摘要：
目的 研究自来水在不同加热方式下余氯及亚硝酸盐含量的变化, 为人们日常健康饮水提供理论依据.方法 根据国家标准GB 5750.5-2006和GB 5750.11-2006, 对管网末梢水在经过不同煮沸时间、不同煮沸次数、煮沸后不同放置时间以及自动开水器及家用电水煲烧开的水中的余氯和亚硝酸盐含量进行检测.结果 市政自来水中余氯含量为0.25 mg/L, 亚硝酸盐含量未检出.自来水在煮沸1 min之后余氯含量未检出,而用家用电水煲烧开的水中余氯为0.1 mg/L, 煮沸1 h, 含量达到3.80 μg/L, 在国家标准限值之下.开水放置24 h亚硝酸盐含量达2.37 μg/L, 继续加热1 min后, 含量再次升高达2.76 μg/L.自来水反复煮沸8次后, 亚硝酸盐含量达3.38 μg/L.自动开水器烧开的自来水中余氯上午偏高, 早上和晚上则未检出; 亚硝酸盐含量在上午和晚上偏低, 在早上含量明显升高.结论 市政自来水通过加热, 较高的余氯迅速挥发减少, 而亚硝酸盐含量则会增加.家用电水煲开水中余氯残留较多, 在使用家用电水煲时, 建议电水煲断电后再开盖烧1 min.取公共场所自动开水器的水时, 尽量避免在用水高峰时取水.%Objective To evaluate the changes of residual chlorine and nitrite in tap water which was boiled through different ways, in order to give a healthy drinking guidance. Methods The residual chlorine and nitrite in the water were detected according to the national standard detection methods (GB 5750.5-2006 and GB 5750.11-2006). Water was divided into several groups which differed from time segments, boiling times and standing time after boiled. The water boiled by automatic water boiler and household water kettle was also detected. Results Content of residual chlorine in municipal water was 0.25 mg/L while the nitrite was not found. In the group of tap water which was boiling for 1 min, the concentration of residual chlorine was zero. The chlorine content in the water boiled by household electric kettle was 0.1 mg/L, and reached a high level of 3.8 μg/L after 1 h, which was still under the limitation. The content of residual nitrite reached a high level of 2.37 μg/L after standing of 24 h, and reached 2.76 μg/L after another one-minute boiling. After 8 times of repeated boiling of tap water, the content of nitrite reached 3.38 μg/L. In the automatic water heater group, the chlorine content in the forenoon was higher than that in the morning and evening, which could not be detected. The residual nitrite in the morning was significantly higher than that in the forenoon and evening. Conclusion The concentration of residual chlorine in municipal tap water decreases after heating, while the nitrite increases. The chlorine in household electric kettle group is higher than the other groups, so it is suggested boiling water for another one minute with the cover opened after boiled. When using public automatic water heater, it is suggested to avoid busy hours.
