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24801. 题目: Sulfur-modified biochar as a soil amendment to stabilize mercury pollution: An accelerated simulation of long-term aging effects
文章编号: N20050806
期刊: Environmental Pollution
作者: Bin Zhao, David O’Connor, Zhengtao Shen, Daniel C.W. Tsang, Jörg Rinklebe, Deyi Hou
更新时间: 2020-05-08
摘要:

The stability of mercury (Hg) contamination in soil environments can change over time. This has implications for agricultural sites under long-term management after in situ treatment involving soil amendments. In this study, rice husk biochar (RHB) and sulfur modified rice husk biochar (SRHB) were synthesized and applied (dosage = 5% dry wt.) to a Hg polluted agricultural soil collected from Guizhou province, Southern China (soil total Hg content = 28.3 mg/kg; C = 2%; and, S = 0.1%). The long-term stabilization effectiveness of the soil treatments was evaluated by a combined approach involving: (i) accelerated aging for 104 simulated years; (ii) soil extraction as a proxy for plant uptake; and, (iii) sequential extraction to identify Hg fractions. The SRHB amendment raised the soil's total S content by approximately an order of magnitude (to 0.9%), which remained at a generally constant level throughout the simulation. The initial pH levels for the untreated and treated soils were alkaline and remained between 7.0 and 7.5 for the first 50 years of simulated aging, before decreasing as the simulation time increased further. The pH of the SRHB treated soils did not drop below that of untreated soils during the simulation. Soil extraction tests with 0.1 M HCl solution indicated that RHB and SRHB treatments could effectively immobilize the Hg in soil for at least 50 and 75 simulated years, respectively. At simulated year 50, the amount of Hg extracted from RHB and SRHB treated soils was <200 ng/L and <100 ng/L, respectively. Thus, showing SRHB to be a particularly promising remedial option. The soil Hg was mostly associated with the stable sequential extraction fractions (F3-5). By the end of the simulation, the F5 fraction for SRHB and RHB treated soils reduced by 44.6%, and 42.0%, respectively, whereas the F4 fraction increased by >400% in both cases. In summary, SRHB may provide long-lasting Hg stabilization at contaminated sites. Therefore, further research toward the development of this stabilization technology is warranted.

24802. 题目: Characteristics of carbon mineralization and accumulation under long-term conservation tillage
文章编号: N20050805
期刊: Catena
作者: Zheng-Rong Kan, Ahmad Latif Virk, Cong He, Qiu-Yue Liu, Jian-Ying Qi, Yash Pal Dang, Xin Zhao, Hai-Lin Zhang
更新时间: 2020-05-08
摘要:

Conservation tillage has been widely practiced to increase soil organic carbon (SOC), and reducing SOC mineralization has the potential to improve accumulation. To assess the effects of conservation tillage on characteristics of SOC mineralization and accumulation, as well as their relationship, a site experiment was established in 2008 using data from 2012 to 2019 under wheat-maize cropping system. Four treatments were investigated: no-till with straw retention (NTS, conservation tillage), no-till with straw removal (NT), conventional tillage with straw incorporation (CTS), conventional tillage with straw removal (CT). The results showed that NTS significantly improved SOC concentration than the other treatments at 0–10 cm soil depth (P < 0.05) by 5–18% in 2012 and 31–93% in 2019 (increasing increments over time). There was a negative correlation (R² = -0.60) between SOC concentration and mineralizability. On average, the SOC mineralizability under NTS was 39.0 mg C kg⁻¹ SOC at 0–10 cm depth, significantly lower than CTS and CT (P < 0.05). Furthermore, relative SOC mineralizability of NT/NTS, CTS/NTS, and CT/NTS was>1 and showed a linear relationship with time, indicating that NTS can increase SOC accumulation by reducing SOC mineralizability over time. A negative correlation was observed between SOC mineralizability and mean weight diameter (MWD) (R² = -0.34), and the highest MWD under NTS, suggesting reduced mineralizability due to enhanced physical protection of soil macro-aggregates. Furthermore, the particulate organic carbon (POC) concentration was highly correlated with MWD (R² = 0.76). Conclusively, results elucidated that higher POC under conservation tillage contributed to the macro-aggregate formation and aggregate stability at 0–10 cm depth, and thus protected SOC from mineralization, and additional SOC sequestration could be accelerated by improving the duration of conservation tillage.

