Qiquan Li, Changquan Wang, Yu Guan, Luigi P. D'Acqui, Youlin Luo, Qi Tao, Qiang Xu, Huanxiu Li, Juan Yang, Xiaoyan Tang
更新时间: 2019-12-12
摘要: Soil aggregate stability and soil organic carbon (SOC) physical sequestration is essential to regulation of anthropogenic climate change. However, relative knowledge remains elusive. The total SOC stock, aggregate stability, capacity of physically protected C, structure of macroaggregates and Al/Fe oxides under rice-wheat rotation (RW), rice-vegetable rotation (RV) and afforested land (AL) were analysed. We chose 1–2 mm macroaggregates for low-temperature ashing (LTA) treatment to mimic natural oxidation to assess the capacity of physically protected C. Using scanning electron microscopy, the N adsorption method, and energy dispersive spectroscopy, we explored the internal structure of macroaggregates under different land use types. All land use types could physically protect over 50% of SOC. AL showed the strongest capacity of C sequestration, followed by RW, which preserved 67.1% and 59.6% of SOC, respectively. After 5 h of LTA treatment, the amount of SOC removed from the macropores in cropland (RW and RV) was higher than that in AL. In micropores with further oxidation, AL and RW both lost only 5% of SOC. Fe oxides were more correlated with C dynamics than Al oxides. Free Fe oxides were associated with the easily oxidised organic matter. Soil aggregate stability significantly correlated with Al/Fe oxides (p < 0.05). The RW and AL had a greater soil aggregate stability than the RV owing to the relatively higher content of Al/Fe oxides. In conclusion, the conversion of RW to RV reduced the mechanical stability of soil aggregates and the capacity of C physical sequestration, while the conversion of RW to AL increased these two properties. Land use change affected C physical sequestration mainly via changes in surface area, pore development and the content of Fe oxides in macroaggregates.
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23532. 题目: Changing riverine organic C:N ratios along the Pearl River: Implications for estuarine and coastal carbon cycles
文章编号: N19121207
期刊: Science of The Total Environment
作者: Qinyu Liu, Yingtong Liang, Wei-Jun Cai, Kuo Wang, Juying Wang, Kedong Yin
更新时间: 2019-12-12
摘要: In the traditional view, riverine organic matter typically has a higher C:N ratio than marine phytoplankton 6.7:1 and has therefore been thought to be a carbon source in estuaries and coastal waters. Thus, a decrease in the riverine organic C:N ratio to <6.7:1 would potentially switch riverine organic matter from a coastal carbon source to sink. However, few studies have paid an attention to such a change. Our field investigation showed that organic C:N ratio was 11.8:1 in the pristine upstream section of a natural reserve, but decreased after the river passed through several urban cities, reaching 5.0:1 in near the Pearl River estuary. Along the river, dissolved inorganic nitrogen, total organic carbon and nitrogen all increased and they were highly negatively correlated with organic C:N ratios. The observation has a great implication that organic matter with a decreased C:N ratio from the Pearl River would potentially switch from a coastal carbon source of 2.8 × 10¹¹ g C/year to a sink of 2.2 × 10¹¹ g C/year. This carbon sink (2.2 × 10¹¹ g C/year) contributes to 56% of the previous estimate of the Pearl River estuarine-coastal net carbon sink. Such a decrease in organic C:N ratio also occurs in some other large rivers, which should be considered in the assessment of global coastal carbon budgets and metabolic balance.
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23533. 题目: Source apportionment of fine particulate matter in a Middle Eastern Metropolis, Tehran-Iran, using PMF with organic and inorganic markers
文章编号: N19121206
期刊: Science of The Total Environment
作者: Sepideh Esmaeilirad, Alexandra Lai, Gülcin Abbaszade, Jürgen Schnelle-Kreis, Ralf Zimmermann, Gaëlle Uzu, Kaspar Daellenbach, Francesco Canonaco, Hossein Hassankhany, Mohammad Arhami, Urs Baltensperger, André S.H. Prévôt, James J. Schauer, Jean-Luc Jaffrezo, Vahid Hosseini, Imad El Haddad
更新时间: 2019-12-12
摘要: With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM_2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM_2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical analysis of filter samples. The dominant mass components were organic matter (OM), sulfate and EC. With a 20% water-soluble organic carbon (WSOC) fraction, the predominance of primary anthropogenic sources (i.e. fossil fuel combustion) was anticipated. A positive matrix factorization (PMF) analysis using the ME-2 (Multilinear Engine-2) solver was then applied to this dataset. 5 factors were identified by Marker-PMF, named as traffic exhaust (TE), biomass burning (BB), industries (Ind.), nitrate-rich and sulfate-rich. Another 4 factors were identified by Metal-PMF, including, dust, vehicles (traffic non-exhaust, TNE), industries (Ind.) and heavy fuel combustion (HFC). Traffic exhaust was the dominant source with 44.5% contribution to total quantified PM_2.5 mass. Sulfate-rich (24.2%) and nitrate-rich (18.4%) factors were the next major contributing sources. Dust (4.4%) and biomass burning (6.7%) also had small contributions while the total share of all other factors was < 2%. Investigating the correlations of different factors between the two sampling sites showed that traffic emissions and biomass burning were local, whereas dust, heavy fuel combustion and industrial sources were regional. Results of this study indicate that gas- and particle-phase pollutants emitted from fossil fuel combustion (mobile and stationary) are the principal origin of both primary and secondary fine aerosols in Tehran.
