Distribution characteristics and ecological risk assessment of heavy metals in sediments in adjacent waters of Wailingding marine ranching

Sediment is the geological material that carries information of the evolution history of the earth and the changes of human activities. In order to understand the current situation and ecological risk of sediments, based on the survey data of 2020 and 2021 in adjacent waters of Wailingding marine ranching, we investigated the contents of particle size, characteristics indexes and six heavy metals. By using Nemero comprehensive pollution index, potential ecological risk index and geo-accumulation index, we evaluated the potential ecological risk of heavy metals. Furthermore, we discussed the possibility of heavy metal sources. The results indicate that the main type of sediments in the survey sea area was silty clay, with significant spatial differences in the content of various elements, showing a gradually decreasing trend with the increase of offshore distance. All the six heavy metals had a high positive correlation with total organic carbon. The assessment results obtained by three ecological risk assessment methods are basically consistent: the high pollution area was mainly located in the artificial reef construction area, northeast of Wailingding. The results of the nemero comprehensive pollution index show that the sediment was at Level 1 of cleanliness. The potential ecological risk index shows that Hg had the highest proportion in the evaluation, and its potential risk coefficient and ground accumulation index were significantly higher than those of other heavy metals. The results reveal that the ecological risk of heavy metals in the sediments is generally at low level, but heavy metals, especially Hg, still needs to be highly concerned.