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Lecture 13.pptx
- 2. Water Pollution and Plants Water can become polluted by a number of sources, ranging from sewage treatment plants and factories to mining activities, paved roads and agricultural runoff. Water pollution has a wide variety of effects on plant life and on the environment in general. Pollution in water not only harms plant growth but also allows plants to absorb dangerous chemicals from the water and pass them on to animals that rely on them for survival. Plants also pass on these pollutants to humans who consume them.
- 3. Foliage and Bark Damage Acid rain contains sulfuric and nitric acid, which can damage tree leaves and bark and damage the fine root hairs of many plants. Plants need these fine root hairs to absorb water. Acid rain is the result of the mixing of compounds, such as sulfur dioxide and nitrogen oxides with oxygen, water and other chemicals in the atmosphere. Many of the compounds that cause acid rain originate from power plants that burn fossil fuels, such as coal, as well as exhaust from buses, trucks and cars.
- 4. Photosynthesis Issues Water pollution from substances can disrupt photosynthesis in aquatic plants. Photosynthesis is the process in which plants use the energy from sunlight to produce sugar, or glucose, by converting carbon dioxide into carbohydrates. However, when water is polluted, the capacity of water to dissolve gases such as carbon dioxide is negatively affected. Because plants depend on photosynthesis for their survival, any interference in the photosynthetic process can kill them.
- 5. Soil Problems Human activities such as mining can release acidic drainage, which can have widespread effects. Acid drains can cause soil pollution which have negative effects on plants and flora as well as the organisms that depend upon them. Polluted water in the ground actually washes the essential nutrients, plants need out of the soil. Water pollution makes the soil acidic and negatively affects the solubility of nutrient ions, such as iron, magnesium, potassium and calcium ions. As a result, water removes these nutrients more quickly from the soil and causes their leaching into streams and lakes. Calcium and magnesium in particular are critical for proper plant growth. Magnesium helps plants to synthesize the pigment chlorophyll -- which is necessary for food formation -- while potassium helps plants in maintenance of turgor pressure. Without these nutrients, plants become more susceptible to drought, fungal and insect infections. Water pollution also releases large amounts of aluminium in the soil, which can be harmful to plants.
- 6. Micro-organisms Acidic soils created by deposit of acidic compounds such as sulfur dioxide produce acidic environment that is harmful for micro-organisms, which improve the soil structure by breaking down organic material and aiding in water flow. Photosynthesis Soils polluted by acid rain have an impact on plants by disrupting the soil chemistry and reducing plants' ability to take up nutrients and undergo photosynthesis. Aluminium While aluminium occurs naturally in the environment, soil pollution can mobilize inorganic forms, which are highly toxic to plants and can potentially leach into ground water, compounding their effects. pH Acidic deposition into the soil can hamper its ability to buffer changes in the soil pH, causing plants to die off due to inhospitable conditions.
- 7. Effects of organic matter deposition: Organic matter from dead and decaying materials of plants and animals is deposited directly from sewage discharges and washed along with rainwater into water bodies causing increase in decomposers/ microbes such as aerobic and anaerobic bacteria. Rapid decomposition of organic matter increase nutrient availability in water favouring the luxuriant growth of planktonic green and blue-green algal bloom. In addition many of the macrophytes like Salvinia, Azolla, Eicchhornia etc. grow rapidly causing reduced penetration of light into deeper layer of water body with gradual decline of the submerged flora . This condition results in reducing the dissolved Oxygen and increase in the biological oxygen demand (B.O.D). The B.O.D of unpolluted fresh water is usually below 1mg/L while that of organic matter polluted water is more than 400 mg/L.
- 8. Effects of detergent deposition: Detergents from domestic and industrial uses wash down into water bodies causing serious effects on plants. Detergents contain high phosphates which results in phosphate- enrichment of water. Excess phosphates enter the plants through roots or surface absorption causing retarded growth of plants, elongation of roots, carbon dioxide fixation, photosynthesis, cation uptake, pollen germination and growth of pollen tubes, destruction of chlorophylls and cell membranes and denaturation of proteins causing enzyme inhibition in various metabolic processes.
