基于定量遥感反演的内陆水体藻类监测

叶绿素作为衡量湖泊富营养化的重要指标,利用遥感技术对其进行实时动态监测具有重要意义。以太湖为例,通过对水体实测光谱和水质采样数据的分析,建立了光谱反射率比值与叶绿素a浓度的回归模型。结果显示,700 nm附近波段与625 nm附近波段所构建的比值模型R2最高,710 nm以后波段与其他可见光波段所构建的比值模型的R2会随可见光波长的增大而逐渐下降。在高光谱遥感估算模型的基础上,应用同步MODIS卫星遥感数据进行了太湖叶绿素a浓度的空间分布反演,并基于MODIS绿度指数建立了太湖藻华水体信息提取模型,从叶绿素a浓度估算和藻华信息提取两个方面实现了太湖藻类空间分布特征的定量反演,为太湖等大型内陆水体藻类的实时定量遥感监测提供了新的研究思路。     

太湖藻华水体的遥感监测与预警

受水体富营养化的影响,藻华暴发已成为目前我国湖泊和水库面临的主要环境问题之一.针对藻华水体的动态监测,特别是提前预警技术的研究对于内陆水体的污染防控具有重要意义.该文结合高光谱实验数据,综合运用指数法和遥感影像假彩色合成法.建立了基于MODIS数据的太湖藻华水体遥感信息提取模型,并在此基础上,对2007年3～5月间太湖藻华形成过程进行了遥感实时动态监测研究.通过埘春夏季节蓝藻水华的空间分布特征和藻华不同形成阶段的特征分析,提出了太湖藻华水体预警的技术方法,即当MODIS水体绿度指数GI集中分布于0.6～0.8区间时,可认为太湖水域已进入蓝藻水华大规模暴发前的预警阶段.     

水体氮磷高光谱遥感实验研究初探

水体中氮、磷含量是衡量水质的主要指标,遥感技术在环境监测中具有重要意义。利用高光谱遥感技术,通过测定实验室纯水条件下配比不同浓度氮、磷溶液的反射光谱,探索水体中有效态氮、磷的特征光谱。结果表明,氮在波长404和477nm各有一反射峰,磷在350nm处有一明显反射峰,且与浓度有很好的相关性,并以这些特征值建立了氮、磷浓度的遥感模型,为进一步遥感定量研究湖泊、水库和河流等大型内陆水体中的氮、磷奠定了基础。     

基于MODIS植被指数时间谱的太湖2001年-2013年蓝藻爆发监测

藻类水华爆发已成为影响内陆水体生态环境的重要因素。遥感能够提供实时的大范围观测,在水华监测中起到越来越重要的作用。遥感植被指数已广泛应用于藻类水华监测中,通过对研究区植被指数图像进行阈值分割,能够反映不同子区域内的藻类爆发程度;然而阈值分割法的结果只能反映某一时间点(图像获取时)的藻类爆发状况,无法表征长时间内藻类的变化。相比于单个时间点的植被指数,植被指数时间谱(时谱)包含藻类的物候信息,能够更加全面准确地反映藻类的长时间变化。目前,植被指数时间谱还尚未应用到水华相关研究中。选取2001年—2013年太湖区域的 MODIS NDVI数据,构建年度 NDVI时谱数据,利用(support vector machine,SVM)方法对每年的太湖蓝藻水华爆发强度进行分类,将太湖重度、中度和轻度蓝藻水华爆发的区域以及水生植物的区域提取出来,得到其空间分布和面积;并从2007年的时谱数据中抽取了8个时间点的NDVI图像,利用传统阈值分割法提取太湖重度、中度和轻度蓝藻水华爆发的区域,将结果与2007年时谱数据分类的结果进行对比。结果表明：所提出的方法能够更加全面准确地对太湖蓝藻爆发强度进行分类,通过 NDVI时谱曲线提供的丰富物候信息可准确区分蓝藻与水生植被区域。本研究有望为准确掌握和预测藻类水华的爆发趋势及强度提供有效手段。     

基于环境一号卫星超光谱数据的多元回归克里格模型反演湖泊总氮浓度的研究

水体中总氮含量是表征湖泊水质的主要指标,利用遥感技术对其动态定量监测可以及时掌握湖泊污染状况.文章以巢湖为例,利用HJ-1A卫星HSI超光谱遥感数据,通过分析总氮与叶绿素a、悬浮物的相关性,采用回归克里格方法建立总氮浓度的定量反演模型,实现了对巢湖水体总氮浓度的反演.结果显示,波段B72,B79和B97的多元线性组合与...     

