Posts tagged ‘Sensors’

Jun 30

Crowdsource Your Data Collection?

What can you do when you need data from all over the world in a short amount of time? Many scientists, including ones at JPL/NASA, are crowdsourcing their data collection.

Projects range from ground truthing NASA satellite data, to spotting migration patterns, to collecting microbes.

Darlene Cavalier, Professor of Practice at Arizona State University is the founder of SciStarter, a website where scientists make data collection requests to a community of volunteers who are interested in collecting and analyzing data for scientific research.

Who Collects the Data?

SciStarter was an outgrowth of Cavalier’s University of Pennsylvania graduate school project where she sought to connect people who didn’t have formal science degrees with scientists who needed their help. She says, “We know from various National Science Foundation reports that many people without science degrees are interested in participating in and learning about science. The challenge was that there was no easy way to find those opportunities.”

One project invites UK citizens to find and take pictures of orchids.

Cavalier started SciStarter, in part, to create a “one-stop shop” resource where people could easily search and find projects best suited to their locations and interests. She says, “We have over 1,600 projects and events. Projects range from ground truthing NASA satellite data, to spotting migration patterns, to collecting microbes.” One project, sponsored by the National History Museum in London, invites UK citizens to find and take pictures of orchids with their smartphones, so scientists can study the effect of climate change on UK flowering times.

How Are Volunteers Recruited?

Volunteers are recruited through SciStarter’s partnerships with the National Science Teachers Association, Discover Magazine, the United Nations, PBS and more. One of the most visible ways that volunteers are enlisted is through an organization Cavalier started called Science Cheerleader. The organization consists of 300 current and former NFL and NBA cheerleaders who are scientists and engineers. These role models visit youth sports groups, go to science festivals, and talk in schools. During their appearances they engage people of all ages in actual citizen science projects. Darlene says, “This is our way of casting a wide net and making new audiences aware of these opportunities.”

Science cheerleader consists of 300 current and former NFL and NBA cheerleaders who are now scientists and engineers.

What’s the Ultimate Goal?

Cavalier is determined to create pathways between citizen science and citizen science policy. She says, “The hope is after people engage in citizen science projects, they will want to participate in deliberations around related science policy. Or perhaps policy decision makers will want to be part of the discovery process by contributing or analyzing scientific data.” Darlene has partnered with Arizona State University and other organizers to form a very active network called Expert and Citizen Assessment of Science and Technology (ECAST). This group seeks to unite citizens, scientific experts, and government decision makers in discussions evaluating science policy. Cavaliers says, “The process allows us to discover ethical and societal issues that may not come up if there were only scientists and policy makers in a room. It’s a network which allows us to take these conversations out of Washington D.C. The conversations may originate and ultimately circle back there, but the actual public deliberations are held across the country, so we get a cross-section of input from different Americans.” ECAST has been contracted by NASA, NOAA, the Department of Energy, and others to explore specific policy questions that would benefit from the public’s input.

ECAST is a network which allows us to take science policy conversations out of Washington D.C.

Overcoming Obstacles

Cavalier says the SciStarter team constantly works to remove challenges and impediments to public participation. She explains, “We’ve found it can be difficult to articulate the geographic bounds of a project because when a researcher says, “this project can be done in a watershed,” it doesn’t mean anything to most people. So SciStarter spent time developing a system of “Open Streetmap and USGS databases that show land-type coverage.”

Another obstacle to some types of research is access to instrumentation. Darlene comments, “The NASA Soil Moisture Active Passive (SMAP) project really opened our eyes to how many obstacles can exist between the spectrum of recruiting, training, equipping, and fully engaging a participant.” This year, SciStarter is building a database of citizen science tools and instruments and will begin to create the digital infrastructure to map tools to people and projects through a “Build, Borrow, Buy” function on project pages.

Image of the world from a satellite view

“The NASA Soil Moisture Active Passive (SMAP) project really opened our eyes to how many obstacles can exist to full engagement.”

What’s Next?

Darlene says that sometimes scientists who want accurate data without knowing about or identifying a particular sensor for participants to use often create room for data errors. To address this problem, SciStarter and Arizona State University will be hosting a summit this fall where scientists, citizen scientists, and commercial developers of instrumentation will meet to determine if it’s possible to fill gaps to develop and scale access to inexpensive, modular instruments that could be used in different types of research. You can learn more about crowdsourcing your data collection with SciStarter here.