24803. 题目: Using CO 2 as an Oxidant in the Catalytic Pyrolysis of Peat Moss from the North Polar Region
文章编号: N20050804
期刊: Environmental Science & Technology
作者: Taewoo Lee, Sungyup Jung, Jinkyu Hong, Chi-Hwa Wang, Daniel S Alessi, Sang Soo Lee, Young-Kwon Park, Eilhann E. Kwon
更新时间: 2020-05-08
摘要: As global warming and climate change become perceived as significant, the release of greenhouse gases (GHGs) stored in the earth's polar regions is considered a matter of concern. Here, we focused on exploiting GHGs to address potential global warming challenges in the north polar regions. In particular, we used CO2 as a soft oxidant to recover energy as syngas (CO and H2) and to produce biochars from pyrolysis of peat moss. CO2 expedited homogeneous reaction with volatile matters from peat moss pyrolysis, and the mechanistic CO2 role resulted in the conversion of CO2 and peat moss to CO at ≥530 °C. Steel slag waste was then used as an ex situ catalyst to increase reaction kinetics, addressing the issue of the role of CO2 being limited to ≥530 °C, with the result where substantial H2 and CO formation was achieved at a milder temperature. The porosity of biochars, a solid peat moss pyrolysis product, was modified in the presence of CO2, with a significant improvement in CO2 adsorption capacity compared to those achieved by N2 pyrolysis. Therefore, CO2 has the potential to serve as an initial feedstock in sustainable biomass-to-energy applications and biochar production, mitigating atmospheric carbon concentrations.

24804. 题目: Millennial-scale hydroclimate control of tropical soil carbon storage
文章编号: N20050803
期刊: Nature
作者: Christopher J. Hein, Muhammed Usman, Timothy I. Eglinton, Negar Haghipour, Valier V. Galy
更新时间: 2020-05-08
摘要: The storage of organic carbon in the terrestrial biosphere directly affects atmospheric concentrations of carbon dioxide over a wide range of timescales. Within the terrestrial biosphere, the magnitude of carbon storage can vary in response to environmental perturbations such as changing temperature or hydroclimate1, potentially generating feedback on the atmospheric inventory of carbon dioxide. Although temperature controls the storage of soil organic carbon at mid and high latitudes2,3, hydroclimate may be the dominant driver of soil carbon persistence in the tropics4,5; however, the sensitivity of tropical soil carbon turnover to large-scale hydroclimate variability remains poorly understood. Here we show that changes in Indian Summer Monsoon rainfall have controlled the residence time of soil carbon in the Ganges–Brahmaputra basin over the past 18,000 years. Comparison of radiocarbon ages of bulk organic carbon and terrestrial higher-plant biomarkers with co-located palaeohydrological records6 reveals a negative relationship between monsoon rainfall and soil organic carbon stocks on a millennial timescale. Across the deglaciation period, a depletion of basin-wide soil carbon stocks was triggered by increasing rainfall and associated enhanced soil respiration rates. Our results suggest that future hydroclimate changes in tropical regions are likely to accelerate soil carbon destabilization, further increasing atmospheric carbon dioxide concentrations.

24805. 题目: Two years of post-wildfire impacts on dissolved organic matter, nitrogen, and precursors of disinfection by-products in California stream waters
文章编号: N20050802
期刊: Water Research
作者: Habibullah Uzun, Randy A. Dahlgren, Christopher Olivares, Cagri Utku Erdem, Tanju Karanfil, Alex T. Chow
更新时间: 2020-05-08
摘要:

