In the rubber dam's impact area, the groundwater total hardness (TH) has declined since 2000, ultimately dropping to 100-300 mg/L in 2012. pH levels have shown no obvious changes. NH<inf>4</inf>-N concentration in the groundwater remained stable from 2000 to 2006, but it increased from 2007 to 2012, with the largest increase up to 0.2 mg/L. NO<inf>3</inf>-N concentration in the groundwater generally declined in 2000-2006 and then increased from 2007; the largest increase was to 10 mg/L in 2012. Total dissolved solids (TDS) of the groundwater showed a general trend of decline from 2000 to 2009, but levels increased after 2010, especially along the south bank of the Luohe River where the largest increase recorded was approximately 100 mg/L. This study has shown that the increases in the concentrations of NH<inf>4</inf>-N and NO<inf>3</inf>-N were probably caused by changes in groundwater levels. Nitrates adsorbed by the silt clay of aeration zone appear to have entered the groundwater through physical and chemical reactions. TDS increased because of groundwater evaporation and some soluble ions entered the groundwater in the unsaturated zone. The distance of the contaminant to the surface of the aquifer became shorter due to the shallow depth of groundwater, resulting in the observed rise in pollutant concentrations more pronounced.
Dong, S., Liu, B., Liu, H., Wang, S., & Wang, L. (2014). Impacts of groundwater recharge from rubber dams on the hydrogeological environment in Luoyang Basin, China. Scientific World Journal, 2014. https://doi.org/10.1155/2014/183457