12601. 题目: Changes in soil organic carbon and nutrient stocks in conventional selective logging versus reduced-impact logging in rainforests on highly weathered soils in Southern Cameroon
期刊: Forest Ecology and Management
作者: Rodine Tchiofo Lontsi, Marife D. Corre, Oliver van Straaten, Edzo Veldkamp
摘要: Although disturbances associated with selective logging can cause pronounced changes in soil characteristics and nutrient stocks, such information is very limited for highly weathered soils in Africa. We assessed the effects of reduced impact logging (RIL, with a 30-year rotation management plan) and conventional logging (CL, without a management plan) on physical and biochemical characteristics of Ferralsol soils that developed on pre-Cambrian rocks in rainforests of Cameroon. Five to seven months after the logging operations were completed, we mapped the CL and RIL sites and quantified the disturbed areas: felling gaps, skidding trails, logging decks and roads. We selected four replicate plots at each site that encompassed these four disturbed strata and an adjacent undisturbed area as the reference. At each disturbed stratum and reference area per plot, we took soil samples down to 50 cm, and quantified soil physical and biochemical characteristics. Nutrient exports with timber harvest were also quantified.The logging intensity was very low with removals of 0.2 and 0.3 tree per hectare, and the ground area disturbed accounted only 5.2% and 4.0% of the total area in CL and RIL, respectively. In terms of area disturbance for each harvested tree, CL had 753 m2 tree−1 more affected ground area than RIL. Roads and logging decks were the most affected by logging operations, where effective cation exchange capacity, soil organic carbon (SOC), total nitrogen (N), Bray-extractable phosphorus (P) and exchangeable aluminum decreased whereas pH, 15N natural abundance and exchangeable manganese increased compared to the undisturbed reference area (P < 0.01–0.04). The disturbed area showed overall reductions of 21–29% in SOC, N and P stocks relative to the reference areas (P = 0.02–0.07). The amounts of C, N, P and base cations exported with harvested timber were only 0.4–5.9% of the changes in stocks of these elements in the disturbed strata. Nutrient reductions in the soil and exports through timber harvest were comparable between CL and RIL, after one logging event in this very low intensity logging systems. Our results suggest that unplanned operations together with frequent re-logging inherent to CL can increase area damage and enhance changes in SOC and nutrients as opposed to RIL, which may affect the recovery of the succeeding vegetation.
12602. 题目: Soil microaggregate size composition and organic matter distribution as affected by clay content
作者: Steffen A. Schweizer, Franziska B. Bucka, Markus Graf-Rosenfellner, Ingrid Kögel-Knabner
摘要: Aggregation assembles different size mixtures of soil particles into a larger architecture. Such mixtures impede resolving which particles build aggregates and how these control the accumulation of soil organic matter (OM). Here we present an approach to differentiate the size distributions of soil fractions in the size range of microaggregates (<250 μm) from their dispersible particle-size distribution using dynamic image analysis. This approach enabled us to differentiate the magnitude and preferential size ranges of aggregates and non-aggregated particles. Wet sieving was used to isolate free microaggregate-sized fractions. Larger soil structures >250 μm were sonicated to isolate occluded size fractions <250 μm. To investigate the impact of soil texture, we analyzed topsoil samples of an arable site on Cambisol soils with a gradient in clay content of 16–37% and organic carbon concentrations of 10–15 g kg−1. Our results demonstrate how soil texture governs aggregate size distributions: most water-stable microaggregates were found to be of approximately 30 μm diameter, independent of the clay content gradient. High-clay soils contain more water-stable macroaggregates (>250 μm) and larger microaggregates in the 50–180 μm size range. The low-clay soils, on the other hand, contained more non-aggregated sand-sized particles >100 μm which probably hampered the buildup of larger aggregates. The size distribution of particles <100 μm in size fractions <250 μm showed a similar prevailing soil texture pattern, with approximately 24% clay, 59% silt, and 17% sand-sized particles at all clay contents. In contrast to the prevailing texture pattern along the clay content gradient, 4% more clay-sized particles helped build up water-stable macroaggregates. In the low-clay soils, the aggregates were smaller and the size fractions <53 μm had higher OM concentrations. This indicates that the low-clay soils held most of their OM in smaller microaggregates. Such arrangement of OM in smaller microaggregates demonstrates that soil texture may control OM stabilization mostly indirectly via the distribution of OM in different aggregate fractions. The occlusion of microaggregates in larger structures led to lower alkyl:O/N-alkyl ratios in 13C nuclear magnetic resonance (NMR) spectroscopy, indicating increased preservation.
