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24561. 题目: Impact of biogenic emissions of organic matter from a cool-temperate forest on aerosol optical properties
文章编号: N20032015
期刊: Atmospheric Environment
作者: Astrid Müller, Kazuma Aoki, Eri Tachibana, Tsutom Hiura, Yuzo Miyazaki
更新时间: 2020-03-20
摘要: Terrestrial biogenic emissions of organic matter can affect the optical properties of atmospheric aerosols and thus impact the radiation budget. To investigate this, the chemical parameters of submicrometer water-soluble aerosols (WSA) collected on filters were compared to optical properties measured by a sky radiometer at a cool-temperate forest site in northern Japan. From June to December 2015, the WSA samples were collected within the forest canopy, while aerosol optical depth (AOD), single scattering albedo (SSA), absorption Ångström exponent (AAE), and scattering Ångström exponent (SAE) were retrieved above the canopy. The optical properties were compared with the filter-based chemical parameters only when the vertical transport of aerosol particles from the forest canopy to the air above it was significant. The result showed that the AOD and the mass concentrations of WSA exhibited similar and distinct seasonal variations with peaks in summer and autumn. In summer, sulfate accounted for 60% of the mass of WSA, which was linked to a high SSA (>0.95), low AAE (1.15 ± 0.84), and low SAE (1.25 ± 0.22). In contrast, water-soluble organic matter (WSOM) accounted for 70% of the mass of WSA in autumn. This large fraction of WSOM was associated with a decrease in SSA (0.90–0.95) and an increase in AAE (2.45 ± 0.91) and SAE (1.46 ± 0.15). The results suggest that in summer, aerosol particles with a greater size range corresponded to aerosol chemical compositions dominated by sulfate. In contrast, smaller particles with a strong light absorption at shorter wavelengths, were likely important in autumn and associated with a composition dominated by WSOM. The majority of WSOM in autumn has previously been associated with emissions of α-pinene from the forest floor and the subsequent formation of biogenic secondary organic aerosols (BSOA). This study indicates that α-pinene-derived SOAs, mostly originating from the forest floor, were associated with a summer to autumn decrease in SSA. This process can modulate the radiative effect on a regional scale.

24562. 题目: Organic carbon fractional distribution and saturation in tropical soils of West African savannas with contrasting mineral composition
文章编号: N20032014
期刊: CATENA
作者: Salifou Traoré, Lamourdia Thiombiano, Babou André Bationo, Ingrid Kögel-Knabner, Martin Wiesmeier
更新时间: 2020-03-20
摘要: Savannas are dry tropical biomes characterized by high above- and belowground biomass production, but at the same time there is extensive C loss by fire regimes. Soil-mediated responses are crucial in biogeochemical cycling and the role of soil minerals may be important in controlling organic carbon (OC) storage and stabilization. The objective of this study was to determine OC fractional distribution and saturation capacity in three soil groups (Vertisols, Lixisols, Luvisols) that are characterized by specific and different 1:1 and 2:1 clay mineral dominance. For each soil group, top- and subsoils (0–10 cm, 40–60 cm) were sampled in protected Soudanian savannas across Burkina Faso and fractionated into free and aggregate-occluded particulate organic matter (fPOM, oPOM) and mineral-associated organic matter (mOM). The results showed that oPOM and mOM were significantly affected by soil groups and topsoil/subsoil layers. We consider this to be due to interactions with fine particles (clay, fine and medium silt), the presence of exchangeable Ca and Mg and extractable Al (D) and Fe (D) as revealed by significant positive correlations. We found that oPOM (13–29% of total OC) and mOM < 20 µm (54–76%) were the most important OC pools in these tropical savanna soils. Vertisols exhibited the highest OC contents and held three times more OC in the fine mineral fraction mOM < 20 µm than Lixisols and Luvisols. Luvisols were affected by mineral illuviation processes which lowered their OC contents. Overall, topsoils contained three times higher OC amounts of mOM < 20 µm than subsoils. Indications were found that all investigated topsoils are below OC saturation, likely due to prescribed fire and soil erosion effects, while the OC saturation deficit was important in Vertisols (−49 to −65%) and Lixisols (−41 to −45%). We conclude that tropical savanna soils have a high protective capacity for OC in top- and subsoils but require adequate management in order to increase OC storage.

