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17701. 题目: Alpine meadow degradation enhances the temperature sensitivity of soil carbon decomposition on the Qinghai–Tibetan plateau
文章编号: N21110909
期刊: Applied Soil Ecology
作者: Junmin Pei, Dong Yan, Jinquan Li, La Qiong, Yuanwu Yang, Changming Fang, Jihua Wu
更新时间: 2021-11-09
摘要: Grassland degradation is widespread globally, yet limited information is available on the effects and mechanisms of grassland degradation regarding the response of soil organic carbon (SOC) to temperature change. This is especially true for alpine regions, which can have high SOC storage and are extreme vulnerability to global warming. Here, we studied the temperature sensitivity of SOC decomposition (Q10, proportional change in decomposition rate for a 10 °C difference in temperature) in both the topsoil (0–10 cm depth) and subsoil (20–30 cm) along an alpine meadow degradation gradient on the Qinghai–Tibetan plateau (QTP). Q10 values were increased in response to alpine meadow degradation (severely degraded (2.42) > moderately degraded (2.20) > non-degraded (2.11)) and were higher in subsoil (2.34) than in topsoil (2.14) as a whole. Soil carbon quantity and quality and extracellular enzyme activities all decreased significantly with increasing degradation levels and soil depths. Among all the factors considered (soil texture; soil pH; carbon quantity, availability, and quality; and enzyme activities), Q10 values were found to be primarily mediated by carbon quality and enzyme activities. This result supported the “carbon-quality temperature” hypothesis in degraded alpine grassland, and that considering soil carbon quality and enzyme activity could improve predictions of the feedbacks between soil carbon and global warming under grassland degradation. Our findings suggest that alpine meadow degradation will further increase the losses of SOC in a warming climate, making the ecosystem more vulnerable to climate change.

17702. 题目: Efficiency and mechanisms of Sb(III/V) removal by Fe-modified biochars using X-ray absorption spectroscopy
文章编号: N21110908
期刊: Journal of Environmental Chemical Engineering
作者: Xin Liu, Jianwei Zhou, Weiqing Zhou, Yu Feng, Y. Zou Finfrock, YingYing Liu, Peng Liu, Cheng Shu
更新时间: 2021-11-09
摘要: Fe-modified biochars (FeBC) are effective antimony (Sb) removal materials; however, the removal mechanisms require further investigation. In this study, aqueous Sb(III) and Sb(V) removal by FeBC (300, 600, and 900 °C) was evaluated, with the adsorption mechanisms investigated using X-ray absorption spectroscopy (XAS). Screening results (based on removal efficiencies) using different types of FeBC indicated the 900 °C FeCl3-modified biochar (FeCl3BC900) achieved the best Sb(III/V) removal performance. The kinetics of the Sb(III/V) removal process were best fitted by a pseudo-second-order model. Additionally, the isothermal results were described by Langmuir and Redlich-Peterson models. Aqueous analysis and X-ray absorption near-edge structure data fitting indicated Sb(III) was oxidized to Sb(V) in the Sb(III)-spiked system, and the oxidation extent increased with increasing pyrolysis temperature. The oxidation process rapidly occurred in both the solution and biochar. No Sb(V) was reduced to Sb(III) in the Sb(V)-spiked system. The XAS results of the isothermal experiment indicated the oxidation capacity of FeCl3BC900 was limited for high initial Sb(III) concentrations. The Sb-Fe1 and Sb-Fe2 bonding distances were 3.05-3.10 and 3.47-3.54Å, respectively, indicating inner-sphere complexes were formed during the Sb(III/V) removal processes. The Sb(III/V) removal mechanisms included electrostatic adsorption, inner-sphere complexes, and coprecipitation. Oxidation was also involved in Sb(III) removal.