12603. 题目: Modified biochar for phosphate adsorption in environmentally relevant conditions
期刊: Chemical Engineering Journal
作者: Yimin Huang, Xinqing Lee, Matteo Grattieri, Mengwei Yuan, Rong Cai, Florika C. Macazo, Shelley D. Minteer
摘要: Herein, we explored the modification of wheat straw biochar with chitosan, quaternary ammonium salt, and lanthanum for enhanced phosphate removal in environmentally relevant conditions. Specifically, a new amine protected cross-linking method was utilized to modify the absorbent material for maximum adsorption capacity, reaching 109 ± 4 mg P g−1. The high phosphate removal performance of the composite was not significantly affected in a broad range of temperature (15–45 °C) and pH (2.5–7). 30 min allowed reaching a 100% adsorption equilibrium for 100 mg P L−1, and 93% for 25 mg P L−1, thus, significantly reducing the treatment time compared to previous reports. The highest partition coefficient 172.1 mg g−1 μM−1 was obtained at a concentration of 25 mg L−1, and the phosphorus removal rate was as high as 99.98%, indicating La/GTB have great adsorption performance at low phosphate concentration. The adsorption mechanisms of the composite are extensively described, where electrostatic interaction, ligand exchange, and Lewis acid-base interaction contribute to the process. All of the above-mentioned advantages make the prepared composite of great interest for the development of materials for on-site phosphate removal.
12604. 题目: Bacterioplankton community in response to biological filters (clam, biofilm, and macrophytes) in an integrated aquaculture wastewater bioremediation system
期刊: Environmental Pollution
作者: Betina Lukwambe, Li Zhao, Regan Nicholaus, Wen Yang, Jinyong Zhu, Zhongming Zheng
摘要: Integrated systems with appropriate bio-filters can be used to treat aquaculture effluents. However, the information on bio-filters that alters the ecological functions of the bacterioplankton community (BC) in biodegradation of the aquaculture effluents remains controversial. In this study, we implemented a comprehensive restoration technology combined with bio-filters [biofilm, clam (Tegillarca granosa), and macrophytes (Spartina anglica)] to investigate their influence on the stability of the BC and nutrient removal. We found that the diversity of BC was linked with biogeochemical factors in processing and upcycling nitrogen-rich effluents into high-value biomass. The BC exhibited significant distinct patterns in the bio-filter areas. Potential biomarkers for constrained harmfully algae-bacteria (Nitriliruptoraceae, Bacillales, and Rhodobacteraceae) and nutrient removal were significantly higher in the bio-filters areas. The bio-filters significantly promoted the restoration effects of N and P balance by reducing 82.34% of total nitrogen (TN) and 81.64% of total phosphorus (TP) loads at the water interface. The main mechanisms for TN and TP removal and nutrient transformation were achieved by assimilation and absorption by the emergent macrophytes (Spartina anglica). The bio-filters significantly influenced the biodegradability and resolvability of particulate organic matter through ammonification, nitrification, and denitrification of microbes, which meliorated the nutrient removal. Beside bio-filter effects, the BC was significantly controlled by abiotic factors [nitrate (NO3−-N), dissolved oxygen (DO), total nitrogen (TN), and water temperature (WT)], and biotic factors (chlorophyll ɑ and green algae). Our study revealed that the co-existence system with bio-filters may greatly improve our understanding on the ecological functions of the BC in aquaculture systems. Overall, combined bio-filters provide an opportunity for the development of efficient and optimized aquaculture wastewater treatment technology.
12605. 题目: Bacterial community rather than metals shaping metal resistance genes in water, sediment and biofilm in lakes from arid northwestern China
期刊: Environmental Pollution
作者: Wenjuan Song, Ran Qi, Li Zhao, Nana Xue, Liyi Wang, Yuyi Yang
摘要: Lakes in arid northwestern China are valuable freshwater resources that drive socioeconomic development. Environmental pollution can significantly influence the composition of microbial communities and the distribution of functional genes in lakes. This study investigated heavy metal pollution to identify possible correlations with metal resistance genes (MRGs) and bacterial community composition in water, sediment and biofilm samples from Bosten Lake and Ebi Lake in northwestern China. High levels of zinc were detected in all samples. However, the metals detected in the sediment samples of both lakes were determined to be at low risk levels according to an ecological index. The mercury resistance gene subtype merP had the greatest average abundance (4.61 × 10−3 copies per 16S rRNA) among all the samples, followed by merA and merC. The high abundance of merA in the pelagic zone rather than in benthic sediment suggests that the pelagic microbial community was important in mercury reduction. Proteobacteria were the main phylum found in the microbial communities in all samples. However, microbial communities in most of the water, sediment and biofilm samples had different compositions, indicating that the habitat niche plays an important role in shaping the bacterial communities in lakes. The microbial community, rather than the heavy metals, was the main driver of MRG distribution. The abundances of some bacterial genera involved in the decomposition of organic matter and the terrestrial nitrogen cycle were negatively correlated with heavy metals. This result suggests that metal pollution can adversely affect the biogeochemical processes that occur in lakes.
