Abstract
The 14 C activity of dissolved organic carbon (DOC) can be used to distinguish between the fossil organic carbon due to petrochemical effluents and modern organic carbon due to domestic wastes and natural decaying organic matter. Rivers polluted by petrochemical effluents show varying amounts of depression of the DOC 14 C activity, reflecting concentrations of 14 C-deficient fossil carbon of as much as about 40 percent of the total DOC.