排序方式: 共有3条查询结果,搜索用时 0 毫秒
1
1.
Irradiation of organic molecules by mineral radioactivity is a feasible alternative to cosmic irradiation to precipitate solid organic carbon-rich matter on the early Earth. Radioactive (uranium- and thorium-rich) minerals have been concentrated at the Earth's surface, and accumulated accretionary coatings of carbon due to irradiation, since early Archean times. The organic accretion process could have occurred at the surface or in the sub-surface, and is independent of a terrestrial or extraterrestrial source for the carbon. 相似文献
2.
Effects of rare earth elements on growth rate,lipids, fatty acids and pigments in microalgae
下载免费PDF全文
![点击此处可从《Phycological Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Franz Goecke Milada Vítová Jaromír Lukavský Linda Nedbalová Tomáš Řezanka Vilém Zachleder 《Phycological Research》2017,65(3):226-234
The extensive exploitation of rare earth elements (REEs), particularly in electronic technologies and agriculture has concomitantly raised the environmental load. Their resulting effects on primary producers such as microalgae are, however, poorly understood. We have studied these effects on two microalgae of biotechnological interest. The yellow‐green alga Trachydiscus minutus (Eustigmatophyceae, Ochrophyta), and the green alga Parachlorella kessleri (Trebouxiophyceae, Chlorophyta) were cultivated in mineral medium supplemented with 10 μmol L?1 chlorides of REEs: cerium, gadolinium, lanthanum, lutetium, praseodymium, scandium, and with monazite, which is a mineral rich in those elements. We observed growth rates at different mean light intensities (20, 50, 150 and 300 μmol m?2 s?1). The high growth rate of P. kessleri was not affected by the presence of any lanthanide, and decreased proportionally with light intensity (from 0.2 to 0.04 doublings per hour). In contrast, the growth rate of T. minutus was about three times lower compared with P. kessleri, with an optimum at 50 μmol m?2 s?1 and decreased at higher or lower light intensities. In the presence of Ce3+, La3+ and Sc3+, the growth rate markedly increased to a value that corresponded to the growth rate in P. kessleri at the same light intensity. The composition and content of pigments and lipids were followed at the optimum light intensity for both species. The lipid content (percentage of dry weight) varied only slightly in the presence of individual rare earths. There was, however, an increase in saturated fatty acids at the expense of polyunsaturated fatty acids. The effect of REEs on pigments was variable: the presence of Ce3+, Gd3+, La3+ and Sc3+ caused an increase in the concentrations of major pigments such as lutein, violaxanthin, β‐carotene or chlorophylls, while Pr3+ and Lu3+ reduced them. 相似文献
3.
1