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Abstract：
A nationwide survey of inorganic components of tap water all over Japan was conducted from 2019 to 2024. In this survey, 1564 tap water samples were collected, and an additional 194 tap water samples were collected from 33 other countries. The water samples were analyzed for 27 dissolved inorganic components, with a primary focus on the distribution of major and trace components, including Ca, Mg, K, Na, Cl-, NO3-, SO42-, total-hardness, Al, Fe, Cu, Mn, and Zn. The Japanese tap water hardness was 50.5 ± 30.2 (± 1σ SD) mg/L, classified as soft water according to the World Health Organization (WHO) classification. The average content of each major component in Japanese tap water tended to be lower than those in other countries. Furthermore, Piper trilinear diagrams were used to categorize Japanese tap water types. The dominating water types were the Ca-HCO3 and mixed types, which had a nationwide distribution. Japanese tap water generally complied with Japanese and WHO drinking water criteria, with only 1% (17/1564 sites) of the samples exceeding water quality standards. Observations of water quality changes for 2 years at three household faucets revealed that fluctuations in major components and trace metals (Al, Fe, Cu, Mn, and Zn) varied in different patterns. This suggests that the behavior of trace metal elements is influenced by local infrastructure, such as supply pipes, distinct from the variability in source water quality.
摘要：
从2019年到2024年，在日本全国范围内对自来水中的无机成分进行了调查。在这次调查中,收集了1564个自来水样本，并从其他33个国家收集了另外194个自来水样本。水样分析了27种溶解的无机成分，主要关注主要成分和微量成分的分布，包括Ca,Mg,K,Na,Cl-,NO3-,SO42-,总硬度,Al,Fe,Cu,Mn,和Zn。日本自来水硬度为50.5±30.2(±1σSD)mg/L,根据世界卫生组织（WHO）的分类被归类为软水。日本自来水中各主要成分的平均含量往往低于其他国家。此外，Piper三线性图用于对日本自来水类型进行分类。主要的水类型是Ca-HCO3和混合类型，在全国范围内发行。日本自来水一般符合日本和世卫组织的饮用水标准，只有1%(17/1564个地点)的样本超过水质标准。对三个家用水龙头的水质变化进行了2年的观察，结果表明主要成分和痕量金属（Al，Fe,Cu,Mn,和Zn)以不同的模式变化。这表明痕量金属元素的行为受到当地基础设施的影响，如供应管道，与水源水质的变异性不同。
