Radiation and Nuclear Safety Authority (STUK), Research and Environmental Surveillance, P.O. Box 14, FI-00881 Helsinki, Finland.
Sci Total Environ. 2012 Dec 15;441:194-208. doi: 10.1016/j.scitotenv.2012.09.045. Epub 2012 Nov 6.
Seasonal variations in foliar ¹³⁷Cs levels were examined in Norway spruce (Picea abies (L.) Karst.), and Scots pine (Pinus sylvestris L.) in western Finland. Our aim was to test the occurrence of seasonal variation in contents and concentrations of ¹³⁷Cs, potassium and carbon in needles. The study focused on analysing levels of total ¹³⁷Cs in the three youngest needle age classes and comparing them to the levels of potassium and carbon. Spruce and pine needles were collected from 50- and 65-year-old stands on 18 sampling occasions between April 1996 and February 1997. Phases of intensive growth, needle elongation and dormancy were apparent in the time series for the needle contents and activity concentration of ¹³⁷Cs, both of which varied according to needle age class and tree species. The sequence of phases with a temporal fluctuation of needle contents, activity concentrations of ¹³⁷Cs and concentrations of K and carbon varied occasionally, and the efficiency of their translocation revealed some differences in the dynamics of ¹³⁷Cs, K and carbon in spruce and pine. The data clearly showed that the needles' K contents responded strongly to changes in K demand from other parts of the tree due to seasonal changes and that these responses were stronger than the associated retranslocations of ¹³⁷Cs, particularly in Scots pine. During intensive growth, K was less mobile than ¹³⁷Cs in the needles. The uptake of ¹³⁷Cs by current-year needles is simultaneously affected by uptake from the soil via the roots and retranslocation from other internal sources, and both of these processes affect the observed transfer rates during the growth period. Our results provided information on the transfer rates and revealed differentiation of root uptake and retranslocation of ¹³⁷Cs in needles. The study can support dynamic modelling of atmospheric ¹³⁷Cs contamination in forests.
在芬兰西部，研究了挪威云杉（Picea abies（L.）Karst.）和欧洲赤松（Pinus sylvestris L.）叶片 ¹³⁷Cs 水平的季节性变化。我们的目的是检验 ¹³⁷Cs、钾和碳在针叶中的含量和浓度是否存在季节性变化。本研究重点分析了三个最年轻的针叶年龄组的总 ¹³⁷Cs 水平，并将其与钾和碳的水平进行了比较。1996 年 4 月至 1997 年 2 月，在 50 年和 65 年生的林分中，采集了云杉和松树的针叶，共采集了 18 次。在时间序列中，针叶的含量和 ¹³⁷Cs 的活性浓度，都表现出了明显的生长高峰期、针叶伸长期和休眠期，这些阶段随针叶年龄组和树种而变化。各阶段的顺序随时间波动，针叶的含量、 ¹³⁷Cs 的活性浓度以及 K 和碳的浓度也随之波动，偶尔也会出现差异，其再转移效率也揭示了 ¹³⁷Cs、K 和碳在云杉和松树中的动态存在一些差异。数据清楚地表明，由于季节性变化，针叶中的 K 含量对来自树木其他部位的 K 需求变化反应强烈，这种反应比 ¹³⁷Cs 的相关再转移更为强烈，尤其是在欧洲赤松中。在旺盛生长期，K 在针叶中的移动性比 ¹³⁷Cs 差。当年生针叶对 ¹³⁷Cs 的吸收同时受到根系从土壤中吸收和其他内部来源再转移的影响，这两个过程都会影响生长期间观察到的转移率。我们的研究结果提供了转移率的信息，并揭示了根吸收和针叶中 ¹³⁷Cs 再转移的差异。本研究可为森林中大气 ¹³⁷Cs 污染的动态建模提供支持。
