Study of the heavy metals concentration in the fresh leaves of tea and the tea fields topsoil (Study area; Fooman County)

Tea is not only known as one of the most common beverages in the world but also as a quite favorable and frequently consumed drink in Iran. Accordingly, studying the fresh tea leaves’ heavy metal content is an area of attention considering the environment quality assessment in addition to the public health issues. The research aimed at determining the concentration of heavy metals including lead, cadmium, zinc, nickel, cobalt, and chromium in the fresh leaves of tea and topsoils of the tea fields in Fouman County, Guilan, Iran. To do so, tea fresh leaves and respective topsoils were sampled at 5 sampling sites. After initial preparation, digestion of the taken samples was performed using HCl, HNO3, and H2O2 reagents. The concentration of heavy elements in the samples was determined by inductively coupled plasma (ICP). There have also been statistical tests such as one-way analysis of variance, T-test, principal component analysis (PCA) and cluster analysis (CA) performed using the SPSS software. Based on the results, the average concentrations of lead, cadmium, zinc, nickel, cobalt, and chromium in soil samples were obtained 3.94, 1.06, 60.29, 22.79, 9.49, and 2.77, mg/kg, respectively. According to the metal pollution load index (0<1), the soil quality of the study area was identified at an acceptable level. The levels of lead, cadmium, zinc, nickel, cobalt, and chromium in fresh leaves were obtained 0.44, 0.08, 22.58, 9.93, 0.23, and 0.36 mg/kg, respectively. Compared to the international standards (WHO / FAO), the amount of lead in fresh leaves was higher than permissible levels. By contrast, the amounts of cadmium, zinc, nickel, cobalt, and chromium were at acceptable values. As for soil samples, only the concentration of cadmium was higher than admissible levels based on the given standards. As such, the leaching process and biological uptake (happened by the rest of the flora) should have a part to play justifying the former results.