无机氮对高原沼泽甲烷氧化的影响

In a series of laboratory incubations using soils of two contrasting sites from a temperate marsh on the Qinghai-Tibet Plateau, potential methane (CH₄) oxidation rates were measured to study the effects of inorganic N inputs on CH₄ oxidation. For a drained site, subsurface peat (5-15 cm) at an initial 20 μL CH₄ L^-1 showed a significantly different (P < 0.05) CH₄ oxidation rate compared to other soil depths, with a maximal rate of 20.9 ng CH₄ gDW (dry weight)^-1 h^-1; the underlying mineral soil layers (15-30 and 30-50 cm) also had a strong CH₄ oxidation capacity at about an initial 2000 μL CH₄ L^-1. With a waterlogged site, the CH₄ oxidation rate in an aerobic incubation was significantly greater (P < 0.05) in the surface soil layer (0-5 cm) compared to the 15-30 and 30-50 cm depths. There was generally no or a very weak effect from addition of NO₃^- on CH₄ oxidation. In marked contrast, NH₄⁺ salts, such as (NH₄)₂SO₄, NH₄Cl and NH₄NO₃, exhibited strong inhibitions, which varied as a function of the added salts and the initial CH₄ level. Increasing NH₄⁺ usually resulted in greater inhibition and increasing initial CH₄ concentrations resulted in less. NH₄⁺ inhibition on CH₄ oxidation in natural high-altitude, low-latitude wetlands could be as important as has been reported for agricultural and forest soils. The NH₄⁺ effects on the CH₄ oxidation rate need to be further investigated in a wide range of natural wetland soil types.     

长期定位试验对水稻田土壤甲烷氧化活性和甲烷排放通量的影响

通过对长期定位施肥的黄松稻田土的甲烷氧化活性和甲烷排放通量的研究表明,长期定位施肥对稻田土壤的好氧甲烷氧化活性和甲烷排放通量有显著性的影响(|t|t0.05,P0.05),而对稻田土壤的厌氧甲烷氧化活性有影响但未达显著性水平(|t|t0.05,P0.05)。施加有机肥能显著增加稻田土壤的甲烷氧化活性和甲烷排放通量;当有机肥和无机肥混合施用时,其促进作用明显大于单施有机肥或无机肥。施加尿素后,稻田土壤的甲烷氧化活性及甲烷排放量都有所下降,但钾肥和磷肥能缓解由尿素引起的抑制作用。施肥后耕作的稻田甲烷氧化活性和甲烷排放通量高于施肥后不耕作的稻田;耕作而不施肥的稻田甲烷氧化活性和甲烷排放通量要低于不施肥也不耕作的稻田。     

Methane emission and entrapment in flooded rice soils as affected by soil properties

Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH₄ emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH₄ emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH₄ emission. A lower CH₄ emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH₄ emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH₄ emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH₄ emission significantly. Urea fertilization promoted CH₄ emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH₄ entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH₄ emissions to the atmosphere.     

广西反刍动物甲烷排放总量的估算

根据政府间国际经济合作组织(OECD)和政府间气候变化专业委员会(IPCC)提供的计算方法,结合中国反刍动物的能量供应特点,对自1980年以来的广西反刍动物的甲烷排放量进行了估算,结果表明:反刍动物摄入总能的6.99%~7.17%通过甲烷排放损失掉,广西反刍动物的甲烷排放总量已经从1980年排放210.0 G g上升至2004年的534.1 G g,每年上升3.97%,速度较快,占全国反刍动物甲烷排放总量的5.90%左右。对估算结果作了分析,并结合广西反刍动物生产的发展趋势提出了建议。     

上海地区水稻土氮素矿化模拟

Three types of paddy soils, derived from granite, Quaternary red clay and basalt, respectively, were selected to study the effects of Fe and Mn in paddy soils on methane production and emission through pot and incubation experiments. The results indicated that the difference of Fe and Mn in paddy soils was one of the important factors causing obvious differences in methane emission from different soil types. Soil Fe and Mn affecting methane emission from the paddy soils was likely through affecting soil Eh and forming Fe and Mn plaques on rice roots. Different rates and valences of added Fe and Mn significantly affected methane production from paddy soils. Therefore, this study enhanced understanding of processes controlling methane emission from paddy soils and may help to improve modeling and estimating regional and global methane emission from paddy soils.     

