41. 题目: Insights into the interaction of microplastic with silver nanoparticles in natural surface water
期刊: Science of The Total Environment
作者: Penghui Li, Jingfu Liu, Hongwu Zhang
摘要: The combined pollution induced by microplastics (MPs) and other pollutants, such as nanomaterials, has received increasing attention. The interaction between MPs and silver nanoparticles (AgNPs) may affect both their behaviors in natural environments, however, knowledge on these effects remains limited. In this study, AgNPs and three common MPs, polypropylene (PP), polyethylene (PE), and polystyrene (PS), were co-exposed to natural freshwater and brackish water to investigate the interaction between MPs and AgNPs in natural surface water. The results showed that the environmental behaviour of AgNPs in natural freshwater and brackish water is first of all affected by water chemistry and only in second instance affected by MPs. In natural freshwater, AgNPs remained stable largely dominated by dissolved organic matter (DOM), parts of which were subsequently captured by three MPs in the form of single particles without significant difference. In contrast, both ionic strength and DOM contributed to the aggregation of AgNPs in natural brackish water. PE and PP captured a small amount of AgNPs in the form of aggregates in natural brackish water, while the majority of AgNP aggregates were trapped by PS in natural brackish water. Therefore, both water chemistry and MPs types were found to play crucial roles in the interaction between MPs and AgNPs. These observations also revealed that MPs could serve as carriers for AgNP transport and advance the current understanding of combined pollution between MPs and engineered nanomaterials in natural aquatic environments.
42. 题目: The pH-sensitive Sorption Governed Reduction of Cr(VI) by Sludge Derived Biochar and the Accelerating Effect of Organic Acids
期刊: Journal of Hazardous Materials
作者: Ying-heng Fei, Manzhi Li, Zhuofeng Ye, Jieyang Guan, Zhenhong Huang, Tangfu Xiao, Ping Zhang
摘要: Reduction coupling immobilization is one of the most commonly adopted strategies for the remediation of Cr(VI) contamination. Biochar is a carbon-rich material with abundant active functional groups for sorption and reduction reactions. In previous reports, phytomass derived biochars and organic functional groups have been emphasized, while the performance of sludge derived biochar (SBC) has often been understated. In the present study, a 30 d kinetic study proved that the removal route involved the sorption of Cr(VI), reduction to Cr(III) and immobilization of Cr(III), and that the sorption process was the primary and rate determining step. As a result of the SBC alkalinity, the solution pH increased, and sorption was largely inhibited, which then governed the overall removal ratio. The FTIR spectra suggested the involvement of hydroxyls in these processes. Low molecular weight organic acids accelerated the removal process in the early phase and improved the reduction process.
43. 题目: Effects of arbuscular mycorrhizal fungi on crop growth and soil N2O emissions in the legume system
期刊: Agriculture, Ecosystems & Environment
作者: Ling Wang, Yunlong Liu, Xiangcheng Zhu, Yi Zhang, Huiyi Yang, Steven Dobbie, Xin Zhang, Aixing Deng, Haoyu Qian, Weijian Zhang
摘要: Arbuscular mycorrhizal fungi (AMF), which form symbiotic associations with 80% of land plants, provide host plants with soil phosphorus (P) and nitrogen (N) in exchange for carbon. The AMF often reduces nitrous oxide (N2O) emissions from soils with non-legume plants, as they acquire N from soils to plants. However, the effect of AMF on soil N2O emissions is still unknown in the legume system, a major source of this potent greenhouse gas. Therefore, we conducted the field and pot experiments to investigate the eﬀects of AMF on plant growth and soil N2O emissions in legume systems. The results showed that AMF significantly increased soil N2O emissions from soils with soybean by 39% in the field experiment and by 63% in the pot experiment. The AMF significantly enhanced the root biomass, aboveground biomass, grain yield, plant N uptake, plant P uptake, and the nodule numbers. The AMF increased soil extractable N concentrations and DOC concentrations, but reduced soil available P concentrations. The AMF stimulated the N2O-producing microbes (nirS- and nirK-type) whereas they did not affect the N2O-consuming (nosZ-type) denitrifiers. The AMF reduced the yield-scaled N2O emissions in the field experiment and increased the net ecosystem economic budget. Our findings indicate that AMF increase soil N2O emissions from legume system through enhancing P acquisition for biological N2 fixation and suggest that AMF benefit crop production for higher-yield with less N2O emissions.
