Remediation of soils polluted with heavy metals

A pot experiment was performed in a greenhouse to study. the remediation of soil polluted with Cd and Pb using some chemical and organic soil amendments such as gypsum, lime, organic compost, Fe and Zn chelates. Also,phytoremediation by growing some crops, i.e., kenaf plants as a fibre crop and comparing with red radish plants as an edible crop was taken into consideration. The soil was collected from EI-Gabal El-Asfar farm, El-Qalyobiya Governorate which irrigated with sewage effluent for long time. The treatments of soil amendments were mixed thoroughly with the experimental soil. Gypsum treatments were added at rates of 0, 5, 10 and 20 ton/fed; lime at rates of 0, 1, 2 and 4 ton/fed; compost at rates of 0, 7, 14 and 21 ton/fed. For Fe-EDDHA and Zn-EDTA, the treatments were added at rates 0, 1, 2 and 4 kg/fed. Red radish (Raphanus sativus, L.) and kenaf (Hibiscus cannabinus, L.) were planted and harvested after 56 and 60 days, respectively. Data showed that the values of the dry matter yields of shoots, roots and whole plants for both two species increased gradually with increasing applied rates of different soil amendments, being compost treatment was most effective. Generally, application of the used soil amendments at different rates decreased Cd and Pb concentrations and uptake by shoots and roots of red radish and kenaf plants as compared with the control, the decrease was progressive and significant with increasing rate. The compost treatment under different rates was the most efficient amendment in decreasing Cd and Pb concentrations and uptake by shoots and roots. Most of Cd and Pb taken up by red radish plants were retained in the roots and consequently less amount of Cd and Pb were translocated to shoots. On the contrary, most of Cd and Pb taken up by kenaf plants were accumulated in the above ground parts. Available and availability index of Cd and Pb in the soil after cultivation with both plants were reduced under different sources of soil amendments. The highest reduction of available and availability index of Cd and Pb was obtained under application of compost at a rate of 21 ton/fed. Accordingly, these soil amendments (gypsum, liming, compost, Fe-EDDHA and Zn-EDT A) have ability to minimize the immediate risk of the presented heavy metals through decreasing its mobility, hence reducing phytoavailability.