Abstract
Batch sorption experiments were conducted to evaluate the
sorption behaviour of iodide and the microbial impact on
iodide sorption in the surface moss, subsurface peat,
gyttja, and clay layers of a nutrient-poor boreal bog.
The batch distribution coefficient (Kd) values of iodide
decreased as a function of sampling depth. The highest Kd
values, 4800 L/Kg dry weight (DW) (geometric mean), were
observed in the fresh surface moss and the lowest in the
bottom clay (geometric mean 90 mL/g DW). In the surface
moss, peat and gyttja layers, which have a high organic
matter content (on average 97%), maximum sorption was
observed at a pH between ~4 and 5 and in the clay layer
at pH 2. The Kd values were significantly lower in
sterilized samples, being 20-fold lower than the values
found for the unsterilized samples. In addition, the
recolonization of sterilized samples with a microbial
population from the fresh samples restored the sorption
capacity of surface moss, peat and gyttja samples,
indicating that the decrease in the sorption was due to
the destruction of microbes and supporting the hypothesis
that microbes are necessary for the incorporation of
iodide into the organic matter. Anoxic conditions reduced
the sorption of iodide in fresh, untreated samples,
similarly to the effect of sterilization, which supports
the hypothesis that iodide is oxidized into I2/HIO before
incorporation into the organic matter. Furthermore, the
Kd values positively correlated with peroxidase activity
in surface moss, subsurface peat and gyttja layers at
+20°C, and with the bacterial cell counts obtained from
plate count agar at +4°C. Our results demonstrate the
importance of viable microbes for the sorption of iodide
in the bog environment, having a high organic matter
content and a low pH.
Original language | English |
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Pages (from-to) | 110-122 |
Journal | Journal of Environmental Radioactivity |
Volume | 143 |
DOIs | |
Publication status | Published - 2015 |
MoE publication type | A1 Journal article-refereed |
Keywords
- sorption
- radioiodides
- peat
- microbes
- bacteria
- radionuclides