Pollution and ecological risk assessments for heavy metals in coastal, river, and road-deposited sediments from Apia City in Upolu Island, Samoa

This study was the first to investigate the pollution and ecological risks of heavy metals in coastal, river/stream and road-deposited sediments (RDS) from Apia in Samoa. Cr and Ni concentrations in sediment samples were higher than those of other metals. River sediments and RDS had relatively high EF values around the intensive commercial areas, with a moderate to significant enrichment of Cu, Zn, Cd, and Pb. The results indicate that Cr and Ni have a natural origin from volcanic parent materials, while Cu, Zn, Cd, and Pb originated from anthropogenic activities, such as traffic emissions and the discharge of municipal wastewater. The assessments of pollution and ecological risk revealed that coastal sediments adjacent to the river are anthropogenically contaminated and present a moderate ecological risk. This study demonstrates that metals that have accumulated in the urban impermeable layer and river/stream bed have flowed into the coastal environment through runoff.

Automated summary

This study investigated the pollution and ecological risks of heavy metals in coastal, river/stream, and road-deposited sediments from Apia in Samoa for the first time. Chromium and nickel concentrations in sediment samples were found to be higher than other metals. The study revealed that the origins of chromium and nickel were natural, while copper, zinc, cadmium, and lead originated from anthropogenic activities. The findings also showed that coastal sediments adjacent to the river were anthropogenically contaminated and presented a moderate ecological risk.