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11.
秸秆烟尘和灰烬中元素碳的稳定同位素组成 总被引:1,自引:1,他引:0
选取稻草、麦草和玉米秸秆各6个品种,进行室内模拟焚烧试验,用同位素质谱计测定了灰烬和烟尘中元素碳(EC)的同位素比值.结果表明,稻草明火和闷烧烟尘中EC的δ13C平均值分别是-28.3‰、-28.7‰,比稻草总碳分别轻2.7‰、3.0‰.麦草明火和闷烧烟尘中EC的δ13C平均值分别为-28.5‰、-28.0‰,比麦草总碳分别轻0.1‰、重0.4‰.玉米秸秆明火和闷烧烟尘中EC的δ13C平均值分别为-17.2‰、-13.6‰,比秸秆总碳分别轻3.4‰、重0.2‰.在稻草明火和闷烧灰烬中,EC的δ13C平均值分别是-27.5‰、-27.3‰,比稻草总碳分别轻1.8‰、1.6‰.在麦草的明火和闷烧灰烬中,EC的δ13C平均值分别为-27.4‰和-26.0‰,比麦草总碳分别重0.9‰和2.4‰.在玉米秸秆的明火和闷烧灰烬中,EC的δ13C平均值分别为-15.0‰和-14.8‰,比玉米秆总碳分别轻1.2‰和1.0‰.3类秸秆,尤其是稻草和玉米秸秆,其烟尘和灰烬中的EC均发生了明显的同位素分馏.其同位素组成对于识别和估算大气气溶胶中此类秸秆燃烧来源的EC有参考意义. 相似文献
12.
13.
污泥中的有机质、营养成分可为农业生产提供重要的有机肥源,但污泥中的重金属是制约污泥农用的重要因素,为检验污泥堆肥施用后对作物及土壤的影响,文章对污泥与稻草或木屑堆肥的产品进行了盆栽试验研究。结果表明,污泥与稻草或木屑的堆肥作为肥料施用于萝卜(Brassicacampestris)和菜心(Brassicaparachinensis),产量明显提高,部分堆肥产品增产效果优于化肥,且后效明显。堆肥施用使土壤中有机质、各养分含量增加,微生物活动增强、数量增加,然而作物和土壤中的重金属含量也有不同程度的提高。 相似文献
14.
大气CO2浓度不断增加将以两种方式影响作物的代谢、生长发育和产量的形成:一是通过温室效应“加热”气候,改变降水类型,进而影响作物;二是浓度变化本身对作物生理过程的影响。介绍了国内外近年来在与CO2浓度有关的作物生理实验方面取得的进展及其主要结果。 相似文献
15.
Yukiyo Yamamoto Thomas Oberthür Rod Lefroy 《Environment, Development and Sustainability》2009,11(3):639-654
In the mountainous regions of northern Laos, shifting cultivation, or slash-and-burn agriculture, is widely practiced. However,
the crop–fallow rotation cycle is becoming shorter owing to forest conservation policies and population pressure, causing
loss of productivity that deleteriously affects farmers’ livelihoods in the region. To investigate regional land use conditions,
we have developed a method of identifying the crop–fallow rotation cycle from Landsat Thematic Mapper (TM) and Enhanced Thematic
Mapper+ (ETM+) data. We assessed the impact of the identified cycle on plant production measured by Normalized Difference
Vegetation Index (NDVI). The study site was an area in Luang Prabang Province. Using eight TM and ETM+ images acquired annually
from 1995 to 2003, except for 1998, when cloud-free data were not collected, we classified land use in each year as crop or
fallow by the presence of vegetation in the late dry season. Conformity with fallow age determined by field investigation
was 69.1%. The cultivation frequency from 1995 to 2002 showed that 77,000 ha (17.3% of the study site) had not been used for
cropping during the period, but 41,000 ha (9.2%) had been used every year. Of the study site, 129,000 ha (29.1%) was cultivated
one or two times, 83,000 ha (18.7%) was three or four times, and 54,000 ha (12.2%) was five or six times. The NDVI of crops
in November did not provide sufficient evidence to prove the assumption that a longer fallow period would result in better
crop yields. Instead, the regeneration of fallow vegetation was evidenced by the higher NDVI values after longer fallow. More
than 8 years would be needed to reach the same NDVI as forest. From the produced maps indicating fallow age and cultivation
frequency, we found that areas with high potential for regeneration decreased as cultivation frequency increased. Areas near
rivers were intensively used, and fallow length was accordingly short. Low-potential areas were found in the western basin
of the Mekong River. This spatial information can be used to detect areas where biomass productivity is at high risk of deteriorating.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
16.
