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421.
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小麦产量的遥感动态预估研究──以山东禹城县为例 总被引:3,自引:0,他引:3
本文利用现代遥感信息、数理统计和回归分析方法,研究了禹城县试验区的小麦单产与卫星遥感信息(绿度)间的关系,并建立了小麦单产与绿度关系的预估模型;阐述了直接利用遥感宏观信息动态预估小麦产量的可行性和这一方法的应用前景。 相似文献
423.
全氟辛酸(perfluorooctanoic acid,PFOA)以其分布广泛性、生物蓄积性、生物毒性强而成为全球关注的一种新型持久性有机污染物.采用化学还原法制备钯掺二氧化钛(Pd-Ti O2)催化剂,利用XRD、FESEM、UV-vis DRS对催化剂进行表征,并考察其在365 nm紫外光照射下对PFOA的光催化降解效果.结果表明,化学还原的制备方法使Ti O2粒径减小、比表面积增大且对紫外光的吸收性能增大,但并不引起PFOA光催化效果的改变.而Pd掺杂后大大增强了PFOA的降解效果,反应7 h后溶液中氟离子浓度为6.62 mg·L-1,是Ti O2(P25)的7.3倍.投加俘获剂与通入氮气的实验证明,在PFOA的降解过程中·OH起重要作用,氧气的存在可促进PFOA的降解.采用UPLC-QTOF-MS对产物进行鉴定分析,PFOA的可能降解过程是经h+氧化后发生脱羧基反应,产生的全氟烷烃自由基(·CnF2n+1)被·OH氧化,脱氟生成短链全氟羧酸.Pd能作为电子(e-)捕获剂、加速e-向O2等电子受体的转移,从而缓解e-累积,提高对PFOA的降解效果. 相似文献
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425.
Effects of seed aerosols on the growth of secondary organic aerosols from the
photooxidation of toluene 总被引:3,自引:0,他引:3
Hydroxyl radical (.OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols (SOA). It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate. 相似文献
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Determination of ammonium on an integrated microchip with LED-induced fluorescence detection 总被引:1,自引:0,他引:1
A simply fabricated microfluidic device integrated with a fluorescence detection system has been developed for on-line determination of ammonium in aqueous samples. A 365-nm light-emitting diode (LED) as an excitation source and a minor band pass filter were mounted into a polydimethylsiloxane (PDMS)-based microchip for the purpose of miniaturization of the entire analytical system. The ammonium sample reacted with o-phthaldialdehyde (OPA) on-chip with sodium sulfite as reducing reagent to produce a fluorescent isoindole derivative, which can emit fluorescence signal at about 425 nm when excited at 365 nm. Effects of pH, flow rate of solutions, concentrations of OPA-reagent, phosphate and sulfite salt were investigated. The calibration curve of ammonium in the range of 0.018-1.8 μupg/mL showed a good linear relationship with R2 = 0.9985, and the detection limit was (S/N = 3) 3.6 × 10-4 μupg/mL. The relative standard deviation was 2.8% (n = 11) by calculating at 0.18 μupg/mL ammonium for repeated detection. The system was applied to determine the ammonium concentration in rain and river waters, even extent to other analytes fluorescence detection by the presented device. 相似文献
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It is important to screen strains that can decompose polycyclic aromatic hydrocarbons (PAHs) completely and rapidly with good adaptability for bioremediation in a local area. A bacterial strain JM2, which uses phenanthrene as its sole carbon source, was isolated from the active sewage sludge from a chemical plant in Jilin, China and identified as Pseudomonas based on 16S rDNA gene sequence analysis. Although the optimal growth conditions were determined to be pH 6.0 and 37℃, JM2 showed a broad pH and temperature profile. At pH 4.5 and 9.3, JM2 could degrade more than 40% of fluorene and phenanthrene (50 mg/L each) within 4 days. In addition, when the temperature was as low as 4℃, JM2 could degrade up to 24% fluorene and 12% phenanthrene. This showed the potential for JM2 to be applied in bioremediation over winter or in cold regions. Moreover, a nutrient augmentation study showed that adding formate into media could promote PAH degradation, while the supplement of salicylate had an inhibitive effect. Furthermore, in a metabolic pathway study, salicylate, phthalic acid, and 9-fluorenone were detected during the degradation of fluorene or phenanthrene. In conclusion, Pseudomonas sp. JM2 is a high performance strain in the degradation of fluorene and phenanthrene under extreme pH and temperature conditions. It might be useful in the bioremediation of PAHs. 相似文献