17703. 题目: Sources and composition of riverine dissolved organic matter to marginal seas from mainland China
文章编号: N21110907
期刊: Journal of Hydrology
作者: Zhidan Wen, Yingxin Shang, Lili Lyu, Ge Liu, Junbin Hou, Chen He, Quan Shi, Ding He, Kaishan Song
更新时间: 2021-11-09
摘要: Rivers are an important connection between terrestrial ecosystems and the ocean, and are hotspots of organic carbon transformation. Riverine dissolved organic matter (DOM) concentration and composition are sensitive to both regional and global change processes. The comparative studies on riverine DOM among different rivers, especially when it comes to seasonal changes, were critical to better constrain the river carbon cycle. In this study, we analyzed organic carbon concentration, DOM sources and composition from the estuary locations of 48 Chinese rivers using the stable isotopic analysis and Fourier transform ion cyclotron resonance mass spectrometry. Both dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations, displayed significantly higher mean values in autumn than in summer (p < 0.05). Most of the DOM in these rivers entering marginal seas in four seasons came from the terrigenous sources (60.6%-68.4%), followed by the autochthonous matters (18.6%-25.6%), and the contribution of the anthropogenic sewage ranged from 7.6% to 13.7%. The proportion contributions of terrigenous and anthropogenic sources to DOM were similar in all seasons, but the contribution of autochthonous inputs showed the highest value in autumn than other seasons (p>0.05). Although the highly unsaturated compounds are the most abundant molecular formulas detected in all riverine DOM, the molecular composition of riverine DOM shows a large difference among seven river basins. The human activity disturbance may be one of the major reasons for DOM composition differences. The contribution of sewage discharge on Chinese riverine DOM flux could be roughly estimated as 16.11-17.74 Gg peptides /yr. This work seeks to provide a foundation for ongoing research of regional and global riverine carbon cycling, and put forward the method for evaluating the potential impact of human disturbances on riverine organic carbon components in Chinese rivers.

17704. 题目: Monitoring of the impact of the proliferations of cyanobacteria on the characteristics of Natural Organic Matter in a eutrophic water resource: Comparison between 2012–2013 and 2017–2018
文章编号: N21110906
期刊: Chemosphere
作者: Hélène Thuret-Benoist, Virginie Pallier, Geneviève Feuillade-Cathalifaud
更新时间: 2021-11-09
摘要: The natural surface waters are widely impacted by the seasonal blooms of phytoplankton and in water rich in nutrients their developments are controlled by the climate. These proliferations modify the global quality of the water resources and the Algal Organic Matter (AOM) produced by the algae and the cyanobacteria impacts the content and the characteristics of the Natural Organic Matter (NOM). However, none study deals with the sustainable influence of the recurrent seasonal blooms of phytoplankton on the chemical quality of the water resources. The physico-chemical, chemical and biological quality of a water resource and more specifically the content and the characteristics of the NOM were thus in situ monitored in a eutrophic pond in 2017–2018 and compared to the characteristics observed in 2012–2013. The blooms of phytoplankton were more important in 2017–2018 and the increase of both the temperature of the air and the radiance promoted the domination of cyanobacteria. None significant evolution of the content in chlorophyll-a, the concentrations in nutrients and the pH was observed between 2012–2013 and 2017–2018. However, the concentrations in DOC increased, more in summer periods than winter, because of the production of AOM by the algae and the cyanobacteria and the NOM presented more hydrophilic and less aromatic characters. These evolutions of the characteristics of the NOM were more important in 2017–2018 than 2012–2013. The recurrent inputs of AOM every year in summer periods seemed thus to sustainably modify the intrinsic characteristics of the NOM.

17705. 题目: Combing phosphorus-modified hydrochar and zeolite prepared from coal gangue for highly effective immobilization of heavy metals in coal-mining contaminated soil
文章编号: N21110905
期刊: Chemosphere
作者: Qilong Ge, Qi Tian, Rui Hou, Sufang Wang
更新时间: 2021-11-09
摘要: Considering the adverse effects of heavy metals (HMs) on agriculture soil, in-situ immobilization has been paid great attention worldwide. P-modified biochar/hydrochar along with synthetic zeolite for efficient HMs immobilization in contaminated soil becomes a promising choice. In this study, H3PO4-modified hydrochar (BPH) derived from banana peels, and Na-X zeolite (ZL) prepared from coal gangue was applied individually and synergistically (1%BPH, 2%BPH 1%ZL, 2%ZL, and 1%BPH+1%ZL) to remediate a farmland soil polluted by Cd, Cu, and Pb near the coal-mining area. Compared with the mono-application of these two amendments, their combination significantly improved the soil organic carbon (SOC), electric conductivity (EC), and dehydrogenase activity. Besides, the addition of 1%CLH+1%ZL remarkably reduced the Cd, Cu, and Pb bioavailability by 67.01%, 57.01%, and 78.72%, respectively, in the soil after 100 d incubation by transforming these metals to more stable forms. The order of the HMs immobilization capacity for these two amendments was as follows: Pb > Cu > Cd. Moreover, the dominated immobilization mechanism of their synergistic application was that BPH could immobilize HMs by precipitation, complexation, and π−π electron-donor-acceptor interaction. The precipitation and complexation blocked the surface pores of BPH. The sustained release of phosphorus groups and radicals was prevented. This obstacle was possibly alleviated by adding ZL. Besides, the formation of cationic bridging, the enhancement of soil properties, and the physical adsorption of these amendments were also conducive to HMs immobilization in soil. This work indicated that co-application of BPH and ZL possibly was an excellent choice for immobilizing HMs in soil.

