Metals in suspended sediments from the Changjiang (Yangtze River) and Huanghe (Yellow River) to the sea, and their comparison

Thirty-five samples of suspended sediments were collected at Datong Station and Lijin Station, the basin-wide control stations of the Changjiang (Yangtze River) and the Huanghe (Yellow River) during flood and dry seasons in 2000 and 2001. Concentrations of 15 elements (Fe, Mg, Ca, Al, Na, K, Ti, Mn, Ba, Sr, Pb, Cu, Zn, V, and Ni) in these samples were measured by ICP-AES. The results indicated that Fe, Al, Ti, Mn, Ba, Cu, Zn, V and Ni concentrations in the Changjiang sediments in May (flood season) were quite close to those in November (dry season), whereas Mg, Ca, Na, K, Sr concentrations were slightly higher and Pb was relatively lower in the dry season. Ti, Ba, Sr and Zn concentrations in Huanghe sediments varied little in August (flood season) and December (dry season), while Mg, Ca, Al, Na and K concentrations were higher by approximately 30% and Fe, Mn, Pb, Cu, Zn, V and Ni concentrations were lower in flood season. Concentrations of most metals, except Ca, Na and Sr were much higher in Changjiang sediments than those in the Huanghe. Such differences of metal concentrations in sediments from these two rivers could be ascribed to their different sediment sources and weathering processes within their corresponding river basin. Particularly, since the 1980s, Pb and Zn concentrations in Changjiang sediments have increased significantly due to the releases of waste/contaminants from human activities, while the variations for these two elements in the Huanghe samples were very little due to the elevated river bed in the lower reaches.