21. 题目: Evaluation of the applicability of organic amendments from microbially driven carbon and nitrogen transformations
期刊: Science of The Total Environment
作者: Yajun Yang, Hexiang Liu, Jialong Lv
摘要: Pig manure (PM), wheat straw (WS), compost product (CP) and improved compost product (IC) are very important agricultural organic resources. In this study, their applicability as soil organic fertilizations (OFs) in terms of their properties and influence on soil properties through an incubation experiment and a field verification were evaluated. The property differences indicated that wheat straw has the highest C/N ratio, and compost products contain more aromatic compounds compared with pig manure and wheat straw. The results of incubation experiment showed that OFs promoted the carbon and nitrogen transformation driven by related microorganisms and their functional metabolisms. The PM treatment had the highest proportion of Labile organic carbon to soil organic carbon (LOC/SOC) and ratio of dissolved organic carbon to soil organic carbon (DOC/SOC), while WS treatment had the lowest values. The highest net N mineralization rate and nitrification rate was observed in the WS treatment, but the lowest amounts were under the PM treatment. Additionally, the similar findings were also obtained from the field examination. Therefore, compost products were more applicable in agricultural soil as OF insight from changes in carbon, nitrogen and microbial community. Furthermore, the result of UV-vision showed that the largest amount of aromatic structure was observed in IC relative to CP. It can be concluded that CP was more conducive to fix carbon and provide available nitrogen for crops among four OFs.
22. 题目: Organic Phosphorus Mineralization Dominates the Release of Internal Phosphorus in a Macrophyte-Dominated Eutrophication Lake
期刊: Frontiers in Environmental Science
作者: Wei Yu, Haiquan Yang, Jingan Chen, Peng Liao, Quan Chen, Yongqiong Yang, Yong Liu
摘要: Macrophyte-dominated eutrophication (MDE) lakes have attracted wide attention due to the high phosphorus (P) loading in sediments that poses a wide spread risk for P release and pollution management. However, because of the superior productivity characteristics, the role of organic P mineralization in sediments in the internal P loading of MDE lake is still under debate. This study investigated the release dynamic of P in the sediments of Lake Caohai, a MDE lake in southwest of China, using a combination of the modified Huffer sequential extraction method, 31 P nuclear magnetic resonance spectroscopy (NMR), and composite diffusive gradient in thin films (DGT) technology. Results showed that the apparent P diffusion flux at the sediment-water interface was remarkably high, with a mean value of 0.37 mg m −2 d −1 . The phosphate ester organophosphorus components (i.e., Mono-P and Diester-P) continuously deposited and degraded in the sediments maintained the high productivity of the lake, and the mineralization process plays a critical role in the release of internal P. Although the content of inorganic P in sediment is relatively high (accounting for approximately 60% of total P), the reductive mechanism based on P-containing iron oxide/hydroxide has a low contribution to the internal P loading, as was indicated by the low release rate of P-combination iron-manganese (Fe-Mn)/iron-aluminum (Fe-Al) (BD-P and NaOH-P) and the insignificant positive correlations between DGT-labile P and DGT-labile Fe in the sediment cores. Additionally, organic P in sediments could transfer to P-combination Fe-Al/Fe-Mn. However, in severely expropriated environments, the enrichment of P-combination Fe-Al/Fe-Mn in surface sediments inhibited the mineralization of monophosphate to some degree. Taken together, this study emphasized the impact of sediment organic P loading on the release of internal P in lake, highlighting that organic P is also the valuable objects for avoiding eutrophication of MDE lakes.
