Arsenic in surface sediments of the southwestern coast of Laizhou Bay, China: Speciation, spatial distribution, sources and contamination risk assessment.

A total of 49 surface sediment samples were collected from the southwestern Laizhou Bay (SWLZB) and its connected fluvial systems. Multiple analytical approaches were combined to explore the total arsenic (As) levels, geochemical fraction, spatial distribution patterns, pollution features, potential ecological hazards and probable source contributions of sedimentary As in this coastal region. The measured total As concentrations in surface sediments varied between 8.06 and 34.71 μg g-1, with an average of 17.87 μg g-1, showing an apparent spatial trend that As concentrations generally declined from west to east across the study domain. The modified BCR sequential extraction method was applied to separate sediment As into four geochemically distinct fractions with varied concentration ranges: acid-soluble fraction (Sol: 0.61-3.79 μg g-1, average = 1.62 μg g-1), oxidizable fraction (Oxy: 0.18-2.25 μg g-1, average = 0.87 μg g-1), reducible fraction (Red: 0.60-7.23 μg g-1, average = 2.60 μg g-1), and residual fraction (Res: 1.64-21.45 μg g-1, average = 7.54 μg g-1). Multiple contamination evaluation indices were jointly adopted to assess As pollution status, and the overall results suggested moderate As contamination alongside relatively low potential ecological risks over most parts of the study area; notably, relatively high As accumulation was observed at sampling stations along the Xiaoqinghe River. Source discrimination results implied that geogenic inputs likely constituted the dominant supply of sedimentary As in the SWLZB, while anthropogenic wastewater emissions may deliver considerable As loads to fluvial sediments distributed in the western coastal river reaches.