17706. 题目: Biochemical phosphorus transformations in a calcareous soil as affected by earthworm, cow manure and its biochar additions
文章编号: N21110904
期刊: Applied Soil Ecology
作者: Safoora Nahidan, Mahshid Ghasemzadeh
更新时间: 2021-11-09
摘要: Application of raw or char material may modify the influence of earthworm activity on soil phosphorus (P) transformation. The purpose of this study was to investigate the effect of cow manure or cow manure biochar addition and its interaction with earthworm on organic (Po) and inorganic (Pi) P fractions, alkaline phosphatase activity and P-solubilizing bacteria (PSB) in a calcareous soil of semi-arid region. For this purpose, the soil was amended with cow manure and its biochar in 4 levels (0, 1, 2 and 5%) in the absence and presence of earthworm (Eisenia fetida). The treatments were then incubated for 90 days. The monitoring of earthworms was also carried out after 30 and 90 days incubation. The results showed an increase in weight of earthworms in control and cow manure amended soils at both incubation times. However, application of cow manure biochar resulted in mortality and an initial weight loss of earthworms (36–85%) at 30 days incubation. This negative effect decreased over time, so that the earthworms recovered in 1% biochar amended soil. Amendment additions increased proportion of NaHCO3-Pi and NaOH-Pi but decreased proportion of HCl-Pi, residual-P, NaOH-Po and HCl-Po, making P more available in soil. The impact of cow manure biochar on the NaHCO3-Pi and NaOH-Pi fractions was stronger than that of cow manure. Earthworm decreased the proportion of Pi fractions but increased the proportion of Po fractions, indicating a transformation of P from Pi to Po forms. Alkaline phosphatase activity and PSB number were also increased as affected by earthworm and amendment (especially cow manure) additions. No significant interaction between earthworm and amendment additions was observed (p < 0.05), indicating that the influence of earthworm on P transformations was not dependent on amendment additions. Overall, we concluded that biochar can be useful for the amendment of semi-arid calcareous soil in terms of P availability, but the negative response of earthworms to biochar and its effect on other soil processes should be taken into consideration.

17707. 题目: Role of Antioxidant Moieties in the Quenching of a Purine Radical by Dissolved Organic Matter
文章编号: N21110903
期刊: Environmental Science & Technology
作者: Shuangshuang Cheng, Yujie Zhao, Yanheng Pan, Jinpeng Yu, Yu Lei, Xin Lei, Gangfeng Ouyang, Xin Yang
更新时间: 2021-11-09
摘要: Dissolved organic matter (DOM) has been known to inhibit the degradation of trace organic contaminants (TrOCs) in advanced oxidation processes but quantitative understanding is lacking. Adenine (ADN) was selected as a model TrOC due to the wide occurrence of purine groups in TrOCs and the well-documented transient spectra of its intermediate radicals. ADN degradation in the presence of DOM during UV/peroxydisulfate treatment was quantified using steady-state photochemical experiments, time-resolved spectroscopy, and kinetic modeling. The inhibitory effects of DOM were found to include competing for photons, scavenging SO4•– and HO•, and also converting intermediate ADN radicals (ADN(-H)•) back into ADN. Half of the ADN(-H)• were reduced back to ADN in the presence of about 0.2 mgC L–1 of DOM. The quenching rate constants of ADN(-H)• by the 10 tested DOM isolates were in the range of (0.39–1.18) × 107 MC–1 s–1. They showed a positive linear relationship with the total antioxidant capacity of DOM. The laser flash photolysis results of the low-molecular-weight analogues of redox-active moieties further supported the dominant role of antioxidant moieties in DOM in the quenching of ADN(-H)•. The diverse roles of DOM should be considered in predicting the abatement of TrOCs in advanced oxidation processes.