23. 题目: Biochar-supported starch/chitosan-stabilized nano-iron sulfide composites for the removal of lead ions and nitrogen from aqueous solutions
期刊: Bioresource Technology
作者: Hai Wang, Renrong Liu, Qian Chen, Yiwei Mo, Yaohong Zhang
摘要: Novel materials that nano-FeS and starch (or chitosan) loaded on peanut shells biochar(Starch-FeS@PSB and Chitosan-FeS@PSB) were prepared and applied for removal of Pb(II) and nitrogen(NO3-N and NH4-N) in wastewater. It showed that Starch-FeS@PSB and Chitosan-FeS@PSB had excellent absorptive effects compared with PSB. The maximum adsorption capacity of Pb(II) by Starch-FeS@PSB and Chitosan-FeS@PSB reached 90.15 mg/g, 96.15 mg/g, respectively. Absorption of Pb(II) by Starch-FeS@PSB and Chitosan-FeS@PSB were controlled by monolayer chemisorption. Mechanism studies showed that complexation, electrostatic attraction, REDOX and physical absorption happened on the adsorbent surface. In addition, the maximum adsorption capacity of NO3-N and NH4-N by Starch-FeS@PSB and Chitosan-FeS@PSB reached 16.89 mg/g, 15.65 mg/g, and 18.45 mg/g, 18.28 mg/g, respectively. Absorption of N by Starch-FeS@PSB and Chitosan-FeS@PSB were controlled by multilayer chemisorption. Mechanism studies showed that complexation, electrostatic attraction and physical absorption happened on the adsorbent surface. Starch-FeS@PSB and Chitosan-FeS@PSB can be utilized in Pb(II) and N wastewater treatment.
24. 题目: Impact of the initial hydrophilic ratio on black carbon aerosols in the Arctic
期刊: Science of The Total Environment
作者: Yunman Han, Bo Fu, Shu Tao, Dongqiang Zhu, Xuhui Wang, Shushi Peng, Bengang Li
摘要: Black carbon (BC) contributes to patterns of Arctic warming, yet the initial hydrophilic ratio (IHR) of BC emitted from various sources and its impact on Arctic BC remain uncertain. With the use of a tagged tracer method of BC implemented in the global chemistry transport model GEOS-Chem, IHRs were partitioned into 7 BC combustion source categories according to the PKU-BC-v2 emission inventory. The results show that as the IHR increased, the concentration of BC decreased globally. The impact on Arctic BC was mainly reflected in the vertical profile and the burden rather than at the surface. Specifically, the greatest impact of IHR on Arctic BC appeared in summer, with the largest perturbation appearing at an altitude of approximately 600 hPa, reaching 8%. This change in BC vertical profile was mainly caused by the IHR change of wildfire combustion in Russia (44%) and Canada (51%), and the emissions from these two regions were also the two most important contributors to the BC concentration and burden in the middle and lower Arctic atmosphere in summer. In the other three seasons, anthropogenic combustion sources (oil, coal, and biomass) in East Asia, Russia, and Europe accounted for 19–40%, 14–28%, and 7–23%, respectively, of the monthly BC burden. Emissions from Russia were the most important contributor (27–43%) to the monthly BC surface concentration. Due to the large adjustment in IHR from 20% to 70%, biomass burning in Europe was shown to be the dominant contributor causing both burden (39%) and surface concentration (88%) changes in all seasons except summer.
25. 题目: Changes in soil organic carbon and nitrogen pool sizes, dynamics, and biochemical stability during ∼160 years natural vegetation restoration on the Loess Plateau, China
作者: Di Zhang, Xinwen Cai, Longfei Diao, Yaqi Wang, Jinsong Wang, Shuqing An, Xiaoli Cheng, Wen Yang
摘要: Natural vegetation restoration has been reported as an effective strategy for the enhancement of soil organic carbon (SOC) and nitrogen (SON) sequestration in degraded ecosystems. However, changes in SOC and SON pool sizes, dynamics, and biochemical stability to natural vegetation restoration remain inadequately addressed. For this study, we investigated carbon (C) and nitrogen (N) contents and δ13C and δ15N values of SOC and SON pools, their labile C and N (LSOC and LSON, respectively), and recalcitrant C and N (RSOC and RSON, respectively) along 0–60 cm soil depths spanning ∼160 years of natural vegetation restoration on the Loess Plateau, China. Our results revealed that natural vegetation restoration greatly enhanced SOC, SON, LSOC, LSON, RSOC, total N, water-soluble organic C, and mineralizable organic C in the topsoil (0–20 cm), while it had little influence on the deeper soil layers (20–60 cm). The concentrations and stocks of SOC and SON in the topsoil increased significantly during the later restoration stages. The recalcitrant index for C at the 0–40 cm soil depths was highest in climax Quercus liaotungensis forest, while the recalcitrant index for N was unchanged at 0–20 and 40–60 cm soil depths between vegetation restoration stages. The δ13C values of SOC, LSOC, and RSOC, and δ15N values of SON and LSON were more enriched in the deeper soil layers relative to the topsoil, for the majority of restoration stages. The δ15N values of SON, LSON, and RSON in the topsoil were more enriched during the early restoration stages compared to the later restoration stages. Our results suggested that long-term natural vegetation restoration enhanced SOC and SON sequestration, increased biochemical stability of SOC, altered the dynamics of SOC and SON in the topsoil of degraded ecosystems through the increased inputs of plant residuals, and reduced the decomposition soil organic matter.
