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1.
以木薯淀粉为原料,探讨了应用于造纸行业中具有一定取工的淀粉磷酸单酯合成的最佳工艺条件。 相似文献
2.
S. I. Efe 《Natural Hazards》2010,55(2):307-319
The study adopted the experimental research design and field survey of the oil-producing region of Nigeria for the past 10 years.
A total of 100 sterilized rain gauges were randomly distributed on the basis of 50 each to the eastern and western division
of the oil company operating in the region. The rainwater samples harvested through this process were transferred into sterilized
plastic containers and kept in coolers and taken immediately to the laboratory for analysis soon after every rain event. The
rainwater samples were analysed in the laboratory with the most appropriate techniques. The physicochemical characteristics
of rainwater harvested were subjected to paired t test and 3-year moving average statistical analysis. The following are the results: There is widespread acid rain in the
region, this is evident from pH values that span 4.98–5.15 and 5.06 mean values. The result also revealed that acid rain (pH)
varied significantly (P > 0.05), and it decreases with increasing distance from gas flare sites throughout the period of study. Other physicochemical
characteristics of rainwater resources conform to safe limit with the exception of turbidity, TSS, Pb and NO3, which is also significant at P > 0.05 with increasing distance from the gas flare sites, as such they decreases with increasing distance. This certainly
has serious environmental effects on the human and other species, soil, water and vegetation resources and calls for the extinction
of gas flaring, in this region. Sources of water that are acidified should be periodically limed to reduce the acid concentration
in such water. 相似文献
3.
钼是人体和农作物必需的有益元素,具有防癌抗癌作用。由于不同地区土壤中钼含量和土壤酸碱性的不同,农作物中钼含量有很大差异,同时不同农作物对钼的吸收也不相同。研究不同农作物中钼富集规律可以为健康地质发展、富钼农产品开发、功能农业发展、种植结构调整提供依据。本文以洛阳市硒资源详查区及其他农业种植区为研究区,通过采集22种大田种植的农作物及其根系土,采用电感耦合等离子体质谱法（ICP-MS）测定土壤和农作物钼含量,研究了不同农作物钼含量特征及其影响因素。结果表明：洛阳市土壤钼含量较高,是中国土壤富钼特色地区。绿豆、豇豆、黑豆、黄豆、红小豆和花生是富集钼的主要农作物,钼平均含量>9mg/kg,富集系数>500%,属于钼的超富集农作物。芝麻、豆角、谷子、小麦、玉米和油菜籽钼含量较高,钼含量均值介于0.446～2.437mg/kg,富集系数介于40%～300%,属于富钼农作物。辣椒、大蒜、红薯、秋葵的钼含量介于0.1～0.3mg/kg,富集系数介于10%～30%,属于高钼农作物。苹果、梨、葡萄、石榴、樱桃与中药材银条的钼含量<0.05mg/kg,富集系数<5%,是低钼农作物。大多数农作物钼含量与根系土钼含量呈正相关,而苹果、葡萄、石榴、樱桃等水果钼含量与根系土钼含量呈负相关。研究揭示了在碱性环境下土壤中的钼更容易被农作物吸收。区内农作物与中国其他地区相比均呈富钼特征,是开发富钼农业产业的有利地区。依据不同农作物钼含量,选择出绿豆、豇豆、黑豆、黄豆、红小豆和花生是研究区特色富钼农产品,芝麻、豆角、谷子、小麦、玉米和油菜籽是富钼农产品,辣椒、大蒜、红薯、秋葵属于高钼农作物。本成果为研究区富钼农产品开发、调整种植结构提供了科学依据。 相似文献
4.
D. Anhuf 《GeoJournal》1990,20(3):221-230
The study attempts to relate crop yields to climatic events in the Sahelian Zone of Africa. The examples are taken from Senegal, Sudan and Tunisia. Theinvestigation was centered to examine closely the relations between weather and crop yields, that means first of all to analyze the influence of the inter-annual variations of the weather on the yields. The aim was to reveal the dependency of the temporal variability of the yields (1960–1980) on the climatic parameters during the different phenological stages of the plants. This analysis made it possible to develop models of prognosis for different cultivated plants (food crops basically). In general suitable models of forecasts could be established for all food crops. An early and exact prediction of harvest losses or surpluses could reduce negative effects for the respective population in unfavourable, and induce food storage in favourable years. 相似文献
5.