44. 题目: Consistent mineral-associated organic carbon chemistry with variable erosion rates in a mountainous landscape
作者: Xiang Wang, Adrian A. Wackett, Brandy M. Toner, Kyungsoo Yoo
摘要: Interactions between organic carbon (OC) and minerals represent a critical mechanism for stabilizing organic matter in soils. Because both mineral weathering and plant productivity are negatively affected by soil erosion, mineral-associated organic carbon (MOC) chemistry is also expected to vary with erosion intensity. Here we show that MOC chemistry, determined by carbon X-ray absorption near-edge fine structure spectroscopy (XANES), exhibits little difference across a large (10-fold) gradient in erosion-derived soil turnover times. Mineral-associated OC chemistry further fails to explain the variation in radiocarbon-based MOC turnover times. Our results suggest that soil OC longevity is largely independent of organic matter chemistry in steep mountainous landscapes where soil development is constrained by erosion.
45. 题目: Cadmium and arsenic availability in soil under submerged incubation: The influence of humic substances on iron speciation
期刊: Ecotoxicology and Environmental Safety
作者: Bo Li, Qi-Hong Zhu, Quan Zhang, Han-Hua Zhu, Dao-You Huang, Shi-Ming Su, Ya-Nan Wang, Xi-Bai Zeng
摘要: Humic substances (HSs), as electron shuttles, are associated with iron oxide transformation, yet the manner by which HSs affect Cd/As availabilities during this process under anaerobic conditions remains unclear. Two HSs (humic sodium, HA-Na, and biochemical fulvic acid, BFA) were applied at 0, 1, 2, and 4 gCkg−1 in a submerged incubation experiment. The dissolved, extractable and fractions of Cd/As and different iron oxides in soils were monitored. The addition of both HA-Na and BFA decreased the CaCl2-extractable Cd by 12.66–93.13%, and increased the KH2PO4-extractable As by 18.81–71.38% on the 60th day of incubation. The soil Eh and crystalline iron oxides (Fed) decreased, while amorphous iron oxides (Feo) and dissolved As increased after addition of both HSs. However, the two HSs had opposite effects on soil pH and dissolved Cd at the end of the incubation. HA-Na immobilized 19.47–85.99% more available Cd than did BFA over the incubation, although the extent of immobilization was similar with the maximum application rate on the 60th day. BFA mobilized 5.22–26.12% more available As than did HA-Na. XPS data showed that FeOOH decreased while the FeO component increased over the incubation. Correlation analysis and SEM showed that the reduction in the soil Eh and Fed and relative increase in Feo increased the available Cd, while decreased the available As. Consequently, the addition of HA-Na and BFA, particularly combined with flooding irrigation management, could effectively reduce the available Cd in Cd-contaminated soil. However, this method should be used with caution in As-contaminated soil.
46. 题目: Effects of Artemisia ordosica on fine-scale spatial distribution of soil C, N and P and physical–chemical properties in the Mu Us Desert, China
期刊: Journal of Soils and Sediments
作者: Zhilong Lan, Shaolei Zhang, Liangchen Xie, Xiong Li, Tanveer Ali Sial, Abdu Ghaffar Shar, Jinglong Fan, Jianguo Zhang, Qiang Dong, Guangjun Fu
摘要: Purpose Vegetation restoration is an effective measure for improving the function of soil ecosystems and promoting the biogeochemical cycling of carbon (C), total nitrogen (TN) and total phosphorus (TP). Here, we aimed to quantify the fine-scale (pedon scale) spatial distribution of soil C, N, P and soil physical–chemical properties in the Mu Us Desert ecosystems. Methods We systematically evaluated the effects of A. ordosica on fine-scale (pedon scale) spatial distribution of C, TN, TP, soil-available nutrients, and liable organic carbon (LOC) and their stoichiometric characteristics in the semiarid Mu Us Desert in the 0–100-cm soil profiles at various distances from the plant. Results and discussion The results demonstrated that soil organic carbon (SOC), TN and LOC were decreased with increasing distance from the plant and soil depth. SOC stocks at 20 cm were 16.98% higher than those at 120 cm from the plant. SOC stocks at 20, 60 and 120 cm from the plant were increased by 71.62%, 58.14% and 46.72% compared with shifting sandy land (Sland), respectively. Microbial biomass carbon (MBC) and readily oxidised organic carbon (ROOC) were significantly affected by different soil layers and distances and their interaction (p < 0.05), whereas dissolved organic carbon (DOC) was affected by the soil layers. TN and soil-available nutrients in the surface layer and at closer distances to the plant were higher than those in the sublayer and Sland. The ratio of C:N:P was generally decreased with different distances from the plant and different soil layers. The ratios of soil C:N, C:P and N:P were significantly different at different soil layers, whereas the ratios of soil C:P and N:P were significantly different at different distances from the plant (p < 0.05). Soil C:P ratio was positively correlated with soil C:N and N:P ratios (p < 0.001). N and P contents in leaves were higher than those in roots, branches and litter, but C contents in leaves were lower than those in other plant tissues and litter (p < 0.01). N:P ratio in leaves (13.94) showed that there was a shortage of N and P in the Mu Us Desert ecosystems. Conclusions We concluded that A. ordosica could enhance the accumulation of SOC, LOC and N on a fine scale and improve mineral-nutrient availability in semiarid deserts and, as a result, the function of soil ecosystems could be improved. Moreover, the limitation of N and P can be alleviated by adding additional N and P.
