CN114184665B - A method for monitoring radioactive water environment in coal-uranium resource overlapping areas - Google Patents

Abstract

The invention particularly relates to a method for monitoring radioactive water environment in a uranium-coal resource overlapping area, which comprises the following steps: knowing the distribution rule of uranium ore aquifers and coal beds in a coal-uranium resource superposition area, and grasping the water chemical characteristics and the water environment background level of different aquifers in the coal-uranium resource superposition area; laying a groundwater monitoring system capable of timely reflecting water environment changes of all aquifers and surface water bodies in a uranium coal resource overlapping area; selecting a long-term monitoring frequency of underground water, and increasing the monitoring frequency when the large-scale drainage of the coal mine is performed or the mining scale is enlarged on the basis of the long-term monitoring frequency; and through ground water level monitoring, the changes of ground water flow fields of different aquifers in the coal uranium resource overlapping area are mastered in time, and the influence of coal mine drainage water on each aquifer is judged in time. The method for monitoring the radioactive water environment of the uranium resource overlapping region can discover the change of the radioactive water chemical condition of the uranium ore aquifer in the uranium resource overlapping region in time and provide early warning in the early stage of pollution possibly occurring.

Description

A method for monitoring radioactive water environment in coal-uranium resource overlapping areas

Technical Field

The invention relates to the technical field of water environment investigation, and in particular to a method for monitoring radioactive water environment in a coal-uranium resource superposition area.

Background Art

Due to the similarity of the mineralization environment between sandstone uranium deposits and coal mines, the uranium deposits and coal seams produced in the northern basins of my country overlap with each other in space, forming a spatial geological pattern of "uranium above and coal below" in some areas. During coal mining, the release of water and pressure reduction of the overlying aquifer will change the groundwater flow field and form a regional groundwater level drop funnel. The formation of a regional drop funnel will change the groundwater flow field and uranium migration conditions in the sandstone uranium deposit layer, which may cause groundwater with high uranium concentration within the uranium deposit to enter the surface water environment along with the drainage of the coal mine, causing radioactive contamination.

The current groundwater environment monitoring methods are mostly centered around the monitoring of conventional groundwater indicators. The monitoring of radioactive water environments relies on laboratory measurements of radioactive indicators. These methods cannot quickly and effectively determine the impact of mineral development on the water environment, nor can they systematically analyze the impact pathways of pollution.

Summary of the invention

Based on this, it is necessary to provide a method for monitoring the radioactive water environment in coal-uranium resource overlapping areas in order to address the problem that the existing radioactive water environment monitoring methods in coal-uranium resource overlapping areas cannot quickly and effectively determine the impact of mineral development on the water environment. The method systematically establishes a water environment monitoring system for coal-uranium resource overlapping areas, utilizes water level observation, on-site monitoring combined with sampling and analysis, and timely discovers changes in radioactive water chemical conditions in uranium aquifers in coal-uranium resource overlapping areas from the perspective of groundwater flow field and redox conditions in the aquifer, and issues early warnings when pollution may occur. The method is suitable for water environment investigation and evaluation in resource overlapping areas with a "uranium above and coal below" stratigraphic structure.

In order to achieve the above object, the present invention provides the following technical solutions:

A method for monitoring radioactive water environment in a coal-uranium resource overlapping area comprises the following steps:

Step 01: Collect hydrogeological data of the coal-uranium resource superposition area, understand the distribution patterns of uranium aquifers and coal seams in the coal-uranium resource superposition area, and master the hydrochemical characteristics and water environment background level of different aquifers in the coal-uranium resource superposition area;

Step 02: Based on the hydrogeological conditions of the coal-uranium resource superposition area and the coal and uranium mining plan, a groundwater monitoring system is deployed that can timely reflect the changes in the water environment of each aquifer and surface water body in the coal-uranium resource superposition area;

Step 03: According to the groundwater recharge and drainage conditions and dynamic change characteristics of each aquifer in the coal-uranium resource superposition area, select the long-term groundwater monitoring frequency. On the basis of the long-term monitoring frequency, according to the coal and uranium mining plans, increase the monitoring frequency when the coal mine is drained on a large scale or the mining scale is expanded;

Step 04: Through groundwater level monitoring, timely grasp the changes in groundwater flow fields in different aquifers in the coal-uranium resource superposition area, and timely determine the impact of coal mine drainage on each aquifer.

