Abstract:

Everything on Earth, living or non-living, is made from one or a combination of the 92 naturally occurring chemical elements. Life survival depends on the bioavailability of these essential elements at appropriate concentrations and proportions. A comparison between the element concentration in human blood and the corresponding baseline element concentration in arable soil shows a very good correlation for 40-50 key elements. The essential element selenium (Se) has a dual character, that both Sn deficiency and excess are harmful for human health. Previous researches concluded that Se deficiency was predominant in China. In this work, we collected the China geochemical baseline data from 3382 grid sampling sites covering the entire country. We found the proportion of Se deficient area to be 21.1% according to the WHO limit (0.1 mg/kg) or 31.6% by the Chinese guideline standard (0.125 mg/kg). The Se-deficient regions are distributed in Tibet and Inner Mongolia where grain crops are scarcely produced. No Se deficiency is observed in the arable plains of the 9 major grain producing regions except the Hetao plain. Specifically, Selenium is enriched (>0.4 mg/kg) in the Pearl delta, Guangxi, Chengdu, and middle and lower Yangtze plains; between marginal and appropriate levels (0.125-0.4 mg/kg) in the Sanjiang, Northern, Northeastern and Guanzhong (Central Shaanxi) plains; and deficient (<0.125 mg/kg) in the Hetao plain. The study shows that the spatial distribution of Se-poor soils is geographically situated in a discrete NE-SW-trending belt from the eastern part of Inner Mongolia to the Qinghai-Tibet Plateau, controlled mainly by geological background, parent rocks, soil types and geographical landscapes.

Key words: critical elements, human health, selenium concentration, spatial distribution, arable soils, China