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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 metal indicators of tap water overnight, grasp the characteristics of metal indicators in tap water overnight, evaluate the sanitary conditions of tap water overnight and guide residents to healthy drinking water. Methods The water of residential tap water was collected overnight. Water samples were collected at 0, 10 and 5 min after tap water was turned on, and 14 metal elements such as iron and zinc were detected. The test results were analyzed by SPSS 20.0 software, Results The failure rate of direct tap water (0 s) was 69.23% overnight. The four elements of Zn, Fe, Pb and Ni exceeded the national standards for drinking water; the failure rate of overnight tap water for 10 s was 19.23%; min overnight tap water failed rate of 7.69%. Using Friedman’s test to analyze each element (taking α = 0.05), the results showed that there were significant differences among the six elements of Cr Cu Zn Pb Ni Cd three time points (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). There was no significant difference in other items. Continue to compare these six elements by Wilcoxon method (take correction α ’= 0.017). The results showed that the results of three groups of Zn were statistically different; Cd 0 s ~ 5 min group was statistically significant; Cr, Cu, Pb, Ni 0 ~ 10 s no significant difference, the difference mainly in 0 s ~ 5 min, 10 s ~ 5 min comparison of time points. Conclusions Faucets and indoor plumbing can affect overnight water quality mainly due to the increase of the concentration of various metal elements. The impact of faucets is even more significant, which will cause a drastic drop in water quality and sanitation, which is not in conformity with the national drinking water standards. With the opening of the tap to increase the release of water, the health of the water quality will be improved. When the water is discharged to 10 s, there is no significant difference between the qualified rate of water quality and the water quality of the main network. However, the individual element concentration is still above the national standard or the level is higher. Drink the first 10 s overnight tap water.