26. 题目: New insights into the cooperative adsorption behavior of Cr(VI) and humic acid in water by powdered activated carbon
期刊: Science of The Total Environment
作者: Yanan Chen, Yunkun Qian, Jiaxin Ma, Mengjun Mao, Linping Qian, Dong An
摘要: Chromium and humic acid often co-exist in wastewater and source waters, and the removal of chromium through sorption by activated carbon may be greatly influenced by humic acid. In this study, we systematically evaluated concurrent adsorption of humic acid (HA) and hexavalent chromium (Cr(VI)) in water by powdered activated carbon (PAC) and further, the effect on conversion to trivalent chromium (Cr(III)). Adsorption of both HA and Cr(VI) was significantly enhanced in the dual adsorbate system as compared to treatments with HA or Cr(VI) alone. The removal of HA increased by 16.0% in the presence of 80 mg/L Cr(VI), while the removal of Cr(VI) similarly increased with increasing levels of HA. However, the promotion effect of HA was found to decrease with increasing pH. With HA at 20 mg/L, removal of Cr(VI) increased from 40.09% to 70.12% at pH 3, which was about twice the increase at pH 10. The cooperative adsorption mechanism was explored using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). Comprehensive analysis of spectra suggested that the mutual promotion between HA and Cr(VI) adsorption was attributable to the formation of Cr(VI)-HA and Cr(III)-HA complexes that were readily adsorbed on the PAC surfaces. The higher HA concentrations increased the reduction of Cr(VI) to Cr(III), which was likely due to the electron transfer provided by the functional groups such as -CO, -OH and -COOH in both PAC and HA. At pH 3, 99.1% of Cr adsorbed on the PAC surface was in the form of Cr(III). These findings imply that the interactions between Cr(VI) and HA in the process of water treatment by PAC provides additional and synergistic benefits, leading to a greater removal of chromium.
27. 题目: Insight into the role of different extracellular polymeric substances components on trimethoprim adsorption by activated sludge
期刊: Journal of Environmental Management
作者: You Ma, Pei-Kun Yuan, Yu Wu, Han Meng, Guo-Xiang Wang, Wen-Ming Xie, Li-Min Zhang, Jie Ma, Yan Xiao
摘要: Adsorption is the primary mechanism of antibiotic removal in wastewater treatment plants, wherein the extracellular polymeric substances (EPS) of the activated sludge play an important role. Due to their complex characteristics, the effect of EPS components on antibiotic adsorption is unknown. Therefore, in this study, the role of main components of EPS in antibiotic adsorption was explored using enzymatic treatment. The results revealed that proteinase K and α-amylase can efficiently hydrolyse the proteins and polysaccharides of EPS. The protein content of EPS reduced from 31.25 mg/g VSS to 21.53, 18.75, and 10.76 mg/g VSS, after treatment with proteinase K, α-amylase and their combination, respectively; the polysaccharides content also observed a similar decrease from 15.20 mg/g VSS to 8.22, 7.83, and 6.03 mg/g VSS, respectively. The humic substance in EPS was stable during enzymatic treatment. The equilibrium adsorption capacity of activated sludge treated by enzyme for trimethoprim (TMP)- a typical antibiotic, was significantly increased from 2.19 μg/g VSS to 4.68, 5.34, and 8.36 μg/g VSS after treatment with proteinase K, α-amylase and their mixture. The adsorption process was adequately described by pseudo-second-order kinetic model. A multivariable linear regression model was subsequently used to quantify the adsorption capacity of activated sludge for TMP considering the concentration of EPS components. The modelling and validated results showed that the model could satisfactorily predict the TMP adsorption capacity. The results of this study can provide new insights into the role of EPS on antibiotic transformation in biological wastewater treatment systems.