Furthermore, the groundwater monitoring system includes: groundwater level observation points in different aquifers, groundwater and surface water on-site indicator monitoring points, and groundwater and surface water detection sample collection points.

Furthermore, the groundwater level observation points of the aquifer are used to monitor the changes in the groundwater flow field of the target layer for coal mine water release and pressure reduction, that is, the uranium mine aquifer. The groundwater level observation points of the aquifer are arranged in the direction vertical to the groundwater runoff or from the periphery to the center of the groundwater drop funnel.

Furthermore, the groundwater and surface water on-site monitoring points are used to timely detect changes in aquifer water environment indicators, thereby issuing early warnings for water environment changes; the groundwater on-site indicator monitoring points are mainly arranged on the groundwater runoff path from the uranium deposit range to the coal mining area, and the surface water on-site indicator monitoring points are mainly arranged at the coal mine drainage outlet and the surface water bodies downstream of the drainage outlet.

Furthermore, the groundwater and surface water sample collection points are used to grasp the content of chemical components in water bodies and analyze the trends and causes of water environment changes; the groundwater and surface water sample collection points should be able to reflect changes in water quality in each aquifer, and the sampling locations include uranium aquifers, potentially affected water supply aquifers, coal mine drainage and surface water.

Furthermore, in order to accurately reflect the changes in groundwater environmental radioactive indicators, the groundwater and surface water on-site indicator monitoring indicators include dissolved oxygen, redox potential, pH value and radon concentration in water; the groundwater and surface water detection sample collection and analysis items include general water sample simple analysis or full analysis, and uranium content in water.

Furthermore, in the process of on-site monitoring of groundwater and surface water indicators, if the dissolved oxygen or redox potential of the uranium aquifer is found to be elevated, it may cause an increase in the uranium concentration in the uranium aquifer water and the coal mine drainage water. In this case, an early warning should be issued and the on-site monitoring and sampling frequency of the uranium aquifer should be increased. If it is found that the dissolved oxygen or redox potential of the uranium aquifer is elevated while the radon concentration in the uranium aquifer and the coal mine drainage water is also elevated, it reflects that the uranium concentration in the uranium aquifer is elevated and has a tendency to migrate to the groundwater drop funnel.

The radioactive water environment monitoring method of the coal-uranium resource superposition area of the present invention is applicable to the coal-uranium resource superposition area of "uranium above and coal below".

Beneficial technical effects of the present invention:

The radioactive water environment monitoring method for coal-uranium resource overlapping areas provided by the present invention targets the special hydrogeological structure of the "upper uranium and lower coal" resource overlapping areas, utilizes the influence of redox conditions on the activation and migration of uranium in water, arranges monitoring points in a targeted manner, and systematically carries out water level monitoring, on-site indicator monitoring and sampling testing. It can timely discover changes in the redox conditions of the coal mine drainage layer and the increase in uranium concentration in the aquifer at the early stage of radioactive contamination, and issue early warnings for changes in the water environment in coal-uranium resource overlapping areas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of a method for monitoring radioactive water environment in a coal-uranium resource overlapping area provided by the present invention.

DETAILED DESCRIPTION

Sandstone-type uranium deposits are produced in groundwater environments with partial reduction conditions, while partial oxidation groundwater environments are conducive to the activation and migration of uranium in water. Therefore, by using this hydrogeochemical characteristic of uranium and designing corresponding monitoring methods, the activation and migration of uranium in groundwater, that is, the situation of radioactive transfer, can be determined through the changes in the redox conditions of the aquifer. At the same time, considering the characteristics of radon in the uranium decay chain can further determine the activation and migration of uranium in the aquifer.

