Today, water shortage in Iran has forced national organizations to reuse treated wastewater effluent through drip irrigation. Improper irrigation management, however, can lead to the loss of soil quality. Soil quality implies its capacity to sustain biological productivity, maintain environmental quality, and enhance plants, human and animal health. Soil quality assessment is a tool that helps managers to evaluate short-term soil problems and appropriate management strategies for maintaining soil quality in the long time. Mobarakeh Steel Complex has been using treated wastewater for irrigation of green space to combat water shortage and prevent environmental pollution. This study was performed to assess the impact of short- middle and long-term wastewater irrigation on soil quality attributes in green space of this complex. Soils were sampled from the wet bulb produced by under-tree sprinklers in three depths (0-20, 20-40 and 40-60 cm) of forested lands irrigated with treated wastewater (for 2, 6 and 18 years) or groundwater. Several chemical, physical and biological characteristics of the soil samples were determined in laboratory and compared to those of the native unirrigated soils as the controls. The results showed that pH was significantly reduced in wastewater-irrigated soils as compared to the control. Soil salinity, however, increased in the irrigated soils because of the salinity of water used for irrigation. Organic matter content of the soils significantly increased in the irrigated soils due to the litterfall produced by the artificial forest. Irrigation with treated wastewater and groundwater had no effect on soil CEC. Significant increases were observed for available Fe, Zn, Cu and Ni in the soil irrigated with wastewater. The total amounts of Cu, Ni, and Zn in the irrigated soils increased compared to those of the control but were still lower than the allowable levels recommended by the Environmental Protection Agency. Microbial basal respiration and arginine ammonification were greater in the irrigated soils in comparison to the control. Alkaline phosphatase activity, as an indicator of soil contamination, was not significantly different in soils irrigated with wastewater and underground water. In general, forestation and irrigation management of the Mobarakeh Steel Complex green space have improved most of the soil quality indexes, but some soil characteristics such as salinity need to be monitored and improved in the future. Key words : soil, soil quality, industrial treatment wastewater, Mobarakeh Steel Complex
