多沙河流水-沙-砷污染物相互作用规律研究

The arsenic pollution in river has become a global environmental problem. After arsenic pollutants are adsorbed by sediment, not only its physical and chemical properties will change, but also the flow structure will be impacted. Flow, sediment and arsenic pollutants interact. But the research on arsenic adsorption by sediment is little, and most of the research has been achieved under the static conditions. It is difficult to reveal the interaction mechanism of flow-sediment-arsenic pollutants in siltladen river. To solve these new problems, this subject will analysis of temporal and spatial distribution characteristics of arsenic pollutants through collecting water quality data and monitoring the sewage outfall sections of the Yellow River. Through laboratory experiments and theoretical analysis，the effects of arsenic adsorption by sediment composition and sediment concentration under dynamic conditions will be studied. And the adsorption model of arsenic in siltladen river will be put forward. At last, interaction mechanism of flow-sediment-arsenic pollutants in the sediment-laden river will be revealed. The research results will contribute to the management of the contaminated water discharge, assessment of water environmental quality, prediction and controlling of water pollution. And the results will also improve the sediment adsorption theory, and promote the development of sediment movement mechanics and environmental science.

河流砷污染已成为全球性的水环境问题。泥沙吸附砷后，不仅自身表面的理化性质会改变，对水流结构也会造成影响，水流、泥沙与砷污染物相互作用。然而，目前泥沙对砷的吸附规律研究成果较少，且吸附研究主要在静水条件下进行，难以揭示多沙河流中水-沙-砷污染物相互作用机理。本项目拟以黄河为对象，分析多沙河流砷污染物时空分布特征；通过室内试验与理论分析相结合的手段，研究水动力条件对泥沙吸附砷污染物的影响；开展不同泥沙组成、含沙量等因素对泥沙吸附砷污染物的作用规律研究；建立多沙河流砷污染物吸附模型，提出多沙河流泥沙与砷污染物相互作用机理。研究成果不仅对多沙河流排污管理、水环境质量评价以及水污染预测与控制等具有重要指导意义，还可完善泥沙吸附重金属理论，为水沙科学与环境科学的交叉发展起到积极的推动作用。

本项目对黄河中下游地区底泥、原水和侧渗水进行了调研及现场取样检测，较为系统地剖析了新水沙情势下黄河中下游砷污染物时空分布规律及环境健康风险；项目组利用环形水槽开展了动水条件下泥沙吸附砷污染物规律研究，模拟黄河自然流动状态，考察了含沙量、初始浓度和吸附时间等影响因素，进一步探讨了砷污染物吸附动力学规律；并对吸附砷之后的泥沙颗粒表面形貌进行了扫描、观察和表面元素分析。本项目结论可为多沙河流排污管理、水环境与健康评价等提供科学支撑。主要成果可概括为3个方面：（1）黄河中下游干流的原水和底泥中砷污染物含量较低，处于无污染状态；但个别支流的原水和黄河侧渗水中砷含量较高，接近标准限值，且有逐年上升的趋势，存在一定的环境与健康风险。（2）在动水条件下，黄河细沙对砷的吸附很快，水体中的砷含量随时间呈幂函数下降，含沙量越小、初始浓度越高，单位质量泥沙对砷的吸附量越大。当初始浓度为0.05mg/L时，吸附平衡时间为300s，去除率为83%；当初始浓度为0.5mg/L时，吸附平衡时间为60s，去除率为90%。动力学模型拟合结果表明，准二级动力学方程能较为准确地描述吸附过程，说明该过程中存在化学吸附。（3）SEM图像观察表明，水源成分越多样泥沙颗粒表面形态就越复杂，共存离子的存在使得吸附后的泥沙颗粒表面的孔隙因被填充而大大减少；N2吸附-脱附BET分析及泥沙颗粒表面元素分析结果表明，As、Fe3+之间由于产生竞争吸附而使As吸附量降低，Mn2+改变了泥沙的表面形貌而导致泥沙吸附能力减弱。