育肥猪舍甲烷排放浓度和排放通量的测试与分析

畜禽养殖是重要的温室气体排放源,畜禽养殖的甲烷排放量受动物生长特性、粪便收集方式和气候条件的影响。为了探讨中国特有的饲养管理方式下育肥猪舍温室气体排放规律,为减少甲烷排放提供依据,该研究在北京选择一典型猪场,对不同季节育肥舍的甲烷排放浓度进行了试验测定,从2004年5月至2005年3月,每2个月一次连续采集72～80 h甲烷浓度和相关数据,并根据二氧化碳平衡原理,对猪场的甲烷排放量进行了估算。结果表明：育肥猪舍内甲烷浓度有明显的季节性和日变化特性,2005年1月舍内甲烷的平均浓度为(22.98±10.52)mg/m³,7月舍内甲烷浓度为(2.68±0.68)mg/m³;每日最低甲烷浓度出现在9:00 am～17：00 pm时段;冬季舍内二氧化碳浓度明显偏高,夜间比允许浓度高1倍;每头育肥猪饲养期间的甲烷排放量为68.10～207.01 mg/h,折合每标准动物单位排放量：436～1185 mg/h·(500 kg),在IPCC推荐的发展中国家猪呼吸代谢甲烷排放1.0 kg/(a·头)范围内。     

土地利用史对水田甲烷的排放和甲烷植物的影响

The characteristics of methane emission were compared among six types of upland and paddy soils developed from different materials with distinct physical and chemical properties after planting rice.The fluxes of methane emission in submerged soils from the upland were obviously lower than those from the paddy rice field.The flux of methane emission in the paddy soil developed from fluvo-aquic soil was the largest among all the types of soils.Planting of rice was heplful to emission of methane in soils.The amounts of various groups of methanogenic flora were conformed with the differences among the fluxes of methane emission in various types of soils.Methane formation was observed in each type of air-dried soils stored for a long time after addition of water and incubation at 35℃.     

Oxidation of methane in the rhizosphere of rice plants

Oxidation of CH₄ in the rhizosphere of rice plants was quantified using (1) methyl fluoride, a specific inhibitor of CH₄ oxidation, and (2) measuring changes in plant-mediated CH₄ emission after incubation under air, N₂, or 40% O₂. No significant rhizospheric CH₄ oxidation was observed from rice plants in the ripening stage. CH₄ emission from rice plants 1 week before panicle initiation increased by 40% if CH₄ oxidation in the rhizosphere was blocked. The growth stage of the rice plant is an important factor determining the rhizospheric CH₄ oxidation. Fluctuation of rhizospheric CH₄ oxidation during the growing season may help to explain the observed seasonal CH₄ emission patterns in field studies. Measurements from four rice varieties showed that one variety, Pokkali, had higher rhizospheric CH₄ oxidation. This was probably because Pokkali was in an earlier growth stage than the other three varieties. Both in the early and in the late growth stages, incubation under N₂ caused a much stronger CH₄ flux than inhibition of CH₄ oxidation alone. Apparently, N₂ incubation not only blocked CH₄ oxidation but also stimulated methanogenesis in the rhizosphere. Incubation under a higher O₂ atmosphere (40% O₂) than ambient air decreased the CH₄ flux, suggesting that increasing the oxidation of the rice rhizosphere may help in reducing CH₄ fluxes from rice agriculture. The O₂ pressure in the rhizosphere is an important factor that reduces the plant-mediated CH₄ flux. However, inhibition of methanogenesis in the rhizosphere may contribute more to CH₄ flux reduction than rhizospheric CH₄ oxidation.     

Factors affecting seasonal variation of methane concentration in water in a freshwater marsh vegetated with Carex lasiocarpa

To understand the underlying factors affecting the seasonal variation of the methane concentration in a cool temperate freshwater marsh vegetated with Carex lasiocarpa in the Sanjiang Plain of northeast China, we measured methane emission from, and the concentrations of methane, dissolved organic carbon (DOC) and acetate in, water samples taken from the standing water surface to the top of the gley soil layer in the C. laisocarpa marsh, before and after plants were covered with a black cloth at the three growing stages of June, July and August 2002. The methane oxidation rate was also measured in situ by applying acetylene, a methane oxidation inhibitor, to whole plants, and the methane production rate in water sampled in June and July was measured via the anaerobic incubation in the laboratory. The methane production rate in water samples was significantly correlated with acetate concentration rather than DOC concentration, whereas the mean acetate concentration in water samples was higher in June than in July and August. Hence, the low methane concentration in June did not result from a lack of acetate for methane production. The mean methane and DOC concentrations in water samples were enhanced by 22.3 and 31.1% in June, 2.1 and 5.0% in July, and 3.4 and 15.2% in August, respectively, after plants were covered with a black cloth. The methane oxidation rate and redox potential in the freshwater marsh decreased from June to July or August. These results suggest that there was more oxygen in the rhizome and rhizosphere in June than in July and August, which not only accentuated methane oxidation but also reduced methane production. Therefore, the high methane concentration in water in July and August could be ascribed to both an increase in temperature and a decrease in redox potential or oxygen concentration in the rhizosphere.     

