Geochemical characteristics and utilization prospects of Zn in farmland soils, Jiangsu Province

Based on the geochemical data of farmland soils in Jiangsu Province, obtained from regional eco-geochemical surveys and the geochemical assessment of land quality in past years, this study delved into the geochemical characteristics of Zn in soils, aiming to explore the prospects of producing natural zinc-rich food in Zn-rich soils. The results indicate that Zn in farmland soils in Jiangsu Province exhibited an uneven distribution, with an average Zn content of approximately 70 mg/kg. The available Zn accounted for about 20% of the total Zn in soils. The total Zn in soils dictated the distribution of available Zn, with a significant positive correlation between both. Significant factors influencing the enrichment and distribution of Zn in soils included soil texture, genetic type, total organic carbon (TOC) content, and Fe content. Among various soils, limestone soils were the most enriched in Zn in Jiangsu Province, while the Holocene marine silty soils served as soil parent materials most enriched in Zn. Zn in soils manifested (relatively) significant positive correlations with Se, Cu, Fe, Al, Mo, and TOC contents. Rice seeds showed an average Zn content of 18 mg/kg, with an average bio-concentration factor (BCF) value of 0.2. Zn in rice seeds was significantly positively correlated with Zn, Se, and TOC content in soils but significantly negatively correlated with soil pH. In contrast, wheat seeds showed an average Zn content of 28 mg/kg, with an average BCF value of 0.36. Zn in wheat seeds was significantly positively correlated with Zn, Se, B, and TOC content in soils. Additionally, a significant positive correlation between Zn and Se was observed in both rice and wheat seeds. According to the industrial standards, the proportions of zinc-rich soils, zinc-rich rice seeds, and zinc-rich wheat seeds in Jiangsu Province were 11.39%, 29%, and 13.69% respectively, suggesting promising prospects for the development and utilization of zinc-rich soil resources in Jiangsu Province. The development and utilization efficiency of zinc-rich soil resources can be significantly enhanced by combining the production of natural zinc-rich food and the amelioration of farmland soils (e.g., improving TOC content and pH in soils). Overall, the results of this study provide a basis for scientifically utilizing beneficial trace elements such as Zn in soils in Jiangsu Province.