银川平原沉积物中砷的吸附机制及对地下水中砷富集影响研究

High arsenic groundwater distributed in Yinchuan Plain where arsenicosis patients have been found in large number. Groundwater is a strategic resource, with deep groundwater increasingly used for drinking water supply to reduce arsenic exposure of rural villagers who have relied on shallow tube wells for drinking. But, the deep groundwater quality would be recharged and polluted by shallow high arsenic.groundwater leakage recharge and the adsorption of arsenic released from sediment for deep groundwater environment change. Based on the sediment extraction and arsenic adsorption experiments, the project carry out adsorption mechanism of sediment arsenic. Moreover, using a variety of technical methods such as sedimentary environment analysis, the main chemical composition analysis, iron/arsenic extraction experiments using different extract liquid, batch and column arsenic adsorption experiments in different arsenic concentration and water environment conditions, relationship between groundwater arsenic and sediment adsorption arsenic has been analysed. The arsenic distribution mechanism in the groundwater-sediment system could be studied under the current conditions, and adsorption ability of sediment could be quantitative revealed when the arsenic migrate to deep aquifer. Also the contamination risk of fresh deep groundwater in the shallow high arsenic groundwater regions has been discussed. The results not only can enrich and improve the academic level of high arsenic groundwater, also provide scientific theoretical basis for deep drinking groundwater utilization and prevention and improvement of arsenic exposed in Yinchuan Plain.

银川平原是我国饮水型砷中毒区域之一，开采深层优质地下水是城镇集中供水和解决农村饮用浅层高砷水的方式。但浅层高砷地下水将可能越流补给或深层地下水因水环境改变而导致沉积物中砷的吸附-解吸附。项目基于沉积物提取试验和砷吸附试验开展含水层对砷吸附机制研究。在湖积和冲湖平原区,分别开展不同深度沉积环境分析和主要化学组分测试,利用不同提取液进行铁/砷提取试验，开展砷批吸附试验、柱吸附试验和原位抽水试验，结合地下水水化学特征，分析地下水中的砷与沉积物吸附砷相关关系，研究砷在地下水-沉积物系统的分配机制，定量揭示不同沉积环境沉积物对砷的吸附能力，探讨浅层高砷地下水区深层优质地下水砷污染分险。其成果不仅可丰富和提高高砷地下水的研究水平，也为深层优质地下水开发利用和防病改水提供科学理论依据。

银川平原是我国高砷地下水分布区之一，地下水中砷含量受沉积物吸附机制影响。开展了沉积物中砷提取试验，分析了沉积物总砷、不同形态吸附砷和地下水中砷含量的关系，探讨了不同沉积环境对地下水中砷含量的影响作用；开展了原位抽水试验和厌氧吸附试验，探讨了浅层高砷地下水迁移风险和沉积物对砷的吸附作用。研究表明，银川平原高砷地下水主要分布在浅层含水层中，沉积物中总砷、可提取砷含量受沉积环境和粒径影响，高砷区沉积物主要为暗色的粉细砂，还原环境更有利于吸附砷的释放，沉积物中可交换态的砷是地下水中砷的直接来源，对砷吸附作用可降低浅层高砷地下水向下层的迁移风险。本研究不仅提高了工作区高砷地下水研究水平，也为高砷区防病改水、深层优质地下水开发利用国土空间规范等提供基础资料。