24563. 题目: Temporal change in soil physicochemical, microbial, aggregate and available C characteristic in dry tropical ecosystem
文章编号: N20032013
期刊: CATENA
作者: Pratap Srivastava, Rishikesh Singh, Rahul Bhadouria, Sachchidanand Tripathi, Akhilesh Singh Raghubanshi
更新时间: 2020-03-20
摘要: The holistic understanding of soil C dynamics with age of organic amendment is limited in dry tropical ecosystems, which may act as potential C sink if managed properly. Therefore, we studied soil physicochemical, microbial, aggregate and available C characteristic with age organic amendment across the season for mechanistic understanding of soil C accumulation. Organic systems under 1, 3, 5 and 10 years under organic amendment were selected along with a forest system as reference for this purpose. We observed that soil organic C and CO2 efflux (SCE) increased significantly after ten years of organic amendment (though with no change in SCE on unit C basis), and approached closer to reference forest site. Soil fine particles, moisture content, ammonium-N, ammonium-N/nitrate-N ratio (ANR), microbial biomass C, N and C/N, crude dehydrogenase, glucosidase and phosphomonoesterase activity, macro- and mesoaggregate, mean weight diameter, macroaggregate water stability, and total and labile C concentration and carbon management index across aggregate fractions significantly increased with age. However, soil nitrate-N, C/N ratio, water soluble C, specific glucosidase and phosphomonoesterase activity, microaggregate and mineral fraction decreased. The seasonality of total and labile C concentration and stock differed distinctly across aggregate size fraction, which showed its linkage with microbial and plant C input dynamics. Though, total and labile C stock increased across aggregate fractions with age, it shifted towards macro-and mesoaggregate, opposite to smaller size fractions. Macro-aggregate stability along with macro-aggregate labile C, dehydrogenase activity, microbial biomass C/N and mesoaggregate C majorly determined the SOC. However, specific glucosidase activity along with mesoaggregate, ammonium/nitrate ratio and microbial biomass majorly governed the SCE. The study indicates that macro-aggregate characteristic (including mesoaggregate) play a crucial role in soil C accumulation in dry tropical ecosystem under organic amendment, with microbial community characteristics and ANR. Moreover, the study indicates towards key role of macro-mesoaggregate equilibrium and inorganic N dynamics in the soil C dynamics of the studied ecosystems, in which seasonality and C input play a crucial role.

24564. 题目: Mid- to Late Holocene Paleoclimatic Changes and Paleoenvironmental Shifts Inferred from Pollen and Diatom Assemblages at Lake Hamra, Wadi El Natrun (Western Nile Delta, north Western Desert, Egypt)
文章编号: N20032012
期刊: Quaternary International
作者: Amr S. Zaky, Kaoru Kashima, Fabrizio Frontalini, Mohamed I.A. Ibrahim, Moataz M. Khalifa, Yu Fukumoto, Dina Gad, Hermann Behling
更新时间: 2020-03-20
摘要: Four palynological and three diatom zones of Mid- to Late Holocene are identified along a 370-cm-long radiocarbon dated sediment core collected in Lake Hamra at Wadi El Natrun (Western Nile Delta, Egypt). The Mid- Late Holocene between the Predynastic to Old Kingdom was terrestrial wetland habitat with high seasonal rainfall and/or Nile flood as revealed by the dominance of Cyperaceae pollen. Therefore, people gathered in and around the Nile Valley and the agricultural activities increased. During the early stage of Late Holocene coincident with the Old Kingdom to Middle Kingdom, the paleoclimate became more arid with low seasonal precipitation and/or Nile flood as reflected by the increasing abundance of Poaceae pollen and the absence of diatoms in addition to low values of TOC, TN, TS, C/S and high values of C/N. These drought conditions possibly played a role in the Old Kingdom collapsing. The late stage of the Late Holocene showed terrestrial wetland habitat with brackish conditions coupled with aquatic contribution under oxic conditions as inferred by the dominance of Typha sp. and Amaranthaceae pollens as well as the diatom assemblages. The relatively high values of TOC, C/N, C/S coupled with low values of TS and TN reveal terrestrial origin of organic matter. The Late Holocene-recent has turned into a terrestrial wetland habitat with more brackish conditions and increasing in the seasonal rainfall as supported by the marked increasing of Cyperaceae pollen. The overall increase of the Diatom Inferred Salinity (DIS) as well as the marked increasing of C/S, TN and decreasing of TOC, C/N and TS values towards the recent point to higher saline brackish wetland paleoenvironment and a terrestrial origin of the organic matter with more aquatic contribution under oxic conditions.

24565. 题目: Effects of plant roots and arbuscular mycorrhizas on soil phosphorus leaching
文章编号: N20032011
期刊: Science of The Total Environment
作者: Cuc T.K. Tran, Stephanie J. Watts-Williams, Ronald J. Smernik, Timothy R. Cavagnaro
更新时间: 2020-03-20
摘要: While the impact of arbuscular mycorrhizal fungi (AMF) on phosphorus (P) uptake is well understood, the mechanism(s) of how these fungi affect P leaching from soil is still unclear. Here we present results of a study in which we grew a mycorrhiza-defective tomato (Solanum lycopersicum L.) genotype (named rmc) and its mycorrhizal wild-type progenitor (named 76R) in microcosms containing non-sterile soil, to examine the influence of roots and AMF on P leaching. More P was leached from the planted microcosms as compared to the plant-free controls. Further, although there was more plant biomass and greater P uptake in the mycorrhizal plant treatments, these treatments were associated with the most leaching of total P, reactive P, and dissolved organic carbon (DOC). There was a strong correlation between the total P and DOC leached, suggesting that root and fungal exudates may have affected P leaching. These findings provide new insights into the impact of roots and AMF on nutrient leaching in soils.

