摘要 :
Awareness of global warming has stimulated research on environmental controls of soil methane (CH) consumption and the effects of increasing atmospheric carbon dioxide (CO) on the terrestrial CH sink. In this study, factors impact...
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Awareness of global warming has stimulated research on environmental controls of soil methane (CH) consumption and the effects of increasing atmospheric carbon dioxide (CO) on the terrestrial CH sink. In this study, factors impacting soil CH consumption were investigated using laboratory incubations of soils collected at the Free Air Carbon Transfer and Storage I site in the Duke Forest, NC, where plots have been exposed to ambient (370 oL L-p#) or elevated (ambient + 200 oL L-p#) CO since August 1996. Over 1 year, nearly 90% of the 360 incubations showed net CH consumption, confirming that CH-oxidizing (methanotrophic) bacteria were active. Soil moisture was significantly (p < 0.01) higher in the 25-30 cm layer of elevated CO soils over the length of the study, but soil moisture was equal between CO treatments in shallower soils. The increased soil moisture corresponded to decreased net CH oxidation, as elevated CO soils also oxidized 70% less CH at the 25-30 cm depth compared to ambient CO soils, while CH consumption was equal between treatments in shallower soils. Soil moisture content predicted (p < 0.05) CH consumption in upper layers of ambient CO soils, but this relationship was not significant in elevated CO soils at any depth, suggesting that environmental factors in addition to moisture were influencing net CH oxidation under elevated CO. More than 6% of the activity assays showed net CH production, and of these, 80% contained soils from elevated CO plots. In addition, more than 50% of the CH-producing flasks from elevated CO sites contained deeper (25-30 cm) soils. These results indicate that subsurface (25 cm+) CH production contributes to decreased net CH consumption under elevated CO in otherwise aerobic soils.
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摘要 :
Selecting for lower methane (CH_4) emitting animals
is one of the best approaches to reduce CH_4 given that
genetic progress is permanent and cumulative over generations.
As genetic selection requires a large number of
animals...
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Selecting for lower methane (CH_4) emitting animals
is one of the best approaches to reduce CH_4 given that
genetic progress is permanent and cumulative over generations.
As genetic selection requires a large number of
animals with records and few countries actively record
CH_4, combining data from different countries could
help to expedite accurate genetic parameters for CH_4
traits and build a future genomic reference population.
Additionally, if we want to include CH_4 in the breeding
goal, it is important to know the genetic correlations
of CH_4 traits with other economically important traits.
Therefore, the aim of this study was first to estimate
genetic parameters of 7 suggested methane traits, as
well as genetic correlations between methane traits and
production, maintenance, and efficiency traits using a
multicountry database. The second aim was to estimate
genetic correlations within parities and stages of
lactation for CH_4. The third aim was to evaluate the
expected response of economically important traits by
including CH_4 traits in the breeding goal. A total of
15,320 methane production (MeP, g/d) records from
2,990 cows belonging to 4 countries (Canada, Australia,
Switzerland, and Denmark) were analyzed. Records on
dry matter intake (DMI), body weight (BW), body
condition score, and milk yield (MY) were also available.
Additional traits such as methane yield (MeY;
g/kg DMI), methane intensity (MeI; g/kg energy-corrected
milk), a genetic standardized methane production,
and 3 definitions of residual methane production
(g/d), residual feed intake, metabolic BW (MBW),
BW change, and energy-corrected milk were calculated.
The estimated heritability of MeP was 0.21, whereas
heritability estimates for MeY and MeI were 0.30 and
0.38, and for the residual methane traits heritability
ranged from 0.13 to 0.16. Genetic correlations between
different methane traits were moderate to high (0.41
to 0.97). Genetic correlations between MeP and economically
important traits ranged from 0.29 (MY) to
0.65 (BW and MBW), being 0.41 for DMI. Selection
index calculations showed that residual methane had
the most potential for inclusion in the breeding goal
when compared with MeP, MeY, and MeI, as residual
methane allows for selection of low methane emitting
animals without compromising other economically important
traits. Inclusion of residual feed intake in the
breeding goal could further reduce methane, as the correlation
with residual methane is moderate and elicits
a favorable correlated response. Adding a negative economic
value for methane could facilitate a substantial
reduction in methane emissions while maintaining an
increase in milk production.
