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181. 题目: Nutrient ratios in marine particulate organic matter are predicted by the population structure of well-adapted phytoplankton
文章编号: N20071701
期刊: Science advances
作者: Shlomit Sharoni, Itay Halevy
更新时间: 2020-07-17
摘要: A common assumption of a constant nitrogen-to-phosphorus ratio (N:P) of 16:1 in marine particulate organic matter (POM) appears to be invalidated by observations of major spatial variations in N:P. Two main explanations have been proposed. The first attributes the N:P variability to changes in the community composition of well-adapted phytoplankton. The second proposes that variability arises from physiological acclimation involving intracellular adjustments of nutrient allocation under nutrient deficiency. Using a model of phytoplankton physiology, observational datasets, and a review of laboratory culture results, we assess the mechanistic basis of N:P variability. We find that the taxonomic composition of well-adapted phytoplankton best explains observed variations in POM N:P. Furthermore, we show that acclimation to nutrient deficiency may be safely neglected when considering the effects of ecology on POM N:P. These findings provide insight into the controls on global variability in POM composition and average phytoplankton physiological performance in the oceans.

182. 题目: Conversion of biochar to sulfonated solid acid catalysts for spiramycin hydrolysis: Insights into the sulfonation process
文章编号: N20071610
期刊: Environmental Research
作者: Qianqian Xie, Xiao Yang, Kangning Xu, Zheng Chen, Binoy Sarkar, Xiaomin Dou
更新时间: 2020-07-16
摘要:

Biochar has been recognized as a sustainable platform for developing functional materials including catalysts. This work demonstrated a method of converting biochar to sulfonated solid-acid catalysts, and the effectiveness of the catalysts for spiramycin hydrolysis was examined. Two biochar samples (H and X) were sulfonated with three reagents (concentrated H2SO4, ClSO3H and p-toluenesulfonic acid (TsOH)) under hydrothermal, simple heating, ambient temperature, and CHCl3-assisted treatments. The effect of elemental compositions and structural characteristics of the feeding materials (H and X) on the acidic properties of the sulfonated biochars were investigated. The results showed that the sulfonation ability of the three reagents was in the order of ClSO3H > H2SO4 > TsOH, while hydrothermal treatment provided the highest total acidity, and largest amount of acidic groups (e.g., SO3H, COOH and Ar-OH). Biochar X with higher O/C and N contents, and less graphitic features showed superior acidic properties than biochar H under all the employed treatments. The hydrolytic efficiencies of the sulfonated biochars under 200 W of microwave irradiation increased with increasing total acidity, and the amount of SO3H and COOH groups. After sulfonation, the O/C of biochars increased, while H/C decreased, and the aromatic and graphitic features did not change. The electromagnetic energy absorbed by the sulfonated biochars did not notably contribute to spiramycin hydrolysis. Thus, this work demonstrated an effective and promising method for maneuvering biochar-based functional solid-acid catalysts for antibiotic remediation in contaminated water.

183. 题目: Carbon nanoarchitectures as high-performance electrodes for the electrochemical oxidation of landfill leachate
文章编号: N20071609
期刊: Journal of Hazardous Materials
作者: Mattia Pierpaoli, Paweł Jakobczyk, Mirosław Sawczak, Aneta Łuczkiewicz, Sylwia Fudala-Książek, Robert Bogdanowicz
更新时间: 2020-07-16
摘要:

Nanomaterials and assemblies of the aforementioned into complex architectures constitute an opportunity to design efficient and selective solutions to widespread and emerging environmental issues. The limited disposal of organic matter in modern landfills generates extremely concentrated leachates characterised by high concentrations of refractory compounds. Conventional biochemical treatment methods are unsuitable, while advanced treatment, such coagulation, reverse osmosis and ultrafiltration can be very costly and generate additional waste. Electrochemical oxidation is an established technique to efficiently mineralise a plethora of recalcitrant pollutants, however the selectivity and efficiency of the process are strongly related to the anode material. For this reason, a nanoarchitectured carbon material has been designed and synthesised to improve the capability of the anode towards the adsorption and decomposition of pollutants. Instead of simple nanostructures, intelligently engineered nanomaterials can come in handy for more efficient advanced treatment techniques. In this study, a carbon nanoarchitecture comprising boron-doped vertically aligned graphene walls (BCNWs) were grown on a boron-doped diamond (BDD) interfacial layer. The results show how the peculiar maze-like morphology and the concurrence of different carbon hybridisations resulted in a higher current exchange density. The BDD performed better for the removal of NH4+ while the BCNW-only sample exhibited a faster deactivation. The BDD/BCNW nanoarchitecture resulted in an enhanced COD removal and a NH4+ removal similar to that of BDD, without the intermediate production of NO2 and NO3.

