Distribution of heavy metals in tidal flat sediments and their bioaccumulation in the crab Macrophthalmus japonicas in the coastal areas of Korea

Levels of heavy metal concentrations in crab, Macrophthalmus japonicas, and in surface sediments from tidal flats in the western and southern coastal area of the Korean Peninsula were assessed in terms of metal pollution and bioaccumulation. Metal concentrations in tidal flat sediments varied considerably at various sites, mostly because of the high variability of pollutants commonly found in the area. Levels of some metals in the sediments exceeded the minimum concentration guidelines effects-range, leading to the expectation of adverse biological effects. The pollution index associated with different metals varied greatly and indicated that As, Cr, Cu and Pb contamination is relatively high in the coastal areas of Korea. The combined pollution index ranged from 0.49 to 2.88 and spatial distribution analysis indicated that runoff from an abandoned metal mine and from a variety of other industries are the main sources of metal pollution. Bulk metal concentrations in crabs showed no significant relationship with size but significant differences with sex: levels of most non-essential metals were significantly higher in females than in males, but levels of essential metals such as Cu and Zn showed no significant difference associated with sex. The concentrations of most metals in crabs were significantly positively related to those in sediments, indicating the usefulness of crabs as a bioindicator for metal pollution assessments in tidal flats. Bioaccumulation factors (BAF) were in the order of Cu>Cd>Zn>As>Ni>Pb>Cr and tended to be significantly inversely related to exposure concentrations. This indicates that other factors, besides BAF, also need to be taken into account when assessing the hazard potential of particular metals.