Abstract：
Water quality deterioration often occurs in secondary water supply systems (SWSSs), and increased heavy metal concentrations can be a serious problem. In this survey, twelve residential neighborhoods were selected to investigate the influence of SWSSs on the seasonal changes in heavy metal concentrations from input water to tank and tap water. The concentrations of nine evaluated heavy metals in all groups of water samples were found to be far below the specified standard levels in China. The concentrations of Fe, Mn, and Zn increased significantly from the input water samples to the tank and tap water samples in spring and summer (p < 0.05), especially for the water samples that had been stagnant for a long time. Negative correlations were found between most of the heavy metals and residual chlorine (Fe, Cu, Zn, and As, r = -0.186 to -0.519, p < 0.05). In particular, a high negative correlation was observed between Fe and residual chlorine (r = -0.489 to -0.519, p < 0.01) in spring and summer. Fe and Mn displayed positive correlations with turbidity (r = 0.672 and 0.328, respectively; p < 0.05). In addition, Cr and As were found to be positively associated with some nutrients (NO3-, TN, and SO42-; r = 0.420-0.786, p < 0.01). The material of the storage tanks had little influence on the difference in heavy metal concentrations. Overall, this survey illustrated that SWSSs may pose a chronic threat to water quality and could provide useful information for practitioners.
摘要：
水质恶化经常发生在二次供水系统(SWSS)中，和增加重金属浓度可能是一个严重的问题。在这次调查中,选择了十二个居民区来研究SWSS对从输入水到水箱和自来水的重金属浓度的季节性变化的影响。发现所有组水样中9种评估的重金属的浓度远低于中国规定的标准水平。铁的浓度，Mn,在春季和夏季，从输入水样到水箱和自来水样品中的Zn显着增加（p<0.05），特别是对于长期停滞的水样。大多数重金属与余氯(Fe，Cu,Zn,和作为,r=-0.186至-0.519，p<0.05)。特别是,在春季和夏季，铁与余氯之间呈高度负相关（r=-0.489至-0.519，p<0.01）。Fe和Mn与浊度呈正相关(r=0.672和0.328;p<0.05)。此外,发现Cr和As与某些营养素呈正相关(NO3-，TN,和SO42-；r=0.420-0.786，p<0.01）。储罐的材料对重金属浓度的差异影响很小。总的来说,这项调查表明，SWSS可能对水质构成长期威胁，并可以为从业人员提供有用的信息。