R. Corobov 《GeoJournal》2002,57(3):195-202
Statistical methods for assessing crop sensitivity and vulnerability to climate change in Moldova were demonstrated and the
following procedures were discussed: (1) projections of likely agroclimatic change; (2) assessments of crop sensitivity to
climate change; and (3) assessments of the impact of climate change on crops. In order to predict the future agroclimate,
key meteorological variables were transformed statistically to correspond to changes in plants' heat and water supply characteristics.
Sensitivity of crop production was examined for corn and winter wheat. By combining the agroclimatic changes with crop response,
possible impacts have been estimated and form a basis for possible adaptation strategies. It was shown that regional climate
change can result in elevated aridity of Moldova's territory, especially during periods of crop growth. Cultivation of cereal
crops in new agroclimatic conditions without adaptation measures will negatively affect yields, especially of winter wheat,
whose yield decrease may be 18–39% by 2020s and 22–50% by 2050s. Corn yields may increase by 0–3% and 1–6%, respectively.
As an example of adaptation, it is shown that the use of an increased number of late hybrids results in a 25–35% increase
in corn yields.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
In Kenya the government is promoting diversification of crops to embrace high value crops and drought resistant crop varieties
in efforts to reduce poverty in rural areas. Sugar beet is one of the crops considered as an option in this context and it
is therefore important to increase knowledge about the potentials in the country for cultivating this crop. Sugar beet trials
conducted in Nyandarua and Butere Mumias Districts of Kenya have shown that the crop yields are comparable to those obtained
in traditional sugar-beet cultivation regions of Europe. Since sugar beet yield is affected by climate and soils, the results
of Nyandarua and Butere Mumias sugar beet trials are not adequate to propose that comparable yields can be obtained elsewhere
in the country and other tropical regions. Physical land evaluations assessing the potentials and constraints for sugar beet
production are therefore essential. The objectives of this study was to develop a Tropical Sugar Beet Land Evaluation Scheme
(TSBLES) that can aid assessment of the suitability of different areas in the tropics for sugar beet cultivation; and to test
this scheme for an assessment of suitable sugar beet zones and land areas in Kenya. The development of the scheme was based
on various literature sources and expert judgment on sugar beet requirements, and a Tropical Sugar Beet yield prediction Model.
The TSBLES accounts for physical conditions of land i.e. climatic, edaphic and topographic conditions. According to the assessment
results 27% of the land area in Kenya is suitable for sugar beet cultivation. Of this area, 5% is highly suitable, another
5% is moderately suitable and 17% is marginally suitable. Most of the highly suitable land area is concentrated in Rift Valley,
Central and Nyanza provinces. The Rift Valley has the highest share of the suitable land area. 相似文献
7.
Timothy Beach 《Geoarchaeology》1998,13(8):759-791
The soils and subsistence of ancient Maya Chunchucmil in northwestern Yucatán are the focus of this paper. Today and historically, the population and crop yields here have been very low. Archaeological field work, however, has shown the Late Classic site to be highly populated with densely packed walled mound and field groups. It is enigmatic that this high ancient Maya population existed in a region of meager crop and soil potential. This enigma is addressed by investigating contemporary Maya agriculture, geoarchaeological evidence, and soil potential for intensive agriculture. The local Maya soil classification of kancab and boxluum synthesizes the Alfisols, Inceptisols, and Mollisols described here. The major soil limitations are shallowness, broad areas with no soil, insufficient water holding capacity, and variable deficiencies in phosphorous, potassium, and zinc. Evidence for intensive agriculture and alternative crops can be seen in widespread field walls compartmentalizing the landscape, sascaberas, and preliminary phosphate fractionation signatures. © 1998 John Wiley & Sons, Inc. 相似文献
8.
