A pot experiment was carried out at the experimental farm of Soil and Water Department, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo, Egypt during the summer season of 2014 to evaluate the effect of some seaweed on remediation of a soil contaminated with heavy metals (Zn, Pb, Mn and Cu), also to assess the effect of seaweed on growth (roots and shoots) contents from heavy metals of red radish (Raphanussativus L.). Surface soil samples (0-30cm) were collected from El-Gable El-Asfer farm located 25km northeast Cairo, Egypt. The experiment involved 39 pots comprised 13 treatments in three replicates in a completely randomized design. Two types of seaweeds (Ulva sp.and Gelidium sp.) were dried in an oven at 600C for 24 hr, and mixed with soil at different rates 0.1, 0.2, 0.3, and 0.4 ton fed-1, before planting. ). Soil samples were collected from all pots after harvesting, air dried and then sieve. Some physical, chemical analysis and available Zn, Pb, Mn and Cu were determined in the experiment soil. In this study, a program of observations and measurements was developed, concerning: morphological, productivity and root contents from heavy metals.
The results of this study indicated that the values of soil bulk density decreased as a result of application seaweeds as compared with the control, while soil total porosity, available water, organic matter and available micronutrients increased due to the treatments used compared to the control. Also, plant dry weight yield values (roots and shoots) increased with of seaweeds treatments application, the treatments under investigation gave higher percentage values of micronutrients (content and uptake) in (roots) of red radish plants than shoots as compared to the control. Seaweeds play an important role in the chemical behavior of heavy metals in soil; decomposition of organic matter is followed by formation of active groups which have the ability to retain the metal in the complex and chelated form. The chemical behavior of the metal changed from cation to anion as well as the release of organic acids which slightly decrease the soil reaction (pH).