Unit II:Environmental Chemistry(5hrs)
Credit for image : https://cdnintech.com/
By : Manoj Acharya
M.B.M.A.N Urlabari
F.b : ac.manoj2 (Manoj Acharya)
Air Pollution:
Causes:
- Industrial Emissions: Factories and power plants release pollutants like sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter into the atmosphere.
- Vehicle Emissions: Cars, trucks, and other vehicles emit pollutants like carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), and particulate matter (PM).
- Burning of Fossil Fuels: Combustion of coal, oil, and natural gas for energy production and heating releases pollutants like sulfur dioxide (SO2) and nitrogen oxides (NOx).
- Agricultural Activities: Livestock farming and crop burning release ammonia (NH3) and methane (CH4) into the air.
- Deforestation: Cutting down trees reduces the natural filtration of pollutants from the air.
Effects:
- Respiratory Problems: Air pollution can cause or exacerbate respiratory diseases like asthma and bronchitis.
- Cardiovascular Diseases: Pollutants like particulate matter (PM) are linked to heart attacks and strokes.
- Global Warming: Greenhouse gases released into the atmosphere contribute to climate change.
- Acid Rain: Sulfur dioxide (SO2) and nitrogen oxides (NOx) react with water vapor in the atmosphere, forming acids that fall back to Earth as acid rain, harming aquatic ecosystems and corroding buildings.
- Ozone Depletion: Certain air pollutants can deplete the ozone layer, leading to increased UV radiation exposure and risks of skin cancer.
Control Measures:
- Regulations and Standards: Governments can implement emission standards for industries and vehicles to limit pollutant emissions.
- Alternative Energy Sources: Promoting renewable energy sources like solar and wind power reduces reliance on fossil fuels.
- Improved Transportation: Encouraging public transportation, biking, and walking reduces vehicle emissions.
- Technological Solutions: Developing cleaner technologies like catalytic converters for vehicles and scrubbers for industrial emissions helps reduce pollution.
- Afforestation and Reforestation: Planting trees helps absorb pollutants and improve air quality.
Water Pollution:
Causes:
- Industrial Discharges: Factories release chemicals and heavy metals into water bodies.
- Agricultural Runoff: Pesticides, fertilizers, and animal waste from farms can contaminate water sources.
- Urban Runoff: Stormwater runoff from cities carries pollutants like oil, trash, and chemicals into water bodies.
- Sewage Discharges: Untreated or poorly treated sewage from homes and industries pollutes waterways.
- Marine Dumping: Dumping of waste, including plastics, into oceans and seas leads to marine pollution.
Effects:
- Waterborne Diseases: Contaminated water can spread diseases like cholera, typhoid, and dysentery.
- Harm to Aquatic Life: Pollutants in water can harm fish, amphibians, and other aquatic organisms, disrupting ecosystems.
- Eutrophication: Excessive nutrients from fertilizers lead to algal blooms, which deplete oxygen levels in water bodies, causing fish kills.
- Bioaccumulation: Toxins like mercury can accumulate in the tissues of organisms, posing risks to human health through the food chain.
- Habitat Destruction: Water pollution can degrade habitats like wetlands and coral reefs, threatening biodiversity.
Control Measures:
- Wastewater Treatment: Implementing effective sewage treatment plants helps remove pollutants before discharging wastewater into water bodies.
- Regulations and Enforcement: Enforcing laws to limit industrial discharges and agricultural runoff helps prevent water pollution.
- Public Awareness: Educating the public about the importance of proper waste disposal and water conservation encourages responsible behavior.
- Green Infrastructure: Installing permeable pavements, green roofs, and rain gardens helps reduce urban runoff and filter pollutants.
- International Cooperation: Addressing transboundary water pollution requires collaboration between countries to implement effective management strategies.
Soil Pollution:
Causes:
- Industrial Activities: Contamination from heavy metals, chemicals, and hazardous waste from industries.
- Agricultural Practices: Use of pesticides, fertilizers, and animal waste leads to soil contamination.
- Mining Activities: Extraction of minerals and metals can release toxic substances into the soil.
- Improper Waste Disposal: Dumping of solid waste and landfill leachate can contaminate soil.
- Urbanization: Construction activities and urban runoff introduce pollutants into the soil.
Effects:
- Reduced Soil Fertility: Soil pollution can degrade soil quality, affecting crop productivity and agricultural yield.
- Contaminated Food Supply: Plants grown in polluted soil can absorb toxins, posing risks to human health through the food chain.
- Groundwater Contamination: Pollutants leaching from soil can contaminate groundwater, a vital source of drinking water.
- Habitat Degradation: Soil pollution can harm soil-dwelling organisms and disrupt ecosystems.
- Land Degradation: Contaminated soil may become unfit for agricultural or recreational use, leading to land degradation and loss of biodiversity.
Control Measures:
2. Land-Use Planning: Proper zoning and land management practices can prevent soil pollution from urbanization and industrial activities.
