... Yen, Phuc Yen, Ha Tay, Hai Duong, Hung Yen, and Bac Ninh provinces [4]. 3. Conclusions On the basis of frequency distribution, the main characteristics of quantitative distribution of chemical components of groundwater in the ... Table 1. Frequency of SO42- concentration in rainy season of Holocene aquifer ions concentration also conforms a slanting distribution. Therefore, the fact that the average value is considered as a representative mean is ... sodium ions concentration in dry season of Holocene aquifer. Two kinds of ion group in Holocene aquifer in RRD can be distinguished based on the probability distribution law. The ...