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23534. 题目: Organic carbon stabilized by iron during slump deformation on the Qinghai-Tibetan Plateau
文章编号: N19121205
期刊: CATENA
作者: Cuicui Mu, Feng Zhang, Mei Mu, Xu Chen, Zhilong Li, Tingjun Zhang
更新时间: 2019-12-12
摘要: Soil organic carbon (SOC) associated with iron (Fe-OC) can be recognized as an important component of the stabilized carbon pool. In permafrost regions, slump deformation can expose soil organic carbon and alter moisture conditions, which change the Fe-OC distribution. We measured the top 30 cm of soils in five slump deformation landscapes under three vegetation types on the middle and eastern Qinghai-Tibetan Plateau. Three stages of slump deformation were defined according to their microtopography. In the slump deformation areas, the SOC and total nitrogen (TN) contents in the surface 30 cm of soils were all lower than the soils without slump deformation in wet meadow (22% and 26%), meadow (16% and 29%), and steppe (14% and 20%) areas. The contents of Fe-OC in wet meadow were 4.1% and 12.5% in the soils without and with slump deformation, respectively, whereas these contents in the meadow and steppe soils were 25.6% and 17.2%, respectively. Slump deformation greatly changed the physiochemical soil variables and affected the Fe-OC% based on different vegetation types. Fe-OC was correlated with factors such as soil moisture, pH and C/Fe ratio. The study shows that slump deformation greatly affected the SOC and TN distribution and SOC stabilization processes in areas with slump deformation features.

23535. 题目: Comparison of adsorption behavior studies of Cd²⁺ by vermicompost biochar and KMnO₄-modified vermicompost biochar
文章编号: N19121204
期刊: Journal of Environmental Management
作者: Jizhou Zhang, Xianfa Ma, Lei Yuan, Dongxing Zhou
更新时间: 2019-12-12
摘要: Cd²⁺ pollution in aquatic environments can pose a serious threat to human health. Biochar can remove Cd²⁺ from aquatic environments, but the Cd²⁺adsorption capacity of conventional biochar is low, therefore, we focused on exploring the Cd²⁺ adsorption capacity of modified biochar. In this study, KMnO₄ was used to modify vermicompost biochar (VBC), and static adsorption tests for Cd²⁺ were carried out. The biochar properties and its adsorption efficiency toward Cd²⁺ before and after modification were studied by kinetics and isotherm model fitting, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). Additionally, an adsorption mechanism was discussed. The results showed that the KMnO₄-modification resulted in a successful loading of the vermicompost biochar with MnO₂, which greatly improved its adsorption capacity for Cd²⁺. The adsorption of Cd²⁺ by VBC and MVBC was a spontaneous, endothermic, and monolayer chemical adsorption process. Mineral precipitation mechanism accounted for the largest proportion, and CdCO₃ was the main precipitate. After modification the proportion of surface precipitation and other mechanisms (π-electron coordination and the inner/outer sphere surface coordination) increased，while adsorption via cation exchange, oxygen-containing functional groups, physical adsorption and electrostatic attraction reduced. Hence, KMnO₄ modification has a significant effect on the Cd²⁺ adsorption behavior of vermicompost biochar.
