大阪湾底泥の堆積速度と重金属汚染

抄録

The accumulation rates of sediment cores in Osaka Bay have been determined by using ²¹⁰Pb dating technique. In the upper 10 cm ²¹⁰Pbex contents show a constant value with depth. The accumulation rates below the homogeneous layer of sediments ranging from 0.12 to 0.61 cm y^-1 (0.067-0.34 gcm^-2y^-1) were obtained. The higher contents of Zn, Cu, Pb and Cr were observed in the upper 10 to 30 cm of sediments. Assuming that the increment of heavy metal content in sediments is due to anthropogenic origin, the amount of anthropogenic input of heavy metals into sediments were estimated to be 1, 300-2, 700μg cm^-2 for Zn, 150-480 for Cu, 360-410 for Pb and 320-480 for Cr. The increment appears to start about 100 years ago. In surfical sediments most of heavy metal contents exceeded the background content, and thenmost part of Osaka Bay is polluted by heavy metals.