Abstract
Due to water scarcity, the use of wastewater to irrigate crops is on the rise all over the world, including in Egypt (particularly untreated wastewater). The purpose of this study is to see if irrigation with untreated industrial wastewater in natural fields can cause Abelmoschus esculentus Moench. (okra plant) to accumulate and translocate eight trace metals (lead: Pb, cadmium: Cd, chromium: Cr, copper: Cu, iron: Fe, manganese: Mn, nickel: Ni, and zinc: Zn) in its different tissues. It was extended to look at the effects of wastewater irrigation on the farmed okra plants' growth characteristics, nutrients, colors, and organic content. Two studied sites at South of Cairo have been investigated: the first site (29°42'31.17" N and 31°15'11.56" E) represented by five cultivated fields irrigated with Nile water (control) and the second site (29°42'37.87" N and 31°17'14.53" E) fields irrigated with effluent received untreated industrial wastewater. Three composite soil and irrigated water samples were collected from each site. Because of wastewater irrigation, soil and plant nutrients (nitrogen, potassium, and phosphorus) decreased significantly (at P < 0.01), whereas trace metals increased significantly (at P < 0.01 and P < 0.05) for soil and plant samples irrigated with untreated wastewater. Due to irrigation with untreated wastewater, there was also a significant decrease in okra growth metrics (at P < 0.05) and leaves photosynthetic pigments: chlorophyll a and b, and carotenoids (at P < 0.01 and P < 0.05). In the plant's fruits (edible section) watered with wastewater, iron was the most abundant metal. Besides, Cd, Cu, Fe, Mn, Ni, and Zn concentrations were also in the phytotoxic range (42.57, 140.67, 2756.67, 1293.33, 1326.67, and 877.83 mg kg-1, respectively). All trace elements examined accumulate in the roots of wastewater irrigated okra (Bioaccumulation factor > 1). Okra plants, on the other hand, did not have an accumulated trace metals strategy in their shoots since the translocation factor was less than one. Because of substantial trace metal accumulation in their edible sections, the scientists advised against eating okra plants grown in fields watered with untreated wastewater.
Highlights
Food production increases continuously to meet the demand of increasing populations, which creates a severe challenge to the agricultural community to increase food production by more than 70% (Kannan and Anandhi 2020)
These industrial sewage effluents are considered the main source of nutrients and organic matter, but they are a source of many trace metals (e.g. Cu, Cr, Cd, Co, Fe, Mn, Ni and Zn), which accumulate in the soil, transfer to plants growing in these polluted soils (Balkhair and Ashraf 2016)
The concentration of all trace metals (Pb, Cd, Cr, Cu, Fe, Mn, Ni, and Zn) was increased significantly as a result of using untreated industrial wastewater in irrigation, while they are still in the safe tolerable limits according to WHO (1996) except Fe, Mn and Zn which exceeds the tolerable limits (Table 1)
Summary
Food production increases continuously to meet the demand of increasing populations, which creates a severe challenge to the agricultural community to increase food production by more than 70% (Kannan and Anandhi 2020). The industrial wastes and sewage water are drained to agricultural fields where they are used to irrigate different vegetable crops. These industrial sewage effluents are considered the main source of nutrients and organic matter, but they are a source of many trace metals (e.g. Cu, Cr, Cd, Co, Fe, Mn, Ni and Zn), which accumulate in the soil, transfer to plants growing in these polluted soils (Balkhair and Ashraf 2016). Due to the continuous application of wastewater in agricultural irrigation, the accumulated trace metals increase to toxic levels in soil and enter the food chain due to uptake and accumulation of these trace metals by growing crops (Ahmed and Slima 2018). The pathway of trace metals entrance into the food web is the uptake and accumulation of these metals by crops grown in polluted soils (Christou et al 2017)
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