12606. 题目: Transformation of atenolol by a laccase-mediator system: Efficiencies, effect of water constituents, and transformation pathways
期刊: Ecotoxicology and Environmental Safety
作者: Yiping Feng, Mengyao Shen, Zhu Wang, Guoguang Liu
摘要: In this study, we investigated the transformation of atenolol (ATL) by the naturally occurring laccase from Trametes versicolor in aqueous solution. Removal efficiency of ATL via laccase-catalyzed reaction in the presence of various laccase mediators was examined, and found that only the mediator 2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPO) was able to greatly promote ATL transformation. The influences of TEMPO concentration, laccase dosage, as well as solution pH and temperature on ATL transformation efficiency were tested. As TEMPO concentrations was increased from 0 to 2000 μM, ATL transformation efficiency first increased and then decreased, and the optimal TEMPO concentration was determined as 500 μM. ATL transformation efficiency was gradually increased with increasing laccase dosage. ATL transformation was highly pH-dependent with an optimum pH of 7.0, and it was almost constant over a temperature range of 25–50 °C. Humic acid inhibited ATL transformation through competition reaction with laccase. The presence of anions HCO3− and CO32− reduced ATL transformation due to both anions enhanced solution pHs, while Cl−, SO42−, and NO3− at 10 mM showed no obvious influence. The main transformation products were identified, and the potential transformation pathways were proposed. After enzymatic treatment, the toxicity of ATL and TEMPO mixtures was greatly reduced. The results of this study might present an alternative clean strategy for the remediation of ATL contaminated water matrix.
12607. 题目: A review of arsenic interfacial geochemistry in groundwater and the role of organic matter
期刊: Ecotoxicology and Environmental Safety
作者: Jinli Cui, Chuanyong Jing
摘要: Recent discoveries on arsenic (As) biogeochemistry in aquifer-sediment system have strongly improved our understanding of As enrichment mechanisms in groundwater. We summarize here the research results since 2015 focusing on the As interfacial geochemistry including As speciation, transformation, and mobilization. We discuss the chemical extraction and speciation of As in environmental matrices, followed by As redox change and (im)mobilization in typical minerals and aquifer system. Then, the microbial-assisted reductive dissolution of Fe (hydr)oxides and As transformation and liberation are summarized from the aspects of bacterial isolates, microbial community and gene analysis by comparing As rich groundwater cases worldwide. Finally, the potential effect of organic matter on As interfacial geochemistry are addressed in the aspects of chemical interactions and microbial respiring activities for Fe and As reductive release.
12608. 题目: The influence of dissolved organic matter on the marine production of carbonyl sulfide (OCS) and carbon disulfide (CS<sub>2</sub>) in the Peruvian upwelling
期刊: Ocean Science
作者: Sinikka T. Lennartz, Marc von Hobe, Dennis Booge, Henry C. Bittig, Tim Fischer, Rafael Gonçalves-Araujo, Kerstin B. Ksionzek, Boris P. Koch, Astrid Bracher, Rüdiger Röttgers, Birgit Quack, Christa A. Marandino
摘要: Oceanic emissions of the climate-relevant trace gases carbonyl sulfide (OCS) and carbon disulfide (CS2) are a major source to their atmospheric budget. Their current and future emission estimates are still uncertain due to incomplete process understanding and therefore inexact quantification across different biogeochemical regimes. Here we present the first concurrent measurements of both gases together with related fractions of the dissolved organic matter (DOM) pool, i.e., solid-phase extractable dissolved organic sulfur (DOSSPE, n=24, 0.16±0.04 µmol L−1), chromophoric (CDOM, n=76, 0.152±0.03), and fluorescent dissolved organic matter (FDOM, n=35), from the Peruvian upwelling region (Guayaquil, Ecuador to Antofagasta, Chile, October 2015). OCS was measured continuously with an equilibrator connected to an off-axis integrated cavity output spectrometer at the surface (29.8±19.8 pmol L−1) and at four profiles ranging down to 136 m. CS2 was measured at the surface (n=143, 17.8±9.0 pmol L−1) and below, ranging down to 1000 m (24 profiles). These observations were used to estimate in situ production rates and identify their drivers. We find different limiting factors of marine photoproduction: while OCS production is limited by the humic-like DOM fraction that can act as a photosensitizer, high CS2 production coincides with high DOSSPE concentration. Quantifying OCS photoproduction using a specific humic-like FDOM component as proxy, together with an updated parameterization for dark production, improves agreement with observations in a 1-D biogeochemical model. Our results will help to better predict oceanic concentrations and emissions of both gases on regional and, potentially, global scales.