肥料类型及浓度对水肥一体化浑水滴灌滴头输沙能力的影响

为研究浑水水肥一体化灌溉过程中,不同肥料对滴头输沙能力的影响,合理配置滴灌系统首部的过滤设备和设施,降低过滤设施的成本,提高滴灌系统工作效率,选取了常用的3种肥料(尿素、硫酸钾和水溶性复合肥)及其3种肥料质量分数(1%、2%和3%),在含沙量为1 g/L的浑水条件下进行间歇灌水堵塞试验,分析了滴头累积泥沙输出量、出流含沙量和泥沙输出率。结果表明:浑水施肥可以增强滴头的输沙能力,肥料类型和浓度不同,对滴头输沙能力的影响也不同。滴头输沙能力随着尿素浓度的增大而增大,当尿素质量分数为3%时,滴头输沙能力比未施肥处理增加了11%(P0.05)。滴头输沙能力随硫酸钾和复合肥浓度的增大而减小,当硫酸钾质量分数为1%时,滴头输沙能力大于未施肥处理,增大了25%;当复合肥质量分数2%时,滴头输沙能力小于未施肥处理。标准化的累积泥沙输出量与标准化的累积灌水量的拟合直线斜率也可作为滴头输沙能力的判断依据,肥料质量浓度是影响滴头输沙能力的重要因素,应根据不同的肥料类型,确定适宜的施肥浓度。研究结果对确定滴头防堵塞策略提供一定的参考。     

水分状态、土壤类型和氮素种类对氧化亚氮和甲烷排放的影响

Specific management of water regimes, soil and N in China might play an important role in regulating N2O and CH4 emissions in rice fields. Nitrous oxide and methane emissions from alternate non-flooded/flooded paddies were monitored simultaneously during a 516-day incubation with lysimeter experiments. Two N sources （^15N-（NH4）2SO4 and ^15N-labeled milk vetch） were applied to two contrasting paddies： one derived from Xiashu loess （Loess） and one from Quaternary red clay （Clay）. Both N2O and CH4 emissions were significantly higher in soil Clay than in soil Loess during the flooded period. For both soil, N2O emissions peaked at the transition periods shortly after the beginning of the flooded and non-flooded seasons. Soil type affected N2O emission patterns. In soil Clay, the emission peak during the transition period from non-flooded to flooded conditions was much higher than the peak during the transition period from flooded to non-flooded conditions. In soil Loess, the emission peak during the transition period from flooded to non-flooded conditions was obviously higher than the peak during the transition period from non-flooded to flooded conditions except for milk vetch treatment. Soil type also had a significant effect on CH4 emissions during the flooded season, over which the weighted average flux was 111 mg C m^-2 h^-1 and 2.2 mg C m^-2 h^-1 from Clay and Loess, respectively. Results indicated that it was the transition in the water regime that dominated N2O emissions while it was the soil type that dominated CH4 emissions during the flooded season. Anaerobic oxidation of methane possibly existed in soil Loess during the flooded season.     

胶体作用下饱和土壤中Cd运移的数值模拟

通过室内土柱出流实验探讨了饱和壤砂土中Cd在SiO2胶体作用下的运移行为,并用对流-弥散方程(Convection-Dispersion Equation,CDE)对实验结果进行了数值模拟。结果表明,土壤中SiO2胶体的存在抑制了Cd的运移,土壤对Cd的吸附以动力学反应为主。耦合Freundlich等温吸附的单点非平衡模型(One Site Nonequilibrium Model,OSM)能较好地模拟Cd在壤砂土中的运移,模拟得到的吸附特性参数β较小,表明壤砂土吸附表面的不均一性较强。SiO2胶体的穿透时间较早,耦合沉淀-释放反应的CDE模型可以很好地描述SiO2胶体在壤砂土中的运移。胶体作用下的CDE模型成功地模拟了SiO2胶体存在时Cd的运移;同时,参数敏感性分析结果表明,胶体对Cd的吸附速率系数kamc、kaic越小,解吸速率系数kdmc、kdic越大,越有利于Cd的运移。     

