给水管网疏松沉积物的结构特征及其风险识别

自来水变色问题通常被视为感官问题，而导致自来水变色的管网疏松沉积物的结构特征及其潜在危害尚不明确。采集了我国北方某城市频繁发生自来水“黄水”的7个小区管网中的疏松沉积物，并进行了分析。结果表明：所有疏松沉积物样品中含量最高的金属元素都是铁元素、主要晶体成分是铁氧化物，样品颗粒微观形貌大多具有锋利的针刺状结构；样品zeta电位范围为−15~20 mV、平均粒径范围为500~4 000 nm、粗糙度范围为0.25~7.81 nm。体外细胞毒性实验结果显示，沉积物可产生一定的细胞毒性(样品浓度100 mg·L⁻¹时人体健康肝脏细胞存活率为86.61%~99.71%)。通过主成分分析发现，疏松沉积物毒性与粗糙度的相关性比与粒度的高，表明形貌对样品毒性的影响比粒径更大；γ-FeOOH是与疏松沉积物毒性相关性最显著的晶体组分，其对毒性的贡献可能是通过增加颗粒表面锋利程度造成的，余氯不足时可能会因铁释放加剧和γ-FeOOH含量增大造成更高的毒性风险。本研究结果可为全面认识给水管网疏松沉积物的风险提供参考。

Structure characteristics and health risk of loose deposits in drinking water distribution system

Discoloration of tap water caused by loose deposits is usually regarded as a sensory problem, but structural characteristics and health risk of the loose deposits are not clear. In this study, we collected loose deposits from the residential areas from the section where frequently occurs “yellow water” in a northern city in China. Characterization results showed that in loose deposit samples, the highest metal element was iron and the main crystal component was iron oxide. The morphology of the samples contained sharp fiber-like structures. The zeta potentials of the samples were −15~20 mV, the average sizes were 500~4 000 nm, and the roughness values were 0.25~7.81 nm. The samples had certain toxicity to health human liver cells (the cell viability was 86.61%~99.71% under loose deposits 100 mg·L−1). Principal component analysis showed that roughness had the highest correlation with toxicity, which indicated that morphology had greater influence on sample toxicity than size. Among crystal components, γ-FeOOH had the highest correlation with toxicity, and its contribution to toxicity may due to sharpness increase. When the residual chlorine is insufficient, it will lead to higher toxicity risk due to the increase of iron release and γ-FeOOH content. Therefore, iron particles have great effects on the toxicity of loose deposits. This study provides an important basis for the comprehensive understanding on the risk of loose deposits in drinking water distribution system.