Saenz, H.

Six years of monitoring HCO3- and pH at selected springs at Popocatepetl during the present eruptive period are presented. Small peaks in HCO3- concentration and PCO2 in springs are associated with small magmatic pulses at Popocatépetl volcano. The magma provides CO2-rich fluids into the water system controlled by meteoric recharge. The PCO2 in equilibrium with the springs is two to four orders of magnitude higher than air-saturated water. The high partial pressure of CO2 also suggests a direct interaction with the magmatic fluids. The isotopic signature of carbon as well, supports a magmatic origin for dissolved CO2.