Study On Evolution And Assessment Of Groundwater Quality In Ruoqiang And Qiemo Oasis Region Of Xinjiang

The studyarea is located in Ruoqiang-Qiemo oasis region, of which the area is 0.98×104 km2. Agricultural activity is the dominance human activity in Ruoqiang-Qiemo region. As human activities increase constantly, groundwater resources may significantly compensate insufficiency and uneven distribution in temporal and spatial of surface water. To study the quality, current pollution situation and vulnerability of groundwater in studyarea is of great significance for groundwater exploitation and protection.This article evaluated quality, current pollution situation and vulnerability of groundwater and analyzed hydrochemical field and characteristics of groundwater based on hydrochemical test results of 18 groundwater sampling points?including nine unconfined water sampling points and nine confined water sampling points? in studyarea. The data comes from “Groundwater pollution survey and evaluate of Bayingolin Mongol Autonomous Prefecture, Xinjiang?Ruoqiang-Qiemo region part?” which is a sub-project of China Geological Survey Bureau project "Groundwater pollution survey and evaluate of main cities in north western China"?1212011220982? in 2014 and groundwater quality monitoring data in 1986-1999, 2003 and 2011. Main conclusions listed as below:?1?Main hydrochemical types of unconfined water are SO₄·Cl-Na·Ca and Cl·HCO3·SO₄-Na·Mg. Superior cationic of unconfined water is Na+, while superior anion is SO₄2-. Main hydrochemical type of confined water is Cl·SO₄-Na·Mg. Superior cationic of confined water is Na+, while superior anion is Cl-.?2? Groundwater quality was evaluated by gray clustering method. There were no Grade ? sampling points of unconfined water, two Grade ?samples?accounting for 22.2% of unconfined water sampling points?, one Grade ? sample?accounting for 11.1% of unconfined water sampling points?, one Grade ?sample?accounting for 11.1% of unconfined water sampling points?, five Grade? sampling points?accounting for 55.6% of unconfined water sampling points?. All confined water sampling points were Grade V.?3?Current situation of groundwater pollution in study area was revealed. All nine unconfined water sampling points were unpolluted which accounting for 100%. For confined water, two sampling points were unpolluted?accounting for 22.2% of total?. Four sampling points were slightly polluted?accounting for 44.5% of total?. Three sampling points were moderately polluted?accounting for 33.3% total?. There are 39 organic pollution testing parameters of groundwater in the studyarea. Two parameters which are Trichloromethane and 1, 2-dichlorobenzene were detected. Trichloromethane was detected in five sampling points with detection rate of 27.8%. 1, 2-dichlorobenzene was detected in two sampling points with detection rate of 11.1%. Concentration of both Trichloromethane and 1,2-dichlorobenzene are below the limit value of the drinking water standard.?4?According to the statistical analysis of groundwater quality monitoring data near the counties in research area, we found that the background value of groundwater F- concentration in Qiemo is higher than that in Ruoqiang. With the increase of area of cultivated land and amount of nitrogen fertilizer in the two areas, content of NO3- in groundwater is gradually increasing. As the intensity of human activities strengthens the groundwater exploitation increases year by year. Groundwater updated soon so that the content of each ion showed a downtrend in recent years.?5? Unconfined water Vulnerability was evaluated in Ruoqiang-Qiemo region. Range of unconfined water vulnerability index was 3.61⁸.64. Area of low, moderate, high and extra high vulnerability was account for 7.8%, 35.8%, 52.5% and 3.9%, respectively. Among all the unconfined water sampling points, X71 with the highest pollution index?0.85? is located in the highly vulnerable area.