47. 题目: Microbial necromass as the source of soil organic carbon in global ecosystems
期刊: Soil Biology and Biochemistry
作者: Baorong Wang, Shaoshan An, Chao Liang, Yang Liu, Yakov Kuzyakov
摘要: Despite the recognized importance of the contribution of microbial necromass to soil organic carbon (SOC) sequestration, at a global scale, there has been no quantification for cropland, grassland, and forest ecosystems. To address this knowledge gap, the contents of fungal and bacterial necromass were estimated based on glucosamine and muramic acid contents in cropland (986 samples), grassland (278 samples), and forest (452 samples) soils. On an average, microbial necromass C contributed 51%, 47%, and 35% to the SOC in cropland, grassland, and forest soils, respectively, in the first 20 cm of topsoil. The contribution of microbial necromass to SOC increased with soil depth in grasslands (from 47% to 54%) and forests (from 34% to 44%), while in croplands it decreased (from 51% to 24%). The microbial necromass accumulation coefficient (the ratio between necromass and living microbial biomass C) was higher in soil from croplands (41) and grasslands (33) than in forest (20) soils. These results suggest that the turnover of living microbial biomass is faster in grassland and cropland soils than in forest soils, where the latter contains more partially decomposed plant residues. Fungal necromass C (> 65% of total necromass) had consistently higher contributions to SOC than bacterial necromass C (32–36%) in all soils due to i) a larger living fungal biomass than bacterial biomass, and ii) fungal cell compounds being decomposed slowly and, thus able to persist longer in soil. The ratio of fungal:bacterial necromass C increased from 2.4 to 2.9 in the order of croplands < grasslands < forests, because fungi are the principal decomposers of complex substrates dominant in grassland and, especially, in forest soils. The ratios of bacterial:microbial necromass and bacterial:fungal necromass in cropland soils are larger than those in grassland and forest soils. This result indicates that the relative contribution of fungal necromass to total microbial necromass is lowest in cropland among the three land uses. Moreover, fungal and bacterial necromass increased with the total living microbial C and N contents. Meanwhile, lower temperatures and soil pH (e.g., in temperate and boreal ecosystems) were found to stimulate fungal and bacterial necromass accumulation. These findings highlight the fact that shifts in the bacterial:fungal necromass ratio and the microbial necromass contribution to SOC are ecosystem-specific. In conclusion, microbial necromass contributes to approximately half of the SOC in cropland and grassland soils, and only 35% in forest soils; whereas, two-thirds of microbial necromass is of fungal origin.
48. 题目: Effective destruction of perfluorooctanoic acid by zero-valent iron laden biochar obtained from carbothermal reduction: Experimental and simulation study
期刊: Science of The Total Environment
作者: Min Yang, Xiaolei Zhang, Yicheng Yang, Qiang Liu, Long D. Nghiem, Wenshan Guo, Huu Hao Ngo
摘要: This study investigated the degradation of perfluorooctanoic acid (PFOA) on zerovalent iron-laden biochar (BC-ZVI) prepared by carbothermal reduction. Results show that over 99% PFOA can be removed by BC-ZVI in hydrothermal conditions under 240 °C within 6 h. The maximum defluorination rate of 63.2% was achieved after 192 h, and this outcome was significantly better than biochar (BC) and zero-valent iron (ZVI) alone. The short-chain perfluorinated compounds (PFCs) and perfluoroheptanal were detected in the liquid phase after degradation, suggesting that the degradation of PFOAs by BC-ZVI followed the Kobel decarboxylation process. XRD and SEM-EDS analyses strongly suggested that carbothermal reduction could avoid the agglomeration of ZVI loaded onto biochar, which helped make the PFOA degradation more efficient. The frontier molecular orbital theory calculated by density functional theory revealed there were two possibilities for ZVI loading on BC (edged or internal loading), while the edge loaded ZVI had a greater tendency to provide electrons for the defluorination of PFOA than internally loaded ZVI.
