Pb and Cr Content in an Agricultural Soil Irrigated with Wastewater and Their Bioaccumulation in Alfalfa

Urban wastewater contains various pollutants, with heavy metals being common, posing risks to the environment and public health, especially when used for irrigation in agricultural systems. This study aimed to assess the total and bioavailable content of Pb and Cr in agricultural soil irrigated with wastewater and their accumulation in alfalfa crops. Five alfalfa sites were sampled, and ten surface soil samples were collected from the top 30 cm of each plot. Plant samples were also collected at each sampling point. A composite sample of irrigation water from the main channels was also collected and prepared. The concentration of heavy metals was determined using atomic absorption spectrophotometry. The results revealed concentrations of Pb and Cr (VI) in the irrigation water above the maximum permissible limits according to environmental regulations. The soil had high organic matter content, neutral pH, elevated electrical conductivity (EC), and Pb and Cr contents of up to 103 and 89 mg/kg, respectively. In alfalfa tissues, Pb and Cr concentrations were recorded at 26 mg/kg and 4.6 mg/kg, respectively (Cr (VI), with lower concentrations observed in the roots. Cr (VI) was higher at all sites, with ranges from 2.25 to 43.56, while lead (Pb) had an AR ranging from 0.64 to 27.04. The Pb presented a mean of 1.45 of the Bioaccumulation factor values, which can be considered a metal-accumulating plant.