Morgan, Jessica EnvironMentors Program April 6, 2012 How can lead level and the pH of soil affect a plant’s growth and your health? Why do some plants thrive where other plants don’t thrive? Well, what is in the soil or the type of fertilizer you use can determine how long it will take your plant to grow or whether it will grow or not. In the process of doing research, I found out that the pH of soil can decipher whether a plants will thrive or not. Also, the lead level in soil can affect a plant’s growth. You may be wondering whether lead is even in the soil. We all know of the dangers of lead in paint. Worn down paint that is chipping off usually on old buildings or houses can raise the lead level in the soils directly adjacent to the structure. This danger still resides today even if the old building is smashed. About six decades ago, constraints were primarily placed on lead in paint. Consequently, the lead content in paints has been minimized; however, paint companies are permitted to combine up to 0.05% lead in paints. Even though there has been major controversy on lead and constraints against the use of it, lead has not been entirely eliminated. In this brief but informative essay, you will learn how does the pH of soil affect a plant’s growth, the controversial history of lead, and why lead affects with a plant’s growth. For my experiment, I will be making my own pH paper which I believe is proven to give accurate results on the pH of soil.
Some people, including myself, didn’t know what pH testing was and didn’t know what it was used for? I was one of those people. Biologists and chemists have to know what pH testing is so they can test chemicals or grow a plant. pH testing is a procedure of evaluating the acidity or alkalinity of a solution. Theoretically, the test is an analysis of the concentration of hydrogen ions (H+), in comparison to the number of hydroxyl ions (OH-) per liter of solution. The first person to come up with the pH test was the Danish scientist Soren P.L. Sörenson. He discussed the inadequacy of measuring acidity by the total amount (normality) of acid additions to a particular solution. The added amount of acid would not necessarily be a true measure of its dissociation, depending on chemical interactions with other chemical species. Sörenson proposed that the actual degree of acidity should be rationally measured by hydrogen ion concentration and proposed the pH scale for expressing the hydrogen ion concentration. There are many benefits to my experiment. What are some benefits of pH testing? The first obvious advantage is that the pHs of the soil that your plant grows in can decipher whether or not your plant will sprout. Another benefit of pH testing is that is determines the amount of nutrients that the plant will receive. For example, if a sample of soil contains calcium and magnesium, the plant, more than likely, highly alkaline. If a sample of soil contains iron and manganese, the plant is highly acidic. Even though testing the pH of soil can determine whether a plant will thrive, the amount of lead in soil can be postponing the growth of plants and can also affect your health directly. When World War II began, small quantities of calcium arsenate were being used as pesticides. In
the course of the war, the price of lead (Pb) salts became very high. Since calcium arsenate was cheaper at the time, it took the place of lead arsenate for numerous uses, predominantly for the control of boll weevil in cotton and for forest pests. However, lead arsenate still lingered on as the favored insecticide for codling moth because of its countless effectiveness and lower phytotoxicity, a term used to describe the degree of toxicity in plants. In 1919, researchers began to find substitutes for lead initially when it was revealed that modern experiments for purifying produce were inadequate to effectively eradicate arsenic residues. Inopportunely, all of the experimented substitutes proved to deliver an ineffective pest control or were more lethal to plants and animals. Since then, researchers had given up hope. Years later in 1947, the manufactured carbon-based insecticide dichlorodiphenyltrichloroethane (DDT) was announced. The use of lead arsenate in Washington State immediately terminated when DDT was available nationwide. Around that time period, the foremost target pest, codling moth, had an advanced resistance to the lead arsenate compound. Fortunately at the time, DDT was found to be a much more effective control agent. Overall, the structure of plants causes it to not engross considerable amounts of lead and arsenic; therefore, plants translocate the lead and arsenic to edible plant tissues. High levels of lead in contaminated soils are not visibly phytotoxic. The absorption of lead in fruits grown on lead arsenic-contaminated soils is tremendously low. In distinction, the lead concentration in vegetal crops is surprisingly higher than fruits; in specific leafy and tuberous plants, it can surpass ethics linked with human health jeopardy. High lead elements in soil adhering to the
outside of these plants potentially explain some of the elevated lead content. Arsenic in lead arsenic-contaminated soils can be phytotoxic. Thermodynamic deliberations and firsthand proof suggest that lead arsenic is unbalanced in soil locations; over time, the lead will convert to less decipherable mineral forms. In conclusion, the lead and the pH of soil both play a determining factor on whether your plant will thrive or not. Even though research says that lead isn’t around anymore, I believe that these contaminants are still deep in the soil and are affecting plant growth in vegetables. As humans, we consume these vegetables that are grown and we could have low levels of lead poisoning and not know it now. As a young high school student and scholar, I want to keep the environment safe from contaminants that may harm the food supply that we receive for plants. That way, humans can live better, longer, and healthier.