基于珠海一号高光谱卫星的巢湖叶绿素a浓度反演

叶绿素a是重要的水质参数,可以衡量水体的富营养化程度。遥感技术可以实时、快速、大范围地获取水体中叶绿素a的浓度与分布,对于水生态环境的评价及治理具有重要意义。内陆水体的光谱特征复杂,宽波段的多光谱遥感难以精确获取水体的光谱信息。国产珠海一号高光谱卫星因其光谱分辨率高,波段多等优势在内陆湖泊的遥感监测中具有广阔的应用前景。基于珠海一号高光谱数据,充分发挥其高光谱分辨率的优势,对巢湖的叶绿素a浓度进行反演,从影像中提取实测点处的遥感反射率曲线,筛选具有显著光谱特征的波段,并以OIF指数衡量不同波段组合获取水体组分信息的能力,以此构建与实测叶绿素a浓度相关性较高的波段组合。结果表明珠海一号OHS-2A星影像的14,16和19波段所构建的三波段模型[R_rs(700 nm)-1-R_rs(670 nm)-1]×R_rs(746 nm)在巢湖的叶绿素a浓度反演中取得了较高的精度,相对误差和均方根误差分别为19.97%和10.85 mg·m-3。由模型反演巢湖2019年5月10日的叶绿素a浓度空间分布图可知,叶绿素a浓度自东向西呈上升趋势,全湖南部和东北部的叶绿素a浓度较低,西巢湖的北部叶绿素a浓度最高。西巢湖的整体叶绿素a浓度是全湖最高的,尤其是其北部水域,水质情况较差,已经出现了一定面积的水华,其主要原因在于该地区紧邻合肥市,人类活动强烈,污水废水排放量大。珠海一号高光谱卫星对于内陆湖泊的水质反演具有一定的优势,但也存在着数据处理困难,波段利用率低,反演模型普适性差等局限,今后仍需借助珠海一号高光谱数据开展更多的湖泊遥感研究,不断提出高光谱遥感影像处理的新方法,提高反演模型的精度与普适性,充分挖掘数据源的潜力,使其更好地服务于水质的遥感监测工作。     

富营养化水体环境中COD浓度遥感监测系统设计

对富营养化水体环境中COD浓度进行遥感监测,可以预防富营养化水体环境中COD浓度增加,提高水体水质,增加水循环次数,减少水体中有机物的污染。当前富营养化水体环境中COD浓度遥感监测系统设计方法,以Modis遥感影像数据为原理,依据富营养化水体环境中COD浓度的特征提取结果,对富营养化水体环境中COD浓度进行遥感监测,没有具体对遥感监测系统进行详细地设计,无法获取富营养化水体环境中COD浓度高精度的遥感监测信息,存在遥感监测结果偏差大的问题。提出了一种基于Zigbee的富营养化水体环境中COD浓度遥感监测系统设计方法。该方法先对Zigbee的富营养化水体环境中COD浓度遥感监测系统进行硬件设计,采用IMF对富营养化水体环境中COD浓度进行特征提取,以特征提取结果为基础,依据COD浓度指数时间序列实现富营养化水体环境中COD浓度遥感监测,最后利用Retinex法对COD浓度遥感监测的图像进行处理,完成对富营养化水体环境中COD浓度的遥感监测。仿真实验结果证明,所提系统设计方法可以精确地对富营养化水体环境中COD浓度进行安全快速的遥感监测。     

基于环境一号卫星超光谱数据的多元回归克里格模型反演湖泊总氮浓度的研究

水体中总氮含量是表征湖泊水质的主要指标,利用遥感技术对其动态定量监测可以及时掌握湖泊污染状况.文章以巢湖为例,利用HJ-1A卫星HSI超光谱遥感数据,通过分析总氮与叶绿素a、悬浮物的相关性,采用回归克里格方法建立总氮浓度的定量反演模型,实现了对巢湖水体总氮浓度的反演.结果显示,波段B72,B79和B97的多元线性组合与总氮浓度的相关系数R2为0.76,而利用多元回归克里格模型,相关系数R2提高到0.83.通过使用这种对常规回归模型残差优化的方法,能有效提高反演的精度,为建立通用的湖泊总氮浓度定量反演模型提供了有益的探索.     

植被氮素浓度高光谱遥感反演研究进展

氮素是植被进行生命活动的必需元素,它在蛋白质、核酸、叶绿素和酶等物质的生物合成中起重要作用,并在植被的光合作用中起到关键作用.植被氮素浓度高光谱遥感反演技术是自20世纪70年代以来的研究热点.近年来随着高光谱遥感技术的发展,可将光谱波段在某一光谱区域进行细分的优势,为与植被氮素相关的光谱特性研究提供了有力的技术手段.结合近几年主要地理科学文献上发表的植被氮素浓度高光谱遥感监测的最新研究成果,介绍了植被氮素浓度高光谱遥感监测的原理及相关问题.从植被氮光谱指数、叶绿素指数的植被氮含量反演、回归模型和反演植被氮浓度影响因素的消除方面,详细介绍了植被氮素浓度高光谱遥感反演这四个方面的主要技术方法,总结分析了研究结论,并讨论了研究发展趋势.     