184. 题目: Changes in soil organic carbon and microbial community under varying straw incorporation strategies
文章编号: N20071608
期刊: Soil and Tillage Research
作者: Ping Cong, Jing Wang, Yuyi Li, Na Liu, Jianxin Dong, Huancheng Pang, Li Zhang, Zhijuan Gao
更新时间: 2020-07-16
摘要:

Straw return is a popular management strategy to improve soil organic carbon (SOC) and change soil microbial community structure in agro-ecosystems. In the North China plain, the average straw incorporation rate is 6000–10,000 kg ha−1, however, effective utilization of maize straw is difficult because of its large amount and volume. A four-year (2014–2017) experiment was conducted to investigate the effects of different forms of maize straw on subsoil SOC fractions and microbial communities under deep-buried (30–40 cm) management in a typic Agrosol in Liaohe plain. Six treatments were established: no straw (CK, 0 kg ha−1), whole straw (WS, 6000 kg ha−1), chopped straw (CS, 6000 kg ha−1), pelletized straw (PS, 6000 kg ha−1), straw biochar (BC, 2010 kg ha−1) and straw ash (SA, 960 kg ha−1). Soil organic carbon, dissolved organic carbon (DOC), microbial biomass carbon (MBC), and bacterial and fungal diversity and abundance were analysed by chemical and molecular methods. Compared with CK, the five treatments significantly increased the SOC pool by 1.4–4.8 % in the 0–20 cm soil depth and 3.2–14.2 % in the 20–40 cm depth, with the highest increase under CS. Both CS and WS significantly increased the DOC and MBC, with higher DOC/SOC and MBC/SOC ratios. Notably, straw incorporation showed greater effects on DOC and MBC and a higher increase in SOC fractions in the 20–40 cm depth. Principal component analysis and similarity analysis showed that the different forms of straw incorporation caused significant variations in microbial community structure in the subsoil layer. The BC and SA significantly increased the diversity of soil microorganisms, while CS and WS altered the relative abundance of the dominant bacterial phyla Acidobacteria, Nitrospirae, Proteobacteria, Verrucomicrobia and dominant fungal phyla Ascomycota, Morttierellomycota, Glomeromycota, which increased with increases in SOC fractions. Our results showed that regulation of C-related microbial abundance in the subsoil was more conducive to improving SOC fractions than simply improving soil microbial diversity. Since chopped straw significantly increased the abundance of C-related microflora and SOC fractions, it should be the optimal form of incorporation in deep-buried straw management.

185. 题目: Humic acid’s (HA) role on NDMA formation from daminozide (DMNZD) during ozonation
文章编号: N20071607
期刊: Environmental Science: Water Research & Technology
作者: Huan Qi, Qing Lin, Mengyi Chen, Xiaobin Liao, Jie Chen, Fei Li, Baoling Yuan
更新时间: 2020-07-16
摘要: Daminozide (DMNZD) has been found to be an important ozone-reactive N-Nitrosodimethylamine (NDMA) precursor, however, the influence of humic acid (HA) on NDMA formation from daminozide during ozonation is unclear. In this study, the impacts of HA on NDMA formation from daminozide at various oxidation conditions (ozone dosages, pH) and other water components (bicarbonate ion (HCO3-), sulfate ion (SO42-)) were investigated. In addition, its implications for water treatment plants were discussed. The results indicated that low levels of HA (≤0.6 mg/L) facilitated NDMA formation and its molar yield maximized at 0.1 mg/L HA (8.5 %), while high concentration of HA (>0.6 mg/L) had inhibition roles. NDMA amounts raised with increasing pH and showed a peak at pH 8. With 0.1 mg/L HA, NDMA raised from 3.0 to 23.1 % with ozone increasing from 0.5 to 4 mg/L; HCO3- competed with daminozide for ozone and cut down NDMA formation, 160 μM HCO3- reduced NDMA conversion from 8.5 to 6.5 %; with the increase of SO42- from 0 to 20 μM, NDMA conversion augmented from 8.5 to 17.8 %. Based on the results of LC/MS/MS and GC/MS, NDMA transformation pathways with/without HA were proposed.