24566. 题目: Vegetation and soil responses to added carbon and nutrients remain six years after discontinuation of long-term treatments
文章编号: N20032010
期刊: Science of The Total Environment
作者: Na Liu, Anders Michelsen, Riikka Rinnan
更新时间: 2020-03-20
摘要: Global warming and increased nutrient availability in the Arctic have attracted wide attention. However, it is unknown how an increased supply of nitrogen (N), phosphorus (P) and/or labile carbon (C) – alone and in combinations – affects the concentrations and pools of C and nutrients in plants, soil and soil microorganisms, and whether the cessation of these additions allows the ecosystem to recover from amendments. Six treatments (control, C, N, P, NP and C + NP) were applied at a subarctic heath for 8–10 years. After being untreated for two years, amendments were re-applied to one half of the plots for four years while the other plot half received no amendments. When the plots were harvested, we could therefore compare responses in plots with nearly continuous 14–16-year amendments to those with six years with discontinued treatments. The responses to individual and combined nutrient additions were mostly similar in re-initiated and discontinued plots. Individual N addition strongly increased the C and N pools in the graminoids, thereby also increasing the C and N pools in litter and fine roots compared to the plots without added N. This contributed to the increased microbial biomass C and total C in soil. P addition alone increased C and N pools in vascular cryptogams, as well as PO43−, NH4+, dissolved organic carbon and dissolved organic nitrogen concentrations in soil compared to the plots without added P. Hence, plant functional groups showed differential responses to long-term N and P amendment, and after the initial nutrient additions for 8–10 years, the investigated subarctic tundra ecosystem had reached a new steady state that was resilient to further changes still six years after cessation of additions.

24567. 题目: Green synthesis of a novel Mn–Zn ferrite/biochar composite from waste batteries and pine sawdust for Pb2+ removal
文章编号: N20032009
期刊: Chemosphere
作者: Zhirui Niu, Wenli Feng, Hua Huang, Bo Wang, Lan Chen, Yibo Miao, Shuai Su
更新时间: 2020-03-20
摘要: Magnetic ferrite/biochar composites are a kind of promising adsorbents due to their high adsorption efficiency and facile magnetic separation; however, their synthesis is associated with high cost and secondary environmental impacts. In this study, a novel Mn–Zn ferrite/biochar composite (MZF-BC) is synthesized via a green two-step biocheaching and hydrothermal method using waste batteries and pine sawdust. Characterization results indicate that the introduced Mn–Zn ferrite particles are successfully embedded and coated on biochar (BC), and synthesized MZF-BC50 with 50% BC content exhibits best performance with a specific surface area of 138.5 m2 g−1, the saturation magnetization of 27.5 emu g−1 and CEC value of 53.2 mmol 100 g−1. The maximum adsorption capacity of Pb2+ is 99.5 mg g−1 based on the Langmuir sorption isotherm study at 298 K, and pseudo-second-order model accurately describes the adsorption process. Regeneration test suggests that MZF-BC50 can be efficiently reused for 6 cycles. In addition, it exhibits a good selective Pb2+ and Cd2+ removal performance in lead-acid battery wastewater. The results illustrate that this newly developed material has low cost and rapid remediation of Pb2+ as good application potential.

24568. 题目: Insight into conditioning landfill sludge with ferric chloride and a Fenton reagent: Effects on the consolidation properties and advanced dewatering
文章编号: N20032008
期刊: Chemosphere
作者: Xudong Zhang, Yitian Lu, Jie Yao, Yajun Wu, Quoc Cong Tran, Vu Quoc Vuong
更新时间: 2020-03-20
摘要: The landfill sludge in storage reservoirs needs to be dewatered and disposed of for environmental and engineering purposes. The key factors are the high organic matter content and low permeability. Chemical conditioning is considered an efficient method for adjusting the properties of sludge. In this paper, two typical chemical agents, FeCl3 and a Fenton reagent with different additive amounts, are studied and compared for dewatering and consolidation purposes. Compression experiments and consolidation experiments are compared, and the coefficient of compressibility and compression index are obtained and compared. Then, the sludge permeability, grain size distribution variations, specific resistance to filtration (SRF) and morphology observations are considered to analyse the treatment mechanism. The results indicate that the properties of landfill sludge will change as the curing time increases. FeCl3 and Fenton are both effective in improving the consolidation and permeability properties of sludge. For the conditioning process, the optimum FeCl3 content is 20%, and the process is dominated by coagulation if FeCl3 is less than 20%; otherwise, it is dominated by hydrolysis. For the Fenton reagent, the optimum Fe2+ content and H2O2 content are 4% and 12%, respectively. The depolymerization effect of the Fenton reagent leads to the oxidation and recombination of the polar group on extracellular polymeric substances (EPSs). The results can be used to explain the conditioning mechanism of the effective agents of FeCl3 and Fenton and compare the corresponding consolidation properties. The consolidation characteristics provide a reference for further application of vacuum preloading in the sludge disposal process.

