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Gao H, Xi Y, Wu X, Pei X, Liang G, Bai J, Song X, Zhang M, Liu X, Han Z, Zhao G, Li S. Partial substitution of manure reduces nitrous oxide emission with maintained yield in a winter wheat crop. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2023; 326:116794. [PMID: 36403458 DOI: 10.1016/j.jenvman.2022.116794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 11/08/2022] [Accepted: 11/12/2022] [Indexed: 06/16/2023]
Abstract
Conventional fertilization of agricultural soils results in increased N2O emissions. As an alternative, the partial substitution of organic fertilizer may help to regulate N2O emissions. However, studies assessing the effects of partial substitution of organic fertilizer on both N2O emissions and yield stability are currently limited. We conducted a field experiment from 2017 to 2021 with six fertilizer regimes to examine the effects of partial substitution of manure on N2O emissions and yield stability. The tested fertilizer regimes, were CK (no fertilizer), CF (chemical fertilizer alone, N 300 kg ha-1, P2O5 150 kg ha-1, K2O 90 kg ha-1), CF + M (chemical fertilizer + organic manure), CFR (chemical fertilizer reduction, N 225 kg ha-1, P2O5 135 kg ha-1, K2O 75 kg ha-1), CFR + M (chemical fertilizer reduction + organic manure), and organic manure alone (M). Our results indicate that soil N2O emissions are primarily regulated by soil mineral N content in arid and semi-arid regions. Compared with CF, N2O emissions in the CF + M, CFR, CFR + M, and M treatments decreased by 16.8%, 23.9%, 42.0%, and 39.4%, respectively. The highest winter wheat yields were observed in CF, followed by CF + M, CFR, and CFR + M. However, the CFR + M treatment exhibited lower N2O emissions while maintaining high yield, compared with CF. Four consecutive years of yield data from 2017 to 2021 illustrated that a single application of organic fertilizer resulted in poor yield stability and that partial substitution of organic fertilizer resulted in the greatest yield stability. Overall, partial substitution of manure reduced N2O emissions while maintaining yield stability compared with the synthetic fertilizer treatment during the wheat growing season. Therefore, partial substitution of manure can be recommended as an optimal N fertilization regime for alleviating N2O emissions and contributing to food security in arid and semi-arid regions.
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Ye J, Gao H, Wu J, Yang G, Duan L, Yu R. Long-term exposure to nano-TiO 2 interferes with microbial metabolism and electron behavior to influence wastewater nitrogen removal and associated N 2O emission. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 311:119930. [PMID: 35970347 DOI: 10.1016/j.envpol.2022.119930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/04/2022] [Accepted: 08/06/2022] [Indexed: 06/15/2023]
Abstract
The extensive use of nano-TiO2 has caused concerns regarding their potential environmental risks. However, the stress responses and self-recovery potential of nitrogen removal and greenhouse gas N2O emissions after long-term nano-TiO2 exposure have seldom been addressed yet. This study explored the long-term effects of nano-TiO2 on biological nitrogen transformations in a sequencing batch reactor at four levels (1, 10, 25, and 50 mg/L), and the reactor's self-recovery potential was assessed. The results showed that nano-TiO2 exhibited a dose-dependent inhibitory effect on the removal efficiencies of ammonia nitrogen and total nitrogen, whereas N2O emissions unexpectedly increased. The promoted N2O emissions were probably due to the inhibition of denitrification processes, including the reduction of the denitrifying-related N2O reductase activity and the abundance of the denitrifying bacteria Flavobacterium. The inhibition of carbon source metabolism, the inefficient electron transfer efficiency, and the electronic competition between the denitrifying enzymes would be in charge of the deterioration of denitrification performance. After the withdrawal of nano-TiO2 from the influent, the nitrogen transformation efficiencies and the N2O emissions of activated sludge recovered entirely within 30 days, possibly attributed to the insensitive bacteria survival and the microbial community diversity. Overall, this study will promote the current understanding of the stress responses and the self-recovery potential of BNR systems to nanoparticle exposure.
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Rõõm EI, Lauringson V, Laas A, Kangro K, Viik M, Meinson P, Cremona F, Nõges P, Nõges T. Summer greenhouse gas fluxes in different types of hemiboreal lakes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 843:156732. [PMID: 35716743 DOI: 10.1016/j.scitotenv.2022.156732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 06/07/2022] [Accepted: 06/12/2022] [Indexed: 06/15/2023]
Abstract
Lakes are considered important regulators of atmospheric greenhouse gases (GHG). We estimated late summer open water GHG fluxes in nine hemiboreal lakes in Estonia classified under different lake types according to the European Water Framework Directive (WFD). We also used the WFD typology to provide an improved estimate of the total GHG emission from all Estonian lakes with a gross surface area of 2204 km2 representing 45,227 km2 of hemiboreal landscapes (the territory of Estonia). The results demonstrate largely variable CO2 fluxes among the lake types with most active emissions from Alkalitrophic (Alk), Stratified Alkalitrophic (StratAlk), Dark Soft and with predominant binding in Coastal, Very Large, and Light Soft lakes. The CO2 fluxes correlated strongly with dissolved CO2 saturation (DCO2) values at the surface. Highest CH4 emissions were measured from the Coastal lake type, followed by Light Soft, StratAlk, and Alk types; Coastal, Light Soft, and StratAlk were emitting CH4 partly as bubbles. The only emitter of N2O was the Alk type. We measured weak binding of N2O in Dark Soft and Coastal lakes, while in all other studied lake types, the N2O fluxes were too small to be quantified. Diversely from the common viewpoint of lakes as net sources of both CO2 and CH4, it turns out from our results that at least in late summer, Estonian lakes are net sinks of both CO2 alone and the sum of CO2 and CH4. This is mainly caused by the predominant CO2 sink function of Lake Peipsi forming ¾ of the total lake area and showing negative net emissions even after considering the Global Warming Potential (GWP) of other GHGs. Still, by converting CH4 data into CO2 equivalents, the combined emission of all Estonian lakes (8 T C day-1) is turned strongly positive: 2720 T CO2 equivalents per day.