National-scale estimation of methane emission from paddy fields in Japan: Database construction and upscaling using a process-based biogeochemistry model

We have estimated methane (CH₄) emission from total rice (Oryza sativa L.) paddies in Japan by means of a process-based biogeochemistry model, DeNitrification-DeComposition(DNDC)-Rice, combined with a geographic information system (GIS) database of climate, soil and farming practices. In the GIS database, 2 million ha of rice paddies were divided into 17,408 units according to 136 climate areas, 16 soil types, four classes of drainage rate and two classes of groundwater level, to simulate CH₄ flux from each of the units applying the DNDC-Rice model. As a result, the national-scale CH₄ emission in 1990 was estimated to be 216 Gg carbon (C), 13% lower than a previous inventory estimated by the Tier 2 method. By our Tier 3 approach, a relatively higher CH₄ flux was estimated from eastern regions than from western regions of Japan, presumably due to the differences in climate and water management. Sensitivity analysis and uncertainty assessment indicated that it is important to account for the heterogeneity in soil properties such as field water capacity, iron (Fe) concentration and drainage rate, in order to reduce the uncertainty in regional estimates.     

中国自然湿地甲烷排放: 1995-2004年研究总结

From studies undertaken during 1995-2004, annual budgets of CH₄ emissions from natural wetlands and its temporal and spatial variations were examined throughout China, and various factors influencing CH₄ emissions were also evaluated. The seasonal variation in CH₄ emissions that increased with increasing plant growth reached its peak in August;decrease in the emissions was found in freshwater marshes but not in peatlands. Emissions were mainly controlled by temperature and depth of standing water. Low CH₄ emissions at the early plant growing stages were not because of deficiency of organic C for CH₄ production but because of low temperatures. Low temperatures not only reduced CH₄ production but also stimulated CH₄ oxidation by lowering the activity of other aerobic microbes which left more O₂ in the rhizosphere for methanotrophs. Low summer temperatures (below 20 ℃) in the Qinghai-Tibetan Plateau lowered CH₄ production and CH₄ emission resulting in little or no seasonal variation of emissions. Diel and spatial variation in CH₄ emissions depended on plant species. For plants that transport CH₄ using the pressure-driven convective through-flow mechanism, diel variation in CH₄ emissions was governed by diel variation of solar energy load (that produces temperature and vapor pressure differences within various plant tissues) and stomatal conductance. For plants that transport gases using the molecular diffusion mechanism only, the diel variation of CH₄ emissions was because of differences in the magnitude of O₂ produced through photosynthesis and then delivered into the rhizomes and/or rhizosphere for CH₄ oxidation. Emergent plants could transport more CH₄ than submerged plants because the former transport CH₄ directly into the atmosphere rather than into water as do submerged plants where CH₄ can be further be oxidized during its diffusion from water to the atmosphere. Emergent plants with high gas transport capacity could not only transport more CH₄ into the atmosphere but also live in deeper water, which in turn would inundate more plant litter, resulting in increased availability of C for CH₄ production. Annual CH₄ emission from natural wetlands in China was estimated to be 1.76 Tg, up to 1.17 Tg of which was emitted from freshwater marshes. CH₄ emission from freshwater marshes mainly occurred during the growing season and less than 8% was released during the freeze-thawing period despite the fact that thawing efficiently released CH₄ fixed in ice column into the atmosphere.     

Effect of seedling transplanting date on methane emission from rice paddy soil during cultivation

In most temperate mono-rice cultivation systems like Korea, the local recommended transplanting date of rice (Oryza sativa L.) seedlings is proposed by the government agency considering climate, rice cultivar, rice productivity and quality, etc. Recently the transplanting of rice seedlings earlier than the recommended transplanting date (RTD) has been adopted by the local farmers to get high yield and to harvest earlier for higher market value. Earlier transplanting than RTD might influence methane (CH₄) emission due to the prolonged cultivation period, but its effect was not evaluated well so far. In this study, the effects of seedling transplanting date on CH₄ emission and rice productivity were investigated for two years in a general paddy soil. The 30-day old seedlings were transplanted on the local RTD (every June 15) as the control, and at 30 and 15 days before and 15 days after the RTD for comparison. There was no difference on CH₄ flux pattern among the treatments, but the earlier transplanting before the RTD significantly (P ?≤?0.05) increased total CH₄ emissions during rice cultivation due to the extended soil flooding period and improved plant growth. Rice grain yield was increased by earlier transplanting, but the values were not significantly different from those of transplanting practices on RTD and 15 days before RTD. Therefore, among all the treatments, the lowest total CH₄ emission per grain yield was observed in the RTD treatment. Conclusively, rice transplanting following the RTD, rather than early or late transplanting, could be more effective to minimize CH₄ emission without significantly decreasing the rice productivity.     

