GIS-based Red-bed Groundwater In The Anhui Segment Of The Tan-lu Fault Zone Water Quality Assessment And Spatial Distribution Characteristics

The red-bed in the Anhui segment of the Tan-lu fault zone is widely distributed,and the red-bed groundwater resource is one of the important drinking water sources.However,there are few studies on the red-bed groundwater in the Anhui segment of the Tan-lu fault zone,especially on the spatial distribution characteristics of the water quality and water volume about the red-bed groundwater.To this end,this paper takes the red-bed groundwater in the Anhui segment of the Tan-lu fault zone as the research object.Based on the summary and analysis of the geological background and hydrogeological conditions,the statistical characteristics and spatial distribution of hydrogeochemistry components are studied by using a combination of field investigation and indoor analysis.At the same time,comprehensively evaluation and the spatial distribution of the red-beds groundwater quality are studied.The spatial distribution characteristics and the sources of pollutants are also focused about the poor water quality areas and the very poor water quality areas.The spatial distribution characteristics of red-bed groundwater volume are studied based on the water resource and water-rich are evaluated.The main results and conclusions of this study are as follows:?1?The red-bed distribution range of the Anhui segment of the Tan-lu fault zone is accurately divided,combined with the 1:200,000 regional geological map,the cross-section of the red-bed drilling and the 1:200,000 exposed red-bed distribution map.?2?According to the spatial zoning results of the hydrogeochemistry type,the southern region is dominated by HCO₃-Ca;the central region is HCO₃-K+Na·Ca,HCO₃·SO₄-K+Na·Ca and HCO₃-Ca·Mg;the eastern region is HCO₃-K+Na·Ca,HCO₃-K+Na·Ca·Mg and HCO₃-Ca.?3?According to the groundwater quality standard,the quality grade of most components in the red-bed groundwater in the study area is Class I.The components with exceeded the standard are nitrate,sulfate,fluoride,iron,manganese and aluminum.The proportion of nitrate,iron,manganese and aluminum in the class IV water reached9.46%,19.57%,15.89%and 15.96%.The proportion of sulfate,nitrate and fluoride in the V water reached 4.23%,17.57%and 7.33%.?4?The research shows that the improved Nemero index model is more in line with the actual situation of the study area than the traditional Nemero index model.Based on the evaluation results of the red-bed groundwater water quality type of the improved Nemero index model,the proportion of the excellent water quality and the good water quality in the study area accounted for 15.03%and 13.94%;the area of general water quality was 60.19%;the area of poor water quality and the very poor water quality was9.74%and 1.12%.?5?According to the spatial relationship between poor water quality areas and the urban,the poor water quality areas are concentrated in the area to be developed around the town and urban-rural integration.The main over-standard components are sodium potassium ion and sulfate,which is mainly caused by the original geological environment.According to the spatial relationship between very poor water quality areas and cultivated land,the very poor water quality areas are mostly located in the basic farmland protection area.The main over-standard components are nitrate and aluminum,which is mainly caused by the unintentional discharge of industrial sewage and enterprise sewage and the random landfill of urban domestic garbage.?6?The main source of recharge of the red-bed groundwater resources in the study area is rainfall recharge.The amount of recoverable resources is 2.726 billion cubic meters each year,accounting for 81.76%of natural recharge resources.According to the water-rich distribution characteristics of the red-bed groundwater,the water volume of the red-bed groundwater is generally better,and the proportion of the area above the medium water volume reached 54.52%.?7?Studies have shown that the Tan-lu fault zone has an important control effect on the distribution of red-beds,the spatial distribution characteristics of water quality and water-richness.