Abstract:

In order to study the biological and geochemical laws of Se element, we made use of Se element in the farmland ecosystem of Poyang Lake Basin, Jiangxi Province as the main subject studied, using atmospheric bulk deposition, irrigation, fertilization and pesticide spray as input parameter, and crop harvest, surface runoff and sublimation of Se element as output parameter. The study shows that the average value of atmospheric bulk deposition flux density of Se element in Poyang Lake Basin is 6.90 g/（hm2·a）, while the values of irrigation flux density, fertilization flux density and pesticide spray flux density are obviously low, and their corresponding contribution rates to the enrichment of edaphic Se element are 77%, 20%,1% and 2%, respectively. The sublimation of Se element flux density output value is relatively small and the annual net increment values of edaphic Se element are majorly affected by the constraints of atmospheric bulk deposition. It is estimated that the current average annual Se element flux density can cause edaphic Se concentration increased by 0.007 mg/kg, and accordingly, the enriched Se element soil of the study area will increase from 5960 km2 to 6672 km2 in 20 years. This study does not take the infiltration of rain water into consideration, which has a vital influence on the geochemical behavior of elements in southern China soil.

Key words: flux density, Se element, farmland ecosystem, Poyang Lake Basin, Jiangxi Province