24569. 题目: Use of biochar to produce reclaimed water for irrigation use
文章编号: N20032007
期刊: Chemosphere
作者: Sandeep Reddy Yanala, Krishna R. Pagilla
更新时间: 2020-03-20
摘要: Emerging contaminants, especially, pharmaceutical and personal care products (PPCPs) are not removed well during conventional wastewater treatment and hence pose water quality risk to the environment and potentially to public health. Long-term use of reclaimed wastewater for irrigation can lead to accumulation of trace contaminants in the soil, ground water and their subsequent uptake by plants and potentially can enter human food chain. This paper uses biochar as an adsorbent to remove emerging contaminants from treated wastewater by performing fixed bed experiments. Ten emerging contaminants namely, carbamazepine (CBZ), caffeine, diethyltoluamide (DEET), diphenhydramine (DPH), meprobamate (MPB), primidone (PMD), sulfamethoxazole (SMX), fluoxetine (FXT), perfluorooctanoic acid (PFOA) and trimethoprim (TMP) were monitored during lab scale experiments. Results from the continuous flow runs showed that the breakthrough curve for compounds caffeine, CBZ, DEET and PFOA follow second order Thomas model with adsorption capacities of 396 μg g−1, 392 μg g−1, 1160 μg g−1 and 32 μg g−1 biochar, respectively. Whereas compounds such as DPH, TMP and FXT were completely removed throughout the column runs by biochar. Results for rest of the compounds were interfered by leaching of these compounds from biochar. It was observed that commercially available GAC performed much better than biochar for all the compounds considered. Even at 1% of obtained capacity, biochar amendment to soils where reclaimed water is used for irrigation can reduce the uptake of these compounds by plants.

24570. 题目: A novel calcium-based magnetic biochar reduces the accumulation of As in grains of rice (Oryza sativa L.) in As-contaminated paddy soils
文章编号: N20032006
期刊: Journal of Hazardous Materials
作者: Jizi Wu, Zhangtao Li, Lu Wang, Xingmei Liu, Caixian Tang, Jianming Xu
更新时间: 2020-03-20
摘要: The present study used calcium-based magnetic biochar (Ca-MBC), a novel material made through pyrolyzing rice straw impregnated with iron oxide (Fe3O4) and calcium carbonate (CaCO3) under oxygen-limited conditions, to reduce arsenic (As) accumulation in rice plants (Oryza sativa L.) through a 130-day pot experiment. The BCR (European Community Bureau of Reference) sequential extraction confirmed that Ca-MBC decreased the unstable fraction of As through transforming to the stable fraction at both tillering stage and maturity. The addition of Ca-MBC decreased while the pristine biochar increased the concentrations of NH4H2PO4- and BCR-extracted As. The μ-XRF test revealed that iron oxide on the Ca-MBC played an important role in decreasing As bioavailability. The addition of Ca-MBC greatly decreased As concentration in rice grains, mainly due to (1) the decreases in bioavailability of As in soil and (2) adsorption of As in pore water by Ca-MBC; and (3) the enhanced formation of iron plaque that acted as a barrier for plant As uptake. Furthermore, the addition of Ca-MBC at 1% but not 2% promoted plant growth. The results suggest that Ca-MBC can be used as an efficient material to lower As accumulation in grains and promote plant growth in rice paddy fields.

24571. 题目: Evaluating soil and nutrients (C, N, and P) loss in Chinese Torreya plantations
文章编号: N20032005
期刊: Environmental Pollution
作者: Xiongwen Chen, Pengfei Xiao, Jianzhi Niu, Xi Chen
更新时间: 2020-03-20
摘要: Improper land-use changes may lead to a loss of soil resources and cause environmental pollution. Chinese Torreya plantation (hereafter CTP) is an important cash tree plantation for nuts production in the mountainous areas of subtropical China. The increasing development of CTPs, to increase seed production, can result in the complete erasure of local natural vegetation. In this study, the vulnerability to soil erosion, loss of soil organic carbon (SOC) and nutrients in CTPs due to land-use change were evaluated. The results indicated that the rates of diffusive soil erosion in the young CTPs with extreme precipitation were about six-fold higher than with the natural vegetation. At sites with a similar slope, there was no significant difference in soil erosion levels between the young and old CTPs. The old CTPs did not hold significantly higher levels of SOC and soil total nitrogen (STN) in their topsoil when compared with the young CTPs. The natural mixed broadleaved subtropical forests lost about 35% of their SOC and 25% of their STN after they were converted into CTPs, but the CTPs had higher soil total phosphorus. The C: N ratios at the different sites were close to 11:1, but the N: P ratios were diverse. There were high levels of organic carbon, nitrogen and phosphorus in stream water. Adequate coverage of natural vegetation within or around the CTPs should be maintained to decrease soil erosion and nutrient loss. Suggestions to develop CTPs while protecting the environment are discussed. Overall, it was determined that aspects of the current management practices and strategies for developing CTPs should be changed to decrease soil erosion and nutrient loss.

