菱镁矿开采引起的Dubravsk(y) Massif水文地质结构中的地下水化学成分变化

Dubravsky Massif菱镁矿体的开采产生了部分局限在石炭纪低裂缝渗透变质岩中的喀斯特型裂缝含水层.大量的开矿过程对含水层中的地下水循环和化学成分都造成了可观的变化.本文研究了在这种复杂条件下地下水化学成分变化成因模型.根据化学配位模型,计算出所选矿物的饱和指数,从而指示所有喀斯特裂缝含水层饱和带中的地下水对菱镁矿、白云石、方解石的过饱和度和石膏的不饱和度.假设地下水未受人类活动的污染,而白云石中黄铁矿的氧化对成矿影响甚微,则水化学数据的统计描述代表了含水层中的水文地球化学背景.矿山中矿石焙烧释放的富氮气体凝聚产生的醋酸,能促进菱镁矿和白云石的溶解.这样产生的地下水相对背景值来说则富集NO3,Mg,和TIC.因此,由于地下开矿,岩溶作用估计将是原来的1.5倍.尽管有污染,这些所测参数并没有超过斯洛伐克卫生保健部颁发的No.29/2002 Z.z.饮用水标准临界值.因此采矿后含水层的开采也是可行的.

Groundwater chemical composition changes in the Dubravsk(y) Massif hydrogeological structure,induced by magnesite exploitation

Exploited magnesite bodies of the Dubravsky Massif create parts of karst-fissure aquifer confined by Carboniferous metamorphic rocks of low fissure permeability. Extensive mining progress caused considerable changes in both groundwater circulation and groundwater chemical composition of the aquifer. A model of groundwater chemical composition genesis in such complicated conditions is presented in this paper. Saturation indices (SI) for chosen minerals were computed based on speciation modelling, which indicate oversaturation of groundwater with magnesite, dolomite, calcite, and undersaturation with gypsum in all saturated zone of karstfissure aquifer. Statistical interpretations of hydrochemical data suppose that anthropogenically unaffected groundwater, where mineralisation is slightly altered by pyrite oxidation in dolomitic environment, represents hydrogeochemical background within the aquifer. It is supposed, that azonic acid, generated by condensation of nitrogen-rich gases freeing by blast-firings in mine, accelerate magnesite and dolomite dissolution. Produced groundwater types are of higher content of NO3 , Mg and TIC in comparison with background values. Estimated acceleration of karstification processes due to underground mining is about 1.5 times. In spite of detected contamination, threshold values of drinking water standard, given by the Edict of the Slovak Ministry of Health Care No. 29 /2002 Z.z. are not markedly exceeded for tested parameters. Future possible exploitation of studied aquifer after mining termination is not excluded.