The answer will depend on where the project is located. For instance, the United States is divided into different regions and the U.S. EPA for the region sets the permissible maximum contaminant level for each media (soil, surface water, sediment, air) for that region.
AoA. The limits of metals in different sources are very tentative and area- and purpose specific. I will suggest you to locate this information from Chinese literature preferrably. Otherwise, you can have look of book by Alloway "Heavy Metals in Soils".
There are a large number of toxic trace elements and its permissible limit varies from one element to other. Guide line for permissible limits of different sources also varies. In addition to this permissible limits also varies in countries according to their guide lines. However good on line literature available which may solved the purpose.
Canadian Lowest Effects and Probable Effects Levels for toxics in sediment are available from the Canadian Council of Minister of the Environments (or CCME) - Google "Canadian Sediment Quality Guidelines for the Protection of Aquatic Life". CCME also publishes limits for soil and water as well.