Assessment of potentially toxic elements (PTEs) in surface and groundwater of volcanic and granite regions of Hainan Island, China: Pollution status, sources, and health risk evaluation.

Abstract

The safety of water resources in regions with naturally high geochemical backgrounds of potentially toxic elements (PTEs) represents a critical environmental issue. This study investigates the concentrations, sources, and health risks of PTEs in surface water and groundwater from volcanic and granite regions of Hainan Island, China. A total of 58 surface water and 26 groundwater samples were collected from the volcanic region, along with 22 surface water samples from the granite region. Ten PTEs (As, Cd, Pb, Se, Hg, B, Cr, I, Mo, and F) were analyzed using a combination of atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS), ion-selective electrode method (ISE), and catalytic spectrophotometry (COL). The results showed that surface water generally contained low PTE concentrations, remaining below national regulatory thresholds, whereas groundwater in the volcanic region exhibited significantly elevated levels of As (up to 59 μg/L) and Cr (up to 23.4 μg/L). Pollution index (PI) results indicated that 15.4% of groundwater samples exceeded the acceptable limit for As. Health risk assessments revealed that while non-carcinogenic risks were generally low, arsenic in groundwater posed potential health concerns for children (HQ approaching 1). Carcinogenic risk assessment further identified As and Cr in groundwater as the dominant contributors, with total cancer risk values exceeding the acceptable limit (> 1.0 × 10^- 4), reaching 3.67 × 10^- 3 for adults and 4.37 × 10^- 3 for children. These findings demonstrate the combined influence of geological and anthropogenic factors on groundwater quality in volcanic regions and underscore the urgent need for targeted monitoring and region-specific water safety strategies in Hainan.