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Jun 24

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Lysimeters Determine If Human Waste Composting Can Be More Efficient (Part 2)

In Haiti, untreated human waste contaminating urban areas and water sources has led to widespread waterborne illness.

Hospital rooms in Haiti with patients infected with cholera

Waterborne disease is the leading cause of death for children under 5. Currently, Haiti is battling the largest cholera outbreak in recent history. Over 1/6 of the population is sickened to date.

Sustainable Organic Integrated Livelihoods (SOIL) has been working to turn human waste into a resource for nutrient management by turning solid waste into compost. (See part 1).

Water ways infected with waste and trash

Contaminants making their way into the waterways.

The organization plans on performing experiments with lysimeters, to determine if human waste will contaminate Haitian soil during the composting process.

A river infected with waste right below a huge forest

Even in places where there are toilets, they are often poorly designed or poorly placed. This latrine is located just above a river, where people are getting their bathing and drinking water.

Lysimeters Help Assess Health Hazards

SOIL will use G3 passive capillary lysimeters in an experiment to determine if composting human waste without a barrier between the waste and the soil will result in ecological and/or health hazards. Why? The problem is “jikaka,” or “poo juice.” The compost facility currently redistributes it onto the compost and finishing piles, but they would rather not have to manage it. They believe if they remove the concrete slab and allow composting to occur in contact with soil, the composting process will be easier and faster.

SOIL’s agricultural team conducts studies on the use of compost to improve farming practices and maximize economic benefits of targeted compost application.

The Experiment

The organization will test their idea as they expand their facility. New compost bins and staging areas for finishing have been built absent concrete pads. G3 passive capillary lysimeters have been installed, three beneath the compost bin, and four beneath the first staging area for finishing. They will be used to monitor the amount of moisture (jikaka) that travels through the soil as well as check for anything harmful that travels with it.

SOIL’s human waste compost was found to increase sorghum yields by 400%.

What’s the Future for Konpòs Lakay?

SOIL’s agricultural team studies the use of their compost (Konpòs Lakay) in order to optimize farming practices and the economic benefits of targeted compost application. The data they collect will help them expand the market for Konpòs Lakay, which in turn will support the sustainability of SOIL’s sanitation programs.

For more information on SOIL’s waste treatment efforts, visit their website, or watch the video below, a TEDx talk given by SOIL co-founder, Sasha Kramer.

Discover G3 Drain Gauge passive capillary lysimeters→

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Jun 17

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Lysimeters Determine If Human Waste Composting Can Be More Efficient

In Haiti, untreated human waste contaminating urban areas and water sources has led to widespread waterborne illnesses such as typhoid, cholera, and chronic diarrhea.

Human wastes are making their way into Haiti’s waterways.

Sustainable Organic Integrated Livelihoods (SOIL) has been working since 2006 to shift human waste as a threat to public health and source of pollution to being a resource for nutrient management by turning solid waste into compost. This effort has been critical to sustainable agriculture and reforestation efforts, as topsoil in Haiti has severely eroded over time, contributing to Haiti’s extreme poverty and malnutrition.

Border between Haiti and the Dominican Republic from an aerial view

This is a very famous image of the border between Haiti and the Dominican Republic. It’s often used to demonstrate how badly off Haiti is relative to their neighbors. What you’re actually seeing is the environmental scars of a very different post-colonial history.

Why Compost?

Topsoil erosion in Haiti was estimated to be 36.6 million metric tons annually in 1990, and it is estimated that only one sixth of the land currently cultivated in Haiti is suitable for agriculture. SOIL combats desertification by producing over 100,000 gallons of agricultural-grade compost made from human waste annually. SOIL research has shown that this compost can increase crop yields by up to 400%. The organization has sold over 60,000 gallons of this compost to local farmers and organizations, increasing soil organic matter and nutrients throughout the country.

Waste covers the urban area infecting people and causing problems

Today in Haiti, only 25% of people have access to a toilet – meaning people are forced to go to the bathroom outside or in urban areas, in a plastic bag, which often times gets disposed of in a canal or an empty lot.

How Do They Do It?

