一、病区水化学特征陕北黄龙、宜川两县是克山病、大骨节病重病区。区内分布有上三迭系砂页岩裂隙水和第四系冲积层孔隙潜水。水化学的基本特征是低矿化度、弱碱性水,pH值7.2～7.9,矿化度一般为0.2～0.5克/升,最大达1克/升左右,硬度一般为12德国度。γHCO_3>γ(Ca+Mg),只具暂时硬度,永久硬度为0。水中明显表现出低SO_4~(2-)、低 First, the ward chemical characteristics of water Huanglong in northern Shaanxi, Yichuan counties are Keshan disease, Kaschin-Beck disease area. There are sand fractures in Upper Triassic sandstone and pore water in Quaternary alluvium. The basic characteristics of water chemistry is low salinity, weak alkaline water, pH 7.2 to 7.9, salinity is generally 0.2 to 0.5 g / l, up to 1 g / l, the hardness is generally 12 degrees Germany. γHCO_3> γ (Ca + Mg), only a temporary hardness, permanent hardness of 0. Water obviously showed low SO 4 ~ (2-), low