Just another site

O Fim


Looking down over the meeting of the Rio Solimões and Rio Negro from the boat

Memorable things happen when two rivers of very different provenance collide. The meeting of the Rio Solimões and Rio Negro is one of the most highly famed colliding points of the Amazon River network. The system is so large here that, at times, you are better off seeing some things happen from an airplane. Height is sometimes the only way you can appreciate how certain things work in this region: where water channels connect, or the quantity of forest that covers the drainage basin.

But, the meeting of the white and black water Solimões and Negro rivers, just downstream of Manaus, is one of the key events that you can experience a few feet from the river, i.e., on a boat right on top of it.

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Google map image of the black Rio Negro and white Rio Solimões meeting to form the Rio Amazonas. Note that the rivers do not fully mix for about 50 miles after meeting, at roughly the red marker. (Ignore the blue driving path.)

The most useful comparison that comes to mind in describing this ongoing and never-ending event is adding milk to coffee. But only in the immediate aftermath of adding milk, because as we all know, coffee and milk mix quickly and create a new, uniform color within seconds after the mixing event. Unlike what we drink, the Rio Solimões and Rio Negro do not mix that quickly; their physical disparities exceed the differences between coffee and milk. The white water river, cold and sediment-loaded, rushing down from the Andes, is much denser than the black water river, sediment poor, flowing in from the lower-lying, warm rain forest of the Guayana shield. Because of this density difference, the white Rio Solimões and black Rio Negro proceed downstream side by side, unmixed for about 50 miles (according to a rough Google map calculation, shown above) after their first meeting event.

Depending on which country you are in, the mixing of these tributaries marks the official start of the main Amazon River. Other mixing events on this river boat trip have yielded similarly fantastic outcomes. To extend the metaphor, the mixing of scientists and non-scientists our river boat has paved the way for unique learning opportunities and new intellectual results, as well. Just as it was rare for scientists to have the undivided attention of a public audience, it was similarly rare for the non-scientists to witness the procession of field work and scientific debate.


Meeting room of the Premium, where group discussions and presentations took place.

For graduate students on board, it was a rich opportunity to observe their mentors step outside of typical meeting rooms and laboratories, and present results in a way that expressed their own sentiments towards why this research was important. Equally insightful was the opportunity to hear the audience react, how their attention gravitated towards certain scientific details more than others. For a week, scientists had to tell stories. And for a week, the audience had to draw from their diverse backgrounds to respond, ask insightful questions, and provide useful feedback.

For what is probably my last trip to the Amazon region for graduate school, it was fitting to end with something that was both so reflective and forward-facing at the same time. Everyone stepped off of the Premium with slightly more practice in addressing key challenges in research: how one prioritizes earth science research when funding and time are not infinite, how objective and subjective this field of science should or can be. To get better at addressing these issues surely benefits everyone involved. What awaits further “downstream” of the mixing event that occurred aboard the Premium is perhaps a better platform for communication between science and the public.

8 December 2014: “Shaping” the river depth


First meeting before disembarking

Because it takes a long time to process samples from the field, I just got my first major data points from the river sediments we collected this past March and July. The data measure (1) what percentage of the sediment is and (2) the composition of carbon isotopes in each sample which I will represent by the symbol δ13C. These metrics are useful for making broad statements about where the river organic carbon comes from (e.g., algae vs. various plant types), how these vary with season, and what further analyses of greater specificity need to be done.

Once you start plotting the data in different graphs, you can see different shapes and forms of it emerge across the times and in locations of the river’s cross-section that we sampled. The most obvious shape so far is how the percent organic carbon and δ13C values of sediments between the river surface and depths closer to the river bed. The same shift by depth occurs in March and July.

We are not the first to see this, but it somewhat comforting to verify previous scientist’s observations that the Amazon River is more complicated than it looks. It means that you can’t just take one measurement at one time – one sample – and say that this data point scales with all the carbon moving through the river system towards the ocean. It means that the solid material which the river carries in the surface can be significantly different in composition from the material it carries at depth. What we see in the surface can come from different sources or parts of the drainage basin, and can also interact with the river environment differently on its way towards the Atlantic Ocean.

