Mine Environmental Monitoring and EvaluationUsing RS&GIS in Chongqing

Ting Zhang#1, Rui Liu#2, Zhirong Zheng*3, Yuelong Chi*4

#College of Geophysics, Chengdu University of TechnologyChengdu 610059, Sichuan Province, China

1hengtanglu@yahoo.com.cn 2lr@cdut.edu.cn 4cyl12@126.com*Department of Computer Science, Xinzhou Teachers University, Xinzhou, Shanx, China

3xzzzr@xztc.edu.cn

Abstract—Mineral resource is the important material base for the humanity livelihood and development. But, it is unavoidable that development of mineral resources could cause a certain extent of destruction on ecological environment In order to development mineral resources reasonably and prevent environmental problems effectively, carrying on the effective monitor to the environment’s present situation and the change is indispensable. The development of RS(Remote Sensing)and GIS(Geographic Information System)technology has offered very important means and method for monitoring the mine environment in science which have already been utilized extensively by the professional person and has made certain achievement. (e.g. [1])This article utilizes IKONOS image in June of 2010 to carry on the environmental monitoring which caused by mine exploitation in Xiushan key mining belts of Chongqing. Then utilize the RS & GIS technology to carry on the environmental quality valuation of this area.

Keywords—Remote Sensing(RS), Geographic InformationSystem(GIS), Environmental Monitoring

I. STUDY AREA PROFILE AND TECHNICAL ROUTE

The Study area is located in Midwest of Chongqing,including Beibei District, Jiangbei District, Shapingba, Dadukou, Jiulongpo District, Banan District, Yubei area, south area and the whole Chongqing urban. The range of geographical coordinates, E106 ° 14'-106 ° 54 ', N 29 ° 19'-29 ° 49 '(e.g. fig.1) .The study area is hilly area, low altitude and relatively flat terrain.

The main mineral of the study area is constructionallimestone, and there also have mudstone, coal, iron, kaolin and other kinds of mineral. The mining of constructionallimestone has a prominent position, and the utilization of constructional limestone has a significant meaning of promoting city’s economic and social development. But inevitably , it also brings relatively serious geological disasters at the same time.

II. DATA SELECTION AND PROCESSING

A. Data SelectionThe main data used in this article, including remote sensing

images and related non-remote sensing data. The remote sensing images are the multi-spectral bands and PAN band of IKONOS high spatial resolution remote sensing images

acquired on May 24, 2010. The images have good quality, no clouds and low noise.

IKONOS has 5 bands, the spatial resolution of PAN-band is 1m, the spatial resolution of other four spectral bands (blue, green, red, near infrared band) is 4m, and fully able to meetthe requirements of monitoring the environmental problems caused by the mining of mineral resources and the condition of the mineral resource development in the area. Non-sensing materials including 1:10 000 topographic map, Chongqing mining rights registration materials, and Chongqing mineral resource master plan materials from 2006 to 2010.

Fig.1 Study area in Google Earth

B. Data ProcessingFor the characteristics of IKONOS data, we carried out

orthorectification, data fusion, image mosaic and true color composite.

The topographic maps and DEM data of the study area are ready before carry out orthorectification. The orbital parameters of the original image data were imported into the ORTHORECTIFICATION module in software of ENVI 4.7. We enter a certain amount of ground control points (GCPs) , insure the GCPs are precise and evenly distributed in the images to be corrected, at the same time, input the corresponding ground elevation provided by topographic maps and DEM data. Then carry out the coordinate conversion and gray-resampling.

PAN band of IKONOS data has a high resolution of 1m.But the gray image is not conducive to the human eyes todistinguish, so we could keep the multi-spectral information

___________________________________ 978-1-4244-8351-8/11/$26.00 ©2011 IEEE

through data fusion, while improve the spatial resolution. The commonly used data fusion methods are Principal components transform, HIS transform, Gram-schmidt transform and Wavelet Transform. First cut a piece of experimental data for the four different fusion methods, comparing the results obtained from the four fusion methods, we come to a conclusion that the fusion result of Gram-schmidt transform has highest resolution and the least color distortion (e.g. [4]). As a result, we choose Gram-schmidt transform for data fusion.

The IKONOS data that covered the entire study area hasfive scenes, so we need to combine the five scenes into one by the mosaic approach based on geographical coordinates, using MOSAICKING module in ENVI 4.7. A cutline is drawn ineach image to cut off the mottle on the edge of image before mosaic, set a certain feather radius to form transition in the seams, balance the color of all five images by the calculation of statistics Overlap region, finally obtain a remote sensing image that have uniform color, natural transition, and noobvious traces of stitching.