28. 题目: Improvement in the physicochemical characteristics of biochar derived from solid digestate of food waste with different moisture contents
期刊: Science of The Total Environment
作者: Ning Wang, Qindong Chen, Chao Zhang, Zihang Dong, Qiyong Xu
摘要: The management of digestate from food waste (DFW) has become a worldwide challenge. Pyrolysis is a promising technology to generate biochar from the DFW. However, unlike other biomass, DFW usually has high salt and moisture content, which affects the properties of biochar generated from pyrolysis. The characteristics of biochar derived from DFW with different MCs (5%, 20%, 40%, and 60%) were investigated in the present study. It was found that more micropore and mesopore structures were generated in the biochar with the increase of MC from 5% to 60%, resulting in the Brunauer–Emmett–Teller surface area of the biochar increased from 89.23 m2 g−1 to 117.75 m2 g−1. The MC could also promote the variation of oxygen-containing functional groups and the generation of amorphous carbon structures, which are beneficial for the adsorption property of the biochar. Pyrolysis could stabilize the metals in the biochar, while MC has little effect on the metal speciations. These results provide fundamental information on the impact of MC on the properties of biochar derived from DFW and are important for the optimization of the pre-drying process.
29. 题目: “Humic substances” measurement in sludge dissolved organic matter: A critical assessment of current methods
作者: Keke Xiao, Harald Horn, Gudrun Abbt-Braun
摘要: The role of humic substances (HS) during sludge treatment has been the focus in recent years. Quantification of HS in sludge dissolved organic matter (DOM) and the chemical and structural characterization of HS data are the prerequisite for understanding their role during different sludge treatment processes. Currently, a number of published articles inadequately acknowledge fundamental principles of analysis methods both in terms of experimental approach and data analysis. Therefore, a more comprehensive and detailed description of the experimental methods and the data analysis are needed. In this study, the current used methods for HS quantification in DOM of sludge had been tested for different calibration and sludge DOM samples. The results indicated that the current methods showed overestimated and contradictory results for HS quantification in sludge DOM. To be specific, using the modified Lowry method, different values were obtained depending on the humic acids used for calibration, and false negative results were observed for some sludge samples. By using the relative amount of HS (based on dissolved organic carbon (DOC)) to total sludge DOM (based on DOC), variations among the results of different analysis methods for the same sample were high. According to the calculated Bray-Curtis dissimilarity indexes, the results for HS quantification obtained by three-dimensional excitation emission matrix (3D-EEM), either with spectra analysis methods by peak picking, fluorescence region integration (both region volume and area integration), or PARAllel FACtor analysis showed higher degrees of dissimilarity to those quantified by size exclusion liquid chromatography or XAD-8 method. The selection of fluorescence regions for HS seemed to be the determining factor for overestimation obtained by the 3D-EEM technique. In future work, strategies, like a consistent terminology of HS, the use of an internal standard sample, and the related standardized operation for HS quantification in sludge DOM need to be established.
