Study On Contamination Characteristics And Mechanism Of Groundwater In Lvcheng Area Of Danyang Based On Solute Transport

Groundwater is the major constitution of water resource system, as well as a sensitive factor among environment ecological system, brings great influence on human life and the industrical and agricultural production. However, unreasonable human activities result in the decrease of groundwater quality, and trigger a series of groundwater contamination. This paper first regards Lvcheng area of Danyang as study object, making study and discussion of contamination characteristics, contamination situation, stratum structure and mechanism of contamination by collecting data, investigation and sampling, testing and analysis as well as numerical simulation, then obtain some processing and new understanging in six aspects:1. Overall contamination characteristic in Lvcheng area of Danyang is mainly inorganic pollution, and organic pollution appeared as well. It concretely manifestes that inorganic regular indices are the most serious, and inorganic toxicological indices are worse than trace organic indices. Five inorganic regular indices involving Mn, TH, Fe, NH4+,CODMn exceed Ⅲ class limitation, and four inorganic toxicological indices including I-, F", NO3- and As exceed Ⅲ class limitation. Meanwhile, three type organic indices covering halohydrocarbon, chlorobenzene and mononuclear aromatics present in groundwater sample, there are thirteen kinds of organism totally.2. Signigicant change of water chemical types in Lvcheng area are found out. It indicates that the number of hydrochemical type has been increased to nine from two previously. And recent types are mainly HCO3-Ca and HCO3-Ca·Na·Mg. The former distributes intensively, but the later distributes relatively dispersive. The groundwater is influenced by human unreasonable activities, HCO3·Cl type water has existed in southeastern area of chemical industry park and northern residence as the result of evolving. All values of total dissolved solides are less than 1g/L, so belongs to fresh water.3. Groundwater quality recent situation is obtained by using various methods. It is evaluated by single index evaluation method, classification index evaluation method and comprehensive quality evaluation method, respectively. During single index evaluation, the quantity and percentage of inorganic indices which exceed III class limitation are far more than those of organic indices. Within the scope of space, quality level gradually becomes lower along with the increasing distance away from chemical industry park. Groundwater inferiority during classification quality evaluation manifests that general chemical indices>inorganic toxicological indices>volatile organic indices>toxic heavy metal indices>semi-volatile organic indices. The results of comprehensive quality evaluation indicate that groundwater quality is relatively worse, and the main quality is Ⅳ level, meanwhile, lack of Ⅰ level and Ⅱ level, the properity of III level occupies nearly 1/5 of total samples and that of V level occupies about 1/10.4. Groundwater contamination recent situation evaluation of Lvcheng area is conducted by single index contamination evaluation method and the latest comprehensive method which combines stepwise evaluation with comprehensive integration. The results of single index evaluation reveal that groundwater is mainly non-contamination, slight contamination and moderate contamination. Serious contamination indeces include Mn, Fe, As and CHCl3. Based on groundwater quality, the comprehensive method chooses inorganic toxicological indices and trace organic indices, which both have great impact on human health, as evaluated factors. The result indicates that the percentage of non-contamination groundwater occupies 2/3, that of slight contamination and heavy contamination occupies 1/3.5. Based on predecessors’ material and recent drilling data, meanwhile, integrating stratum division method with experts’ advice, stratum layers of study area are redefined and divided. Three-dimensional geological model is set up using GMS software, making stratum structure observation from various perspective, different layers and arbitrary section come true.6. To establish hydrogeological conceptual model and mathematical model, solute transportion in groundwater is predicted under the effect of convection and dispersion. It shows that pollutant mainly concentrates within the scope of chemical industry park at initial five years, and pollutant will infiltrate groundwater as the production going on, eventually, pollutant go forward nearly 769 meter along the groundwater flow direction in thirty years, as well as the influenced area by contamination plume from initial 0.145 square kilometer increased to 0.58 square kilometer.