12609. 题目: Organic and chemical amendments positively modulate the bacterial proliferation for effective rhizoremediation of PCBs-contaminated soil
期刊: Ecological Engineering
作者: Ayesha Hayat, Imran Hussain, Gerhard Soja, Mazhar Iqbal, Naeem Shahid, Jabir Hussain Syed, Sohail Yousaf
摘要: Polychlorinated Biphenyls (PCBs) are xenobiotic chlorinated aromatic compounds with high toxicity to both fauna and flora. PCBs can enter the environment through close interactions of multiple environmental matrices such as sediments, soils, water and food web. Biogeochemical cycle of PCBs can transport them far from their initial source of production. The present study aims to investigate the effects of organic and chemical amendments during rhizoremediation of PCBs in aged contaminated soil. Italian ryegrass (Lolium multiflorum) was grown in PCB-contaminated soil, whereas different combinations of two biochar (i.e., beech woodchip and green garden waste) and a surfactant (i.e., sodium dodecyl sulfate) were applied to assess the removal efficiency. The overall system’s performance was evaluated based on plant growth, PCBs degradation, and proliferation of PCBs degrading bacteria after 5-months of sowing of ryegrass. We found that PCBs removal was significantly high in the vegetated soils as compared to the un-vegetated soils. Maximum removal (85% of total PCBs load) was observed in the presence of green garden waste biochar whereas less removal was observed with the surfactant application. The observations on PCBs degrading bacteria and plant growth parameters were consistent with the degradation scheme, which suggest the potential role of bacteria in the overall degradation process. We conclude that appropriate combinations of vegetation, soil amendments, and PCB degrading bacteria can help to improve the degradation of PCBs impacted soils.
12610. 题目: Radiolysis as a source of 13C depleted natural gases in the geosphere
期刊: Organic Geochemistry
作者: Renzo C. Silva, Lloyd R. Snowdon, Haiping Huang, Michael Nightingale, Veith Becker, Stephen Taylor, Bernhard Mayer, Jon H. Pedersen, Rolando di Primio, Steve Larter
摘要: Is natural radioactivity a significant agent of hydrocarbon gas generation from sedimentary organic matter Laboratory gamma radiation of dead crude oil (no solution gas) yields wet hydrocarbon gases depleted in 13C: δ13C CH4 (-75‰ to -65‰), δ13C C2H6 (-52‰ to -45‰), δ13C C3H8 (-42‰ to -37‰) and δ13C C4H10 (-35‰ to -32‰). Although laboratory irradiation dose rates are orders of magnitude higher than those in geological settings, radiolytic transformations occur at total radiation doses equivalent to those in natural geological settings over many millions of years. Radiolysis generates wet gases with isotopic signatures that might be interpreted as “biogenic” if only the methane carbon isotope ratio is considered. We examine situations where such gases may be quantitatively significant.
