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23421. 题目: Effect of two organic amendments on atrazine degradation and microorganisms in soil
文章编号: N20030113
期刊: Applied Soil Ecology
作者: He Huang, Chaolan Zhang, Qun Rong, Chuangzhang Li, Jun Mao, Yu Liu, Junxian Chen, Xutong Liu
更新时间: 2020-03-01
摘要: Silkworm excrement and silkworm excrement derived biochar were added to both sterilized and unsterilized soil at rates of 0 and 0.5% (w/w). The effects of the two organic amendments on atrazine degradation and the microbial community in soils with an atrazine content of 5 mg·kg−1 were studied. In unsterilized soils, the residual fraction of atrazine at 56 d was increased in the silkworm excrement- and biochar-amended soils, by 2.18 mg·kg−1 and 0.72 mg·kg−1, respectively. Furthermore, both organic amendments increased the accumulation of desethylatrazine (DEA). However, unlike DEA, deisopropylatrazine (DIA) accumulation increased in silkworm excrement-amended soil and decreased in biochar-amended soil. There was a negative relationship between the depletion rate of DOC and the degradation rate of atrazine. With respect to microorganisms, the Biolog Ecoplate test revealed that biochar and silkworm excrement improved microbial activity and community diversity in atrazine-contaminated soil. Additionally, Illumina-MiSeq analyses showed that both organic amendments increased the proportions of Proteobacteria, Actinobacteria, Aspergillus and Cephalothecaceae in soil but decreased that of Bacteroidetes and Talaromyces.

23422. 题目: Foliage C:N ratio, stage of organic matter decomposition and interaction with soil affect microbial respiration and its response to C and N addition more than C:N changes during decomposition
文章编号: N20030112
期刊: Applied Soil Ecology
作者: Veronika Jílková, Petra Straková, Jan Frouz
更新时间: 2020-03-01
摘要: How litter at various stages of decomposition reacts to C and N additions is unclear. Here we used five substrates (litter, fermentation [Oe] layer, bulk soil, and the light fraction [LF] and heavy fraction [HF] of SOM) obtained from sites supporting five plant monocultures (Alnus glutinosa, Quercus robur, Salix caprea, Calamagrostis epigejos, or Picea omorica) with foliage C:N ratios ranging from 17 to 48. These plant-specific communities were experimentally planted on a post-mining heap and had affected the substrates used in this study for 40 years. Soils and other environmental factors were similar among the sites. Substrates were incubated for 3 weeks without nutrient addition or with C (glucose) or N (ammonium nitrate) addition, and microbial respiration was determined weekly. Substrate C:N ratios were determined at the start of the incubation and were highest for litter followed by Oe layer > LF > bulk soil and HF. Foliage C:N ratio was a better indicator of microbial respiration than the substrate C:N ratio, suggesting that the foliage C:N ratio reflected unmeasured leaf properties that determined microbial respiration. Respiration was highest in the litter followed by Oe layer > bulk soil > LF > HF. C addition increased respiration of the bulk soil (+39%), LF (+48%), and HF (+72%). Priming of SOM respiration was therefore higher in substrates with less available C. N significantly increased respiration of litter (+19%) but decreased respiration of bulk soil (−18%). The difference in respiration of HF vs. bulk soil following N addition suggested that, in addition to the stage of decomposition, environmental properties present in bulk soil but absent in HF may cause the reduction in respiration after N addition to bulk soil. Overall, the results indicate that differences in the contents of SOM fractions among soils will affect the responses of those soils to C and N additions.

23423. 题目: Spectroscopic studies on the phosphorus adsorption in salt-affected soils with or without nano-biochar additions
文章编号: N20030111
期刊: Environmental Research
作者: Esawy Mahmoud, Ahmed El Baroudy, Nehal Ali, Mahmoud Sleem
更新时间: 2020-03-01
摘要: Biochar amendment may be an effective solution of maintaining phosphorus (P) and sustaining agricultural production in salt affected soils. However, the behavior of P adsorption in salt-affected soils with nano-biochar (nB) amendment is unclear. Batch adsorption experiments were conducted to investigate the impacts of different levels of soil salinity amended with nB at rates of 0, 0.10%, 0.20%, and 0.50% (w/w) on the P adsorption isotherm and also, mechanisms of P adsorption by using spectroscopic analysis. The results showed that P adsorption increased with increasing soil salinity with or without nB addition. Under level of 120 mg P L−1, adsorption capacity of P increased from 992.8 mg kg−1 for high saline soil (S5) to 1144.0 mg kg−1 after treated with 0.20% nB. The results of P adsorption were agreed with Langmuir and Freundlich isotherm models. Fourier transform infrared analysis (FTIR) of nB showed that the surface of nB decorated with oxygenated functional groups which play an important role in the adsorption of P anions. Analyzes of FTIR and XRD indicated that the main adsorption mechanism for P adsorption on nB in salt affected soils was surface precipitation. Our findings suggest that the nano-biochar amendment in salt affected soils can be a promising enhancer for P adsorption.

