Chemical characterization of rain in Córdoba City, a study of the deposition process

Full text: Sequential samples of single precipitation event were collected between December-2011 and September-2012 in Córdoba, Argentina. The temporal evolution of the pH value, electrical conductivity and the concentration of the elements S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, and Pb were analyzed. The samples were analyzed by Synchrotron Radiation Total Reflection X-Ray Fluorescence (SR-TXRF) by using the XRF line at the Brazilian Synchrotron Light Source Laboratory (LNLS). The results show a high variability of the variables (pH, electrical conductivity, concentrations) at the initial stage of precipitation and a sharp decreasing as event progress. The average scavenging coefficients for the analyzed elements were calculated. It is found that for the soluble fraction at the initial state of precipitation, Ca, K and S contribute with ≈ 95% of the mass concentration and they show the highest coefficients for the washout process. For the insoluble fraction, K, Ca and Fe contribute with ≈ 60 % of the mass concentration at the onset of precipitation. Assuming that the amount of pollutants available for scavenging are insignificant for large precipitation depths, the chemical elements (within the analyzed elements) acting as cloud condensation nuclei were inferred. (author)