共查询到20条相似文献，搜索用时 15 毫秒
1.
Wong CS 《Science (New York, N.Y.)》1978,200(4338):197-200
The atmospheric input of carbon dioxide from burning wood, in particular from forest fires in boreal and temperate regions resulting from both natural and man-made causes and predominantly from forest fires in tropical regions caused by shifting cultivation, is estimated to be 5.7 x 10(15) grams of carbon per year as gross input and 1.5 x 10(15) grams of carbon per year as net input. This is a significant amount as compared to the fossil fuel carbon dioxide produced from the utilization of oil, gas, coal, and limestone, and bears on the hypothesis of the enhanced sedimentation of marine detritus as a removal mechanism of excess atmospheric carbon dioxide. 相似文献
2.
火烧迹地朽木的热重分析 总被引：1，自引：0，他引：1
森林火烧往往造成大量林木死亡。火烧迹地上不同死亡木腐朽程度差别较大。为比较分析朽木和正常生长木的热解差异,对昆明市安宁2006年"3·29"森林火灾火烧迹地上12种主要受害树种的朽木及其正常生长木进行了热重实验,分析和计算了24种样品的活化能、着火温度、燃烬温度和综合燃烧特性指数。研究表明,朽木热稳定性优于同种正常生长木,燃烧性较同种正常生长木差。 相似文献
3.
山白兰人工林生态系统碳储量及空间分布特征 总被引：1，自引：0，他引：1
[目的]揭示山白兰人工林碳储量的空间分布特征及规律,为森林生态系统碳储量估算提供基础数据,也为进行人工林碳汇造林项目提供科学参考。[方法]以南亚热带地区27年生山白兰人工林为研究对象,采用标准木法、样方收获等方法对其生物量、碳含量分配进行研究。[结果]山白兰人工林生态系统碳储量为158.21 t/hm2,其中乔木层占植被层碳储量的87.24%,灌木层占10.77%,草本层占0.18%,凋落物层占1.81%;土壤层中0～80 cm的碳储量为102.01 t/hm2,为植被层的1.82倍。山白兰人工林乔木层年净固碳量为3.50 t/（hm2.年）。[结论]山白兰人工林生态系统碳储量比较可观,具有较好的发展前景。 相似文献
4.
The ocean: a natural source of carbon monoxide 总被引：4，自引：0，他引：4
The surface waters of the western Atlantic are supersaturated with respect to the partial pressure of carbon monoxide in the atmosphere. Under these conditions, the net transport of carbon monoxide across the air-sea interface must be from the sea into the atmosphere. Thus, the ocean appears to act as a source of carbon monoxide. The ocean may be the largest known natural source of this gas, contributing possibly as much as 5 percent of the amount generated by burning of fuels by man. 相似文献
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Oil shales and carbon dioxide 总被引：1，自引：0，他引：1
During retorting of oil shales in the western United States, carbonate minerals are calcined, releasing significant amounts of carbon dioxide. Residual organic matter in the shales may also be burned, adding more carbon dioxide to the atmosphere. The amount of carbon dioxide produced depends on the retort process and the grade and mineralogy of the shale. Preliminary calculations suggest that retorting of oil shales from the Green River Formation and burning of the product oil could release one and one-half to five times more carbon dioxide than burning of conventional oil to obtain the same amount of usable energy. The largest carbon dioxide releases are associated with retorting processes that operate at temperatures greater than about 600 degrees C. 相似文献
7.
《农业科学学报》2016,(1)
We have had little understanding on the effects of different types and quantities of biochar amendment on soil N transformation process and the microbial properties. In this study, various biochars were produced from straw residues and wood chips, and then added separately to a paddy soil at rates of 0.5, 1 and 2%(w/w). The effects of biochar application on soil net N mineralization and nitrification processes, chemical and microbial properties were examined in the laboratory experiment. After 135 d of incubation, addition of straw biochars increased soil p H to larger extent than wood biochars. The biochar-amended soils had 37.7, 7.3 and 227.6% more soil organic carbon(SOC), available P and K contents, respectively, than the control soil. The rates of net N mineralization and nitrification increased significantly as biochars quantity rose, and straw biochars had greater effect on N transformation rate than wood biochars. Soil microbial biomass carbon increased by 14.8, 45.5 and 62.5% relative to the control when 0.5, 1 and 2% biochars(both straw- and wood-derived biochars), respectively, were added. Moreover, biochars amendments significantly enhanced the concentrations of phospholipid fatty acids(PLFAs), as the general bacteria abundance increased by 161.0% on average. Multivariate analysis suggested that the three rice straw biochar(RB) application levels induced different changes in soil microbial community structure, but there was no significant difference between RB and masson pine biochar(MB) until the application rate reached 2%. Our results showed that biochars amendment can increase soil nutrient content, affect the N transformation process, and alter soil microbial properties, all of which are biochar type and quantity dependent. Therefore, addition of biochars to soil may be an appropriate way to disposal waste and improve soil quality, while the biochar type and addition rate should be taken into consideration before its large-scale application in agro-ecosystem. 相似文献
8.