17708. 题目: Limited effects of century-old biochar on taxonomic and functional diversities of collembolan communities across land-uses
文章编号: N21110902
期刊: Soil Biology and Biochemistry
作者: Sasha Pollet, Ariane Chabert, Victor Burgeon, Jean-Thomas Cornélis, Julien Fouché, Charles Gers, Brieuc Hardy, Benjamin Pey
更新时间: 2021-11-09
摘要: Biochar is often considered as a promising climate-smart agricultural tool capable of stabilizing carbon overtime in soils while improving crop productivity. However, long-term consequences for soil biodiversity have barely been addressed. The main aim of this study was to investigate the effects of centennial biochar on the total collembolan densities, the taxonomic and functional diversities of collembolan communities. We sampled preindustrial charcoal kiln sites across three land-uses (cropland, grassland and forest) in temperate soils as model for aged biochar. The complementarity use of total collembolan densities, a taxonomic approach (species richness, Pielou evenness) and a functional approach (functional richness, Rao quadratic entropy, community-weighted means of the functional traits) showed that charcoal enrichment had little effect on collembolan communities. Yet, there was a systematic shift in traits composition of collembolan communities towards traits adapted to life at depth in the presence of charcoal across land-uses. In cropland soils, charcoal induced minor species and abundance changes that significantly shifted the traits composition. In grassland soils, charcoal significantly decreased the taxonomic evenness of communities and host new species with more diverse functional profiles. In forest soils, charcoal was suggested to induce a species domination and a functional homogenization of collembolan communities. Our results suggest that the long-term effect of biochar on soil fauna are related to slight direct or indirect modifications of soil habitat, which hinges on land-use. Indeed, the land-use was a much stronger driver in shaping soil collembolan communities than centennial charcoal. We advocate furthering functional traits studies on the ecological and edaphic mechanisms driving Collembola long-term responses to biochar amendment.

17709. 题目: Inactivation of Microcystis Aeruginosa by Peracetic Acid Combined with Ultraviolet: Performance and Characteristics
文章编号: N21110901
期刊: Water Research
作者: Lisan Cao, Jingwen Wang, Zongping Wang, Shiwen Yu, Yujie Cheng, Jun Ma, Pengchao Xie
更新时间: 2021-11-09
摘要: The inactivation of algae by a combined process of peracetic acid and ultraviolet irradiation (UV/PAA) was systematically investigated by choosing Microcystis aeruginosa as the reference algal species. Both hydroxyl (HO•) and organic radicals (RO•) contributed to the cell integrity loss and RO• played the dominant roles. The algae inactivation kinetics can be well fitted by the typical Hom model, showing that the inactivation kinetic curves followed a type of shoulder and exponential reduction. The initial shoulder might be induced by the protection from the cell wall. Although the results from the cell morphology, UV-vis spectra and fluorescence excitation-emission matrices analysis suggested the cell lysis and the release of algal organic matter (AOM) in the UV/PAA process, the AOM could be subsequently degraded. Humic acid (1−5 mg/L) inhibited the algal cell inactivation, and the presence of chloride (0.5−2 mM) had little effect on the cell viability reduction. However, the addition of bicarbonate (1−5 mM) promoted cell integrity loss. The UV/PAA process displayed better performance under the natural water background, demonstrating the extensive potential for the practical application of this approach. This study suggests that the UV/PAA process is an effective strategy for algae inactivation.

17710. 题目: Tracing organic matter sources in the estuarine sediments of Vanga, Kenya, and provenance implications
文章编号: N21110721
期刊: Estuarine, Coastal and Shelf Science
作者: Amon Kimeli, Shawlet Cherono, Bonface Mutisya, Fredrick Tamooh, Judith Okello, Hildegard Westphal, Nico Koedam, James Kairo
更新时间: 2021-11-07
摘要: Mangrove ecosystems can potentially and indirectly modulate the effects of sea level rise due to their ability to trap and retain sediments. In order to gain a better understanding of the potential sediment dynamics in the mangroves of Vanga, Kenya, inter-seasonal riverine, estuarine and coastal/marine sediments together with agricultural soil and mangrove tissues were studied. Elemental ratios (C/N) and carbon (δ13C) stable isotope composition, were analysed to disentangle sources of sediment organic matter (SOM) in the Vanga, Estuary. The organic carbon (C) content, C/N ratios and δ13C values ranged between 0.1 and 2.4%, 9.9 to 35.5 and −24.8 to −19.9‰ respectively. These contents were also as expected relatively higher in mangrove tissues than in all the sediment samples. δ13C values of mangrove sediments were higher than those of the mangrove tissues, which was attributed to rapid decomposition, dilution by freshwater and mineral organic matter (OM) discharged by the Umba River as well as outwashing by ebb tides. On average, C/N ratios were also observed to be greater than 10 in all samples collected during both the dry and wet season. This has been shown to reflect a pronounced contribution of allochthonous organic matter. Using a combination of δ13C values and C/N ratio, the dominance of riverine POM was also evident from a Bayesian Stable Isotope Mixing Model in R-program (SIMMR) that indicated OM source mixing but with a dominant (∼60%) contribution of riverine OM. The observed and modeled variability of SOM in the Vanga estuary points to the hypothesized influence of the Umba River on Vanga Estuary sediments but with evidence of potential material exchange and influence of tidal fluxes within the estuary.