- 9. Effects of agricultural chemicals Chemicals from fertilizers, pesticides, insecticides, herbicides etc. applied to crops in excess are washed away with rainwater as runoff, then enter into soil and finally arrive at the water bodies. Ammonium from fertilizers is acidic in nature causing acidification of water. Similarly pesticides, herbicides and insecticides also cause change in pH of the water bodies. Most common effect of these substances is the reduction in photosynthetic rate. Some may uncouple oxidative phosphorylation or inhibit nitrate reductase enzyme. The uptake and bioaccumulation capacities of these substances are great in macrophytic plants due to their low solubility in water.
- 10. Effects of industrial wastes Effluents from industries contain various organic and inorganic waste products. Fly ash form thick floating cover over the water thereby reducing the penetration of light into deeper layers of water bodies. Fly ash increases the alkalinity of water and cause reduced uptake of essential bases leading to death of aquatic plants. Liquid organic effluents change the pH of water and the specific toxicity effects on the aquatic plants vary depending on their chemical composition. There may be synergistic, or antagonistic interactions between metals with respect to their effects on plants.
- 11. Effects of silt deposition: Deposition of silt in water bodies occurs as a result of erosion carrying silt laden water and due to flood. It increases the turbidity of water and reduces light penetration in deep water causing decline in abundance of submerged plants. Siltation inhibits the growth of aquatic plants. Abundance of phytoplankton is affected due to reduction in surface exchange of gases and nutrients. Plants that are tolerant to turbidity are abundant followed by those that are intermediate and the least tolerant species. Plants such as Polygonum, Sagittaria etc. are found to grow in dominance
- 12. Effects of oil spillage Oil pollution due to spillage of oil tankers and storage containers prevents oxygenation of water and depletes the oxygen content of the water body. Further, oil spills by reducing light transmission inhibiting the growth of planktons and photosynthesis in macrophytes.
- 13. Effects of thermal pollution The release of heated water into water bodies from the thermal power plants has an adverse effect on the aquatic life. It reduces the activity of aerobic decomposers due to oxygen depletion because of high temperature. With decreased organic matter decomposition, the availability of nutrients in the water bodies is jeopardised. Aquatic plants show reduced photosynthesis rate due to inhibition of enzyme activity with increased temperature. Primary productivity and diversity of aquatic plant species decline because of increased temperature of water bodies as a result of thermal pollution.
- 14. Effect of nutrient enrichment Nutrient enrichment in aquatic water bodies leads to eutrophication which is a process whereby water bodies receive excess inorganic nutrients, especially N and P, stimulating excessive growth of plants and algae. Eutrophication can happen naturally in the course of normal succession of some freshwater ecosystems. However, when the nutrient enrichment is due to the activities of humans, it is referred to as cultural eutrophication, where the rate of nutrient enrichment is greatly intensified. Plants must take in nutrients from the surrounding environment in order to grow. Nitrogen and phosphorous, in particular, encourage growth because they stimulate photosynthesis. This is why they are common ingredients in plant fertilizers. When agricultural runoff pollutes waterways with nitrogen and phosphorous rich fertilizers, the nutrient-enriched waters often paves way to algal bloom leading to eutrophication. That result is oxygen depletion and dying of fishes due to suffocation.
- 15. Phytotoxicity effects on plants When chemical pollutants build up in aquatic or terrestrial environments, plants can absorb these chemicals through their roots. Phytotoxicity occurs when toxic chemicals poison plants. The symptoms of phytotoxicity on plants include poor growth, dying seedlings and dead spots on leaves. For example, mercury poisoning which many people associate with fish, can also affect aquatic plants, as mercury compounds build up in plant roots and bodies result in bioaccumulation. As animals feed on polluted food the increasing levels of mercury is built up through food chain.