23424. 题目: Extracellular polymeric substances alter cell surface properties, toxicity, and accumulation of arsenic in Synechocystis PCC6803
文章编号: N20030110
期刊: Environmental Pollution
作者: Sadiq Naveed, Qingnan Yu, Chunhua Zhang, Ying Ge
更新时间: 2020-03-01
摘要: Arsenic (As) contamination of water poses severe threats to human health and thus requires effective remediation methods. In this study, Synechocystis PCC6803, a model cyanobacterium common in aquatic environments, was used to investigate the role of extracellular polymeric substances (EPS) in As toxicity, accumulation, and transformation processes. We monitored the growth of Synechocystis with As exposure, measured the zeta potential and binding sites on the cell surface, and analysed As accumulation and speciation in Synechocystis cells with and without EPS. After EPS removal, the binding sites and zeta potential of the cell surface decreased by 44.43% and 31.9%, respectively. The growth of Synechocystis decreased 49.4% and 43.7% with As(III) and As(V) exposure, and As accumulation in the cells decreased by 12.8–44.5% and 14–42.7%, respectively. As absorption was enhanced in cells with EPS removed. The oxidation of As(III) and reduction of As(V) were significantly greater in cells with intact EPS compared to those with EPS removed. Fourier transform infrared spectroscopy (FTIR) showed that functional groups of EPS and Synechocystis cells, including –NH, –OH, CO, and CC, interacted with As species. Together the results of this work demonstrate that EPS have significant impacts on cell surface properties, thereby affecting As accumulation and transformation in Synechocystis PCC6803. This work provides a basis for using EPS to remedy As pollution in aquatic environments.

23425. 题目: Calibration and validation of the DNDC model to estimate nitrous oxide emissions and crop productivity for a summer maize-winter wheat double cropping system in Hebei, China
文章编号: N20030109
期刊: Environmental Pollution
作者: M. Abdalla, X. Song, X. Ju, C.F.E. Topp, P. Smith
更新时间: 2020-03-01
摘要: The main aim of this paper was to calibrate and evaluate the DeNitrification-DeComposition (DNDC) model for estimating N2O emissions and crop productivity for a summer maize-winter wheat double cropping system with different N fertilizer rates in Hebei, China. The model's performance was assessed before and after calibration and model sensitivity was investigated. The calibrated and validated DNDC performed effectively in estimating cumulative N2O emissions (coefficient of determination (1:1 relationship; r2) = 0.91; relative deviation (RD) = −13 to 16%) and grain yields for both crops (r2 = 0.91; RD = −21 to 7%) from all fertilized treatments, but poorly estimated daily N2O patterns. Observed and simulated results showed that optimal N fertilizer treatment decreased cumulative N2O flux, compared to conventional N fertilizer, without a significant impact on grain yields of the summer maize-winter wheat double cropping system. The high sensitivity of the DNDC model to rainfall, soil organic carbon and temperature resulted in significant overestimation of N2O peaks during the warm wet season. The model also satisfactorily estimated daily patterns/average soil temperature (o C; 0–5 cm depth) (r2 = 0.88 to 0.89; root mean square error (RMSE) = 4 °C; normalized RMSE (nRMSE) = 25% and index of agreement (d) = 0.89–0.97) but under-predicted water filled pore space (WFPS; %; 0–20 cm depth) (r2 = 0.3 to 0.4) and soil ammonium and nitrate (exchangeable NH4+ & NO3−; kg N ha−1; r2 = 0.97). With reference to the control treatment (no N fertilizer), DNDC was weak in simulating both N2O emissions and crop productivity. To be further improved for use under pedo-climatic conditions of the summer maize-winter wheat double cropping system we suggest future studies to identify and resolve the existing problems with the DNDC, especially with the control treatment.

