Fig. 3: Statistical analyses on groundwater δ18OPO4 values and redox-sensitive components in the different zones. | Communications Earth & Environment

Fig. 3: Statistical analyses on groundwater δ18OPO4 values and redox-sensitive components in the different zones.

From: Microbial cycling contributes to the release of dissolved inorganic phosphate into the groundwater of floodplain aquifers

Fig. 3

a Observed δ18O isotope values of groundwater (δ18OH2O). b Observed δ18O isotope values of dissolved inorganic phosphate in groundwater (δ18OPO4). c Calculated theoretical equilibrium δ18OPO4 values of dissolved inorganic phosphate after intensive intracellular microbial cycling (δ18OPO4 equ). d Difference between δ18OPO4 and δ18OPO4 equ values (Δ18OPO4) (Negative Δ18OPO4 values indicate that observed δ18OPO4 were isotopically lighter (i.e. more 18O-depleted) than the calculated equilibrium δ18OPO4 equ values). e Redox potential (Eh) of groundwater. f–h Concentrations of dissolved inorganic phosphate (PO4), ferrous iron (Fe(II)), and sulfide (S2-), respectively. The Zone I, II and III stand for the alluvial fan, the transition area and the flat plain, and are shown in blue, green, and red colours, respectively. Uppercase letters (A–C) indicate significant differences (p < 0.05) in measured variables among the three zones. N = 13, 16, and 16 in the alluvial fan, the transition area, and the flat plain, respectively.

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