SOIL distributes specially constructed toilets throughout Haiti that separate urine from solid waste. Odors are reduced by covering the solid waste with organic cover material. The toilet utilizes a five gallon bucket to collect solid waste that can be swapped out when full.

Instead of flushing nutrients away with fresh water, people use a dry carbon material to cover it up so that it doesn’t smell, and it doesn’t attract flies. This material also provides food for the microbes that will ultimately transform the poop.

The five gallon buckets are collected weekly and taken to the composting facility, where they are dumped into large composting bins. It takes about 1500 buckets (3-4 days worth) to fill each bin. Bins are required to reach 122°F and left for 2.5 months in order to kill all pathogens.

Wastes are safely transformed into nutrient-rich compost in a carefully monitored composting treatment process that exceeds the World Heath Organization’s standards for the safe treatment of human waste.

The compost is then removed from the bin and turned by hand. There are three concrete slabs used to manage the finishing process. Compost is turned horizontally and then moved forward to the next slab, allowing multiple batches to be finishing at the same time, each at a different stage. After processing, the compost is sifted, bagged, and sold, reinvigorating the agriculturally-based Haitian economy.

Students study plants sold for agriculture

The compost SOIL produces is bagged under the Haitian Creole brand name “Konpòs Lakay” and then sold for agricultural application, improving both the fertility and water retention of soil. With over four billion people worldwide currently lacking access to waste treatment services, finding ways to provide waste treatment services profitability through the private sector has the potential to dramatically improve public health and agricultural outputs globally.

Continue reading part 2→

Understand the Impact

Watch this 5 minute video filmed by independent parties to see how SOIL is impacting Haitian citizens and the environment.

Read how experiments using lysimeters will help SOIL make the composting process more efficient.

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Jun 11

Founders of Environmental Biophysics: Champ Tanner

Champ Tanner (November 16, 1920 – September 22, 1990) Image: soils.wisc.edu

We interviewed Gaylon Campbell, Ph.D. about his association with one of the founders of environmental biophysics, Champ Tanner.

Who was Champ Tanner?

Champ Tanner was a dominant scientist in his time and a giant among his colleagues. He was the first soil scientist to be elected a member of the National Academy of Sciences: the highest honor a scientist can achieve in the United States. Some may not realize that throughout a career filled with achievements and awards, he battled the challenges of a debilitating illness. He didn’t let that limit his passion for science, however. His efforts to understand and improve measurements generally went beyond those of his fellow scientists. One of his colleagues once said of him, “Champ’s life exemplified goal-oriented determination and optimism regardless of physical or financial impediment.”

Dr. Tanner was one of the pioneers in applying micrometeorology to agriculture.

What were his scientific contributions?

Champ was an extremely careful experimentalist who was gifted at developing instrumentation. He started out making significant contributions in soil physics such as improved methods for measuring water retention, particle size distribution, air-filled porosity, and permeability. He was one of the pioneers in applying micrometeorology to agriculture and was passionate about finding ways to improve the precision and reliability of measurements. No measurement was too difficult. He designed and built his own precise weighing lysimeters which provided measurements of evapotranspiration in as little as 15 minutes. Later, he switched to plant physiology, reading almost every published paper on the subject and then building his own thermocouple psychrometer and plant pressure chambers, making important contributions in that field.

His largest contribution, however, was the measure of excellence he inspired in the students that he trained. I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have. They’ve all made enormous contributions in many different fields. Perhaps it was because he was a pretty hard taskmaster. He expected the students to meet a standard, and the ones that struggled with that had a hard time. In fact, to this day one former student complains, “About once a year, I have a nightmare in which Champ appears.”

I don’t know of anybody, anywhere in the world, that produced a crop of students that has attained the levels that his have.

Champ wanted his students to measure up, but he also cared about them. His fellow scientist, Wilford Gardner, described him this way, “There was a transcendent integrity to his personality that permeated everything he did. He could be blunt, candid and forthright, but he was never lacking in compassion and concern for students, colleagues, and friends.”

What was your association with him?

I had a wonderful relationship with Champ, although I wasn’t one of his students. One of his former students came to WSU as a visiting scientist and told him about what I was working on. As a result, he brought me into his inner circle of associates and played a vital role in the success of my research. This association even extended to my family who were with me on one of my many trips to Madison. Despite my numerous and occasionally unruly progeny, he and his wife welcomed us like long lost relatives and made each of the children feel special. That’s who they were: the most caring and outgoing people.

