Seasonal and spatial impact of heavy metal contamination in the Yamuna riverine ecosystem at Delhi, India: a multi-matrix study

The ecological impact of metal contamination in the Yamuna riverine ecosystem has remained understudied. This multi-matrix investigation of cadmium, zinc, chromium, copper, lead, and iron contamination at six key sites along the river Yamuna, Delhi, in the winter, early-monsoon, and late-monsoon seasons (2022–2023). Results revealed strong seasonal variations in heavy metal levels, peaking during winter and declining in early monsoon. Various indices (heavy metal pollution index, contamination factor, and pollution load index) identified Batla House, Burari, and Kashmiri Gate as major contamination hotspots. The study highlighted the transfer of toxic metals from river water and soil into locally grown vegetables. The metal concentrations in the river water, soil, and vegetables were in the order of Fe > Zn > Cr > Ni > Cu > Pb > Cd, Fe > Zn > Cr > Cu > Ni > Pb > Cd, and Fe > Cr > Zn > Cd > Ni > Pb > Cu, respectively. In vegetables, Spinacia oleracea and Raphanus sativus exhibited the highest and lowest levels of contamination, respectively. Further, higher and lower levels of contamination were recorded during the 2nd and the 3rd sampling periods, respectively. Cd and Pb were high in all vegetables, while Zn, Cu, and Ni were below their permissible limits. This integrated assessment is among the first to connect heavy metal flux in the river at Delhi with contamination in adjacent soil and cultivated vegetables, posing significant public health risks and offering valuable insights for risk evaluation.