23426. 题目: Multi‐year alfalfa plantation aggravates soil carbon and nitrogen stocks in the semiarid environment
文章编号: N20030108
期刊: Land Degradation & Development
作者: Wei Wang, Zheng‐Guo Cheng, Meng‐Ying Li, Bao‐Zhong Wang, Ji‐Yuan Li, Wei Wang, Yong‐Zhong Su, Asfa Batool, You‐Cai Xiong
更新时间: 2020-03-01
摘要: It is unclear how multi‐year planting of alfalfa affects soil carbon & nitrogen stocks. We investigated the alfalfa fields differing from 2, 5, 8, 10 and 20 planting years (wheat field, CK) in the semiarid Loess Plateau. In general, soil water storage tended to drop from the second to eighth year and then turned to increase at the 10th and 20th years, displaying a V‐shaped curve. Comparing with CK, soil organic carbon (SOC) was significantly improved at the second year. It started to decrease to the lowest level at the eighth year, and then recovered to increase at the 10th and 20th year. Interestingly, soil C/N ratio, microbial biomass carbon, easily oxidizable organic carbon and high fraction organic carbon followed a similar trend as SOC did, up to the lowest at the eighth year, that is, 8.28, 18.1 mg kg−1, 1.91 and 10.2 g kg−1 respectively. Particularly, light fraction organic carbon and particulate organic carbon increased up to the highest at the eighth year (1.78 and 2.81 g kg−1 respectively). Moreover, soil NH4+‐N, NO3−‐N and microbial biomass nitrogen fell into a similar dynamic as SOC did. It can be argued that soil C and N sequestration be weakened with planting years due to enhanced mineralization rate of soil active organic C and N pool. The possible mechanism causing such phenomenon was also discussed. Therefore, multi‐year planting of alfalfa aggravated the soil C & N stocks and alfalfa field should be renewed following a certain year of planting. This article is protected by copyright. All rights reserved.

23427. 题目: Preliminary techno-economic analysis of biodiesel production over solid-biochar
文章编号: N20030107
期刊: Bioresource Technology
作者: Jae-Cheol Lee, Boreum Lee, Yong Sik Ok, Hankwon Lim
更新时间: 2020-03-01
摘要: This study suggests the economic potential of biochar-based biodiesel production by conducting the techno-economic analysis. The itemized cost estimation was performed by categorizing biochar production facility and biodiesel conversion plants for 30,000 ton y-1 of biodiesel production capacity. The result of sensitivity analysis shows the methanol and waste cooking oil (WCO) costs are significantly sensitive to determine a unit biodiesel production cost. When the biodiesel selling price was 1.70 $ kg-1, the discounted payback period was varied from 1.91 (not discounted) to 2.06 years (10% discounted). In addition, the break-even price of biodiesel was calculated to 1.55 $ kg-1 when the discount rate was 10%. It means that this technology is to be feasible because of commercial diesel price (0.97 to 1.88 $ kg-1). The consideration of tax exemption and subsidy for biodiesel can be good option to supply WCO based energy production.

23428. 题目: Effects of biochar on ethanol-type and butyrate-type fermentative hydrogen productions
文章编号: N20030106
期刊: Bioresource Technology
作者: Weiming Li, Lei He, Chi Cheng, Guangli Cao, Nanqi Ren
更新时间: 2020-03-01
摘要: Low hydrogen yield was the bottleneck of dark fermentative hydrogen production. To solve this problem, the effects of rice straw-derived biochar on hydrogen production was investigated in different fermentation types. Ethanol-type and butyrate-type fermentations, two dominant types of dark fermentation, were carried out in batch fermentations with different concentrations of biochar. The results revealed that 3 g/L was the best concentration for both types of fermentations. Hydrogen production increased by 118.4% and 79.6% in ethanol-type and butyrate-type fermentations, respectively. The maximal hydrogen yields of ethanol-type and butyrate-type fermentations were 1.34 and 2.36 mol/mol-glucose, respectively. The addition of biochar buffered the broth pH, lowered the redox potential, and released mineral nutrients. The porosity of biochar boosted cell immobilization and thus improved the H2 productivity. This study demonstrated the enhancement effect of biochar on ethanol- and butyrate-type fermentative hydrogen productions, and enhanced the understanding of the functional mechanisms of biochar.