This is a typical complexity of all large, deep rivers. The volume of water in flux is so great that the denser (which tends to be heavier and larger) sedimentary material always ends up deeper in the river. Scientists have tried to fit all this mathematically into one equation, called the Rouse profile equation, named after the scientist who formulated it (Rouse 1950). The equation allows you to calculate the amount of sedimentary material (or a specific chemical measurement in it) at any depth of a river so long as you have one known measurement at one depth. The unique Rouse number, a constant in the equation, encompasses all change with depth expected to occur in that specific river.

Like all scientific models of the real world, the Rouse profile is a simplification. It does not always work. But it is more accurate and practical than assuming that large rivers are all the same with depth. And when it does, it means that one need not take measurements at all depths of a large river because you can calculate, or “model” them, instead (Bouchez et al. 2010).

Carl Johnson, our lab manager, emailed us the data just this past Friday. It’s perfect timing to have fresh data to discuss as we disembark on the boat today. Here’s our course for the coming week. I will reveal the sequence of these sites later on.

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1. Bouchez, J., Metivier, F., Lupker, M., Maurice, L., Perez, M., Gaillardet, J., & France‐Lanord, C. (2011). Prediction of depth‐integrated fluxes of suspended sediment in the Amazon River: Particle aggregation as a complicating factor.Hydrological Processes25(5), 778-794.

2. Rouse H. 1950. Engineering Hydraulics. Wiley: New York.

7 December 2014: Faces of the Amazon Dream

IMG_3682Harbor by Universidade Federal do Oeste do Pará – Santerem, July 2014

It is probably no coincidence that boats on the Tapajos River in Santarem are named Amazon Dream. Now on my fourth visit to Brazil in the past 13 months, I have come to realize that the concept of the Amazon dream is more than a sporadic phenomenon in my world. It would be an over-statement to compare it to formal anthropological patterns like the American Dream. Nonetheless, it pervades more facets of my life, and captivates more people, colleagues and friends in my community than I was aware of before it became part of my own graduate thesis.

Starting today, I will join thirty explorers in Manaus, the largest city of the Brazilian Amazon, to discuss what comprises the Amazon Dream and navigate through the confluence of two major Amazon tributaries, the Negro and Solimões Rivers. Our team largely consists of faculty from Woods Hole Oceanographic Institution, Woods Hole Research Center and collaborating institutions in Brazil and Siberia: from light-hearted and passionate students to researchers like Dr. Bernhard Peucker-Ehrenbrink, who was one of the early pioneers of the Global Rivers project at Woods Hole Oceanographic Institution, and Dr. José Mauro Sousa de Moura, who leads monthly river sampling efforts from Santarem. The group also includes people who support earth science from several other angles: affiliates of the Woods Hole organizations who have been drawn in different ways to the research there, and Chris Linder, who has mastered the skill of conveying the excitement of earth science through the still (and sometimes moving image).

Dream is such a non-scientific word because it sounds vague and theatrical, an over-dramatization of emotions over logic. With that said, knowing myself and my advisors in graduate school, who have made it their career to study the global significance of river systems on Earth, scientific dreams may be dramatic, but they are also very specific and testable. I have only just scraped the surface of understanding why the diverse group of scientists I am joining in Manaus could share a similar attraction to the Amazon River Basin.

Given the size of the drainage basin, there is a lot of room to dream here. Depending on how you count, over ten tributaries meet the eastward flowing Amazon River on its way to the Atlantic Ocean. They come from a wide expanse of South America: the Andes in the far West, the elevated Guyana and Brazilian shields to the North and South, and the tropical lowland forests that the hug the main stem right in the middle. By the time the Amazon River meets the Atlantic Ocean farther to the East, it has carried the unique imprints of each tributary. If you manage to look at the discharge with just the right lens (e.g., stable isotope chemistry, traces of lignin or sediment load), you can find the diverse natural and human histories that river water from distinct tributaries has absorbed during its journey towards the main stem.

Gaillardet et al. 1996

The geographical extent of the Amazon River tributaries (Gaillardet et al. 1996)

At the same time, there is nothing like a biodiversity hotspot and a massive organic carbon pool to prove that one need not travel far, or function at the large scale, to actually dream big in a place like this. The Amazon rainforest and river systems have a way of concentrating a lot in a small space. If you ever find yourself in primary rainforest, try to tally each distinct flora you can see, or pick apart every unique sound you hear coming from the tree canopy. Or, re-visit all the questions one can ask by visiting one site on the river, like Óbidos. These challenges are comparable to counting all the stars in the night sky; they can occupy people for their entire careers, or for their entire lifetime.