12611. 题目: Palaeoenvironments, flora, and organic carbon and nitrogen isotope changes across the non-marine Permian-Triassic boundary at Wybung Head, Australia
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Shreya Misra, Neerja Jha, Alan Stebbins, Michael Brookfield, Robyn Hannigan
摘要: The Permian-Triassic boundary section at Wybung Head, eastern Australia shows a rapid change from humid coal-bearing lowland braided stream through a thin clay and coal breccia and paleosols to semi-arid silty floodplain deposits. Identifiable plant remains and total organic matter disappear above the coal and clay breccia. Three characteristic palynofacies accumulated in a range from oxic to sub-oxic to anoxic conditions. The dominance of opaque phytoclasts in the entire sequence reflects deposition under oxic conditions, especially in the sequence lying above the Birdie Coal, the result of fluctuating water tables, high energy and desiccating conditions. In the Birdie Coal, however, at certain horizons, a water-saturated environment favored the preservation of organic matter such as pollen, spores, and structured organic matter. This latest Permian paleovegetation was dominated by opportunistic understory spore-bearing plants, with a canopy of pollen-bearing glossopterids, conifers and cordaitales. Total organic carbon drops from >30% in the coal, through <5% in the breccia to <1% in the paleosols and silts. The organic δ13C values are constant at ~ −25.5‰ in the coal and coal breccia, but then decrease to less than −27‰ in the paleosols and silts. These results confirm the rapid sedimentary, floral and organic carbon isotope changes across the non-marine Permian-Triassic boundary in eastern Australia. Our δ13Corg values suggest a significant and sustained negative δ13Corg excursion, with a magnitude of about 3‰, above the Birdie Coal. Unlike δ13Corg, there is no clear trend in δ15Norg values. The low C/N ratios of 10 and less, of the samples above +55 cm, are only found in modern burned soils with low bacteria/fungi ratios or in decaying wood. There is no obvious fungal spike in the Wybung Head section, may have been destroyed during the formation of this soil B horizon, as elsewhere a global fungal spike layer marks an interval of decreased terrestrial biomass and decaying vegetation associated with the Permian-Triassic crisis and boundary. Two negative excursions in the uppermost Permian and lowest Triassic can be correlated throughout Gondwana.
12612. 题目: Effects of soil organic residue amendment on losses of dissolved organic carbon, P, Cu and Zn via surface runoff from arable soils
期刊: Soil and Tillage Research
作者: Pu Shi, Rainer Schulin
摘要: Dissolved organic carbon (DOC) constitutes the largest carbon pool in surface waters, with soil being its main source via surface and subsurface runoff. Amendment with organic residues can reduce soil erosion and surface runoff, but little is known how this affects the amount and composition of DOC losses via surface runoff and the associated transfer of nutrients and pollutants. In this study, artificial rainfall experiments were conducted on three pairs of soil runoff plots with contrasting organic matter management. A mixture of grass and wheat straw residues was incorporated into the topsoil of one plot in each pair (OI treatment) but not into the other (control). Artificial rainfall was applied onto both treatments at an intensity of 49.1 mm h−1, and surface runoff samples were collected at designated time steps for analysis of DOC, total dissolved phosphorus (TDP), copper (TDCu) and zinc (TDZn) concentrations, as well as for characterization of DOC by UV–vis absorbance (SUVA254 and E2:E3) and fluorescence spectroscopy (FI) indexes. The organic amendment reduced the loss rates of DOC, TDP, TDCu and TDZn by reducing surface runoff, although increasing the concentrations of DOC, TDP and TDCu. Regardless of the treatment, DOC, TDP and TDCu concentrations were always maximal at the onset of runoff and then continuously decreased after the initial flush. The observed relationships of TDP and TDCu concentrations with DOC indicate that the export of “dissolved” P and Cu primarily occurred in DOC-bound form, while the concentration of TDZn was not correlated with that of DOC. Surface runoff from the amended soils generally contained more hydrophilic and low molecular weight DOC (as indicated by low SUVA254 and high E2:E3 and FI values), particularly at high DOC concentrations. The ratio between TDCu and DOC concentration showed a positive relationship to DOC aromaticity (as indicated by SUVA254 values) in the OI treatment. The results indicate that organic amendment can reduce total rates of dissolved element losses with surface runoff, but attention should also be paid to the composition of lost DOC and the concentrations of DOC-associated solutes.