23429. 题目: Blue carbon gains from glacial retreat along Antarctic fjords: What should we expect?
文章编号: N20030105
期刊: Global Change Biology
作者: D.K.A. Barnes, C.J. Sands, A. Cook, F. Howard, A. Roman Gonzalez, C. Muñoz–Ramirez, K. Retallick, J. Scourse, K Van Landeghem, N. Zwerschke
更新时间: 2020-03-01
摘要: Rising atmospheric CO2 is intensifying climate change but it is also driving global and particularly polar greening. However, most blue carbon sinks (that held by marine organisms) are shrinking, which is important as these are hotspots of genuine carbon sequestration. Polar blue carbon increases with losses of marine ice over high latitude continental shelf areas. Marine ice (sea ice, ice shelf and glacier retreat) losses generate a valuable negative feedback on climate change. Blue carbon change with sea ice and ice shelf losses has been estimated, but not how blue carbon responds to glacier retreat along fjords. We derive a testable estimate of glacier retreat driven blue carbon gains by investigating three fjords in the West Antarctic Peninsula (WAP). We started by multiplying ~ 40 year­mean glacier retreat rates by the number of retreating WAP fjords and their time of exposure. We multiplied this area by regional zoobenthic carbon means from existing datasets to suggest that WAP fjords generate 3,130 tonnes of new zoobenthic carbon per year (t zC yr–1) and sequester > 780 t zC yr‐1. We tested this by capture and analysis of 204 high resolution seabed images along emerging WAP fjords. Biota within these images were identified to density per 13 functional groups. Mean stored carbon per individual was assigned from literature values to give a stored zoobenthic Carbon per area, which was multiplied up by area of fjord exposed over time, which increased the estimate to 4,536 t zC yr‐1. The purpose of the current study was to establish a testable estimate of blue carbon change caused by glacier retreat along Antarctic fjords and thus to establish its relative importance compared to polar and other carbon sinks.

23430. 题目: Purification of diazinon pesticide by sequencing batch moving-bed biofilm reactor after ozonation/Mg-Al layered double hydroxides pre-treated effluent
文章编号: N20030104
期刊: Separation and Purification Technology
作者: Mohammad Malakootian, Yousef Dadban Shahamat, Hakimeh Mahdizadeh
更新时间: 2020-03-01
摘要: The catalytic ozonation process (COP) using MgAl- layered double hydroxide (MgAl-LDH) nanoparticles was used as a pre-treatment of the sequencing batch moving-bed biofilm reactor (SBMBBR) to degrade diazinon pesticide from aqueous solutions. The structure of the synthesized MgAl-LDH was investigated by X-ray diffraction pattern (XRD), field-emission scanning electron microscope (FESEM), energy dispersive spectroscopy (EDS) mapping, and Fourier-transform infrared spectra (FTIR). The response surface methodology (RSM) was adopted to optimize the COP variables, including LDH dose (0-1000 mg/L), initial diazinon concentration (50-200 mg/L), initial pH (3-10), and reaction time (10-90 min). Under the optimal conditions, COP effluent was introduced to the SBMBBR for further purification. The dispersive liquid-liquid microextraction (DLLME) method was employed to extract diazinon from aqueous samples. The GC-mass analysis was performed to determine by-products during diazinon degradation reactions. To evaluate system performance, the removal efficiency of chemical oxygen demand (COD), total organic carbon (TOC), and diazinon was compared in processes of aeration, single ozonation process (SOP), COP, SBMBBR, and COP/SBMBBR. The formation of the LDH nanoparticles was confirmed by XRD and EDS mapping analysis. In the COP reactor, under optimal conditions (initial diazinon concentration: 120 mg/L, pH: 8.25, LDH dose: 750 mg/L, and reaction time: 70 min), the removal efficiency of diazinon, COD, and TOC equaled 92, 80, and 74%, respectively. The effluent of COP reactor was treated further in the SBMBBR system with the pH of 6.5-7, hydraulic retention time (HRT) of 24 h, mixed liquor suspended solids attached to bio-carriers (MLSSatt.) of 4500 mg/L, mixed liquor volatile suspended solids attached to bio-carriers (MLVSSatt.) of 3600 mg/L, MLSS of 950 mg/L, and MLVSS of 830 mg/L. The use of COP/SBMBBR resulted in the complete degradation of diazinon pesticide and COD and TOC removal efficiency of 99.37 and 99%, respectively. Therefore, this method can be used for the purification of non-biodegradable industrial wastewater.

