质子诱发瞬发 γ 射线测定 C 和 N 同位素丰度

观测了低能质子在含Ｃ和Ｎ样品上引起的共振核反应。通过测定几种已知丰度富集物的γ射线产额进行体系刻度，可快速、准确地求出待测样品的丰度。测量范围：１３Ｃ为１％—９０％，１５Ｎ为０．０５％—５％。

Temporal and spatial distribution of virioplankton in large shallow freshwater lakes

Virioplankton dynamics at seven sample sites(from two freshwater lakes) with different trophic states were monitored over the period of a year.Water was sampled monthly from August 2004 to July 2005,and the abundances of viruses and bacteria were measured using direct epifluorescence microscopy counting.Results indicated that both natural and anthropogenic factors could influence the distribution of virioplankton.Temporally,viral abundance was significantly correlated to bacterial density and water temperature.Spatially,viral abundance was significantly correlated to trophic state.This in turn indicated that viral abundance was directly dependant on host abundance in eutrophic lakes,while trophic state and temperature could drive the distribution of virioplankton.The virus-bacteria ratio was significantly lower in less productive water-bodies.The result implied that the control of virioplankton on their hosts may change according to the host density.

氢同位素分馏效应校正

同位素分馏效应是影响氢同位素丰度准确测定的主要因素。采用系统校正法和分子泵压缩比校正系数法可以较好地解决分馏效应对氢同位素丰度准确测定产生的影响。系统校正法是用标准样品的标称值对测量系统进行误差修正得到系统误差校正系数k，然后通过C校=kC样测，通过对标准样品的测量给出，校正系数k=C标／C标测，用系统校正法校正分析待测样品的丰度值，需要使用气体同位素标准，而分析不同丰度的氢同位素气体样品，需要使用相应丰度值的气体同位素标准。因此氢同位素标准气体的获取以及在储存过程中保持标称值不变是需要考虑的问题。