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[ Objective]The present paper aimed to provide basic data and theoretical reference for the feasibility research and technological development of the replacement control of the relevant invasive plants by using Cynodon dactylon . [Method] Using assays with petri dishes and filter papers, the effects of the aqueous extracts from leaves of four invasive plants ( Argeratina adenophora, Conyza Canadensis, Chmmolaena odoratum and Tithonia diversifolia) with different concentration ( 0 . 00, 0 . 2S, 0. SO, 1. 00 and 2. 00 g · L - l) on the germination rate, germination potential and allopathic effect index of Cynodon dynodon seeds were investigated and compared. [ Result] Aqueous extracts from leaves of four invasive plants had significant inhibitory effects on seed germination of Cynodon dynodon ; and the inhibitory effects increased with the corresponding concentrations. Moreover, at the low or medium concentrations (0.25 0.05 and 1.00 g·L-1), the four invasive plants showed significantly different inhibitory and allopathic effects on the seed germination of Cynodon dynodon; while at the high concentration ( 2.00 g·L-1), the most powerful inhibitory and allopathic effects arose from Chromolaena odoratum, but there was no significant differences among the other three plants. [ Conclusion] The four invasive plants had a strong inhibitory allopathic effect on Cynodon dynodon, and appropriate measures should be taken to avoid or alleviate these negative effects for the application of Cynodon dynodon in the replacement control and ecological restoration. [ABSTRACT FROM AUTHOR]

BACKGROUND: Simultaneous determination of thorium and potassium in geological samples can provide an important basis for exploration of radioactive mineral resources and evaluation of the natural radioactive ecological environment. The thorium in geological samples is usually digested by alkali fusion in traditional methods and determined by spectrophotometry. The traditional method is long, complex and not suitable for simultaneous determination of multiple elements. The potassium oxide in geological samples is digested by acid and generally determined by flame atomic absorption spectrometry, which requires diluting the solution with high concentration and has low detection efficiency. The determination of thorium and potassium oxide involves two different analytical methods and analytical instruments. OBJECTIVES:To establish an analytical method for simultaneous determination of thorium and potassium oxide in geological samples. METHODS:Chemical solvent which consists of nitric acid, hydrofluoric acid and perchloric acid, was identified according to the characteristics of the chemical composition of the geological samples. The geological samples were dissolved with this solvent and extracted with nitric acid. The content of thorium and potassium oxide in geological samples was measured by inductively coupled plasma-optical emission spectrometry at wavelengths of 401.913nm and 766.490nm, respectively by radial observation. RESULTS:The correlation coefficient of the calibration curve of thorium and potassium oxide was greater than 0.999 and the detection limit of this method was 0.69 μg/g and 0.008%, respectively. The measured value of the standard substance was consistent with the identified value, and the absolute logarithmic error of the two values was less than 0.10. The relative standard deviation was less than 6% and the recovery ranged from 96% to 104%. CONCLUSIONS:This method meets the requirements of the testing quality management standard for geological and mineral laboratories. [ABSTRACT FROM AUTHOR]