24572. 题目: Frequency but not amount of stover mulching orchestrates the decomposition pathways of soil micro-foodwebs in a no-tillage system
文章编号: N20032004
期刊: Soil Biology and Biochemistry
作者: Xinchang Kou, Ningning Ma, Xiaoke Zhang, Hongtu Xie, Xudong Zhang, Zhengfang Wu, Wenju Liang, Qi Li, Howard Ferris
更新时间: 2020-03-20
摘要: In the decomposition pathways of the soil micro-foodweb, resource-transfer links between bacteria, fungi and microbivorous nematodes are extremely important for the transformation and cycling of soil organic carbon and for the quality, productivity and sustainability of soil ecosystems. However, the changes in organic decomposition pathways in response to different amounts and frequencies of stover mulching are less clear. Here, we investigate the responses of the soil micro-foodweb to maize stover mulching amounts (33% and 67% amounts of all harvest stover) and frequencies (high frequency with continuous mulching per year and low frequency with interval mulching every three years) in a 10-year no-tillage mulching experiment. The frequency but not the amount of stover mulching had significant effects on soil microorganism and nematode communities. Greater bacterial PLFAs and their higher correlation with bacterivores were observed in high mulch-frequency treatments while in low frequency treatments fungal PLFAs and their correlations with fungivores were higher. The increased nematode enrichment footprint in high frequency treatments indicated more carbon flow into soil micro-foodweb, while a higher structure footprint in low frequency treatments suggested the development of a relatively stable soil micro-foodweb. We conclude that trophic interactions regulate decomposition pathways in a binary coupling between bacteria and nematodes at high input frequencies and between fungi and nematodes at low input frequencies. The structure and activity of the pathways are determined by the bottom-up effects of different stover mulching frequencies.

24573. 题目: Adsorption of organic contaminants on biochar colloids: effects of pyrolysis temperature and particle size
文章编号: N20032003
期刊: Environmental Science and Pollution Research
作者: Rashida Hameed, Cheng Lei, Daohui Lin
更新时间: 2020-03-20
摘要: Biochar (BC) colloids attract increasing interest due to their unique environmental behavior and potential risks. However, the interaction between BC colloids and organic contaminants that may affect their fates in the environment has not been substantially studied. Herein, adsorption and desorption of phenanthrene (PHN), atrazine (ATZ), and oxytetracycline (OTC) by a series of BC colloids derived from bulk rice straw BC samples with 6 pyrolysis temperatures (200–700 °C), and 3 particle sizes (250 nm, 500 nm, and 1 μm) were investigated. Regardless of pyrolysis temperature, BC colloids from a given sized bulk BC had a comparable size, being 30 ± 6, 70 ± 18, and 140 ± 15 nm corresponding to the three sized bulk BCs, respectively. The adsorption kinetics curves were well explained by the pseudo-second-order model, and pore diffusion was the primary rate-determining step. Both Freundlich and Langmuir models well fitted the adsorption isotherms. With increasing pyrolysis temperature or decreasing particle size of bulk BC, the specific surface area and pore volumes of the derived BC colloids increased, the kinetics model fitted adsorption rates (k2) of the three organics by the BC colloids all largely decreased, and the Langmuir model fitted adsorption capacities (Qmax) increased. The highest Qmax was obtained by BC colloids from the smallest (250 nm) bulk BC with the highest pyrolysis temperature (700 °C), being 212 μmol g−1 for PHN, 815 μmol g−1 for ATZ, and 72.4 μmol g−1 for OTC. The adsorption was reversible for PHN and ATZ, while significant desorption hysteresis was observed for OTC on BC colloids with middle pyrolysis temperatures (300–500 °C). The underlying mechanisms including hydrophobic interaction, π–π electron donor-acceptor interaction, molecular size effect, and irreversible reactions were discussed to explain the difference in the adsorption and desorption behaviors. The findings increased our understanding of the environmental fate and risk of BC.