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23536. 题目: In mitigating CO₂ emission in the reservoir riparian: The influences of land use and the dam-triggered flooding on soil respiration
文章编号: N19121203
期刊: Soil and Tillage Research
作者: Kai Zhu, Maohua Ma, Yiguo Ran, Zhimei Liu, Shengjun Wu, Ping Huang
更新时间: 2019-12-12
摘要: Soil respiration (SR) has been found to be highly influenced by land use and soil water regimes. However, the relative contribution of farming and dam-triggered flooding in influencing the SR of the riparian zone is poorly understood. The objectives of this study were to investigate the effects of land use and dam-triggered flooding intensity on SR in the riparian zone along the Three Gorges Reservoir (TGR), China, and to identify the main factors shaping the SR. At the Wuyang Bay of the Pengxi River, a tributary of the Yangtze River in the TGR, a series of SR field examinations in different land-use types and along elevation gradients in the riparian zone were carried out from March to September in 2018. During the study period, by analyzing SR in 177 m (elevation above sea level, the same as follows) unflooded site (UF), 173 m corn field (173C), 173 m paddy field (173 P), 168 m corn field (168C), 168 m paddy field (168 P), 168 m fallow grassland (168 F), 166 m fallow grassland (166 F), 163 m corn field (163C) and 163 m fallow grassland (163 F), significant differences in diurnal variations were found to be mainly affected by soil temperature (ST) at 10 cm depth, while seasonal variations were mainly regulated by ST and rainfall events (i.e. 10 cm depth soil water content). Importantly, croplands were found to contain higher soil organic carbon (SOC) but lower SR efflux and Q₁₀ values than those for non-cropping fields. The results imply that SR was strongly affected by land-use types rather than flooding intensity in the TGR riparian zone. Furthermore, this study highlights the significant impacts of tillage in stabilizing SOC and reducing SR efflux in the area that is highly influenced by hydrological regime shift. Finally, from the perspective of controlling the soil carbon dioxide emission, we suggest that local government should manage and guide farming activities in the riparian zone.

23537. 题目: The role of biochar in organic waste composting and soil improvement: A review
文章编号: N19121202
期刊: Waste Management
作者: Xiao-xia Guo, Hong-tao Liu, Jun Zhang
更新时间: 2019-12-12
摘要: Large amounts of organic wastes, which pose a severe threat to the environment, can be thermally pyrolyzed to produce biochar. Biochar has many potential uses owing to its unique physicochemical properties and attracts increasing attentions. Therefore, this review focuses on the agronomic functions of biochar used as compost additives and soil amendments. As a compost additive, biochar provides multiple benefits including improving composting performance and humification process, enhancing microbial activities, reducing greenhouse gas and NH₄ emissions, immobilizing heavy metals and organic pollutants. As a soil amendment, biochar shows a good performance in improving soil properties and plant growth, alleviating drought and salinity stresses, interacting with heavy metals and organic pollutants and changing their fate of being uptaken from soils to plants. Furthermore, combined application of biochar and compost shows a good performance and a high agricultural value when applied to soils. Objectively and undeniably, there are still negative or ineffective cases of biochar amendment on crop yield and heavy metal immobilization, which is worthy of further attention. The medium-long term field monitoring of biochar-specific agricultural functions, as well as the exploration of wider sources for biochar feedstocks, are still needed.
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23538. 题目: Influences of nitrogen addition and aboveground litter-input manipulations on soil respiration and biochemical properties in a subtropical forest
文章编号: N19121201
期刊: Soil Biology and Biochemistry
作者: Yong PENG, Si-yi SONG, Zeng-yan LI, Shun LI, Guan-tao CHEN, Hong-ling HU, Jiu-long XIE, Gang CHEN, Yin-long XIAO, Li LIU, Yi TANG, Li-hua TU
更新时间: 2019-12-12
摘要: Atmospheric nitrogen (N) deposition has rapidly increased in subtropical ecosystems and may have altered the input of aboveground litter to soil, which substantially impacts soil carbon (C) and nutrient cycling. But how the soil processes and properties respond to N deposition under uncertain fresh litter input is poorly understood. In order to examine the responses of soil respiration and biochemical properties to N addition and aboveground litter manipulation, a field N addition and litterfall manipulation interaction experiment was performed in an evergreen broadleaf forest on the western edge of the Sichuan Basin in China. Three levels of N addition, including an N control (CN, ambient N input) and low N (LN, + 50 kg N ha⁻¹ year⁻¹) and high N (HN, + 150 kg N ha⁻¹ year⁻¹), and three levels of litterfall manipulation, including intact litter input (L0, no litter alteration), litter reduction (L−, reduced by 50%) and litter addition (L+, increased by 50%), were conducted monthly starting in January 2014 and August 2015, respectively. Soil respiration was measured monthly from January 2016 to December 2017. Soil samples were collected four times, in October 2016 and January, April and July 2017, to measure soil biochemical properties. The results showed that: (1) short-term N addition did not significantly alter the aboveground litter input in this forest; (2) soil respiration decreased with elevating N input and was associated with amount of litterfall input; (3) N addition increased the total organic C (TOC) concentration in topsoil in subplots without litterfall alteration but did not affect TOC in subplots with increased or decreased litter-input; (4) N addition decreased soil pH and did not affect soil microbial biomass regardless of whether litterfall was altered or not; (5) short-term litter manipulation did not affect any soil properties in the N control plots, but both litterfall reduction and addition tended to reduce surface soil TOC concentration in the N-added plots; and (6) both N addition and litterfall manipulation showed stronger effects on organic soil than on mineral soil. These findings indicated that elevated N input increased the surface soil C content by reducing soil respiration mainly via enhancing stabilization of soil organic matter rather than by reducing soil microbial biomass, and that altered litterfall may mitigate the N-induced increase in soil C. Because of temporal lag, long-term experimentation is needed to investigate the response of soil to altered litter input under different N addition conditions.