基于GOCI影像分类的太湖水体叶绿素a浓度日变化分析

叶绿素a浓度(Chlorophyll-a:Chl-a)是内陆水体重要的水质参数之一,遥感数据为其提供了大范围、多时相的监测信息,然而由于内陆湖泊水色要素复杂的光学性质及较大的时空差异,传统的遥感影像及单一的Chl-a反演模型在应用中存在着局限性。因此本研究以太湖为研究区,时间分辨率1小时的静止海洋水色卫星Geostationary Ocean Color Imager(GOCI)为数据源,在基于层次聚类法实现归一化实测光谱反射率分类的基础上,利用光谱角测距匹配实现2012年5月6日(08:16—15:16)8景GOCI太湖影像的水体分类;并针对不同水体类型分别建立基于GOCI影像的Chl-a反演模型,实现不同类型水体的Chl-a浓度反演。结果表明,太湖水体光谱可分为四类,类型1光谱体现出漂浮藻类的特征,可将其作为蓝藻水华的判定依据;类型2—4体现的特征分别为水体含有较高Chl-a浓度、较高悬浮物浓度及相对较低Chl-a较低悬浮物浓度;并且类型2—4与分类前相比,其分类模型估算的Chl-a浓度误差均得到了不同程度的提高,平均相对误差分别降低了7%,12.3%和15.9%;此外,GOCI影像反演结果不仅可以很好地反映Ch卜a浓度的空间分布状况,也能反映出太湖Chl-a浓度的日变化差异及规律,表现出了其在富营养化污染动态监测及预警中的应用潜力。该方法在GOCI影像中的应用,在提高Chl-a浓度反演精度的同时也提高了模型在实际应用中的适用性,为日后太湖水体不同时刻Chl-a浓度的精确估算提供了基础。     

Equilibrium surface segregation of dissolved nonmetal atoms on iron(100) faces

At elevated temperatures equilibria of surface segregation X (dissolved) = X (adsorbed) have been studied for the nonmetal atoms X = C, N and S. Iron single crystals with (100)orientation have been doped with different concentrations of solute atoms (in the range about 10–100 wt ppm). The samples were introduced into the UHV chamber, cleaned and then heated to temperatures in the α-solid solution range. The surface concentration of the segregated nonmetal atoms was observed by AES for different bulk concentrations in dependence of the temperature. The LEED pattern was also observed during segregation equilibrium at temperatures up to about 750° C. The LEED patterns indicate a c(2 × 2) structure for carbon and nitrogen as well as for sulfur. The temperature dependence of the surface concentration for carbon on Fe(100) can be described by a Langmuir-McLean equation, an average segregation enthalpy of ?85 kJ/mol°C is obtained. Since N₂ desorption occurs the nitrogen segregation is in virtual equilibrium only at temperatures <500°C. The equilibrium surface concentration of sulfur on α-iron is virtually independent of the solute concentration and the temperature: there is always a saturated layer of sulfur on the (100) faces, even at small bulk concentrations. Since the thermodynamic activity of the nonmetal atoms is well defined in the segregation studies (except nitrogen at higher temperatures) , the results can be correlated with studies in gas atmospheres at atmospheric pressure. The relations to the kinetics of the carburization and the nitrogenation of iron are discussed and the influence of sulfur on these reactions.     

On the hydrogen etching mechanism in plasma nitriding of metals

Iron alloys and aluminum were nitrogen implanted in a controlled oxygen atmosphere and the role of hydrogen on the surface etching mechanisms studied. The surface composition was analyzed by in situ photoemission electron spectroscopy (XPS). In iron alloys, hydrogen strongly etches oxygen, improving nitrogen retention on the surface. On the other hand, hydrogen removes nitrogen from aluminum surfaces, with a deleterious effect on the nitriding effectiveness. The oxygen removal in iron alloys is associated with the catalytic effect of electrons in d-orbitals and the nitrogen removal in aluminum is associated with a steric effect.     

M?ssbauer study of iron nitride films produced by pulsed laser deposition

Iron nitride films were produced by pulsed laser deposition of Fe onto an Al substrate in an N₂ atmosphere and their M?ssbauer spectra and powder X-ray diffraction patterns were measured. The nitrogen content of the iron nitride films varied depending on the N₂ pressure. Under high N₂ pressures, γ”-FeN (ZnS structure) and γ’”-FeN (NaCl structure) were obtained. The yields of these two phases could be controlled by varying the Al substrate temperature. γ”-FeN and γ’”-FeN were found to be paramagnetic and antiferromagnetic, respectively, at 5?K.     