在全球气候变化背景下,森林碳汇能力成为国际减缓气候变暖的重要措施之一。随着碳汇林业的开展,碳汇计量日益受到国际社会重视。依据《造林项目碳汇计量与监测指南》,对浙江省嘉兴市高速公路互通枢纽区进行碳汇造林及碳汇计量,计量期为2011-2031年。结果表明:该项目在2011年表现为碳源,累计项目碳汇量为-81.59 t(二氧化碳当量),自2012年开始有碳汇,项目净碳汇累计量为1 747.84 t(二氧化碳当量),2017年项目累计量达到11 396.84 t(二氧化碳当量),到2031年累计量达到45 886.07 t(二氧化碳当量),年均净碳汇量为2 294.30 t(二氧化碳当量),释放O2为2 031.00 t,固碳效果明显,生态效益显著。 相似文献
9.
对新疆1996-2013年农业生产5大碳源碳排放及种植业碳汇进行测算,从时间、空间、结构3方面分析其农业生产碳排放变化特征;在农业净碳排放的基础上,构建净碳排放压力指数模型,分析新疆农业生产净碳排放压力变动趋势。研究表明,新疆农业生产碳排放在总量上呈“上升-下降-上升”趋势,碳排放强度总体上保持下降;在区域上表现出明显的差异性,喀什地区碳排放量最高,是克拉玛依市的72倍;从结构特征看,牲畜养殖、农用物资、农业活动占碳排放源的96%以上。牲畜碳排放量呈下降趋势,农业活动、农用物资碳排放呈明显增长趋势。碳汇总量增加较为迅速,农业生产净碳排放量整体保持下降趋势。净碳排放量大致分为“持平-下降”两个阶段变化特征。由净碳排放压力指数看出,新疆农业碳排放压力呈逐年递减状态。由此可知,要根据新疆实际合理适时调整优化农业产业结构,加快推进农业绿色化现代化;宏观布局,制定差异化的农业发展路线;加强农村地区的生态环境建设,提高农业生产资料的回收利用强度。 相似文献
10.
Sensitivity of boreal forest carbon balance to soil thaw 总被引：6，自引：0，他引：6
ML Goulden SC Wofsy JW Harden SE Trumbore PM Crill ST Gower T Fries BC Daube S Fan DJ Sutton A Bazzaz JW Munger 《Science (New York, N.Y.)》1998,279(5348):214-217
We used eddy covariance; gas-exchange chambers; radiocarbon analysis; wood, moss, and soil inventories; and laboratory incubations to measure the carbon balance of a 120-year-old black spruce forest in Manitoba, Canada. The site lost 0.3 +/- 0.5 metric ton of carbon per hectare per year (ton C ha-1 year-1) from 1994 to 1997, with a gain of 0.6 +/- 0.2 ton C ha-1 year-1 in moss and wood offset by a loss of 0.8 +/- 0.5 ton C ha-1 year-1 from the soil. The soil remained frozen most of the year, and the decomposition of organic matter in the soil increased 10-fold upon thawing. The stability of the soil carbon pool ( approximately 150 tons C ha-1) appears sensitive to the depth and duration of thaw, and climatic changes that promote thaw are likely to cause a net efflux of carbon dioxide from the site. 相似文献
11.
