Hydrogeochemistry of the Mid-levels Area, Hong Kong

Groundwater and seepage samples were collected from both the natural and building-modified slopes in the highly urbanized spaces of the Mid-Levels area, Hong Kong. Groundwater in the natural slopes, although retaining some signatures from rainwater, is enriched in major cations such as Na, K, Ca and Mg and some anions such as HCO3 and SO4. Clearly, water-rock interactions, such as weathering of plagioclase feldspar, play a significant role in the hydrogeochemistry of this area. On the developed slopes, the subsurface hydrogeochemical system is more complex. Here samples are dominated by Na-Cl and Na-Ca-Cl complexes and vary significantly in total dissolved solid (TDS). It is evident that groundwater from the developed area is contaminated by leakage from flushing water mains (mainly sea water) to different extents. It is believed that dissolution of concrete materials may also contribute calcium to the groundwater.