A review on iron chelators as potential therapeutic agents for the treatment of Alzheimer’s and Parkinson’s diseases

Iron plays a vital role in several cellular functions due to its unique physiochemical properties. Iron concentration increases in the brain with age due to multiple factors. Excessive amount of iron can lead to formation of reactive oxygen species. Neurodegenerative disorders are characterized by iron supplemented increase in oxidative stress and cellular damage. There is an urgent need of novel therapies which should not only provide symptomatic relief but also be able to modulate iron accumulation in the brain. Therefore, the development of novel iron chelators as neuroprotective agents for the treatment of neurodegeneration is an emerging trend. Several iron chelators including 8-hydroxyquinoline derivatives, dopaminergic agonists and natural products are under preclinical and clinical investigations for the treatment of neurodegenerative disorders.

     

Mixing characterization of mechanically milled Fe75Si15M10 powders using Mössbauer spectroscopy

Iron nitrides are attractive as they show excellent magnetic properties which can be utilized as recording and permanent magnetic materials for potential applications. Due to the high saturation magnetization and chemical stability, γ ^′-Fe₄N compound is widely investigated as a promising high density magnetic recording material. γ ^′-Fe₄N particles were synthesized by conventional gaseous nitriding in a heated atmosphere containing ammonia as a source of nitrogen. X-ray diffraction, ⁵⁷Fe Mössbauer spectroscopy, vibrating sample magnetometer, scanning electron microscopy and transmission electron microscopy are used for the characterization of the as prepared sample.     

Iron films deposited on porous alumina substrates

Iron films were deposited on porous alumina substrates using an arc plasma gun. The pore sizes (120 – 250 nm) of the substrates were controlled by changing the temperature during the anodic oxidation of aluminum plates. Iron atoms penetrated into pores with diameters of less than 160 nm, and were stabilized by forming γ-Fe, whereas α-Fe was produced as a flat plane covering the pores. For porous alumina substrates with pore sizes larger than 200 nm, the deposited iron films contained many defects and the resulting α-Fe had smaller hyperfine magnetic fields. In addition, only a very small amount of γ-Fe was obtained. It was demonstrated that the composition and structure of an iron film can be affected by the surface morphology of the porous alumina substrate on which the film is grown.     

Mössbauer study of braunite

Braunite mineral from Triodi manganese deposits (India) has been studied by Mössbauer spectroscopy. Room temperature Mössbauer spectra show a well resolved quadrupole splitting which is attributed to the substitution of iron in Mn (2) site. Emergence of another doublet at liquid nitrogen temperature has been attributed to the location of small quantities of iron in Mn (4) site. Iron is in Fe III and high spin state. At 4.2 K the internal magnetic field is 415 kOe.     

An in situ Mössbauer study on the metal-support interaction of supported iron catalysts for CO hydrogenation

Iron supported catalysts were investigated by in situ Mössbauer spectroscopy. Results showed that MSI can be vell Interpreted as a combination of the dispersion effect and the chemical interaction effect.     

Nitridation of iron by the mixing technology with laser and plasma beams

Iron nitride (Fe_xN) is obtained by the mixing technology with laser and plasma beams coaxially on the surface of pure iron in atmosphere. In this technology, laser and plasma provide heat source and nitrogen ion source, respectively, easily to nitriding the sample. The feasibility of the method is analyzed in theory. Small-angle X-ray diffraction measurements reveal formation of iron nitride in the as-treated sample, and scanning tunneling microscope measurements describe the surface profiles of the irradiated area, at different laser energy densities or different scanning velocities.     

基于多光谱图像分析的温室黄瓜叶片营养元素检测与诊断

采用CCD照相机加滤光片的方法,进行了基于多光谱图像分析的温室黄瓜叶片营养元素检测与诊断研究。对近红外光波段的叶片图像分别采用遗传算法和分水岭算法进行阈值选取,对两种算法二值化的效果进行对比分析,结果表明采用分水岭方法分割的图像,边界清晰,噪音小,与原图像更接近,背景和叶片分离的效果更好。NDVI与叶面积、叶片含氮量之间有明显的线性关系,R~2分别为:0.820 9和0.701 7。GNDVI与叶面积、叶片的含氮量之间也有较高的线性关系,R~2分别为:0.762 5和0.676 2。RVI与叶面积之间有明显的线性相关关系,R~2为0.857 7,但与叶片的含氮量之间则包含了非线性成分,R~2为0.598 8。以上结果表明,CCD照相机加滤光片可以作为一种作物含氮量信息的快速诊断方法。