Referring to FIG1 , in order to systematically and effectively implement water environment monitoring in coal-uranium resource overlapping areas, the present invention provides a method for monitoring radioactive water environment in coal-uranium resource overlapping areas, comprising the following steps:

Step 01. Preliminary data collection and analysis: Collect hydrogeological data of the coal-uranium resource superposition area, understand the distribution patterns of uranium aquifers and coal seams in the coal-uranium resource superposition area, and master the hydrochemical characteristics and water environment background levels of different aquifers in the coal-uranium resource superposition area.

Step 02, establish a water environment monitoring system: according to the hydrogeological conditions of the coal-uranium resource overlapping area and the coal mine uranium mining plan, set up a groundwater monitoring system that can timely reflect the changes in the water environment of each aquifer and surface water body in the coal-uranium resource overlapping area.

Step 03, determine the monitoring indicators: According to the groundwater recharge and drainage conditions and dynamic change characteristics of each aquifer in the coal-uranium resource superposition area, select the long-term groundwater monitoring frequency. On the basis of the long-term monitoring frequency, according to the coal mine uranium mining plan, increase the monitoring frequency when the coal mine is drained on a large scale or the mining scale is expanded.

Step 04, Monitoring and Evaluation: Through groundwater level monitoring, timely grasp the changes in groundwater flow fields in different aquifers in the coal-uranium resource superposition area, and timely determine the impact of coal mine drainage on each aquifer.

The groundwater monitoring system includes: groundwater level observation points in different aquifers, groundwater and surface water on-site indicator monitoring points, and groundwater and surface water detection sample collection points.

The groundwater level observation points of the aquifer are used to monitor the changes in the groundwater flow field of the target layer for coal mine water release and pressure reduction, that is, the uranium mine aquifer. The groundwater level observation points of the aquifer are arranged in the direction vertical to the groundwater runoff or from the periphery to the center of the groundwater drop funnel.

The groundwater and surface water on-site monitoring points are used to timely detect changes in aquifer water environment indicators, thereby issuing early warnings for water environment changes; the groundwater on-site indicator monitoring points are mainly arranged on the groundwater runoff path from the uranium deposit range to the coal mining area, and the surface water on-site indicator monitoring points are mainly arranged at the coal mine drainage outlet and the surface water bodies downstream of the drainage outlet.

The groundwater and surface water sample collection points are used to grasp the content of chemical components in water bodies and analyze the trends and causes of water environment changes; the groundwater and surface water sample collection points should be able to reflect changes in water quality in each aquifer, and the sampling locations include uranium aquifers, potentially affected water supply aquifers, coal mine drainage and surface water.

In order to accurately reflect the changes in groundwater environmental radioactive indicators, the groundwater and surface water on-site monitoring indicators include dissolved oxygen, redox potential, pH value and radon concentration in water; the groundwater and surface water detection sample collection and analysis items include general water sample simple analysis or full analysis, and uranium content in water.

During the on-site monitoring of groundwater and surface water indicators, if the dissolved oxygen or redox potential of the uranium aquifer is found to be elevated, it may cause an increase in the uranium concentration in the uranium aquifer water and the coal mine drainage water. In this case, an early warning should be issued and the on-site monitoring and sampling frequency of the uranium aquifer should be increased. If it is found that the dissolved oxygen or redox potential of the uranium aquifer is elevated while the radon concentration in the uranium aquifer and the coal mine drainage water is also elevated, it reflects that the uranium concentration in the uranium aquifer is elevated and has a tendency to migrate to the groundwater drop funnel.

The radioactive water environment monitoring method of the coal-uranium resource superposition area of the present invention is applicable to the coal-uranium resource superposition area of "uranium above and coal below".

