Concentration-Discharge Relationships of Al, Transition Metals, and Rare Earth Elements in the Santa Catalina Mountains- Jemez River Basin Critical Zone Observatory

Abstract:

The Concentration-Discharge relationships of solutes in stream waters during high-volume storm events are of interest when studying influencing factors of weathering. While base cations (Na, K, Mg, Ca) have been widely characterized in terms of concentration-discharge relationships, little is known in regards to Al, transition metals, and rare earth elements, which typically demonstrate a positive concentration-discharge relationship, unlike their cation counterparts. We performed a cascade-filtration (at 1.2μm, 0.4μm, and 0.025μm) of stream water samples collected during a monsoon storm event at the Marshall Gulch site of the Santa Catalina Mountains-Jemez River Basin Critical Zone Observatory and used standard stream water analytical techniques to determine concentration-discharge relationships. This yielded positive concentration-discharge relationships for Al, transition metals, and rare earth elements. Additionally, using the ratio of 0.025um-filtered samples to 0.4um-filtered samples, we find that these species (Al, transition metals, rare earth elements) were not completely dissolved in stream water. This partial dissolution, in conjunction with the positive concentration-discharge relationship, implies the complexation of these species to colloids or dissolved organic matter during stream-water transport.