Champ also had a sense of humor. He used to call me up to have long discussions about science, and because he was two time zones ahead, it would get pretty late for him. We’d be having an intense discussion about experimentation, and all of a sudden he’d stop and say, “Oh, I’d better cut this off, or I’ll get home to a cold supper and a hot wife.”

What kind of a person was he?

If you worked in his lab, you needed to tow the mark. You didn’t leave tools around, and you didn’t mess them up. If you left out a screwdriver, you’d find it on your desk the next morning with a terse note. And if you took the diagonal pliers, cut some hard wire with it and left some nicks, those would be on your desk too. It was a sort of tough love, but he used it to train his students to the highest possible level.

He taught his students to be rigorous in their measurement protocols

He wanted his students to stand up and argue for their point. If you were the kind of person that could stand your ground and put up a good defense, he loved that. Gardner described Champ in this way, “His work hours were legendary. His standards of science and personal integrity were almost unrealistically high. The stories his students now pass on to their students may sound apocryphal to those who did not know Champ. But it was impossible to exaggerate where Champ was concerned.”

What do you think scientists today can learn from him?

What we can learn from Champ Tanner is not to fool ourselves. He thought you should try to come to an answer in a few different ways, to be sure that it really was the answer. He taught his students to be rigorous in their measurement protocols in order to get the noise out of their experiments. He wanted them to dig to the bottom of problems and understand the details. In his mind, you couldn’t be a scientist and rely on somebody else to figure out heat transfer or radiation. He thought you should understand it well enough that you could defend it yourself.

You can read more about Champ Tanner’s life and scientific contributions in this biographical sketch, written for the National Academy of Sciences when he died.

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May 27

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Are Biodegradable Mulches Actually Better for the Environment?

Henry Sintim, PhD student at Washington State University, is investigating whether biodegradable mulches are, in fact, what they claim to be.

Plant row farm with dirt between each row

Application of plastic mulches conserves water, and helps in weed, pest, and disease control.

He and his research team want to understand what leaches into the soil as the mulches degrade and which ones perform as well as polyethylene-made plastic mulches (PEs) at weed, pest, and disease control.

Plastic Mulch

Application of plastic mulches in agriculture is a common practice by specialty crop producers worldwide. It conserves water, and helps in weed, pest, and disease control, subsequently improving crop yield and quality. Because PE is durable and does not degrade in the soil, you cannot leave it in the field, which ultimately leads to the question of disposal. When PE is buried in the field, it becomes contaminated with soil and can’t be recycled but instead requires transport to a landfill, increasing production costs. Another problem arises when landfill facilities are not available. When this is the case, growers stockpile PE on their farm, where the rain can wash the mulch down to streams and water bodies. Henry Sintim and his team are investigating whether or not biodegradable plastic mulches (BDMs) could be a viable alternative.

Researchers digging a site up for installation

The team installs a lysimeter beneath the mulches.

Biodegradable Alternatives

Substituting PE with BDM could alleviate the need for disposal. However, Sintim says the potential impact on agricultural soil ecosystems needs to be assessed before adopting biodegradable mulch for field use. For instance, do biodegradable mulches really degrade? Sintim explains, “By BDM, we mean it is plastic mulch, but it has been made from pure or partial biobased materials. Though there are plastic mulches advertised as biodegradable, none have actually been proven to biodegrade, so the team is examining degradation of different commercial BDM types over time. They have also included an experimental BDM, in which the constituents were specified by the team.”

Sintim is monitoring the degradation of BDM by assessing the material properties and measuring the particle size and surface area via photography: digitizing and analyzing them using Image J software.

Researchers standing at an installation getting data

There are indications that some of the BDMs are performing well.

How Well Do the Mulches Compare?

Sintim also wants to find out how well BDMs maintain microclimate in comparison to PE. Since soil temperature and moisture content are important parameters that govern chemical reaction rates and microbial activity, and are likely to vary among the different BDM treatments, he is monitoring soil moisture dynamics using soil moisture and temperature sensors installed at 10 cm and 20 cm depths. In addition, the team has installed sensors directly underneath the mulches to measure surface temperature and light penetration. Reduction of light penetration is the attribute that helps plastic mulches to control weeds. The team is also assessing soil quality using the USDA Soil Quality Test Kit.

