Jeff Perez

3 more days until the abstract deadline for @goldschmidt-confer.bsky.social 2026 in Montreal!

If you are working on elemental cycling and fluxes in polar environments, please consider submitting an abstract to our Goldschmidt Session 9b: shorturl.at/JYoSu.

Icy river winding through snow and basalt under a low winter sky in Iceland.

Last day as a Discovery Research Fellow — same island, new questions. Grateful to @gfz.bsky.social for this wonderful opportunity.

Fresh Iceland work starts now. @anneeberle.bsky.social @lianegbenning.bsky.social

I have a fully funded PhD position open for start in Jan or May 2026. Field work in peatlands of the Northwest Territories, with lab work to understand potential downstream mobilization of carbon, nutrients, mercury after thaw or wildfire. Reach out for more information, and please send on!

📅 DEI Session: Weds July 9 , 8:30 Club C (1st Floor)
Join our #DEI session “Geochemistry beyond stereotypes: solving tough scientific issues & advancing diversity, equity & inclusion” to explore lived experiences & strategies for a more inclusive geochem community
@eageo.bsky.social

Excited to share our new collaborative paper with @vanvillegas.bsky.social! 🧪

Proud to have contributed through the Envi Mineralogy & Biogeochemistry Labs @lianegbenning.bsky.social & @forjanes.bsky.social.

Big thanks to @mimilovesmilo.bsky.social for a great collab during her @daadworldwide.bsky.social RISE internship at @gfz.bsky.social!

And grateful to @diamondlightsource.bsky.social for beamtime at I20-scanning that allowed us to "look" inside the crystal structure of these minerals. 💡💠

Coexisting Phosphate Controls Arsenate Speciation and Partitioning during Fe(II)-Catalyzed Ferrihydrite Transformation Arsenic immobilization in soils and sediments is primarily controlled by its sorption onto or incorporation into reactive soil minerals, such as iron (oxyhydr)oxides. However, coexisting ions (e.g., dissolved bicarbonate, phosphate, silica, and organic matter) can negatively impact the interaction of the toxic arsenate species with iron (oxy)hydroxides. Of special note is inorganic phosphate, which is a strong competitor for sorption sites due to its analogous chemical and structural nature to inorganic arsenate. Much of our understanding of this competing nature between phosphate and arsenate focuses on the impact on mineral sorption capacities and kinetics. However, we know very little about how coexisting phosphate will alter the stability and transformation pathways of arsenate-bearing Fe (oxyhydr)oxides. In particular, the long-term fate and behavior regarding arsenate immobilization are unknown under anoxic conditions. Here, we document, through mineral transformation reactions, the immobilization of both phosphate (P) and arsenate [As(V)] in secondary mineral products and characterize their changing compositions during the transformations. We did this while controlling the initial P/As(V) ratios. Our results document that, in the absence or at low P/As(V) ratios, the initial ferrihydrite rapidly transforms to green rust sulfate (GRSO4), which further transforms into magnetite after 180 days. Meanwhile, high P/As(V) ratios resulted in a mixture of GRSO4 and vivianite, with magnetite as a minor fraction. Invariably, the speciation and partitioning of As(V) were also affected by the P/As(V) ratio. A higher P/As(V) ratio also led to a faster partial reduction of mineral-bound As(V) to As(III). The most important finding is that the initial ferrihydrite-bound As(V) became structurally incorporated into magnetite [low P/As(V) ratio] or vivianite [high P/As(V) ratio] and was thus immobilized and not labile. Overall, our results highlight the influence of coexisting phosphate in controlling the toxicity and mobility in anoxic, Fe2+-rich subsurface settings, such as contaminated aquifers.

New paper out! 🎉

How does #phosphate, a common nutrient in fertilizers, influence the behavior of toxic #arsenic in soils and groundwater?

We show that phosphate levels affect how well arsenate can be locked inside iron minerals, controlling its toxicity and mobility.

🔗: tinyurl.com/3k254ebf

Very excited to share my first 100% @gfz.bsky.social paper on mineral pseudomorphism with my Interface Geochemistry fantastic team! @lianegbenning.bsky.social @jeffperez.bsky.social

First day back at work after my #PH holidays 🌴🌞 and going through hundreds of emails 😵

Despite a fellowship rejection, we had a couple of manuscripts accepted, and the reviewer comments on my last manuscript were all quite positive! 🤞

What a great start to the month!

📣 Only 7 days left until the abstract deadline for #Goldschmidt2025! @goldschmidt-confer.bsky.social

If you are working on elemental cycling and transport in polar environments, please consider submitting an abstract to our Goldschmidt Session 8e: shorturl.at/d4yNf.

Hope to see you in Prague!

📣 Researchers wanted!

3x #PhD and 1x #PostDoc positions available in the #EnviChem group @lthomasarrigo.bsky.social at UniNeuchâtel CH. The topics are interesting + Laurel is an amazing mentor. Come and join their lab! #geochem #soil #mineralogy #carbon

More info below 👇

Meet one of our handling editors - Raúl Fonseca. He talked about what were his main motivations to join AGC and why he thinks that researchers should support DOA publishing. Can you guess why S is his favourite element?
Follow the link to the full interview https://buff.ly/3E9d173
Publish with AGC!

Spread the word📢 Please repost this msg so that we can build the #geochemistry community 👨‍👨‍👧‍👧 on Bluesky. Follow the European Association of Geochemistry for regular updates on: job & funding opportunities; the latest papers in #GPLetters; #Goldschmidt2025 & other events.

More info: www.eag.org

DOM summer school - Please share!
Opportunity for early/mid PhD students.

Application form: doit.medfarm.uu.se/bin/kurt3/ku...
Applications will be open in the first instance until 31st January 2025. Venue for the summer school: www.gu.se/en/tjarno Please send questions to jeffrey.hawkes@kemi.uu.se

Collecting biofilms from the wetland

Collecting water samples from a river

I finally managed to move here!

Hi everyone, I am Jeff and I am broadly interested in mineral-organic matter-microbe interactions in terrestrial-aquatic interfaces. I am currently a research fellow at @gfz.bsky.social, studying #iron and #organiccarbon cycling in polar #wetlands.

Let's connect!