49. 题目: Effects of fine bubble aeration at the sediment‒water interface on distributions of organic phosphorus fractions and related microbial activity in a heavily urban river
期刊: Journal of Soils and Sediments
作者: Changming Yang, Xiazhi Chen, Yunqi Xu, Yulai Wang
摘要: Purpose Effects of aeration on distribution and release potential of organic phosphorus in sediments are of great significance. The aim of this study was to investigate effects of fine bubble aeration at the sediment‒water interface on species distributions of organic phosphorus and related microbial activities in the sediments from Nanfei River, a seriously polluted urban river in Hefei City, Anhui Province, China. Materials and methods A simulation experiment with a precision oxygen distribution system with fine bubble was applied and the sediments in system were taken out at intervals to test various indicators, mainly including the contents of phosphorus, species distribution of organic phosphorus, microbial biomass (MBC), and alkaline phosphatase activity (APA), as well as the number of phosphate solubilizing bacteria. Results The results showed that the content of dissolved organic carbon (DOC) increased in the sediments, along with the decrease of pH and the significant increase of oxidation–reduction potential (ORP). The content of total phosphorus and inorganic phosphorus in the surface sediments generally presented a downward trend when the content of organic phosphorus increased first and then decreased during aeration. The variation trends of liable organic phosphorus and moderately labile organic phosphorus were similar to organic phosphorus, while the content of non-labile organic phosphorus was slightly decreased. In addition, the MBC and APA increased. The number of organic phosphorus mineralizing bacteria (OPB) increased while that of inorganic phosphorus solubilizing bacteria (IPB) decreased, and the number of OPB was significantly correlated to APA, which corresponds to the mineralization mechanism of organic phosphorus. Conclusions There were two stages of phosphorus transformation in the surface sediments during the aeration treatment: the stabilization of inorganic phosphorus in the early stage and the mineralization of organic phosphorus latterly, which means an increased risk of phosphorus release into the water in the late stage. Therefore, the fine bubble aeration treatment at the sediment‒water interface applied to controlling the internal pollution of water bodies should be considered, especially focusing on the strict control of the aeration time. Overall, the present study can provide scientific guidance for in situ remediation of heavily polluted sediments.
50. 题目: The effect of carbonization temperature on the capacity and mechanisms of Pb(II) adsorption by microalgae residue-derived biochar
期刊: Ecotoxicology and Environmental Safety
作者: Zijun Yang, Jun Hou, Jun Wu, Lingzhan Miao
摘要: This study investigated the adsorption characterizations and mechanisms of lead (Pb) on biochar-derived microalgae residue (MB) produced at different pyrolytic temperatures. Six different MB samples were prepared from Chlorella sp. (CB) and Spirulina sp. (SB) in the temperature range of 200–600 ℃, and microalgae residue power (MP) was used as a control. The effect of pH, adsorption kinetics and isotherms were studied for the different MBs, and a chemical analysis of Pb2+-loaded MP and MB was performed by SEM-EDS, XRD, XPS, FTIR, and Boehm titration. The results showed that Pb2+ adsorption on MP and MB was a monolayer chemical adsorption process. Precipitation with minerals, metal ion exchange, oxygen/nitrogen-containing functional groups (OFGs/NFGs), and coordination of Pb2+ with π electrons jointly contributed to Pb2+ adsorption on MP and MB. More specifically, the contribution of each mechanism depended on the pyrolytic temperature. The contribution of surface complexation and ion exchange decreased with increasing pyrolytic temperature due to the loss of OFGs/NFGs and decreasing metal ion content, while the contribution of precipitation and Pb2+-π interaction significantly increased. Overall, precipitation with minerals and ion exchange dominated Pb2+ adsorption on MP and MB, which accounted for 65.20–74.40% of the total adsorption capacity. Surface precipitation contributed to a maximum adsorption capacity for high-temperature CB and SB (600 ℃) of up to 131.41 mg/g and 154.56 mg/g, respectively. In conclusion, MB adsorbents are a promising material for the remediation of heavy metal-bearing aquatic environments.