Sintim says so far one of the commercial BDMs and the experimental BDM had the same yield performance as PE. He adds, “We don’t have final results yet, and there are a lot of variables that could come into the picture. But I will say there is an indication that some of the BDMs are performing well.”

Next week: Find out how Sintim will determine what’s leaching into the soil and another alternative for polyethylene plastic mulch.

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May 23

Building a Martian: the University Rover Challenge

One day soon robots will rule the world. Well, maybe. For now, they rule Mars as research and colonization efforts push forward, and for a few days this June they will rule the Mars Desert Research Station in Hanksville, Utah at the University Rover Challenge (URC).

Launched in 2006, the URC has hosted competitions since 2007 and boasts contestants from around the globe, including the United States, Canada, India, Bangladesh, Poland, and Egypt. Each year, contestants are given point scores based on how quickly they complete a series of tasks and how closely each task conforms to parameters outlined by the competition guidelines. This year, teams must complete a terrain traverse, a simulated equipment servicing, an astronaut assist, and the retrieval and measurement of a non-contaminated soil sample.

Collaboration and Challenges

Byron Cragg, Science Team Lead for the Titan Rover Team out of California State University, Fullerton, says it’s been an uphill battle. “We’ve had to design the systems we are using to control our rover, retrieve our data, and keep our data organized from the ground up. We’ve also needed to make our rover robust in case a battery or a motor fails during the competition.”

It is no easy feat to build a rover for the Utah desert, let alone send instrumentation to Mars. This is why it has taken a multi-disciplinary team to build the physical components, robotic arm, telecommunications, and scientific cache on Titan Rover. Cragg says his team consists of scientists, computer engineers, electrical engineers, mechanical engineers, geologists, chemists, and biologists all working together.

A prototype image of the Titan Rover.

Titan Rover Features

The CSU rover is outfitted with sophisticated features like Leap Motion infrared sensors that allow Titan Rover’s robotic arm to be controlled by a human counterpart moving their arm in free space. When the user moves their arm and hand position, the arm on Titan Rover is given a signal from the command center to move accordingly.

Cragg is responsible for the 3D printed science cache that uses a 3” auger and a capacitance sensor to measure a soil sample’s volumetric water content, temperature, and bulk electrical conductivity. During the competition, the team will also be required to construct a stratigraphic column from HD images transmitted by the rover, as well as measure soil temperature at a depth of 10cm.

“It comes down to designing the pieces to communicate and work together to perform the tasks correctly,” Cragg says about the challenges ahead. “It’s one thing to build the rover,” he adds, “but it’s another to complete the requirements.”

While ambitions of a colonized Mars are on the horizon and research pushes on, like the Titan Rover project, progress will require collaboration and teamwork. In the meantime, good luck to all the Earthlings who will be competing in the Utah desert this June.

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May 14

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Is Average Relative Humidity A Meaningless Measurement? (Part II)

Scientists often misunderstand average relative humidity (see part I). In fact, it’s not uncommon to encounter average relative humidity being misused in scientific literature. This week, learn which measurement should be used instead.

Humid conditions in a pine forest.

What is Wrong with Average Relative Humidity?

We often use average values to illustrate the behavior of parameters over time. One of the most common is air temperature, where we effectively graph average half-hourly temperature across a day or daily temperature across a year to show important details about the environment. But, consider what average relative humidity would look like.

As noted above, a general rule, though not consistent everywhere, is that the temperature at night cools down to the point where the air is saturated and the relative humidity is 100% (1). During the day, depending on the climate and weather, the saturated vapor pressure may increase roughly two to five times ea and relative humidity would be between 0.2 to 0.5. If we calculated an average for the day, it would most likely be between 0.6 and 0.75, no matter what environment was being measured. Of course, if it were raining or in the winter with low incoming radiation, this would be higher. Still, it is easy to see that an average relative humidity does not do much to define meteorological conditions.

The title of this chart is misleading because they were not averaging across the day, but only daily at noon. Image: Britannica.com/

What Should We Use Instead?

