Abstract:

In order to study the feasibility of improving tidal flat soil with the application of sewage sludge and to understand its effects on the physic-chemical properties of tidal flat soils and the environments, pot experiments were conducted to investigate the effects of sewage sludge on soil properties and heavy metal contents of tidal flat. Municipal sewage sludge meeting the standards for agricultural use were applied at dosages of 0, 2.5%, 5%, 10%, 15%, 20% of dry soil weight. The results showed that soil total nitrogen, available nitrogen, total and available phosphors, as well as organic matter were increased significantly. Total nitrogen and available nitrogen increased at same rates, while available phosphors increased at much higher rate than total phosphors. Soil organic content increased significantly with the use of sewage sludge, while soil pH decreased. No significant effect was observed on soil soluble total salt. Total and available contents of heavy metals in tidal flat, including Ni, Cd, Zn, Cu, Cr were significantly increased. Therefore, heavy metal contents in sewage sludge should be considered as an important criteria in practical use.