We investigated the effects of two California wildfires (Rocky and Wragg Fires, 2015) compared to an unburned reference watershed on water quality, dissolved organic matter (DOM), and precursors of disinfection by-products (DBPs) for two years' post-fire. The two burned watersheds both experienced wildfires but differed in the proportion of burned watershed areas. Burned watersheds showed rapid water quality degradation from elevated levels of turbidity, color, and suspended solids, with greater degradation in the more extensively burned watershed. During the first year's initial flushes, concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonium (NH₄⁺/NH₃), and specific ultraviolet absorbance (SUVA₂₅₄) were significantly higher (67 ± 40%, 418 ± 125%, 192 ± 120%, and 31 ± 17%, respectively) in the more extensively burned watershed compared to the reference watershed. These elevated values gradually declined and finally returned to levels like the reference watershed in the second year. Nitrate concentrations were near detection limits (0.01 mg-N/L) in the first year but showed a large increase in fire-impacted streams during the second rainy season, possibly due to delayed nitrification. Changes in DOM composition, especially during the initial storm events, indicated that fires can attenuate humic-like and soluble microbial by-product-like (SMP) DOM while increasing the proportion of fulvic-like, tryptophan-like, and tyrosine-like compounds. Elevated bromide (Br⁻) concentrations (up to 8.7 μM]) caused a shift in speciation of trihalomethanes (THMs) and haloacetic acids (HAAs) to brominated species for extended periods (up to 2 years). Wildfire also resulted in elevated concentrations of N-nitrosodimethylamine (NDMA) precursors. Such changes in THM, HAA, and NDMA precursors following wildfires pose a potential treatability challenge for drinking water treatment, but the effects are relatively short-term (≤1 year).

24806. 题目: Iron-mediated organic matter decomposition in humid soils can counteract protection
文章编号: N20050801
期刊: Nature Communications
作者: Chunmei Chen, Steven J. Hall, Elizabeth Coward, Aaron Thompson
更新时间: 2020-05-08
摘要: Soil organic matter (SOM) is correlated with reactive iron (Fe) in humid soils, but Fe also promotes SOM decomposition when oxygen (O2) becomes limited. Here we quantify Fe-mediated OM protection vs. decomposition by adding 13C dissolved organic matter (DOM) and 57FeII to soil slurries incubated under static or fluctuating O2. We find Fe uniformly protects OM only under static oxic conditions, and only when Fe and DOM are added together: de novo reactive FeIII phases suppress DOM and SOM mineralization by 35 and 47%, respectively. Conversely, adding 57FeII alone increases SOM mineralization by 8% following oxidation to 57FeIII. Under O2 limitation, de novo reactive 57FeIII phases are preferentially reduced, increasing anaerobic mineralization of DOM and SOM by 74% and 32‒41%, respectively. Periodic O2 limitation is common in humid soils, so Fe does not intrinsically protect OM; rather reactive Fe phases require their own physiochemical protection to contribute to OM persistence.

24807. 题目: Permafrost thawing puts the frozen carbon at risk over the Tibetan Plateau
文章编号: N20050713
期刊: Science advances
作者: Taihua Wang, Dawen Yang, Yuting Yang, Shilong Piao, Xin Li, Guodong Cheng, Bojie Fu
更新时间: 2020-05-07
摘要: Soil organic carbon (SOC) stored in permafrost across the high-latitude/altitude Northern Hemisphere represents an important potential carbon source under future warming. Here, we provide a comprehensive investigation on the spatiotemporal dynamics of SOC over the high-altitude Tibetan Plateau (TP), which has received less attention compared with the circum-Arctic region. The permafrost region covers ~42% of the entire TP and contains ~37.21 Pg perennially frozen SOC at the baseline period (2006–2015). With continuous warming, the active layer is projected to further deepen, resulting in ~1.86 ± 0.49 Pg and ~3.80 ± 0.76 Pg permafrost carbon thawing by 2100 under moderate and high representative concentration pathways (RCP4.5 and RCP8.5), respectively. This could largely offset the regional carbon sink and even potentially turn the region into a net carbon source. Our findings also highlight the importance of deep permafrost thawing that is generally ignored in current Earth system models.

24808. 题目: A critical review on arsenic removal from water using biochar-based sorbents: The significance of modification and redox reactions
文章编号: N20050712
期刊: Chemical Engineering Journal
作者: Rabia Amen, Hamna Bashir, Irshad Bibi, Sabry M. Shaheen, Nabeel Khan Niazi, Muhammad Shahid, Muhammad Mahroz Hussain, Vasileios Antoniadis, Muhammad Bilal Shakoor, Samir G. Al-Solaimani, Hailong Wang, Jochen Bundschuh, Jörg Rinklebe
更新时间: 2020-05-07
摘要:

Biochar is considered to be the cost-effective, environmentally-friendly and sustainable sorbent that has an extraordinary potential to efficiently remove toxic elements, including arsenic (As) from water. Until now, no review has focused to understand various important and intriguing aspects on biochar use as a sorbent for As removal from water, either pristine or modified. This review discusses various factors governing As removal potential of biochars (e.g., pH, biochar dose and physico-chemical properties of biochar), sequestration mechanisms, fate of sorbed As on biochar and the redox-mediated interactions between biochar and As. The significance of biochar-derived materials for the treatment of As-contaminated drinking water/wastewater and their potential regeneration ability is also critically discussed, which has not been previously elaborated. This comprehensive review article could be greatly valuable for scientists, policymakers, water treatment industries, environmentalists and graduate students, who are involved in biochar-As research. The review covers some new overarching and key scientific opportunities for the remediation of As-contaminated water using biochar-based materials, which is a potential health risk to millions of people worldwide.

