[Selenium Threshold for the Delimitation of Natural Selenium-Enriched Land].

The nationwide Se-enriched threshold plays a key role in identifying China's selenium-enriched land resources and developing characteristic agricultural practices. In this study, we used the cooperative data of 10222 sets of crops and roots in China for the past 10 years with a systematic analysis of the selenium content characteristics of the soil and the status of selenium-enriched agricultural products. The preliminary estimates of the selenium-enriched threshold based on a bulk crop-soil linear model and population selenium-intake are presented. Finally, a collaborative analysis model of soil selenium-enrichment rate and crop selenium-enrichment rate is established, coming up with the nationwide Se-enriched threshold:total selenium ≥ 0.40 μg·g in paddy soil, and total selenium ≥ 0.30 μg·g in dryland soil. The threshold passed the feasibility test in 13 provinces, providing strong support for the China Geological Survey to formulate and promulgate this technical standard for the delimitation of the natural selenium-enriched land.