Abstract

Groundwater quality in Beijing, China was evaluated by measuring the quantities of major and minor elements, temperature, pH, total dissolved solids (TDS), and electrical conductivity (EC). Most samples contained high concentrations of NO₃^– (5.13 to 164.0 mg/L), which is a serious water quality issue. This NO₃^– originates from the soil surface and enters the groundwater by infiltration. Factor analysis modeling demonstrated that NO₃⁻, Cl⁻, SO₄²⁻, Ca²⁺, and Mg²⁺ in the system are produced by anthropogenic sources, but a portion of the (Ca²⁺, Mg²⁺) comes from ion exchange and mineral dissolution. The strong correlation observed between NO₃⁻ and Ca²⁺, Mg²⁺, Cl⁻ and SO₄^2- suggests that they have the same origin. The parameters in Factors 1–3 reflected the importance of the acid-rain recharge of the aquifers in the area, anthropogenic impact and salinity, respectively. Hierarchical cluster analysis was used to group the wells into homogeneous zones for future monitoring of groundwater quality. Multivariate statistical techniques were used to identify key parameters that described the groundwater quality, characterize spatial variability of groundwater quality data and allow future groundwater quality control studies to be performed using a reduced number of measurements on a small number of sampling points, respectively.

Key words: Groundwater, hydrochemica, multivariate statistical, nitrate, contamination.