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Ding K, Luo J, Clough TJ, Ledgard S, Lindsey S, Di HJ. In situ nitrous oxide and dinitrogen fluxes from a grazed pasture soil following cow urine application at two nitrogen rates. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156473. [PMID: 35660610 DOI: 10.1016/j.scitotenv.2022.156473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 05/18/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Cattle grazing of pastures deposits urine onto the pasture soil at high nitrogen (N) rates that exceed the pasture's immediate N demands, increasing the risk of N loss. Nitrous oxide (N2O), a greenhouse gas, and dinitrogen (N2) are lost from the cattle urine patches. There is limited information on the in situ loss of N2 from grazed-pasture systems which is needed for understanding pasture soil N dynamics and balances. The 15N flux method was used to determine N2 and N2O fluxes over time following synthetic urine-15N application at either 400 or 800 kg N ha-1 to a grazed perennial pasture soil. Results showed that daily N2O fluxes were higher under 800 kg N ha-1 than under 400 kg N ha-1, but there was no significant difference in N2 fluxes. Cumulative N2O emissions from soil with 400 kg N ha-1 and 800 kg N ha-1 applied represented 0.16 ± 0.08% and 0.43 ± 0.08% of deposited N, respectively, while emitted N2 accounted for 32.1 ± 4.1% and 14.4 ± 1.7%, respectively, over 95 days after urine application. Codenitrification and denitrification co-occurred, with denitrification accounting for 97.9 to 98.5% of total N2 production. Recovery of urine-15N in pasture decreased with increasing N rate with 14.7 ± 0.5% and 9.9 ± 0.8% recovered at 400 and 800 kg N ha-1, respectively after 95 days. The N2O/(N2 + N2O) product ratio was generally higher during periods of nitrification of urine-N (the first month after urine application) but with no clear relationship to other measured variables. Contrary to our hypothesis, an elevated urine-N rate did not enhance N2 loss. This is speculated to be due to enhanced ammonia volatilisation and transfer of N as nitrate, to deeper soil layers. Soil relative gas diffusivity indicated that high N2 fluxes resulted from entrapped N2 diffusing from the draining soil.
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Tang Z, Liu X, Li G, Liu X. Mechanism of biochar on nitrification and denitrification to N 2O emissions based on isotope characteristic values. ENVIRONMENTAL RESEARCH 2022; 212:113219. [PMID: 35390305 DOI: 10.1016/j.envres.2022.113219] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 03/13/2022] [Accepted: 03/27/2022] [Indexed: 06/14/2023]
Abstract
To clarify the mechanism of biochar on nitrification and denitrification to N2O emissions in farmland soil, the effects of combined application of biochar and different nitrogen sources on the contributions of nitrification and denitrification to N2O emissions were studied using isotope characteristic values. The results showed that the soil N2O emissions from ammonium nitrogen fertilizer treatments were significantly higher than that from nitrate nitrogen fertilizer treatments. The biochar combined with ammonium nitrogen fertilizer reduced soil N2O emissions by 31.0%-30.8%, and biochar combined with nitrate nitrogen fertilizer reduced soil N2O emissions by 70.6%-63.0%. The isotope model showed that the application of ammonium nitrogen fertilizer was more favorable for soil nitrification in the early stage of the experiment (0-2 d), and more favorable for denitrification in the middle and later stages of the experiment (3-17 d). Application of nitrate nitrogen fertilizer enhanced the nitrification of soil nitrifying bacteria in the early and middle stages of the experiment (0-8 d), and the denitrification of soil denitrifying bacteria in the later stage of the experiment (9-17 d). The effects of biochar on N2O emissions were mainly in the middle and later stages of the experiment by promoting the nitrification of nitrifying bacteria and inhibiting denitrification of denitrifying bacteria, so as to reduce N2O emission in soil. These results may help to understand the mitigation mechanism of biochar on N2O emission in upland soil.
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Mousavian P, Esrafili MD, Sardroodi JJ. Oxidation of methane and ethylene over Al incorporated N-doped graphene: A comparative mechanistic DFT study. J Mol Graph Model 2022; 117:108284. [PMID: 35987185 DOI: 10.1016/j.jmgm.2022.108284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 07/17/2022] [Accepted: 07/26/2022] [Indexed: 10/15/2022]
Abstract
It is generally recognized that developing effective methods for selective oxidation of hydrocarbons to generate more useful chemicals is a major challenge for the chemical industry. In the present study, density functional theory calculations are conducted to examine the catalytic partial oxidation of methane (CH4) and ethylene (C2H4) by nitrous oxide (N2O) over Al-incorporated porphyrin-like N-doped graphene (AlN4-Gr). Adsorption energies for the most stable configurations of CH4, C2H4, and N2O molecules over the AlN4-Gr catalyst are determined to be -0.25, -0.64, and -0.40 eV, respectively. According to our findings, N2O can be efficiently split into N2 and Oads species with a negligible activation energy on the AlN4-Gr surface. Meanwhile, CH4 and C2H4 molecules compete for reaction with the activated oxygen atom (Oads) that stays on the surface. The energy barriers for partial methane oxidation through the CH4 + Oads → CH3° + HOads and CH3° + HOads → CH3OH reaction steps are 0.16 eV and 0.27 eV, respectively. Furthermore, the produced CH3OH may be overoxidized by Oads to give formaldehyde and water molecules by overcoming a relatively low activation barrier. The activation barriers for C2H4 epoxidation are small and comparable to those for CH4 oxidation, implying that AlN4-Gr is highly active for both reactions. The high energy barrier for the 1,2-hydrogen shift in the OCH2CH2 intermediate, on the other hand, makes the production of acetaldehyde impossible under normal conditions. According to the population analysis, the AlN4-Gr serves as a strong electron donor to aid in the charge transfer between the Al atom and the Oads moiety, which is necessary for the activation of CH4 and C2H4. The findings of the present study may pave the way for a better understanding of the catalytic oxidation the CH4 and C2H4, as well as for the development of highly efficient noble-metal free catalysts for these reactions.
