Influence of soil characteristics on the concentrations of Cr, Pb, and Zn in tobacco leaves from Longyan, China, and the associated predictive models

Abstract In Longyan City, Fujian Province, a hub for premium tobacco in China, our study explored the connection between soil properties and heavy metal levels in tobacco leaves, focusing on chromium (Cr), lead (Pb), and zinc (Zn). We observed that the soil's average concentrations for Cr, Pb, and Zn were 0.165, 9.53, and 5.17 mg/kg, respectively. In stark contrast, tobacco leaves presented elevated mean concentrations of these metals, measuring 0.936, 2.19, and 102 mg/kg for Cr, Pb, and Zn, respectively. This disparity was further highlighted by the soil's exceedance rates for Pb and Zn at 2.93% and 0.472%, and the significantly higher enrichment coefficients in tobacco, 23.1 for Pb and 19.7 for Zn, compared to Cr, suggesting a substantial health risk. Our study identified critical soil parameters, including pH, organic matter, and levels of available potassium and phosphorus, as influential factors determining heavy metal content in tobacco. Utilizing these findings, we formulated predictive regression models for estimating Cr, Pb, and Zn concentrations in tobacco leaves. The regression models for estimating the concentrations of chromium, lead, and zinc in tobacco leaves are as detailed below: YCr = 0.889 + 0.001 * XK + 0.001 * XN - 0.005 * XOM + 0.101 * XCr (R2 = 0.852), YPb = 2.608 - 0.069 * XpH - 0.001 * XN + 0.008 * XZn + 0.01 * XPb (R2 = 0.738) and YZn = 101.892 - 0.141 * XP + 0.32 * XOM - 0.123 * XPb + 0.614 * XZn (R2 = 0.801), respectively. These offering essential tools for assessing and controlling heavy metal risks in tobacco cultivation within the region.