51. 题目: Sources and main controls of dissolved organic and inorganic carbon in river basins: a worldwide meta-analysis
期刊: Journal of Hydrology
作者: Vincent Chplot, Macdex Mutema
摘要: Despite dissolved carbon (C) exports from continents being crucial in the connection between terrestrial, atmospheric and oceanic C pools, the relative contribution and process controls on dissolved organic (DOC) and inorganic (DIC) fluxes within river basins are not fully understood. This paper presents an analysis of data from 843 sites worldwide from 45 Web of Science SCI-Expanded (ex ISI) indexed papers that report both the DOC and DIC contents and fluxes in conjunction with chemical elements, such as Si, Na and 13C abundance, to investigate the likely origin, pathways and fate of the dissolved C. The reviewed papers also report on selected environmental factors (e.g., MAP and MAT: mean annual precipitation and temperature respectively; Climate, LU: land use, A: basin surface area). Regarding dissolved C fluxes rivers transported on average, 8.4 GT C yr-1 of dissolved C with 7.7 GT C yr-1 (92%) being DIC and remaining (8%) DOC. Asia has the highest within-river dissolved C transport (5.8 GT C yr-1) followed by Europe (2.0 GT C yr-1), America (0.4 GT C yr-1), and Africa (0.1 GT C yr-1). The dissolved C fluxes tend to increase with river water fluxes and contribution of interflow as seen in the tropical climate, which results in the export of relatively fresh DOC with low aromaticity. In contrast, the lower river water fluxes in sub-tropical and temperate climates corresponds to high concentration of comparatively more decomposed DOC, which pointed to a high proportion of groundwater contribution to the water fluxes. The results also imply that surface area and morphology of the river basins, as well as land use, has insignificant impact on dissolved C dynamics. Such quantitative results, including on the important role of climate on the dynamics of dissolved C in river basins, are helpful in improving predictions on the impact of climate change on the global C cycle. New and innovative multidisciplinary research on the subject is called for.
52. 题目: Response of soil respiration and Q10 to temperature and moisture in naturally regenerated and bare lands based on an 11-year observation period
作者: Junxia Yan, Ya Feng, Junjian Li, Hongjian Li, Guangwei Ding
摘要: Although correlations between soil respiration (Rs) and environmental factors in different ecosystems have been extensively investigated, results based on long-term experiments are limited. In this study, we analyzed the correlations between Rs and soil temperature (Ts), moisture (θ), the normalized difference vegetation index (NDVI), and soil organic matter (SOM) based on an 11-year field campaign in abandoned farmland (HD) and bare land (LD) areas with a Cambisol soil type in the eastern Loess Plateau of China. The results showed that the mean annual Rs and annual temperature sensitivity (Q10) values in HD were significantly larger than those in LD during the measurement period. Rs and the annual contribution ratio (Rratio) of root respiration (Rr) to Rs in HD increased significantly with vegetation recovery years. On the annual scale, Rs was controlled primarily by Ts at both sites. However, in the summer months, Rs was controlled by θ rather than Ts. A two-variable model, including Ts and θ, could more accurately predict the temporal variations in Rs at the annual and seasonal time scales than a single-variable model, and the explanatory power of the equations in HD was significantly larger than that in LD. On the interannual scale, variations in the annual Rs and Rr showed significant positive correlations with the annual θ and NDVI and SOM, and negative correlations with Ts in HD. Moreover, the annual Q10 was significantly positively related to θ in HD. In LD, the only significant relationship was between the annual Q10 and the annual θ. All differences between HD and LD in Rs, Ts, and θ and their correlations were attributed to differences in vegetation. Our findings highlight the importance of long-term observations for the accurate estimation of CO2 efflux in semiarid regions and the impact of vegetation changes on soil respiration.