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Zheng Q, Ding J, Lin W, Yao Z, Li Q, Xu C, Zhuang S, Kou X, Li Y. The influence of soil acidification on N 2O emissions derived from fungal and bacterial denitrification using dual isotopocule mapping and acetylene inhibition. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 303:119076. [PMID: 35240268 DOI: 10.1016/j.envpol.2022.119076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 01/20/2022] [Accepted: 02/26/2022] [Indexed: 06/14/2023]
Abstract
Denitrification, as both origins and sinks of N2O, occurs extensively, and is of critical importance for regulating N2O emissions in acidified soils. However, whether soil acidification stimulates N2O emissions, and if so for what reason contributes to stimulate the emissions is uncertain and how the N2O fractions from fungal (ffD) and bacterial (fbD) denitrification change with soil pH is unclear. Thus, a pH gradient (6.2, 7.1, 8.7) was set via manipulating cropland soils (initial pH 8.7) in North China to illustrate the effect of soil acidification on fungal and bacterial denitrification after the addition of KNO3 and glucose. For source partitioning, we used and compared SP/δ18O mapping approach (SP/δ18O MAP) and acetylene inhibition technique combined isotope two endmember mixing model (AIT-IEM). The results showed significantly higher N2O emissions in the acidified soils (pH 6.2 and pH 7.1) compared with the initial soil (pH 8.7). The cumulative N2O emissions during the whole incubation period (15 days) ranged from 7.1 mg N kg-1 for pH 8.7-18.9 mg N kg-1 for pH 6.2. With the addition of glucose, relative to treatments without glucose, this emission also increased with the decrement of pH values, and were significantly stimulated. Similarly, the highest N2O emissions and N2O/(N2O + N2) ratios (rN2O) were observed in the pH 6.2 treatment. But the difference was the highest cumulative N2O + N2 emissions, which were recorded in the pH 7.1 treatment based on SP/δ18O MAP. Based on both approaches, ffD values slightly increased with the acidification of soil, and bacterial denitrification was the dominant pathway in all treatments. The SP/δ18O MAP data indicated that both the rN2O and ffD were lower compared to AIT-IEM. It has been known for long that low pH may lead to high rN2O of denitrification and ffD, but our documentation of a pervasive pH-control of rN2O and ffD by utilizing combined SP/δ18O MAP and AIT-IEM is new. The results of the evaluated N2O emissions by acidified soils are finely explained by high rN2O and enhanced ffD. We argue that soil pH management should be high on the agenda for mitigating N2O emissions in the future, particularly for regions where long-term excessive nitrogen fertilizer is likely to acidify the soils.
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Fang W, Wang Q, Li Y, Hua J, Jin X, Yan D, Cao A. Microbial regulation of nitrous oxide emissions from chloropicrin-fumigated soil amended with biochar. JOURNAL OF HAZARDOUS MATERIALS 2022; 429:128060. [PMID: 35236032 DOI: 10.1016/j.jhazmat.2021.128060] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 12/06/2021] [Accepted: 12/07/2021] [Indexed: 06/14/2023]
Abstract
The microbial mechanism underpinning biochar's ability to reduce emissions of the potent greenhouse gas nitrous oxide (N2O) is little understood. We combined high-throughput gene sequencing with a dual-label 15N-18O isotope to examine microbial mechanisms operative in biochar made from Crofton Weed (BC1) or pine wood pellets (BC2) and the N2O emissions from those biochar materials when present in chloropicrin (CP)-fumigated soil. Both BC1 and BC2 reduced N2O total emissions by 62.9-71.9% and 48.8-52.0% in CP-fumigated soil, respectively. During the 7-day fumigation phase, however, both BC1 and BC2 increased N2O production by significantly promoting nirKS and norBC gene abundance, which indicated that the N2O emission pathway had switched from heterotrophic denitrification to nitrifier denitrification. During the post-fumigation phase, BC1 and BC2 significantly decreased N2O production as insufficient nitrogen was available to support rapid population increases of nitrifying or denitrifying bacteria. BC1 and BC2 significantly reduced CP's inhibition of nitrifying archaeal bacteria (AOA, AOB) and the denitrifying bacterial genes (nirS, nirK, nosZ), which promoted those bacterial populations in fumigated soil to similar levels observed in unfumigated soil. Our study provided insight on the impact of biochar and microbes on N2O emissions.
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Abdalla M, Espenberg M, Zavattaro L, Lellei-Kovacs E, Mander U, Smith K, Thorman R, Damatirca C, Schils R, Ten-Berge H, Newell-Price P, Smith P. Does liming grasslands increase biomass productivity without causing detrimental impacts on net greenhouse gas emissions? ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 300:118999. [PMID: 35176412 DOI: 10.1016/j.envpol.2022.118999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 02/03/2022] [Accepted: 02/13/2022] [Indexed: 06/14/2023]
Abstract
Soil acidification has negative impacts on grass biomass production and the potential of grasslands to mitigate greenhouse gas (GHG) emissions. Through a global review of research on liming of grasslands, the objective of this paper was to assess the impacts of liming on soil pH, grass biomass production and total net GHG exchange (nitrous oxide (N2O), methane (CH4) and net carbon dioxide (CO2)). We collected 57 studies carried out at 88 sites and covering different countries and climatic zones. All of the studies examined showed that liming either reduced or had no effects on the emissions of two potent greenhouse gases (N2O and CH4). Though liming of grasslands can increase net CO2 emissions, the impact on total net GHG emission is minimal due to the higher global warming potential, over a 100-year period, of N2O and CH4 compared to that of CO2. Liming grassland delivers many potential advantages, which justify its wider adoption. It significantly ameliorates soil acidity, increases grass productivity, reduces fertiliser requirement and increases species richness. To realise the maximum benefit of liming grassland, we suggest that acidic soils should be moderately limed within the context of specific climates, soils and management.
