Comprehensive Perspective on Contamination Identification, Source Apportionment, and Ecological Risk Assessment of Heavy Metals in Paddy Soils of a Tropical Island

The closed-loop material and energy cycles of islands increase the susceptibility of their internal ecosystem components to heavy metal accumulation and transfer. However, limited research on the island scale hinders our understanding of heavy metal environmental geochemistry in this unique environment. This study focused on assessing a tropical island’s ecological risk by investigating heavy metal contamination and potential sources. The results revealed elevated cadmium and nickel concentrations in 0.44–1.31% of soil samples, particularly in coastal plains and developed areas. Using the absolute principal component score-multiple linear regression (APCS-MLR) model assisted by GIS mapping, we identified three contamination sources: geological factors, agricultural activities, and traffic emissions. Network analysis indicated direct exposure risks of vegetation and soil microorganisms to contaminated soil (0.4611 and 0.7687, respectively), with nickel posing the highest risk, followed by Zn, Cd, Pb, Cu, and Cr with risks transferring across trophic levels. These findings provide crucial insights for mitigating ecological risks associated with heavy metals by controlling priority pollutants and their sources in tropical island environments.