24809. 题目: Integrated process for membrane fouling mitigation and organic pollutants removal using copper oxide modified ceramic hollow fiber membrane with in-situ peroxymonosulfate activation
文章编号: N20050711
期刊: Chemical Engineering Journal
作者: Songxue Wang, Jiayu Tian, Zhihui Wang, Qiao Wang, Jialin Jia, Xiujuan Hao, Shanshan Gao, Fuyi Cui
更新时间: 2020-05-07
摘要:

A novel CuO modified ceramic hollow fiber membrane for in-situ peroxymonosulfate (PMS) activation was developed and employed in surface water treatment. The performance of membrane fouling control and organic pollutants removal was systematically investigated. The results indicated that compared with pristine membrane, CuO modified ceramic hollow fiber membrane significantly improved the removal of dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV₂₅₄) in surface water. The removal rate increased with the increase of CuO loading content because of the reduction of the membrane surface pore size, but declined with the increase of PMS dosage due to the degradation products of incomplete mineralization passing through the membrane. The fluorescent compounds in surface water were efficiently removed by the CuO modified ceramic hollow fiber membrane and enhanced with the increase of PMS dosage and CuO loading content. The CuO modified ceramic hollow fiber membrane with in-situ PMS activation exhibits excellent antifouling property to natural organic matter (NOM) in surface water. Both the reversible and irreversible fouling decreased with the increase of PMS dosage while the membrane fouling would be slightly intensified with increased loading of CuO on the membrane, suggesting the trade-off relation between PMS dosage and CuO loading content. In addition, the degradation efficiency of organic pollutants in surface water was dramatically enhanced by the CuO modified ceramic hollow fiber membrane via incorporation of in-situ PMS oxidation process. High removal performance after five cycles of experiments showed the superior stability and reusability of the CuO modified ceramic hollow fiber membrane.

24810. 题目: Organic amendment increases soil respiration in a greenhouse vegetable production system through decreasing soil organic carbon recalcitrance and increasing carbon-degrading microbial activity
文章编号: N20050710
期刊: Journal of Soils and Sediments
作者: Haoan Luan, Wei Gao, Shaowen Huang, Jiwei Tang, Mingyue Li, Huaizhi Zhang, Xinping Chen, Dainius Masiliūnas
更新时间: 2020-05-07
摘要: Purpose Recent works have shown that fertilization has an important influence on soil respiration (Rs); however, the underlying mechanisms involved in regulating Rs in greenhouse vegetable production (GVP) systems remain unclear. Materials and methods Samples from six kinds of soils that were amended with different fertilization patterns (8 years) were incubated for 36 days to determine soil microbial community (PLFA), enzyme activities, soil organic C (SOC) quality (13C NMR), and Rs in a GVP system in Tianjin, China. Treatments included 100% chemical N (CN) and different substitution rates of CN with manure-N and/or straw-N. Results and discussion Compared with 100%CN treatment, organic amendment strongly promoted microbial (e.g., fungi, bacteria, and actinomycetes) growth, enhanced the majority of C-degrading enzyme activities, affected SOC chemical composition with increasing O-alkyl (labile) C and reducing aromatic (stable) C, decreased SOC recalcitrance, and enhanced Rs. Redundancy analysis indicated that variations in microbial community and SOC chemical composition were closely linked to light fraction organic C (LFC) and readily oxidizable C (ROC), respectively. Further, structural equation modeling and linear regression analysis revealed that SOC recalcitrance (negative effects) and C-degrading enzyme activities (positive effects) together mediate Rs rates; meanwhile, microbial community can indirect affect Rs rates through altering C-degrading enzyme activities. Conclusions Agricultural soil abiotic properties (mainly labile C fractions, i.e., LFC and ROC) are altered by adding organic resources (i.e., manure and straw), the changes of which can promote soil microbial growth, enhance C-degrading microbial activity, and reduce SOC recalcitrance, and in turn accelerate Rs in GVP systems.