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Meng T, Wei Q, Yang Y, Cai Z. The influences of soil sulfate content on the transformations of nitrate and sulfate during the reductive soil disinfestation (RSD) process. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 818:151766. [PMID: 34801506 DOI: 10.1016/j.scitotenv.2021.151766] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 11/02/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
The transformations and products of sulfate (SO42-) and nitrate (NO3-), especially the influences of SO42- content on the transformations during RSD process, are unclear. In this study, a series of soil SO42- contents (from 333 to 3000 mg S kg-1) were prepared before RSD treatment. The results indicated that nearly all the cumulative NO3- (>98.6%) was removed and not affected by the soil SO42- content. The 15N recovery results showed that 0.57-1.24% and 2.94-4.59% of NO3- translated into ammonium (NH4+) and organic N, respectively, and high SO42- contents stimulated the processes of NO3- dissimilatory reduction and NO3- immobilization. The soluble SO42- contents decreased by 397-922 mg S kg-1, but the contents of total sulfur, sulfide, and sulfate precipitation varied slightly after RSD, indicating that the decreased SO42- was mainly immobilized into organic sulfur in all soils. In addition, a fraction of decreased SO42- was adsorbed to the soil with a relatively high SO42- content. The leaching of SO42- was high (42.9-602 mg S kg-1) during the RSD process, and the leaching amounts increased with increasing soil SO42- content. In terms of the gases emitted from the transformations of NO3- and SO42-, the cumulative emissions of nitrous oxide (N2O) and six sulfurous gases (hydrogen sulfide, carbonyl sulfide, carbon disulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide) were in the ranges of 17.1-21.2 mg N kg-1 and 7.78-23.5 μg S kg-1, respectively, during the whole RSD process. The emissions of sulfurous gases were inhibited by high soil SO42- content, but the N2O emissions were unaffected. In conclusion, the soil SO42- content influenced the transformations of NO3- and SO42- during RSD process, and the SO42- leaching and N2O emissions might threaten the environment which should be concerned.
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Wu L, Wang LK, Wei W, Ni BJ. Autotrophic denitrification of NO for effectively recovering N 2O through using thiosulfate as sole electron donor. BIORESOURCE TECHNOLOGY 2022; 347:126681. [PMID: 34999195 DOI: 10.1016/j.biortech.2022.126681] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/29/2021] [Accepted: 01/01/2022] [Indexed: 06/14/2023]
Abstract
To reclaim nitrous oxide (N2O) as an energy resource economically, this study developed an autotrophic denitrification-based system with thiosulfate (S2O32-) and nitric oxide (NO) as electron donor and acceptor, respectively. NO from flue gases is absorbed on Fe(II)EDTA to overcome its low solubility in liquid phase by forming Fe(II)EDTA-NO. Short-term batch tests and long-term continuous experiments were conducted to investigate the N2O production profile and NO conversion efficiency from thiosulfate-based denitrification under varied Fe (II)EDTA-NO conditions (5-20 mM). Up to 39% of NO was converted to gaseous N2O at 20 mM Fe(II)EDTA-NO amid batch test due to the inhibition of key enzymatic activities by NO and the acidic conditions following thiosulfate oxidation. Higher Fe(II)EDTA-NO levels induced lower enzymatic activities with N2OR being suppressed harder than NOR. Microbial diversity was reduced in the continuous thiosulfate-driven Fe(II)EDTA-NO-based denitrification system. NO-resistant bacteria and sulfide-tolerant denitrifiers were enriched, facilitating NO conversion to N2O thereafter.
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Yang P, Luo L, Tang KW, Lai DYF, Tong C, Hong Y, Zhang L. Environmental drivers of nitrous oxide emission factor for a coastal reservoir and its catchment areas in southeastern China. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2022; 294:118568. [PMID: 34838712 DOI: 10.1016/j.envpol.2021.118568] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 11/19/2021] [Accepted: 11/20/2021] [Indexed: 06/13/2023]
Abstract
While Asia is projected to be one of the major nitrous oxide (N2O) sources in the coming decades, a more accurate assessment of N2O budget has been hampered by low data resolution and poorly constrained emission factor (EF). Since urbanized coastal reservoirs receive high nitrogen loads from diverse sources across a heterogeneous landscape, the use of a single fixed EF may lead to large errors in N2O assessment. In this study, we conducted high spatial resolution sampling of dissolved N2O, nitrate-nitrogen (NO3--N) and other physico-chemical properties of surface water in Wenwusha Reservoir and other types of water bodies (river, drainage channels, and aquaculture ponds) in its catchment areas in southeastern China between November 2018 and June 2019. The empirically derived EF (calculated as N2O-N:NO3--N) for the reservoir showed considerable spatial variations, with a 10-fold difference ranging from 0.8 × 10-3 to 8.8 × 10-3. The average EF varied significantly among the four types of water bodies in the following descending order: aquaculture ponds > river > drainage channels > reservoir. Across all the water bodies, the mean EF in summer was 1.8-3.5 and 1.7-2.8 fold higher than that in autumn and spring, respectively, owing to the elevated water temperature. Overall, our derived EF deviated considerably from the IPCC default value, which implied that the use of default EF could result in over- or under-estimation of N2O emissions by up to 42%. We developed a multiple regression model that could explain 82% of the variance in EF based on water temperature and the ratio between dissolved organic carbon and nitrate-nitrogen (p < 0.001), which could be used to improve the estimate of EF for assessing N2O emission from coastal reservoirs and other similar environments.
