Groundwater Age And Recharge Temperature In The Quantenary Aquifers In North China Plain

Environmental problems, such as land subsidence, saline water intrusion, and water quality degradation, occurred in the North China Plain (NCP) due to groundwater overexploitation. The studies on groundwater age and recharge temperature in NCP can provide some valuable information about hydrologic cycle and groundwater resources renewability. These information is vital for groundwater groundwater resources management.Groundwater and gas samples,including stable isotopes 2H and18O , radioisotopes3H and 14C , environmental tracer SF6 , and noble gas, were collected along the transect of Shijiazhuang to Tanggu from wells of Quaternary aquifers. The noble gas temperature(NGT) and excess air were explained by using the CE model, SF6 and 3 H ? 3He approaches were used for young groundwater dating in the piedmont, While 14C and 4He approaches were used for waters in the central and littoral plain.The major results as fallows:(1) The NGT suggested that the recharge temperature of young groundwater is about 5oC lower than that of old groundwater. It is also meaning that the climate now is being warmer than past.(2) The SF6 age and 3 H ? 3He age of groundwater in piedmont indicated that they were modern waters. The groundwater is sustainable and quickly renewable.(3) The component of helium indicated that the crust helium isotope ratio is 4.05E-8 in NCP, and the concentration of tritiogenic helium-3 in the confined aquifers in NCP range from 6.97 to 10.95E-15 cm3STP/g , equeal to the tritium range from 2.8TU to 4.4TU.(4) The uncorrected 14C age of confined waters in the central and littoral plain range from 12 ka to 44 ka, in contrast,the 4He age range from 8.2 ka to 351ka. They were similar in the middle Pleistocene aquifer, while 4He age is apparently larger than 14C age in the lower Pleistocene aquifer, and exhibit the characteristic of fossil water. The water resources can be considered as nonrenewable groundwater resources.