In order to express the surface features better, this paper chose the red, green and blue bands to composite ture-colorimage, and then the color enhancement was carried out to thecomposite color image. Finally got a simulated true-color, 1:10000 digital orthophoto map (DOM) of the whole study area.

III. REMOTE SENSING INFORMATION EXTRACTION

A. Establishment of Interpretation SignsThe study area has varied surface features. From the

collected materials, field reconnaissance and the DOM of IKONOS image, comprehensive analysis the image interpretation factor (such as shape, size, shadow, color, texture, pattern, location, layout), establish interpretation signs of the mine environment, then analysis image characteristics relative the mineral exploitation informationand mining environment information.

A . Constructional Limestone Mining Point

B .Coal Mining Point

C .Water Pollution Point

D .Landslide

Fig. 2 Features of IKONOS image related to mining environment information

TABLE IINTERPRETATION SIGNS OF FEATURE TYPE

Feature Type Direct Interpretation Signs

Indirect InterpretationSigns

Constructional Limestone

Mining Point

Gray, differ size, irregular shape.

Active mining surface, crusher, Yard, loading platform, simple road, water pit, building, etc.

are clearly visible.

Coal Mining Point

Black, differ size, irregular shape.

Coal heaps around here,mining equipment and

buildings can be clearly seen.

Water Pollution Point

The color of pollutants usually is green or white, extends along the surface

of the water.

Obviously contrast with the water color

LandslideTonal is yellow,the shape is round-backed armchair

shape or arc shape.

Landslide wall, landslide accumulation, threatening

objects, destruction of vegetation and soil, etc.

B. Method of Information ExtractionAll information extraction work was carried out on the

ArcGIS 9.3 platform, at the basis of establishing interpretation signs, completed with human-computer interaction methods. Before human-computer interaction interpreting, make full use the spectral differences of mine surface features, at the same time, use supervised classification or unsupervised classification methods to finish preliminary classificationwork. The processed image will be converted into GeoTiff image format before information extraction, take it as a background layer combine with mining rights registration data and topographic map to superposition analysis. We could not only do macroscopic monitoring and extracting the distribution of mining , the status of mining, the situation of environmental damage caused by mining activities, but also accurate delineation of distribution and roughly sizes of undocumented illegal mine and cross-border exploitation of mines.

C. Field verificationField verification work was carried out after the indoor

work of information extraction. The main purpose is: 1,Verify the accuracy of thematic information interpretation signs, whether them covers all extraction types, whether have representative; 2, Verify the reliability of information extraction. Field verification work includes: check the information in question, added the missing information, and modify false information. The verification work conduct with such survey and observation approaches: GPS location, area measurement, on-site photographs, description of the environment, and qualitative polygons.

IV. MINE ENVIRONMENTAL MONITORING AND EVALUATION

A. Overview of mine environmental remote sensingmonitoring information

1) The situation of land occupation for mining: Through the mine environmental remote sensing survey about 2800km2 of area. Mine exploitation occupy land 238 places, total acreage is 621.94 ha, 2.2% of the research area. Types of mine exploitation occupying land are mining field, mine construction, mining activities (transit site), and solid waste (waste heap, coal waste heap).

TABLE II2010 CHONGQING MINE OCCUPYING LAND TABLES (UNIT: HA)

Minerals mining field

mine construction

transit site

solid waste

building stone Limestone 186.13 4.49 0.62 4.52

Cement limestone 97.79 0.22 1.3

Limestone 20.7Building sand 128.59 0.08 8.53

coal 0.08 5.05 3.77Brick shale 104.97 42.64 12.08 0.38

2) Mine geological hazards monitoring: When create economic benefit; the mining activities may also cause geological disasters at the same time. Through remote sensing interpretation and field verification on the study area, we found that the vast majority of the study area did not stop mining exploration and formation "doline"(Fig.3) , those have not been filled or took other recovery work, some stopped mining surface exist hazards such as mudslides, landslides, avalanches and other geological disasters.

Fig.3 Mining limestone to form "artificial doline"

Here is a constructional limestone mining point, located at Dadukou District of Chongqing, the centre coordinate is 106° 23�������������� ����������������������������������������the formed “doline” has not been clear or been filled.

Fig. 4 An area of debris flow in Chongqing Yubei

The debris flow located at Yubei District of Chongqing, the centre coordinate is 106° 49�� ���� �� �� � ���� Through the remote sensing interpretation and field survey found that, the rock of debris flow source area is mostly clastic rock, joints is development., after washed by rain , it formed a ribbon debris flow along the ravine. It blocked one road;destroyed about 50 acres of farmland.

