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To analyze the influencing factors of karstification and karst carbon cycle, a simulation experiment was carried out and 6 soil columns were designed. The results showed that the content of H2O4, hydrodynamic condition and thickness of the soil had important influence on karstification and karst carbon cycle. For the soil columns which were covered by the same thickness of soil, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B20-2 > B20-1 > B20-3, B50-2 > B50-1 > B50-3. This meant that input of H2SO4 enhanced the karstification and increasing infiltration water had significant dilution effect on the chemical properties. For the soil columns with different thickness of soil but with the same slag pile and hydrodynamic conditions, the concentrations of Ca2+ + Mg2+ and SO4(2-) followed the order of B50-1 > B20-1, B50-2 > B20-2, B50-3 > B20-3. It was demonstrated that more carbonate rock was dissolved under the thick soil columns. In addition, the net consumption of CO2 mainly depended on the content of H2SO4 in this experiment due to slight contribution of H2CO3 to carbonate rock dissolution. More content of H2SO4 brought about less net consumption of C02, but B50-2 was an exception. Organic matter and other nutrients might be input into deep soil with the slag pile, and they promoted the production of soil C)2. Therefore, more CO2 was consumed due to the increased contribution of H2CO to karstification.

Objective: To study the association between vitamin D status and bone mineral density(BMD) in urban postmenopausal women in Beijing., Methods: A total of 400 community-dwelling women older than 60 (median age 67.8 years) were selected randomly from 17 community of 3 districts in Beijing by cluster sampling method from May to July, 2008. Serum 25(OH)D concentrations were measured by radioimmunoassay, using the DiaSorin kit, America. The objects were assigned into four groups: vitamin D deficient group (group A, 25(OH)D < 25 nmol/L), insufficient group(group B, 25 nmol/L < 25(OH)D < or = 50 nmol/L), normal group (group C, 50 nmol/L < 25(OH)D < or = 75 nmol/L) and enough group (group D, 25(OH)D > 75 nmol/L). The BMD at total, lumbar spine (L(2-4)) and proximal femur were measured by dual-energy X-ray absorptiometry (DEXA)., Results: The mean concentration of serum 25(OH)D concentration was (36.0 +/- 14.6) nmol/L, BMD at total and proximal femur were respectively (0.829 +/- 0.090) and (0.679 +/- 0.106) g/cm(2). The mean BMD at total of group A, B, C + D were respectively (0.811 +/- 0.077), (0.825 +/- 0.088) and (0.864 +/- 0.112) g/cm(2)(F = 16.93, P < 0.01), and BMD at proximal femur of group A, B, C + D were respectively (0.666 +/- 0.107), (0.673 +/- 0.099) and (0.725 +/- 0.117) g/cm(2)(F = 18.36, P < 0.01). The 25(OH)D level was positively correlated with BMD at total body and proximal femur (r values were 0.17 and 0.18, both P values < 0.05)., Conclusion: Vitamin D status was highly correlated with BMD at lumbar spine (L(2-4)), proximal femur, pelvis and limbs for the postmenopausal older women.