Arsenic and heavy metal pollution in wetland soils from tidal freshwater and salt marshes before and after the flow-sediment regulation regime in the Yellow River Delta, China

Abstract

Summary Soil samples were collected in tidal freshwater and salt marshes in the Yellow River Delta (YRD), northern China, before and after the flow-sediment regulation. Total concentrations of arsenic (As), cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) were determined using inductively coupled plasma atomic absorption spectrometry to investigate the characteristics of heavy metal pollution in tidal wetlands before and after the regulation regime. The results demonstrated that marsh soils in both marshes had higher silt and total P contents, higher bulk density and lower sand contents after the flow-sediment regulation; moreover, soil salinity was significantly decreased in the tidal salt marsh. As and Cd concentrations were significantly higher in both marsh soils after the regulation than before, and there were no significant differences in the concentrations of Cu, Pb and Zn measured before and after the regulation. No significant differences in heavy metal concentrations were observed between freshwater and salt marsh soils, either before or after the regulation. Before the regulation regime, soil organic matter, pH and sulfer (S) were the main factors influencing heavy metal distribution in tidal freshwater marshes, whereas for tidal salt marshes, the main factors are soil salinity and moisture, pH and S. However, bulk density and total P became the main influencing factors after the regulation. The sediment quality guidelines and geoaccumulation indices showed moderately or strongly polluted levels of As and Cd and unpolluted or moderately polluted levels of Cu, Pb and Zn; As and Cd pollution became more serious after the regulation. Factor analysis indicated thatthese heavy metals including As were closely correlated and orginated from common pollution sources before the flow-sediment regulation; however, the sources of As and Cd separated from the sources of Cu, Pb and Zn after the regulation regime, implying that the flow-sediment regulation regime contributed to As and Cd accumulation in the YRD.