Karl S. Zimmerer Prof. Dr. 《GeoJournal》1992,27(1):61-72
The fate of agricultural biodiversity varies among the native crops produced in a mountainous region. Four native crops (potatoes, maize, ulluco, quinoa) cultivated in the southern Peruvian sierra demonstrate different patterns of cultivar loss and cultivar maintenance. Contingent social, economic and environmental conditions in mountain agriculture shape the distinct fates befalling the cultivars in each crop. Three sets of specific conditions contribute to differences in the patterning of cultivar loss and maintenance: (1) proximate conditions in the local peasant economy, particularly access among agricultural households to land, labor, and capital, and changes in the availability and quality of the three endowments; (2) the social and cultural value of the crop in the local diet and cuisine; and (3) the biogeographic patterning of cultivars. Maintenance of cultivars currently marks the ulluco and quinoa crop as well as many potato and maize types. Cultivar loss besets the fast-maturing potato S. phureja and the slow-maturing maize types. To incorporate variable in situ crop-conservation programs into development planning for montane regions requires thoroughly assessing the contingent conditions for continued production. 相似文献
9.
Muhammad Zia ur Rehman Muhammad Rizwan Shafaqat Ali Asif Naeem Balal Yousaf Guijian Lui Hinnan Khalid Saifullah Farhan Hafeez Muhammad Azhar 《Arabian Journal of Geosciences》2018,11(19):594
A field study was performed to determine the efficiency of diammonium phosphate (DAP) applied alone or combined with biochar, lignite, and farmyard manure (FYM) on growth and cadmium (Cd) accumulation in wheat and rice. Before crop sowing, different treatments were applied in the field such as a control (T1), DAP alone (0.1%, T2), DAP + lignite (0.05% each, T3), DAP + FYM (0.05% each, T4), and DAP + biochar (0.05% each, T5). Afterwards, the wheat seeds were sown in the soil. At wheat postharvest, rice was sown without any further treatment. Raw effluent was applied as an irrigation source during the whole growth period of both crops since it is the common practice of the farmers of study area. It was revealed that the use of amendments enhanced the yield and photosynthesis but lowered the Cd contents in straw as well as grains of both crops. In both crops, the highest yield of straw and grain was found in DAP + FYM whereas the lowest Cd concentration was found in DAP alone. The ammonium bicarbonate-DTPA extractable Cd of post wheat and post rice soils were decreased while the soil pH and immobilization index were increased in all treatments as compared with the control. The present field study highlighted that the DAP + FYM can be effective in increasing yield with decreased Cd concentrations in crop grains. 相似文献
10.
本文采用酸前法合成工艺,探讨了木薯淀粉羧甲基化反应的一般规律;考察了反就绎产物取代度和粘度的影响,通过正交试验,找到了最佳工艺条件,并对产物的性能与羟甲基纤维素进行了对比测试。 相似文献
11.
12.
全球气候增暖对甘肃农作物生长影响的研究进展 总被引：16，自引：2，他引：14
系统总结了甘肃省科技攻关重大项目“甘肃干旱生态环境对全球气候变暖的响应研究”等3个课题的主要成果和研究进展。在揭示甘肃省现代气候变化基本特征是冬暖夏干的基础上,比较系统地综述了越冬作物（冬小麦、冬油菜）、喜凉作物（春小麦、马铃薯、胡麻）和喜温作物（玉米、棉花、酿酒葡萄）等8种主要农作物的生长发育、适生种植区高度和种植面积、产量和品质等对现代气候变化的响应特征。现代气候变化对甘肃农作物生长的影响非常突出,已对农作物安全生产与农业可持续发展构成了严重威胁。其研究结果为建立现代农业发展模式,旱作农业生产机制,农作物安全生产提供科学的指导意见。 相似文献
13.
A. P. Chandrasekaran S. Sivamani V. Ranjithkumar 《International Journal of Environmental Science and Technology》2017,14(6):1291-1296
A number of previous studies established that the autoclave-mediated pretreatment enabled the efficient way of producing fermentable sugars from lignocellulosic residues. Hence, our emphasis was on studying the surface morphology of cassava stem to reveal its complex internal structure. In this study, combined organic (oxalic)–inorganic (sulfuric) acid was utilized for the pretreatment of cassava stem at 121 °C and 1 bar of pressure for 15 min. For the pretreatment, mixture containing 10 mL of 1% (w/v) of oxalic acid and 1% (w/v) sulfuric acid (5 mL each) was added to 1 g cassava stem and autoclaved. Pretreated samples were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet spectroscopy (UVS). FTIR spectral studies confirmed the removal of hemicellulose and lignin from the pretreated cassava stem (PCS) when compared with untreated cassava stem. SEM micrographs revealed the decimation in the surface of cassava stem after pretreatment. XRD motifs shown that crystallinity index of PCS decreased from 63 to 52%. Thus, this study established the structural modifications to unlock its valuable components for further applications. 相似文献
14.
