Influence of Phosphogypsum Waste on Rainwater Chemistry in a Highly Polluted Area with High Mortality Rates in Huelva Metropolitan Area, Spain

This study evaluates the impact of phosphogypsum stacks on the chemical composition of rainwater in the Huelva metropolitan area, a metal-polluted area with high cancer and heart disease mortality rates. A total of 612 rainwater samples were collected using 17 rain gauges located around the study area between January 2021 and December 2022. The pH, conductivity, major ions, and trace metals were detected in the soluble fraction of rainwater. The results revealed spatial variability in the rainwater quality. The highest values of As, Ca 2+ , Cr, F − , NH 4 + , Ni, PO 4 3− , SO 4 2− , Sr, and V were detected in rain-gauges near phosphogypsum stacks, exceeding the levels of pH, F − , and Ni according to the guideline values for drinking water quality from the WHO. Additionally, other pollution sources also contributed: a regional source (marine factors: Ca 2+ , Cl − , K + , Mg 2+ , and Na + ) and a local source (chemical complexes emissions: Co, Cu, Pb, and Zn). A downward trend of most toxic metal(loid) concentrations in wet depositions was detected as the distance to the affected area increased. The findings revealed that phosphogypsum stacks are a relevant source of metal(loid)s with potentially adverse environmental and public health effects that, if replicated, could be relevant for environmental monitoring and policy making.