Effect of Wastewater Irrigation on Heavy Metal Accumulation, Growth and Yield of Vegetables

Abstract

<jats:p>Use of wastewater for irrigation is on the rise in India and other developing countries. Wastewater contains plant nutrients that favour crop growth but leave a burden of heavy metals which can enter the food chain and is a cause of great concern. This study was conducted to explore the possibility of using wastewater to grow four vegetables fenugreek (Trigonella foenum-graecum L.), spinach (Spinacia oleracea L.), radish (Raphanus sativus L.) and carrot (Daucus carotaL.). Two aspects namely (1) effect on plant growth and yield (2) accumulation of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb) and zinc (Zn) in leaves and roots of the plant have been presented in this paper. The physico-chemical analysis of the wastewater showed that it was rich in total suspended and dissolved solids with large amount of BOD and COD. The higher amount of Cl-, Ca++, Mg++ and K+ were also present in the effluent. The heavy metal (Cd, Cr, Cu, Ni, Pb and Zn) content in wastewater is comparatively more than groundwater (GW). The values of these heavy metals were slightly higher in the soil irrigated with wastewater. The effluent severely affects crop plants and soil properties when used for irrigation. The growth characteristics (plant length, plant fresh and dry weight, leaf number and leaf area) as well as yield characteristics (seed number, 1000 seed weight and seed yield) of all the plants, irrigated with 100% wastewater, were more than that with groundwater. The pattern of increase for the plants was fenugreek&gt; radish&gt; spinach&gt; carrot. Though the wastewater contains low levels of the heavy metals, the soil and plant samples show higher values due to accumulation, but their level was under permissible limits in plants. The trend of metal accumulation in wastewater-irrigated soil is in the order: Pb&gt; Ni&gt; Zn&gt; Cu&gt; Cr&gt; Cd. Of the four plants that are grown, the order of total heavy metal accumulation in roots is Carrot&gt; Radish, while in leaves the order is Spinach&gt; Fenugreek. The enrichment factor (EF) of the heavy metals in contaminated soil is in the sequence of Ni (3.1)&gt;Pb (2.6)&gt; Cd (2.35)&gt; Zn (2.18)&gt; Cu (1.66)&gt; Cr (1.05), while in plants EF varies depending upon the species and plant part. Radish and carrot show a high transfer factor (TF &gt;1) for Cd signifying a high mobility of Cd from soil to plant whereas the TF values for Pb are very low as it is not bioavailable. Thus, it may be concluded that wastewater may be used profitably for the cultivation of these vegetables and could effectively supplement not only the nutrient requirement of the crop but may also act as the source of water.</jats:p>

Heavy Metal Contamination Status of Water, Agricultural Soil, and Plant in the Semiarid Region of Kandahar, Afghanistan

“…7 Similarly, the wastewater concentrations of Cu, Zn, and Pb were nearly 35, 23, and 35% higher, respectively, compared to the groundwater. 52 Another study 48 showed that in Egypt, the Pb, Zn, and Cu levels in wastewater were more than 50, 77, and 82% higher compared to freshwater from the Nile River, respectively.…”

“…A recent investigation in Egypt revealed that its urban wastewater contains around 80, 33, 50, 67, and 50% higher concentrations of Mn, Cu, Zn, Fe, and Pb, respectively, compared to freshwater . Similarly, the wastewater concentrations of Cu, Zn, and Pb were nearly 35, 23, and 35% higher, respectively, compared to the groundwater . Another study showed that in Egypt, the Pb, Zn, and Cu levels in wastewater were more than 50, 77, and 82% higher compared to freshwater from the Nile River, respectively.…”

Toxic Heavy Metals in Soil and Plants from a Gold Mining Area, South Africa

“…The researchers concluded that the concentrations of heavy metals in plants were above the acceptable limits of Cd, 0.02 mg/kg, Pb, 2 mg/kg set by World Health organization (WHO). In the study by Kausar et al [45] high concentrations of Cd, Pb, and Zn were recorded in crops irrigated by heavy metal polluted water. The accumulation of Cd, Pb and Zn was recorded in the crops' leaves and root of carrot and spinach.…”

Effect of Seed Germination and Early Seedling Growth Response on Two Rice (Oryza sativa) Varieties Supplied with Different Types and Concentrations of Wastewater in Thailand

“…The treated wastewater contains nutrients such as nitrogen, phosphorus, potassium, and sulfur, which can easily be absorbed by plants [10]. Studies have demonstrated that paddy irrigated with wastewater results in higher yields and better vegetative growth compared to groundwater [11,12]. Additionally, paddy shoots that were treated with wastewater showed a higher concentration of essential nutrients [13].…”