24574. 题目: Soil carbon dynamics in Indian Himalayan intensified organic rice-based cropping sequences
文章编号: N20032002
期刊: Ecological Indicators
作者: Subhash Babu, Raghavendra Singh, R.K. Avasthe, Gulab Singh Yadav, K.P. Mohapatra, Thiru Selvan, Anup Das, Vinod K. Singh, Donatella Valente, Irene Petrosillo
更新时间: 2020-03-20
摘要: The contribution of soil to supporting, regulating, provisioning and cultural functions as well as its role in the ecosystem services is well-known in the international literature. However, in the domain of organic agriculture, the impact of cropping systems shifts from cereal-cereal to high-frequency diversified cropping sequences with legume as a component crop on soil carbon dynamics is not widely known. In order to identify an alternative cropping system to widely prevalent rice-fallow production system in Himalayan region of India, seven cropping sequences viz., rice -fenugreek (green vegetable) - maize (R-F-M); rice -vegetable pea - maize (R-Vp-M); rice-coriander (leaves)-cowpea (R-C-Cp); rice - fenugreek (green vegetable) - baby corn (R-F-Bc); rice - broccoli - Sesbania (green manuring) (R-B-S); rice - buckwheat (R-Bw) and rice - maize (R-M) were assessed for five consecutive years from 2013 to 2018 for their productivity and resource conservation values. Results revealed that the inclusion of legumes in rice-based sequences increased the rice grain yield by 13.4 to 24.6% over R-M (3.13 Mg ha−1) sequence. The R-B-S sequence had the highest very labile carbon (VLC) (4.6 g kg−1 soil) followed by the R-Vp-M. Relative proportion of various organic carbon fractions in the top 10 cm soil followed the order of VLC (30.2%) > non labile carbon (NLC, 27.6%) > labile carbon (LC, 23.4%) > less labile carbon (LLC, 18.9%). The carbon management index (CMI) was the highest (100.9%) in the R-B-S sequence followed by R-C-Cp (98.0%). The addition of a third crop in the sequence increased the active carbon (AC) pool by 1.1 to 5.8%. The passive carbon (PC) pool was highest in soil under the R-C-Cp sequence (9.15 Mg ha−1) at 0–10 cm soil depth. The carbon retention efficiency under the R-C-Cp cropping sequence was the highest (15.1%) followed by the R-B-S (14.9%). R-B-S and R-C-Cp sequences had 12.5% and 10.6% higher soil microbial biomass carbon (SMBC) over the R-M sequence, respectively. Similarly, R-B-S and R-C-Cp increased the FDA by 49.6 and 41.8%, and DHA by 135.0% and 103.9%, respectively over R-M sequence. In conclusion, the management of crops from organic agriculture aimed at improving soil ecosystem services, in contrasting degradation of soil health and the decline of SOC, can also have positive effects on crop productivity in the eastern Himalayan region of India as well as all over the world.

24575. 题目: Soil organic carbon increase in semi-arid regions of China from 1980s to 2010s
文章编号: N20032001
期刊: Applied Geochemistry
作者: Tao Yu, Yesi Fu, Qingye Hou, Xueqi Xia, Beizhan Yan, Zhongfang Yang
更新时间: 2020-03-20
摘要: Soil carbon plays a key role in agriculture and ecosystem. Semi-arid regions cover many parts of China, holding a carbon pool that should not be ignored. Thus, systematic studies of the carbon distribution and variation in semi-arid regions are necessary. In this study, we comprehensively analyzed the factors that influence the distribution and variation in soil carbon covering area over 0.92 × 106 km2. Results indicated that the average values of soil organic carbon density (at the soil sampling depth of 0–20 cm) in the study area were 0.58–4.50 kg/m2. Soil organic carbon density (SOCD) was clearly related with climate conditions (e.g., temperature and precipitation), soil properties (e.g., pH and soil texture) and human activities. The results revealed a significant negative relationship between SOCD and temperature. Meanwhile, SOCD showed positive relationship with precipitation. Correlation analysis also demonstrated a negative correlation between SOCD and soil pH, but positively associated with soil Al:Si ratio. Land utilization and fertilization would also affect SOCD in the regions. Upon comparing the current data with that of the 1980s, soil organic carbon storage presented a remarkable increasing trend with 2.55 Tg in these studied regions due to land use change. These findings would provide evidences and insights for the future land managements of semi-arid regions of China in the context of global climate change.

