Riverine organic carbon in the Xijiang River (South China): seasonal variation in content and flux budget

. Riverine water samples were collected from the lower reach hydrometric station Makou of the Xijiang River, in four hydrological seasons during 1997 and 1998. The samples were analyzed for their particulate and dissolved organic carbon. The contents of riverine particulate and dissolved organic carbon changed synchronously during different hydrological processes. The contents of organic carbon and total suspended substances in the riverine water increased with increasing discharge. The mass of organic carbon in the total suspended substances decreased logarithmically with increasing total suspended substances. The transported flux of organic carbon in the Xijiang River drainage is about 10.18᎒⁶ g of C km^?2 year^?1, which is two to three times larger than that of the average value in other river systems. Particulate organic carbon is the main component of riverine organic carbon, with a flux of about 8.30᎒⁶ g of C km^?2 year^?1.