The Bio-Availability and Accumulation of the Trace Elements in Rock-Soil-fruit System in Carbonatite Regions of Different Stratums: Critical Soil Factors and Transfer Models

For exploring the key factors affecting trace element accumulation in crops in limestone soil derived from limestone area of different stratums, the loquat (Eriobotrya japonica Lindl.) orchard of three limestone units (Middle Devonian, Upper Devonian and Middle Cambrian) in Mengzi city of Yunnan Province, China were investigated. Loquat fruits grown on soil from Middle Devonian limestone exhibited significantly higher bio-enrichment in cadmium. The Middle Devonian (Chemical Index of Alteration [CIA] = 86.07) and Upper Devonian (CIA = 84.84) soils were more weathered than those derived from Middle Cambrian rocks (CIA = 74.42). In the Middle Devonian limestone area, Fe element (for As uptake into fruit), Al element (for Cu and Zn) and metal speciation (for Cd, extracted by diethylene triamine pentaacetic acid) in the soil were the important influencing factors. For the Upper Devonian, soil weathering was found to be the key factors controlling fruit Cu uptake, respectively. For the Middle-Cambrian-derived soils, soil Ca concentration and pH played a critical role in Cd accumulation in fruit. In conclusion, under acidic soil conditions derived from limestone, the Ca concentration and metal fraction in the soil are the pivotal factors affecting Cd accumulation of fruit, whereas the soil Fe element content control the fruit As and Pb uptake. These results are helpful to further understand the migration regularity of trace elements into fruit in different limestone geology types.