Characteristics of Sludge from Sewage Discharge Channels of Tianjin, China

In 1998, sludge samples were taken from the sewage dischargechannels of Tianjin, China, and concentrations of 50 elementsand total organic carbon (TOC) were detected by inductively coupled plasma-atomic emission spectrometry (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), instrumental neutron activation analysis (INAA), and otherconventional methods, and the results are reported in thisstudy. The sludge samples contain high concentrations oforganic matter, with the median value of TOC 15.5%. Comparedwith sediments from the intertidal flats of Bohai Bay, highconcentrations of Sn, Zn, Cu, Pb, Sb, Bi, Cr, Ni, P and Ba areobserved in the sludge. However, rare earth elements, alkalielements, Ti and Al do not show a correlation with pollution.From the urban side to the coastal side, the spatial variationof concentrations of the pollution-related elements is quiteirregular, indicating that the channels receive dischargesalong the course. No significant pollution in sediments at theoutlets of the sewage discharge channels was observed, whichmay be attributed to the dispersion of pollutants andpurification of the Bohai Bay. Factor analysis has revealed thetwo controlling factors of `pollution' and `background' on theelemental composition of the sludge.