24576. 题目: Light absorption of brown carbon in PM2.5 in the Three Gorges Reservoir region, southwestern China: Implications of biomass burning and secondary formation
文章编号: N20031918
期刊: Atmospheric Environment
作者: Chao Peng, Mi Tian, Xiaoliang Wang, Fumo Yang, Guangming Shi, Ru-Jin Huang, Xiaojiang Yao, Qiyuan Wang, Chongzhi Zhai, Shumin Zhang, Ruozhi Qian, Junji Cao, Yang Chen
更新时间: 2020-03-19
摘要: Brown carbon (BrC) is known as a light-absorbing organic aerosol which affects the visibility and radiative forcing budget in the troposphere. The optical properties were studied for filter-based PM2.5 samples collected from the winter of 2015 to the summer of 2016 at one rural and three urban sites in the Three Gorges Reservoir (TGR) region, China. The average light absorption coefficient for BrC (βabs, 405,BrC) at 405 nm and its contributions to total aerosol light absorption during winter were 12.1 ± 7.0 Mm−1 and 23.8 ± 9.1% respectively, higher than those during summer (1.7 ± 0.8 Mm−1 and 11.2 ± 4.1%). Spatially, the average βabs,405,BrC was higher at the urban sites (13.4 ± 7.3 Mm−1) than that at the rural site (7.8 ± 3.2 Mm−1). The average mass absorption efficiency of BrC at 405 nm (MAE405,BrC) was 0.8 ± 0.4 m2 g−1 during winter which was 2.7 times higher than that during summer (0.3 ± 0.1 m2 g−1). Furthermore, the absorption Ångström exponents (AAE) at 405–980 nm (AAE405−980) were 1.1 ± 0.1 in summer and 1.3 ± 0.2 in winter respectively. Correlation analysis suggests that biomass burning (BB) played an important role in βabs,405,BrC during winter. Additionally, the relatively high AAE405−980 during winter was mainly due to the BrC from both BB and secondary organic aerosol. The fractional contribution of solar energy absorption by BrC relative to BC in the wavelengths of 405–445 nm was 23.9 ± 7.8% in summer and 63.7 ± 14.2% in winter, significantly higher than that in the range of 405–980 nm (11.9 ± 3.4% and 29.9 ± 6.1% respectively). Overall, this study contributes to the understanding of sources of BrC in the climate-sensitive TGR region of southwestern China.

24577. 题目: Agroforestry boosts soil health in the humid and sub-humid tropics: A meta-analysis
文章编号: N20031917
期刊: Agriculture, Ecosystems & Environment
作者: Mary N. Muchane, Gudeta W. Sileshi, Sofia Gripenberg, Mattias Jonsson, Lorena Pumariño, Edmundo Barrios
更新时间: 2020-03-19
摘要: Agroforestry has been increasingly recognized as a key example of agroecological praxis contributing to the sustainable intensification of food production while providing a number of additional benefits to society. However, a quantitative synthesis of the impact of agroforestry on soil health and associated ecosystem services in the humid and sub-humid tropics is still lacking. The objective of this study was to quantify the contribution of agroforestry practices to soil-mediated ecosystem services, specifically, regulation of soil erosion, storage of soil organic carbon (SOC) and nitrogen (N), availability of soil N and phosphorus (P) to crops, and alleviation of soil acidity across the humid and sub-humid tropics. The analysis demonstrated that agroforestry can reduce soil erosion rates by 50 % compared to crop monocultures. This finding is supported by higher infiltration rates, lower runoff, higher proportion of soil macroggregates, and greater stability of soil structure under agroforestry. SOC increased by 21 %, N storage increased by 13 %, available N by 46 % and available P by 11 % while soil pH increased by 2% under agroforestry compared to crop monocultures. We conclude that agroforestry can make significant contributions to provision of soil-mediated ecosystem services in the humid and sub-humid tropics.

24578. 题目: Changes in soil micro- and macro-aggregate associated carbon storage following straw incorporation
文章编号: N20031916
期刊: CATENA
作者: Dangwei Pang, Jin Chen, Min Jin, Haoyu Li, Yongli Luo, Wenqian Li, Yonglan Chang, Yong Li, Zhenlin Wang
更新时间: 2020-03-19
摘要: Inadequate soil management strategies weaken soil quality. Soil aggregates and aggregate-associated soil organic carbon (SOC) are important attributes of the soil and can serve as indicators of changes in soil quality. The objective of this study was to optimize an improved soil management that slowed turnover of aggregates and increased SOC storage in Northern China. Four tillage methods were examined: (i) RT (rotary tillage without straw return), (ii) RS (rotary tillage with straw return), (iii) DS (deep tillage with straw return), and (iv) TS (RS applied annually and with DS applied at a two-year interval). The results indicated that straw return treatments increased macroaggregate formation and sequestrated greater SOC. The C inputs among RS, DS, and TS were similar in magnitude, ranging from 8.86 to 8.99 t ha−1 year−1. Compared to RS, DS enhanced the turnover of macroaggregates in the 0–20 cm layers, and led to more SOC loss in occluded microaggregates than in macroaggregates in the 0–30 cm layers, indicating a reduced protection of aggregates to SOC. Similar to DS, the mass of macroaggregates under TS was greater than RS in the 10–30 cm layers. However, TS increased the SOC storage in macroaggregates by 0.66 and 0.90 t ha−1 in the 0–30 cm layers, respectively, compared to RS and DS. Moreover, the SOC storage in occluded microaggregates under TS was 0.52 and 1.06 t ha−1 greater than RS and DS, respectively, in the 0–30 cm layers. SOC variations among treatments in this study were dominated by tillage methods; thus, appropriate soil disturbance in deep layers (TS) has great potential in activating more C sequestration in macroaggregates and occluded microaggregates. These findings are of great importance for formulating soil management strategy and probably beneficial for crop production.