30. 题目: Prior nitrogen fertilization stimulated N2O emission from rice cultivation season under a rapeseed-rice production system
期刊: Plant and Soil
作者: Peng Xu, Mengdie Jiang, Yanbin Jiang, Imran Khan, Wei Zhou, Hongtao Wu, Xian Wu, Muhammad Shaaban, Jianwei Lu, Ronggui Hu
摘要: Aims Nitrogenous fertilizer has been recognized as a key factor regulating nitrous oxide (N2O) emissions from agricultural soils. However, the effect of nitrogen (N) fertilization of preceding season on soil N2O emission in subsequent season remain poorly understood. Methods Herein, a field-based study was done to examine the effect of prior N fertilization on N2O emissions under a rapeseed-rice rotation (RR) system in central China. Treatments were as follows: no N fertilizer was applied in both rapeseed and rice-growing seasons (N0-0), N fertilizer (150 kg N ha−1 y−1) was only applied during rapeseed-growing season (N150-0,), N fertilizer (150 kg N ha−1 y−1) was applied in both rapeseed and rice-growing seasons (N150-150), and N fertilizer (150 kg N ha−1 y−1) was only applied during rice-growing season (N0-150). Soil N2O fluxes and the key soil factors (soil available C and N and their ratios, soil temperature and moisture) that further drive N2O emissions were determined after N fertilization in preceding and subsequent seasons. Results The application of N fertilizer during the rapeseed-growing season caused a significant increase in soil N2O emission from rice-growing season, but no such promotion effect was observed during rapeseed growing season due to N fertilization during prior rice season. Higher N2O emission from rapeseed-growing season, after N fertilization was attributed to high soil mineral nitrogen content (including NH4+-N and NO3−-N). N2O efflux was higher when dissolved organic carbon (DOC) to NO3− content ratio (DOC/NO3−) was < 0.5 but lower when DOC/NO3− ratio was > 0.5 for both N150-0 and N150-150 treatments. Pulse N2O emission during the rice-growing period was observed due to higher soil DOC content derived from soil organic matter decomposition. The positive correlation between soil N2O fluxes and DOC/NO3− ratio for both N150-150 and N0-150, also revealed that soil available carbon to nitrogen ratio could be a crucial factor regulating peaks of N2O during the rice season. Structural equation model (SEM) displayed the explanation of impact factors on N2O emission was 62% during the rapeseed-growing season, while that explanation was 45% during the rice-growing season. Conclusions These results showed that not only labile C and N content, but also soil DOC/NO3−, influenced by prior N fertilization, play a key role in soil N2O emissions under the RR system.
31. 题目: Association of Organic Carbon with Reactive Iron Oxides Driven by Soil pH at the Global Scale
期刊: Global Biogeochemical Cycles
作者: Chenglong Ye, Wenjuan Huang, Steven J. Hall, Shuijin Hu
摘要: Association of organic carbon (C) with iron (Fe) minerals is one important mechanism for long-term terrestrial C storage. Yet, specific edaphic variables that directly contribute to Fe-associated C across diverse soil types are still unclear. Through analyzing soils from the National Ecological Observatory Network (NEON) and other published data, here we show that soil pH primarily controls Fe-associated C across the globe. Fe-associated C in most soils ranged from 0 to 20 g kg-1 soil, with a strong increase from pH 4.2 to 3.5, but a small change in soils with pH > 4.2. A microcosm experiment further showed that raising soil pH by liming reduced the formation of Fe-associated C in an acidic Oxisol. Together, these findings demonstrate the dominant role of soil pH in controlling the abundance of Fe-associated C.
32. 题目: Unrevealing the role of in-situ Fe(II)/S2O82- oxidation in sludge solid-liquid separation and membrane fouling behaviors of membrane bioreactor (MBR)
期刊: Chemical Engineering Journal
作者: Xueqin Lu, Jianhui Wang, Yule Han, Yan Zhou, Yenan Song, Ke Dong, Guangyin Zhen
摘要: Membrane bioreactor (MBR) has received continuous attention in waste activated sludge (WAS) treatment, however, membrane fouling still remains a big and inevitable challenge to its wide applications. Ferrous-persulfate (Fe(II)/S2O82–) oxidation possesses the outstanding oxidizing capability and high-efficiency in degrading refractory organics and enhancing sludge solubilization. In this study, in-situ Fe(II)/S2O82- oxidation was coupled for pretreating sludge, and the effect on the subsequent filtration performance and membrane fouling behaviors in MBR was investigated. Fe(II)/S2O82- oxidation had an outstanding effect on enhancing filterability of mixed sludge liquor and alleviating membrane fouling. Under the optimal pretreatment condition of 1.5/1.2 mmol-Fe(II)-S2O82-/g-VS, the membrane flux of reactor reached 20.6 mL/s/m2, and a 46.6% decrease in trans-membrane pressure (TMP) was obtained compared to the raw sludge without pretreatment. Correlation analysis reveal that polysaccharides in extracellular polymeric substances was the decisive factor affecting the membrane fouling behavior. The strong oxidizing ability of in-situ Fe(II)/S2O82- pretreatment could effectively break the glutinous and pilotaxitic biopolymer matrix deposited on the membrane surface, and rupture the hydrophilic bonds of proteins and polysaccharides. The high molecular weight biopolymers were brought down, with the water bounded inside the flocs released into liquid phase. Iron-mediated coagulation was also conductive to the re-aggregation of the fine particles and subsequent membrane fouling control. For raw WAS, the predominated fouling mechanisms were intermediate pore blocking and cake layer formation, while complete pore blocking and standard pore blocking occurred more frequently for pretreated WAS. This work provides a promising approach based on Fe(II)/S2O82- oxidation processes for efficient abatement of membrane fouling and sludge treatment.
