Trace metals and inorganic ion measurements in rain from Mexico City and a nearby rural area

Abstract

Rain is a main source of water for the ecosystem in Mexico. Emitted particulate matter and gases enter the ecosystem by rain scavenging. Although the chemistry of rainwater has been the subject of a number of studies, the insoluble fraction has been virtually ignored. This fraction is made up of particulate material, and can be significant, particularly in rural forest regions. Average aluminium weights were the highest of all elements, in both the soluble and insoluble fractions. Ions with the highest concentrations were and , followed by , Na+, Cl−, Ca2+, Mg2+ and K+. The Spearman rho correlation showed that the acidity was caused by and , and the most important neutralising ion was . High crustal enrichment factors (EFcrusts) suggested that Mexico City in general was richer in Cd, Cr, Mn, Pb, and V than Rancho Viejo. The enrichment factors support the idea that the metals observed in rainwater have an anthropogenic origin. Air mass back trajectories were associated with the concentrations of trace metals and of , Ca2+, Mg2+, and observed during each rainy day.