The influences of soil properties on Cu and Zn availability in soil and their transfer to wheat (Triticum aestivum L.) in the Yangtze River delta region, China

A regional scale survey investigated accumulation of Cu and Zn in wheat and agricultural soil from the Yangtze River delta region, China. A total of 126 pairs of topsoil and wheat samples were collected to analyze Cu, Zn and relevant parameters. 7.9% and 21.4% of the wheat grain samples exceed Chinese maximum permitted concentrations of Cu and Zn in wheat grain (Cu: 10 mg kg− 1, Zn: 50 mg kg− 1), respectively. Cu had the highest accumulation in wheat straw, whereas Zn showed the highest accumulation in grain. The translocation from root to straw was the key link in the whole Cu transfer process in the soil–wheat system, and the average transfer coefficient was 1.244. For the whole Zn transfer process, the key link was the translocation from straw to grain, and the average transfer coefficient was 1.764. The spatial distributions of Cu and Zn accumulation in wheat grain did not exactly correspond to those in the soil. Among the soil parameters, soil pH was the most important factor in grain Cu or Zn accumulation apart from the concentrations of the heavy metal themselves. S and Fe had significant influences on Cu and Zn accumulation in the wheat grain. Besides Cu, Zn and co-transporter (S and Fe) imported from the soil, S present in atmosphere may also play an important role in wheat grain Cu and Zn accumulation, as S can provide conjunct ions and co-transporters for Cu and Zn in the soil–wheat system.

► Cu and Zn had the highest accumulation in wheat straw and grain, respectively. ► The spatial distribution of Cu and Zn are different between wheat and soil. ► Soil pH is the most important factor affecting the uptake of Cu and Zn by wheat. ► S and Fe have close associations with wheat Cu and Zn concentrations. ► S in atmosphere may play an important role in wheat grain Cu and Zn accumulation.