| With cropland filed and open vegetable fields as control, the experiment was carried out to study the change of contents of K, Na, Ca, Mg, Al, Fe, Mn, Cu, Cd, Cr, and Li in different layers (0～20, 20～40 cm) of greenhouse soils with six vegetable growing years (1, 4, 7, 11, 14 a, and 17 a) in northern Shanxi. The results indicated that K, Ca, Mg, Al, Cd and Li contents in greenhouse soils decreased during the first 4 years, then increased until 14th year, and decreased after that. Fe, Mn, Cu and Cr contents increased during the first four years, then decreased to the 11th year, and increased after that. The analysis of variance showed significant difference in minerals content of the same soil layer between different treatments. Contents of K, Na, Al, Fe, Mn, and Cu were higher than the natural background soil metal concentrations of northern Shanxi, whereas Ca and Mg showed no significant change. According to environmental quality standard for soil pollution, the contention of Cd, Cu, and Cr fell into the allowable range, while that of Cd was above the upper limit. In addition, Cd was within the range of 0.28～0.56 mg·kg-1, nearly approaching to the maximum threshold. |