Rain forest in the Xingu River basin, one of the Amazon River’s most Eastern tributaries

In the coming days, as I traverse the largest river in the world among new company, it will be our shared learning experience and challenge to characterize what it means to dream about the Amazon River and, more broadly, other river systems in the world that compare and contrast with the Amazon in significant ways. Notably, this boat is not named Amazon Dream; perhaps that would be thematic overkill.


Gaillardet, J., Dupre, B., Allegre, C. J., & Négrel, P. (1997). Chemical and physical denudation in the Amazon River Basin. Chemical geology142(3), 141-173.

24 July 2014: Starting the dry season

When I searched Santarem, Brazil on a few days ago, I was shocked to see that the daily rain forecasted for the next 4 days is less than or equal 10%. How can a city at the heart of the world’s largest tropical rainforest receive such little daily precipitation? I know one should always take weather forecasts with a grain of salt, and quickly validated that I had typed in the right city when I saw that predicted humidity was >75%. But perhaps the precipitation forecast is not so far-fetched. I have arrived at the onset of Santarem’s dry season. 

And, perhaps contrary to intuition, now that we are here in Northern Brazil’s dry season, the waters of the Amazon River and its nearby tributary, the Tapajos, are still very high. The levels have just begun to fall as the rainy season transitioned to dry sometime during this past month, later than usual, according to Jose, our main collaborating scientist from Universidade Federal do Oeste do Para (UFOPA) – Santarem. But the transition in water level is more gradual than what one sees in the weather. Part of the disconnect between weather and river comes from the size of the Amazon floodplain, which occupies an area of 6.4 million km2, equivalent to almost 9 billion Manaus World Cup arenas. The main stem of the Amazon River receives not only the rain that falls directly on it, but also the cumulative precipitation over the entire Amazon floodplain. The time is takes for the Amazon River to realize the input of rainfall from directly above plus rain hitting the Andean headwaters plus rain navigating underground, beneath all 9 million soccer stadiums, creates the lag we see between season and river water level.



Views of the muddy Amazon River floodplain in flight between Santarem and Manaus.


The river is not the only body of water subject to seasonal cycles. Lining the Amazon River network are several floodplain or varzea lakes that are connected to river year round by small passageways. As detailed in an article published by Patricia Moreira-Turcq and her colleagues last year, these lakes feel the hydrological pulse of the Amazon River, as well. When river levels are falling, these lakes push water into the Amazon River. By contrast, when levels rise, which we also observed during our last trip in late March (during the rainy season), river water spills into these lakes, reversing the flow.

If we were to go back to questions about carbon, the motivation behind my frequent trips to this site with Woods Hole Research Center and UFOPA, seasonal patterns in the riverine carbon cycle reflect the ebb and flow of water between varzea lakes and the Amazon River main stem, as well. Using carbon isotope observations (see previous post “Clogging the Filters” for an example), Moreiera-Turcq et al. concluded that during falling river levels, most of the organic carbon flowing from lake to river originates from the bodies of algae growing in the lakes. In contrast, during rising river levels, most of the organic matter from rivers and flowing into the varzea lakes is mostly the degraded remains of soils and old vegetation washing in from land nearby. For a given lake, you can see this seasonal cycle in the lake’s bottom, plant and soil remains settle as sediments during the period of rising rivers. 

The seasonal interchange between river and lake fits into a longstanding idea that there are two types of organic carbon moving through river water, and each type participates in a distinct recycling process through the river. The carbon coming from algae in the lakes is newly produced, and very susceptible to breakdown by bacteria. For this reason, this carbon does not persist for long in river water; it quickly returns to its building blocks as carbon dioxide gas that bubbles out of the river and back into the atmosphere. At the same time, there is older organic carbon washing in from the adjacent floodplain, less likely to degrade. This source of carbon is believed to survive the river-borne journey to the Atlantic Ocean, where some fraction eventually gets buried in coastal sediments.

Many scientists continue to return to this two-piece carbon model of the Amazon River system, the question of whether the river is a “pipe or processor” (as summarized by Aufdenkampe et al. 2007) of organic carbon from the floodplain. Considering the size of this system, the answers to this question greatly impact how we understand the role of the Amazon River Basin in the global carbon budget. Some of the data we collect on our field trips will hopefully contribute to this understanding.