24811. 题目: Evaluation of carbon mineralization and structural alterations of organic carbon in high-moor peat soils during incubation
文章编号: N20050709
期刊: Journal of Soils and Sediments
作者: Kazuto Sazawa, Daiki Kubota, Hironori Yoshida, Noriko Hata, Naoya Wada, Hideki Kuramitz
更新时间: 2020-05-07
摘要: Purpose The quantity and quality of soil organic matter (SOM) in the wetlands and peatlands are important for evaluating of the effects of environmental changes. This study’s aim was to evaluate the change in the chemical properties of SOM and dissolved organic matter (DOM) during a constant temperature incubation of high-moor peat soil under two types of vegetation. Materials and methods Incubation of high-moor peat soils collected from marsh vegetation and dwarf bamboo was conducted for 108 days at each temperature of 25 °C and 35 °C. The chemical properties of alkaline extract and DOM in soil samples during incubation were analyzed by tetramethylammonium hydroxide thermochemolysis-gas chromatography-mass spectrometry (TMAH-GC/MS) and fluorescence analysis. Results and discussion The cumulative CO2 emission from peat under dwarf bamboo was higher than that of peat under marsh vegetation. During incubation at 35 °C, plant and microbial residues in DOM extracted from dwarf bamboo soil were increased significantly at the early stages of culture. On the other hand, the components of DOM in the marsh vegetation soil sample did not significantly change between incubation at each temperature. The fluorescence spectra showed that protein-like fluorescent DOM contained in dwarf bamboo soil is consumed by microorganisms, which promotes leaching of humic-like fluorescent DOM and carbon mineralization during the incubation period at a higher temperature. Conclusions Compared with marsh vegetation soil, the DOM in dwarf bamboo soil is susceptible to temperature rises and can be a larger source of CO2 emissions. This study shows that evaluation of DOM properties in soil could be useful to assess the effect of climate change on soil environment.

24812. 题目: Tracking changes in soil organic carbon across the heterogeneous agricultural landscape of the Lower Fraser Valley of British Columbia
文章编号: N20050708
期刊: Science of the Total Environment
作者: S.S. Paul, L. Dowell, N.C. Coops, M.S. Johnson, M. Krzic, D. Geesing, S.M. Smukler
更新时间: 2020-05-07
摘要:

Increasing soil organic carbon (SOC) can improve the capacity of agricultural systems to both adapt to and mitigate climate change. Despite its importance, the current understanding of the magnitude or even the direction of SOC change in agricultural landscapes is limited. While changes in land use/land cover (LULC) and climate are among the main drivers of changes in SOC, their relative importance for the spatiotemporal assessment of SOC is unclear. This study evaluated LULC and SOC dynamics using archived and recent soil samples, remote sensing, and digital soil mapping in the Lower Fraser Valley of British Columbia, Canada. We combined both pixel- and object-based analysis of Landsat satellite imagery to assess LULC changes from 1984 to 2018. We achieved an overall accuracy of 81% and kappa coefficient of 0.77 for LULC classification using a random forest model. For predicting SOC for the same time period, we applied soil and vegetation indices derived from Landsat images, topographic indices, historic soil survey variables, and climate data in a random forest model. The SOC prediction of 2018 resulted in a coefficient of determination (R²) of 0.67, concordance correlation coefficient (CCC) of 0.76, and normalized root mean square error (nRMSE) of 0.12. For 1984, the SOC prediction accuracies were 0.46, 0.58, and 0.18 for R², CCC, and nRMSE, respectively. We detected SOC loss in 61%, gain in 12%, while 27% remained unchanged across the study area. Although we detected large losses of SOC due to LULC change, the majority of the SOC losses across the landscape were attributed to areas that were remained in the same type of agricultural production since 1984. Climate variability did not, however, have a strong effect on SOC changes. These results can inform decision making in the study area to support sustainable LULC management for enhancing SOC sequestration.