模拟作物适宜生长区的时空分布是分析气候变化对作物生长影响、提高作物生长适应能力的重要内容。选择影响主要粮食作物(小麦、玉米和水稻)生长的气候要素,结合地表土壤和地面高程要素与农业观测站数据,模拟和分析1953—2012年主要粮食作物适宜生长区的变动,评估气候变化下作物的适应能力。研究发现:(1)60年来3种粮食作物适宜生长区对气候变化响应程度从大到小依次是小麦、水稻和玉米。(2)同一时空尺度上,主要粮食作物适宜生长类型区在南方农区较北方农区多样化,在山地较盆地多样化,在高原较平原多样化。(3)小麦生长适应气候变化的能力在多数农区略有上升。玉米生长的适应能力在北方和南方农区分别略微提高和下降。水稻生长的适应能力在长江中下游区、西南区和华南区相对稳定,在黄淮海区和东北区分别下降和提高。(4)60年来,主要粮食作物综合生长适应气候变化的能力在黄淮海区和长江中下游区下降,在其余农区升高。(5)玉米和水稻适宜生长区分别与播种面积和作物产量显著相关,这为模拟未来不同气候情景下二者适宜生长区的分布提供了可行性。小麦适宜生长区与播种面积和产量均不显著相关,未来需要考虑更多因素精准识别小麦适宜生长区,以便更为有效地提高小麦生长对气候变化的适应能力。 相似文献
15.
Temperature dependence of the polarized electronic absorption spectra of olivines. Part I – fayalite
Polarized electronic absorption spectra of orthorhombic fayalite, Fe2SiO4, [E || a(|| Z),E || b(|| X), E || c(|| Y)], space group Pbnm, have been studied in the temperature range 293 ≤T/K ≤ 1273. The spectra were analysed into component bands originating from spin-allowed dd transitions of iron(II) at the different sites, M1 and M2, in the structure. The assignments of bands, made on the basis
of the polarization dependence of the spectra and considerations of transition energies, were confirmed by the analysis of
the temperature-dependent spectra. The temperature dependencies of integral intensities, half band widths and energy positions
of absorptions bands caused by Fe2+ on the different octahedral sites, M1 and M2, were evaluated for the individual transitions. Independent of the site symmetry,
absorption bands shift to lower energies and half band widths increase on rising temperature. The temperature dependence of
band intensities depends on site symmetry. The integral intensities are found to increase with temperature for the transition
metal ion on a centrosymmetric site, or remain constant when the site is missing an inversion centre. This is consistent with
the general conclusion of Taran et al. (1994).
Received: 11 October 2001 / Accepted: 17 January 2002 相似文献
16.
通过对三原—阎良地区土壤与农作物采样分析研究,发现该地区土壤环境总体清洁,足硒—富硒土壤占调查区总面积的94.62%,富硒土壤分布广,具备了开发富硒农产品的基本土壤条件;大宗粮食作物均达富硒水平,其中油菜富硒率100%,小麦富硒率99.4%,玉米富硒率88.1%,大部分蔬菜也都达到了富硒蔬菜的标准,适合种植富硒大宗粮食作物和蔬菜;农作物硒与土壤硒整体相关性较好,玉米硒含量与根系土硒含量相关系数为0.788,小麦硒含量与根系土硒含量相关系数为0.612,富硒产业发展前景好。三原—阎良地区是陕西省关中地区重要的粮食、蔬菜产地,建议选择示范点开展富硒农产品种植试点,为关中地区富硒资源开发利用提供科学依据,在此基础上打造建设一批富硒粮食、蔬菜产业基地,更好地支撑服务乡村振兴战略和精准脱贫攻坚战。 相似文献
17.