Simulations of carbon storage suggest that conversion of old-growth forests to young fast-growing forests will not decrease atmospheric carbon dioxide (CO(2)) in general, as has been suggested recently. During simulated timber harvest, on-site carbon storage is reduced considerably and does not approach old-growth storage capacity for at least 200 years. Even when sequestration of carbon in wooden buildings is included in the models, timber harvest results in a net flux of CO(2) to the atmosphere. To offset this effect, the production of lumber and other long-term wood products, as well as the life-span of buildings, would have to increase markedly. Mass balance calculations indicate that the conversion of 5 x 10(9) to 1.8 x 10(9) megagrams of carbon to the atmosphere. 相似文献
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13.
Atmospheric carbon dioxide and carbon reservoir changes 总被引：1，自引：0，他引：1
Stuiver M 《Science (New York, N.Y.)》1978,199(4326):253-258
The net release of CO(2) from the biosphere to the atmosphere between 1850 and 1950 is estimated to amount to 1.2 x 10(9) tons of carbon per year. During this interval, changes in land use reduced the total terrestrial biomass by 7 percent. There has been a smaller reduction in biomass over the last few decades. In the middle 19th century the air had a CO(2) content of approximately 268 parts per millon, and the total increase in atmospheric CO(2) content since 1850 has been 18 percent. Major sinks for fossil fuel CO(2) are the thermocline regions of large oceanic gyres. About 34 percent of the excess CO(2) generated so far is stored in surface and thermocline gyre waters, and 13 percent has been advected into the deep sea. This leaves an airborne fraction of 53 percent. 相似文献
14.
3种针叶树种树皮的阻燃性研究 总被引：3，自引：0，他引：3
在火烧迹地调查的基础上，分析了滇中云南油杉Keteleeria evelyniana，华山松Pinus armandii．云南松Pinus yunnanensis等3种树种在不同林火行为下的耐火性差异，确定了从树皮的阻燃性角度分析林木耐火性的研究方法。对3种树种的树皮的结构进行了调查，对树皮的平均厚度、含水率、导热系数、氧指数和热辐射作用下的质量损失过程和树皮内表面温度变化过程6个阻燃性相关因子进行了测定和分析。结果表明：①云南油杉树皮内皮层结构完整不开裂，外皮层疏松，平均厚度是云南松和华山松树皮的1．38和3．07倍，导热系数为云南松树皮和华山松树皮的67．66％和54．85％，氧指数是云南松和华山松树皮的1．25和1。33倍。在热辐射作用下，云南油杉树皮内表面升温速率低，热分解缓慢，阻燃性最强，云南松树皮的阻燃性次之，华山松树皮的阻燃性最差。②树皮阻燃性的不同造成了云南油杉、云南松和华山松树种间耐火性差异。根据3种树种树皮的阻燃性和林木耐火性差异提出了相应的森林消防措施。图3表3参11 相似文献
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[目的]研究火烧迹地中土壤轻组有机碳和重组有机碳含量及其与相关因子的关系。[方法]通过野外采样和室内分析,研究了大兴安岭地区不同强度火烧迹地0～15cm土壤轻组有机碳和重组有机碳含量的差异及其与相关因子的关系。[结果]对照样地、低强度和高强度火烧样地中轻组有机碳含量分别为2．53～10．15g／kg、3．06～12．37g/kg和2．16～11．66g/kg,轻组有机碳占总有机碳的比例为5．69％～19．60％,均值表现为低强度火烧轻组有机碳含量〉高强度火烧轻组有机碳含量〉对照样地轻组有机碳含量,差异不显著（P〉0．05）,但轻组有机碳含量在不同月份差异显著度不同;不同强度火烧样地中重组有机碳含量分别为35．09～54．59g/kg、35．83～64．15g／kg和23．83～51．11g／kg,重组有机碳占总有机碳比例为80．40％～94．31％,均值表现为低强度火烧重组有机碳含量〉对照样地重组有机碳含量〉高强度火烧重组有机碳含量,差异显著（P〈0．05）。[结论]对照样地、低强度和高强度火烧样地中轻组有机碳均值大小依次为低强度、高强度、对照样地,重组有机碳均值大小依次为低强度、对照样地、高强度。土壤轻组有机碳和重组有机碳含量与全氮呈正相关,与土壤温度、含水率呈负线性相关。 相似文献
16.
