Evaluation Of Eco-environmental Geological Quality In Danzhai County Based On Comprehensive Evaluation Method

Danzhai County,Guizhou Province,is composed of karst parts and non-karst parts in geology.In this paper,comprehensive method is used to establish evaluation system of eco-environmental geology.Based on this system,the of eco-environmental geological quality and eco-environment geological bearing capacity are evaluated.The natural geographical conditions,geological environment disasters,quality of land,and human activities for production and life in Danzhai County are studied comprehensively.With these researches,12evaluation indexes for the system are selected.These indexes are contained in climate,natural geography,hydrology,land use,fault structure,ecology,geologic disaster,and quality of land.These indexes are analyzed and discussed one by one depending on large amount of field surveys and physical experiments,and chemical analyzing of samples.The composition of rapid decomposed nitrogen,rapid phosphorus,and rapid potassium for the land is used to evaluate the soil nutrient.This evaluation system is applied to evaluate the eco-environmental geological quality and bearing capacity of eco-environment geology.The conclusions of evaluation are summarized as follows:1.The composition of heavy metal elements As,Cd,Cr,Cu,Hg,Ni,Pb,Zn in the soil is calculated individually to define the pollution indicator of land.In the whole,the land quality in Danzhai County is good in the East and bad in the West.The soil quality in non-karst area is higher than that in karst area.2.Based on the comprehensive analysis of physical and chemical properties of rocks,it is considered that areas occurred by siltstone and metamorphic siltstone are the best;by limestone,dolomite and slate are good generally;by shale and claystone are moderate.The species diversity of vegetation in the east is greater than that in the west in Danzhai County.It is also greater in non-karst area than in karst area.Because of the complicated structures occurred,the main potential geological disaster is landslide in Danzhai County.3.Due to the unrestrained exploration of natural resources,especially the mercury deposits,the land is seriously polluted by elements Hg and Cd.4.Based on these works,the weights of the indexes contained in evaluation system were defined as follow:annual rainfall 0.078;slope 0.282;aspect 0.161;species richness of plant0.032;vegetation coverage 0.032;physical and chemical properties of rock;0.063,geologic disaster 0.022;fault structure 0.038;land quality 0.170;land use 0.083;mining activities 0.013,and vegetation changes 0.026.With above indexes given weight,evaluation system of eco-environmental geological quality for Danzhai County is established finally.5.The studied area is divided into five grades:high quality,good quality,medium quality,poor quality and extremely poor quality.The existing problems of eco-environmental geology in each area are summarized.The protection measures for these problems are put forward.In Danzhai County,the eco-environmental geological quality in the Middle East and Midwest is better.But it in the north and South Central is worse.6.The evaluation result for bearing capacity of eco-environment geology in Danzhai County indicates that the total area,464.1630 km~2,does not exceed the threshold value of eco-environment geological bearing capacity.But the rest area,479.2238 km~2,has exceeded.A conceptual plan is proposed for the sustainable development for Danzhai County.Two key development areas,two optimized development areas and two restricted development areas are delineated.