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ENVIRONMENTAL CHEMISTRY Final Exam Review KEY CONCEPTS Chemicals essential to life Substrates and nutrients Air and water quality Organic and inorganic material Acids and bases Ingestion and absorption of materials Concentration and dispersal Evidence of toxicity Stability and biodegradability Uncertainties in environmental monitoring and in assessing toxicity and risk NUTRIENTS Nutrients are compounds or elements that are essential for production of the organic matter that makes up organisms. The four key nutrient categories are carbohydrates, proteins, lipids (fats) and minerals. NUTRIENTS Organic nutrients are carbon-based compounds such as carbohydrates, proteins, lipids, and vitamins, which are produced by green plants and modified by animals. Inorganic nutrients – the minerals – are divided into macrominerals and trace elements, depending on how much is needed for normal health. UPTAKE OF NUTRIENTS Consumers rely on the ingestion of other organisms in order to satisfy their energy and nutrient requirements. Ingestion: the process of taking in the nutrients needed for survival A substrate is a material on which an organism moves or lives. Some organisms attach themselves to the substrate, while others obtain their nutrients from their substrate. FERTILIZERS Artificial fertilizers greatly increase the amount and types of plant crops that can be grown for human consumption, but also require large amounts of fresh water. Agriculture influences the environment by effectively decreasing biodiversity. PESTICIDES The use of chemical poisons and toxins to control pests is widespread and although they are effective in reducing disease-causing organisms, they should be carefully controlled and regulated. herbicide: a chemical used to control weeds insecticide: a chemical used to control insects fungicide: a chemical used to control fungus ACIDS, BASES, AND THE PH SCALE The pH scale ranges from 0 to 14, and is used to compare substances based on their acidic and basic properties. Acidic substances taste sour, conduct electricity, and have a pH of less than 7. Basic substances taste bitter, feel slippery, conduct electricity, and have a pH greater than 7. Neutral substances have a pH of 7. PH INDICATORS pH indicators use color changes to help identify substances. Litmus paper turns red in the presence of an acid, and blue in the presence of a base. pH paper turns a different color for each pH value. Other common pH indicators include red cabbage juice, phenolphthalein, bromothymol blue, bromocresol green, and methyl red. EMISSIONS FROM INDUSTRY Fossil fuel combustion results in the emission of nitrogen, sulfur, and carbon oxides that react with moisture in the atmosphere to form acidic compounds. Acid precipitation results in the leaching of minerals from soils, and damage to living organisms. REDUCING EMISSIONS FROM INDUSTRY Acid-base neutralization reactions between minerals, such as limestone (calcium carbonate) and acidified waters in lakes and streams, can lead to more neutral pH water. Sulfur scrubbers and catalytic converters work to reduce the amount of nitrogen, sulfur, and carbon oxides that are released, in order to prevent acid precipitation from ever forming. TOXICITY Acute toxicity: the ability of a chemical to cause harm with only one exposure Chronic toxicity: the ability of a chemical to cause harm to an organism only after the chemical accumulates to a specific level after many exposures over time Since different organisms respond to toxic chemicals in different ways, toxicity is commonly measured by the LD50 – the dose needed to kill 50 percent of the population that it is applied to. POLLUTION The amount or dose of a pollutant that will cause harm is established by observing the effects of the pollutant on living organisms. Concentration is usually expressed in parts per million (ppm) or parts per billion (ppb) ENVIRONMENTAL MONITORING The monitoring of the levels of pollutants in any ecosystem requires knowledge of how to detect those pollutants or their effects, either by chemical testing or direct observation of biological organisms. Biological indicators are organisms whose presence or absence gives clues as to the amount of pollution affecting any ecosystem. Ex. The presence of macroinvertebrates in a stream DISPERSAL OF POLLUTANTS The dispersal of atmospheric pollutants is affected by global wind patterns. Pollutants may be carried great distances before their effects are felt. Pollutants can also travel through water systems. Soluble pollutants can travel large distances through bodies of water. Insoluble pollutants can contaminate a localized region for long periods of time. BIODEGRADATION Biodegradable wastes are those wastes that can be broken down by the action of living organisms. The rate of biodegradability is determined by the chemical structure of the waste material. persistent pollutant: wastes that accumulate in the environment and break down very slowly, if at all non-persistent pollutant: wastes that can be broken down into simple non-polluting compounds by naturally occurring chemical reactions or bacterial action EXPERIMENTAL VARIABLES Control – any element of an experiment that is unchanged or consistent throughout the trials Manipulated – the element of an experiment that is changed throughout the trials. This is what the experiment is testing for , and is related to the experimental question or purpose. Responding – the result of an experiment, based on observation. This should provide an answer to the experiment question. WHAT TO EXPECT ON THE PAT From this unit: 10 multiple choice questions 1 numerical response question 4 “knowledge” questions 7 “skills” questions EXAMPLES OF KNOWLEDGE QUESTIONS The presence of a species of large trout in a particular lake indicates a A. High dissolved oxygen concentration B. Low dissolved oxygen concentration C. High water temperature D. Low water pH Which of the following roles is played by carbohydrates in human nutrition? A. Act as an energy source B. Assist enzyme function C. Storage form of unused chemical energy D. Structural component of cells in the body EXAMPLES OF SKILLS QUESTIONS Bromothymol blue is an indicator that changes colour at different pH levels. Bromothymol blue will appear yellow when mixed with A. Lemon juice B. Baking soda C. Drain cleaner D. Distilled water The carcass of a whooping crane was found along the shore of a lake. It was examined, and high levels of pesticide were found in its tissues. Fish of various species were then collected from the lake, and they were found to have moderate levels of pesticide in their tissues. Which of the following statements best explains the high levels of pesticide in the whooping crane? A. The whooping crane’s skin absorbed the pesticide B. The whooping crane swam in contaminated lake water C. The whooping crane fed on pesticide-treated grass near the lake D. The whooping crane’s primary food source was the fish from the lake