Sampling the Amazon estuary
During spring 2025, one of our PhD students joined the international GEOTRACES cruise GApr21 (RV Meteor cruise M206) along the Brazilian margin. Below, she summarises the goals of her project, the sampling strategy on board, and the next analytical steps that will shed light on trace‑metal fluxes from the Amazon system to the Atlantic Ocean.
Rivers are a major source of trace elements to the ocean, but their contribution is difficult to quantify because many transformations occur at the river–sea interface. In estuaries, rising salinity can change metal speciation and behaviour. My research targets the isotopes of nickel (Ni) and molybdenum (Mo) to better understand the processes that control trace‑metal fluxes from land to ocean—especially the roles of the Amazon River, the Pará River, and groundwater inputs from the surrounding mangrove belt in shaping Atlantic biogeochemistry.
To collect the necessary samples, I sailed on cruise M206 aboard RV Meteor, led by Prof. Andrea Koschinsky (Constructor University, Germany). Over one month at sea we worked our way north from Fortaleza, sampling the mangrove belt, the Pará and Amazon estuaries, and the offshore Amazon plume as far as French Guiana.
Trace‑metal work requires a very clean working environment, so most of my time was spent inside a “clean bubble”: a portable laboratory with HEPA‑filtered laminar‑flow hoods that keep airborne particles to a minimum. Full‑body protective suits ensured that we did not contaminate the samples we were handling at ultra‑trace levels.
We collected water with two main systems. A towed instrument array
(“Tow‑Fish”) pumped surface water directly into the lab, while a
trace‑metal‑clean rosette equipped with GoFlo bottles retrieved deeper
samples. Back on deck, I filtered each sample to separate the dissolved
(< 0.2 µm) and particulate (> 0.2 µm) fractions.
The next stage will be shore‑based: measuring Ni and Mo concentrations and isotopic compositions. These data will help unravel the mechanisms that control trace‑metal cycling in tropical estuaries and coastal waters, ultimately
refining global budgets for these environmentally important elements.
Contact Information
Professur für Geochemie
Clausiusstrasse 25
8092
Zürich
Switzerland