Aufdenkampe, A. K., et al. (2007). Organic Geochemistry38(3): 337-364.

Moreira-Turcq, P., et al. (2013). Global Biogeochemical Cycles 27: 119-130.

 Richey, J. E., et al. (2002). Nature416(6881): 617-620.

Slicing up the Amazon

Some things are less obvious about large rivers like the Amazon. In some ways, the water we observe at station Obidos, which is no more than 70 meters deep, is far more complicated than the spacious Southern Ocean, which reaches depths of 4000 meters on average.

Physical oceanographers who specialize in tracing the movement of water beneath the ocean surface will certainly disagree with that statement. Nonetheless, my reasoning stems from how marine chemists, particularly those who care about organic carbon, envision oceans and rivers to work beneath their surface. In general, it is enough for us chemists to assume that most solid particles in the Southern Ocean move vertically by the force of gravity, sinking downward from the surface, from their origins in masses of living algae. Hence, sampling the sinking particle from one location of the Southern Ocean provides a distinct, stand-alone measurement at that particular location of the ocean.

The fact that sediment movement in the Amazon River is water-driven, and therefore predominantly horizontal, changes the game completely. This difference means that estimating the sediment load at one point of the river’s path, such as at Obidos, does not necessarily represent the entire sediment flow across that location; one measurement may not suffice. If one were to cut a slice out of the river at that particular point and view it from its side, water speed and sediment load vary considerably across the entire slice. The result is that, while you might find one sediment concentration and flow rate at the very center top of this slice, i.e., right in the middle of the river, you will find different values 10 feet deeper, or 20 feet away.

We can be sure of this by using the Acoustic Doppler Current Profiler (ADCP). Though small and compact, this instrument can read the river slice by slice. Here, at station Obidos on the Amazon River, we have transited the channel from bank to bank multiple times with the ADCP. With roughly every second in transit, the ADCP measures the range of water speeds as they vary layer by layer, from surface to bottom, generating a vertical profile of current velocity. As it crosses the river, ADCP software glues each vertical profile side by side, creating a mosaic of current velocities at every depth and location of this transect, a slice of the Amazon River. A slightly different crossing would generate yet another slice.


This is how the ADCP looks once it is submerged right under water. It needs to stay here to take measurements.


And we need to stay close enough to read ADCP measurements in real-time.

The learning curve for operating the ADCP and reading the data it collects for us is steep, and I have not yet reached its peak. Nonetheless, I have accumulated enough information so far to understand how much current velocity can very in a given slice of the Amazon River. Though some things about river chemistry are obvious from the bird’s eye view, from the deck of Joao Felipe II, such as its sedimentary composure, it is not obvious that the movement of water along the surface could differ so much at depth. Thankfully, the ADCP extends our ability to perceive these differences.

Because our sediment analysis back in the lab will depend on our understanding of water velocity, data from the ADCP will be particularly useful in making the most accurate estimates from our chemistry. If we take only one measurement from one part of the station Obidos slice, for example, we will be able to understand how representative this one measurement is for the rest of that station.

Clogging the filters

One great advantage of field work in geochemistry is the ability to gain meaningful information from the environment by the simple act of being there. No analytical chemistry necessary. I remember how my advisor Phoebe showed me patches of silvery blue water along the darker back drop of the Southern Ocean surface water during our 2012 cruise on the R/V Revelle. These discolorations indicated dense populations of coccolithophores on ocean surface. Using the naked eye, we were able to hypothesize the chemical features of the water before us.

Several visual observations were similarly immediate and insightful on the Amazon main stem, as well. Upon arriving at the Óbidos site on our first full day, before even taking my first sample – long before actually analyzing it in lab back at home— it was clear that this water was packed with sediment, and by proportion, organic carbon. It was quickly apparent that the amount of carbon I collected per 100 liters at each Fazenda Tanguro stream I visited last November would not measure up to the quantity we could retrieve from filtering the same volume of sediment from the Amazon River waters.


Amazon River sediment clogged on a filter. Though it looks like milk-chocolate, I can assure you it certainly does not taste of it.

