ABSTRACT
Objective To study the variations of the contents of trace elements in first section of tap water stagnating in pipe over night. Methods The first and middle sections of tap water stagnating in galvanized iron pipe for water supply over night for about 10 hours flowing through an iron tap and a chromed tap were sampled and determined for the contents of copper, manganese, iron and zinc by atomic spectrophotometry. The relationship between the variations of contents of four elements and the flow capacity was analyzed also. Results The contents of copper and manganese in the first section and middle section of tap water stagnating in pipe over night accorded with the sanitary standard for drinking water (SSDW), and revealed no significant differences between the first and middle section of tap water. The contents of iron in first section of tap water flowing through an iron tap and the contents of zinc in first section of tap water flowing through a chromed tap both exceeded the SSDW and revealed higher levels respectively compared with those in the related middle section of tap water. The levels of iron and zinc negatively correlated with the flow capacity (r Zn=-0.938,P