Regional wheat grain manganese and its potential risks affected by soil pH and precipitation

Abstract

Neurotoxicant exposure by the over intake of manganese (Mn) and crop Mn accumulation related with fertilization and other agronomical measures had attracted wide attentions, while information is limited about variations in grain Mn with geographical changes in both soil and precipitation. A total of 438 wheat-grain site samples were therefore collected from two regions that were categorized by soil pH (non-acidic, pH > 7 and acidic, pH < 7) across the major Chinese wheat production areas, to determine the distribution of grain Mn, the potential Mn risk and the rational grain Mn concentration to human health. Results showed that grain Mn ranged from 13.9 to 98.3 mg kg−1, with an average of 43.7 mg kg−1. On the one hand, soil pH in the acidic region had significantly negative, while annual precipitation had positive influence on grain Mn due to their different effects on soil DTPA-Mn. On the other hand, grain Mn in the non-acidic region insignificantly correlated with soil pH or soil DTPA-Mn, but negatively correlated with annual precipitation. In addition, the yield-dilution effect was not observed in this present study. Simulating assessment showed that long-term consumption of whole wheat grains with high Mn concentrations could cause potential hazards to children, and the upper limits of the daily whole grain Mn intake for local residents at different ages were also recommended. Results from this study could provide insight into rational strategies to curb Mn toxicity to human beings in wheat production areas around the world.