[Soil amelioration of different vegetation types in saline-alkali land of the Yellow River Delta, China]. / 黄河三角洲盐碱地不同植被模式的土壤改良效应.

Yellow River Delta is an important distribution area of coastal saline-alkali land in China. Revegetation is the main technology for ecological restoration during saline-alkali land amelioration. To explore the effects of different vegetation types on soil improvement in saline-alkali land and get the suitable model in the Yellow River Delta, four tree-grass compound models, Salix americana+Distichlis spicata, S. matsudana+D. spicata, Tamarix chinensis+Medicago sativa, and Fraxinus chinensis+T. chinensis+M. sativa, were set up, with pure S. americana forest as the control. Twenty indicators, including soil moisture physical parameters, saline-alkali content, soil nutrient contents, and microorganism quantity etc. were measured. Principal component analysis, cluster analysis and fuzzy mathematics were used to evaluate soil modification effect of different vegetation combinations. The results showed that all compound models significantly improved soil physical and che-mical properties in coastal saline-alkali land by increasing soil porosity, soil water storage, soil organic matter content, available nutrient content and soil microorganism quantity and reducing soil density. Among all the models, the tree-shrub-grass mixed model of F. chinensis+T. chinensis+M. sativa was the most effective in inhibiting salt and alkali stress and increasing soil nutrients and microorganism abundance, whereas the tree-grass mixed model of S. matsudana+D. spicata was the most effective in improving soil water physical properties. The combined effects of different vegetation patterns on soil amelioration in coastal saline-alkali land of the Yellow River Delta were arranged in order of F. chinensis+T. chinensis+M. sativa> S. matsudana+D. spicata> S. americana+D. spicata> T. chinensis+M. sativa.

[Effects of multiple times of topdressing nitrogen application under equal level on utilization and distribution characteristics of 15N and 13C in winter jujube]. / 等量分次施氮对冬枣15N和13Cåˆ©ç”¨ä¸Žåˆ†é ç‰¹æ€§çš„å½±å“.

We explored the effects of multiple times of topdressing nitrogen application under equal level on the characteristics of absorption, utilization, accumulation, and distribution of 15N and 13C in four-year-old potted winter jujube during fruit developmental periods using the stable isotope tra-cer technology. The results showed that with the increases of nitrogen application times, the 15N derived from fertilizer (Ndff) in each organ significantly increased at the fruit maturity. The distribution rates of 15N in reproductive organ (fruit) and vegetative organs (leaf, deciduous spur, new branch, and fine root) were highest under four-time application, and lowest under one-time application. The opposite pattern was observed in storage organs (trunk, perennial branch, and coarse root). The 15N utilization rate under four-time application was 27.4% and 15.5% higher than one-time and two-time application, respectively. The more times N being applied, the more total N content and 15N absorption amount of plant. Soil 15N abundance and total N content continued to drop under one-time application and increased at the beginning and then declined with the time under two-time application. The relatively stable soil 15N abundance and total N content appeared in four-time application, which was significantly higher than those in the other treatments in later treatment stages. The chlorophyll content, leaf nitrogen content and photosynthetic rate displayed an order of four-time application > two-time application > one-time application during fruit white-mature period to fruit harvest period. The accumulation and distribution of 13C varied across different treatments. Increasing nitrogen application times would promote more 13C being transported to fruit and storage organs but decrease that in annual vegetative organs. Our findings indicated that four-time nitrogen application could enhance and optimize the accumulation and distribution of photosynthetic products by ensuring steady and adequate supply of nitrogen and improving the absorption and utilization of nitrogen during fruit development period, which facilitates the growth, yield and quality of winter jujube.

[Using atomic fluorescence spectrometry to study the spatial distribution of As and Hg in orchard soils].

Aqua regia digestion, double channels-atomic fluorescence spectrometry method was used to determine the concentrations of As and Hg in orchard soils of Qixia City - the main apple production area of Shandong province. Validate The detection limitation, accuracy and precision of the method were validated, the spatial distribution was analyzed, and the characteristics of As and Hg pollution in Qixia orchard soils were assessed. The results showed that the range of As concentration in Qixia soils is between 2.79 and 20.93 mg x kg(-1), the average concentration is 10.59 mg x kg(-1), the range of Hg concentration in Qixia soil is between 0.01 and 0.79 mg x kg(-1), the average concentration is 0.12 mg x kg(-1). The variation of As concentration in soils is small, whereas that of Hg concentration is large. Frequency distribution graphics of As and Hg showed that the concentration of As in soils is according with the normal distribution approximately and the concentrations are mostly between 7 and 15 mg x kg(-1), the concentration of Hg in soil isn't according with the normal distribution and the concentrations are mostly between 0.03 and 0.21 mg x kg(-1). The correlations between the concentrations of As or Hg in soils and the nutrient are not significant and there is no significant correlation even between As and Hg. Based on the environmental technical terms for green food production area, the As concentration in orchard soil of Qixia City is at clean level, but there are 4.76% of sample points with Hg pollution index exceeding 1, and this should be attracted the attention of the administrators.

[Study of arsenic concentration and distribution in shell sand of the shell ridge islands by hydride generation atomic fluorescence spectrometry].

The present paper determined the As concentration in shell sand of the shell ridge islands by hydride generation atomic fluorescence spectrometry, studied the distribution of As in shell sand of the shell ridge islands, analysed the correlations of As with other nutrient elements, and discussed the probably influencing factors affecting the As concentration and distribution in shell sand. The results showed that the range of the arsenic concentration in shell sand is between 0.78 and 8.76 mg x kg(-1), the average concentration is 3.11 mg x kg(-1), and this indicated that the As contamination of the shell ridge island is in clean level. The As concentration of the shell sand has a increasing trend followed by the increase with profile depth or the decrease with the particle size, and the difference in As concentrations in shell sand of different particle sizes reached the significant level (p < or = 0.05). The As concentration in shell sand has a very significant positive correlation with the concentrations of Cu, Zn and Mn as well as the TP and TK, whereas the correlations between As and TN or Fe are not significant. The pollutant of As in the shell sand mainly comes from the absorption and fixation by shell sand from the environment but not the accumulation of the shell organism during their growing up.