17.
Peter Weindler Frank Böhme Varis Liepa Wolfgang Wiltschko 《Behavioral ecology and sociobiology》1998,42(4):289-294
To assess the role of celestial rotation during daytime in the development of the magnetic compass course, pied flycatchers
(Ficedula hypoleuca Pallas, Muscicapidae) were handraised in Latvia under various celestial and magnetic conditions. Tests were performed during
autumn migration in the local geomagnetic field (50 000 nT, 73° inclination) in the absence of celestial cues. A group of
birds that had never seen the sky showed a bimodal preference for the migratory southwest-northeast axis, whereas a second
group that had been exposed to the natural sky from sunrise to sunset in the local geomagnetic field showed a unimodal preference
for the seasonally appropriate southwesterly direction. A third group that had also been exposed to the daytime sky, but in
the absence of magnetic compass information, also oriented bimodally along a southwest-northeast axis. These findings demonstrate
that observing celestial rotation during daytime enables birds to choose the right end of the migratory axis for autumn migration
at the Latvian test location. This transformation of axial behavior into appropriate migratory orientation, however, requires
the birds to have simultaneous access to information on both celestial rotation and the geomagnetic field.
Received: 19 September 1997 / Accepted after revision: 22 November 1997 相似文献
18.
Paul N. Wilson Teddy J. Goldammer James C. Wade 《Journal of the American Water Resources Association》1988,24(1):1-9
ABSTRACT: Urban wastewater can be a valuable source of water and plant nutrients for agricultural producers, particularly in arid regions. The scientific literature reveals cautious optimism concerning the biological, institutional, and economic viability of irrigating crops with secondary-treated effluent. A derived effluent demand function for agricultural producers near Tucson, Arizona, reveals a potential annual demand of 11,000 acre-feet under present price and proposed delivery system conditions. In this case, wastewater could be exchanged for ground water and both the urban and rural areas would gain. 相似文献
19.
20.
Rameshwar S. Kanwar 《Journal of the American Water Resources Association》2006,42(6):1493-1501
Abstract: Diverse cropping systems can have significant impacts on nutrient losses through tile drain systems and to surface water bodies (rivers and streams). Increased transport of nitrogen to water bodies can reduce dissolved oxygen and enrich the supply of nutrients, resulting in hypoxic zones. With the objective of reducing the transport of nutrients from agricultural watersheds, long term studies (1990 to 1998) were conducted in Iowa to investigate the impact of tillage, crop rotation, and N-management practices on NO3 -N leaching losses to tile drain water. Results of these studies indicated that continuous corn production systems required higher input of nitrogen fertilizers and resulted in significantly higher NO3 -N leaching losses compared to rotated corn in plots either fertilized with manure or urea ammonium nitrate. Also, rotated corn gave higher corn yields, 8 megagrams per hectare (Mg/ha) versus 6 Mg/ha, than continuous corn. The higher N application rates resulted in increased NO3 -N concentrations in tile water. A strip cropping system with alfalfa lowered NO3 -N concentrations in tile water to less than 10 mg/l. These studies indicated that better land use practices can reduce NO3 -N leaching losses to surface and ground water systems and will help in mitigating environmental concerns of the production agriculture. 相似文献