The human impacts level and migration of heavy metals in original inshore sediments of Dongying, China

Largely uncontrolled exogenous heavy metals (HMs) are released into the sea which eventually deposit in the original inshore sediments. However, the migration of these HMs was commonly overlooked in previous studies, which makes it hard to determine the fate of these HMs and locate the high-risk HMs pollution areas. Therefore, the original inshore areas in Dongying, China were taken as an example, and eight HMs (As, Cd, Cr, Cu, Hg, Pb and Zn) in sediments and multiple geochemical indexes relevant to the properties of sediments were determined to clarify the level of human impacts on the aggregation of HMs and uncover the migration of HMs from nearshore to offshore. The obtained results suggested relatively low pollution of HMs based on the values of EF and Eri. Due to the intense marine erosion, HMs in the sediments mainly stem from the natural deposition, but are less affected by human activities. Mariculture is widespread but fails to exert its impact on the accumulation of HMs in sediments, mainly due to just the phosphorus, instead of the organic matters, which aggregate effectively. More exogenous HMs are moved from nearshore to offshore so that the offshore rather than nearshore is more susceptible to human activities, confirmed by the higher concentration and EF of HMs in the offshore areas. The migration of HMs may be more related to the altered minerals than the composition of grain size in sediments. The conversion of hydrodynamic conditions induced by runoff reduction may transport more altered minerals along with HMs to a farther area of sea and threaten the broader area of sea.