Effect of rice variety on methane emission from an Indonesian paddy field

Variations in CH₄ emission from a Sumatra paddy field in which 8 popular modern varieties in Indonesia were grown were compared in the 1994/1995 rainy season. Total amounts of CH₄ emitted during the period of rice growth were in the ranges of 32.6-41.7 and 51.3–64.6 g CH₄ m^-2 for the plots amended with chemical fertilizer only and those amended with both rice straw and chemical fertilizer, respectively. The mean CH₄ emission rate was highest in the plot with the variety Bengawan solo and lowest in the plots with the varieties Atomita-4 and Way seputih among the plots which received chemical fertilizer, while highest in the plot with Way seputih and lowest in the plot with Bengawan solo among the plots amended with both rice straw and chemical fertilizer. The increase in the mean CH₄ emission rates by rice straw application was higher for the plots planted with Way seputih (1.98 times) and Atomita-4 (1.77 times) than for the plots with Bengawan solo (1.23 times) and IR-64 (1.35 times). The plots with Walanai and Cisanggarung recorded intermediate mean emission rates and the increase in CH₄ emission by rice straw application was also intermediate (1.57–1.64 times). It was noteworthy that Way seputih and Atomita-4 were derived from the variety Cisadane, Bengawan solo and IR-64 from the variety IR-54, and Walanai and Cisanggarung from the varieties IR-36 and Pelita 1-1, respectively.

The amounts of CH. emitted for 1 kg grain production ranged from 53 (Atomita-4) to 74 (Kapuas and Walanai) and from 89-93 (IR-64, Bengawan solo, and Atomita-4) to 121 (Kapuas) g CH₄ kg^-1 of grain for the plots amended with chemical fertilizer and those amended with rice straw and chemical fertilizer, respectively.     

夏季猪场污水贮存过程中CO2、CH4排放试验

猪场粪污是重要的温室气体排放源,针对中国缺乏猪场污水贮存过程中温室气体排放参数的问题,该文选择温度较高的夏季,利用动态箱法于2007年6月对猪场的三格式化粪池进行了CO<2、CH₄气体排放测试。测试结果表明：当大气平均温度为28.4℃时,86%的温室气体排放源于一级和二级化粪池,一级、二级和三级化粪池的温室气体排放通量分别为407.5、383.0、127.7 g/(m2?h)二氧化碳当量;CH₄是本污水贮存单元中产生的主要的温室气体,一、二、三级化粪池排放的温室气体总量中,CH₄排放的贡献率分别为95%、96%、95%,控制一、二级化粪池甲烷排放将大幅度减少猪场污水温室气体排放     

Methane uptake and nitrous oxide emission in Japanese forest soils and their relationship to soil and vegetation types

Abstract

To determine the means and variations in CH₄ uptake and N₂O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed-chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH₄ uptake rates were observed at most sites. N₂O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH₄ uptake and N₂O emission (all sites combined) were 66 (2.9–175) µg CH₄-C m^?2 h^?1 and 1.88 (0.17–12.5) µg N₂O-N m^?2 h^?1, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH₄ uptake were found among soil types (P < 0.05). The mean CH₄ uptake rates (µg CH₄-C m^?2 h^?1) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N₂O emission rates differed significantly among vegetation types (P < 0.05). The mean N₂O emission rates (µg N₂O-N m^?2 h^?1) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH₄ uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11–43 µg CH₄-C m^?2 h^?1), and the N₂O emission rates in Japan were lower than those reported for temperate forests (0.23–252 µg N₂O-N m^?2 h^?1). Using land area data of vegetation cover and soil distribution, the amount of annual CH₄ uptake and N₂O emission in the Japanese forest land was estimated to be 124 Gg CH₄-C year^?1 with 39% uncertainty and 3.3 Gg N₂O-N year^?1 with 76% uncertainty, respectively.