| The characteristics of hydrochemistry and geochemistry of the shallow groundwater could reflect the weathering intensity of the rock. As the product of the weathering denudation, the soil influence the chemical constituents of the underground water significantly. Meanwhile, the water environment quality, elements distribution of the water and the characteristics of regional environmental chemistry all could be represented largely by chemical constituents of the water.The characteristics of two types of shallow groundwater in the soil are treated as the starting point in this article, including the red soil and the paddy soil. And the hydrogeochemical characteristics of the shallow groundwater in the Poyang Lake Basin are researched through the sample collection and analytical test. The conclusions are as follows:(1) The shallow groundwater in the Poyang Lake Basin is supplied by the meteoric waters.The surface water and shallow groundwater distribute near the local meteoric water line, which indicate the close hydraulic connection between the surface water and groundwater.(2) The pH of the shallow groundwater in red soil layer range from 4.89 to 6.6, Eh range from90 mV to 382 mV, and the TDS range from 25.1 to 152.9mg/L, that lower than the average of the value in subtropical monsoon climate. The pH increase with the value of TDS, and the main hydrochemical type include the HCO3-Ca, HCO3-Na-Ca and SO4-Ca-Na. The kaolinite, iron hydroxide and low concentration Al-Mn compounds are in the equilibrium state except some original mineral. The Si-OH bonds in the kaolinite always form the H bonds through the Fe-OH bonds in the Hematite and goethite. And the iron ion are enriched in the crystal lattice of the kaolinite frequently.(3) The pH of the shallow groundwater in paddy soil range from 6.3 to 7.7, Eh range from67 mV to 354 mV, and the TDS range from 160.8 to 595mg/L, that higher than the average of the value in subtropical monsoon climate. The pH increase with the value of TDS slightly, and the main hydrochemical type is the HCO3-Ca. Eh of the groundwater range from-68 to-91 mV in partial areas, the NO3- range from 0.20 to 0.24 mg/L. And the concentration range of the Fe2+,SiO2, F-, NH4+ are 11.1~40.2 mg/L, 22.6~41.2 mg/L, 0.12~1.03 mg/L, 1.95~6.40 mg/L and1.03~5.53 mg/L, respectively. The montmorillonite, illite, a handful of kaolin and iron-compound of the groundwater in paddy soil belong to the equilibrium state.(4) The groundwater quality in the Hukou, Duchang, Tacheng and Yongxiu area are good. Alittle slight pollution are happened in the Poyang, Leping and Wannian area. And the groundwater quality are bad in the Lianhu, Yugan and Ruihong area.(5) In the serious-polluted areas, the existing forms of harmful elements are:①the As mainly exist in the form of HAsO2 and As(OH)3, and the content of HAsO2 is higher. The content of HAsO42- increase with the pH in other test points, but the content of H2AsO4- decrease. ②High valence Cu mainly exist in the form of the CuCO3、Cu2+ that occupy 74%~92% in the total Cu.The low valence Cu mainly exist in the form of the Cu+. And the activity of the high valence Cu increase with the Eh in the existing form of Cu. ③Cd mainly exist as the stable form, like Cd2+type and CdCl+ type, that the content of Cd2+ is relatively higher which occupy the 73%~97% of the total Cd. ④The Pb mainly exist as the PbCO3、Pb2+、PbOH+ and little PbCl+, Pb(CO3)22-.⑤The Zn mainly exist as the Zn2+ which distribute unequally. The phenomenon need to pay attention to that Ⅳ-water appear in local area. |
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