Long-Term Effect of Heavy Metal–Polluted Wastewater Irrigation on Physiological and Ecological Parameters of Salicornia europaea L.

Irrigation of Salicornia europaea with heavy metal–polluted wastewater is a promising alternative method for risk mitigation of the Urmia Lake ecosystem from uncontrolled sewage. The objective of the study was to evaluate morphological and physicochemical responses of Salicornia europaea under wastewater irrigation at different growth stages. A field experiment was conducted in a split-plot experiment based on randomized complete block design with four replications. Treatments included control and wastewater irrigation (containing zinc (Zn), iron (Fe), copper (Cu), cadmium (Cd), lead (Pb), and nickel (Ni)) at three stages (vegetative, flowering, and reproductive) of plant growth and two times (two and 4 days in each stage). The result showed that the wastewater application at reproductive stage resulted in higher biomass production than that of the control plants. Wastewater irrigation at the flowering stage caused a significant increase in the amount of total chlorophyll and chlorophyll-a, while chlorophyll-b content was decreased at both flowering and reproductive stages. The amount of the total soluble protein was also affected, with wastewater irrigation showing the most significant increase at the reproductive stage. There was significant enhancement of osmolytes in leaves of plant under heavy metal stress, and the increased rate of proline was higher than soluble sugar at the flowering stage. Relative water content in Salicornia was not duration- and time-dependent. A 154% increase in catalase activity, 32% increase in peroxidase activity, and 57% increase in polyphenol oxidase activity were observed in the plant exposed to long-term wastewater duration. Based on the observed positive effect of wastewater on shoot length and weight, total soluble protein, proline, soluble sugar, enzyme activities, and plant biomass of Salicornia europaea, long-term effect of heavy metal–polluted wastewater irrigation can be approved for Salicornia crops in coastal areas.