Key factors affecting heavy metal contamination of mangrove sediments in the Zhangjiang Estuary: Implications for environmental management.

With the rapid economic development of coastal cities, the discharge of significant amounts of heavy metal pollutants has posed a severe threat to mangrove forests. However, the potential sources of these metals and the health risks they pose remain poorly understood. This study analyzed 14 heavy metals in mangrove and river sediments of Zhangjiang Estuary, southeastern China. Concentrations ranged from 0.001 to 1.324 mg/g, with boron, nickel, lead, and zinc showing highest levels. Mangrove areas were influenced by external inputs while estuarine sediments by river and point sources. Ecological risk assessment identified cadmium and arsenic as most hazardous elements. Principal component analysis revealed three pollution sources: industrial and agricultural activities (55.01 %), agricultural activities with natural deposition (31.51 %), and natural geological background (13.48 %). Mangrove areas generally showed low pollution and functioned as ecological barriers, though localized high-risk areas existed. Cadmium contamination originated from industrial wastewater and agricultural runoff, while arsenic from pesticide and fertilizer applications. Enhanced pollution source management is essential for protecting mangrove ecological functions.