Geochemical Characteristics And Assessment, Prediction Of Shallow Groundwater In The Nansi-Lake Area

Nansihu Lake is the largest freshwater lake in North C hina Plain. The Nansihu Lake area plays a key role in the industry and agriculture in Shandong Province, and its main water supply is from local groundwater. However, the water quality and the distribution of ions concentrations were influenced by both the natural conditions and the anthropogenic activities.To study the geochemical characteristics of shallow groundwater in the Nansihu area, 43 samples were collected, and their ions concentrations, hardness, TDS and p H value were measured. The hydro-chemical types of the waters were defined as HCO3-Ca. The Gibbs plots showed that the major ions in the waters were mainly originated from water-rock interaction; the results of the stoichiometric analyses suggestive of the influence of human activities; the variance of both multi-annual rainfall and hydro-chemicals illustrated that the chemicals of the waters were apparently influenced by the evaporation and precipitation. Through the Single Factor Evaluation, the NO3- concentrations in 31 samples, the Pb concentrations in16 samples, and the Hardness in 21 samples exceeded the Limit of Water Standard Ⅲ. These factors were considered to cause the degradation of the water quality. Through the Comprehensive Evaluation, the water quality in 74.42% of the whole area exceeded the Limit of Water Standard Ⅳ.In order to prevent and control the pollutions in shallow groundwater, the modeling software of groundwater environment, GMS, was used to predict the distribution and evolution of the chemical components in shallow groundwater. The results showed that in the next 5-10 years, the equal water levels in Nansihu Lake area would drop slowly, and a large number of ions could transfer to the position around the Lake, especially the accumulation of NO3- and Pb there.