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大同盆地是典型的干旱-半干旱内陆盆地,盆地中部地下水碘含量异常,对当地饮用水安全造成了严重威胁.对盆地高碘地下水分布区沉积物组成及稀土元素(REE)进行了地球化学研究,结果表明,地下水系统呈弱碱性(pH值为7.18~9.64)的偏还原环境,沉积物多为Ce正常或轻微负异常及Eu负异常;沉积物中碘含量为0~1.78×10~(-6);ΣREE含量较高,ΣLREE/ΣHREE比值为2.79~4.14,即富集轻稀土元素(LREE)而亏损重稀土元素(HREE).ΣREE与碘含量呈负相关关系,虽然铁氧化物/氢氧化物矿物的还原性溶解可导致二者的释放,但由于沉积物有机质产生的低结晶矿物对碘的强吸附性,使沉积物中碘含量较高;弱碱性环境中REE的再吸附过程会导致沉积物中富集LREE;沉积物中碘含量与氧化还原敏感组分TOC、U、V及[Eu]N的关系也表明,地下水系统的氧化还原条件及有机质含量是影响碘富集的重要因素.
Datong Basin is a typical arid-semiarid inland basin with abnormal groundwater iodine content in the central part of the basin, which poses a serious threat to the safety of drinking water in the basin. The sediment composition and REE of the high iodine groundwater in the basin are geochemically The results show that the groundwater system is a weakly alkaline (pH value of 7.18 ~ 9.64) partial reduction of the environment, the sediment mostly normal or slight negative Ce and Eu anomalies; sediment iodine content of 0 ~ 1.78 × 10 ~ (-6), higher ΣREE content and ΣLREE / ΣHREE ratio ranging from 2.79 to 4.14, ie enrichment of LREE and loss of heavy rare earth elements (HREE). ΣREE has a negative correlation with iodine content, The reductive dissolution of matter / hydroxide minerals can lead to the release of both, but due to the strong adsorption of low-crystallinity minerals produced by sediment organic matter to iodine, the iodine content in sediments is higher; in weakly alkaline environment, REE The re-adsorption process leads to the enrichment of LREE in the sediments. The relationship between the iodine content in the sediments and the redox-sensitive components TOC, U, V and [Eu] N also shows that the redox conditions and organic matter content of the groundwater system are affected by iodine An important factor in enrichment.