3. Waste Management: Implementing proper waste disposal methods and recycling reduces the risk of soil contamination from landfill leachate and hazardous waste.
4. Soil Conservation: Practices such as crop rotation, cover cropping, and terracing help maintain soil fertility and prevent erosion, reducing the risk of soil pollution.
5. Monitoring and Regulation: Regular monitoring of soil quality and enforcement of environmental regulations help prevent and control soil pollution.
Water quality analysis :
Water quality analysis involves assessing the physical, chemical, and biological characteristics of water to determine its suitability for various uses such as drinking, irrigation, recreation, and aquatic habitat support.
1. Sampling: Water samples are collected from different sources such as rivers, lakes, groundwater wells, and wastewater treatment plants. Sampling locations and frequency are determined based on regulatory requirements, monitoring objectives, and potential sources of contamination.
2. Physical Parameters: Physical characteristics such as temperature, turbidity (clarity), color, and odor are measured on-site using portable meters or in the laboratory. These parameters provide insights into water clarity, aesthetics, and temperature-dependent processes.
3. Chemical Parameters: Various chemical constituents in water, including nutrients (nitrogen, phosphorus), heavy metals (lead, mercury), organic compounds (pesticides, pharmaceuticals), and pH, are analyzed using laboratory techniques such as spectrophotometry, chromatography, and titration. Chemical analysis helps assess water quality, identify pollutants, and evaluate compliance with water quality standards.
4. Biological Parameters: Biological indicators such as bacteria (E. coli, fecal coliforms), algae, and macroinvertebrates are used to assess water quality and ecological health. These organisms respond to changes in water quality, pollution levels, and habitat conditions, providing valuable information on ecosystem health and potential human health risks.
5. Data Interpretation: Analytical results are interpreted based on established water quality standards, guidelines, and objectives set by regulatory agencies. Deviations from these standards indicate potential water quality problems and the need for corrective actions such as pollution control measures, water treatment, or habitat restoration.
6. Reporting: Water quality data and analysis findings are compiled into reports that communicate monitoring results, trends, and recommendations to stakeholders, policymakers, and the public. These reports inform decision-making, policy development, and management strategies aimed at protecting and improving water quality.
Overall, water quality analysis plays a crucial role in safeguarding public health, preserving ecosystems, and ensuring sustainable water resources management. By monitoring and assessing water quality parameters, stakeholders can identify potential risks, prioritize interventions, and implement measures to maintain or enhance water quality for current and future generations.
Alkalinity is a measure of the water's capacity to neutralize acids, thus maintaining a relatively stable pH level. It is an important parameter in water quality analysis and is influenced by the presence of certain ions, primarily bicarbonate (HCO3-), carbonate (CO3^2-), and hydroxide (OH-) ions.
Factors Affecting Alkalinity:
1. Carbonate Minerals: Rocks such as limestone, dolomite, and marble contain carbonate minerals, which can dissolve in water and contribute to alkalinity.
2. Bicarbonate Ions:Carbon dioxide (CO2) from the atmosphere or organic matter can dissolve in water, forming carbonic acid (H2CO3), which then dissociates into bicarbonate ions (HCO3-) and hydrogen ions (H+), increasing alkalinity.
3. Hydroxide Ions: The presence of hydroxide ions (OH-) from sources such as mineral weathering or alkaline substances like caustic soda (NaOH) can contribute to alkalinity.
4. Acid-Base Reactions: Alkalinity can be influenced by acid-base reactions, where acids are neutralized by bases, increasing the concentration of alkaline species in the water.
Measurement of Alkalinity:
Alkalinity is typically measured through titration, where a strong acid (usually sulfuric acid or hydrochloric acid) is slowly added to a water sample until the pH reaches a certain endpoint. The endpoint is determined by a pH indicator that changes color at a specific pH value, indicating the completion of the neutralization reaction. The amount of acid required to reach the endpoint is proportional to the alkalinity of the water sample.
Importance of Alkalinity:
1. Buffering Capacity: Alkalinity acts as a buffer, helping to stabilize pH levels in water bodies by neutralizing acids that may be introduced through pollution or natural processes. This buffering capacity is crucial for maintaining suitable conditions for aquatic life and chemical processes.
2. Corrosion Control: In water treatment and distribution systems, alkalinity helps prevent corrosion of pipes and infrastructure by neutralizing acidic components and maintaining the water's pH within acceptable ranges.
3. Aquatic Habitats: Alkalinity influences the chemical composition of aquatic environments, affecting the availability of nutrients, the solubility of minerals, and the physiology of aquatic organisms. Fluctuations in alkalinity can impact the health and biodiversity of aquatic habitats.
4. Industrial Processes: Alkalinity is important in various industrial processes, such as manufacturing, mining, and agriculture, where control of pH and chemical reactions is essential for production efficiency and environmental compliance.
