Once injected in a well, CO2 plumes will rise via buoyant forces, due to lower density than its surroundings. CO2 then spreads laterally upon encountering caprock until it finds a gap. Fault planes or fracture networks near the injection zone increase the possibility of gaps, which would be potentially dangerous to life in the surrounding area. CO2 can potentially migrate into shallow groundwater aquifers and compromise water quality by releasing trace metals such as Sr, Zn, Co, and Ba, and organic compounds, and/or change the water's pH. Deep coal seams that are not economically viable sources for coal mining are generally used for sequestration of CO2. Despite the many advantages of these sites, the injected CO2 chemically and physically alter the coal matrix and induce its swelling and mobilization of polycyclic aromatic hydrocarbons (PAHs) in the coal seam. This mobilization of PAHs may cause environmental issues as PAHs are harmful even at relatively low concentrations.