Phytoextraction and estimating optimal time for remediation of Cdcontaminated soils by spinach (Spinacia oleracea L.)

The so-called phytoextraction in which hyperaccumulator plants are used to remediate the contaminated soils is proven to be an efficient method. The objective of this study was to investigate the capability and efficiency of spinach for phytoremediation of cadmium from Cd-contaminated soils. For this purpose, a completely randomized design with five treatments including 0, 15, 30, 60 and 120 mg Cd/ kg soil and three replications was established in natural conditions. After contaminating the experimental soils with different levels of cadmium, the seeds of spinach were planted. When plants were fully developed, plants were harvested and their cadmium contents in shoots and roots as well as the soil-cadmium were measured. The results indicated that by increasing Cd concentration in soil, the most Cd accumulation was occurred in the roots rather than shoots. Maximum cadmium concentration within the shoots and roots was 73.7 and 75.86 mg.kg 1 soil, respectively. According to spinach ability to absorb high concentration of cadmium in the root zone and its high biomass and capability of cadmium accumulation in shoots, this plant can be used as a hyperaccumulator to remediate cadmium from Cd-contaminated soils. But, according to minimum remediation time and maximum dry matter for the 30 mg Cd/ kg soil, maximum Cd extracted by shoots in hectare/year was in 30 mg Cd/ kg soil. It can be concluded that spinach is a suitable plant for phytoremediation of slight to moderately cadmium contaminated topsoils.