186. 题目: Impact of biochar addition on soil thermal properties: Modelling approach
文章编号: N20071606
期刊: Geoderma
作者: Bogusław Usowicz, Jerzy Lipiec, Mateusz Łukowski, Zbigniew Bis, Jerzy Usowicz, Agnieszka E. Latawiec
更新时间: 2020-07-16
摘要:

Little information is available on the effect of biochar on both measured and model-predicted soil thermal properties although they play a crucial role in the accumulation and transfer of heat and water through the soil. This study aimed at evaluation of the impact of biochar addition on soil thermal properties in field experiments conducted in China and Poland. The experimental data included biochar doses, soil texture, quartz and other minerals, bulk density, particle density, water content, air-filled porosity, and organic matter content. The data were then used to validate three models (analytic of de Vries, analytic of Zhao et al., and statistical-physical) and improve the predictability of the soil thermal properties. The biochar doses in the field experiments were from 4.5 to 40 Mg ha−1 and those in the modelling study ranged from 52 to 267 Mg ha−1. Pure biochar was used as well. The biochar additions caused a significant decrease in thermal conductivity and thermal diffusivity and exerted a less pronounced effect on the heat capacity. As shown by classic statistics and Bland-Altman plots, the agreement between the predicted and measured heat capacity of the Chinese soil was good and similar to the Zhao et al. and de Vries models. The best agreement between the statistical-physical model predicted and measured the thermal conductivity and diffusivity was obtained using the geometric mean of the native soil organic matter and biochar and after reduction of the quartz content in the sand fraction (2–0.05 mm) from 100 to 72%. The thermal diffusivity decreased with increasing biochar dose at comparable water contents and its characteristic maximum shifted towards higher water contents with increasing biochar dose. As thermal diffusivity enhances the smoothing of the temperature wave, these results imply that application of different biochar rates may help in regulation of soil temperature, which is an essential determinant of plant growth and soil processes and functions.

187. 题目: Effects of biochar on methane emission from paddy soil: Focusing on DOM and microbial communities
文章编号: N20071605
期刊: Science of the Total Environment
作者: Mengyuan Ji, Lei Zhou, Shicheng Zhang, Gang Luo, Wenjing Sang
更新时间: 2020-07-16
摘要:

Biochar can be used as a soil amendment. However, it generally possesses unique physicochemical properties and complex organics, which could affect soil methanogenesis. In this study,straw-based biochars obtained at 300 °C (BC300), 500 °C (BC500) and 700 °C (BC700) were added to the paddy soil. Compared with the blank group, BC300 significantly increased paddy soil methane emissions by about 38%. However, this promoting effect gradually disappeared with the increase of pyrolysis temperature, and the inhibition even appeared in the BC700 group with the methane reduction by 18.2%. This might be related to the organics released from biochar. Van Krevelen (VK) diagram showed that the aromaticity of BC700 and BC500 were significantly higher than BC300. Fluorescent analysis further revealed that BC300 increased the amount of degradable fluorescent organics in the soil, which could provide more substrate for methane production. Moreover, as pyrolysis temperature increased, the fluorescent organics released were more likely to be non-biodegradable humus. In addition, it was shown that BC700 could adsorb some inherent organics in the soil, and thus reduced the total organic content and inhibited soil methane emissions. Microbial analysis showed that methanogenesis had a positive correlation with the abundance of syntrophic bacteria (e.g. Desulfobacca and Clostridium) which had ability to further degrade various types of organics and provided substrates to the methanogens. This article provides a deeper understanding regarding for the effects of biochar on methane emission from paddy soil in terms of organics and microbial perspectives.