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Timilsina A, Oenema O, Luo J, Wang Y, Dong W, Pandey B, Bizimana F, Zhang Q, Zhang C, Yadav RKP, Li X, Liu X, Liu B, Hu C. Plants are a natural source of nitrous oxide even in field conditions as explained by 15N site preference. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 805:150262. [PMID: 34536861 DOI: 10.1016/j.scitotenv.2021.150262] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/16/2021] [Accepted: 09/06/2021] [Indexed: 05/12/2023]
Abstract
Plants are either recognized to produce nitrous oxide (N2O) or considered as a medium to transport soil-produced N2O. To date, it is not clear whether in their habitat plants conduit N2O produced in soil or are a natural source. We aimed to understand role of plants in N2O emissions in field conditions. Therefore, rubber plants (Ficus elastica) were planted in the field; then plant and soil chambers were deployed simultaneously to collect gas samples, and 15N site preference (SP) of N2O was evaluated. The mean SP values of plant and soil emitted N2O were -20.85 ± 2.8‰ and -8.85 ± 1.08‰, respectively, and were significantly different (p < 0.0001); while bulk 15N of plant and soil emitted N2O were -10.83 ± 3.33‰ and -22.56 ± 3.37‰, respectively and were similar (p = 0.06). In the current study, soil always acted as a source of N2O, while plants were both source and sink. Plant and soil N2O fluxes had significant positive exponential relationship with both soil and air temperature. Soil water-filled pore space (WFPS) had significant negative linear relationship with only soil N2O fluxes. Plant N2O fluxes had significant positive linear relationship with plant respiration rates and negative linear relationship with plant surface areas. Based on the relationship between plant respiration rates and N2O fluxes, we suggest that mitochondria are the possible sites of N2O formation in plant cells while the relationship between plant surface areas and N2O fluxes suggests that roots are the parts of its formation in natural and field conditions. Our results suggest that plants are a natural source of N2O even at field conditions and challenge a view that plants are a medium to transport soil-produced N2O into the atmosphere.
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[Acute and chronic toxicities associated with the use and misuse of nitrous oxide: An update]. Rev Med Interne 2021; 43:170-177. [PMID: 34903366 DOI: 10.1016/j.revmed.2021.10.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 09/07/2021] [Accepted: 10/09/2021] [Indexed: 11/22/2022]
Abstract
Nitrous oxide (N2O) is used since the eighteenth century as an anesthetic and analgesic but also for recreational use. If the labelled uses of N2O and their modalities are nowadays perfectly framed, the misuse of N2O takes very alarming proportions among teenagers and young adults. This misuse is the cause of acute (hypoxia, barotrauma, burns, neuropsychiatric disorders) and chronic complications if repeated (myeloneuropathy, anemia, thrombosis, inhalant use disorder). The main mechanism of the latter is mainly related to a functional deficit in vitamin B12 induced by N2O. The management of acute complications is symptomatic. The management of chronic complications is based on vitamin B12 supplementation. The best biomarker of chronic N2O exposure is the elevation of the plasmatic level of methylmalonic acid. In all cases of recreational misuses, addiction treatment is necessary to prevent complications or their worsening by providing information in order to stop consumption.
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Wan X, Laureni M, Jia M, Volcke EIP. Impact of organics, aeration and flocs on N 2O emissions during granular-based partial nitritation-anammox. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 797:149092. [PMID: 34303231 PMCID: PMC7612980 DOI: 10.1016/j.scitotenv.2021.149092] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 07/11/2021] [Accepted: 07/13/2021] [Indexed: 05/21/2023]
Abstract
Partial nitration-anammox is a resource-efficient technology for nitrogen removal from wastewater. However, the advantages of this nitrogen removal technology are challenged by the emission of N2O, a potent greenhouse gas. In this study, a granular sludge one-stage partial nitritation-anammox reactor comprising granules and flocs was run for 337 days in the presence of influent organics to investigate its effect on N removal and N2O emissions. Besides, the effect of aeration control strategies and flocs removal was investigated as well. The interpretation of the experimental results was complemented with modelling and simulation. The presence of influent organics (1 g COD g-1 N) helped to suppress NOB and significantly reduced the overall N2O emissions while having no significant effect on anammox activity. Besides, long-term monitoring of the reactor indicated that constant airflow rate control resulted in more stable effluent quality and less N2O emissions than DO control. Still, floc removal reduced N2O emissions at DO control but increased N2O emissions at constant airflow rate. Furthermore, anammox bacteria could significantly reduce N2O production during heterotrophic denitrification, likely via competition for NO with heterotrophs. Overall, this study demonstrated that the presence of influent organics together with proper aeration control strategies and floc management could significantly reduce the N2O emissions without compromising nitrogen removal efficiency during one-stage partial nitritation-anammox processes.
