| The groundwater samples of a typical wastewater irrigation area were collected and analyzed including 15 inorganic components,22 organic components,2 aerobic components, and 3 bacteria components. Two methods were used to assess the groundwater quality of the sewage irrigation; single factor index method was used to assess the pollution degree of the sewage irrigation area. The results show that, though the irrigation water quality has been improved, groundwater is still polluted by some components. Main pollution components include SO42-, nitrogen, total hardness, TDS, bacteria, what's worse, in addition, total coliform exceed standard seriously.With the use of ARCGIS, plane distribution columnar section of pollutants was drew to analyze the characteristics of groundwater pollution. And comparison was made between 2008 and 2014, to analyze pollution source of groundwater, find that the pollution source is as follows:1.accumulated effect of long time sewage irrigation; 2.furthur filtration from soils polluted by sewage irrigation; 3. agricultural fertilization.In addition, predict the diffusion of N?TDS?total hardness and total coliform at downstream of the first aquifer and lower aquifers in the next 30 years by building proper numerical simulation on the basement of hydrogeology conditions of the study area, the result shows that there are effects on both horizontal and vertical directions, but hasn't reached deep aquifer. Then sensitivity analysis was made to permeability coefficients, dispersivities, adsorption coefficients, degradation coefficients, and scenario analysis were made of pumping levels, pumpages, positions of pumping wells and skylight, to identify the main controlling factors, then proposed prevention and control scheme. |
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