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

Taking the Zaohuohao area in the northeast of the Ordos Basin in northern China as an example, the uranium deposits distributed in this area overlap with the mining area of the Wangjiata coal mine in the west of the deposit, with an overlapping area of about ^20km2 , accounting for more than 80% of the uranium deposit area. To the west of the coal-uranium resource overlapping area is the water source for Dongsheng District, Ordos City, and the drainage outlet of the coal mine is located in the water source basin. Since the aquifer where the uranium mine is located covers the coal seam, it has become the target layer for water release and pressure reduction in the coal mine. With the expansion of the coal mining area, when the influence of drainage is expanded to the uranium ore body, it is very likely to cause the activation and migration of uranium in the aquifer, and discharge it to the surface with drainage, causing radioactive pollution.

In view of the above situation, the radioactive water environment monitoring method of the coal-uranium resource overlapping area of the present invention is used to monitor the radioactivity of the water environment in the coal-uranium resource overlapping area, comprising the following steps:

1. Collect the hydrogeological and water environment data of the coal-uranium resource superposition area. According to the collected hydrogeological and water environment data of the coal-uranium resource superposition area, the main aquifers in the coal-uranium resource superposition area are: Quaternary phreatic aquifer, Cretaceous clastic rock phreatic-confined water aquifer, and Middle Jurassic Zhiluo Formation aquifer. Among them, the Quaternary phreatic aquifer is the water source water supply layer, and the Middle Jurassic Zhiluo Formation aquifer is the uranium reservoir and also the coal mine water release and pressure reduction layer. The coal mining area is located to the west of the uranium deposit and has not yet entered the uranium deposit area.

2. According to the distribution of aquifers in the monitoring area and the conditions of coal mine drainage, it can be analyzed that the main way of radioactive contamination in the monitoring area is that the coal mine drainage discharges the groundwater of the uranium aquifer to the surface, thereby causing radioactive contamination. Therefore, monitoring points are set up with a focus on the uranium aquifer, coal mine drainage outlets and drainage outlet areas. For the Zhiluo Formation uranium aquifer, 8 Zhiluo Formation aquifer monitoring holes are set up from east to west along the groundwater runoff direction within the uranium deposit; at the coal mine drainage outlet, 3 surface water monitoring points and 2 Quaternary aquifer monitoring points are set up from the drainage outlet to the downstream water source; at the same time, two Cretaceous aquifer monitoring points are set up within the uranium deposit.

3. Water environment monitoring work began in August 2016. At the beginning of the monitoring, the boundary of the groundwater level drop funnel formed by coal mining was located in the northwest of the uranium deposit, slightly entering the boundary of the uranium deposit. The Eh and dissolved oxygen of the uranium aquifer showed a reducing environment. Under this condition, the U element in the ore layer was difficult to dissolve and migrate. The uranium content in the water was 2.6μg~64μg, and the radon concentration in the water was less than 40Bq/L. The radioactive indicators were basically consistent with diving.

The uranium content in the coal mine drainage water is 0.37μg/L, and the discharged groundwater is highly mineralized Cl·HCO3-Na type water. The Quaternary groundwater downstream of the drainage outlet shows increased mineralization and Cl- content.

4. By the beginning of 2017, the coal mine expanded mining in the southern part of the uranium deposit, and the monitoring team increased the frequency of groundwater level and on-site indicator monitoring. Through water environment monitoring, it was found that from March 2017, when the coal mine expanded mining, to October 2017, the impact range of the drop funnel formed by drainage expanded to the middle of the uranium deposit, and the center of the funnel has moved to the west of the uranium deposit.

As the groundwater level of the uranium aquifer drops, the Eh of the aquifer in the middle and eastern parts of the deposit reaches 86mV~332mV, showing an oxidizing environment, and the radon concentration in the water reaches 26.61Bq/L~989.38Bq/L. Judging from the on-site monitoring indicators, the decline in the groundwater level of the aquifer has led to the activation and migration of uranium in the ore body and its dissolution in the groundwater. The sampling and analysis data also illustrate this argument. The uranium concentration in the water in the eastern part of the deposit has reached 1061μg/L.