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Wang J, Chen Z, Xu C, Elrys AS, Shen F, Cheng Y, Chang SX. Organic amendment enhanced microbial nitrate immobilization with negligible denitrification nitrogen loss in an upland soil. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 288:117721. [PMID: 34247001 DOI: 10.1016/j.envpol.2021.117721] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 05/16/2021] [Accepted: 07/03/2021] [Indexed: 06/13/2023]
Abstract
Both soil microbial nitrate (NO3--N) immobilization and denitrification are carbon (C)-limited; however, to what extent organic C addition may increase NO3--N immobilization while stimulate denitrification nitrogen (N) loss remains unclear. Here, 15N tracing coupled with acetylene inhibition methods were used to assess the effect of adding glucose, wheat straw and peanut straw on NO3--N immobilization and denitrification under aerobic conditions in an upland soil, in which NO3--N immobilization has been previously demonstrated to be negligible. The organic C sources (5 g C kg-1 soil) were added in a factorial experiment with 100, 500, and 1000 mg N kg-1 soil (as K15NO3) in a 12-d laboratory incubation. Microbial NO3--N immobilization in the 12-d incubation in the three N treatments was 5.5, 7.7, and 8.2 mg N kg-1 d-1, respectively, in the glucose-amended soil, 5.9, 4.2, and 2.4 mg N kg-1 d-1, respectively, in the wheat straw-amended soil, and 4.9, 5.1 and 4.4 mg N kg-1 d-1, respectively, in the peanut straw-amended soil. Therefore, under sufficient NO3--N substrate, the higher microbial NO3--N immobilization in the glucose than in the crop residue treatments was likely due to the slow decomposition of the latter that provided low available C. The 15N recovery in the N2O + N2 pool over the12-day incubation was <2% for all treatments, indicating negligible denitrification N loss due to low denitrification rates in the aerobic incubation in spite of increasing C availability. We conclude that external C addition can enhance microbial NO3--N immobilization without causing large N losses through denitrification. This has significant implications for reducing soil NO3--N accumulation by enhancing microbial NO3--N immobilization through increasing C inputs using organic materials and subsequently mitigating nitrate pollution of water bodies.
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Dockx L, Caluwé M, De Vleeschauwer F, Dobbeleers T, Dries J. Impact of the substrate composition on enhanced biological phosphorus removal during formation of aerobic granular sludge. BIORESOURCE TECHNOLOGY 2021; 337:125482. [PMID: 34320762 DOI: 10.1016/j.biortech.2021.125482] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 06/25/2021] [Accepted: 06/27/2021] [Indexed: 06/13/2023]
Abstract
Performance of enhanced biological phosphorus removal (EBPR) is often investigated with simple synthetic wastewater containing volatile fatty acids (VFAs). In this study, various (fermentable) substrates, individually and in mixtures, were examined during the application of a granulation strategy. In addition, the microbial community and N2O formation were monitored. Sludge densification was observed in all systems. Stable EBPR, associated with the presence of Accumulibacter and an anaerobic P-release up to 21.9 mgPO43--P.gVSS-1, was only obtained when VFAs were present as sole substrate or in mixture. Systems fed with VFAs were strongly related to the formation of N2O (maximum of 6.25% relative to the total available nitrogen). A moderate anaerobic dissolved organic carbon (DOC) uptake was observed when amino acids (64.27 ± 3.08%) and glucose (75.39 ± 5.79%) as sole carbon source were applied. The substrate/species-specific enrichment of Burkholderiaceae and Saccharimonadaceae respectively, resulted in unstable EBPR in those systems.
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Li Z, Li L, Xia S, Zhang R, Zhang R, Chen P, Pan J, Liu Y. K fertilizer alleviates N 2O emissions by regulating the abundance of nitrifying and denitrifying microbial communities in the soil-plant system. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 291:112579. [PMID: 33957419 DOI: 10.1016/j.jenvman.2021.112579] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 03/16/2021] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
Potassium (K) fertilizer additions can result in high crop yields of good quality and low nitrogen (N) loss; however, the interaction between K and N fertilizer and its effect on N2O emissions and associated microbes remain unclear. We investigated this in a pot experiment with six fertilizer treatments involving K and two sources of N, using agricultural soil from the suburbs of Wuhan, central China. The aim was to determine the effects of the interaction between K and different forms of N on the N2O flux and the abundance of nitrifying and denitrifying microbial communities, using static chamber-gas chromatography and high-throughput sequencing methods. Compared with no fertilizer control (CK), the addition of nitrate fertilizer (NN) or ammonia fertilizer (AN) or K fertilizer significantly increased N2O emissions. However, the combined application (NNK) of K and NN significantly reduced the average N2O emissions by 28.3%, while the combined application (ANK) of K and AN increased N2O emissions by 22.7%. The abundance of nitrifying genes amoA in ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) changed in response to N and/or K fertilization, but the denitrifying genes narG, nirK and norl were strongly correlated with N2O emissions. This suggests that N or K fertilizer and their interaction affect N2O emissions mainly by altering the abundance of functional genes of denitrifying microbes in the soil-plant system. The genera Paracoccus, Rubrivivax and Geobacter as well as Streptomyces and Hyphomicrobium play an important role in N2O emissions during denitrification with the combined application of N and K.
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Ganasamurthy S, Rex D, Samad MS, Richards KG, Lanigan GJ, Grelet GA, Clough TJ, Morales SE. Competition and community succession link N transformation and greenhouse gas emissions in urine patches. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 779:146318. [PMID: 34030223 DOI: 10.1016/j.scitotenv.2021.146318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 01/28/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
Nitrous oxide (N2O) is a strong greenhouse gas produced by biotic/abiotic processes directly linked to both fungal and prokaryotic communities that produce, consume or create conditions leading to its emission. In soils exposed to nitrogen (N) in the form of urea, an ecological succession is triggered resulting in a dynamic turnover of microbial populations. However, knowledge of the mechanisms controlling this succession and the repercussions for N2O emissions remain incomplete. Here, we monitored N2O production and fungal/prokaryotic community changes (via 16S and 18S amplicon sequencing) in soil microcosms exposed to urea. Contributions of microbes to emissions were determined using biological inhibitors. Results confirmed that urea leads to shifts in microbial community assemblages by selecting for certain microbial groups (fast growers) as dictated through life history strategies. Urea reduced overall community diversity by conferring dominance to specific groups at different stages in the succession. The diversity lost under urea was recovered with inhibitor addition through the removal of groups that were actively growing under urea indicating that species replacement is mediated in part by competition. Results also identified fungi as significant contributors to N2O emissions, and demonstrate that dominant fungal populations are consistently replaced at different stages of the succession. These successions were affected by addition of inhibitors which resulted in strong decreases in N2O emissions, suggesting that fungal contributions to N2O emissions are larger than that of prokaryotes.
