Heavy metal concentration in water, soil and cultivated vegetables at the edge of Kashaf Roud River, Mashhad, Iran: ecological risk assessment and bioaccumulation factor

Abstract

ABSTRACT The entrance of heavy metals through human activities causes pollution of water, soil, and plants. The aim of this study was to measure the heavy metals concentration (Hg, Pb, As, and Cd) and their ecological impacts on water, soil, and vegetables in the Kashaf Roud River basin. Hence, 72 samples of irrigation water, 72 samples of soils, and 216 samples of vegetables (dill, leek, and basil) were collected. The contamination levels were evaluated by several ecological indices including Ecological Risks index (ERI), Heavy Metal Evaluation Index (HEI), Contamination factor (Cf), Pollution Index (PI), geo-accumulation index (Igeo), Potential ecological risk index (RI), Pollution load index (PLI), and modified degree of contamination (MDC). Based on obtained results, concentrations of heavy metals in water and soil samples were in the order of Pb>As>Cd>Hg. In addition, Pb and As had the highest concentration in vegetables with the mean total concentrations of 1.60 and 0.08 mgkg−1 wet weight, respectively. According to ERI value (238), water sampling site no. 3 had higher pollution than other places and was classified in the considerable ecological risk. Among the soil samples, the Cf average values followed the declining order of Cd (7.78)>Pb (6.91)>Hg (4.26)>As (2.68), so that Pb and Cd presented high contamination levels. Moreover, all soil samples of the studied region possessed PLI>1, which confirms their contamination with heavy metals. Finally, the trends in the BAF values for heavy metals in various vegetables were in order of Hg>Cd≈Pb>As for Leek and Hg>As> Pb>Cd for Dill and Basil. Concentrations of heavy metals in soil and water samples were within the national and international standard ranges. However, the concentrations of these metals in some vegetable samples exceeded the national and international levels. The utilisation of standard quality effluent for agricultural irrigation requires control measures and good organisational performance.