23431. 题目: Membrane Fouling Mitigation by Fluidized Granular Activated Carbon: Effect of Fiber Looseness and Impact on Irreversible Fouling
文章编号: N20030103
期刊: Separation and Purification Technology
作者: Jingwei Wang, Bing Wu, Jia Wei Chew
更新时间: 2020-03-01
摘要: Membrane fouling mitigation by fluidized granular activated carbon (GAC) is well-acknowledged to be effective in mitigating external reversible fouling. However, the effect of fluidized GAC and fiber looseness on the alleviation of irreversible fouling is not known, which motivated the current study. Analyses included reversible and irreversible membrane fouling resistance, GAC particle velocities, foulant characteristics, permeate quality and membrane morphology. Results indicate that (i) membrane fouling resistances were significantly reduced by GAC fluidization and fiber looseness, with reversible and irreversible fouling respectively reduced by up to 17 and 35 times; (ii) advantages conferred by fiber looseness was tied to the decreased GAC particle velocities by about 10%, which implies a greater transfer of momentum from the fluidized GAC to the membranes; (iii) GAC scouring reduced 87% of reversible fouling and 48% of irreversible fouling by microbial by-product-like substances, but not so much by humic acid-like substances, whereas fiber looseness had a greater impact on the composition of the irreversible foulants; (iv) GAC particles and fiber looseness were more effective in alleviating the deposition of larger molecular weight organics in reversible fouling; (v) not only was the membrane integrity not compromised by the scouring GAC, but better permeate quality (i.e., 40% lower DOC in the permeate) was achieved; and (vi) roughness of the fouled membrane surface was 63% lower in the presence of GAC fluidization, which further reduced membrane fouling. This study thereby provides valuable insights towards the better design and operation of such fouling mitigation means for wastewater treatment.

23432. 题目: Experimental and simulation investigations of UV/persulfate treatment in presence of bromide: Effects on degradation kinetics, formation of brominated disinfection byproducts and bromate
文章编号: N20030102
期刊: Separation and Purification Technology
作者: Ziying Wang, Na An, Yisheng Shao, Naiyun Gao, Erdeng Du, Bin Xu
更新时间: 2020-03-01
摘要: Bromide (Br-), which is omnipresent in water bodies, can not only affect the degradation kinetics of target pollutants but may also form undesired byproducts (such as bromate (BrO3-) and brominated disinfection byproducts (Br-DBPs)) through sulfate radical (SO4·-)-based advanced oxidation processes (AOPs). This study found that Br- significantly suppressed the degradation of diethyl phthalate (DEP) based on the ultraviolet (UV)/persulfate (PS) treatment and was efficiently converted into reactive species (radicals and free bromine) by the SO4·- or hydroxyl radical (HO•) generated in the UV/PS system. These reactive bromine species could, in turn, brominate the phenolic degradation intermediates of DEP as well as natural organic matter (NOM), yielding Br-DBPs, including tribromomethane (TBM), which was observed when Br-, DEP and/or NOM coexisted in this UV/PS system. However, the Br-DBPs were a short-lived form of bromine during the transformation of Br– and were degraded by the excessive oxidants (e.g., SO4∙- and HO•). Instead, Br- was eventually transformed into BrO3-, with free bromine acting as the requisite intermediate. The BrO3- formation initially showed a delay before increasing monotonically. In general, raising the PS dosage and the initial Br- concentrations enhanced both the maximum concentration of TBM and the formation of BrO3-, while increasing the amounts of DEP and NOM facilitated the former and inhibited the latter. The maximum concentration of TBM increased while the formation of BrO3- was suppressed with increasing pH from 5.0 to 8.0. In addition, through simulating the steady-state concentration of radicals, it was found that the contribution of bromine atom radical (Br•) towards oxidizing free bromine to BrO3- was far greater than those of SO4∙- and HO•. The findings demonstrate the potential negative effects of Br- on SO4·--based AOPs, which need to be considered when this technology is applied in practice.

23433. 题目: Molecular Tagging for the Molecular Characterization of Natural Organic Matter
文章编号: N20030101
期刊: Environmental Science & Technology
作者: Richard York, Nicholle G. A. Bell
更新时间: 2020-03-01
摘要: Natural organic matter (NOM) is the product of microbial and abiotic decay of plant and animal remains in terrestrial and aquatic ecosystems. On a molecular level, NOM is a complex mixture of organic molecules, of which the vast majority of structures are unknown. By identifying these molecules, our understanding of the many functions of NOM could be greatly enhanced. However, given that they are chromatographically inseparable and number in the thousands, traditional analytical techniques have proven unable to achieve this goal. A promising approach to enumerate functional groups and elucidate molecular structures within NOM is based on a combination of molecular tagging and high resolution spectroscopic techniques, such as nuclear magnetic resonance spectroscopy and mass spectrometry. Molecular tagging involves the selective modification of particular functional groups, inserting nuclei to act as reporters on their surrounding chemical environment. This allows examination of only the tagged molecules within NOM, thereby reducing the complexity of the mixture. In this review, the effectiveness of molecular tagging methods incorporating carbon, silicon, nitrogen, phosphorus, and deuterium into NOM are discussed. Some potential tagging methods which have not yet been applied to NOM are also presented.