17711. 题目: Effects of marine produced organic matter on the potential estuarine capacity of NOx− removal
文章编号: N21110720
期刊: Science of The Total Environment
作者: Fangjuan Huang, Xianbiao Lin, Kedong Yin
更新时间: 2021-11-07
摘要: Dissolved inorganic nitrogen (DIN) is very high in the Pearl River Estuary (PRE) and nitrate (NOx−) removal processes such as denitrification, anaerobic ammonium oxidation (anammox) and dissimilatory nitrate reduction to ammonium (DNRA) are important for determining export of DIN to coastal waters. However, fluxes of NOx− removal and influencing factors in the PRE are still unclear. We conducted 4 cruises at 11 sites in the PRE to investigate potential NOx− removal rates, their contributions, and corresponding gene abundances, and controlling factors in surface sediments (0–5 cm). The results showed that the potential rates of denitrification, anammox, and DNRA as well as their contributions varied spatially and seasonally. Denitrification (1.98 ± 1.7 μg N g−1 d−1) was the major NOx− removal processes (68.43 ± 14.61%) while DNRA (0.45 ± 0.28 μg N g−1 d−1) contributed 22.61 ± 14.89% in NOx− removal. The NOx− removal processes and corresponding gene abundances were correlated with the chlorophyll concentrations in both overlying water and sediment, indicating that marine-produced organic matter was the major driver for benthic NOx− removal processes. In addition, water column turbidity had important effects on primary production, which affects benthic N processes. Our study provides evidences for that the turbidity-regulated primary production in overlying water is the primary driver for benthic NOx− removal processes. The contribution of sediment NOx− removal fluxes to water column NOx− concentration was low in the upper estuary and increased in the lower estuary where marine produced chlorophyll a was higher. However, daily fluxes of NOx− removal were estimated to account for only 0.18–7.22% (mean 1.85 ± 1.62%) of NOx− in the whole overlying water column. This suggests that most riverine NOx− was exported out into the adjacent coastal waters.

17712. 题目: Catalytic performance and periodate activation mechanism of anaerobic sewage sludge-derived biochar
文章编号: N21110719
期刊: Journal of Hazardous Materials
作者: Pengyu Xiao, Xianliang Yi, Minghuo Wu, Xue Wang, Simeng Zhu, Bixia Gao, Yang Liu, Hao Zhou
更新时间: 2021-11-07
摘要: Periodate (PI)-based advanced oxidation processes are a newly discovered approach for effective pollutant elimination. In this study, we demonstrated that biochar obtained from pyrolysis of anaerobic sewage sludge without any pretreatment can be used for PI activation. The biochar obtained at 800 °C (SBC-800) exhibited the best PI activation capacity using acid organic II (AO7) as substrate. The PI activation was strongly dependent on pH and exhibited the highest AO7 removal rate at pH 3.0. Meanwhile, the anti-interference capacity with common wastewater components and reusability of the SBC-800/PI system were confirmed. Combined with the results of chemical quenching, reactive oxygen species (ROS) trapping, X-ray photoelectric spectroscopy (XPS), electrochemical and density function theory (DFT)-based calculations, singlet oxygen production and electron transfer mediated by the SBC-800-PI complex were the dominant AO7 oxidation mechanisms. This study provides easily prepared catalysts for PI activation and paves the way for solid waste recycling and reuse.

17713. 题目: Catalytic mechanism of nitrogen-doped biochar under different pyrolysis temperatures: The crucial roles of nitrogen incorporation and carbon configuration
文章编号: N21110718
期刊: Science of The Total Environment
作者: Yu Wan, Yan Hu, Wenjun Zhou
更新时间: 2021-11-07
摘要: To scrutinize the crucial role of carbon configuration and nitrogen speciation in peroxymonsulfate (PMS) activation, nitrogen-doped biochars (NBCs) were prepared at different pyrolysis temperatures (700, 800 and 900 °C) and named NBC700, NBC800 and NBC900, respectively. Nitrogen doping introduced many nitrogen-containing groups into NBCs and the carbon configuration and nitrogen speciation of NBCs were regularly changed by the pyrolysis temperature. Compared to the phenol (PN) removal in the pristine biochar (BC)/PMS system that mainly depended on adsorption, NBCs showed excellent PMS activation activity for efficient PN degradation and the PMS activation activity was highly dependent on the carbon configuration and nitrogen speciation of NBCs. Furthermore, the PMS activation pathways of NBCs were unveiled to convert 1O2 to electron transfer with increasing pyrolysis temperature, which was ascribed to the variation of active sites on NBCs caused by the regular changes in carbon configuration and nitrogen speciation. Pyridinic N and oxygen groups (CO, CO and O-C=O) were proposed as potential active sites on NBC700 and NBC800 for 1O2 generation via PMS activation. Differently, the highly sp2-hybridized carbon skeleton and graphitic N of NBC900 played an important role in the electron transfer pathway by acting as a carbon bridge to accelerate electron transfer from PN to PMS. This study provides new insight into the effects of carbon configuration and nitrogen speciation on PMS activation mechanism of NBCs and identifies opportunities for the subsequent catalyst design in a specific degradation pathway.