As a consequence, the orange murkiness of Amazon River discharge also gave away the unique logistical hurdles of sampling water here in April. On this first day at Obidos, we collected 100 liters of surface discharge near a center point of the river. Using pressure by manual bike pumps, we forced murky orange water through filters designed to collect all particles above 0.22 microns (1 thousandth of a millimeter!) in diameter. The filters clogged after just 1.5 liters. Because a large proportion of the work involved in sample processing during field work is manually exchanging clogged filters for new ones, the greatest challenge ahead was filtering the equivalent of 50 2-liter soda bottles before our trip’s end.

Fortunately, we have an efficient group of scientists on this river boat. João Felipe II is equipped with a diligent team of researchers from the Wood Hole Research Center and Universidade Federal do Oeste do Pará, quick learners of the act of water filtration. With just two bike pumps and three to five scientists, we are able to master a network of 4 filtration cylinders, passing a total of ~9 liters of water through filters at a time.


The filtration team. Even Kaka from Brazil’s 2010 National World Cup team lent a helping hand!

The great sediment concentrations in the river mean that we will go home with more than enough organic material to investigate its origin and transformation in the Amazon River system. We will be able to find specific biological molecules that have been produced by plants, riverine algae, and aquatic bacteria.

More importantly, we will have enough material from these samples to measure the relative proportions of two carbon isotopes in these specific molecules: carbon-12 and carbon-13. Isotopes are atoms of the same element that differ by the number of neutrons in their nucleus. Carbon-12 is the most common carbon isotope in nature; it has six protons and six neutrons inside its atomic nucleus (hence, 12 indicates the sum of protons and neutrons). By contrast, far less common is carbon-13, which is slightly heavier, as it has seven neutrons in its nucleus.

Living things incorporate different proportions of molecules with carbon-12 and carbon-13 when constructing or transforming organic matter. For example, during photosynthesis, plants use less energy in absorbing carbon dioxide with carbon-12 than carbon dioxide with carbon-13. Organic molecules produced by different plant types will demonstrate unique ratios of carbon-12 to carbon-13 based on these preferences.

Resolving the isotope ratios of specific biological molecules in our samples will help us track the history of organic carbon in the river, from its point of production to its journey into the river system and thereafter.

29 March 2014: Starting the rainy season

With the last trip to Brazil five months behind us, we arrive again for the next phase of sampling from the Amazon River Basin. For one week, I will visit one to two major sites on the main stem of the Amazon River with a team of scientists from Massachusetts-based Woods Hole Research Center and Brazil-based Universidade Federal do Oeste do Pará (UFOPA). These sites, Óbidos and Alter do Chão (a.k.a. the Caribbean of Brazil), sit a few degrees south of the equator, and wind through the northern states of Amazonas and Par, the quintessential Amazon rain forest, inside the “lungs” of our planet. Our visit coincides strategically with the start of the rainy season (and the end of Carnaval season), as daily rainstorms and river discharge are on the rise.



Typical river boats docked along the Rio Tapajós in Santarem, Pará, near its meeting with Rio Amazonas



At its core, the current mission is the same as my first trip in November. We return in search of sediments of organic carbon suspended in river discharge. Alongside the other scientists traveling from Woods Hole, we bring about two hundred pounds of equipment in our luggage. Once again, a disproportionately large fraction of this weight is comprised of bicycle-pump-powered devices for catching and filtering river water.

But, this time, we are sampling the main stem of the Amazon River, and by this fact alone, I expect this trip to differ dramatically. The suspended sediments I collected from Fazenda Tanguro in November flowed through small streams with limited catchment areas, through which underground water and rainfall drained into the river. This meant that the particles of organic carbon in my sediments have a unique terrestrial origin. If I collected sediments from a stream that flowed solely through soy cropland, for example, I could quickly surmise that most of the organic material in my samples came from soy agriculture.

Sediments suspended in the main stem of the Amazon River tell a broader story. There is a reason that station Óbidos has been visited by scientists of Amazonia for several decades. The flow rate of the river through this site varies by a factor of three, from ~100,000 m3/sec during the dry season (November – January) to ~300,000 m3/sec during the wet season (April – July) (Moreira-Turcq et al. 2013), the volume of 50 to 150 million soda bottles flowing through the river each second. Because water at station Óbidos has traveled extensively across the Amazon landscape, from the high Andes in Peru to the wide floodplains below, scientists have used measurements from Óbidos alone to learn about large-scale interactions between entire river network and the global carbon cycle.

