Table 1. The concentration of cations (Na⁺, Mg²⁺ and Ca²⁺) in different environmental samples (average global river water⁴⁰; seawater from Imari Bay, Japan¹⁶; FDNPP groundwater¹⁵; and Magnox waste storage tank liquor from Sellafield, UK³).

Ion	Concentration (mmol/L)
	Seawater	River water	Fukushima groundwater	Sellafield tank liquor
Na+	450	0.31	2.1	6.6
Mg2+	52	0.15	0.86	0.39
Ca2+	9.4	0.37	0.70	0.27