The uranium content of groundwater discharged from the coal mine drainage outlet is 0.28μg/L, and the radon concentration in the water is 13Bq/L, which has not changed much. This is because the oxidation zone of the aquifer has moved from east to west and has not yet reached the west of the deposit. As drainage continues, the oxidation zone will move to the water release and pressure reduction area in the west of the deposit, and radioactive water with high uranium concentration will be discharged to the surface along with the drainage of the coal mine.

The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims (1)

1. The method for monitoring the radioactive water environment in the uranium resource overlapping area is characterized by comprising the following steps of:

Step 01, collecting hydrogeological data of a uranium resource overlapping region, knowing the distribution rule of uranium ore aquifers and coal beds of the uranium resource overlapping region, and grasping the water chemical characteristics and the water environment background level of different aquifers in the uranium resource overlapping region;

Step 02, laying a groundwater monitoring system capable of timely reflecting water environment changes of each aquifer and surface water body in the uranium-coal resource overlapping area according to hydrogeological conditions of the uranium-coal resource overlapping area and mining planning of uranium ores of the coal mine;

step 03, selecting a long-term monitoring frequency of underground water according to the condition of the water-bearing stratum underground water supply and drainage and the dynamic change characteristics in the coal uranium resource overlapping region, and increasing the monitoring frequency when the coal mine is used for large-scale drainage or the mining scale is enlarged according to the mining planning of the coal mine and uranium mine on the basis of the long-term monitoring frequency;

Step 04, timely grasping the underground water flow field changes of different aquifers in the coal uranium resource overlapping area through underground water level monitoring, and timely judging the influence of coal mine drainage water on each aquifer;

the uranium-coal resource overlapping area is an upper uranium-lower coal resource overlapping area;

the groundwater monitoring system includes: groundwater level observation points, groundwater and surface water field index monitoring points and groundwater and surface water detection sample collection points of different aquifers;

The underground water level observation points of the aquifer are used for monitoring the underground water flow field change condition of the coal mine water-discharging depressurization target layer, namely the uranium aquifer, and are arranged in the direction perpendicular to the underground water runoff or from the periphery to the center of an underground water falling funnel;

The underground water and surface water on-site pointing monitoring points are used for finding out the water environment index change of the aquifer in time, so that early warning is carried out on the water environment change; the underground water field index monitoring points are mainly arranged on an underground water runoff path from a uranium deposit range to a coal mine mining area, and the surface water field index monitoring points are mainly arranged on a coal mine water outlet and a surface water body at the downstream of the water outlet;

The underground water and surface water detection sample collection points are used for grasping the content of chemical components of the water body and analyzing the change trend and the cause of the water environment; the underground water and surface water detection sample collection points can reflect the water quality change of each aquifer, and the sampling positions comprise uranium ore aquifers, water supply aquifers which are possibly affected, coal mine drainage and surface water;

The on-site index monitoring indexes of the underground water and the surface water comprise dissolved oxygen, oxidation-reduction potential, pH value and radon concentration in water; the underground water and surface water detection sample collection analysis items comprise general water sample simple analysis or total analysis and uranium content in water;

In the process of monitoring the indexes of the ground water and the surface water, under the condition that the dissolved oxygen or the oxidation-reduction potential of the uranium deposit aquifer is found to be increased, early warning is provided and the frequency of on-site monitoring and sampling of the uranium deposit aquifer is increased; if the uranium aquifer dissolved oxygen or oxidation-reduction potential is found to be increased, and meanwhile, the radon concentration in the uranium aquifer and the water drained from the coal mine is also increased, the tendency that the uranium concentration in the uranium aquifer is increased and the uranium aquifer is migrated to the underground water dropping funnel is reflected.