Geochemical processes controlling the spatial distribution of selenium in soil and water,west central South Dakota,USA 总被引：8，自引：0，他引：8
Selenium (Se) is essential in the human diet, but has a low threshold for toxic concentration. It is recommended that nutrients
such as Se should be consumed through foods as part of a normal diet. Se concentrations in crops and meat depend on the amount
of labile Se in the soil where crops and forage are grown. Therefore, managing agriculture for optimal Se in grain crops and
forage requires an understanding of the distribution and mobility of Se. Elevated concentrations of Se occur in waters, soils,
and forage 120 km west of Pierre in west central South Dakota, USA. The research site lies in an elevated, dissected plain
where soils developed on gently dipping Pierre Shale. Soils were sampled along catena transects and waters collected from
soil, ponds, and shallow borings in areas of known elevated forage and crop Se. Soil extracts from saturated-paste extraction
and acid (aqua regia and hydrofluoric acid) extraction were analyzed. Selenate was the dominant Se species in both acid and
saturated-paste extracts; selenite and organic Se were below detection (<0.2 ppb) in the same soil extracts. On average, 98% of soil Se was not water-soluble. The distribution of total Se shows much less spatial variation than water-soluble
Se in the areas sampled. Se shows correlation with organic carbon in soils and waters, suggesting its association with organic
carbon. Ca shows some correlation to Se in acid extracts, but not in saturated-paste extracts or in waters. Total Se shows
no significant correlation to Na, Mg, and total S in the soils. Se in saturated-paste extracts and water samples shows good
correlations with Na, Mg, and SO4, suggesting that evaporitic Na–Mg–sulfate minerals may temporarily concentrate water-soluble Se in shallow soils. The dissolution
and precipitation of these Na–Mg–sulfate salts together with pH and oxidation–reduction conditions apparently control water-soluble
Se distribution and mobilization in shallow subsurface environments. 相似文献
18.
Yield variability of crops in Japan 总被引：1，自引：0，他引：1
Z. Uchijima Dr. 《GeoJournal》1981,5(2):151-163
Results of the investigation on the yield variability of main crops in Japan are reported. The analyses of yield variability
suggest that the yield variability of rice is generally less than that for upland crops. This is accounted for by the fact
that the adverse effects of unusual weather events on rice crops are greatly reduced by flood water. Yield and climate data
are analysed to obtain relationships between yield variability and weather variability. The analysis indicates that the influence
of weather variability on crop yield is greater in regions with poor agroclimatic resources than in regions with good agroclimatic
resources. The spectral analysis is made to study in more detail regional characteristics of yield fluctuations. It is reported
that Japan can be classified into five districts from the stand point of characteristics of yield fluctuations. 相似文献
19.
V. I. Abramenko 《Astronomy Reports》2003,47(2):151-160
Observations of the total magnetic field in the active region NOAA 6757 have been used to study the turbulence regime from 2.5 h before the onset of a 2B/X1.5 flare until two minutes after its maximum. The curvature of the exponent ζ(q) for the structure functions of the B z field increases monotonically before the flare (i.e., the multifractal character of the B z field becomes more complex) but straightens at the flare maximum and coincides with a linear Kolmogorov dependence (implying a monofractal structure for the B z field). The observed deviations of ζ(q) from a Kolmogorov line can be used for short-term forecasting of strong flares. Analysis of the power spectra of the B z field and the dissipation of magnetic-energy fluctuations shows that the beginning of the flare is associated with the onset of a new turbulence regime, which is closer to a classical Kolmogorov regime. The scaling parameter (cancellation index) of the current helicity of the magnetic field, k h , remains at a high level right up until the last recording of the field just before the flare but decreases considerably at the flare maximum. The variations detected in the statistical characteristics of the turbulence can be explained by the formation and amplification of small-scale flux tubes with strong fields before the flare. The dissipation of magnetic energy before the flare is primarily due to reconnection at tangential discontinuities of the field, while the dissipation after the flare maximum is due to the anomalous plasma resistance. Thus, the flare represents an avalanche dissipation of tangential discontinuities. 相似文献
20.
海洋生物质能研究进展及其发展战略思考 总被引：3，自引：0，他引：3
生物质能的研究与开发的目的是解决化石资源短缺和温室气体排放等全球性问题。利用油料作物生产生物柴油和利用淀粉作物生产燃料乙醇是当前生物质能产业化开发的重要内容,其原料来源主要依赖农作物,从而导致了生物质能开发与粮食、耕地和水资源竞争的局面。海洋生物质能的开发和利用为解决上述问题提供了一条可能有效的出路。介绍了海洋生物质能的国内外研究进展,分析了有关国家战略需求和关键科学问题,提出了我国发展海洋生物质能的战略思考和下一步的研究重点。 相似文献