12613. 题目: Effects of fertilization and straw return methods on the soil carbon pool and CO2 emission in a reclaimed mine spoil in Shanxi Province, China
期刊: Soil and Tillage Research
作者: Jianhua Li, Hua Li, Qiang Zhang, Hongbo Shao, Chunhua Gao, Xunzhong Zhang
摘要: Reclaimed soil is similar to an “empty cup” with a large carbon (C) sequestration potential. Agricultural management practices strongly influence C storage and soil carbon dioxide (CO2) emission. The objective of this study was to identify the effects of fertilization and straw return methods on the soil C pool and CO2 emission in a reclaimed mine spoil. Thus, we studied the effects of four fertilization treatments [chemical fertilizer (NP), manure (M), 50% M plus 50% NP (NPM), and unfertilized control (CK)] and three straw return methods [no straw return (no straw), return of straw mixed with soil (straw mixing), and return of straw to the surface of the soil (straw mulching)] in a mine reclamation region by examining changes in the soil C pool and CO2 emission. The soil C pool was evaluated by acid hydrolysis, considering three pools: (a) labile pool I (LP I), obtained by hydrolysis with 5 N H2SO4 at 105 °C for 30 min; (b) labile pool II (LP II), obtained by hydrolysis with 26 N H2SO4 at room temperature overnight, followed by 2 N H2SO4 at 105 °C for 3 h; and (c) the recalcitrant pool, measured as the unhydrolyzed residue. The CO2 emission/C sequestration and CO2 emission/grain yield ratios were used as indicators of C emission. Compared with the CK, the NPM treatment was the most efficient among the fertilization treatments in increasing grain yield (136%) and C sequestration (311%) and reducing the CO2 emission/C sequestration (62%) and CO2 emission/grain yield (32%) ratios. The straw mixing treatment had more soil organic carbon (SOC), a larger LP I and LP II, and more C sequestration than the other straw return treatments. The addition of manure resulted in a higher distribution rate of new organic C to the labile C pool (73–78%) than the addition of inorganic fertilizer (45%). Soil C emissions were mainly concentrated in the maize growing season, accounting for more than 80% of the total annual C emissions. LP I, LP II and CO2 emission were significantly positive correlated with SOC and yield. Therefore, soil C pools and CO2 emissions are significantly influenced by fertilization regimes and straw return methods, which should be used to important indicators to estimate the C balance in agro-ecosystems during the process of mine spoil reclamation.
12614. 题目: Seasonal variation, source apportionment and source attributed health risk of fine carbonaceous aerosols over National Capital Region, India
作者: Shivani, Ranu Gadi, Sudhir Kumar Sharma, Tuhin Kumar Mandal
摘要: Deteriorating air quality with high levels of fine particulate matter (PM2.5) over National Capital Region (NCR) of India is one of the serious environmental and scientific issues. In this paper, PM2.5 samples were collected for 24 h twice or thrice a week during December 2016–December 2017 at three sites [Delhi (IG), Modinagar (MN) and Mahendragarh (HR)] over NCR to analyse the carbonaceous aerosols. Source apportionment of PM2.5 was attempted using Principal Component analysis (PCA) and Positive Matrix Factorization (PMF) based on the analysed carbonaceous fractions [Organic carbon, Elemental carbon, Secondary organic carbon (SOC)]. Organic compounds: alkanes, hopanes, steranes, polycyclic aromatic hydrocarbons (PAHs), phthalates, levoglucosan and n-alkanoic acids were analysed to distinguish the emission sources. Total Carbonaceous Aerosols (TCA) contributed significantly (∼26%) to PM2.5 which revealed their importance in source apportionment. Estimated SOC contributed 43.2%, 42.2% and 58.2% to OC and 5.4%, 5.3% and 7.8% to PM2.5 at IG, MN and HR sites respectively. PCA and PMF apportion five emission sources i.e., vehicular emissions (34.6%), biomass burning (26.8%), cooking emissions (15.7%), plastic and waste burning (13.5%) and secondary organic carbon (9.5%) for PM2.5. Source attributed health risk has also been calculated in terms of Lung cancer risk (LCR) associated with PAHs exposure and concluded that vehicular emissions (40.3%), biomass burning (38.1%), secondary organic carbon (12.8%) contributed higher to LCR (503.2 × 10−5; ∼503 cases in 1,00,000). Health risk assessment combined with source apportionment inferences signifies the immediate implementation of emissions reduction strategies with special target on transport sector and biomass burning over the NCR of India.
12615. 题目: High time resolution observation of PM2.5 Brown carbon over Xi'an in northwestern China: Seasonal variation and source apportionment
作者: Yali Lei, Zhenxing Shen, Tian Zhang, Di Lu, Yaling Zeng, Qian Zhang, Hongmei Xu, Naifang Bei, Xin Wang, Junji Cao
摘要: There is growing evidence suggesting the enhancement of brown carbon (BrC) in severe haze episodes. In this study, hourly measurements of BrC in PM2.5 were conducted in Xi'an, a typical city in northwestern China during winter and summer. The absorption coefficient for methanol exacts at 365 nm (babs365, methanol, which is typically used as a proxy of methanol-soluble BrC) in the winter sampling period was over 7 times than that in summer. The mass absorption cross-section for methanol extracts (MAC365, methanol, normalized by babs365, methanol to organic carbon, OC) in winter sampling period was nearly 1.5 times of that in the summer. During the winter haze days, the average babs365, methanol peaked at midnight and the lowest values in the morning, in contrast to high levels in afternoon and low levels at night in non haze days. Unlike the diurnal patterns in winter, summer babs365, methanol diurnal variation presented high midday and low afternoon levels in haze days. However, in non haze days, the pattern showed high morning levels and night low levels. Haze and non haze variations of chemical species levels, babs365, methanol, and MAC365, methanol during winter and summer sampling time showed that the effects of atmospheric aging were complex and could either enhance or reduce light absorption of BrC. Source apportionment based on positive matrix factorization receptor model and multiple linear regressions showed that primary emission was an important contributor to BrC emissions during the winter sampling period, whereas secondary formation played an important role in summer.