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摘要 :
Dairy cows contribute to greenhouse gas emissions from livestock, and reducing methane emissions is vital for the long-term sustainability of the dairy industry. Genetics and breeding strategies can be used to bring about permanen...
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Dairy cows contribute to greenhouse gas emissions from livestock, and reducing methane emissions is vital for the long-term sustainability of the dairy industry. Genetics and breeding strategies can be used to bring about permanent and long-term enteric methane emission reduction from dairy cattle. Here, we assess three definitions for methane emission traits, investigate their genetic parameters, and compare potential implications of including them in a genetic selection program. All three commonly used methane traits (daily methane production, methane yield, and methane intensity) were heritable, and are potential candidates for a selection program. Additionally, all traits were highly correlated with each other, indicating that selection on one trait would lead to an indirect response on the other methane traits. By exploring trait definitions for including methane in selection strategies, this work contributes to potential mitigation strategies for reducing greenhouse gas emissions in dairy cattle using genetics.
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В донных осадках озера Байкал проведена количественная оценка деятельности меганоген-ных и мётаногрофных бактерий. Содержан...
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В донных осадках озера Байкал проведена количественная оценка деятельности меганоген-ных и мётаногрофных бактерий. Содержание метана вдонных отложениях озера варьирует от 0.0053 до 81.7 ид/дм~3. Скорость бактериального образования метана составляет 0.0004-534.7 мкл СН_4/(дм~3 сут), окисления -0.005-1180 мкл СНд/ (дм~3 сут). Максимальная скорость этих процессов измерена в осадках вблизи метанового вента в бухте Фроглиха. За суткис 1 м~2 осадков в водную толщу поступает 492-4340 мкл CH_4. В придонных слоях воды скорость бактериального окисления метана равна 0.002-1.78 мкл/(я суг).Установлено, чтометаногены и метанотрофы играют важную роль в круговороте углерода по всей толще изученных осадков озера и особенно в районах метановых вент и газогидратов.
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Soil is a non-renewable environment in which, depending on the prevailing O-2 conditions, two opposite processes - methanogenesis and methanotrophy - may take place. The rates of the processes may result in soil acting as a sink o...
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Soil is a non-renewable environment in which, depending on the prevailing O-2 conditions, two opposite processes - methanogenesis and methanotrophy - may take place. The rates of the processes may result in soil acting as a sink or a source of methane (CH4). Due to agricultural practices, heavy metals may accumulate affecting soil microbial processes. We tested the effect of cadmium (Cd) contamination on CH4 emission and uptake in three mineral soils (Eutric Cambisol, Haplic Podzol, Mollic Gleysol). Additionally, in the methanotrophy study, different soil moisture levels (pF 0; 2.2; 3.2) were studied. Based on the European annual and maximum limits, soils were polluted with cadmium in four doses (per dry soil mass): 0.048 mg Cd kg(-1) (and its five-fold higher value) and 3.00 mg Cd kg(-1) (and its five-fold higher value). The results showed that all tested soils produced and consumed CH4. Methane production rates were not significantly changed by the presence of the cadmium (except annual five-fold Cd dose in Podzol). In methanotrophy study, soil moisture was stronger regulator of CH4 oxidation (p < 0.05) than Cd pollution which effect depended on the soil type, Cd dose and pF level. CH4 was completely consumed in Cambisol (only at pF 0 with the rate significantly different from the rates at pF 2.2 and 3.2) and in Gleysol (at pF 0; pF 2.2; the CH4 oxidation rates were significantly different among all tested moistures with annual Cd dose), but this process was delayed after the application of the higher Cd doses. Among the tested soils, only the Podzol oxidized the added CH4 under all tested moisture levels (with the rate significantly different at pF 2.2 wit annual Cd dose), while Cd addition delayed CH4 uptake as well. In the Podzol, CH4 consumption was inhibited only by the highest Cd dose at low moisture (pF 3.2).