17714. 题目: Response of soil chemical properties, enzyme activities and microbial communities to biochar application and climate change in a Mediterranean agroecosystem
文章编号: N21110717
期刊: Geoderma
作者: José Luis Moreno, Felipe Bastida, Marta Díaz-López, Yunkai Li, Yunpeg Zhou, Rubén López-Mondéjar, Iria Benavente-Ferraces, Roxana Rojas, Ana Rey, Juan Carlos García-Gil, César Plaza
更新时间: 2021-11-07
摘要: Changing climatic conditions (warming and decreasing precipitation) have been found to be a threat to the agricultural sustainability of Mediterranean croplands. From the climate change perspective, biochar amendment may interact with the effects of warming and drought stresses on soil ecosystems. However, the responses of soil microbial communities to the joint effects of climate change and biochar in Mediterranean croplands are not sufficiently known. To help fill this knowledge gap, in this work we used a field experiment to determine the effects of partial rain exclusion alone or combined with a soil temperature increase in biochar-amended (20 t ha−1) and unamended plots under crop rotation on soil chemical properties, enzyme activities, and the microbial community activity, structure, composition, abundance, and functions. The biomass, composition, and activity of the soil bacterial and fungal communities were more responsive to biochar addition than to climate manipulation. Thus, soil chemical parameters, enzyme activities and the relative abundances of bacterial populations were not responsive to the interaction of biochar and climate manipulation, while the predicted functionality of the bacterial community was modified by both factors. Soil β-glucosidase activity significantly decreased in response to biochar addition and climate manipulation, while urease activity was significantly increased by biochar, and protease activity was significantly decreased by climate manipulation. Gram negative and fungal biomasses were significantly affected by the interaction of biochar with climate manipulation. Climate manipulation produced changes in the composition of the soil fungal community without loss of diversity. This study illustrates how the interactions between biochar amendment and future climate change scenarios influence microbially-driven ecosystem services related to the maintenance of nutrient cycles and biodiversity in a Mediterranean agroecosystem.

17715. 题目: Event‐based runoff and sediment yield dynamics and controls in the sub‐humid headwaters of the Blue Nile, Ethiopia
文章编号: N21110716
期刊: Land Degradation & Development
作者: Habtamu Assaye, Jan Nyssen, Jean Poesen, Hanibal Lemma, Derege Tsegaye Meshesha, Alemayehu Wassie, Enyew Adgo, Deribew Fentie, Amaury Frankl
更新时间: 2021-11-07
摘要: Land degradation due to soil erosion presents a major challenge for sustainable development. We investigated runoff and sediment yield dynamics in the NW highlands of Ethiopia. The study area included 14 zero-order catchments with a surface area ranging from 324 m2 to 1715 m2. V-notch weirs produced from plastic jars were introduced as measuring alternatives that met local constraints. Runoff depth at the weir was registered manually at 5-min intervals during two rainy seasons in 2018 and 2019 and a total of 618 events were monitored. Rainfall was measured using tipping-bucket rain gauges. Runoff samples were collected in 1-L bottles and suspended sediment concentration (SSC) was determined. The mean event runoff coefficient ranged from 3% for forests to 56% for badlands. Similarly, the mean annual sediment yield (SY) was lowest for forests (0.8 Mg ha−1 yr−1) and highest for badlands (43.4 Mg ha−1 yr−1), with significant differences among land use types (14.8 Mg ha−1 yr−1 in cropland, 5.7 Mg ha−1 yr−1 in grazing land, and 2.9 Mg ha−1 yr−1 in plantations). Soil organic matter (SOM) reduced runoff and SY, necessitating the consideration of agronomic and land management practices that enhance SOM. Annual SY decreased exponentially with the rock fragment cover (RFC). In fields where RFC was less than 20%, collecting rock fragments for installing stone bunds resulted in a net increase in SY. Rehabilitating badlands and enhancing SOM content in croplands can substantially reduce catchment SY and, hence contribute to the sustainability of land uses in the subhumid highlands.

