Environmental risks for application of iron and steel slags in soils in China: A review

Iron and steel slags are smelting wastes, mainly including blast furnace slag (BFS) and steel slag (SS) produced in the iron and steel industry. Utilization of iron and steel slags as resources for solving the problem of slag disposals has attracted much attention with increasing iron and steel smelting slags in China. Because the iron and steel slags contain calcium (Ca), magnesium (Mg), phosphorus (P), and silicon (Si), some have tried to use them as Si- and P-fertilizers, for producing Ca-Mg-P fertilizers, or as soil amendments in agriculture. However, in the iron metallurgical process, several pollutants in iron ores can inevitably transfer into iron and steel slags, resulting in the enrichment of pollutants both in BFS (mainly nickel (Ni), copper (Cu), mercury, zinc (Zn), cadmium (Cd), chromium (Cr), arsenic, lead, selenium, fluorine (F), and chlorine (Cl)) and in SS (mainly Ni, Cr, Cd, Zn, Cu, F, and Cl), in which some of pollutants (especially Cr, Ni, F, and Cl) exceed the limits of environmental quality standards for soils and groundwater. The elements of manganese, barium, and vanadium in iron and steel slags are higher than the background values of soil environment. In order to ensure soil health, food safety, and environmental quality, it is suggested that those industrial solid wastes, such as iron and steel slags, without any pretreatment for reducing harmful pollutants and with environmental safety risk, should not be allowed to use for soil remediation or conditioning directly in farmlands by solid waste disposal methods, to prevent pollutants from entering food chain and harming human health.