Heavy metals contamination in sediments along the eastern coast of the gulf of Thailand

Abstract

Levels of Hg, Cd, Pb, Zn, Cu, Ni, Fe and Mn in surface sediments were investigated in 52 stations along the Eastern Coast of the Gulf of Thailand. The sediment samples were collected in March 2004. Concentrations of the heavy metals ranged from 0.005 - 0.121 microgram g-1 for Hg, <0.006 - 0.19 microgram g-1 for Cd, 1.69 - 66.3 microgram g-1 for Pb, 7.48 - 131 ±g g-1 for Zn, 14.4 - 103 microgram g-1 for Cu, <0.64 - 79.9 microgram g-1 for Ni, 1.17 - 92.8 milligram g-1 for Fe and 0.03 - 1.71 mg g-1 for Mn. Only Pb and Cu in the sediments exceeded the effects range low of the proposed marine and coastal sediment quality guidelines for Thailand. The calculated geoaccumulation index (Igeo) showed that the sediments were moderately polluted with Pb in some locations, particularly at Map Ta Phut Industrial Estate, and were slightly polluted with Cu, Zn and Mn at some sampling stations. All metals (except Cu) were associated with each other in the sediments. Organic matter, clay and silt were the major sediment components responsible for most metals sorbed in the study area.