Cleaning up water that bees like to drink
WASHINGTON, D.C. — Most people know that bees like nectar. But these insects also like to sip the water that plants push out of their leaves. If that water is full of pesticides, though, bees can ingest a dose of poison. Derek Woo, 17, wanted to see if he could clean out some of that bug-killing chemical. All he needed to add was a little charcoal.
The senior at Greenwich High School in Connecticut brought the results of his project here to the Regeneron Science Talent Search. Created by Society for Science & the Public, this yearly event brings together 40 top high school scientists from across the United States. It is sponsored by Regeneron, a company that designs new medications. The students present their projects to the public and compete for almost $2 million in prizes. (Society for Science & the Public also publishes Science News for Students and this blog.)
Derek didn’t start out with an interest in research. It developed accidentally, three years ago. That’s when he followed a friend into a meeting about his school’s research program. Teachers described how students would create their own projects and solve their own problems, he recalls. “It hooked me.”
When it was time to come up with his own project, Derek got inspired by a radio story. It described colony collapse disorder, or CCD. It’s what happens when most of the worker bees abandon a hive. Without the food these workers normally bring home, the queen and her young can starve.
Farmers also care about CCD because it threatens many of the crops that rely on bees to pollinate them. With no worker bees, the supply of peaches, blueberries, squash or other foods could run short.
Several factors can contribute to CCD, including parasites and infections. But Derek was especially worried about insecticides. Farmers use these chemicals on their crops to keep away hungry insects that could destroy their plants. But most of these chemicals will clobber harmful and helpful insects alike. Some can hurt or even kill bees.
Bees can get an extra-large dose of insecticides when they drink water that has been produced through a process called guttation (Guh-TAY-shun). At night, most plants close tiny holes in their leaves called stomata. That prevents too much water from leaving the plant. But pressure in the roots continues to push water up through the plant. Eventually, it can seep out of the edges of the leaves. If those leaves are shaped like blades, the drops may collect at the very tip.
That water isn’t pure, though. As it moves through the plant it can pick up nutrients such as sugar. And bees do love a sip of sugar. In fact, Derek observes, “They prefer [guttation water] over a pond.” The bad news: Insecticides and other chemicals can also end up in that water.
Derek wanted to see how much of an insecticide called imidacloprid (Ih-mid-ah-KLOH-prid) might end up in guttation water. To find out, he grew plants in his high school laboratory. The plants were Dracaena deremensis (Drah-SEE-nah Der-eh-MEN-sis), houseplants with long, blade-shaped leaves. He watered the soil of eight plants with clean water every other day for a week. He laced the drinking water of another eight plants with the pesticide. On the days he didn’t water the plants, Derek collected guttation water from the leaves’ tips.
He analyzed the water using a method called high-performance liquid chromatography. It separates chemicals from a mixture so they can be identified.
The insecticide didn’t just move into the leaves, the teen found. It actually became concentrated along its climb. Water at the leaf tips had four times more pesticide (per milliliter) than had the water sprayed onto the soil. Such a high dose, he notes, would kill any bees that sipped that water.
Hoping to reduce the amount of pesticide getting into the guttation water, Derek turned to biochar. This a type of charcoal that some farmers add to their soils. Biochar can help soils retain water. The same type of charcoal also can sop up certain toxic chemicals. So the teen investigated what it would do to imidacloprid. He grew a batch of plants in a mix of one part biochar to four parts soil.
The biochar indeed soaked up the pesticide. This kept most of it from reaching the leaves. The guttation water from plants grown with biochar in their soil had only 10 percent as much of the pesticide as before. But some chemical still remained in the water. Derek found about 5 molecules per one million molecules of water. This is not enough to kill a bee, the teen says, but it could be enough to make one sick.
Derek’s next goal is to convince farmers in his area to add biochar to their soils. “I’ve contacted a few farms in my area,” he says. But, he admits, it would be best for bees if farmers could stop using the pesticide. In 2013, the European Union banned imidacloprid’s use on plants to which bees are attracted. And starting this year, U.S. farmers will also be banned from spraying insecticides such as this one when bees are present.
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biochar A type of charcoal often used in agriculture to improve soil for plant growth. It can help plants take up nutrients, improve soil drainage and increase crop yields.
bug The slang term for an insect. Sometimes it’s even used to refer to a germ.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical can also be used as an adjective to describe properties of materials that are the result of various reactions between different compounds.
chromatography Separation and detection of chemical compounds as a result of their having traveled at different rates according to their different attractions to the matter that carries them (such as a flowing liquid or gas).
colony collapse disorder A phenomenon that occurs when most worker bees abandon a hive, leaving the queen and young bees alone. Scientists are unsure why colony collapse disorder occurs, but they think it may have something to do with parasites, diseases and pesticides, all of which can weaken the bees.
European Union The confederation of 28 European countries that have agreed to work peacefully together. Residents of EU can move freely between its member countries and sell goods to them. Most members have also adopted the same currency, known as the Euro.
evaporate To turn from liquid into vapor.
fruit A seed-containing reproductive organ in a plant.
guttation A process in which water moves up through plants at night, powered by higher water pressure in the plant’s root. Because stomata of the plant usually close at night, water can squeeze out at the edges and tips of leaves, gathering in droplets.
high school A designation for grades nine through 12 in the U.S. system of compulsory public education. High-school graduates may apply to colleges for further, advanced education.
imidacloprid A chemical used to kill insects. Applied to crops or soil, it attacks an insect’s nervous system. Primary targets include aphids and termites. It also can harm non-targeted insects, such as bees.
infect To spread a disease from one organism to another. This usually involves introducing some sort of disease-causing germ to an individual.
insect A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.
insecticide An insect killer. Some kill all kinds of insects; others are selective for specific types.
mass A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
molecule An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).
nectar A sugary fluid secreted by plants, especially by flowers. It encourages pollination by insects and other animals. It is collected by bees to make into honey.
nervous system The network of nerve cells and fibers that transmits signals between parts of the body.
nutrient A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.
parasite An organism that gets benefits from another species, called a host, but doesn’t provide that host any benefits. Classic examples of parasites include ticks, fleas and tapeworms.
pesticide A chemical or mix of compounds used to kill insects, rodents or other organisms harmful to cultivated plants, pet or livestock, or unwanted organisms that infest homes, offices, farm buildings and other protected structures.
pressure Force applied uniformly over a surface, measured as force per unit of area.
Science Talent Search An annual competition created and run by Society for Science & the Public. Begun in 1942, this event brings 40 research-oriented high school seniors to Washington, D.C. each year to showcase their research to the public and to compete for awards. Since spring 2016, this competition has been sponsored by Regeneron Pharmaceuticals.
Society for Science and the Public A nonprofit organization created in 1921 and based in Washington, D.C. Since its founding, the Society has been not only promoting public engagement in scientific research but also the public understanding of science. It created and continues to run three renowned science competitions: the Regeneron Science Talent Search (begun in 1942), the Intel International Science and Engineering Fair (initially launched in 1950) and Broadcom MASTERS (created in 2010). The Society also publishes award-winning journalism: in Science News (launched in 1922) and Science News for Students (created in 2003). Those magazines also host a series of blogs (including Eureka! Lab).
society An integrated group of people or animals that generally cooperate and support one another for the greater good of them all.
stoma (plural stomata) A tiny opening in the surface of a plant leaf or stem. It allows gases and water vapor to escape. Some plants may close their stomata at night. Other plants — those living in very dry areas such as deserts — close them during the day. In each case, the goal of those closures is to keep the plant from losing too much water.