53. 题目: Straw and straw biochar differently affect phosphorus availability, enzyme activity and microbial functional genes in an Ultisol
期刊: Science of The Total Environment
作者: Caidi Yang, Shenggao Lu
摘要: Crop straw is commonly returned back to agricultural fields to improve soil nutrient status. In order to compare the effects of straw returning modes (direct and carbonization returning) on the phosphorus (P) availability in acidic soils and explore possible chemical and microbial mechanisms, a pot experiment was conducted. The rice straw, canola stalk at the rate of 1% (w/w) and their corresponding biochar produced by the same amount of straw at 350 °C and 550 °C were used, and two-season crops (rice and soybean) were planted. Results indicated that the content of available P in biochar-treated soils was significantly higher than in the straw-treated soils owing to the biochar soluble P and increased pH. Straw returning increased the activities of urease, sucrase and catalase more than biochar. Biochar mode significantly increased the activity of alkaline phosphatase (ALP), while decreased the acid phosphatase (ACP) relative to the straw mode. Likewise, there were a significant rise in the copy number of phoD gene and a drop of phoC in the biochar mode. The P functional genes (phoD, gcd and pqqC) had the higher copy numbers in soils with biochar made at 350 °C. Similarly, biochar made at 350 °C improved the yields of rice and soybean more effectively. Therefore, straw returning modes affected the availability of P differently via chemical and microbial pathways and the ALP regulated by phoD played a crucial role in the conversion of P. Results demonstrated that biochar returning had a larger impact on the availability of P and developed the effectiveness of crop production than the straw returning directly.
54. 题目: Secretion of sulfated fucans by diatoms may contribute to marine aggregate formation
期刊: Limnology and Oceanography
作者: Guoyin Huang, Silvia Vidal‐Melgosa, Andreas Sichert, Stefan Becker, Yang Fang, Jutta Niggemann, Morten Hvitfeldt Iversen, Yi Cao, Jan‐Hendrik Hehemann
摘要: Microalgae produce copious amounts of structurally diverse polysaccharides, some are bound within cells and cell walls, while others are secreted into the surrounding seawater. A fraction of the secreted polysaccharides assembles into particles promoting aggregation and in turn formation of aggregates increases the export of carbon into the deep ocean via sinking. However, specific polysaccharides contributing to particle formation and carbon export remain unknown. Here, we studied microalgae polysaccharide composition in a system of reduced complexity consisting of lab grown monospecific cultures of the centric diatom species Thalassiosira weissflogii and Chaetoceros socialis. We followed the abundance and dynamics of five specific polysaccharide types in the dissolved and particulate organic matter (DOM and POM) for two weeks. Polysaccharides were detected using monoclonal antibodies (mAbs) specific for β-1,4-mannan, β-1,4-xylan, arabinogalactan, and two fucose-containing sulfated polysaccharide (FCSP) epitopes. Additionally, glycan composition of all samples was analyzed by monosaccharide analysis. The time series revealed polysaccharides partition differently between the dissolved and particulate carbon pools. β-1,4-xylan and β-1,4-mannan were mainly present in POM, possibly as cell wall polymers, while FCSPs were found in both DOM and POM. The data showed that the main glycan component secreted by diatoms was fucose-containing polysaccharide, which accumulated in DOM over time. Roller tank experiments were used to induce aggregate formation finding FCSP transitioned from DOM to POM under aggregating conditions. These results suggest that diatom-secreted FCSPs are involved in the formation of aggregates, which promote the formation of particles, and potentially carbon export.
55. 题目: Biochar-induced reduction of N2O emission from East Asian soils under aerobic conditions: Review and data analysis
期刊: Environmental Pollution
作者: Sun-Il Lee, Hyun-Jin Park, Young-Jae Jeong, Bo-Seong Seo, Jin-Hyeob Kwak, Hye In Yang, Xingkai Xu, Shuirong Tang, Weiguo Cheng, Sang-Sun Lim, Woo-Jung Choi
摘要: Global meta-analyses showed that biochar application can reduce N2O emission. However, no relevant review study is available for East Asian countries which are responsible for 70% of gaseous N losses from croplands globally. This review analyzed data of the biochar-induced N2O mitigation affected by experimental conditions, including experimental types, biochar types and application rates, soil properties, and chemical forms and application rates of N fertilizer for East Asian countries. The magnitude of biochar-induced N2O mitigation was evaluated by calculating N2O reduction index (Rindex, percentage reduction of N2O by biochar relative to control). The Rindex was further standardized against biochar application rate by calculating Rindex per unit of biochar application rate (ton ha−1) (Unit Rindex). The Rindex averaged across different experimental types (n = 196) was −21.1 ± 2.4%. Incubation and pot experiments showed greater Rindex than column and field experiments due to higher biochar application rate and shorter experiment duration. Feedstock type and pyrolysis temperature also affected Rindex; either bamboo feedstock or pyrolysis at > 400 °C resulted in a greater Rindex. The magnitude of Rindex also increased with increasing biochar rate. Soil properties did not affect Rindex when evaluated across all experimental types, but there was an indication that biochar decreased N2O emission more at a lower soil moisture level in field experiments. The magnitude of Rindex increased with increasing N fertilizer rate up to 500–600 kg N ha−1, but it decreased thereafter. The Unit Rindex averaged across experimental types was −1.2 ± 0.9%, and it was rarely affected by experimental type and conditions but diminished with increasing biochar rate. Our results highlight that since N2O mitigation by biochar is affected by biochar application rate, Rindex needs to be carefully evaluated by standardizing against biochar application rate to suggest the best conditions for biochar usage in East Asia.
