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Subgroups: (a) shallow groundwater—A′, samples from the northeastern areas; B′, samples from the southern mountain areas; and C′, samples from the western areas; (b) deep groundwater—A, samples from the northeastern areas; B, samples from the southern mountain areas; C, samples from the western areas; and D, samples from the Emei high platform areas. Symbols: triangle, shallow groundwater; circle, deep groundwater.