24813. 题目: The aggregation and sedimentation of two different sized copper oxide nanoparticles in soil solutions: Dependence on pH and dissolved organic matter
文章编号: N20050707
期刊: Science of the Total Environment
作者: Yanhua Qiu, Zuting Mu, Ning Wang, Xiaojun Wang, Meilan Xu, Helian Li
更新时间: 2020-05-07
摘要:

Copper oxide nanoparticles (CuO NPs) in soil have received considerable attention because of their potential impact on the environment. In the present study, the stability of CuO NPs (50 nm and 80 nm) in eight soil solutions as well as the major influencing factors was investigated. The results showed that hetero-aggregation between natural colloids and NPs dominated the first stage of aggregation, afterwards the two different sized CuO NPs exhibited different aggregation behaviors. The aggregation of 80 nm CuO was inconspicuous except for notable aggregation observed in JX soil solution where the zeta potential of CuO NPs is close to zero. While for 50 nm CuO NPs, the aggregate size sharply decreased and the aggregates gradually reached a stable state. Further, the sedimentation rate and residual concentration of 50 nm CuO were found to be greater than those of 80 nm CuO. The residual amount of 80 nm CuO in the JX soil solution was lower than those in other soil solutions owing to the lowest zeta potential of the NPs. The pH of the soil solution has a significant effect on the stability of CuO NPs because of the shifting of the zeta potential of the NPs. In addition, dissolved organic carbon showed a statistically significant positive correlation with the residual concentration of CuO NPs. These findings imply the properties of CuO NPs as well as environmental factors including pH and DOC play key role in determining the fate, transport, and bioavailability of CuO NPs in soils.

24814. 题目: Effects of pyrolysis temperature on soil-plant-microbe responses to Solidago canadensis L.-derived biochar in coastal saline-alkali soil
文章编号: N20050706
期刊: Science of the Total Environment
作者: Jiawen Tang, Shudong Zhang, Xiaotong Zhang, Jinhuan Chen, Xinyu He, Qiuzhuo Zhang
更新时间: 2020-05-07
摘要:

Because salinity of coastal soils is drastically increasing, the application of biochars to saline-alkali soil amendments has attracted considerable attention. Various Solidago-canadensis-L.-derived biochars prepared through pyrolysis from 400 to 600 °C were applied to coastal saline-alkali soil samples to optimise the biochar pyrolysis temperature and investigate its actual ecological responses. All biochars reduced the soil bulk density and exchangeable sodium stress and increased soil water-holding capacity, cation exchange capacity, and organic matter content. Principal-component-analysis results showed that pyrolysis temperature played an important role in the potential application of biochars to improve the coastal saline-alkali soil, mainly contributed to ameliorating exchangeable sodium stress and decreasing biochar-soluble toxic compounds. Furthermore, soil bulk density and organic matter, as well as carboxylic acids, phenolic acids and amines of biochar were major driving factors for bacterial community composition. Compared to low-temperature biochar (pyrolyzed below 550 °C), which showed higher toxicity for Brassica chinensis L. growth due to the higher content of carboxylic acids, phenols and amines, high-temperature biochar (pyrolyzed at or above 550 °C) possessed less amounts of these toxic functional groups, more beneficial soil bacteria and healthier for plant growth. Therefore, high-temperature biochar could be applied as an effective soil amendment to ameliorate the coastal saline-alkali soil with acceptable environmental risk.

24815. 题目: The remediation of PAH contaminated sediment with mangrove plant and its derived biochars
文章编号: N20050705
期刊: Journal of Environmental Management
作者: Hui Jia, Jian Li, Yi Li, Haoliang Lu, Jingchun Liu, Chongling Yan
更新时间: 2020-05-07
摘要: Highlights • Application of biochar remarkably increased PAH sorption from sediment. • Biochar amendments reduced the PAHs bioavailability in plant tissue after 56 days. • The tested biochars promoted the removal effeciency of PAHs in anaerobic conditions. • Biochar and K. obovata could be a sound remediation treatment when used in combination.