188. 题目: Application of Aurantiochytrium sp. L3W for food-processing wastewater treatment in combination with polyunsaturated fatty acids production for fish aquaculture
文章编号: N20071604
期刊: Science of the Total Environment
作者: Nurlaili Humaidah, Satoshi Nakai, Wataru Nishijima, Takehiko Gotoh, Megumi Furuta
更新时间: 2020-07-16
摘要:

Thraustochytrids such as Aurantiochytrium are heterotrophic microorganisms that are known to produce valuable polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In this study, Aurantiochytrium sp. strain L3W was used to remove dissolved organic carbon (DOC) and dissolved nitrogen (DN) from bean-boiling (BB) and miso-processing (MP) wastewater and to simultaneously produce PUFAs. Strain L3W removed 52% of the DOC and 37% of the DN from sterilized BB wastewater and produced biomass that contained 137 mg/g of fatty acids (FAs), including 96.2 mg/g of DHA. Growth of strain L3W in sterilized MP wastewater resulted in the production of biomass containing 147.6 mg/g of FAs, including 97.8 mg/g of DHA, and removal of 47% of the DOC and 55% of the DN from the wastewater. The biomass of strain L3W was digestible by the enzymes extracted from the stomachs of rainbow trout. These results confirmed the potential for use of strain L3W to remove DOC and DN from food processing wastewater and to produce PUFAs. This study also provided the first evidence that the raw biomass of Aurantiochytrium sp. can be used as a fish feed additive.

189. 题目: Nickel aluminum layered double oxides modified magnetic biochar from waste corncob for efficient removal of acridine orange
文章编号: N20071603
期刊: Bioresource Technology
作者: Huan Wang, Wei Zhao, Youning Chen, Yuhong Li
更新时间: 2020-07-16
摘要:

The objective of this work was to use corncob as raw material to prepare green reusable magnetic biochar for removal of dyes in wastewater. For this purpose, an environmentally friendly NiAl layered double oxides modified magnetic corncob biochar (MC1/NiAl-LDO) was obtained by pyrolysis of NiAl layered double hydroxides modified magnetic corncob biochar (MC1/NiAl-LDH) at 700 °C for 3 hours. The surface area of MC1/NiAl-LDO is552.62 m2∙g-1, which was much higher than that of MC1 (26.83 m2∙g-1). MC1/NiAl-LDO for acridine orange (AO) exhibited higher adsorption ability, the adsorption capacity of MC1/NiAl-LDO was increased by 90% compared with MC1. Adsorption experiments for AO on MC1/NiAl-LDO were carried with effect of pH, adsorption time, initial concentrations of AO and ionic strength. MC1/NiAl-LDO can be recycled nine times. The results exhibited that MC1/NiAl-LDO was a low cost adsorbent, providing good example for th agricultural waste recycling.

190. 题目: Tree planting in organic soils does not result in net carbon sequestration on decadal timescales
文章编号: N20071602
期刊: Global Change Biology
作者: Nina L. Friggens, Alison J. Hester, Ruth J. Mitchell, Thomas C. Parker, Jens‐Arne Subke, Philip A. Wookey
更新时间: 2020-07-16
摘要:

Tree planting is increasingly being proposed as a strategy to combat climate change through carbon (C) sequestration in tree biomass. However, total ecosystem C storage that includes soil organic C (SOC) must be considered to determine whether planting trees for climate change mitigation results in increased C storage. We show that planting two native tree species (Betula pubescens and Pinus sylvestris ), of widespread Eurasian distribution, onto heather (Calluna vulgaris ) moorland with podzolic and peaty podzolic soils in Scotland, did not lead to an increase in net ecosystem C stock 12 or 39 years after planting. Plots with trees had greater soil respiration and lower SOC in organic soil horizons than heather control plots. The decline in SOC cancelled out the increment in C stocks in tree biomass on decadal timescales. At all four experimental sites sampled, there was no net gain in ecosystem C stocks 12–39 years after afforestation—indeed we found a net ecosystem C loss in one of four sites with deciduous B. pubescens stands; no net gain in ecosystem C at three sites planted with B. pubescens ; and no net gain at additional stands of P. sylvestris . We hypothesize that altered mycorrhizal communities and autotrophic C inputs have led to positive 'priming' of soil organic matter, resulting in SOC loss, constraining the benefits of tree planting for ecosystem C sequestration. The results are of direct relevance to current policies, which promote tree planting on the assumption that this will increase net ecosystem C storage and contribute to climate change mitigation. Ecosystem‐level biogeochemistry and C fluxes must be better quantified and understood before we can be assured that large‐scale tree planting in regions with considerable pre‐existing SOC stocks will have the intended policy and climate change mitigation outcomes.

