[Simulation of the Migration and Leaching of Nitrate Nitrogen in the Farmland Soil Profile in a Hilly Area of Taihang Mountain with the RZWQM Model].

Taihang Mountain region is the recharge area for groundwater in the North China Plain (NCP). In recent years, the elevated nitrate concentration in the groundwater in the Taihang Mountain has often been associated with the increased area of farmland and the excessive application of nitrogen. Thus, it is significant to study the soil nitrogen leaching process in typical farmland. In this study, the root zone water quality model (RZWQM) was used to simulate the nitrate nitrogen leaching of winter wheat/summer maize rotation systems in the Hilly Ecosystem Experimental Station in Taihang Mountain. The results showed that during the 2015-2016 winter wheat/summer maize season, the nitrate nitrogen from the soil leaching occurred mainly in the summer maize season (rainy season), with the nitrate nitrogen leaching amount reaching 59.9 kg·hm-2, while the nitrate nitrogen leaching amount during the winter wheat season was only 2.12 kg·hm-2. The soil nitrate nitrogen leaching condition was simulated using the RZWQM model for different nitrogen contents and years with different rainfall. Significant linear correlations were observed between nitrogen use and nitrate leaching in winter wheat/summer maize rotation systems. In summary, the results showed that the nitrate nitrogen leaching values were 10.5, 59.9, and 136.5 kg·hm-2 for nitrogen fertilizer applications of 0, 300, and 450 kg·hm-2, respectively, during extreme precipitation in a wet year (2015). The value of nitrate nitrogen leaching in the maize season of 2013 (dry year), 2015 (normal year), and 2016 (wet year) accounted for 9%, 10%, and 20% for the 300 kg·hm-2 of nitrogen fertilizer applied, respectively. However, the value of nitrate nitrogen leaching in the maize season of 2013 (dry year), 2015 (normal year), and 2016 (wet year) accounted for 11%, 17% and 30% of the 450 kg·hm-2 of nitrogen fertilizer applied. These results show that extreme precipitation events not only greatly recharge the groundwater, but also increase the leaching of accumulated nitrate nitrogen and potential nitrate contamination in the groundwater.

Effect of grape procyanidins on tumor angiogenesis in liver cancer xenograft models.

BACKGROUND: In recent years a wide variety of flavonoids or polyphenolic substances have been reported to possess substantial anti-carcinogenic and antimutagenic activities. Grape proanthocyanidins (GPC) are considered as good examples for which there is evidence of potential roles as anti-carcinogenic agents. METHODS: A xenograft model was established using H22 cells subcutaneously injected into mice and used to assess different concentrations of grape proanthocyanidins (GPC) and Endostar. Treatments were maintained for 10 days, then levels of vascular endothelial growth factor (VEGF) and microvessel density (MVD) were examined by immunohistochemistry, while VEGF mRNA was determined by real-time PCR in tumor tissue. RESULTS: The expression of MVD and VEGF decreased gradually as the concentration of GPC increased.There was a significant positive correlation between MVD and VEGF. CONCLUSIONS: These results suggest that GPC restrains the growth of tumor, possibly by inhibiting tumour angiogenesis.