Spatial and Temporal Variability of Soil Organic Matters in Se-rich Areas of Hainan Island in Recent 30 Years

[Objectives] The aim was to reveal the distribution of soil organic matter content in cultivated land in the Se-rich areas of Hainan in 1980and 2010, so as to provide reference for the study on the evolution of soil organic matter content.[Methods] With the combination of field investigation with indoor analysis, the characteristics of organic matter content in the Se-rich areas of Hainan in 1980 and 2010 was revealed by means of spatial analysis, and the differences were analyzed.[Results] In the last 30 years, the proportion of 20-30 g/kg of soil organic matter content in the Se-rich areas of Hainan was reduced, but the content of soil organic matter in the area generally increased. The average value of the content of organic matter in the area was increased from 25.3 g/kg in the 1980s to 28.1 g/kg, but its spatial distribution was uneven.[Conclusions] The farmers should be guided to change the fertilization structure, and attention should be paid to the application of organic fertilizer, so as to improve the soil organic matter content.

引水式水电站变顶高尾水洞水力特性和体型优化

考虑引水式水电站常用的有压尾水洞和变顶高尾水洞两类布置型式,采用基于特征线法的有压管道瞬变流分析模型和适用于明满流过渡过程分析的改进狭缝法模型,分别分析系统的过渡过程特性和尾水洞体型参数的敏感性,研究不同的尾水洞型式下尾水系统的水力特性,进一步揭示了变顶高尾水洞的底宽、洞高和顶坡对尾水管进口最小内水压力的影响规律。结果表明,与增大面积的有压尾水洞比较,变顶高尾水洞是一种可行的布置型式,可有效提高尾水管进口的最小内水压力且水锤过程衰减较快;合理增大变顶高尾水洞底宽、洞高或顶坡均可不同程度地改善尾水管进口最小内水压力,其中顶坡的影响相对明显,为体型优化设计提供了参考依据。