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Machado PVF, Farrell RE, Deen W, Voroney RP, Congreves KA, Wagner-Riddle C. Contribution of crop residue, soil, and fertilizer nitrogen to nitrous oxide emissions varies with long-term crop rotation and tillage. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 767:145107. [PMID: 33550054 DOI: 10.1016/j.scitotenv.2021.145107] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 01/05/2021] [Accepted: 01/07/2021] [Indexed: 06/12/2023]
Abstract
Agriculture is an important contributor to N2O emissions - a potent greenhouse gas - with high peaks occurring when soil mineral nitrogen (N) is high (e.g., after mineralization of organic N and N fertilizer application). Nitrogen dynamics in soil and consequently N2O emissions are affected by crop and soil management practices (e.g., crop rotation and tillage), an effect mostly assessed in the literature through comparisons of total N2O emission. Hence, information is scarce on the effect of these management practices on specific N sources affecting N2O emissions (i.e., N fertilizer, soil, above and belowground crop residues) - a knowledge gap explored in this study with the use of 15N tracers. The isotope approach enabled refinement on global N2O budget by directly determining the emission factors (EF) of above and belowground crop residues that vary in chemical composition and comparison with default EF values (e.g., IPCC EFs). Our experiment was conducted over the full-cycle of long-term crop rotations to (i) compare N2O totals and intensity, under no-tillage and conventional tillage, simple and diverse rotation; (ii) partition total N2O emissions into soil, N fertilizer, above and belowground crop residue N sources; (iii) compare the 12-month EF of crop residue against the default values proposed by IPCC (2019). For the tillage effect, annual N2O emissions were from 1.2- to 2.0-times higher on CT than NT soil due to 40% increased soil N derived N2O emission in CT. The diversified crop rotation emitted 1.3-times higher N2O than the simple rotation over the full-cycle of the rotations, but the effect was due to differences in N fertilizer rate between the rotations since emissions were equivalent when scaled by N rate. Finally, our results suggested that default IPCC EF are overestimated for crop residues under CT and NT, simple and diverse rotations as measured EFs never surpassed 0.1%.
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Han P, Wu D, Sun D, Zhao M, Wang M, Wen T, Zhang J, Hou L, Liu M, Klümper U, Zheng Y, Dong HP, Liang X, Yin G. N 2O and NO y production by the comammox bacterium Nitrospira inopinata in comparison with canonical ammonia oxidizers. WATER RESEARCH 2021; 190:116728. [PMID: 33326897 DOI: 10.1016/j.watres.2020.116728] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 06/12/2023]
Abstract
Nitrous oxide (N2O) and NOy (nitrous acid (HONO) + nitric oxide (NO) + nitrogen dioxide (NO2)) are released as byproducts or obligate intermediates during aerobic ammonia oxidation, and further influence global warming and atmospheric chemistry. The ammonia oxidation process is catalyzed by groups of globally distributed ammonia-oxidizing microorganisms, which are playing a major role in atmospheric N2O and NOy emissions. Yet, little is known about HONO and NO2 production by the recently discovered, widely distributed complete ammonia oxidizers (comammox), able to individually perform the oxidation of ammonia to nitrate via nitrite. Here, we examined the N2O and NOy production patterns by comammox bacterium Nitrospira inopinata during aerobic ammonia oxidation, in comparison to its canonical ammonia-converting counterparts, representatives of the ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). Our findings, i) show low yield NOy production by the comammox bacterium compared to AOB; ii) highlight the role of the NO reductase in the biological formation of N2O based on results from NH2OH inhibition assays and its stimulation during archaeal and bacterial ammonia oxidations; iii) postulate that the lack of hydroxylamine (NH2OH) and NO transformation enzymatic activities may lead to a buildup of NH2OH/NO which can abiotically react to N2O ; iv) collectively confirm restrained N2O and NOy emission by comammox bacteria, an unneglectable consortium of microbes in global atmospheric emission of reactive nitrogen gases.
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Chen C, Yin G, Hou L, Liu M, Jiang Y, Zheng D, Gao D, Liu C, Zheng Y, Han P. Effects of sulfamethoxazole on coupling of nitrogen removal with nitrification in Yangtze Estuary sediments. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 271:116382. [PMID: 33387786 DOI: 10.1016/j.envpol.2020.116382] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Revised: 12/07/2020] [Accepted: 12/23/2020] [Indexed: 06/12/2023]
Abstract
Coupling of nitrogen removal processes with nitrification (NRn) are vital synergistic nitrogen elimination mechanisms in aquatic environments. However, the effects of antibiotics on NRn are not well known. In the present work, 20-day continuous-flow experiments combined with 15N tracing techniques and quantitative PCR were performed to simulate the impact of sulfamethoxazole (SMX, a sulfonamide antibiotic) with near in situ concentration on NRn processes in sediments of Yangtze Estuary. Results showed that SMX with near in situ concentration significantly decreased NRn, NRw (uncoupling of nitrogen removal processes with nitrification) and actual nitrogen removal rates via inhibiting nitrogen transformation functional genes (AOB, narG, nirS, nosZ) and anammox 16S rRNA gene, while the coupling links between nitrification and nitrogen removal processes were not broken by the exposure. The proportion of NRn in total nitrogen removal processes decreased by approximately 10% with SMX addition, due to the different inhibition on AOB, denitrifying genes and anammox 16S rRNA gene. N2O production and nitrite accumulation remarkably increased with SMX addition under simultaneous nitrification and denitrification, and they strongly correlated with each other. The more severely inhibition on nirS gene (13.6-19.8%) than Nitrospira nxrB gene (0.3-8.2%) revealed that the increased nitrite accumulation with SMX addition mainly occurred in heterotrophic denitrification, suggesting that the increased N2O production was dominated by the heterotrophic nitrite reduction. Moreover, we estimated that the ratio of external inorganic N eliminated by actual nitrogen removal can upgrade to 6.4-7.4% under circumstances of no inhibition by SMX. This study revealed the effects of SMX with near in situ concentration on NRn processes and illustrated the microbial mechanism on functional genes level. Our results highlighted the inhibitory effects of SMX on NRn may contribute to reactive N retention and N2O production in estuarine and coastal ecosystems.