23434. 题目: Adsorption/desorption of three tetracycline antibiotics on different soils in binary competitive systems
文章编号: N20022920
期刊: Journal of Environmental Management
作者: Manuel Conde-Cid, Gustavo Ferreira-Coelho, Manuel Arias-Estévez, David Fernández-Calvinho, Avelino Núñez-Delgado, Esperanza Álvarez-Rodríguez, María J. Fernández-Sanjurjo
更新时间: 2020-02-29
摘要: Taking into account environmental and public health issues due to emerging pollutants, and specifically to antibiotics spread into environmental compartments, this work focused on the competition among three tetracycline antibiotics (tetracycline, CT; oxytetracycline, OTC; and chlortetracycline, CTC) for adsorption sites in six different soils. Batch-type adsorption/desorption tests were carried out, with 24 h as contact time. The six soils were from two different farming areas, and were selected according to pH values and organic matter contents. Binary systems (pairs of antibiotics present simultaneously) were used to study competition, setting the dose of one antibiotic at 200 μmol L−1, and varying the concentration of another from 50 to 600 μmol L−1. In the case of the concentration of 200 μmol L−1, the results of the binary systems were also compared with those obtained in simple and ternary systems. The results showed that those soils with the highest organic matter content (soils 50AL and 71S) adsorbed 100% of the three antibiotics, with desorption being <10% in all cases. The other four soils showed some degree of competition for adsorption sites in binary systems, with adsorption decreasing between 25 and 47% compared to simple systems, and with desorption increasing, especially in soils with higher pH and less organic matter. This competition was even more pronounced in ternary systems, affecting to these same soils, while the effects were very scarce in soils with higher organic matter content. The results indicate that most of the studied soils have high adsorption capacity for tetracycline antibiotics, retaining them with high energy even in the case of multiple systems. It was also shown that hysteresis affected adsorption/desorption processes. These results have relevance at environmental and social levels, given the growing concern regarding antibiotics pollution, and the need of promoting their retention and inactivation when spread in environmental compartments.

23435. 题目: The convertion of sewage sludge to biochar as a sustainable tool of PAHs exposure reduction during agricultural utilization of sewage sludges
文章编号: N20022919
期刊: Journal of Hazardous Materials
作者: Beata Tomczyk, Anna Siatecka, Yanzheng Gao, Yong Sik Ok, Aleksandra Bogusz, Patryk Oleszczuk
更新时间: 2020-02-29
摘要: There is a discussion in the literature whether PAHs introduced with biochar are safe and whether they are persistent in the environment. The persistence of PAHs (Ctot – total and Cfree – freely dissolved) in sewage sludge (SSL) or SSL-derived biochar-amended soils was investigated. Biochar were produced at 500, 600 and 700 °C. We also compared the persistence of PAHs in these experimental treatments depending on the plants cultivated (grass, clover and thale cress). We showed that the Ctot PAHs in the biochar-amended soils exhibited higher persistence than in the SSL-amended soil. The opposite trend was observed for Cfree PAHs. A higher reduction of Cfree PAHs was noted in the biochar-amended soils than in SSL-amended soil. The persistence of both Cfree and Ctot PAHs clearly varied between the biochars produced at different temperatures. It should be stated that despite that for biochar the persistence of Ctot PAHs is higher compared to SSL-amended soils, an opposite trend is observed for the fraction of Cfree (which is directly responsible for the toxic effect), and this entails a lower risk to the environment (lower mobility and bioavailability). The plants had a significant impact on Ctot PAHs content depending on the number of PAH rings.