23539. 题目: Depth is relative the importance of depth for transparent exopolymer particles in the near-surface environment
文章编号: N19121115
期刊: Ocean Science
作者: Tiera-Brandy Robinson, Christian Stolle, Oliver Wurl
更新时间: 2019-12-11
摘要: Transparent exopolymer particles (TEPs) are a major source for both organic matter (OM) and carbon transfer in the ocean and into the atmosphere. Consequently, understanding the vertical distribution of TEPs and the processes which impact their movement is important in understanding the OM and carbon pools on a larger scale. Additionally, most studies looking at the vertical profile of TEPs have focused on large depth scales from 5 to 1000 m and have omitted the near-surface environment. Results from a study of TEP enrichment in the sea surface microlayer (SML) in different regions (tropical, temperate) has shown that, while there is a correlation between TEP concentration and primary production (PP) on larger or seasonal scales, such relationships break down on shorter timescales and spatial scales. Using a novel small-scale vertical sampler, the vertical distribution of TEPs within the uppermost 2 m was investigated. For two regions with a total of 20 depth profiles, a maximum variance of TEP concentration of 1.39×106 µg XG eq2 L−2 between depths and a minimum variance of 6×102 µg XG eq2 L−2 was found. This shows that the vertical distribution of TEPs was both heterogeneous and homogeneous at times. Results from the enrichment of TEPs and Chl a between different regions have shown TEP enrichment in the SML to be greater in oligotrophic waters, when both Chl a and TEP concentrations were low, suggesting the importance of abiotic sources for the enrichment of TEPs in the SML. However, considering multiple additional parameters that were sampled, it is clear that no single parameter could be used as a proxy for TEP heterogeneity. Other probable biochemical drivers of TEP transport are discussed.

23540. 题目: Aeolian transport and deposition of carbonaceous aerosols over the Northwest Pacific Ocean in spring
文章编号: N19121114
期刊: Atmospheric Environment
作者: Zilan Wu, Limin Hu, Tianfeng Guo, Tian Lin, Zhigang Guo
更新时间: 2019-12-11
摘要: The present study provides insight into the long-range transport of carbonaceous aerosols over the Northwest Pacific Ocean (NWP) based on marine aerosol samples collected onboard a research vessel in the spring of 2015. Organic carbon (OC) and elemental carbon (EC) concentrations showed maxima in proximity to land, with high levels also observed in advective air masses. The decoupled spatial variations in OC and EC levels in relatively pristine air masses from the Pacific, in which aerosol n-alkanes of marine origin were relatively high in abundance, revealed the influence of heterogeneity in air masses and suggested the release of n-alkanes from local marine environments. This was confirmed by the enhanced particle-bound fraction of marine organic matter-sourced n-alkanes, resulting in non-significant relationships between the gas–particle partition coefficient of n-alkanes and the corresponding sub-cooled liquid vapor pressure in some marine air masses. High OC/EC ratios over the NWP indicated secondary organic aerosol formation, possibly as a result of marine emissions followed by gas-to-particle conversion and/or aerosol aging during long-range transport from East Asia. Similar molecular profiles of n-alkanes were found in air and seawater particles in regions dominated by either marine or continental influence, reflecting the strengths of continental and/or marine input and more importantly, suggesting the occurrence of air–sea exchange through wind-induced marine emissions or atmospheric deposition. Relative to the East China Sea, dry particle deposition after long-range transport acted as a more important source for terrestrial lipids in the open NWP.