17716. 题目: Concentration, optical characteristics, and emission factors of brown carbon emitted by on-road vehicles
文章编号: N21110715
期刊: Science of The Total Environment
作者: Ru-Jin Huang, Wei Yuan, Lu Yang, Huinan Yang, Wenjuan Cao, Jie Guo, Ningning Zhang, Chongshu Zhu, Yunfei Wu, Renjian Zhang
更新时间: 2021-11-07
摘要: Atmospheric brown carbon (BrC) is a light-absorbing component that affects radiative forcing; however, this effect requires further clarification, particularly with respect to BrC emission sources, chromophores, and optical properties. In the present study, the concentrations, optical properties, and emission factors of organic carbon (OC), water-soluble OC (WSOC), and humic-like substances (HULIS) in fine particulate matter (PM2.5) emitted from vehicles in three road tunnels (the Wucun, Xianyue, and Wenxing tunnels in Xiamen, China) were investigated. The mass concentrations and light absorption of OC, WSOC, and HULIS were higher at the exits of each tunnel than at entrances, demonstrating that vehicle emissions were a BrC source. At each tunnel's exit, the average light absorption contributed by HULIS-BrC to water-soluble BrC (WS-BrC) and total BrC at 365 nm was higher than the corresponding carbon mass concentration contributed by HULIS (HULIS-C) to WSOC and OC, indicating that the chromophores of HULIS emitted from vehicles had a disproportionately high effect on the light absorption characteristics of BrC. The emission factors (EFs) of HULIS-C and WSOC mass concentrations were highest at the Xianyue tunnel; however, the EFs of HULIS-BrC and WS-BrC light absorption were highest at the Wenxing tunnel, indicating that the chromophore composition of BrC was different among the tunnels and that the mass concentration EFs did not correspond directly to the light absorption EFs.

17717. 题目: Effects of organic matter complexation on partitioning of transition metals into calcite: Cave-analogue crystal growth experiments
文章编号: N21110714
期刊: Geochimica et Cosmochimica Acta
作者: I. Lindeman, M. Hansen, D. Scholz, S.F.M. Breitenbach, A. Hartland
更新时间: 2021-11-07
摘要: We highlight the potential for first row transition metals to carry paleohydrological signals in speleothems, and argue that these metals constitute valuable proxies for climate reconstructions. Metal availability to speleothems is hypothesised to be restricted by organic complexation, which strongly limits the free ion activity of transition metals (Co2+, Ni2+ and Cu2+) in dripwater, thereby creating a kinetic overprint on metal concentrations and isotope ratios in speleothem calcite. This study presents the results of the first cave-analogue experiments of transition metal partitioning into calcite in the absence and presence of organic ligands. The Geological Microclimate (GeoMic) system establishes homeostatic control of air temperature and atmospheric pCO2 (set to 20 ± 0.1 °C and 1000 ± 10 ppm, respectively), and regulates relative humidity to cave-analogue levels (>90%). Calcite was precipitated from flowing aqueous films on inclined glass plates to assess the effect of prior calcite precipitation (PCP) on metal partitioning. We report speleothem-specific inorganic Kd values for Co, Ni and Cu of ∼4, 1, and 44, respectively. Pronounced PCP effects were observed in Co and Cu in the inorganic experiments, leading to strong reduction in Cu/Ca and Co/Ca, whereas Ni/Ca molar ratios remained constant. Introduction of the organic chelating ligand nitrilotriacetic acid (NTA) overturned the behaviour of all three metals, leading to stable solution Cu/Ca ratios and progressive enrichment of Co/Ca and Ni/Ca ratios as PCP progressed and apparent Kd values <1 for all three metals. This result is confirmed in a Cu-fulvic acid experiment. We show that in the presence of organic ligands with stability constants close to those observed in natural systems, the partitioning of transition metals into calcite is dependent on the fluid residence time and the stability of the metal-ligand complexes. Therefore, drip rate should be the first-order control on transition metal concentrations in stalagmites: opening the way to a novel and potentially quantitative paleohydrological proxy.

