Unstable geogenic arsenic in reclaimed coastal soils poses environmental risks
Meng Chen, Li Yan, Yuting Zhang, Wenbing Ji, Yuanyuan Lu, Zhen Song, Lei Wang, Tao Long
Abstract
Rapid urbanization has driven extensive coastal land reclamation worldwide. However, the soils used often contain geogenic contaminants, particularly arsenic, posing a largely unrecognized but substantial threat to the environment and human health. Here we present a comparative analysis of arsenic speciation in naturally contaminated coastal soils, revealing distinct risk profiles between reclaimed and natural environments. Analysis of 1029 soil samples from the Pearl River Delta, with detailed characterization of 29 high-arsenic samples using integrated chemical and microscale techniques, identifies two contrasting arsenic occurrence patterns: reclaimed soils dominated by unstable arsenic sulfide species versus natural hilly soils characterized by stable arsenic oxide species. The findings demonstrate that land development activities, hydrological dynamics and sea-level rise can trigger arsenic release in reclaimed soils. To mitigate these risks, an integrated risk management framework is proposed. This research provides valuable insights to inform sustainable land reclamation management across rapidly urbanizing coastal regions. Reclaimed soils contain unstable arsenic-sulfur species resembling unweathered parent rock leading to arsenic mobilization through land development, tidal dynamics and sea-level rise, according to an analysis of 1029 soil samples from the Pearl River Delta, China.