Study On The Safe Utilization Of Selenium-rich Land Resources In Shadi County,Enshi City,Hubei Province

Selenium is one of the essential trace elements for human,and lack or excessive intake of selenium will adversely affect human health.Enshi located in Hubei Province is China's selenium capital,with unique selenium-enriched land resources while high cadmium soils were widely distributed.Samples of soil and crops were systematically collected and analyzed in Shadi Township,a typical area of Enshi.The concentrations of selenium and heavy metal elements in soil and their distribution,the origin of selenium and cadmium and the c concentrations of selenium and heavy metals in crops were identified.A set of safe utilization model for selenium-rich land utilization in high-selenium and high-cadmium area has been established.The results were listed as follows:(1)The soil selenium concentrations in the study area was high,whose average value was significantly higher than those in Hubei Province and China.However,he soil selenium concentrations with the distribution ratio of 15.58% was excessive,which meant the risk of selenium poisoning.The spatial variability of soil selenium was strong which was mainly controlled by the Permian Maokou formation.Soil organic carbon concentrations and the altitude were the important factors affecting the selenium concentrations in soil.(2)The concentrations of cadmium were higher while the concentrations of other heavy metal elements were lower in the study area.It was indicated that the concentrations of heavy metals as Cr,Ni,Zn,Cd,Hg and Cu were controlled by the Se-rich black rock series.The characteristic that soil selenium was rich with cadmium in the study area was inherited from the geological background.Soil Pb,As concentrations may be affected by anthropological factors.(3)The results of crop safety evaluation showed that the number of se-rich maize seed samples accounted for 43% of the total while potentially selenium deficient samples accounted for 48% of the total.Se excessive samples accounted for 9% of the total.For the heavy metal elements,42% of the samples exceeded the safe food standard of cadmium,while the some samples exceeded the safe food standard of Pb and Hg.The concentrations of Se in maize seeds were obviously affected by the concentrations of aluminum oxide,copper,zinc,cadmium and selenium in soil.Based on the prediction model of selenium concentrations in maize seeds,the results showed that the concentrations of selenium in maize seeds varies greatly,and the proportion of se-rich crops was 43%.(4)The result of land evaluation of mountainous region showed that the best grade area of mountainous region was about 203 ha,accounting for 3% of the total;the common grade area was about 2708 ha,accounting for 40% of the total;the worst grade area was about 3859 ha,accounting for 57% of the total.(5)The zonation of crops showed that the area of A grade area was about 1625 ha,accounting for 24% of the total;the area of B grade area was about 812 ha,accounting for 12% of the total;the area of C grade area was about 16 ha,accounting for 0.23% of the total;D grade area was about 4353 ha,accounting for 64.30% of the total.