The clay mineralogy rather than the clay content determines radiocaesium adsorption in soils on a global scale
<p>The transfer of radiocaesium (<span class="inline-formula"><sup>137</sup></span>Cs) from soil to crops is the main long-term radiation risk after nuclear accidents. The prevailing concept is that <span class="inline-formula"><sup>137&l...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-04-01
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| Series: | SOIL |
| Online Access: | https://soil.copernicus.org/articles/11/339/2025/soil-11-339-2025.pdf |
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| Summary: | <p>The transfer of radiocaesium (<span class="inline-formula"><sup>137</sup></span>Cs) from soil to crops is the main long-term radiation risk after nuclear accidents. The prevailing concept is that <span class="inline-formula"><sup>137</sup></span>Cs sorption in soil – and, hence, its bioavailability – is controlled by soil clay content (0–2 <span class="inline-formula">µ</span>m). This study tested this assumption using 24 soils collected worldwide. The radiocaesium interception potential (RIP), i.e., <span class="inline-formula"><sup>137</sup></span>Cs adsorption, was measured for the bulk soils and for their clay and silt fractions. The RIP varied by a factor of 438 among soils and was <i>unrelated</i> to the clay content (<span class="inline-formula"><i>p</i></span> <span class="inline-formula">></span> 0.05). The RIP in the clay fractions was lowest for young volcanic soils with allophane and mica and for highly weathered tropical soils with kaolinite. In contrast, RIP values about 2 orders of magnitude higher were found in intermediate-weathered temperate soils dominated by illite. Soil RIP was, hence, related to soil illite content (R<span class="inline-formula"><sup>2</sup>=</span> 0.50; <span class="inline-formula"><i>p</i></span> <span class="inline-formula"><</span> 0.001). A significant fraction of soil RIP originated from clay minerals embedded in the silt fraction. The sum of RIP in clay and silt fractions overestimated the soil RIP by, on average, a factor of 2, indicating that the isolation of clay opens selective <span class="inline-formula"><sup>137</sup></span>Cs sorption sites inaccessible in intact soils. Soil mineralogy, not just clay content, governs soil RIP. In terms of validity, existing <span class="inline-formula"><sup>137</sup></span>Cs bioavailability models require recalibration for use on a global scale.</p> |
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| ISSN: | 2199-3971 2199-398X |