Cadmium (Cd) pollution poses a threat to human health, and research on Cd bioavailability as well as its ecological risk assessment can help prevent and mitigate Cd hazards. The enrichment characteristics and variability of Cd were investigated in sea-land interaction soil fractions and the associated environmental and ecological risks were evaluated using the accumulation index (Igeo), potential ecological hazard index (Er), and risk assessment coding (RAC). The results showed that:① The Cd content of miscellaneous fill material was typically lower than 0.3 mg·kg-1 and that of plain full was higher than 0.3 mg·kg-1. The Cd content of marine sediment was significantly higher than that of continental sediments, averaging 0.36 and 0.10 mg·kg-1, respectively. The concentration of Cd in marine sediments buried at shallow depths (<5 m) was generally higher than at greater depths (>5 m). ② There was a moderate correlation between Cd and CEC in artificial fill (Q4ml; correlation coefficient=0.52, P<0.05). There was a weak correlation between Cd and organic matter in the marine sediments (correlation coefficient=0.49, P<0.05). Total cadmium and the physical and chemical properties of soil had a significant influence on the fraction of soil cadmium. ③ The Igeo of artificially fill and marine sediment was dominated by the relationship 1 < Igeo < 2, which indicated a moderate level of pollution. The Er of artificial fill and marine sediment was mainly 80 < Er < 160, indicating a high potential ecological hazard. Soil acid-extractable Cd accounted for more than 50% of the total Cd in each drill hole, which generally indicated a very high potential ecological risk. These results provide a basis for environmental and agricultural decision-making and provide theoretical guidance for soil pollution investigations and remediation.
Keywords: Cd fractions; Nansha of Guangzhou city; Soil cadmium; ecological risk assessment; influencing factors.