Soil nitrate is important for crop growth, but it can also leach to groundwater causing nitrate contamination, a threat to human health. Here, we report a significant accumulation of soil nitrate in Chinese semi-humid croplands based upon more than 7000 samples from 141 sites collected from 1994 to 2015. In the 0–4 meters depth of soil, total nitrate accumulation reaches 453 ± 39, 749 ± 75, 1191 ± 89, 1269 ± 114, 2155 ± 330 kg N ha−1 on average in wheat, maize, open-field vegetables (OFV), solar plastic-roofed greenhouse vegetables (GHV) and orchard fields, respectively. Surprisingly, there is also a comparable amount of nitrate accumulated in the vadose-zone deeper than 4 meters. Over-use of N fertilizer (and/or manure) and a declining groundwater table are the major causes for this huge nitrate reservoir in the vadose-zone of semi-humid croplands, where the nitrate cannot be denitrified due to the presence of oxygen and lack of carbon sources. Future climatic change with more extreme rainfall events would increase the risk of accumulated nitrate moving downwards and threatening groundwater nitrate contamination.

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A double-blind, randomized, controlled trial involving 706 adults was conducted to evaluate the immunogenicity and safety of different dosages of whole-virion or split-virion H1N1 influenza vaccines with or without aluminum adjuvant. A rapid and strong immune response was induced at day 14 after the first injection. The seroprotection rates ranged from 72.7% (95% confidence interval [CI], 62.7%-81.1%) for 5-microg whole-virion aluminum formulation to 97.0% (95% CI, 90.9%-99.7%) for 30-microg split-virion nonaluminum formulation. All formulations were well tolerated. The incidences of mild, moderate, and severe reactions were 71 (10.1%), 15 (2.1%), and 1 (0.1%) of 706 reactions, respectively. The 15-microg split-virion formulation had the best immunogenicity and safety.

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