33. 题目: Regrowth potential of chlorine-resistant bacteria in drinking water under chloramination
期刊: Journal of Hazardous Materials
作者: Xiaofei Wu, Jun Nan, Jimin Shen, Jing Kang, Dapeng Li, Pengwei Yan, Weiqiang Wang, Binyuan Wang, Shengxin Zhao, Zhonglin Chen
摘要: The regrowth of chlorine-resistant bacteria in drinking water can deteriorate water quality. The study evaluated the relationship between organic carbon and the regrowth potential of chlorine-resistant bacteria remaining in chloraminated water samples. The results showed that the community structure of bacteria changed with the increase of chloramine dosage. The order in which organic carbon utilized by bacteria was affected by the composition of bacterial community. The biodegradable dissolved organic carbon (BDOC), assimilable organic carbon (AOC), bacterial regrowth potential (BRP) and total cell concentration (TCC) in cultivated water sample after disinfection with 1.8mg/L chloramine increased form 0.22mg/L, 33.68µg/L, 2.70 × 105 cells/mL and 3.48 × 104 cells/mL before cultivation to 1.20mg/L, 193.90µg/L, 4.74 × 105 cells/mL and 1.46 × 105 cells/mL, respectively. The increase of TCC did not result in the decrease of BDOC, AOC and BRP in the cultivated water samples. The results showed that other biodegradable organic carbon in chloraminated water samples assimilated by residual chlorine-resistant bacteria besides AOC, BDOC, and organic carbon assimilated by indigenous bacteria. AOC, BDOC, and BRP indicators used to characterize the biostability of drinking water were not enough to accurately assess the regrowth potential of chlorine-resistant bacteria remaining in drinking water. It is suggested to supplement the index of TCC in cultivated water samples, which might be able to more accurately evaluate the regrowth potential of chlorine-resistant bacteria remaining in drinking water.
34. 题目: Cu–Fe–FeC3@nitrogen-doped biochar microsphere catalyst derived from CuFe2O4@chitosan for the efficient removal of amoxicillin through the heterogeneous electro-Fenton process
期刊: Chemical Engineering Journal
作者: Haiqiang Qi, Guifang Pan, XueLin Shi, Zhirong Sun
摘要: The heterogeneous electro-Fenton (hetero-EF) technology is an attractive but challenging method used to degrade organic pollutants. The development of a catalysts for the stable and efficient degradation of pollutants under neutral conditions remains a challenging task. In this study, a microsphere catalyst consisting of magnetic Cu–Fe–FeC3 on nitrogen-doped biochar (Cu–Fe–Fe3C@NDB) was prepared using chitosan (CS) as the carrier material in a two-step process. A hetero-EF system using Cu–Fe–Fe3C@NDB as the catalyst was constructed to efficiently degrade amoxicillin (AMX). The catalyst exhibited a wide pH application range, a good stability, and a low metal ion leaching. The main reasons behind the remarkable catalytic performance and excellent stability of the Cu–Fe–Fe3C@NDB catalyst are: (i) The presence of a core–shell structure, in which Cu–Fe bimetallic particles are wrapped in the structure of biomass carbon to slow down the loss of the metal active component in the catalyst and maintain its stability; (ii) The uniform dispersion of nanoparticles on the surface of the Cu–Fe–Fe3C@NDB catalyst, N-doped carbon, and the combined effect of Cu and Fe, which are beneficial to improve the charge transfer efficiency and regulate the electronic structure, which in turns improve the activity of the catalyst. This work demonstrates that the efficient degradation of pollutants under neutral conditions can be achieved and provides useful information for the design and synthesis of efficient and stable catalysts in hetero-EF reaction systems.