56. 题目: Synthesis of ultralight chitosan/activated biochar composite aerogel globules for ketoprofen removal from aqueous solution
期刊: Separation and Purification Technology
作者: Jian Chen, Jinbo Ouyang, Weixin Lai, Xiaohong Xing, Limin Zhou, Zhirong Liu, Wenqian Chen, Di Cai
摘要: A novel non-template method was used to prepare ultralight composite aerogel globules that were exploited for the removal of anti-inflammatory drug ketoprofen (KTP) from aqueous solution. The composite aerogel globules were synthesized by freeze-drying and characterized with FESEM, BET, FTIR, XRD and Zeta potential. Swelling behavior of these aerogel globules was strongly affected by the solution pH. The results showed that the presence of 10% activated biochar (ABC) in chitosan (CS), which was named CS-ABC2, was the most desirable aerogel globules as it had high mechanical property and remarkable sorption performance. The sorption kinetics and isotherms of KTP onto composite aerogel globules were studied in detail. In addition, the effects of ion strength and regeneration on sorption performance were investigated, indicating decent environment tolerance, complete recovery rate and excellent reusability of the composite aerogel globules. The composite aerogel globules also exhibited other outstanding advantages such as biodegradability, economy and ease of separation.
57. 题目: Charred plant fragment‐aluminium complexes in buried humic horizons of a cumulative volcanic soil profile: Formation, accumulation and potential role
期刊: European Journal of Soil Science
作者: Haruo Shindo, Yudzuru Inoue
摘要: The objective of the present study was to investigate the formation, accumulation and potential role of charred plant fragment (CPF)-aluminium (Al) complexes in several buried A (Ab) horizons of a cumulative volcanic soil profile, focusing on CPFs, active Al components and soil age. Nineteen soil samples were collected from four buried humic horizons (2A–5A, from 7.3 cal ka BP to AD 1471), and their CPF-carbon (C), soil organic C (SOC), acid oxalate-extractable Al (Alox), pyrophosphate-extractable Al (Alpy, Al-humus complexes) and short-range ordered Al minerals (Alox−Alpy) were quantified. The proportion of CPF-C content (up to 15.8 g kg−1) to SOC content (up to 117 g kg−1) ranged from 2.3 to 15.1% (8.4% on average). The contents of active Al components (6.71–77.1 g kg−1) increased: Alpy < Alox−Alpy < Alox. No consistent trends with age were found for the accumulation levels of CPF-C, SOC and active Al components. However, the significant positive correlations (p < .001) were found between the Alpy and CPF-C and SOC contents, suggesting that the accumulation and stabilization of soil organic matter in these humic layers proceeded simultaneously with the formation of organo-Al complexes, including CPF-Al complexes. On the other hand, the significant negative correlations (p < .01) were obtained between the Alox−Alpy and Alpy, CPF-C or SOC contents. From these correlations, it was assumed that the complexation of organic constituents, including CPFs, with Al competed with the synthesis of short-range ordered Al minerals (including allophane and imogolite), irrespective of soil age and climatic conditions with the range of more than 6,000 yrs. This competitive relationship in the presence of CPFs was first described in the current study.
