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441.
虚拟水是当今水科学的研究热点,被认为是解决粮食与水资源安全的重要策略。在计算河南省2009年3种主要农作物生物需水量的基础上,结合作物单产得到初级产品单位虚拟水含量,明晰了这3种主要农作物的"虚拟水"空间分布格局。研究结果表明:河南省3种主要农作物中,棉花的单位虚拟水含量最高,玉米最小。空间上小麦的单位耗水量在三门峡最高,漯河最低;玉米的单位耗水量在三门峡最高,许昌最低;棉花的单位耗水量在鹤壁最高,信阳最低;3种作物单位虚拟水含量从东南向西北增加,尤其在东西方向最明显,但是不同作物又有细微差别。中东部水资源短缺区应提高玉米和小麦的种植面积,丘陵和山前平原单位耕地地表水丰富区可种植虚拟水含量较高的作物。提供了从虚拟资源视角认识水资源消耗的实证,可以对河南省农作物布局提供科学依据。 相似文献
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The equilibrium and kinetic adsorption of phosphate (P) from the Yellow River water onto desert particles taken from the Ulan Buh and Kubuqi deserts were investigated. Effect of the initial concentration of P and particulate matter on the sorption was explored. The kinetic studies show that adsorption rate was faster within the 0–8th hour period, then gradually decreased at 8th–48th hour period and basically tended to a dynamic equilibrium at the 48th hour, but there exists an adsorption difference of P onto different desert particles. The uptake process of P followed the pseudo-second-order rate model and the Morris-Weber diffusion equation which indicates that the adsorption process was mainly controlled by P diffusion inside the particles. The equilibrium investigation obtained an adsorption-desorption equilibrium mass concentration (EPC0) of P from the Yellow River water on desert particles with the range of 0.010–0.042 mg/L, which is higher than present P concentration in the Yellow River. This study indicates that desert particles entering the river might release P to the Yellow River. 相似文献
444.
白月明 《中国气象科学研究院年报》2008,(1):16-17
科技部农业科技成果转化资金项目“北方草原蝗虫气象监测预测服务系统推广应用”研究成果在北方草原蝗虫主要发生省、自治区气象部门推广应用,进行北方草原蝗虫气象监测预测。2008年度完成了任务书规定的各项工作。主要进展如下: 相似文献
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447.
两护村ZKC1孔位于洞庭盆地安乡凹陷的东南部,孔内第四系(底部跨上新世)厚达294 m,为河流和湖泊沉积,自下而上依次为上新世—早更新世华田组、早更新世汨罗组、中更新世洞庭湖组、晚更新世坡头组以及全新统等。对ZKC1孔第四系进行了详细的孢粉分析,自下而上划分出16个孢粉组合带。ESR年龄和孢粉组合及其反映的气候特征指示华田组下段形成于上新世末。根据孢粉组合特征,结合构造—沉积演化和区域气候背景,重塑洞庭盆地上新世末以来的气候演化过程:上新世末期由孢粉带Ⅰ和Ⅱ指示具暖干气候。早更新世经历了凉干(孢粉带Ⅲ、Ⅳ)→暖湿间凉干(孢粉带Ⅴ~Ⅶ)→冷干间温湿(孢粉带Ⅷ~Ⅹ)→暖较湿(孢粉带Ⅺ,Ⅻ)的气候演变过程。中更新世早期无孢粉样品(洞庭湖组下部砾石层),其沉积环境暗示冷干气候条件;中期由孢粉带ⅩⅢ反映出暖稍湿的气候特征;晚期因构造抬升缺失沉积,同期湿热化事件指示暖湿气候。晚更新世早期缺乏沉积,据区域对比应为寒冷气候;中期由孢粉带ⅩⅣ指示温较湿的气候特征;晚期缺失沉积,系寒冷气候下区域海平面下降所致。全新世经历了暖稍湿(孢粉带ⅩⅤ)→暖稍干(孢粉带ⅩⅥ)的演变。上述气候演变过程与ZKC1孔化学蚀变指数曲线反映的气候演变过程以及中国东部第四纪气候演化基本吻合。以孔深140 m为界,上部孢粉数量显著高于下部,种属也更为丰富。这一变化很可能对应于一次重要的地质事件,其成因有待今后深入研究。 相似文献
448.
AGNs with hard γ-ray emission identified so far are radio-loud.III Zw 2 is a radio intermediate AGN with a relativistic jet.We study its spectral energy distribution (SED) and find that the broad band emissions are dominated by the non-thermal emissions from the jet.We model its SED through a synchrotron + inverse Compton (IC) model.The results show that the IC component of III Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index Γ≈3.3 above 0.1GeV.The predicted flu... 相似文献
449.
Error evaluation of rasterization of vector data is one of the most important research topics in the field of geographical
information systems. Current methods for evaluating rasterization errors are far from perfect and need further improvement.
The objective of this study is to introduce a new error evaluation method that is based on grid cells (EEM-BGC). The EEM-BGC
follows four steps. First, the area of each land category inside a square is represented in a vector format. The size and
location of the square are exactly the same as those of a grid cell that is to be generated by rasterization. Second, the
area is treated as the attribute of the grid cell. Vector data are rasterized into n grids, where n is the number of land categories. Then, the relative area error resulting from rasterization for each land category in the
grid cell is calculated in raster format. Lastly, the average of the relative area error for all land categories in the grid
cell is computed with the area of a land category as weight. As a case study, the EEM-BGC is applied for evaluating the rasterization
error of the land cover data of Beijing at a scale of 1 to 250,000. It is found that the error derived from a conventional
method (denoted as y) is significantly underestimated in comparison with that derived from the new method (denoted as x), with y = 0.0014x
2.6667. The EEM-BGC is effective in capturing not only the spatial distribution of rasterization errors at the grid-cell level but
also the numerical distribution range of the errors. The EEM-BGC is more objective and accurate than any conventional method
that is used for evaluating rasterization errors. 相似文献
450.
Mingqun Huo Qian Sun Yuhua Bai Peng Xie Zhaorong Liu Jinlong Li Xuesong Wang Sihua Lu 《Journal of Atmospheric Chemistry》2010,67(1):29-43
Rainwater samples were collected at four sites, including Beijing and Mazhuang Town in the north of China, Shenzhen and Mangdang
Mountain in the south of China. Character of atmospheric particles and gases were also measured at Mazhuang Town and Mangdang
Mountain. Both of Beijing and Shenzhen are urban sites; Mazhuang Town and Mangdang Mountain are rural and remote sites respectively.
The atmospheric pollution at rural plain site in the north of China was more serious than that at remote mountain site in
the south of China. At Beijing, Mazhuang Town, Shenzhen and Mangdang Mountain the average pH values in rainwater were 6.02,
5.97, 4.72 and 4.81, respectively and the concentrations of total ions in rainwater were 1454, 1125, 187 and 191 μeq/l, respectively.
While the acidity of the rain was higher in the south than that in the north, the rainwater in the north of China was more
severely polluted than that in the south. The major acidic ion in the rainwater is SO42-, and NH4+ is the most important neutralizing ion in rainwater at the four sites, followed by Ca2+. The amounts of organic acid in precipitation were compared with other sites in the world. The ratios of organic acid to
total free acid in rainwater at Mangdang Mountain was 13.8% and the influence of organic acid on acidity of rainwater at mountain
site in the south of China is more important. The variation of atmospheric particles, gases and components in rainwater and
cloud-fog water during special rain and cloud-fog events was discussed. The importance of washout process varied with atmospheric
species. The impacts of rainfall, rain duration time and wind speed on wash-out process were estimated by regression analysis. 相似文献