geochemistry – Page 2

January 20, 2021January 20, 2021

To P, not to P? That is (an oversimplification of) the biogeochemical question—

Paper: Unraveling biogeochemical phosphorus dynamics in hyperarid Mars‐analogue soils using stable oxygen isotopes in phosphate

Authors: Jianxun Shen, Andrew C. Smith, Mark W. Claire, Aubrey L. Zerkle

Many geologists believe that ancient Mars, with its warmer temperatures and water-rich environment, may have been home to life. To test this hypothesis, astrobiologists must find signifiers of life that can survive the billions of years of hyperaridity experienced on the Martian surface. One such method could be identifying biotic alteration of the geochemical cycling of phosphorus, as was highly publicized during the recent discovery of phosphine in the atmosphere of Venus. Researchers have taken the first step in this search by characterizing biological phosphorus cycling in the analog environment of the Atacama Desert – an endeavor that has applied novel techniques in chemistry to provide insights about the movement of phosphorus in arid environments.

January 12, 2021January 13, 2021

Muddy waters lead to decreased oxygen in Chesapeake Bay

Featured Image: Plumes of muddy, sediment-laden water at the Chesapeake Bay Bridge near Annapolis, MD. Photo courtesy of Jane Thomas/ IAN, UMCES.

Paper: Seabed Resuspension in the Chesapeake Bay: Implications for Biogeochemical Cycling and Hypoxia
Authors: Julia Moriarty, Marjorie Friedrichs, Courtney Harris

A memorable feature of the Chesapeake Bay, the largest estuary in the USA, is that the water is very murky and looks like chocolate milk. Former Senator Bernie Fowler has conducted public “wade-ins” over the past 50 years in one of the Bay’s tributaries, seeing how deep the water is before he can no longer see his white tennis shoes, and let’s just say it is never very deep. This is because of the high concentrations of sediment, or small particles of sand and organic material, in the water. Besides making it harder for seagrasses to grow and serving as food for the economically-important oyster, sediment impacts the biological processes that determine how much oxygen and nutrients are available in the water for algae and fish.

November 25, 2020January 7, 2021

Unveiling the Mysterious Patterns of Arctic Cobalt

Featured Image: Fractured sea ice. Image courtesy Pink Floyd 88 a, accessed through Wikimedia Commons GNU Free Documentation License

Paper: Elevated sources of cobalt in the Arctic Ocean

Authors: Randelle Bundy, Alessandro Tagliabue, Nicholas Hawco, Peter Morton, Benjamin Twining, Mariko Hatta, Abigail Noble, Mattia Cape, Seth John, Jay Cullen, Mak Saito

Imagine navigating the Beaufort Sea to the North Pole, crossing icy and treacherous waters through the untamed North, all to chase a metal that is so rare that you have a better chance of finding 5 grains of sand in an Olympic swimming pool*. This is exactly what Bundy et al. accomplished in their work identifying cobalt amounts in the Arctic Ocean and how these amounts vary based on ocean depth, distance from land, and over a time period of 6 years.

November 11, 2020November 11, 2020

Ancient ocean temperatures outline a puzzling period in Earth’s climate history

Paper: The enigma of Oligocene climate and global surface temperature evolution

Featured image: Figure 1 from O’Brien et al. (2020). Paleogeographic reconstruction of the late Oligocene world, with continents and oceans in slightly different positions than today. Symbols indicate paleo-locations of ocean sediments that these scientists discuss in their paper, with stars indicating sites where they estimated Oligocene temperatures.

Authors: Charlotte L. O’Brien, Matthew Huber, Ellen Thomas, Mark Pagani, James R. Super, Leanne E. Elder, Pincelli M. Hull

We know that the amount of carbon dioxide in the atmosphere strongly affects climate –and temperature – on Earth. As carbon dioxide concentrations increase, so does average global temperature; this pattern is clear from direct historical measurements and ice core records going back hundreds of thousands of years. Nevertheless, it’s important to understand how this relationship operated in the past (for example, during times when there was less ice in the cold polar regions of the globe). A new study suggests that, millions of years in the past, the simple relationship between carbon dioxide and temperatures may not have been so clearcut.

October 10, 2020October 10, 2020

Rivers underground

Featured Image: The River Styx emerging from Mammoth Cave by Daniel Schwen. From Wikipedia under a CC-BY-SA license.

Paper: Modeling cave cross‐section evolution including sediment transport and paragenesis
Authors: M.P. Cooper and M.D. Covington

It’s not easy to watch caves form. It happens slowly and out of view, so we know relatively little about cave passage erosion compared to our knowledge of how rivers at Earth’s surface work. New research suggests that the same physical erosion processes that cut river channels at the surface might also be at work underground, adding new depth to our understanding of cave genesis.

September 8, 2020September 8, 2020

Did a change in phosphorus cycling lead to the diversification of macroscopic life?

Featured image: The earliest examples of life on Earth are microbial buildups known as stromatolites, like these 1.8 Ga old examples from Great Slave Lake, Canada. What changed on our planet for organisms to evolve from microbes to macroscopic lifeforms?

