Some overlaps in Group 2 pore-water and the second confined groundwater samples were observed (Figure 7), indicating that the vertical diffusive mixing between the porewater and aquifer groundwater possibly existed.
Fu, The Hydrochemical Characteristics And Processes for Salinity Sources of The Deep Confined Groundwater in The Coastal Plain of Huai River Basin, Jilin University, 2015.
As shown, the TDS of the unconfined groundwater varies from 149 mg/L to 823.39 mg/L with a mean value of 360.28 mg/L; that of the middle confined groundwater ranges from 64.31 mg/L to 252.94 mg/L with an average value of 124.47 mg/L; and that of the deep confined groundwater changes from 99.52 mg/L to 325.98 mg/L with a mean value of 158.01 mg/L.
As shown, the unconfined and middle confined groundwater show a relatively large range in the rhombus area (areas I and II).
Figure 4 also shows that the deep confined groundwater samples, which are distributed mainly in the bottom-left corner of rhombus area (II), are mainly represented by HC[O.sub.3]-Na x Ca(Mg) hydrochemical type, indicating that deep confined groundwater naturally evolves without any intensive hydrogeochemical process or anthropogenic impact.
The isotopic compositions of [delta][sup.2]H and [delta][sup.18]O of the middle confined groundwater vary from -43.60[per thousand] to -52.90[per thousand] (average: -47.58%) and from -6.42[per thousand] to -7.42[per thousand] (average: -6.91[per thousand]), respectively.
For the middle and deep confined groundwater, as shown in Figure 5, the distribution of the confined groundwater samples presents a pattern: the deeper the aquifer depth is, the more depleted the isotopic data are.
As shown in Table 3, the ([Na.sup.+] + [K.sup.+])/[C1.sup.-] ratio values of the unconfined groundwater vary from 0.38 to 4.44 with an average value of 1.58; those values of middle confined groundwater range from 0.57 to 6.28 with an average value of 2.22; those values of deep confined groundwater change from 0.91 to 25.03 with average value of 6.95.