35. 题目: Vertical migration of cesium in weathered granite soil under flowing water condition depending on Cs concentration and states of dissolved organic matter
期刊: Journal of Environmental Management
作者: Takahiro Tatsuno, Shoichiro Hamamoto, Naoto Nihei, Taku Nishimura
摘要: After the accident at the Fukushima Daiichi nuclear power plant in Japan, the migration of radioactive cesium (Cs) in soils has become a crucial issue since this can negatively affect human health and the surrounding environment. Dissolved organic matter (DOM) may have different influences on Cs migration in soils depending on Cs adsorption sites with different selectivity. It is unclear how DOM affects the rapid migration of Cs in soils under flowing water conditions during rainfall events. This study evaluated the effects of DOM on Cs migration in weathered granite soil depending on Cs adsorption sites by conducting laboratory experiments under different DOM conditions and Cs concentrations in the liquid phase. Cs concentration can affect the fraction of Cs adsorbed onto differently selective sites, and DOM can have different influences on Cs migration in the soil accordingly. Under condition of high-Cs concentration, the DOM adsorbed on the soil reduced Cs migration due to increasing Cs electrostatic adsorption to less selective sites in the soil. Meanwhile, under low-Cs concentration, the DOM adsorbed on the soil enhanced Cs migration because the DOM on the soil decreased the Cs adsorption to highly selective sites. Furthermore, DOM in the liquid phase detached the Cs adsorbed on the less selective sites and enhanced Cs migration in the soil, regardless of the Cs concentration.
36. 题目: Effects of recovery models on organic carbon pathways: A method using 13C natural abundance
期刊: Agriculture, Ecosystems & Environment
作者: Jinjin Xiao, Yunfei Zhao, Xia Wang, Zhiguo Hao, Kaichang Wang, Silong Jiang, Huiying Liu, Xiaohe Zhou
摘要: The rehabilitation of disaster-prone areas can enhance the stability of soil structure and is a common way to increase organic carbon storage. The response of soil carbon sequestration pathways to different recovery modes is not clear, especially in mountain soils. After 11 years of recovery, we evaluated soil organic carbon (SOC) sequestration pathways in plantations (dominated by Olea europaea ‘Leccino’), croplands [Zea mays (L.)] natural shrublands (Lycium chinense Mill), and natural grasslands [Setaria viridis (L.) Beauv]. The physical and chemical properties of the soil and the 13C natural abundance of each aggregate and its density components were studied. The results showed that, during the restoration process, the soil organic carbon content of natural grassland increased the most, while the δ13C value of soil of natural shrubs was the highest. The natural abundance of 13C was used to reveal the pathway of C flow in soil organic matter (SOM), as follows: free light fractions (ρ < 1.6 g cm−3)→mineral fractions (ρ > 2.0 g cm−3)→dense occluded fractions (ρ from 1.6 to 2.0 g cm−3) (in plantation, natural shrubland, and grassland). However, in cropland soil, C flowed as follows: mineral fractions→free light fractions→dense occluded fractions. Specifically, the SOC content decreased with aggregate particle size, and after entering the soil, plant litter was first stored in large aggregates and then decomposed into the free light fraction. The study revealed the mechanism of organic carbon sequestration in the restoration area, emphasizing that artificial restoration treatment can change the carbon conversion pathway, and reduced the sequestration of organic carbon.
37. 题目: Dam cascade unveils sediment methylmercury dynamics in reservoirs
期刊: Water Research
作者: Honghai Ma, Yuchen Chen, Qiuwen Chen, Dongsheng Liu, Jianyun Zhang, Daniele Tonina
摘要: Methylmercury (MeHg) can be bioaccumulated through food chains and adversely affect human health. Reservoirs are reported to stimulate MeHg production, however, the characteristics of MeHg dynamics in cascade reservoirs and the associated relations to sedimentation as well as reservoir properties remained unclear. Here we investigated sediment MeHg dynamics in eight cascade reservoirs in the upper Mekong River. We found significant differences in sediment MeHg concentration between the reservoirs, showing an increase with fluctuations along the reservoirs cascade. However, a novel relationship was found between sediment %MeHg (MeHg/Hg) and the ratio of reservoir hydraulic residence time (HRT) to reservoir age. This relationship is formed by the joint effects of the original deposit of Hg and organic carbon (OC) before impoundment and the subsequent sedimentation of Hg and OC after impoundment. The original deposit is continuously transformed as the reservoir ages, whereas the latter is driven by the annual hydrological cycle and HRT, of which the HRT is dominant. This finding cannot be easily revealed in a single reservoir or by comparing multiple reservoirs in different rivers. The discovery is of great significance to understand Hg geochemical cycling in reservoirs, which is quickly increasing in rivers worldwide.
