Identifying spatio-temporal variation and controlling factors of chemistry in groundwater and river water recharged by reclaimed water at Huai River, North China

摘要

Reclaimed water is efficiently used to recover the dry river, but river water and groundwater may be impacted considering the water quality. Thus, it is critical to study the factors controlling water chemistry. Samples of reclaimed water, river and groundwater were collected monthly from January to September in 2010, in Huai River (North China). And samples were analyzed for major 15 physio-chemical parameters. Using hierarchical cluster analysis, 9 months are divided into two distinct groups, which show the clear temporal variation. In reclaimed water and river water, one group includes February, while the other includes other months. In shallow and deep groundwater, one group includes months from January to April, while the other encompasses others. Monitoring stations are classified into three groups. Group A with high value of ions and nitrogen (order: NH_4-N ＞ NO_3-N ＞ NO_2-N) includes reclaimed water and river water. Group B with moderate concentration and nitrogen (order: NO_3-N ＞ NH_4-N ＞ NO_2-N) includes all shallow ground water and one deep groundwater. Group C with the low value and nitrogen (order: NO_3-N ＞ NO_2-N ＞ NH_4-N), includes two deep groundwater. Using multivariate analysis and ionic relationships, river water chemistry is found to be controlled by reclaimed water and evaporation process; chemistry in shallow groundwater and one deep groundwater, with type of Na-Ca(Mg)-HCO_3-Cl, is controlled by dissolution of calcite, carbonate weathering. Additionally, reactions of nitrification, denitrification and cation exchange occur in the infiltration of reclaimed water; chemistry in the other deep groundwater, with type of Ca-Mg-HCO_3-Cl, is controlled by dissolution of calcite, carbonate weathering and denitrification.