Heavy Metal Transport in Different Drip-Irrigated Soil Types with Potato Crop

Abstract

Heavy metal (HM)-polluted soil is a serious concern, especially as brackish water is widely used for irrigation purposes in water-scarce countries. In this study, the HYDRUS-2D model was used to simulate HM (copper (Cu), lead (Pb), and zinc (Zn)) transport through agricultural land cultivated with potato crops under surface drip irrigation to explore the potential groundwater contamination risk. Three soil types, namely, silty clay loam, sandy loam, and sandy soil, and two irrigation schemes, irrigation every two days (scheme A) and irrigation every four days (scheme B), were considered during the simulations. Firstly, the ability of HYDRUS-2D to simulate water flow was validated using data obtained from a full growing season of the potato crop in a lysimeter irrigated by surface drip irrigation using El-Salam Canal water, Egypt (i.e., water contaminated by HMs). Secondly, the model was calibrated for solute transport parameters. After that, the investigated simulation scenarios were executed. The results showed that HYDRUS-2D effectively simulated water flow. Moreover, a good agreement between the simulations and experimental results of HM concentrations under the calibrated solute parameters was obtained with R2 values of 0.99, 0.91, and 0.71 for Cu, Pb, and Zn concentrations, respectively. HM distribution is considerably influenced by the HMs’ adsorption isotherm. The results of the investigated scenarios reveal that soil texture has a greater impact on HM concentrations in the simulation domain and on the contamination risk of the groundwater than the irrigation scheme. Under both irrigation schemes, lower HM concentrations were observed in sand, while higher values were observed in silty clay loam. Subsequently, the potential shallow groundwater contamination risk is greater when cultivating potatoes in sand, as higher HM concentrations were found in drainage water compared to the two other investigated soils, regardless of the irrigation scheme. The cumulative Cu, Pb, and Zn concentrations in drainage water corresponding to scheme A for silty clay loam and sandy loam were 1.65, 1.67, and 1.67 and 1.15, 1.14, and 1.15 times higher, respectively, than scheme B. To safeguard the sustainability of groundwater and agricultural lands irrigated with water contaminated by HMs, it is recommended to adopt an irrigation frequency of once every four days in soils with silty clay loam and sandy loam textures.