Identification of heavy metal pollution in estuarine sediments under long-term reclamation: Ecological toxicity, sources and implications for estuary management

Sediment samples were collected to clarify the effect of changing sedimentary environment under long-term reclamation on heavy metals (Cr, Zn, Pb, Cu, Cd, and Ni) in a partially mixed estuary (Modaomen) of the Pearl River Delta. The ecological toxicity and source apportionment of these metals were discussed as well. The metal species during the 2010s (as 2015, 2018) was more enriched than that during the 2000s (as 2003) and 1990s (as 1991). This estuary overall suffered from a moderate-to-high pollution status. The element Cd was a major concern for the ecosystem's health because of its high toxicity. Sediment quality guidelines suggested that adverse biological effects were likely to be caused by Cu and Cd in the early adjustment stage, while the threats to marine organisms caused by the elements of Cu, Cr, Zn, and Ni were elevated during the 2010s. Two receptor models of PCA-MLR and PMF quantified the source types and contributions of these heavy metals. Strong intensity of industrial activities coupling with agricultural applications and import of adjacent seas were responsible for the enriched accumulation of heavy metals in sediments. Metal source apportionment would help to control the metal input into the estuary; identifying the role of sedimentary environment on heavy metals can inform the sediment quality management in the estuary.

Automated summary

After long-term reclamation, the Modaomen estuary of the Pearl River Delta suffered from moderate-to-high pollution status due to enriched accumulation of heavy metals like Cr, Zn, Pb, Cu, Cd, and Ni, with Cd being a major concern for ecosystem health. Receptor models quantified the sources and contributions of these heavy metals, highlighting the importance of controlling metal input and managing sediment quality in the estuary.