24816. 题目: Application of rapeseed residue increases soil organic matter, microbial biomass, and enzyme activity and mitigates cadmium pollution risk in paddy fields
文章编号: N20050704
期刊: Environmental Pollution
作者: Wentao Yang, Hang Zhou, Jiaofeng Gu, Bohan Liao, Jia Zhang, Pan Wu
更新时间: 2020-05-07
摘要:

Rapeseed (Brassica napus L.) is a winter oil crop and biodiesel resource that has been widely cultivated in the southern part of China. Applying rapeseed residue (RSD) to summer rice fields is a common agricultural practice under rice−rapeseed double cropping systems. However, in Cd−contaminated paddy fields, the influence mechanisms of this agricultural practice on the migration and distribution of Cd fractions in soil are not clear. Therefore, a field experiment was carried out to analyse the changes in soil pH, organic matter (OM), microbial biomass carbon (MBC) and nitrogen (MBN), enzyme activity (urease (UA), acid phosphatase (ACP), and dehydrogenase (DH)), Cd distribution fractions, and Cd concentration in rice tissues after RSD application. The results showed that RSD treatment significantly increased the soil OM and MBC concentrations and UA, ACP, and DH activities, decreased the soil acetic acid−extractable fraction of Cd (ACI–Cd), and increased the reducible fraction of Cd (Red–Cd). The formation of stable organic complexes and chelates upon application of RSD is a result of the high affinity of Cd for soil OM. The activities of soil ACP, DH and MBC can well reflect Cd ecotoxicity in soil, particularly the DH activity. In addition, RSD application was helpful in inducing iron plaque formation. The barrier effect of iron plaque resulted in reduced Cd accumulation in different tissues of rice. The health risk of rice consumption also decreased as a result of RSD application; it decreased by 0.89–30.0% and 24.1–51.7% in the two tested fields. Overall, the application of RSD was increased soil OM, microbial biomass, and enzyme activity, and these changes was instrumental in reduce the risk of cadmium pollution in rice fields.

24817. 题目: Survival, growth and element translocation by 4 plant species growing on acidogenic gold mine tailings in Québec
文章编号: N20050703
期刊: Ecological Engineering
作者: Vanessa Gagnon, Michaël Rodrigue-Morin, Martine Migneault, Antoine Tardif, Louis Garneau, Sophie Lalonde, Bill Shipley, Charles W. Greer, Jean-Philippe Bellenger, Sébastien Roy
更新时间: 2020-05-07
摘要:

Mining activities create nutrient-poor sites that can be impacted by heavy metal solubilization. The introduction of plants into these environments can lead to organic matter deposition that can bind metals and limit their migration in the environment. This study aimed to determine which of four pioneer plant species (Alnus alnobetula ssp. crispa, Alnus incana ssp. rugosa, Larix laricina and Picea glauca) could survive and grow on undisturbed acidogenic gold mine tailings in Northwestern Québec. After three growing seasons, all four outplanted species successfully established on the tailings without the use of organic amendments. Spruce and larch showed lower growth than the two species of alders, which had high survival rates and aerial biomass production per plot. None of the studied species had high metal translocation rates into leaf tissue despite high metal concentrations in the tailings. This study demonstrates the importance of preliminary field trials to optimize plant biomass and biodiversity on reclamation sites and to mitigate the risk of heavy metal translocation into plant tissues. Our results suggest that the reclamation of acidogenic tailings, without the use of capping materials, warrants further study.

24818. 题目: Can soil properties and land use explain glomalin-related soil protein (GRSP) accumulation? A nationwide survey in France
文章编号: N20050702
期刊: Catena
作者: Siobhan Staunton, Nicolas P.A. Saby, Dominique Arrouays, Hervé Quiquampoix
更新时间: 2020-05-07
摘要:

Organic matter plays essential roles in soil, including physical stabilization, nutrient storage and carbon sequestration. An operationally defined fraction of soil organic matter known as glomalin or glomalin-related soil protein, GRSP, is obtained by autoclaving soil in citrate solution. It is reputed to be of fungal origin, very stable and responsible for enhanced soil physical stability. This is the first nationwide survey of GRSP content in soil and was conducted to test the hypotheses on the origin and identity of GRSP. Nearly 200 archived soils were selected on the basis of organic matter content from the French National Soil Inventory, representing mostly cropland, grassland and woodland land uses. Two fractions of GRSP were measured, easily extractable (GRSP_EE) and total (GRSP_T), extraction. The median values of GRSP_EE and GRSP_T were 0.7 and 2 g kg⁻¹ respectively, with a strong correlation between the two fractions. Scatter plots and cubist modelling were used to explore the relationships between the contents of the two GRSP fractions and both soil properties and land use. Land use effects were almost entirely attributable to soil characteristics. No evidence was found to support the hypotheses that GRSP is solely of fungal origin, nor that easily extracted GRSP is more recent that the total fraction, although this does not disprove either hypothesis. Soil organic matter was enriched in GRSP C-depleted cropland soils and lower in C-rich woodland, this may result from inherent stability or differences in plant-related composition of carbon input.