38. 题目: How to estimate soil organic carbon stocks of agricultural fields? perspectives using ex-ante evaluation
作者: Eric Potash, Kaiyu Guan, Andrew Margenot, DoKyoung Lee, Evan DeLucia, Sheng Wang, Chunhwa Jang
摘要: Estimating soil organic carbon (SOC) stocks of agricultural fields has a range of important applications from development of sustainable management practices to monitoring carbon stocks. There are many estimation strategies with the potential for more reliable estimates of SOC stock and more efficient use of soil sampling and analysis resources, especially by leveraging readily available auxiliary information such as remote sensing. However, concrete guidance for strategy selection is lacking. This study narrows this gap with a comparison of strategies for estimating deep SOC stock (0–60 cm) in a prototypical field. Using high density SOC stock measurements and simulation, we built on past studies by 1) ex-ante evaluating a large number of strategy options, 2) using a Bayesian approach to quantify the uncertainty of the comparison, and 3) considering multiple Bayesian models to assess sensitivity to this modeling choice. We found that, using readily available auxiliary information, both balanced and stratified sampling offer substantial improvements over simple random sampling. The auxiliary information most important for this improvement is a Sentinel-2 SOC index = blue / (green × red), followed by the topographic wetness index. We found that these results are robust to the choice of mapping method, but that there is uncertainty in the magnitude of improvement. We recommend future studies implement this Bayesian approach for simulated ex-ante evaluation of SOC stock estimation strategies across more fields to investigate the generalizability of these findings.
39. 题目: Bacteriohopanetetrol-<i>x</i>: constraining its application as a lipid biomarker for marine anammox using the water column oxygen gradient of the Benguela upwelling system
作者: Zoë R. van Kemenade, Laura Villanueva, Ellen C. Hopmans, Peter Kraal, Harry J. Witte, Jaap S. Sinninghe Damsté, Darci Rush
摘要: 50 µmol L−1, the BHT-x ratio was 0.04) were also detected in oxygenated offshore waters ([O2] up to 180 µmol L−1), whereas ladderane IPLs were undetected. The index of ladderane lipids with five cyclobutane rings (NL5) correlates with in situ temperature. NL5-derived temperatures suggested that ladderane FAs in the offshore waters were not synthesized in situ but were transported down-slope from warmer shelf waters. Thus, in sedimentary archives of systems with known lateral organic matter transport, such as the BUS, relative BHT and BHT-x abundances should be carefully considered. In such systems, a higher BHT-x ratio may act as a safer threshold for deoxygenation and/or Ca. Scalindua presence: our results and previous studies indicate that a BHT-x ratio of ≥ 0.2 is a robust threshold for oxygen-depleted waters ([O2]
40. 题目: Removal of fluconazole from aqueous solution by magnetic biochar treated by ball milling: adsorption performance and mechanism
期刊: Environmental Science and Pollution Research
作者: Zhexi Huang, Yunqiang Yi, Nuanqin Zhang, Pokeung Eric Tsang, Zhanqiang Fang
摘要: The problem of low adsorption capacity of pristine magnetic biochar for organic pollutants always occurs. It is of great significance to select a suitable method to improve the adsorption performance of magnetic biochar. In this study, magnetic biochar was treated by ball milling and tested for its fluconazole adsorption capacity. The maximum adsorption capacity of ball-milled magnetic biochar (BMBC) for fluconazole reached nearly 15.90 mg/g, which was approximately five times higher than that of pristine magnetic biochar (MBC). Fluconazole adsorption by BMBC was mainly attributed to π–π interactions, hydrogen bonding, and surface complexation with oxygen-containing functional groups. The enhancement in fluconazole adsorption by BMBC was attributed to an increase in oxygen-containing functional groups. Batch adsorption experiments also illustrated that BMBC could be successfully applied in a wide range of pH values. The high efficiency of fluconazole removal confirmed that ball milling was an effective strategy to enhance the adsorptive performance of magnetic biochar.