23436. 题目: Identifying and estimating soil erosion and sedimentation in small karst watersheds using a composite fingerprint technique
文章编号: N20022918
期刊: Agriculture, Ecosystems & Environment
作者: Zihao Cao, Zhuodong Zhang, Keli Zhang, Xin Wei, Shizhen Xiao, Zhicheng Yang
更新时间: 2020-02-29
摘要: The highly heterogeneous surface environment and subsurface conduit network in karst areas make estimating soil erosion extremely complicated. Sediment fingerprint techniques have been successfully applied in soil erosion research in karst areas as a new way to more effectively collect information on soil loss. However, few sediment fingerprint factors, most of which are based on radioactive fallout tracers, such as 137Cs and/or 210Pb, have been used in existing studies. The soil loss rate estimated by these fingerprint factors varies greatly among different watersheds. To clearly identify the sedimentary sequence, to estimate the changes in soil erosion in recent years, and to relate the soil erosion process to rocky desertification, a composite sediment fingerprint technique is used in this study. Two typical watersheds with peak clusters and depressions and with different degrees of rock desertification were selected, and sediment cores were extracted from the depressions to measure changes in 137Cs, magnetic susceptibility, soil organic carbon (SOC) and sediment particle composition at different depths. The results indicated that the soil loss rates in the Liaojiawodang (LJWD) and Dajutang (DJT) watersheds showed a fluctuating decrease from 1954 to July 2018. The severe soil erosion in the periods of 1954–1963,1963–1970 and 1976–1986 was mainly caused by large-scale reclamation and deforestation. In addition, heavy rainfall in 1983 and 1991 might have played a significant role in the soil loss in the DJT watershed in 1978–1986 and in the LJWD watershed in 1986–2000, respectively. The construction of agricultural terraces several decades ago and the implementation of the Closing Mountains for Forest Cultivation, Grain for Green and Poverty Alleviation projects in recent years to improve the ecological environment have effectively alleviated the soil erosion in the studied watersheds. Over the past 60 years, soil loss in the LJWD and DJT watersheds decreased by approximately 89 % and 87 %, respectively. In karst areas, rocky desertification and soil erosion do not exhibit identical trends. Because of severe rocky desertification, the soil erosion in the LJWD watershed was significantly less than that in the DJT watershed. This study provides important information on detailed sediment dating and demonstrates the potential of using 137Cs, magnetic susceptibility, SOC and sediment particle composition to identify changes in erosion in a watershed.

23437. 题目: Linking bacterial community shifts with changes in the dissolved organic matter pool in a eutrophic lake
文章编号: N20022917
期刊: Science of The Total Environment
作者: Lei Zhang, Wangkai Fang, Xingchen Li, Guang Gao, Jiahu Jiang
更新时间: 2020-02-29
摘要: Aquatic bacterial communities play crucial roles in the circulation of nutrients in watershed ecosystems. However, the interaction between bacterial communities and chromophoric dissolved organic matter (CDOM) in freshwater ecosystems has not been studied in depth. In our study, we examined the constitution and interactions of CDOM with the bacterial community in Lake Chaohu and its inflow rivers under the influence of different exogenous pollutants. The results revealed that the bacterial community diversity in the inflow rivers was significantly lower than that in the lake sites. Clustering of different types of polluted inflow rivers integrated with the most abundant genera observed in specific areas indicated that environmentally guided species selection had a large impact on the composition of aquatic bacterial communities. Moreover, our study suggests that communities in lake environments may be more susceptible to interference through a variety of physiologies or via functional redundancy, allowing them to preserve their community structure. Through linear discriminant analysis effect size (Lefse) methods, we revealed that some taxa (from phylum to genus) were consistently enriched in the lake sites. Based on correlation network analysis results, the supersession niches of bacterial community members related to different CDOM in the biogeochemical process was determined. This study provides an ecological basis for the control of external pollution and the protection of the water environment in watershed ecosystems.

