家用鹅颈水龙头和供水管道中隔夜自来水中14种金属指标变化特征

Variations of 14 metallic elements in over-night drinking water stagnated in household curved taps and branch pipes

目的通过对隔夜自来水金属指标进行检测分析,掌握隔夜自来水中金属指标变化特征,评估隔夜自来水水质的卫生状况,指导居民健康饮水。方法对居民自来水隔夜潴留水进行采集,在打开龙头放水0、10 s和5 min 3个时间点采水样,进行铁、锌等14种金属元素检测,检测结果用SPSS 20.0软件进行统计分析,结果直接接取(0 s)的隔夜自来水不合格率为69.23%,Zn、Fe、Pb、Ni 4种元素超过国家饮用水卫生标准;放水10 s的隔夜自来水不合格率为19.23%;放水5 min的隔夜自来水不合格率为7.69%。运用Friedman检验对各元素进行分析(取α=0.05),显示Cr Cu Zn Pb Ni Cd 6种元素3个时间点水样浓度差异具有统计学意义(Crχ2=14.769,P<0.01,Cuχ2=25.154,P<0.01,Znχ2=36.077,P<0.01,Pbχ2=18.583,P<0.01,Niχ2=29.255,P<0.01,Cdχ2=15.469,P<0.01),其余项目差异无统计学意义。继续对这6种元素用Wilcoxon法做两两比较(取校正α’=0.017)。结果显示,Zn的3组结果均有统计学差异;Cd的0 s^5 min组有统计学差异;Cr、Cu、Pb、Ni的0~10 s差异无统计学差异,差异主要出现在0 s^5 min、10 s^5 min时间点的比较。结论水龙头和住户室内管道均可对隔夜水水质造成影响,主要体现在多种金属元素浓度升高,而水龙头的影响更为显著,会使水质卫生状况急剧下降,不符合国家饮用水卫生标准。随着打开龙头放水时间的增加,水质卫生情况随之好转,放水至10 s时,水质合格率与主管网水质无统计学差异,但个别元素浓度仍超出国家标准或水平较高,建议居民不要饮用最初的10 s隔夜自来水。

[Objective] To detect and analyze the metallic elements in over-night drinking water, know their variation characteristics, evaluate the sanitary condition of over-night drinking water, and give a healthy drinking suggestion to citizens. [Methods]The samples of over-night drinking water were collected from households at three time points of 0 seconds, 10 seconds and 5 minutes after opening taps. 14 metallic elements （including Fe and Zn, etc.） were detected in water samples, and the results were statistically analyzed with SPSS 20.0 software. I Results jThe unqualified rate of first water samples （0 seconds） was 69.23%, and the concentrations of Zn, Fe, Pb and Ni were higher than the national health standard. The unqualified rate of water samples of 10 seconds and 5 minutes after opening taps was 19.23% and 7.69% respectively. The Friedman test was used to analyze each element （α=0.05）, the results showed there were statistically significant differences in the concentrations of Cr, Cu, Zn, Pb, Ni and Cd among three time points （Cr x^2=14.769, P〈0.01 ,Cu x^2=25.154,P〈0.01 ,Zn x^2=36.077, P〈0.01 ,Pb x^2=18.583,P〈0.01, Ni x^2=29.255, P〈0.01 ,Cd x^2=15.469, P〈0.01）, and differences in other elements were not statistically significant. The Wilcoxon test was used to compare the differences between any two time points of six elements （adjust α=0.017）. The results showed the concentration of Zn had the statistically significant differences in every pair of the three time points, while Cd had difference in 0 s-5 rain pair, and there were no statistically significant differences in 10 s-5 min pairs of Cr, Cu, Pb and Ni. The differences were mainly found in 0 s-5 rain pairs and 10 s-5 rain pairs. [Conclusion]The taps and pipes of household can influence the quality of over-night drinking water by rising the concentrations of some metallic elements, especially taps, which reduce the sanitary conditions of drinking water, and the water quality can not meet the national health standard of drinking water. With the increasing of water flowing time, the sanitary quality is getting better. After 10 seconds flowing, the water qualified rate has no statistical difference from that in main water supply pipes, but the concentrations of some elements are still higher than the limits. It is suggested that the over-night water flowing from the taps at the first 10 second should not be used for drinking.