The measurement that should be reported is vapor pressure. Not only is it independent of temperature, but it can also be effectively averaged over time to show ecosystem behavior. However, this value will not be helpful to scientists who are identifying the pull generated by the atmosphere for water vapor in the plant or soil. This quantity is called vapor deficit and is calculated by taking the difference between the saturation vapor pressure and ea.

We sense water deficit in the atmosphere through our skin.

As humans, we intuitively sense the deficit when we feel that the atmosphere is dry through drying of our lips or our skin. The same is true for plants. The dry atmosphere will exert a higher pull on the water, pulling it out through the leaves. The higher the difference between the vapor pressure and the saturation vapor pressure, the more pull for water. Although sometimes reported in literature, the most common use for vapor pressure is as a standard input to evapotranspiration models like FAO56 or Penman-Monteith.

See weather sensor performance data for the ATMOS 41 weather station.

Explore which weather station is right for you.

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Apr 29

Does Early Planting Increase Risk to Winter Canola?

Many dryland winter canola growers assume that if they plant earlier, they will establish a stronger plant, but Washington State University researcher Megan Reese recently found that this was not the case. She and her team discovered that planting earlier increases risk to the plant, as more water is used, and the reduced amount of water then left after the winter season limits spring regrowth. Megan’s findings could be valuable as water is the most yield-limiting factor in eastern Washington state’s wheat-dominated dryland systems, where winter canola has newly emerged as a rotational crop.

Bright yellow canola field in full bloom

Winter canola is cold hardy, but it’s not as resilient as wheat.

Early Planting:

Winter canola is cold hardy, but it’s not as resilient as wheat. It’s planted in August, much earlier than winter wheat, which is planted in the late fall. In order to survive, winter canola has to establish a hardy taproot system so that plants have reserves to survive the winter. Megan says, “Opinions vary, but anecdotally, a dinner plate sized plant can survive winter fairly well, so that’s why winter canola is planted in August . However, because establishment and germination can be an issue, we decided to try planting in June at Ritzville, Washington, thinking the soil would be more moist and have a cooler seedbed. However, the early planting date had a negative effect on winter survival. Not one of the early plants survived. We found the plants that started earlier used a lot more water, and consequently, the winter rains weren’t enough to refill the soil profile. Excessive growth and bolting also contributed to low survivorship.”

Methods and Moisture Release Curves:

Megan monitored soil water in the profile several different ways. At one location she used a neutron probe and hand-sampled gravimetric soil moisture in the top 30 cm of the profile, and in other locations, she was limited to hand samples. Then she combined those measurements with local weather stations to provide the crop water balance for the canola. Using these data, she was able to determine soil water use as indicated by the water content change through the growing season and calculate the depletion of soil water.

Anecdotally, a dinner plate sized plant can survive winter fairly well.

Megan also took soil samples into the lab from each depth increment at every site and used a chilled mirror hygrometer to construct a moisture release curve. This helped her to define the apparent permanent wilting point at -1.5 MPa. She says, “I was able to then see how efficient canola was at extracting available water, and I could look at available water instead of total water contents, which was more useful in terms of plant accessible moisture in the soil profile. It allowed me a consistent platform to compare actual water amounts across sites with differing soil types. At one site, 12.5% of the water was unavailable, but in the sandier soils at another site, it was 4%. So there were significant differences in permanent wilting point.”

Water and Physiological Challenges Affect Winter Survival:

Megan found that the June planted canola used every milliliter of available water in the soil profile by late October/early November, but August-planted canola still had some water above wilting left in the profile over the winter, which helped the plants in the spring. She says, “It was a milder winter, so we didn’t get the usual amount of snow and rain, which probably played a role, but we did not see the profile refilled in the June-planted canola. In addition, those June plants were purple and wilted by November, so water stress could have hurt the plants in terms of its defenses. However, I think a larger issue was that they grew so large (the crowns actually elongated and bolted so they weren’t close to the soil) they were more susceptible to the harsh temperatures, whereas the August planted canola were much smaller and their crowns stayed right on the soil surface.” These findings are based on only one year of data, and Megan notes that early plantings have worked well in the milder climate of Pendleton, OR.

What Does it Mean for Farmers?