23438. 题目: Mechanistic investigation of mercury removal by unmodified and Fe-modified biochars based on synchrotron-based methods
文章编号: N20022916
期刊: Science of The Total Environment
作者: Yu Feng, Peng Liu, Yanxin Wang, Wenfu Liu, YingYing Liu, Y. Zou Finfrock
更新时间: 2020-02-29
摘要: Improved surface characteristics and incorporated Fe, S, and Cl species are reported in Fe-modified biochar, which makes it a prospective material for Hg(II) removal. In this study, aqueous Hg(II) was removed from solution by unmodified, FeCl3-modified, and FeSO4-modified biochars pyrolyzed at 300, 600, or 900 °C. Higher pyrolytic temperature resulted in higher removal efficiency, with the biochars pyrolyzed at 900 °C removing >96% of Hg(II). Fe-modification enhanced Hg(II) removal for biochars pyrolyzed at 600 °C (from 88% to >95%) or 900 °C (from 96% to 99%). Based on synchronous extended X-ray absorption fine structure (EXAFS) analysis, Hg coordinated to S in modified and unmodified biochars pyrolyzed at 900 °C, where thiol was reported, and in FeSO4-modified biochars pyrolyzed at 600 or 900 °C, where sulfide was recognized; in other biochars, Hg bound to O or Cl. Additionally, confocal micro-X-ray fluorescence imaging (CMXRFI) demonstrated Hg was distributed in agreement with S in biochars where HgS was formed; otherwise, Hg distribution was influenced by Hg species in solution and the pore characteristics of the biochar. This investigation provides information on the effectiveness and mechanisms of Hg removal that is critical for evaluating biochar applications and optimizing modification methods in groundwater remediation.

23439. 题目: Seasonal dynamics of metal phase distributions in the perennial tropical (Brahmaputra) river: Environmental fate and transport perspective
文章编号: N20022915
期刊: Environmental Research
作者: Anindita Gogoi, Kaling Taki, Manish Kumar
更新时间: 2020-02-29
摘要: An evaluation of the seasonal dynamics of metal (Cd, Cr, Cu, Pb and Zn) phase distribution and speciation, along with different hydrogeochemical facies, was conducted along the entire stretch of a perennial tropical (Brahmaputra) River. Water samples were collected from twelve locations during the monsoon, post-monsoon and pre-monsoon seasons. A characteristic trend in bioavailability was observed in the sequence of Zn > Cu > Pb > Cr > Cd, reflecting non-significant seasonal changes in dissolved and particulate phase metal fractions at all twelvelocations. Partition (or distribution) coefficients (Kds) for Cu (5.30–6.50), Zn (4.47–6.44), Pb (3.69–4.97) and Cr (3.25–5.15), reflect the influences of anionic inorganic constitutents (aqua ion complexes), environmental variables, and river hydrology. MINTEQA2 calculations showed that metal forms complexes with other inorganic ions such as Cl−, SO42−, HCO3− and strong binding as organic complexes (for Cu and Pb) reduces their leaching potential to groundwater system. High log Kd values (≥5.3) and significant spatial variations at locations R3 to R8 of Pb, Cu, and Zn during pre-monsoon period may be explained by the formation of complexes with organic ligands in sewage and domestic wastes (humic and fulvic acids). Multivariate statistical analysis revealed multi-metal co-contamination, mainly of Zn, Cu, Cd and Pb and dissolved nutrients, loading in different clusters, emphasizing the importance of climatic, anthropogenic, terrigenous and lithological sources as controlling factors for seasonal metal dynamics in the river water.

23440. 题目: Effect of calcium dihydrogen phosphate addition on carbon retention and stability of biochars derived from cellulose, hemicellulose, and lignin
文章编号: N20022914
期刊: Chemosphere
作者: Feiyue Li, Xiangyang Gui, Wenchao Ji, Chunhuo Zhou
更新时间: 2020-02-29
摘要: Pyrolysis of biomass with phosphate compound is a promising method to improve biochar characteristics. However, how phosphate compound affects the three components of biomass during the biochar formation is still unclear. In this study, a typical phosphate compound, calcium dihydrogen phosphate (Ca(H2PO4)2), was premixed with cellulose, hemicellulose, and lignin reagent, at the ratio of 20% (w/w) for biochar production through pyrolysis, aiming to investigate the effects of Ca(H2PO4)2 addition on biochar formation. Results show that, with Ca(H2PO4)2 additions, carbon retention of biochars from cellulose (MCBC) and hemicellulose (MHBC) increased by 63.4% and 48.3%, respectively, but that of lignin (MLBC) decreased by 6.7% due to the reactions between lignin and Ca(H2PO4)2. Moreover, the stable carbon proportion in the biochar decreased by 10.2% for MCBC, almost unchanged for MHBC, and increased by 6.15% for MLBC based on the potassium dichromate oxidation. During the pyrolysis process, Ca(H2PO4)2 addition fixed more volatile and/or labile carbon in biochar, resulting in greater carbon retention. Declined carbon stability of biochar might be caused by the inhibited formation of aromatic-C, evidenced by the Fourier transform infrared spectroscopy analysis. This study highlights the importance and potential mechanisms of calcium dihydrogen phosphate influencing the carbon retention and stability of biochar derived from three biomass components.