Sato Yoko, Ishihara Masayuki, Fukuda Koichi, Nakamura Shingo, Murakami Kaoru, Fujita Masanori, Yokoe Hidetaka
Division of Biomedical Engineering, Research Institute, National Defense Medical College.
Department of Oral and Maxillofacial Surgery, National Defense Medical College.
Biocontrol Sci. 2018;23(3):139-143. doi: 10.4265/bio.23.139.
Nitrate-nitrogen (NO-N) and nitrite-nitrogen (NO-N) are constituents of the nitrogen cycle. NO-N is toxic to humans, primarily due to its reduction to NO-N. In Japan, NO-N and NO-N levels in tap water must not exceed 10 mg/L and only NO-N alone not 0.04 mg/L, respectively. In this study, we verified the effect of microorganisms and ultraviolet (UV) to increase of NO-N in water. First, all tested drinking-waters including tap water and commercial mineral water in PET bottles had < 2 mg/L NO-N and undetectable levels (< 0.01 mg/L) of NO-N. However, we found that NO-N was generated in tap water left to stand at room temperature for several days, leading to increases in CF and TC counts and reduction of NO-N. We also demonstrated that direct UV and sunlight irradiation of NO-N-containing drinking water generated NO-N in 1-2 h, with NO-N reaching > 0.04 mg/mL by 4-6 h. On the other hand, NO-N and NO-N were undetectable in commercially purified water.
硝酸盐氮（NO₃-N）和亚硝酸盐氮（NO₂-N）是氮循环的组成部分。NO₂-N对人体有毒，主要是因为它会还原为NO₃-N。在日本，自来水中NO₃-N和NO₂-N的含量分别不得超过10毫克/升和仅NO₂-N不得超过0.04毫克/升。在本研究中，我们验证了微生物和紫外线（UV）对水中NO₂-N增加的影响。首先，所有测试的饮用水，包括自来水和PET瓶中的商业矿泉水，NO₃-N含量均<2毫克/升，NO₂-N含量未检出（<0.01毫克/升）。然而，我们发现，在室温下放置数天的自来水中会产生NO₂-N，导致CF和TC计数增加以及NO₃-N减少。我们还证明，对含NO₂-N的饮用水进行直接紫外线和阳光照射，1-2小时内会产生NO₃-N，4-6小时内NO₃-N含量会达到>0.04毫克/毫升。另一方面，在商业净化水中未检测到NO₃-N和NO₂-N。
