Strontium isotope variations in the lower Mississippi River and its estuarine mixing zone

The spatial and temporal variations of elemental and isotopic Sr in the Mississippi River (MR) mixing zone are examined in an attempt to address the extent to which estuarine environments modify the fluvial Sr flux on its way to the ocean. We collected samples from the MR delta and its outflow region during four cruises that took place from 1999 to 2002. MR discharge varied from about 7600–30,600 m3 s− 1. Mixing patterns revealed minimal non-conservative behavior of Sr in the dissolved pool. Monthly measurements of the Lower MR at an anchored site during 2000 shows that Sr input to the Gulf of the Mexico from the MR varies temporally in both elemental concentration and isotopic composition, and that the flux of Sr is largely a function of water discharge. The extent of the non-conservative geochemical behavior of Sr does not compromise the use of Sr isotope ratios for stratigraphic dating purposes.