الفهرس 
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Abstract
The present investigation was carried out to evaluate the quality of agricultural drainage water for irrigation purposes, and its effect on soils and plants grown in Northern Dakahlia Governorate, Egypt.For this purpose, twenty locations for soil, agricultural drainage water and plant sampling were selected by the aid of Global Positioning System (GPS) technique to provide a represented distribution of environmental resources in the studied area (Gamasa Ditrict, Dakahlia Governorate). The obtained results could be summarized as follows: Hydrochemical assessment of drainage water resources showed that the highest concentrations of soluble salts were recorded at the northern sites (6-7 dS m-1), and the lowest concentrations (1-2 dS m-1) were recorded in areas located at southern sites.The northern sites showed very high levels of potential salinity (42-48 meq L-1) because of the seawater intrusion effect. Most of investigated water resources are classified as class 1 according to FAO guidelines (Fig. 4). Other sites, including those at northern parts, were classified as class 2.Drainage water resources showed a low potential sodicity hazardous effect due to the low RSC index as most of these values were minus except only one location.Boron concentration in all irrigation samples did not exceed 1.0 mg L-1 (0.34-0.96). The highest boron concentrations in the studied sites were associated with the adjacent sea sites (0.8-0.96 mg L-1), and the lowest boron concentrations were observed in southern locations.Cadmium concentration in all studied sites was below the maximum allowable limit given by FAO guidelines (0.01 mgL-1). Most of these concentrations are ranged between 0.002-0.003 mgL-1; however, some spots (L12 and L16) showed relatively higher Cd2+ concentration (0.003-0.004 mg L-1) due to specific anthropogenic activities.Particle size distribution of bottom sediments of drainage water showed a very limited content of silt and clay (7.9%). Silt and clay content showed a high correlation with available Cd2+ concentration in sediments (R2=0.60), and a low correlation with available Pb2+ concentration (R2=0.04) suggesting the low affinity of silt and clay to Pb2+ comparing with organic matter.The electrical conductivity of soil sediments varied among different locations with an average value of 1.88 dS m-1. pH value of all sediments reflects the alkaline nature of bottom sediments with an average pH value of sediments was 9.27.Pb2+ concentration in bottom sediments was above normal reference range of available Pb2+ (0.16 mg Kg-1) extracted using ammonium acetate (the method of extraction in our experiment). The average concentration of Pb2+ in different sites was (0.585 mg kg-1). The calculated Igeo index of Pb2+ concentration in sediments could be classified as slightly contaminated and some sites were classified as uncontaminated.The average value of Cd2+ concentration was 0.002 mg kg-1. This value was below the reference Cd2+ concentration extracted by ammonium acetate (0.004 mg kg-1). The geoaccumulation index (Igeo) revealed the low Cd2+ pollution potentiality in all studied sites Ec values of most tested sites were classified as slightly saline. However, some specific sites (i.e. L11 and L12) suffered from salinity hazards and classified as moderately saline and highly saline, respectively. pH value of soil was very high with an average value 9.2 and 9.4 in surface and subsurface layers, respectively.The average value of CEC was 9.87 Cmol Kg-1. The highest CEC value (15 Cmol Kg-1) was recorded in L2; however, the lowest value (4.57 Cmol Kg-1) was recorded in L17. The concentration of available Pb2+ in the investigated soils was <1.0 mg Kg-1. Igeo index indicated that all studied soil samples are classified as uncontaminated or slightly contaminated either its surface or subsurface layers.Data of Cd2+ determination showed relatively low labile concentration. The average concentration of Cd2+ in surface layer was higher than that in subsurface layer (0.006 vs. 0.002 mg kg-1, respectively). Igeo index values of all investigated locations were minus (below zero) confirming the un-contamination of all soil location with Cd2+.Phenotypic investigation of irrigated soils showed a wide range of different food, feed and wild weeds. Lead concentrations in cultivated plants of different locations were noticeably high with an average concentration of 8.65 mg kg-1 suggesting the potential accumulation from airborne resources. Crop pollution index (CPI) of different investigated plants showed a severe pollution index in some cases. These sites were located mainly from L12-L20. Few locations were classified as alert to slight potential, and most of locations were classified as slight to moderate pollution. Cadmium concentration in plants showed also an increase with an average concentration 0.44 mg kg-1. Crop pollution index of cadmium was in similarity with that of lead. The first locations (L1 and L2) showed the lowest pollution index (alert to slight pollution); however, the locations at the end of experimental site (L13-L20) showed the highest pollution index (moderate pollution to severe pollution).Conclusions In conclusion, drainage water resources of the investigated locations are acceptable for irrigation. These water resources can be reused wisely under restricted precautions. Physicochemical analyses of bottom sediments should be performed regularly in order to avoid the release of pollutants into water. Fresh edible plants should be avoided in such vulnerable areas, and other tolerant crops can be cultivated under proper management practices.