Megan says, “We were able to surprise a lot of farmers by showing that canola roots access water down to 1.5 to 1.7 m in the fall; it was hard to believe that a winter crop would do that. Also, in my second year’s data, we followed water use all the way through harvest, so we were able to show how much yield we gained for every millimeter of water used, and farmers liked hearing that number as well. I think it’s useful information that incorporates biophysics principles and answers some questions that these new canola producers are interested in. I have three locations this season that we are currently following to give farmers a further idea of what the water use looks like, when canola uses that water, and from where in the soil profile. Hopefully, this research will help them manage their rotations and look at the possibility of adopting canola.”

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Apr 25

The Tensiometer: Micro-sized

A strand of a spider’s web is 5 micrometers in width. Microelectromechanical systems (MEMS) devices range in size from 20 micrometers to one millimeter. That’s the incredibly small size of the components used in the tensiometer being developed by PhD candidate, Michael Santiago, and his collaborators, professors Abraham Stroock and Alan Lakso at Cornell University.

Spider wed with dew water on the strands

MEMS devices can be as small in width as 4 strands of a spider’s web.

The engineer/research team is using MEMS technology to develop a miniature tensiometer (microtensiometer) that has a 100 times larger range than existing tensiometers, is stable for months, communicates digitally, and can be embedded into plant stems to directly measure plant water potential.

Existing Tensiometer Limitations:

Water potential is the best measure of a plant’s hydration relative to growth and product yield. Unfortunately, directly measuring water potential in plant tissue is only possible through labor-intensive, destructive methods such as the leaf pressure bomb and stem psychrometer. A common alternative is to use ‘set-and-forget’ soil tensiometers to measure soil water potential as a proxy for plant water potential, but this method is unreliable for plants with high hydraulic resistance (vines and woody species), where plant water potential is often much less than the water potential in soil. Although soil tensiometers are very accurate and simple to use, they can be large and bulky, and cavitate as soils dry.

A 25 cent coin next to a prototype microtensiometer

Prototype microtensiometer made with MEMS components.

Solution:

The Cornell University research team wants to improve the design of the tensiometer so it can be used in the field for applications such as continuously monitoring and controlling plant water potential in vineyards to consistently produce high-quality wine grapes with an exact flavor/aroma profile. Santiago says, “We’ve basically miniaturized a tensiometer using microchip technology to the point where it’s this tiny chip inside a wafer. Because of the way we fabricated it, we are hoping to make it an embeddable tensiometer that can go in anywhere and measure tension down to about -100 bars (-10 MPa).”

Developing and Calibrating

Santiago is using a chilled mirror hygrometer to produce solutions of specific water potential to test, calibrate, and characterize the microtensiometer. He comments, “We’ve been testing it in osmotic solutions. We use the water potential meter for calibrating a solution of PEG (polyethylene glycol), and then we measure it with the tensiometer.”

One hurdle the team has to overcome is finding a membrane that keeps small molecules and ions out of the tensiometer pores: these pollute the water inside the tensiometer and cause measurement errors. Santiago explains, “Our solution right now is to test in solutions of large molecules, such as PEG of 1400 molecular weight. The tensiometer pores are about 3-4 nanometers, extremely small, but small molecules, such as sugars and salts, can still get through. It’s not a problem for the short term because we are directly submerging into solutions of just water and large molecules, but our goal is to go into the environment and insert the tensiometer into soils and plant stems where small molecules are ubiquitous, so we’ll have to find a membrane that works and can handle field testing.”

The team has been experimenting with materials such as Gore-Tex and reverse osmosis membranes [M5] [M6] hoping to find a membrane that allows water through and keeps ions out, but does not slow the measurement.

Researchers want be able to insert the device directly into plant xylem.

What’s Next?

Santiago says the calibrations have worked well. Now the challenge will be putting the tensiometer into different environments such as soil, concrete, and plants. For example, they want be able to insert the device directly into plant xylem, which will require a seal so water is not exiting the system. And that’s not the only complication. Santiago explains, “We are getting ready to do some testing in soils. The challenge will be getting good data because soil can be really heterogeneous, and we have this sensor with a much larger range than the usual tensiometer. So what do we compare it with? That’s going to be a bit of a challenge.” Santiago says the next few months will be spent getting into some different materials and obtaining some initial publishable data.

