Radiocaesium accumulation in stemwood: integrated approach at the scale of forest stands for contaminated Scots pine in Belarus

Twenty years after the Chernobyl accident, root uptake from the surface layers of contaminated forest soils plays a major role in radiocaesium ((137)Cs) transfer to the trees and accumulation in perennial compartments, including stemwood. Trustworthy long-term predictions (modelling) of stemwood contamination with (137)Cs should accordingly be based on a reliable picture of this source-sink relationship. Considering the complexity of the processes involved in (137)Cs cycling in forest stands, elementary ratios like transfer factors (TF) were shown to be not very relevant for that purpose. At the tree level, alternatives like the wood immobilisation potential (WIP) have therefore been proposed in order to quantify the current net (137)Cs accumulation in stemwood. Our objective was here to compare WIP values determined for a series of contaminated forest stands in Belarus with the corresponding pools of (137)Cs available in the soil for root uptake. The comparison reveals that both indices are quite proportional, whatever the forest ecosystem features. This corroborates the relevancy of WIP as an indicator of the current (137)Cs root uptake by the trees, which could accordingly help to improve the existing models of (137)Cs cycling and the long-term management of contaminated forest ecosystems.     

根分泌物与微生物对污染土壤重金属活性的影响

研究了铜富集植物海州香薷(Elsholtziasplendens)和鸭跖草(Commelinacommunis)根分泌物,以及假单胞菌(P.aeruginosaZD4-3)和白腐真菌(P.Chrysosprim)对污染土壤重金属活性的影响.结果表明,海州香薷和鸭跖草根分泌物对污染土壤中Cu有一定的活化能力,不同处理间差异不大,鸭跖草根分泌物对Cu的活化能力大于海州香薷.不同处理根分泌物中有机酸种类或含量有所差异,但主要以草酸和出峰时间为6.5min左右的未知有机酸为主.假单胞菌对污染土壤Cu、Pb和Zn有很强的活化作用;白腐真菌对Cu、Zn有活化作用,对Pb则表现为固定作用,海州香薷根分泌物降低了供试假单胞菌对重金属的活化效果,但增加了白腐真菌对重金属的活化效果.