Paper: Ediacaran reorganization of the marine phosphorus cycle
Authors: Laakso, T.A., Sperling, E.A., Johnston, D.T., and Knoll, A.H.

This is a guest post by Akshay Mehra and Danielle Santiago Ramos. Contact us to submit a guest post of your own!

The history of life on Earth—as recorded in the rock record—stretches back to more than 3.5 billion years ago (Ga). The earliest fossilized remains of living organisms appear in the form of stromatolites, which are laminated constructions built in part (or completely) by microbes. While there have been some tantalizing hints that living organisms were mobile by 2.1 Ga (Albani et al., 2019) and multicellular by 1.6 Ga (Bengston et al. 2017), what is definitively known is that by ~750 million years ago (Ma), complex microscopic lifeforms were widespread on our planet. As time progressed, life became macroscopic. Then, during the Cambrian Era (beginning 539 Ma), most modern phyla (i.e. a grouping of organisms based on body plans) appeared in a flurry of diversification so drastic that it has been nicknamed “the Cambrian explosion.” Scientists are still trying to understand what combination of physical and biological processes may have driven the Cambrian explosion.

August 21, 2020September 22, 2020

Hillsides collapsing into Arctic streams can trigger CO₂ release to the atmosphere

Featured Image: Permafrost thaw slumps draining into a river on the Peel Plateau in western Canada. Photo courtesy Scott Zolkos, lead author of the paper.

Paper: Experimental Evidence That Permafrost Thaw History and Mineral Composition Shape Abiotic Carbon Cycling in Thermokarst-Affected Stream Networks

Authors: Zolkos, Scott & Suzanne E. Tank.

The rivers and streams of the Arctic transfer atmospheric heat into the surrounding permafrost (perennially frozen) soil. At the same time, surface soils up to 1 meter deep undergo annual freeze-thaw cycles. When warmer air arrives in the summer months, the combination of warming air and river water can thaw large chunks of ice-rich permafrost soil along the stream’s edge. Thawed permafrost breaks away from the surrounding hillsides and causes catastrophic slope failures, transporting huge amounts of sediment into the nearby waterways. As the stream water becomes murky it takes on the appearance of chocolate milk, and simultaneously, the geochemistry of the water changes.

August 16, 2020August 16, 2020

Citizen science project identifies extensive mining pollution in central Peru

Featured image: Anti mining protesters in Downtown Lima, Peru. Photo credit: Geraint Rowland on Flickr (CC BY-NC 2.0).

Paper: Citizen science campaign reveals widespread fallout of contaminated dust from mining activities in the central Peruvian Andes
Authors: James B. Molloy, Donald T. Rodbell, David P. Gillikin, and Kurt T. Hollocher

At the heart of Cerro de Pasco, Peru, one of the highest cities on Earth, is an enormous open pit mine. People have been mining at the Cerro de Pasco site since pre-Incan times, but after silver was discovered there in the 1630s, it became one of the world’s richest and most heavily worked mines.

July 28, 2020July 27, 2020

Evidence of pollution all the way to the poles

Featured Image: Lake Hazen in front of the Grant Land Mountains – photo courtesy Kyra St. Pierre, a co-author of the Sun et al. paper.

Paper: Glacial melt inputs of organophosphate ester flame retardants to the largest High Arctic lake

Authors: Sun, Yuxin, Amilia O. De Silva, Kyra A. St Pierre, Derek C. G. Muir, Christine Spencer, Igor Lehnherr, John J. MacInnis

Far from human habitation Lake Hazen sits north of the Arctic Circle surrounded by pristine, treeless mountains. But even there, the telltale chemical fingerprints of human pollution can be found.

Spring and summer in the far North are a short three-month period of reawakening, glacial melt, and permafrost thaw. During these months, meltwater transports anything that has collected on top of glaciers, like particles, nutrients, and contaminants deposited from the atmosphere, flowing down rivers and into glacial lakes.

July 23, 2020July 23, 2020

Cave formations show link between ice ages and the tilt of Earth’s axis

Paper: Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition

Featured image: Stalagmites captured by mareke on Pixabay

Authors: Petra Bajo, Russell N. Drysdale, Jon D. Woodhead, John C. Hellstrom, David Hodell, Patrizia Ferretti, Antje H.L. Voelker, Giovanni Zanchetta, Teresa Rodrigues, Eric Wolff, Jonathan Tyler, Silvia Frisia, Christoph Spötl, Anthony E. Fallick

Our planet has been circling and spinning in a wobbly dance around the Sun for billions of years. The exact motions of this dance- governed by Earth’s near-circular orbit (eccentricity), the tilt of its axis, and the orientation of the tilted axis in space (precession) fluctuate predictably. Variations in this planetary dance have changed the amount and distribution of sunlight reaching Earth’s surface through time, and have determined when the planet experienced long periods of cold temperatures and growth of massive ice caps on the continents (ice ages). However, scientists have not been so sure about which planetary motion is the most important for the timing of ice ages. New research uses climate information stored in caves to precisely link these motions to ice ages, showing that axis tilt may be the most important position in the dance when it comes to pulling Earth’s climate out of those frigid times.