Impact of Wastewater Irrigation on Soil Mechanical Properties in the Green Space of Mobarakeh Steel Complex

Long-term use of treated wastewaters for irrigation adds compounds and/or ions to soils which might alter the soil physical, hydraulic and mechanical properties. Soil mechanical properties are closely linked with the plant growth. This study was conducted to investigate the effect of short-, mid- and long-term applications of the treated wastewater of Mobarake Steel Company in Isfahan on the soil penetration resistance and shear strength in the company green space. Soil penetration resistance and shear strength were measured using a pocket penetrometer and in situ shear box, respectively. The results showed that soil penetration resistance (i.e. soil hardness) at both dry and wet conditions significantly was increased upon short-, mid- and long-term applications of wastewater; 19 years of the application of wastewater resulted in the highest soil penetration resistance at wet condition, but the well water did not significantly affect it. Surface crust in the non-irrigated locations increased the soil penetration resistance, but the irrigated sealed soils were not significantly different from the virgin soil in terms of dry and wet penetration resistances. For the soil shear strength parameters, wastewater, well water and surface crust did not significantly affect soil cohesion (c), they but significantly affected the angle of internal friction (φ). Overall, soil shear strength parameters were not greatly affected by the irrigation water treatments because of the dominant effect of the soil fractions (texture and gravel content) and the microstructure.