191. 题目: Soil organic matter turnover depending on land use change: Coupling C/N ratios, δ13C and lignin biomarkers
文章编号: N20071601
期刊: Land Degradation and Development
作者: Shaopan Xia, Zhaoliang Song, Yidong Wang, Weiqi Wang, Pal Singh Bhupinder, Yakov Kuzyakov, Hailong Wang
更新时间: 2020-07-16
摘要: Soil organic carbon (SOC) stocks have been greatly depleted by the global extent of conversion from wetlands to cropland, agroforestry and urban areas. Here, we investigated SOC distribution and turnover in four land use types: wetland, cropland, forestland, and construction land in the Baiyangdian wetland, northern China. The C:N ratios were up to 1.70 times larger in cropland, forestland and construction land than in the original wetland because of faster N losses compared to C by wetland conversion. The δ13C values of SOC increased with depth in wetland, and were overall depleted than the other three land use types. Acid‐to‐aldehyde ratios of syringyl in wetland were 0.72–1.14, 0.72–1.72, 1.18–1.43 times, and cinnamyl/vanillyl ratios were 0.56–1.05, 0.22–0.48, 0.40–0.76 times those of cropland, forestland and construction land, which reflect faster lignin decomposition rate in wetlands. The β value was defined by the slope of the linear regression between the logarithm of SOC and δ13SOC values, and decreased from cropland over construction land and forestland to wetland, reflecting the faster SOC turnover with the lower β values. However, SOC content and storage were up to 2.29 and 2.07 times higher in wetlands than in soils of other land use types. The combination of C:N ratios, δ13C, and lignin monomer composition can explain well the decrease of β value (corresponding to faster SOC turnover), and can be used as effective proxies to evaluate the sources and turnover of SOC in response to land use changes.

192. 题目: Delineating the continuum of dissolved organic matter in temperate river networks
文章编号: N20071509
期刊: Global Biogeochemical Cycles
作者: Joan P. Casas‐Ruiz, Robert G. M. Spencer, François Guillemette, Daniel Schiller, Biel Obrador, David C. Podgorski, Anne M. Kellerman, Jens Hartmann, Lluís Gómez‐Gener, Sergi Sabater, Rafael Marcé
更新时间: 2020-07-15
摘要: The origin and reactivity of dissolved organic matter (DOM) has received attention for decades due to the key role DOM plays in global carbon cycling and the ecology of aquatic systems. However, DOM dynamics in river networks remain unresolved, hampered by the lack of data integrating the spatial and temporal dimensions inherent to riverine ecosystems. Here we examine the longitudinal patterns of dissolved organic carbon (DOC) concentration and DOM chemical diversity along a temperate river network under different hydrological conditions, encompassing small headwater streams to the river mouth, and base flow to storm events. We show that, during non‐storm conditions, the concentration of DOC and the chemical diversity of DOM exhibit their maxima in the middle section of the network, depicting a bell‐shaped pattern along the river continuum. In contrast, DOM shows a homogeneous longitudinal pattern during storm events, with highly concentrated and diverse DOM along the river network. We posit that these emerging patterns result from changes in the relative influence of catchment versus in‐stream biogeochemical processes along the river continuum, and that the degree of influence is modulated by river network hydrology. Based on these findings we put forward the Bending DOM Concept, a new conceptual framework around which testable hypotheses on the spatiotemporal dynamics of DOM and the functioning of temperate river networks may be formulated.

193. 题目: Successive biochar amendment improves soil productivity and aggregate microstructure of a red soil in a five-year wheat-millet rotation pot trial
文章编号: N20071508
期刊: Geoderma
作者: Lili He, Jin Zhao, Shengmao Yang, Hu Zhou, Shenqiang Wang, Xu Zhao, Guangxi Xing
更新时间: 2020-07-15
摘要:

