Accumulation of Potentially Toxic Metals in Egyptian Alluvial Soils, Berseem Clover (Trifolium alexandrinum L.), and Groundwater after Long-Term Wastewater Irrigation

Abstract

The reduced availability of water resources in Egypt has imposed the need to intensify the use of wastewater for crop irrigation in the alluvial soils of anthropogenic origin. Relevant effects can derive from contents of potentially toxic metals (PTMs) in supply resources soils, crops, and groundwater in these areas. For this reason the PTM content has to be monitored to evaluate and minimize health hazards. Therefore, in this context, two areas of the SE Nile Delta subjected to 25 year of wastewater irrigation, using agricultural drainage water (ADW) and mixed wastewater (MWW) were chosen and compared with a nearby site irrigated with Nile freshwater (NFW). At each of the three sites, ten samples of irrigation water, topsoil, berseem clover (Trifolium alexandrinum L.) plants, and seven groundwater samples were collected and analyzed for Cr, Co, Cu, Pb, Ni, and Zn. Results indicate that the total contents of Co, Cu, Ni, and Zn in soils collected from the three sampling sites and Pb in the MWW-irrigated soils were higher than their average natural contents in the earth’s crust, indicating potential risks. The DTPA-extractable contents of Cu in the three sites, in addition to Pb and Zn in the MWW-irrigated soils, exceeded the safe limits. The MWW-irrigated soils showed a considerable degree of metal contamination, while the NFW- and ADW-irrigated soils showed moderate and low levels of contamination, respectively. The contents of the six PTMs in the three sites showed low individual ecological risks, except for Pb in the MWW-irrigated soils that showed a moderate risk; however, the overall ecological risk remained low in all samples. The values of Co, Cu, and Ni in berseem shoot in addition to Pb from the MWW-irrigated soils were over the maximum permissible levels for animal feeding. Values of root-to-shoot translocation factor were lower than 1.0 for Cr, Co and Ni but higher than 1.0 for Cu, Pb, and Zn. Berssem plant is a good candidate for phytofiltration of Cr, Co and Ni, while for extracting Cu, Pb and Zn from polluted soils. The groundwater samples collected from the three sampling sites showed lower metal concentrations than the safe limits for drinking standards. Further remediation studies should be taken into account to alleviate potential environmental and health-related risks when using supply resources different from freshwater.

Effect of Marginal-Quality Irrigation on Accumulation of some Heavy Metals (Mn, Pb, and Zn) in TypicTorripsamment Soils and Food Crops

“…This interpretation could be confirmed by lower metal partitioning in the available fraction reported for other soil types under sewage irrigation. In the Nile Delta TypicTorriorthent soils, mean DTPA-extractable contents were 1.98 mg kg −1 for Pb [39] and 1.01 mg kg −1 for Zn [40].…”

“…For instance, in TypicHaplosalid and VerticTorrifluvent soils in the Northern Nile Delta, Aitta et al [46] reported that AR for Mn did not exceed 1%. Moreover, Abuzaid et al [40] reported that ARs for Pb and Zn in TypicTorriorthent soils of the South-Eastern Nile Delta did not exceed 10 and 2%, respectively.…”

Optimized Land Use through Integrated Land Suitability and GIS Approach in West El-Minia Governorate, Upper Egypt

“…In this study, while selecting this practice for the agricultural cycle, it was necessary to pay attention to the following matters: (1) It is preferable not to reuse a particular site to grow the same type of plants that were planted on it in the previous season or in recent seasons, especially when growing seasonal plants, such as vegetables and medicinal herbs, or when replanting perennial trees, such as fruit trees and shrubs [56,[59][60][61]. (2) The ideal practice is to plant different types and varieties of seasonal crops in different locations and basins, and not to replant the same crop in the same location or basin until after a few years, as this practice helps in controlling harmful and vascular insects.…”

“…(2) The ideal practice is to plant different types and varieties of seasonal crops in different locations and basins, and not to replant the same crop in the same location or basin until after a few years, as this practice helps in controlling harmful and vascular insects. Crop rotation also eliminates weeds and maintains soil fertility and good levels of organic matter [55][56][57][58][59][60][61]. Crops that are similar in their predisposition to the same diseases, and in their susceptibility to harmful insects, should be planted at spaced intervals [62][63][64][65].…”

“…(5) If it is not possible to practice crop rotation, for practical reasons, it should partially compensate for it through interlacing and intercropping, provided that healthy soils are maintained [62][63][64][65][66][67][68][69][70][71][72]. (6) In the framework of a crop rotation system, before replanting plants of the same species in the same site, it must be ensured that the soil is free of germs and associated parasitic plants [56,[59][60][61]. The agricultural pattern of growing the same family of vegetables annually on the same plot of land to meet market demands is a good example of poor or non-successive crops rotations.…”