Long-term effects of single potassium fertilization on 137Cs levels in plants and fungi in a boreal forest ecosystem

We examined the long-term effects of a single application of potassium (K) fertilizer (100 kg K ha(-1)) in 1992 on Cs-137 uptake in a forest ecosystem in central Sweden. Cs-137 activity concentrations were determined in three low-growing perennial shrubs, heather (Calluna vulgaris), lingonberry (Vaccinium vitis-idaea) and bilberry (Vaccinium myrtillus), and in four wild fungal species (Cortinarius semisanguineus, Lactarius rufus, Rozites caperata and Suillus variegatus). Uptake of Cs-137 by plants and fungi growing on K-fertilized plots 17 years after application of the K fertilizer was significantly lower than in corresponding species growing in a non-fertilized control area. The Cs-137 activity concentration was 21 -58% lower in fungal sporocarps and 40-61% lower in plants in the K-fertilized area compared with the control. Over the study period, this decrease in Cs-137 activity concentration was more consistent in plants than in fungi, although the effect was statistically significant and strongly pronounced in all species. The effect of K fertilization in reducing Cs-137 activity concentration in fungi and plants decreased over time but was still significant in 2009,17 years after fertilization. This suggests that application of K fertilizer to forests is an appropriate and effective long-term measure to decrease radiocaesium accumulation in plants and fungi. (C) 2010 Elsevier Ltd. All rights reserved.