Soil structure affects soil physical, chemical, and microbial processes, and is a key factor influencing soil productivity and ecological functions. Biochar (BC) has a porous structure, large surface area and high organic carbon content and therefore has the potential to regulate soil structure and productivity. In the present study, we evaluated the effects of five-year successive seasonal application of BC at three different rates (0, 2.25 and 22.5 Mg ha−1) along with chemical fertilizer on soil microstructure and soil fertility of a red soil using a pot trial under wheat-millet crop rotations. We found continuous application of chemical fertilizers reduced soil fertility with progressive reductions in wheat and millet biomass yields over five rotation cycles. While BC amendment slowed the decline of soil productivity with their yield of grain and straw significantly higher than the treatment without BC. Application of high rate of BC (BC22.5) significantly improved soil fertility, with increased soil pH (3.29 units), cation exchangeable capacity (5.66 cmol kg−1), plant available water capacity (50.0%), soil organic carbon (306%), total nitrogen (182%), available phosphorus (241%), potassium (513%), calcium (245%) and magnesium (265%), and significantly decreased bulk density (0.52 g cm−3), soil exchange acidity (6.37 cmol kg−1) and exchange Al3+ concentrations (5.87 cmol kg−1) after five rotations. Specially, BC improved aggregate stability, intra-aggregate pore structure and water retention capacity, manifesting that BC might be an effective soil amendment to reduce soil erosion in this region. Our results indicated that long-term successive seasonal BC application could improve soil fertility and soil aggregation, and thus eliminate soil acidification and restore soil productivity in the acidic red soil.

194. 题目: Rapid recovery of carbon cycle processes after the cessation of chronic nutrient enrichment
文章编号: N20071507
期刊: Science of the Total Environment
作者: Thomas J. Mozdzer, Sophie E. Drew, Joshua S. Caplan, Paige Weber, Linda A. Deegan
更新时间: 2020-07-15
摘要:

Salt marshes provide critical ecosystem services including some of the highest rates of carbon storage on Earth. However, many salt marshes receive very high nutrient loads and there is a growing body of evidence indicating that this nutrient enrichment alters carbon cycle processes. While many restoration plans prioritize nutrient management in their efforts to conserve salt marsh ecosystems, there has been little empirical investigation of the capacity for carbon cycle processes to recover once nutrient loading is reduced. To address this, we compared rates of greenhouse gas fluxes (i.e., CO2 and methane) measured using static chambers, and soil organic matter decomposition, using both decomposition bags and the Tea Bag index, during the last two years of a long-term, ecosystem-scale nutrient enrichment experiment (2015–2016), as well as in the first two years post-enrichment (2017–2018). We found that both ecosystem respiration (Reco) and decomposition processes (i.e., rhizome decomposition and soil organic matter stabilization) were enhanced by nutrient enrichment, but returned to reference ecosystem levels within the first year following the cessation of nutrient enrichment, and were maintained in the second year. These results suggest that management practices intended to reduce nutrient loads in coastal systems may, in fact, allow for rapid recovery of carbon cycle processes, potentially restoring the high rates of carbon sequestration to these blue carbon ecosystems.

195. 题目: Overseeding legumes in natural grasslands: Impacts on root biomass and soil organic matter of commercial farms
文章编号: N20071506
期刊: Science of the Total Environment
作者: Viviana Bondaruk, Felipe Lezama, Amabelia del Pino, Gervasio Piñeiro
更新时间: 2020-07-15
摘要:

Overseeding legumes in natural grasslands coupled with phosphorous fertilization are management practices oriented to increase forage production and quality, and to restore nutrient losses generated by livestock. Several studies show increases in forage due to this practice, but less is known about impacts on soil fertility and carbon sequestration. The objective of this study was to evaluate under real farm conditions changes in root C and N stocks and soil organic carbon (SOC) and nitrogen (SON) stocks in two different soil pools, the particulate organic matter (POM) and the mineral associated organic matter (MAOM), after the introduction in natural grasslands of a legume species, Lotus subbiflorus cv. El Rincón, accompanied with phosphorous fertilization. We also evaluated changes in the natural abundance of 15N and 13C in soils and roots to understand changes in N fixation and species composition. We selected 12 adjacent paddocks of natural grasslands (NG) and natural grasslands overseeded with legumes and fertilized with phosphorous (NGLP) located in commercial farms in Uruguay. We found that overseeding legumes increased root C and N stocks and SOC and SON stocks in some farms but decreased them in others. On average, no significant differences arose between NGLP and NG paddocks in total stocks of 0–30 cm depth. However, higher C stocks were observed in POM of NGLP paddocks in 0–5 cm layer and lower contents in 5–10 cm layer indicating a change in the vertical distribution of C in POM. Changes in δ15N suggest that atmospheric N is being fixed by legumes in NGLP paddocks, but not translated into more N or C stocks in the MAOM fraction, probably due to high N losses promoted by cattle grazing. Our work suggests that carbon sequestration can be achieved after legumes introduction in grazed natural grasslands but will depend on grazing management practices.

