紫色土小流域浅层井水中胶体颗粒的季节变化

胶体是多种污染物迁移进入地下水的主要载体.为探究地下水中胶体颗粒的长期动态变化及影响因素,对川中丘陵区紫色土小流域浅层井中胶体颗粒浓度及井水理化性质进行了1 a的原位观测.结果表明:浅层井水中胶体颗粒含量存在较强的季节变异(CV0.5),胶体颗粒质量浓度峰值可达到14.68 mg·L~(-1)(相应的数量浓度为1.34×109L~(-1)),出现在非雨季,由人为取水扰动所致.雨季中前期大雨产流的物理扰动能有效增加井水中胶体颗粒浓度,后期暴雨的促进作用不明显.井水化学性质(EC、Ca2+、Mg2+、DOC)是影响胶体颗粒浓度动态及存在形态最重要的因素.该地区作为饮用水源的浅层井在雨季中前期可能受到因增加的胶体颗粒输入而辅助迁移的农化物质(如农药、P等)对井水质量安全的威胁,建议加强该时段内降雨后井水中胶体及井水理化性质的监测.

Seasonal Variation of Colloid Particles in the Shallow Well Water of a Small Watershed of Purple Soil

Colloids are the major carriers of various contaminants during the downward transport into groundwater.To explore the long-term dynamics of colloid in the groundwater and its influencing factors,a one-year monitoring of colloid concentration and water physicochemical parameters was carried out in the shallow wells in a purple soil dominated watershed in the hilly region of central Sichuan.The results indicated that colloid concentrations within a year had a strong seasonal variation with the coefficient of variation being larger than 0.5.The maximum of colloid mass concentration could reach as high as 14.68 mg·L^-1(the corresponding number concentration being 1.34×10⁹ L^-1),which occurred in the non-rainy season and was caused by the physical perturbations from water taken.Physical perturbations of rainfall led to the distinct peaks of colloid concentrations in the well water at the early stages of rainy season while it did not occur at the end of the rainy season even upon heavy storm.Water chemistries (EC,Ca²⁺,Mg²⁺,DOC) showed the dominant role in determining colloid concentrations and status in the well.The facilitated transport of contaminants (i.e.pesticides and heavy metals) due to the increased colloids in the shallow well water at the early stages of rainy season would potentially pose a great threat to the drinking water safety in the study area.Therefore,it is strongly suggested to increase the monitoring frequencies in terms of colloid concentrations and well water physicochemical parameters following the large rainfall events during this period.