12616. 题目: On the origin of aged sedimentary organic matter along a river‐shelf‐deep ocean transect
期刊: Journal of Geophysical Research: Biogeosciences
作者: Rui Bao, Meixun Zhao, Ann McNichol, Ying Wu, Xinyu Guo, Negar Haghipour, Timothy I. Eglinton
摘要: To assess the influences of carbon sources and transport processes on the 14C age of organic matter (OM) in continental margin sediments, we examined a suite of samples collected along a river‐shelf‐deep ocean transect in the East China Sea (ECS). Ramped pyrolysis‐oxidiation was conducted on suspended particulate matter in the Yangtze River and on surface sediments from the ECS shelf and northern Okinawa Trough. 14C ages were determined on OM decomposition products within different temperature windows. These measurements suggest that extensive amounts of pre‐old (i.e., millennial age) organic carbon (OC) are subject to degradation within and beyond the Yangtze River Delta, and this process is accompanied by an exchange of terrestrial and marine OM. These results, combined with fatty acid concentration data, suggest that both the nature and extent of OM preservation/degradation as well as the mode of transport influence the 14C ages of sedimentary OM. Additionally, we find that the age of (thermally) refractory OC increases during across‐shelf transport and that the age offset between the lowest and highest temperature OC decomposition fractions also increases along the shelf‐to‐trough transect. Amplified inter‐fraction spread or 14C heterogeneity is the greatest in the Okinawa Trough. Aged sedimentary OM across the transect may be a consequence of several reasons including fossil OC input, selective degradation of younger OC, hydrodynamic sorting processes, and aging during lateral transport. Consequently, each of them should be considered in assessing the 14C results of sedimentary OM and its implications for the carbon cycle and interpretation of sedimentary records.
12617. 题目: Sedimentary organic carbon budget across the slope to the basin in the southwestern Ulleung (Tsushima) Basin of the East (Japan) Sea
期刊: Journal of Geophysical Research: Biogeosciences
作者: Jae Seong Lee, Jeong Hee Han, Sung‐Uk An, Sung‐Han Kim, Dhongil Lim, Dongseon Kim, Dong‐Jin Kang, Young‐Kyu Park
摘要: With the total sediment oxygen uptake rates measured using an in situ benthic chamber, vertical distributions of organic carbon and sedimentation rates estimated by excess 210Pb across the slope to the basin sediment of the southwestern region of the Ulleung (Tsushima) Basin (UB), the partitioning of organic carbon fluxes in the sediment was estimated to understand the biogeochemical cycles of organic carbon in the high productivity marginal sea. The results of depth attenuation of total oxygen uptake (TOU) demonstrate that the organic carbon oxidation of the UB sediment was 2.5 times higher than that obtained from the empirical relationship of the global's depth attenuation of TOU. Similar to TOU, the high mass accumulation rates observed in the slope region were 9.5 times higher than the rate in the basin, indicating that the slope may act as the depocenter of organic carbon. The organic carbon budget with water depth gradient implies that a significant fraction of the organic carbon deposited into sediment is supplied by lateral transport down the slope. Definite increasing C/N ratio with water depth indicates the refractory organic carbon seems to be successively transported later from shelf to slope. The total burial flux in the sediment of southwestern UB was estimated to be 0.46±0.04 Tg C y–1, which is similar to the megadepocenter of the Congo River fan. Our results imply that the UB sediment may be an important biogeochemical reaction place, not only for organic carbon but also materials linked to primary production.