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Methane (CH4) is a product of enteric fermentation in ruminants, and it represents around 17% of global CH4 emissions. There has been substantial effort from the livestock scientific community toward tools that can help reduce thi...
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Methane (CH4) is a product of enteric fermentation in ruminants, and it represents around 17% of global CH4 emissions. There has been substantial effort from the livestock scientific community toward tools that can help reduce this percentage. One approach is to select for lower emitting animals. To achieve this, accurate genetic parameters and identification of the genomic basis of CH4 traits are required. Therefore, the objectives of this study were 1) to perform a genomewide association study to identify SNP associated with several CH4 traits in Angus beef cattle (1,020 animals) and validate them in a lactating Holstein population (population 1 [POP1]; 205 animals); 2) to validate significant SNP for DMI and weight at test (WT) from a second Holstein population, from a previous study (population 2 [POP2]; 903 animals), in an Angus population; and 3) to evaluate 2 different residual CH4 traits and determine if the genes associated with CH4 also control residual CH4 traits. Phenotypes calculated for the genotyped Angus population included CH4 production (MeP), CH4 yield (MeY), CH4 intensity (MI), DMI, and WT. The Holstein population (POP1) was multiparous, with phenotypes on CH4 traits (MeP, MeY, and MI) plus genotypes. Additionally, 2 CH4 traits, residual genetic CH4 (RGM) and residual phenotypic CH4 (RPM), were calculated by adjusting MeP for DMI and WT. Estimated heritabilities in the Angus population were 0.30, 0.19, and 0.15 for MeP, RGM, and RPM, respectively, and genetic correlations of MeP with DMI and WT were 0.83 and 0.80, respectively. Estimated heritabilities in Holstein POP1 were 0.23, 0.30, and 0.42 for MeP, MeY, and MI, respectively. Strong associations with MeP were found on chromosomes 4, 12, 14, 20, and 30 at P < 0.001, and those chromosomes also had significant SNP for DMI in Holstein POP1. In the Angus population, the number of significant SNP for MeP at P < 0.005 was 3,304, and approximately 630 of those SNP also were important for DMI and WT. When a set (approximately 3,300) of significant SNP for DMI and WT in the Angus population was used to estimate genetic parameters for MeP and MeY in Holstein POP1, the genetic variance and, consequently, the heritability slightly increased, meaning that most of the genetic variation is largely captured by these SNP. Residual traits could be a good option to include in the breeding goal, as this would facilitate selection for lower emitting animals without compromising DMI and WT.
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To clarify how hydrological processes affect biogenic methane (CH4) production andemission from soil surfaces, we analyzed the 613C of CH4 and CO2 and chemicalconstituents dissolved in groundwater at a wetland in the headwater cat...
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To clarify how hydrological processes affect biogenic methane (CH4) production andemission from soil surfaces, we analyzed the 613C of CH4 and CO2 and chemicalconstituents dissolved in groundwater at a wetland in the headwater catchment of atemperate forest in Japan. We estimated the contribution of acetate fermentation using the613C isotope mass balance of dissolved CH4 and CO2. CH4 production pathways (e.g.,acetate fermentation and carbonate reduction) changed temporally and spatially withhydrologically controlled redox conditions. The proportion of methanogenesis attributableto acetate fermentation usually decreased with temperature, suggesting that carbonatereduction dominated under conditions of high CO2 concentration. In particular, thegroundwater table and summer temperatures were key controlling factors in theinterannual and intra-annual changes in CH4 production pathways, controlling oxygensupply and consumption and, therefore, redox conditions in the soil. Under hightemperature and high water table conditions during summer, the soil was strongly reducedand the proportion of carbonate reduction increased. Acetate fermentation alsoincreased episodically, resulting in sporadic increases in 613C-CH4. The calculated acetatecontribution obviously decreased in periods of low water table and high temperaturewhen the soil surface was relatively oxic, implying deactivation of acetoclasticmethanogenesis under oxic conditions. Thus, hydrological processes control the supply ofthese electron donors and acceptors and therefore play an important role in determiningthe relative proportions of CH4-producing pathways. Our results also indicate that anincrease in acetate contribution under highly reducing conditions stimulates CH4production and emission from the soil surface.