58. 题目: Decomposing the Oxygen Signal in the Ocean Interior: Beyond Decomposing Organic Matter
期刊: Geophysical Research Letters
作者: Nicolas Cassar, David Nicholson, Samar Khatiwala, Ellen Cliff
摘要: At depth, O2 depleted because of organic matter remineralization is generally estimated based on apparent oxygen utilization (AOU). However, AOU is an imperfect measure of oxygen utilization because of O2 air-sea disequilibrium at the site of deep-water formation. Recent methodological and instrumental advances have paved the way to further deconvolve processes driving the O2 signature. Using numerical model simulations of the global ocean, we show that measurements of the dissolved O2/Ar ratio, which so far have been confined to the ocean surface, can provide improved estimates of oxygen utilization, especially in regions where the disequilibrium at the site of deep-water formation is associated with physical processes. We discuss applications of this new approach and implications for current tracers relying on O2 such as remineralization ratios, respiratory quotients and preformed nutrients. Finally, we propose a new composite geochemical tracer, [O2]*bio combining dissolved O2/Ar and phosphate concentration. Being insensitive to photosynthesis and respiration, the change in this new tracer reflects gas exchange at the air-sea interface at the sites of deep-water formation.
59. 题目: Comparative study on polychlorinated biphenyl sorption to activated carbon and biochar and the influence of natural organic matter
作者: Yanmei Zhou, Dingjie Miao, Jose L. Gomez-Eyles, Upal Ghosh, Mengyuan Bi, Jiuyi Li, Fumin Ren
摘要: The sorption isotherms of polychlorinated biphenyls (PCBs) on carbons (coal based activated carbon named AC and hardwood derived biochar named BC) and natural organic matter (NOM) loaded carbons were examined and carbon-water partition coefficients (KC-W-PCB) were calculated. The purpose was to accurately predict the effectiveness of in-situ carbon treatments on the sediment impacted with hydrophobic organic chemicals (HOCs). For 1 month sorption, AC KC-W-PCB values were significantly higher than BC, corresponding to the much larger surface area (particularly in mesopores) for AC. BC KC-W-PCB values were correlated with PCB total surface area (TSA) and octanol-water partition coefficient (logKow). After loading with NOM, AC adsorption to PCBs strongly reduced and the fitted Freundlich exponents (n) decreased with increasing NOM level. However, NOM loading slightly impacted BC sorption and exhibited an opposite effect on BC n values. It is illustrated that the sorption mechanisms are different between AC and BC thereby the influences of NOM on sorption characteristics differ vastly. As the sorption time increased from 1 month to 6 months, an increase is observed in BC sorption extent but simultaneously NOM reduction effect on BC sorption increases, implying that more accurately evaluating BC application as an in-situ sorbent amendment for HOC impacted sediment need further investigation. On the contrary, AC adsorption attenuation caused by NOM coating greatly decreases over time, encouraging AC application as a sediment amendment.
60. 题目: Grassland degradation with saline-alkaline reduces more soil inorganic carbon than soil organic carbon storage
期刊: Ecological Indicators
作者: Tongtong Xu, Minna Zhang, Shiwen Ding, Bai Liu, Qing Chang, Xuan Zhao, Ying Wang, Jianyong Wang, Ling Wang
摘要: Grassland is an important part of terrestrial ecosystems and contain substantial amounts of soil carbon. However, 90% of grasslands suffer from degradation in northern China, where soil inorganic carbon (SIC) is a major reservoir. Previous studies have focused primarily on soil organic carbon (SOC) stock, while the effects of grassland degradation in SIC stock remains largely unexplored. Therefore, accurate assessments of both SOC and SIC stocks and their profile distributions are necessary to fully understand the role of grassland degradation in China’s carbon budget. Here, we conducted an experiment to estimate the stocks, profile distributions, and environmental controls of both SOC and SIC in patchy saline-alkaline grasslands under three degraded degrees (non-degraded patches, ND; moderately degraded patches, MD, and heavily degraded patches, HD). Our results showed that grassland degradation destroys not only SOC but also SIC stocks in saline-alkaline grasslands. SIC is the main component of soil carbon in saline-alkaline grasslands, and their distributions changed dramatically. Compared with ND, SIC losses caused by degradation accounted for 84% and 86% of total carbon loss under MD and HD patches, respectively. SIC loss primarily occurred at the intermediate soil layers (30–70 cm), while the loss of SOC was mainly in the topsoil (0–40 cm). Moreover, the distributions of SIC from 20 to 60 cm were closely related to soil pH, while it is mainly regulated by EC from 60 to 100 cm. In addition, soil pH, EC, and above-ground biomass were important variables driving the profile distributions of SOC in the upper soil. Our work provides evidence that grassland degradation mainly damages the SIC stocks. Our findings, therefore, highlight the non-negligible role of SIC dynamics in the carbon budget of degraded grassland ecosystems and the need to consider these dynamics in terrestrial carbon cycle research.