17718. 题目: Key predictors of soil organic matter vulnerability to mineralization differ with depth at a continental scale
文章编号: N21110713
期刊: Biogeochemistry
作者: Tyler L. Weiglein, Brian D. Strahm, Maggie M. Bowman, Adrian C. Gallo, Jeff A. Hatten, Katherine A. Heckman, Lauren M. Matosziuk, Lucas E. Nave, Angela R. Possinger, Michael D. SanClements, Christopher W. Swanston
更新时间: 2021-11-07
摘要: Soil organic matter (SOM) is the largest terrestrial pool of organic carbon, and potential carbon-climate feedbacks involving SOM decomposition could exacerbate anthropogenic climate change. However, our understanding of the controls on SOM mineralization is still incomplete, and as such, our ability to predict carbon-climate feedbacks is limited. To improve our understanding of controls on SOM decomposition, A and upper B horizon soil samples from 26 National Ecological Observatory Network (NEON) sites spanning the conterminous U.S. were incubated for 52 weeks under conditions representing site-specific mean summer temperature and sample-specific field capacity (−33 kPa) water potential. Cumulative carbon dioxide respired was periodically measured and normalized by soil organic C content to calculate cumulative specific respiration (CSR), a metric of SOM vulnerability to mineralization. The Boruta algorithm, a feature selection algorithm, was used to select important predictors of CSR from 159 variables. A diverse suite of predictors was selected (12 for A horizons, 7 for B horizons) with predictors falling into three categories corresponding to SOM chemistry, reactive Fe and Al phases, and site moisture availability. The relationship between SOM chemistry predictors and CSR was complex, while sites that had greater concentrations of reactive Fe and Al phases or were wetter had lower CSR. Only three predictors were selected for both horizon types, suggesting dominant controls on SOM decomposition differ by horizon. Our findings contribute to the emerging consensus that a broad array of controls regulates SOM decomposition at large scales and highlight the need to consider changing controls with depth.

17719. 题目: Role of coconut shell biochar and earthworm (Eudrilus euginea) in bioremediation and palak spinach (Spinacia oleracea L.) growth in cadmium-contaminated soil
文章编号: N21110712
期刊: Journal of Environmental Management
作者: Florence Ruth Noronha, Soumya Koippully Manikandan, Vaishakh Nair
更新时间: 2021-11-07
摘要: The contamination of soil with heavy metals is known to affect the yield the soil fertility, which in turn affects the growth of agricultural crops. This study investigates the role of coconut shell biochar (CSB) and earthworms (Eudrilus euginea) in the bioremediation and growth of Palak spinach (Spinacia oleracea L.) in cadmium (Cd) contaminated soil. The soils were amended with different combinations of CSB and earthworms and incubated for 35 days. Later, the soil samples were analyzed for the changes in the soil properties, soil enzyme activity, and heavy metal contents. It is observed that the treatments with both CSB and earthworms resulted in the improvement of soil properties and soil enzyme activity which was directly related to soil fertility. Meanwhile, the maximum removal of 94.38% of total Cd content in the soil was obtained for the soil sample contain both CSB and earthworms. The improved soil properties resulted in a higher germination percentage of Spinacia oleracea L. seeds in the Cd contaminated soil.

17720. 题目: Photoformation of environmentally persistent free radicals on particulate organic matter in aqueous solution: Role of anthracene and formation mechanism
文章编号: N21110711
期刊: Chemosphere
作者: Xintong Li, Hongxia Zhao, Baocheng Qu, Yu Tian
更新时间: 2021-11-07
摘要: Environmentally persistent free radicals (EPFRs) generated under irradiation have been widely detected in soil particles, atmospheric particles and microplastic particles, but the formation of EPFRs in water is not well understood. This study investigated the formation of EPFRs on particulate organic matter (POM) in water contaminated by anthracene (Ant) under irradiation. The photoformation and decay progress of EPFRs was represented with the help of electron paramagnetic resonance (EPR) technique on both actual POM and Fe(III)-montmorillonite simulated samples. EPR signals at the range of 1016 to 1017 spin/g were detected and the half-life time of EPFRs stored in water was at around 16.62 h and 60.80 h, much shorter than those in the air. The g factors were all larger than 2.0040, which indicated the generation of oxygen centered EPFRs. The primary intermediates were identified by gas chromatography-mass spectrometer (GC-MS) and a possible EPFR formation pathway during Ant degradation was proposed. The interaction between Ant and POM, and the hydroxylation and carbonylation of the intermediates made contributions to the generation of EPFRs. Meanwhile, the indirect photodegradation of bisphenol A (BPA) has been demonstrated by analyzing the reactive oxygen species (ROS) and photogenerated electrons in the solution with POM containing EPFRs. It is found that hydroxyl radicals (•OH) and singlet oxygen (1O2) were induced and might promote the photodegration. Overall, our present study provided useful information to understand the photoformation of EPFRs on POM and their fate in aqueous environments.