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Apr 7

Green Roofs—Do They Work? (Part II)

Innovative soil scientist, John Buck, and his team have discovered that green roofs have more capacity than people imagined (see part I). Below are some of the challenges he sees for the future, and the type of measurements he suggests researchers take, as they continue to validate the effectiveness of these urban ecosystems.

Green and whited plant on a garden rooftop with orange rocks

A green roof is essentially a garden on a roof, but rather than growing plants in soil, installers use a synthetic substrate made of expanded shale, expanded clay, crushed brick, or other highly porous, lightweight material.

New Challenges for Green Roofs

Green roof results are promising, but they present a new challenge: making sure the plants have enough water. The crux of the challenge is that the lightweight, expanded shale/clay substrate material, the standard in green roof design, does a good job of soaking up the water, but has some peculiar properties that are unlike typical soils. Specifically, the expanded shale and expanded clay media tend to be dominated by sand and fine gravel-sized particles that provide a high proportion of macropores, but the interior porosity of the large particles is dominated with micropores. That pore size distribution leads researchers to two important questions— How much water will be readily available for plant growth? And, will the unsaturated hydraulic conductivity be adequate to avoid starving the roots under high-evaporative demand by allowing water to flow to roots from the bulk soil? These are critical questions as green roof technologies continue to evolve.

Researchers wonder, will the unsaturated hydraulic conductivity be adequate to avoid starving the roots under high-evaporative demand.

Measurements Required for Green Roof Validation

Still, Buck has learned a great deal from his work. Considering the wild spatial distribution of summer storms, quantitative green roof performance studies require that rainfall be measured locally. Monitoring of soil volumetric moisture content measurements in concert with rainfall and soil lysimeter measurements of drainage, reveal the degree of total and capillary saturation, drainage rate, and porosity available for storage. Soil water potential sensors, placed within the capillary fringe of water ponded over subsurface drainage layers, can provide useful insights regarding the dryness of the drainage layer and overlying soil, as well as the available storage of stormwater within the drainage layer.

Direct measurement of soil drainage using lysimeters is a key supplemental measurement on green roof performance quantification projects because there is an unmeasured component of water storage where drought-resistant alpine succulents (typically Sedum species) are used on green roofs. The Sedum plants can absorb up to 10 mm of rainfall equivalent in their plant tissues.

Plants poking out of the soil in front of a house

Measurement of soil drainage using lysimeters is a key supplemental measurement on green roof performance quantification projects.

Other Projects and Future Plans

At ground level, Buck is quantifying the performance of intensive stormwater infiltration areas known as rain gardens, bioretention areas, or more generically, infiltration-based stormwater best management practices (Infiltration-based BMPs). When monitoring infiltration-based stormwater BMPs, Buck has used similar tools to those used on green roofs, but has added water-level sensors and piezometers. Buck has found that ancillary measurements of electrical conductivity, often available on water content sensors, along with surface and pore water sampling, can be used to document transformations taking place in infiltration systems. These measurements now combine to show that green roofs and infiltration-based BMPs are indeed making a difference to urban environments and contributions to CSOs. The challenge now is how to implement this technology more widely. But, with the validation now in hand, that job should be quite a bit easier.

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Measuring and Modeling the Environment

Posts tagged ‘Sensors’

Who Collects the Data?

How Are Volunteers Recruited?

What’s the Ultimate Goal?

Overcoming Obstacles

What’s Next?

Lysimeters Help Assess Health Hazards

The Experiment

What’s the Future for Konpòs Lakay?

Why Compost?

How Do They Do It?

Understand the Impact

Who was Champ Tanner?

What were his scientific contributions?

What was your association with him?

What kind of a person was he?

What do you think scientists today can learn from him?

Plastic Mulch

Biodegradable Alternatives

How Well Do the Mulches Compare?

Collaboration and Challenges

Titan Rover Features

What is Wrong with Average Relative Humidity?

What Should We Use Instead?

Early Planting:

Methods and Moisture Release Curves:

Water and Physiological Challenges Affect Winter Survival:

What Does it Mean for Farmers?

Existing Tensiometer Limitations:

Solution:

Developing and Calibrating

What’s Next?

Take our Soil Moisture Master Class

New Challenges for Green Roofs

Measurements Required for Green Roof Validation

Other Projects and Future Plans