24579. 题目: On-line recovery system coupled to a Rock-Eval® device: An analytical methodology to characterize liquid and solid samples
文章编号: N20031915
期刊: Organic Geochemistry
作者: Pierre Cadeau, Maria-Fernanda Romero-Sarmiento, Olivier Sissmann, Valérie Beaumont
更新时间: 2020-03-19
摘要: The Rock-Eval® device has been widely used to identify the type and the thermal maturity of sedimentary organic matter as well as quantifying the total organic carbon content. Traditionally, it is a screening tool to estimate the petroleum generation potential of source rocks using standardize parameters. More recently, a new Rock-Eval® method (Shale PlayTM) was proposed to investigate the hydrocarbon content in liquid-rich tight rock samples. In this study, we describe a dual vacuum and on-line system that was developed to recover most compounds that are thermally released during a Rock-Eval® Shale PlayTM analysis. Thermally vaporized products are divided so that half is analyzed by the Rock-Eval® flame ionization detector (FID) while the other portion is cryogenically trapped in the on-line recovery system. The trapped products can then be transferred via a vacuum line system into a sample vial for subsequent molecular and/or isotopic composition analyses. The recovery vacuum line volumes were calibrated using known quantities of gas (CH4 and CO2). Sample transfer from without isotopic fractionation was demonstrated for CO2 evolved from Rock-Eval® preparation of pure carbonate standards (siderite, magnesite and azurite). Recovery efficiencies were first measured on C8-C16 n-alkane standards and then on produced oil samples. Results indicate a high quantitative recovery and an accurate mass balance of most compounds released during the Shale PlayTM Sh0 thermovaporization step (100-200°C). Thermally vaporized compounds released at higher temperatures Sh1 (200-350°C) are recovered at lower efficiencies but are still suitable for subsequent characterization. The coupled Rock-Eval® and recovery system could have applications beyond petroleum geochemistry.

24580. 题目: Bio-reduction of ferrihydrite-montmorillonite-organic matter complexes: Effect of montmorillonite and fate of organic matter
文章编号: N20031914
期刊: Geochimica et Cosmochimica Acta
作者: Qiang Zeng, Liuqin Huang, Jinyu Ma, Zihua Zhu, Chen He, Quan Shi, Wen Liu, Xi Wang, Qingyin Xia, Hailiang Dong
更新时间: 2020-03-19
摘要: Organic matter (OM) is often associated with Fe (hydr)oxides such as ferrihydrite (Fh) in soils and sediments, forming binary Fh-OM complexes. Microbial reduction of Fh results in destabilization of the complexes and mineral/OM transformation. However, little is known about the role of clay minerals in such processes, despite their common co-existence with Fh and OM in natural environments. Here Fh-OM complexes were synthesized in the presence of montmorillonite (SWy-2), forming ternary Fh-(SWy-2)-OM complexes. A metal-reducing bacterium Geobacter sulfurreducens was used to reduce Fh in the complexes under circumneutral pH and anoxic conditions with or without H2 as extra electron donor. Various spectroscopy and mass spectrometry methods were used to monitor the progress of Fh bio-reduction and mineral/OM transformation. Results showed that G. sulfurreducens utilized mineral-bound OM as electron donor and/or carbon source to couple with Fh reduction. Relative to Fh-OM complex, Addition of SWy-2 to Fh-OM complex enhanced the bio-reduction extent of Fh by increasing the proportion of bioavailable OM that was weakly bound to SWy-2. However, its effect on the bio-reduction rate was variable. SWy-2 initially decreased the rate, because it spatially separated OM (electron donor) from Fh (electron acceptor). During later incubation, SWy-2 increased the reduction rate by sorbing biogenic Fe2+ that would otherwise passivate the Fh and cell surfaces. Bio-reduction transformed mineral-bound OM to microbial products (e.g. necromass, extracellular polymeric substances), but organic compounds with aromatic structures, carboxyl groups and large molecular weight were more resistant to desorption and oxidation. The persistence of these compounds against bio-reduction induced transformation is likely due to their stronger binding with minerals and/or lower nominal oxidation states of carbon relative to other compounds. Our results provide new insights into the role of clay minerals in regulating biogeochemical cycling of solid-phase Fe and transformation of mineral-associated OM in anoxic soil environments.