الفهرس 
REVIEWOnly 14 pages are availabe for public view
Abstract
SUMMARY AND CONCLUSIONS
The accumulation of heavy metals in farmland has become an important issue related to food security and environmental risk. The results of this study indicate heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) concentrations in soil and different vegetable crops associated with wastewater discharge of Abu-Rawash wastewater treatment plant, southern Giza governorate, Egypt.
- Generally, the concentrations of studied metals in wastewater samples were within the national and international recommended standards.
- The concentrations of heavy metals in study soils were higher than their concentration in water samples. Soil samples were below the critical limits of heavy metals contamination except for Cd, Cu and Zn.
- The trend of heavy metal accumulation in different parts of the studied crops followed the order Zn > Cu > Pb > Ni > Cr > Cd.
- The general low capability of the plants to accumulate high quantities of metals in aerial parts of studied vegetables, yielded small translocation factors (TF) and bioconcentration factors (BF).
- Faba bean is not heavy metals accumulators although it showed a relatively high translocation factors (TF).
- The transfer factor of study metals showed that Pb and Cr had the greatest potential of food chain entry followed by Cu, Zn, Ni and Cd.
- Health risk assessments performed showed that normal consumption of vegetables assessed poses relatively low risk from heavy metal toxicities since daily intake rates and the hazard indices obtained were below the minimal risk levels.
- Generally, the metal concentrations in aerial parts of studied vegetables were lower than the maximum limits allowed for livestock feeding, thus the potential risks for livestock was highly reduced.
- Further studies are needed on microbial content of soil and vegetables for fecal coliform on serious threat to the health of the local population. In particular, the bacteriological results of wastewater samples were unfit to irrigation purposes.
RECOMMENDATIONS
To maximize the benefits and minimize drawbacks, wastewater reuse must be carefully planned: -
- Proper management of wastewater irrigation and periodic monitoring of soil and agricultutal crops quality are required to ensure safe reuse of wastewater for irrigation.
- Government should pay attention to improve the characteristics of primary tretaed wastewater from Abou-Rawash wastewater treatment plant, especially NH3+, DO, total and fecal coliforms and consider heavy metals. Thus that soil and plants are being exposed to minimum amount of heavy metals. In that respect, organic matter and nutrients are not targeted compounds for agricultural purposes, especially if soils are poor, while pathogens are of the most importance. A particular need that has to be considered is the efficiency and reliability of a process for removing helminth ova.
- It is essential to identify the speciation of metals in different soil fractions of the study area for the determination of their potential mobility, availability and persistence in the environment.
- There are needs for a survey of the agricultural lands surrounding Abou-Rawash area that suitable for the application of primary treated wastewater in terms of soil properties, types of vegetation planted and ground water quality.
- The crops that are of major health concern are those that are eaten raw by humans or animals. In order to be effectively implemented by farmers, crop selection needs to consider economic benefits. For instance, flowers can be selected as crops because they carry a low health risk and a high economic value.
- Trickle and dip irrigation, particularly when the soil surface is covered with plastic sheeting or other mulch, it certainly provides the greatest degree of health protection for farm workers and consumers