Alter do Chão, which sits near the confluence of the Tapajos River tributary and the Amazon River, similarly draws water from an extensive catchment area. As a consequence, the organic carbon in suspended sediments from the Tapajós and Amazon River waters pools together a variety of sources from different landscapes. As we are interested in the role of different landscape types on the movement of carbon through the river system, isolating the origin of this organic matter is not trivial.

For this reason, the measurements that stem from this trip are ever the more valuable alongside the samples we collect from more isolated sites like Fazenda Tanguro. What comparisons can we draw between the large scale and the small scale within the Amazon River network? What is the pooled of effect of land use change spanning across all of Amazônia, one of the greatest terrestrial carbon sinks on Earth, on the movement of organic carbon from land to river to sea?

How-to Guide for Building a Lab


Early on, setting up for a week’s worth of work.

In the past week, I learned how to transform a chicken coop into a laboratory. The transformation had already started long before I arrived last week, but my short, quick stay at Fazenda Tanguro has still provided some important insights into the process.

 Most fundamentally, improvisation is key to drawing the blueprints. There is clearly a strong correlation between surprise and creativity here. The more unexpected turns I encountered, the more scientific innovation came out of improvisation.

I learned this with an early obstacle: blowing not only the fuse but moreover the capacitor of the power box for the peristaltic pump in incompatible Brazilian outlets. I planned to use this pump to suck water from a collection container and push it through filters on the other end, but now I had no more power to drive it, or collect half of my samples. For half of this half, I needed to pump water through a filter that removes particles from river water, allowing me to collect the throughput for other scientists at WHOI to measure nutrients and ions. For the other fourth, I needed to force water through cartridges that trapped lignin molecules dissolved in water, which are produced by vegetation and therefore help track the presence and influence of land plants in rivers.

But, maybe, the effect of arriving on a ranch over an hour removed from the nearest town and perhaps a half-day’s travel away from the nearest big city, makes you think in different ways. Certainly outside the box, as they say. As it turned out, replacing my pump was easy because the chicken coop lab had another. Most of the work entailed finding a car battery to power it, and fitting tubes of different sizes together pass water.

Other challenges, however, became clear with time. Most notable was the lack of a fume hood. Ventilation was ample in the lab, but no matter how much of a breeze passes through the open windows, hydrochloric acid is still hydrochloric acid, and extremely –literally – painful to smell. In the hottest of climates, I needed a small quantity of this caustic acid, which when added to my river water samples, helps extract the lignin molecules from the rest of the water feeding through the peristaltic pump.

So even in the tropics, it is useful to have some long sleeves and closed toe shoes, and gloves and goggles if you can manage it. Aside from these essentials, Paul – maybe the master lab architect here – also helped me fashion a trusty apron with a garbage bag, a fan to ventilate, a plastic sheet to serve as a hood-esque shield, and, finally, a bucket of water on standby as an emergency shower. This is how you build a fume hood in a chicken coop.


Later, wearing my lab gear after using the Hydrochloric Acid.

As I reflect, the odds seemed against collecting lignins for the Woods Hole Research Center. But, despite all the troubleshooting, I think I can return home with some vegetation to track from the streams at Fazenda Tanguro. 

Though I may not go back to the ranch for my thesis at WHOI, I am curious how the lab will continue to change into the future. What new innovations will occur? Will future generations of scientists soon forget that it once housed chickens? I will be particularly curious to learn whether anyone secured a system to keep insects, our great contaminants, away from field samples.


It probably took me five repetitions to engrain the word “multi-tirao” into my new vocabulary. And I’m not sure if you can even find it in a proper Brazilian Portuguese dictionary. Nonetheless, I will try my best to define it here because, in just three syllables, it adequately conveys the way field work gets done on Fazenda Tanguro, my field site over the past few days (fazenda means ranch). 

Oftentimes, dictionaries break down words into their different roots, so I will start with this same approach. First off, just like it would in English , “multi” means many. And indeed, at this fazenda, things exist and proceed in multitudes. I see multitude in the ten or so ripe mango trees that line our row of dormitories, kitchens and labs. I see multitude in the ostrich-like rheafamilies that roam the wide, flat fields of soy and corn. I certainly see multitude in the beetles swarming to my makeshift  laboratory when it is the only bright light on the grounds at night.


These are the rheas who run often through the crop fields in family-sized packs. I can’t remember their name in English. 