Al(OH)_3对树脂型阻燃剂的阻燃增效作用 总被引：3，自引：1，他引：3
为探讨Al(OH)3作为树脂型阻燃剂之阻燃协效作用,以树脂型阻燃剂(UDFP)为主剂,采用热分析法(TG、DTG、DSC)探讨其添加Al(OH)3前后处理和未处理杉木粉的动态,并用此技术对纯Al(OH)3的热性质也进行了相应的研究.结果表明:在219.44～315.09℃范围内,Al(OH)3于热分解脱水的过程中吸收了大量的热;热重分析表明Al(OH)3的加入可使木材热解时的起始温度降低,失重减小,产炭量相应增加;DTG曲线峰温降低,峰形变小,差热分析表明,尽管添加Al(OH)3前后的DSC图谱相似,在两曲线上均出现了2个明显的吸热峰,但后者峰温前移,峰形略显尖锐. 相似文献
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Wigg EE 《Science (New York, N.Y.)》1974,186(4166):785-790
The tests conducted with the three vehicles at different emission control levels suggest that, in the area of fuel economy and emissions, potential benefits with methanol blends are related to carburetion and are only significant in the case of the rich-operating cars built before emission control standards were imposed. Theoretical considerations related to methanol's leaning effect on carburetion support this conclusion. Potential advantages for methanol in these areas are therefore continuously diminishing as the older cars leave the roads. At present, these older cars use only about one-fourth of the totalc motor gasoline consumed and, before methanol could be used on a large scale, this fraction would be much smaller. The use of methanol in gasoline would almost certainly create severe product quality problems. Water contamination could lead to phase separation in the distribution system and possibly in the car tank as well, and this would require additional investment in fuel handling and blending equipment. Excess fuel volatility in hot weather may also have adverse effects on car performance if the methanol blends include typical concentrations of butanes and pentanes. Removal of these light hydrocarbon components would detract from methanol's role as a gasoline extender and if current fuel volatility specifications were maintained, its use could lead to a net loss in the total available energy for use in motor fuels. Car performance problems associated with excessively lean operation would also be expected in the case of a significant proportion of late-model cars which are adjusted to operate on lean fuel-air mixtures. If methanol does become available in large quantities, these factors suggest that it would be more practical to use it for purposes other than those related to the extending of motor gasoline, such as for gas turbines used for electric power generation. In this case, the "pure" methanol would act as a cleanburning fuel, having none of the potentially severe product quality problems associated with its use in motor gasoline, while the fuel oil or natural gas cLirrently burned in these tuLrbines CotLild be diverted to other ulses. 相似文献
19.
[目的]对南亚热带低山区柳杉人工林碳汇进行研究。[方法]研究广西国营六万林场低山区的31年生柳杉人工林生态系统碳素含量、碳储量及其空间分配特征。[结果](1)柳杉人工林不同器官平均碳素含量变化在498.5～530.3 g/kg,其含量排列为:叶子枯枝树干根蔸枝条细根干皮中根粗根;碳素含量随土壤深度的增加而逐渐减少。(2)低山区柳杉人工林的生态系统碳储量为393.651 t/hm2,其中植被层碳储量占生态系统碳储量的29.22%,而0～100 cm土壤层占70.78%。31年生柳杉人工林年净固碳量估算为3.709 t/(hm2.a),其中乔木层的年净固碳量为3.537 t/(hm2.a)。(3)0～20 cm土壤表层碳储量为132.418 t/hm2,比植被层的碳储量还高。[结论]加强低山区的植被保护,减少表层土壤的水土流失,可有效保持南亚热带低山区土壤对碳的长期吸存和维持。 相似文献
20.
小陇山林区森林固碳效益的研究 总被引：4，自引：3，他引：1
甘肃小陇山林区是甘肃省最大的天然次生林区,它对维持大气中的CO2和O2的动态平衡,减少温室效应以及提供人类的生存基础有着不可替代的作用和地位。据此,根据植物光合作用的原理,林木生长与林木吸收并固定大气中CO2二者之间的因果关系,利用蓄积量转化法、区域生物量估算等方法来计算该林区吸收固定和保存大气CO2的生态服务价值。得出小陇山林区生物量现存量4.26×107 t,固定CO2 6.95×107 t,折合纯C量1.90×107 t,固C的价值为4.15×109元人民币。由于计算中存在许多不确定性,对计算结果的含义、生物量扩展因子以及木材比重的取值进行了讨论和说明。 相似文献