3) Remote sensing monitoring of mine air pollution: Theremote sensing image and field verification survey results show that, most of the building limestone mining was met the norms. But some Limestone mining field have serious dust pollution.(Fig.5)

Here is a constructional limestone mining point, located at Dadukou District of Chongqing, the centre coordinate is 106° 23��57 ������5 �27���� On the site the dust floated all over in the sky, and pollute the surrounding environment.

Fig.5 Dust pollution caused by limestone mining

B. Mine Environmental Quality EvaluationIn this paper, with the mine environment assessment unit of

1km ×1km grid, selected these evaluation factors such as vegetation coverage rate, landform, mining occupied land rate, mining point density, degree of environmental recovery, etc. (e.g. [7]). According to mine environmental assessment index grade standard of SICHUAN province (Table ) for each evaluation factor were grading. (Fig.6)

Fig.6 Grade maps of some environmental evaluation parameter

TABLE III MINE ENVIRONMENTAL ASSESSMENT INDEX GRADESTANDARD

Evaluation factor

Evaluation index Grade standard

1 2 3

Geological structure

Complicated structure, fracture is

development strongly.

Structure is somewhat

complicated, fracture is

development.

Simple structure,fracture is

not developme

nt.

Lithological combination

Rock is broken, slope is instability.

Rock is somewhat

broken, local slope is

instability.

Rock is stability

Landform Slope>35° Slope is in 20°-35°. Slope<20°

Vegetation Coverage Rate (%)

<30% 30% 60% >60%

Regional important

degreeImportant Average Non-

important

Mining Point Density >5 1 5 0

Mining occupied

land rate (%)>30 30 10 <10

Geological Hazards

Point Density

Smallgeological hazards is

more than 5 points, or

large geological hazards is

more than one point.

Small geological hazards is

more than one point.

None geological

hazard.

Atmospheric pollution degree

Serious A little serious Slight

Water pollution degree

Serious A little serious Slight

The difficulty Level of

environmental recovery

Difficult A little difficult Easy

Environmental recovery

degreeNo recovery Some recovery Complete

recovery

Table IV WEIGHT OF EVALUATION FACTORS

Evaluation factor weightGeological structure 0.04Lithological combination 0.04Landform 0.04Vegetation Coverage Rate(%) 0.04Regional important degree 0.04Mining Point Density 0.12Mining occupied land rate (%) 0.12Geological Hazards Point Density 0.12Atmospheric pollution degree 0.12Water pollution degree 0.12The difficulty Level of environmental recovery 0.05Environmental recovery degree 0.15

Then according to the weight of each factor (Table IV), all evaluation factors were weighted analysis. At last, the result of weighted analysis were divided into five grades, finally get the comprehensive environmental evaluation results (Fig.7).

Fig.7 Grade map of environmental evaluation

In order to better express the quality of spatial distribution of the mine geological environment, each grid of the mine geological environment quality index as the sample points, spatial interpolation on the mine geological environment and Mine environmental quality, get the final mine geological environment evaluation results.(Fig.8)

Fig.8 Environmental evaluation Map of study area

V. CONCLUSION

Through IKONOS images, using remote sensing and GIS technology in this paper, the situation in Chongqing mining and mining-induced environmental problems were monitoredand the quality of mine environment were evaluated. It can be seen through the research and application that, fused IKONOS images can be well used in monitoring the environmental of study area, environmental monitoring results are accurate and the environmental evaluation factor can been extractedeffectively, combined with the mathematical methods can doan ideal environmental quality assessment of study area.

In this study, also found some noticeable problems and shared experiences as follows:

Mining condition usually has certain imaging characteristic, can be direct recognized in high-resolution images. Whether the closed mine can recognize from image depends on how long it has been shut down. Such as mining surface is weathering, or weeds is overgrown on the ground. Sometimesthe closed mining is hard to judge, especially some unauthorized small mining, these have none obvious imagesigns, and need field validation.

Because the spectral resolution of IKONOS image is low, it can’t reflect the atmospheric pollution situation very well, wemainly rely on field verification to finish the monitoring of atmospheric pollution.

In IKONOS images, the brightness values of limestone mining surface obviously higher than other features, so in image enhancement process, common 2% linear stretch couldlead to the color of limestone mining surface become too bright, caused information loss. The optimal linear stretch is more suitable for the information extraction of theconstructional limestone mining situation.

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