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Kollah B, Parmar R, Vishwakarma A, Dubey G, Patra A, Chaudhari SK, Mohanty SR. Nitrous oxide production from soybean and maize under the influence of weedicides and zero tillage conservation agriculture. JOURNAL OF HAZARDOUS MATERIALS 2021; 402:123572. [PMID: 32745878 DOI: 10.1016/j.jhazmat.2020.123572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 07/17/2020] [Accepted: 07/21/2020] [Indexed: 06/11/2023]
Abstract
Current experiment envisages evaluating N2O production from nitrification and denitrification under the influence of weedicides, cropping systems and conservation agriculture (CA). The weed control treatments were conventional hand weeding (no weedicide), pre emergence weedicide pendimethalin and post emergence weedicide imazethapyr for soybean, atrazine for maize. Experiment was laid out in randomized block design with three replicates. Soils were collected from different depths and incubated at different moisture holding capacity (MHC). N2O production from nitrification varied from 2.77 to 6.04 ng N2O g-1 soil d-1 and from denitrification varied from 0.05 to 1.34 ng N2O g-1 soil d-1. Potential nitrification rate (0.16-0.39 mM NO3 produced g-1 soil d-1) was higher than potential denitrification rate (0.45-0.93 mM NO3 reduced g-1 soil d-1). N2O production, nitrification, denitrification, and microbial gene abundance were higher in maize than soybean. Both N2O production and nitrification decreased (p < 0.05) with soil depth, while denitrification increased (p < 0.05) with soil depth. Abundance of eubacteria and ammonia oxidizing bacteria (AOB) were high (p < 0.01) at upper soil layer and declined with depth. Abundance of ammonia oxidizing archaea (AOA) increased (p < 0.05) with soil depth. Study concludes that intensive use of weedicides in CA may stimulate N2O production.
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Wu Y, Liu J, Shaaban M, Hu R. Dynamics of soil N 2O emissions and functional gene abundance in response to biochar application in the presence of earthworms. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 268:115670. [PMID: 33022546 DOI: 10.1016/j.envpol.2020.115670] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 09/08/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Nitrous oxide (N2O) is a devastating greenhouse gas and acts as an ozone-depleting agent. Earthworms are a potential source of soil N2O emissions. Application of biochar can mitigate earthworm-induced N2O emissions. However, the underlying interactive mechanism between earthworms and biochar in soil N2O emissions is still unclear. A 35-day laboratory experiment was conducted to examine the soil N2O emission dynamics for four different treatments, earthworm presence with biochar application (EC), earthworm presence without biochar application (E), earthworm absence with biochar application (C) and earthworm absence without biochar application, and the control. Results indicated a negative impact of biochar on earthworm activity, displaying a significantly (p ≤ 0.05) lower survival rate and biomass of earthworms in treatment EC than E. Compared with the control, earthworm presence significantly (p ≤ 0.05) increased cumulative N2O emissions, while application of biochar in the presence of earthworms significantly (p ≤ 0.05) decreased cumulative N2O emissions (485 and 690 μg kg-1 for treatments EC and E, respectively). Treatments E and EC significantly (p ≤ 0.05) increased soil microbial biomass carbon (MBC), ammonium (NH4+-N), nitrate (NO3-N), and dissolved organic carbon (DOC) content and soil pH as compared with the control. The gene copy number of 16 S rRNA, AOA, AOB, nirS, and nosZ increased for all treatments when compared with the control; however, a significant (p ≤ 0.05) difference among the studied genes was only observed for the nosZ gene (2.05 and 2.56 × 106 gene copies g-1 soil for treatments E and EC, respectively). Earthworm-induced soil N2O emissions were significantly (p ≤ 0.05) reduced by biochar addition. The possible underlying mechanisms may include: (1) short-term negative impacts on earthworm activity; (2) a change of functional gene abundance in earthworm casts; and (3) an increase in soil pH due to addition of biochar.
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Zhao J, Zhao J, Xie S, Lei S. The role of hydroxylamine in promoting conversion from complete nitrification to partial nitrification: NO toxicity inhibition and its characteristics. BIORESOURCE TECHNOLOGY 2021; 319:124230. [PMID: 33049441 DOI: 10.1016/j.biortech.2020.124230] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/01/2020] [Accepted: 10/04/2020] [Indexed: 06/11/2023]
Abstract
This study investigated a strategy for hydroxylamine (NH2OH) addition for promoting the conversion of complete nitrification to partial nitrification in a sequencing batch reactor (SBR). The results showed that continuous dosing of 5 mg-N/L NH2OH into a complete nitrification reactor for 16 days led to an increase in the nitrite accumulation ratio (NAR) from 0.22% to 95.08% and a significant enhancement in the accumulation of NO and N2O in the liquid. The maximum concentration of NO in each cycle rose with the increase of NAR during NH2OH addition. With the stopping of NH2OH addition, the partial nitrification disappeared progressively in 21 days. The analysis for microbial community showed that Nitrospira was the main NOB and its relative abundance decreased with NH2OH addition and recovered after the cessation of NH2OH addition. Accordingly, NH2OH has a significant and reversible inhibition on Nitrospira and its essence might be related to NO toxicity.
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