24819. 题目: Role of Extracellular Polymeric Substances in Microbial Reduction of Arsenate to Arsenite by Escherichia coli and Bacillus subtilis
文章编号: N20050701
期刊: Environmental Science & Technology
作者: Xinwei Zhou, Fuxing Kang, Xiaolei Qu, Heyun Fu, Pedro J. J. Alvarez, Shu Tao, Dongqiang Zhu
更新时间: 2020-05-07
摘要: We show that arsenate can be readily reduced to arsenite on cell surfaces of common bacteria (E. coli or B. subtilis) or in aqueous dissolved extracellular polymeric substances (EPS) extracted from different microorganisms (E. coli, B. subtilis, P. chrysosporium, D. gigas, and a natural biofilm) in the absence of exogenous electron donors. The efficiency of arsenate reduction by E. coli after a 7-h incubation was only moderately reduced from 51.3% to 32.7% after knocking out the arsenic resistance genes (arsB and arsC). Most (>97%) of the reduced arsenite was present outside the bacterial cells, including for the E. coli blocked mutant lacking arsB and arsC. Thus, extracellular processes dominated arsenate reduction. Arsenate reduction was facilitated by removing EPS attached to E. coli or B. subtilis, which was attributed to enhanced access to reduced extracellular cytochromes. This highlights the role of EPS as a permeability barrier to arsenate reduction. Fourier-transform infrared (FTIR) combined with other chemical analyses implicated some low-molecular weight (<3 kDa) molecules as electron donors (reducing saccharides) and electron transfer mediators (quinones) in arsenate reduction by dissolved EPS alone. These results indicate that EPS act as both reducing agent and permeability barrier for access to reduced biomolecules in bacterial reduction of arsenate.

24820. 题目: Organic management improves soil phosphorus availability and microbial properties in a tea plantation after land conversion from longan (Dimocarpus longan)
文章编号: N20050611
期刊: Applied Soil Ecology
作者: Tingting Wu, Wenjie Liu, Dungang Wang, Yukun Zou, Rui Lin, Qiu Yang, Thomas Gbokie, Mansoor Ahmed Bughio, Qinfen Li, Jinchuang Wang
更新时间: 2020-05-06
摘要:

Studies on the transformation of P fractions under different land uses and management practices remain scarce, especially in tropical regions. Hence, we investigated the P fraction, microbial communities and soil chemical properties after the conversion of a longan orchard (LO) into an organic tea plantation (OTP) and a conventional tea plantation (CTP) in Hainan, China. At 0–10 cm and 10–20 cm soil depths, the conversion of the LO into the OTP increased the contents of labile P (Resin-P, NaHCO₃-P_i and NaHCO₃-P_o), moderately labile P (NaOH-P_i and NaOH-P_o) and occluded P (Sonicate-P_i and Sonicate-P_o) but decreased the contents of Ca-P (HCl-P_i) and residual P (stable P), whereas converting the LO into the CTP increased the Ca-P and residual P but decreased the labile P, moderately labile P and occluded P. In addition, at the 0–10 cm soil depth, the bacteria, fungi, actinomycetes, arbuscular mycorrhizal fungal (AMF) and total phospholipid fatty acid (PLFA) biomass were decreased in the CTP, but only the total PLFA was increased in the OTP. However, at the 10–20 cm soil depth, the total PLFA, fungi, and AMF were increased in the OTP, whereas all the PLFA biomarkers remained unchanged in the CTP compared to those in the LO. Furthermore, the labile P, moderately labile P, occluded P and Ca-P in the 0–10 cm layer were related to the soil chemical properties and microbially related groups such as the TK, NO₃⁻, NH₄⁺, acid phosphatase activity (APA), fungi, AMF and bacteria. However, at the 10–20 cm soil depth, these fractions were only associated with soil chemical properties such as the TK, NO₃⁻, NH₄⁺ and APA. Our results revealed that the land use altered the soil P fractions as well as the microbial biomass and activity related to soil P cycling, and organic management practices enhanced the soil P availability more than conventional management practices.