A post-hoc extension to this work investigated the ratio of Ca:Mg,
at a fixed water hardness (400 mg CaCO3 L−1) and U concentration
(547 μg L−1 U; the EC50 value at 400 mg CaCO3 L−1) on the accumulation
and toxicity of U with C. demersum. The results (Table 6)
show that U accumulation and toxicity are about a factor of four
lower where the ratio of Ca:Mg was the highest (390:10).