12618. 题目: Validation and application of diphenylamine method for DNA detection into soils and clay minerals
期刊: Journal of Soils and Sediments
作者: Amira Lajmi, Isabelle Bourven, Emmanuel Joussein, Stéphane Simon, Marilyne Soubrand, Mounir Mehdioub
摘要: Purpose: Soil provides important ecosystemic services, in particular through its biodiversity, which plays a major role for humans. It is therefore essential to detect and, above all, quantify soil DNA in order to better understand and conserve this biodiversity. However, the techniques commonly used are not specific and do not always allow an easy and reliable detection in complex matrices rich in organic matter. The aim of this article is to develop an effective method to quantify DNA whatever the type of soil matrix. Materials and methods: Two reference clays (kaolinite and montmorillonite which are ubiquitous in soils but present very different physicochemical properties) and two soils (Cambisols and Andosols with different mineralogy, organic matter content, and properties) were used for this purpose. The developed method, based on the use of diphenylamine with colorimetric detection at 600 nm, was compared to the traditional method (absorption at 260 nm). Results and discussion: The results highlight the independence of the method in terms of organic matter content or soil type, as well as its simplicity and low cost. It opens up important possibilities of application, such as a better understanding of the interactions between DNA and mineral supports, as well as the effects of mineral species. As an illustration, the method was applied to study the sorption of calf thymus DNA on various substrates with or without humic acid for a specific concentration. DNA sorption has been successfully adjusted by the Langmuir model. Conclusions: The method is specific and can be easily used in complex matrices commonly found in soils, regardless of the different properties in terms of mineralogical content, presence of organic matter, or physicochemical properties.
12619. 题目: The role of laccase in stabilization of soil organic matter by iron in various plant-dominated peatlands: degradation or sequestration?
期刊: Plant and Soil
作者: Yunpeng Zhao, Wu Xiang, Ming Ma, Xiuzhi Zhang, Zhengyu Bao, Shuyun Xie, Sen Yan
摘要: Aims: The association of organic matter with iron (Fe-OM associations) is recognized as an important stabilization mechanism for soil organic matter. Our objective was to assess the factors regulating stabilization of soil organic matter by iron in various plant-dominated peatlands, and the role of laccase in the formation of Fe-OM associations. Methods: We investigated Fe-bound OC content and related physicochemical and biochemical parameters in four plots with different successional vegetation, and a set of simulations was conducted to investigate the association of Fe and peat-derived dissolved organic carbon catalysed by laccase. Results: Our results indicate Fe-bound OC content varies regularly with the succession gradients, and a significant positive relationship between laccase activities and Fe-bound OC content was found (R = 0.77, P < 0.05). Although laccase degradation of recalcitrant polyphenolics is related with the CO2 release from peat soils (R = 0.697; P < 0.05), the simulation results confirmed laccase can significantly promote the formation of Fe-OM association. Conclusions: We propose that laccase plays a unique multifunctional role in the peatland carbon cycle. That is, while laccase degrades refractory organic matter such as lignin, it may enhance carbon sequestration by promoting the formation of Fe-OM association, which is particularly effective in acidic peat environments containing abundant iron and laccase-producing fungi.
12620. 题目: In situ transformations of bonechar and tri-poly phosphate amendments in phosphorus-limited subsurface soils
期刊: Applied Geochemistry
作者: Jordan G. Hamilton, Jay Grosskleg, David Hilger, Gurbir Singh Dhillon, Kris Bradshaw, Trevor Carlson, Steven D. Siciliano, Derek Peak
摘要: Nutrient availability is a key factor for the in situ bioremediation of petroleum hydrocarbon contaminated (PHC) soils. Phosphorus deficiencies in calcium rich PHC soils can often be challenging, as amendment P rapidly forms new mineral phases. In situ bioreactors were used to determine the chemical fate of several P amendments (ortho-P, tripolyphosphate, fishmeal and bonemeal biochar), which are currently under consideration to address P nutrient deficiencies during PHC remediation. Contaminated and uncontaminated soil from the study site were treated with the P amendments then suspended in onsite bioreactors (contaminated and uncontaminated). Amendment fate and transformation was determined utilizing a combination of bulk and micro-focused X-ray diffraction (XRD), P X-ray absorption near edge structure (XANES), and X-ray fluorescence imaging (XFI). The ortho-P amendment was found to rapidly precipitate as a Mg-brushite species, proposed as a surface precipitate on dolomite mineral surfaces. Tripolyphosphate increased the adsorbed P fraction through direct adsorption to mineral surfaces and displayed evidence of surface hydrolysis over time with subsequent formation of surface precipitated Mg-brushite. Both P rich biochars demonstrated a potential for dissolution and incorporation of Mg ions, resulting in increased fractions of Mg-brushite and newberyite on the edges of the biochar particles. Tripolyphosphate is an effective short-term P amendment; as there was an increased adsorbed P fraction without the formation of precipitate species until after hydrolysis. In contrast, biochars are potentially an effective long-term amendment, as significant time is required for mineral dissolution to occur and increase the P nutrient status of subsurface soils.