Sulfur forms in wetland soils with different flooding periods before and after flow-sediment regulation in the Yellow River Delta, China.

Dynamics of sulfur forms in the surface soils were investigated in the seasonal flooding wetlands (SEW), short-term flooding wetlands (SHW) and tidal flooding wetlands (TFW) affected by the flow-sediment regulation event in the Yellow River Delta from April to October of 2012. Our results demonstrated that the changing trend of inorganic sulfur (IS) and total sulfur (TS) contents were consistent. TS and IS contents in SEW and SHW soils showed a decrease and then an increase in the whole sampling dates. TS and IS showed significant differences between the TFW and SEW soils (p < 0.05). Water-soluble sulfate (H 2 O–S) contents exhibited a "decreasing then increasing" trend after the regulation (from July to October) in the SHW (7.86–19.23 mg/kg) and SEW (8.12–16.27 mg/kg) soils, whereas the TFW (21.35–30.58 mg/kg) soils showed an opposite trend after the regulation. The dynamic variations in absorbed sulfate (Absorbed-S) in the SHW (1.52–2.64 mg/kg), SEW (1.27–1.93 mg/kg) and TFW (2.06–2.89 mg/kg) soils before and after the regulation were consistent with H 2 O–S. Hydrochloric acid-soluble sulfur (HCl–S) contents in the SEW (4.13–6.72 mg/kg) soils showed a "double V″ tendency before and after the regulation. In the SHW (4.51–7.26 mg/kg) soils, HCl–S contents showed an increasing trend before the regulation and a "decreasing then increasing" trend after the regulation. Sulfide sulfur (Sulfide-S) contents increased significantly after the regulation in SHW, SEW and TFW soils. Compared to the SHW soils, C–O–S showed a similar dynamic trend in the SEW and TFW soils. Dynamic variations in C–S contents in SHW, SEW and TFW soils were similar to that of TS. On the whole, the average contents of TS, IS and OS in the three flooding wetlands followed the order: TFW > SHW > SEW during the sampling period. Sulfur forms in the three wetlands followed the order: C–S > C–O–S > H 2 O–S > HCl–S > Absorbed-S > Sulfide-S. Compared with C–O–S, C–S was significantly correlated with TN and clay, explaining the prevalence of C–S over C–O–S in wetland soils in the Yellow River Delta. The distribution of sulfur forms were significantly influenced by soil texture, organic matter, pH values, soil water and salinity. [ABSTRACT FROM AUTHOR]

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