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Coincidences between neutral particles and photoions have been measured at the C 1s edge of the CH_4 molecule. These neutral particles are either vacuum ultraviolet (VUV) photons or metastable fragments and their contributions can...
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Coincidences between neutral particles and photoions have been measured at the C 1s edge of the CH_4 molecule. These neutral particles are either vacuum ultraviolet (VUV) photons or metastable fragments and their contributions can be separated temporally. Observed VUV-photon-photoion coincidences were mostly triggered by Lyman emission in excited H atoms. Two metastable fragment-photoion channels were observed and assigned to H ~*-H~+ and H~*-CH_n ~+ (n=0-3) coincidences, where H~* signifies a metastable H atom. The coincidence yields as a function of photon energy revealed all the core excitations, but were particularly enhanced just above the C 1s ionization threshold and also displayed the vibrational structure related to the core-ionized C 1s-1 state. The metastable H atoms observed in the present study were produced in highly excited Rydberg states and could be partly field ionized. The approximate kinetic energy distributions of the metastable H~* atoms have been derived from the H ~*-H~+ coincidence measurements performed at the C 1s→3p and 3d resonances as well as just above the C 1s threshold.
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Landfills are frequently considered for urban development, but have limited end uses due to large differential settlements, leachate generation, and gas emissions. Current landfill design with top- and bottom-liner systems minimiz...
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Landfills are frequently considered for urban development, but have limited end uses due to large differential settlements, leachate generation, and gas emissions. Current landfill design with top- and bottom-liner systems minimize entry of moisture and increase the period required for stabilization of the refuse to occur. The objective of this study is to test the ability of biological enhancement to reduce the time to reach biological stabilization of the waste to nondegradable matter, and to determine the effects of biodegradation on settlement. To accomplish this, six landfill test cells were constructed to model both settlement and decomposition over extended periods. Three cells were designed to simulate bioreactor landfills, while another three were designed to simulate secure vaults. Results demonstrate that secondary settlement is linear with the logarithm of time, and decomposition is well represented by a first-order model. Comparisons indicate that in the short term there is no significant increase in the settlement rate due to biodegradation; however, extrapolation suggests that in the long term the settlement rate will likely increase as the effects of decomposition become more significant. [References: 39]
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In lakes, the production and emission of methane (CH_4) have been linked to lake trophic status. However, few studies have quantified the temporal response of lake CH_4 dynamics to primary productivity at the ecosystem scale or co...
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In lakes, the production and emission of methane (CH_4) have been linked to lake trophic status. However, few studies have quantified the temporal response of lake CH_4 dynamics to primary productivity at the ecosystem scale or considered how the response may vary across lakes. Here, we investigate relationships between lake CH_4 dynamics and ecosystem primary productivity across both space and time using data from five lakes in northern Wisconsin, USA. From 2014 to 2019, we estimated hypolimnetic CH_4 storage rates for each lake using timeseries of hypolimnetic CH_4 concentration through the summer season. Across all lakes and years, hypolimnetic CH_4 storage ranged from <0.001 to 7.6 mmol CH_4 m~(-2) d~(-1) and was positively related to the mean summer rate of gross primary productivity (GPP). However, within-lake temporal responses to GPP diverged from the spatial relationship, and GPP was not a significant predictor of interannual variability in CH_4 storage at the lake scale. Using these data, we consider how and why temporal responses may differ from spatial patterns and demonstrate how extrapolating cross-lake relationships for prediction at the lake scale may substantially overestimate the rate of change of CH_4 dynamics in response to lake primary productivity. We conclude that future predictions of lake-mediated climate feedbacks in response to a shifting distribution of trophic status should incorporate both varying lake responses and the temporal scale of change.
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