196. 题目: Agrochemical leaching reduction in biochar‐amended tropical soils of Belize
文章编号: N20071505
期刊: European Journal of Soil Science
作者: Gerardo O. Aldana, Charles Hazlerigg, Elisa Lopez-Capel, David Werner
更新时间: 2020-07-15
摘要:

The aim of this study was to determine the effects of biochar addition on agrochemical leaching in tropical soils of Belize. Biochars were produced from mixed softwood, rice husk and miscanthus straw, each pyrolysed at 700°C. Loam, sandy silt loam, and clay loam tropical soils were amended with 0, 1, 2.5 and 5% (w/w) biochar to determine atrazine, diuron, enrofloxacine, oxytetracycline and tetracycline absorption in batch studies following OECD 106 guidelines. FOCUS groundwater modelling was performed with the results of the batch‐sorption study and alterations to the soil profiles to explore the effect of biochar amendment on the leaching of atrazine in a risk assessment context. Results showed that agrochemical sorption was higher in biochar amended soils than soils without biochar amendment. Soil organic matter content and biochar amendment contributed to the agrochemical sorption increase in soils. The FOCUS modelling showed a significant reduction in Predicted Environmental Concentration in groundwater (PECgw) of atrazine when biochar was amended to the soil. However, a trade‐off was identified between the sorptive capacity of the biochar and the changes in hydrology in the soil as a result of the biochar incorporation. The amendment of Belizean tropical soils with rice husk biochar was shown to be an effective method to reduce the leaching of the selected agrochemicals, though the widespread implementation should be conducted carefully, taking account of the potential trade‐offs with biochar use identified in our modelling.

197. 题目: Molecular dynamics of foliar litter and dissolved organic matter during the decomposition process
文章编号: N20071504
期刊: Biogeochemistry
作者: Alex T. Chow
更新时间: 2020-07-15
摘要: Decomposing foliar litter organic matter (LOM) in forested watersheds is an essential terrestrial source of dissolved organic matter (DOM) to aquatic ecosystems. To evaluate the relationship of chemical composition between LOM and DOM, we collected freshly fallen leaves of white oak (Quercus alba) and conducted an 80-week field decomposition experiment along a small elevation gradient in a floodplain within the Congaree National Park, South Carolina. Foliar litters were collected for water extraction and instrumental analyses using pyrolysis GC/MS, UV/VIS and fluorescence spectrophotometry. Factor analyses of pyrolysates showed that fresh LOM was mainly composed of lignin compounds (LgC), phenolic compounds (PhC), and carbohydrate (Carb), and the change in composition was relatively small throughout the decomposition process. In contrast, there were two distinct chemical compositions of DOM in early (between 0–8 weeks) and late phases (between 16–80 weeks). The early phase had a higher percentage of PhC, but the late phase contained higher percentages of Carb, unsaturated hydrocarbon (UnSaH), aromatic hydrocarbon (ArH), and nitrogen-containing compounds (Ntg). The fluorescence emission-excitation matrix showed there was an increasing trend in humic and fulvic-like fractions in DOM over time, matching well with increases of UnSaH and ArH fractions from the results of pyrolysis GC/MS. Our study illustrated that the changes of chemical components in LOM and water extractable DOM were not parallel during the decomposition process and the degradation of lignin and phenolic compounds was one of the controlling factors on the production of DOM.

198. 题目: Effects of Storm Events on Phosphorus Concentrations in a Forested New England Stream
文章编号: N20071503
期刊: Water, Air, and Soil Pollution
作者: Anju Shrestha
更新时间: 2020-07-15
摘要: Phosphorus is considered the primary limiting nutrient in the freshwater aquatic ecosystems; thus, excessive concentrations of phosphorus (P) in streams and lakes can lead to eutrophication. Understanding the transport of P from minimally impacted watersheds provides a benchmark for quantifying human enhancement of P loss from the landscape. To better understand storm event transport of P from small watersheds of northern New England, we examined hourly variations in P in its multiple forms during three rain events at Livermore Cove Brook, New Hampshire, USA. The three storm events had different hydrological characteristics that resulted in different maximum total P concentrations. Streamwater P levels rose quickly at the onset of each event, remained high for a few hours during peak flow, and subsided as flow decreased. Dissolved organic P was the dominant species of P in the streamwater during baseflow and event flow. For each event, P concentrations were higher on the rising limbs of the hydrograph, resulting in clockwise hysteresis of the concentration-discharge relationships. Different behavior of the more inorganic, soluble reactive P hysteresis curve suggests a different source than the other P species. Both particulate and dissolved organic P were highest an hour before peak discharge and storm event water, suggesting quick mobilization of sources proximal to the stream. Soluble reactive P peaked an hour after discharge and storm event water, suggesting slower mobilization or more distal sources. Overall, these results show that storms create episodic peak concentrations of P that constitute a substantial flux of P to downstream lakes and wetlands. Consequently, efforts to manage P in New England lakes likely require greater attention to P transport during episodic storm events and their contribution to annual P loading.

