The enrichment of phosphorus (P) in groundwater (GW) has been regarded as one of the most important sources of water eutrophication, but its sources and mechanisms have remained unclear. This study focused on hydraulic change show that drove the migration of P in an agricultural groundwater system, Jianghan Plain, Central China. Based on four rounds of field investigation over different seasons and across two consecutive years. Seasonable water table fluctuations (WLFs) reached 1.6 m and 3.8 m in GW and surface water (SW), respectively. Moreover, the concentrations of P in GW were obviously higher than those in SW where 54.1% of all GW samples presented higher content of P than the World Health Organization (WHO) limit of 0.4 mg/L with the highest one arriving to 1.97 mg/L. Although the trends and amplitudes varied at different points and depths, the spatial and temporal distribution of P corresponded with the local WLFs that were responsible for the enrichment of GW P. On the one hand, WLFs changed hydraulic conditions to enhance the migration of soluble P in the unsaturated zone into the aquifer. On the other hand, WLFs resulted in changes to the redox conditions or to the GW hydrochemical compositions, which promoted the dissolution of Fe or Mn containing P. These caused the release and enrichment of P in GW. Therefore, this study helps understand the geochemical cycling of P and improves GW management in the local GW system, Jianghan Plain.
Keywords: Enrichment; Groundwater; Influence; Migration; Phosphorus; Water table fluctuations.
© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.