Following this track, there is multitude in how research gets done here, as well. While I seek to describe the chemistry of rivers draining through different land types (i.e., farm vs. pristine rain forest), the other scientists stationed here have several other questions to answer. Daniel and Paulo from Sao Paulo, observe how fish grow in similar parts of watershed. Rafael and Junha, also from Sao Paulo, are after the butterflies that live on the ranch, how they respond to forest fires. Paul and Marcia from the Woods Hole Research Center are investigating regional hydrology and soil water chemistry across different land types. Only a multitude of scientists can sufficiently tell the environmental story of Fazenda Tanguro, and perhaps contextualize this one ranch in the greater mosaic of landscape conversion in the Amazon River Basin.


 Taking a soil sample from a soy field.

The next part of my new word is more difficult to decipher: “tirao”. From my limited history speaking Portuguese, I have heard the verb “tirar” used in the context of taking photos or grabbing something. Assuming that the noun “tirao” is derived from the latter meaning, we do a lot of it on the fazenda, as well. All my field work is grabbing. I grab at least one hundred liters of stream water from each field site. I scoop soils from the land types surrounding each stream. The laboratory processing of these samples comes later, and certainly takes up the majority of my hours here. But, it all begins with the act of “tirao”.

Of course, compound words take on new meanings that surpass the sum of their parts. “Multi-tirao” as a whole also expresses a sentiment of teamwork and force. When the full-time Fazenda Tanguro crew helped me take 100 liters of water from a stream flowing through my one pristine rain forest site within a half hour, this was a multi-tirao. (In fact, this is when they taught me the word!) Not unlike my Indian Ocean expedition, field sampling is done best with many helping hands. A hundred liters is not an easy volume to carry, so the multi-tirao saved me a few more hours of energy that I could devote to post-collection processing in lab.

Just under 70 pounds

Image (Above: Before landing in Goiania, capital of the state of Goias in central Brazil).


Packing light is not the central philosophy of preparing for field work, and the baggage I am tied to for the next 10 days in central Brazil affirms this. One 68 pound suitcase, and a duffel bag that can fit an average-sized adult. Fortunately, the approximate weight limit of what I can carry on my own equally matches the weight limits for check-in.

In the past 24 hours, I have grown ever the more aware of the trust we put into the check-in agents at airport gates. Perhaps I should not take for granted that all the equipment essential to make a worthwhile field expedition in the Amazon River Basin can actually survive three flights from Boston to Brasilia to Goiania, a sprawling city that sits just beyond the intersection between dry cerrado forest and humid rain forest, at the center of the Brazilian Amazon.

My goal for the next few days is to collect hundred liters of river water from streams flowing through a giant ranch 12 hours away from Goiania by bus (stay tuned to see if my luggage survives that too!). And so it follows that most of my baggage contents are empty plastic containers, from bottles of various size to huge collapsible cubitainers, which can expand to hold almost 20 L of river water (or 5 gallons) at a time.

Although I might have over-packed my water sampling supplies, I do not actually plan to carry hundreds of liters of water back to the United States. If all goes well, I will leave with just the suspended particles of organic carbon and minerals, the soils and plant remains that have washed into the water from adjacent lands. When I analyze these solid materials back in lab, its chemistry will (hopefully) tell us something about which plant types produced this river-borne material in the first place, as well as the history of this organic material since being introduced to the soil and riverine environments. Because this organic material originally came from carbon dioxide in the atmosphere, many scientists are interested in keeping track of its movement from plant to river.

And hence the 68 pound suitcase is full of filtration units to separate the solids from this water. These units have been developed and refined through years of field work by scientists from my rivers research group from Woods Hole Oceanographic Institution and Research Center. A vertical cylinder, the filtration units accept water from the top and pushes it through a filter at the bottom that, very much like a coffee filter, collects only solid materials (or the coffee grinds) too large to pass through its small pores.

Image (above: A filtration unit when connected to a bike pump, during a practice run in Woods Hole with the more experienced river scientist Britta Voss)

With gravity alone, it would take much longer than my daylight hours to get all the water through the filter. So us river scientists are also typically equipped bike pumps, which I will use to pressurize the air inside the cylindrical filtration units, pushing the water downward past the filters faster than gravity would manage alone. Imagine being able to have your drip coffee ready in a few seconds rather than a few minutes. I hope that this bike pump accelerates my work over the next week by a comparable order of magnitude, as well.


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