199. 题目: Reactivity of Pyrogenic Carbonaceous Matter (PCM) in mediating environmental reactions: Current knowledge and future trends
文章编号: N20071502
期刊: Frontiers of Environmental Science & Engineering
作者: Wenqing Xu, Mark L. Segall, Zhao Li
更新时间: 2020-07-15
摘要: Pyrogenic Carbonaceous Matter (PCM; e.g., black carbon, biochar, and activated carbon) are solid residues from incomplete combustion of fossil fuel or biomass. They are traditionally viewed as inert adsorbents for sequestering contaminants from the aqueous phase or providing surfaces for microbes to grow. In this account, we reviewed the recently discovered reactivity of PCM in promoting both chemical and microbial synergies that are important in pollutant transformation, biogeochemical processes of redox-active elements, and climate change mitigation with respect to the interaction between biochar and nitrous oxide (N2O). Moreover, we focused on our group's work in the PCM-enhanced abiotic transformation of nitrogenous and halogenated pollutants and conducted in-depth analysis of the reaction pathways. To understand what properties of PCM confer its reactivity, our group pioneered the use of PCM-like polymers, namely conjugated microporous polymers (CMPs), to mimic the performance of PCM. This approach allows for the controlled incorporation of specific surface properties (e.g., quinones) into the polymer network during the polymer synthesis. As a result, the relationship between specific characteristics of PCM and its reactivity in facilitating the decay of a model pollutant was systematically studied in our group's work. The findings summarized in this account help us to better understand an overlooked environmental process where PCM synergistically interacts with various environmental reagents such as hydrogen sulfide and water. Moreover, the knowledge gained in these studies could inform the design of a new generation of reactive carbonaceous materials with tailored properties that are highly efficient in contaminant removal.

200. 题目: Incorporation of biochar into semi-interpenetrating polymer networks through graft co-polymerization for the synthesis of new slow-release fertilizers
文章编号: N20071501
期刊: Journal of Cleaner Production
作者: Xiongfang An, Jianglong Yu, Junzhi Yu, Arash Tahmasebi, Zhansheng Wu, Xiaochen Liu, Bing Yu
更新时间: 2020-07-15
摘要:

Modern agriculture is strongly calling for the development of environment-friendly slow-release fertilizers (SRFs) with high water retention. In this study, a new biochar embedded-Semi-IPN based SRF is developed by the incorporation of biochar into semi-interpenetrating polymer networks (Semi-IPN) via grafted co-polymerization, which holds great potential to combine the advantages of biochar and Semi-IPN when they are used in SRFs. The results show that the as-prepared biochar embedded-Semi-IPN based SRF (BiBe-SRF) exhibits a high water-retention capacity with the value of 73.50% after 25 days, which far outstrips that of Semi-IPN based SRF without the incorporation of biochar. BiBe-SRF also has a better slow-release performance of nutrients than the Semi-IPN based SRF. The release ratios of N, P and K from Semi-IPN based SRF within 30 days reach in the range of 95.5% to 100.0%, but they are less than 80.0% for BiBe-SRF. The degradation ratio for BiBe-SRF is 62.63% after 90 days' degradation experiment which is higher than Semi-IPN based SRF, suggesting that the presence of biochar significantly improves the degradability of BiBe-SRF. Pot experiments reveal that pepper seedlings fertilized by BiBe-SRF grow better than those fertilized by Semi-IPN based SRFs, which further highlights its great potentials for the practical application. The mechanism study suggests that the existence of biochar is beneficial for the formation of improved porous structure and generation of abundant cross-linking points within BiBe-SRF, and it is also responsible for the high hydrophilicity of BiBe-SRF. Overall, this study demonstrates a new route for the development of environment-friendly SRFs with high water retention.

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