Groundwater Systems and Resources in the Ordos Basin,China

The Ordos Basin is a large-scale sedimentary basin in northwestern China. The hydrostratigraphic units from bottom to top are pre-Cambrian metamorphic rocks, Lower Paleozoic carbonate rocks, Upper Paleozoic to Mesozoic clastic rocks and Cenozoic deposits. The total thickness is up to 6000 m. Three groundwater systems are present in the Ordos Basin, based on the geological settings, i.e. the karst groundwater system, the Cretaceous clastic groundwater system and the Quaternary groundwater system. This paper describes systematically the groundwater flow patterns of each system and overall assessment of groundwater resources.

Vulnerability Assessment of Shallow Groundwater in Ordos Cretaceous Basin

[Objective] The aim was to evaluate the vulnerability to pollution of shallow groundwater in Or（los Cretaceous Basin system. [Method] Mathematical modeling, GIS spatial analysis and multivariate statistical analysis technologies were introduced to improve the traditional groundwater vulnerability assessment model of DRASTIC in view of its strong subjective for expert estimation and weight assigning. In the meantime, the intensi- ty and reasons of vulnerability to pollution of groundwater in the area were studied, and measures to protect local groundwater were proposed. [Resultl Using improved DRASTIC method to assess the vulnerability to pollution of groundwater in Ordos Cretaceous Basin system was objective and reliable. The application of fertilizer was the main influential factors to the vulnerability to pollution of groundwater in Ordos Cretaceous Basin sys- tem. It was advised to lessen the usage of fertilizer and not to drink water from lake or deep ground water. Density, rock, and evaporation were fac- tors that led to intensive vulnerability to pollution of groundwater in shallow areas. [ Conclusion] The study provided a new method for the evaluation of vulnerability to pollution of groundwater in Ordos Basin.

Characteristics-based classification research on typical petroleum contaminants of groundwater

Petroleum pollution has become an important factor to threaten the groundwater environment, and the classification of its typical characteristics will contribute to pollution assessment and environmental management. Under the same hydrogeological features condition, the reaction of typical petroleum pollutants in groundwater depends on the characteristics. This paper takes the typical toxicity, oil pollutant migration, degradation, water-soluble etc. as evaluation indexes, and with AHP method the typical petroleum pollutants in groundwater are divided into four classifications according to comprehensive calculated values: comprehensive value≥2.5, Class I hazardous pollutant; 2.0≤comprehensive value<2.5, Class II hazardous pollutant; 1.5≤comprehensive value<2.0, Class III hazardous pollutant; comprehensive value<1.5, Class IV hazardous pollutant. The pollutant group shall be managed according to the classification, and obtained classification list will provide technical support for priority monitoring and priority repair of groundwater environmental management.

Study on the Effect of Underground Temperature on the Adsorption Behavior of Chlorobenzene under Artificial Recharge Condition

[ Objective] The research aimed to study the effect of underground temperature on the adsorption behavior of chlorobenzene under artifi- cial recharge condition. [ Method] Based on the prior researches, combining actual condition of the artificial recharge test site, the adsorption be- havior of chlorobenzene under the background of artificial recharge was discussed. [ Reset ] The adsorption reaction of chlorobenzene correspon- ded with quasi-first-order and quasi-second-order kinetics equations at certain concentration. When temperature rose, reaction rate accelerated, and adsorption balance time shortened to 12 （0 ℃）, 10 （10 ℃） and 8 （20 ℃） h. The adsorption of chlorobenzene corresponded with isothermal adsorption model very well at different concentrations. When temperature ranged from 0 to 20 ℃, the adsorption amount of medium on chloroben- zene increased at equilibrium time. The maximal adsorption amounts calculated by Langmuir model were 20.747, 21. 505, 23.364 μg/g at 0, 10 and 20 ℃, respectively. [ Conclusion] The adsorption of chlorobenzene in aquifer medium was endothermic reaction, and the best season of artifi- cial recharne was in summer.

Spatial distribution patterns of wetland plants in relation to environmental gradient in the Honghe National Nature Reserve, Northeast China

Quantifying correlation between the spatial patterns of natural wetland plants and environmental gradient gives better understanding of wetland habitats, which is the fundamental for the strategy making on the protection and restoration of natural wetlands. In this study, the spatial patterns of wetland plants and the environmental gradient of wetland habitats were assessed in the Honghe National Nature Reserve （HNNR） in Northeast China, a wetland of international importance on the Ramsar list. Biophysical parameters’ values of wetland plants were obtained by field sampling methods, and wetland mapping at the community scale was completed using remote sensing techniques. Digital delineation of the surface water system, hydrological zoning and wetness index were produced by spatial analysis methods in Geographic Information System. An ecological ordination method and two clustering methods were used to quantify the relationship between the spatial distribution patterns of wetland plants and the corresponding environmental gradients. Such quantitative analyses also present the specific diversity of different types of wetland plants based on the environmental attributes of their habitats. With the support from modern geo-information techniques, the experimental results indicate how four ecotypes of wetland plants spatially transit from forest swamp, shrub wetland and meadow into marsh wetland with increasing wetness index and water table. And they also show how wetland spatial distribution patterns are controlled by an environmental gradient of wetness. Another key finding of this research work is that our results present the exact fundamental differences between marsh and non-marsh plants of 11 wetland plant communities within the core study area. Hence, this case study gives a good sample for better understanding of the complex correlation between the spatial patterns of wetland plants and their environmental attributes using advanced digital analysis methods. It is also useful to show how to integrate geoinformatic techniques with statistical analysis methods based on the field data base.

Performance and Mechanisms of Fluoride Removal from Groundwater by Lanthanum-aluminum-loaded Hydrothermal Palygorskite Composite

Lanthanum-aluminum loaded hydrothermal palygorskite（La-Al-HP） composite was prepared and selected as adsorbent for the fluoride removal from simulated groundwater. The adsorbent was characterized by scanning electron microscopy（SEM）, Brunauer-Emmet-Teller（BET） analysis, X-ray diffraction（XRD） analysis and X-ray pho- toelectron spectroscopy（XPS）. SEM visualization shows that the dense surface structure of raw HP appeared loose and presented micro canals after modification. The BET analysis also proved the specific surface area of La-Al-HP composite（95.58 m^2/g） was higher than that of the raw HP（34.31 m^2/g）. Subsequently, the adsorption capacity of La-Al-HP composite was demonstrated in adsorption experiments. The kinetics of fluoride ion adsorption into La-Al-HP composite followed the pseudo-second order with a correlation coefficient of 0.997. The isotherm data was well fitted with the Langmuir model. The monolayer adsorption capacity of La-Al-HP composite was 1.30 mg/g. The XRD and XPS results reveal that the La^3＋ and Al^3＋ ions were loaded on the surface of modified HP and the fluoride ion was adsorbed onto the La-Al-HP composite. A large amount of La-Al-O composite oxide existing on the surface of La-Al-HP composite might be the immanent cause for the excellent adsorption capacity of fluoride ions.