The application of soil amendments to immobilize heavy metals is a promising technology to meet the requirements for environmentally sound and cost-effective remediation. The present study was carried out to evaluate the result of phosphogypsum (PG) used alone and in combination with compost (CP) at a mix ratio of 1:1 wet weight ratio (PG + CP) at 10 and 20 g dry weight kg À1 dry soil, on heavy metal immobilization in contaminated soil and on canola growth. The results revealed that the Pb, Cd and Zn uptake of canola plants was reduced by the application of PG alone and when it was mixed with CP as compared with untreated soil. At an application rate of 10 g dry weight kg À1 dry soil of (PG + CP) the dry weight of canola plants increased by 66·8% was increased in comparison with its weight in the untreated soil. The addition of PG alone resulted in more pronounced immobilization of heavy metal as compared with PG mixed with CP. Plant growth was improved with CP addition, but heavy metals immobilization was the greatest in PG alone treatments. Results suggest that PG may be useful for the immobilization of heavy metals in contaminated soils.

Abstract. The discharge of untreated waste water in Zefta drain and drain no. 5 is becoming a problem for many farmers in the El-Mahla El-Kobra area, Egypt. The discharged water contains high levels of contaminants considered hazardous to the ecosystem. Some plants, soil, water, and sediment samples were collected from the El-Mahla El-Kobra area to evaluate the contamination by heavy metals. The results showed that the heavy metals, pH, sodium adsorption ratio (SAR), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) in the water of Zefta drain and drain no. 5 exceeded permissible limits for irrigation. In rice and maize shoots grown in soils irrigated by contaminated water from Zefta drain and drain no. 5, the bioaccumulation factors for Cd, Pb, Zn, Cu, and Mn were higher than 1.0. The heavy metals content of irrigated soils from Zefta drain and drain no. 5 exceeded the upper limit of background heavy metals. In this study, the mean contaminant factor values of the drain no. 5 sediments revealed that Zn, Mn, Cu, Cd, Pb, and Ni > 6, indicating very high contamination. The bioaccumulation coefficient values of Cynodon dactylon, Phragmites australis, and Typha domingensis aquatic plants growing in Zefta drain are high. These species can be considered as hyperaccumulators for the decontamination of contaminated water.

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A greenhouse study was conducted to explore the effect of various rates of potassium sulfate (K 2 SO 4 ) nanoparticles on alfalfa (Medicago sativa L.) growth and physiological response under salt stress. One salt-tolerant genotype (Mesa-Sirsa) and one salt-sensitive genotype (Bulldog 505) were selected based on germination under salt and were planted in pots containing 2 kg of sand. The two genotypes were subjected to 0 and 6 dS•m −1 salt levels using CaCl 2 •2H 2 O: NaCl (2:1) mixed with Hoagland solution. Three K 2 SO 4 nanoparticle treatments consisting of, 1/4, 1/8, and 1/10 of the potassium (K) level in full strength Hoagland solution (235 mg•L −1 ) were applied. Adding K 2 SO 4 nanoparticles at the 1/8 level resulted in the highest shoot dry weight, relative yield, root length and root dry weight in both genotypes. The different rates of K 2 SO 4 nanoparticles affected significantly Na/K ratio and the concentrations of Calcium (Ca), Phosphorus (P), Copper (Cu), Manganese (Mn), and Zinc (Zn) in plant tissue. The application of K 2 SO 4 nanoparticles at the 1/8 rate enhanced the plant's physiological response to salt stress by reducing electrolyte leakage, increasing catalase and proline content, and increasing antioxidant enzymes, activity. These results suggest that the application of K nanoparticles may have better efficiency than conventional K fertilizers in providing adequate plant nutrition and overcoming the negative effects of salt stress in alfalfa.

Water treatment residuals (WTR) and organic amendments can improve both organic wastes recycling and soil reclamation. The present work was carried out to evaluate the effect of vermicompost, when used alone or in combination with WTR at mixed ratios of 2:1 and 1:1 wet weight (Vermi: WTR ), on soil chemical properties of saline sodic soils, and on barley growth (Hordeum aestivm). The results showed that the soil EC, SAR, Cl -and Na + decreased significantly with the application of vermicompost alone and when mixed with WTR. Organic matter, CEC and nutrients available (N, P and K) were increased as the rate of the organic materials increased. The treatment of vermicompost: WTR (2:1 wet weight ratio) at level of 10g kg -1 soil gave the highest grain weight of barley plants compared to other treatments. Based on the results of the current study, the combinations of vermicompost and WTR can are considered as an ameliorating material to reclaim of salt-affected soils and to improve the yield of barley plants. Moreover, it can improve the efficiency of organic wastes and WTR disposal.