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981.
982.
983.
The contents of Pb, Cd, Cr, As, and Hg was investigated in the neighboring areas of a lead smelting enterprise and the metals contamination of soil was evaluated with the methodologies of the single factor index and Nemerow integrated index. It is found that the content of heavy metals in the neighboring areas has no obvious difference from the reference points. And the soil contamination of heavy metals varies by elements, the contamination index follows the pollution order: Cd〉Hg〉Cr〉As〉Pb. The pollution degree of Cd is at high level and Hg at low level, but Cr and As reached the warning level. Therefore, the lead smelting enterprises should not only control lead but also other heavy metals as Cd. 相似文献
984.
Late Paleozoic retrograded eclogites from within the northern margin of the North China Craton: Evidence for subduction of the Paleo-Asian ocean 总被引:4,自引:1,他引:3
Retrograded eclogites from the central part of the northern margin of the North China Craton, Hebei Province, China occur as separate tectonic lenses or boundins within garnet–biotite–plagioclase gneisses of the Paleoproterozoic Hongqiyingzi Complex characterized by amphibolite facies paragneisses. The petrographic features and mineralogical compositions represent three main metamorphic stages: (1) the peak eclogite facies stage (P > 1.40–1.50 GPa, T = 680–730 °C), (2) the granulite facies stage and (3) the amphibolite facies stage (P = 0.67–0.81 GPa, T = 530–610 °C) formed during decompression. The major and trace element and Sm–Nd isotopic data suggest that most of the retrograded eclogite samples had protoliths of tholeiitic oceanic crust with geochemical characteristics of mid-ocean ridge basalt (MORB) or island arc tholeiite (IAT) environment, and were contaminated by crustal components during subsequent subduction. Zircon SHRIMP isotopic dating of two different textural varieties of retrograded eclogite defines a weighted mean age of 325 Ma, which is interpreted as the peak metamorphic age of the eclogites and reflects the occurrence of eclogite facies metamorphism related to subduction of Paleo-Asian Oceanic crust beneath the North China Craton during the Late Paleozoic. Finally, we show that the retrograded eclogite from Hebei Province is not related to the Baimashi retrograded eclogite at the northern foot of the Heng Mountains, approximately, 300 km to the southwest. 相似文献
985.
Nano-sized zinc oxide (nZnO) particles are one kind of the most commonly used metal oxide nanoparticles (NPs). This study compared the cytotoxic and embryotoxic effects of three increasing sized ZnO particles (? 30 nm, 80-150 nm and 2 μm) in the flounder gill (FG) cells and zebrafish embryos, and analyzed the contribution of size, agglomeration and released Zn2+ to the toxic effects. All the tested ZnO particles were found to be highly toxic to both FG cells and zebrafish embryos. They induced growth inhibition, LDH release, morphological changes and apoptosis in FG cells in a concentration-, size- and time-dependent manner. Moreover, the release of LDH from the exposed FG cells into the medium occurred before the observable morphological changes happened. The ultrasonication treatment and addition of serum favored the dispersion of ZnO particles and alleviated the agglomeration, thus significantly increased the corresponding cytotoxicity. The released Zn2+ ions from ZnO particles into the extracellular medium only partially contributed to the cytotoxicity. All the three sizes of ZnO particles tested induced developmental malformations, decrease of hatching rates and lethality in zebrafish embryos, but size- and concentration- dependent toxic effects were not so obvious as in FG cells possibly due to the easy aggregation of ZnO particles in freshwater. In conclusion, both FG cells and zebrafish embryos are sensitive bioassay systems for safety assessment of ZnO particles and the environmental release of ZnO particles should be closely monitored as far as the safety of aquatic organisms is concerned. 相似文献
986.
中国近百年气候变化的自然原因讨论 总被引:20,自引:9,他引:11
本文分析了近百年来中国气候变化的概况,讨论了影响中国气候变化的自然因素大气环流和海温,此外还叙述了有关大气气溶胶、大气污染等人为因素对中国气候变化影响的研究进展。结果指出:北极涛动、东亚季风这两个大气环流因素对中国气候异常变化有至关重要的作用,同时El Nino和La Nina事件和太平洋年代际振荡的海表温度异常变化也对中国气候产生了一定的影响。但是有关大气气溶胶和大气污染物对中国气候的影响作用还有待于进一步研究,自然原因仍然是影响中国气候变化的主要原因。 相似文献
987.
冲绳海槽是因菲律宾海板块俯冲于欧亚板块之下,在陆壳上发育起来的一个初始的弧后盆地,是研究弧后扩张作用早期盆地演化、岩浆作用和壳幔过程的天然实验室.尽管迄今对冲绳海槽已经做了大量的调查研究工作,但仍存在一些颇有争议或亟待解决的科学问题,如:冲绳海槽酸性浮岩与基性玄武岩之间的成因联系,冲绳海槽不同区段构造背景对岩浆作用的控... 相似文献
988.
989.
Dong Chenfan Wu Haiyan Peng Jixing Guo Mengmeng Zhai Yuxiu Tan Zhijun 《中国海洋湖沼学报》2022,40(6):2267-2276
Journal of Oceanology and Limnology - Understanding the risk factors associated with shellfish consumption is a relevant public health concern because of the potential adverse effects of paralytic... 相似文献
990.
黑龙江林口西北楞石墨矿位于佳木斯—兴凯(地块)Fe-Au-P-石墨-矽线石成矿带(Ⅲ-53)中部,为一沉积变质超大型晶质石墨矿床。赋矿层位为上元古界兴东岩群大盘道岩组下段(Pt3dp1.),构造较为简单,矿带延展长度约为9.5 km,共圈定石墨矿带6条、石墨矿体73条。矿床地质特征及地球物理特征明显,极具代表性,总结研究其地质特征及成矿规律,对黑龙江东部佳木斯隆起兴东岩群大盘道岩组的区域矿产勘查工作具有一定的参考价值。 相似文献