Control and Management:
1. Monitoring: Regular monitoring of alkalinity levels in water bodies helps assess water quality, detect changes over time, and identify potential sources of pollution or stress.
2. Buffering Agents: Adding alkaline substances such as lime (calcium hydroxide) or sodium bicarbonate can increase alkalinity in water systems, providing additional buffering capacity and stabilizing pH levels.
3. Pollution Prevention: Minimizing inputs of acidic pollutants such as acid rain, industrial effluents, and agricultural runoff helps maintain natural alkalinity levels and protect aquatic ecosystems.
4. Water Treatment: In water treatment processes, adjusting alkalinity levels may be necessary to optimize coagulation, flocculation, and disinfection processes, ensuring the production of safe and stable drinking water.
In summary, alkalinity plays a critical role in regulating pH levels, buffering acidity, and supporting aquatic life in natural and engineered water systems. Understanding the factors influencing alkalinity and implementing appropriate management strategies are essential for maintaining water quality and ecosystem health.
Free chlorine
Free chlorine refers to the form of chlorine that is available for disinfection in water treatment processes. It exists in water as hypochlorous acid (HOCl) and hypochlorite ion (OCl^-), collectively referred to as "free available chlorine" (FAC). Free chlorine is highly effective at killing pathogens such as bacteria, viruses, and protozoa, making it a crucial component of water treatment for ensuring public health and safety.
Forms of Chlorine in Water:
1. Free Chlorine: Free chlorine exists in water as HOCl and OCl^-, which are the active forms responsible for disinfection. The relative proportions of HOCl and OCl^- depend on the pH and temperature of the water.
2. Combined Chlorine: Combined chlorine refers to chloramines, which are formed when free chlorine reacts with ammonia or organic nitrogen compounds in water. Chloramines are less effective disinfectants than free chlorine and can produce undesirable tastes and odors.
Sources of Free Chlorine:
1. Chlorine Gas (Cl2): Chlorine gas is commonly used for disinfection in water treatment plants. It is introduced into water through a gas injection system, where it reacts with water to form hypochlorous acid and hypochlorite ion.
2. Sodium Hypochlorite (NaOCl): Sodium hypochlorite, commonly known as bleach, is a liquid chlorine compound used for disinfection in water treatment and sanitation. It dissociates in water to release hypochlorite ions, providing a source of free chlorine.
3. Calcium Hypochlorite (Ca(ClO)2): Calcium hypochlorite is a solid chlorine compound used for disinfection in swimming pools, drinking water treatment, and wastewater treatment. It dissolves in water to release hypochlorite ions, generating free chlorine.
Importance of Free Chlorine:
1. Disinfection: Free chlorine effectively kills pathogenic microorganisms, including bacteria, viruses, and protozoa, preventing the spread of waterborne diseases and ensuring the safety of drinking water and recreational water facilities.
2. Oxidation: Free chlorine acts as an oxidizing agent, breaking down organic matter, ammonia, and other contaminants in water. It helps reduce odors, colors, and tastes caused by organic compounds and maintains water quality standards.
3. Residual Protection: Maintaining a residual concentration of free chlorine in distribution systems provides ongoing disinfection and protection against microbial regrowth, biofilm formation, and contamination during water storage and distribution.
Measurement of Free Chlorine:
Free chlorine concentration in water is typically measured using chemical tests or online analyzers. Common methods for measuring free chlorine include:
1. DPD Colorimetric Method: This method involves adding a DPD (N,N-diethyl-p-phenylenediamine) reagent to the water sample, which forms a pink color in the presence of free chlorine. The intensity of the color is proportional to the concentration of free chlorine and can be measured using a colorimeter or spectrophotometer.
2. Amperometric Method:Amperometric chlorine analyzers use an electrode system to measure the electrical current generated by the oxidation of free chlorine at the electrode surface. The current is directly proportional to the concentration of free chlorine in the water sample.
Control of Free Chlorine:
1. Chlorine Residual Monitoring: Regular monitoring of free chlorine residual levels ensures effective disinfection and compliance with regulatory standards. Maintaining a consistent residual concentration throughout the distribution system is essential for ensuring water safety.
2. Chlorine Dosage Control: Proper dosing of chlorine disinfectants in water treatment processes ensures adequate disinfection without exceeding recommended levels or causing undesirable taste and odor issues.
3. pH Adjustment: pH influences the distribution of free chlorine species in water, with hypochlorous acid (HOCl) being more effective at lower pH levels. Adjusting the pH of the water to optimize the equilibrium between HOCl and OCl^- can enhance disinfection efficiency.
4. Residual Maintenance: Maintaining a residual concentration of free chlorine throughout the distribution system, including storage tanks and distribution pipelines, provides continuous disinfection and protects against microbial contamination.
In summary, free chlorine is a vital disinfectant used in water treatment to ensure the safety and quality of drinking water and recreational water facilities. Understanding its forms, sources, importance, measurement methods, and control measures is essential for effective water treatment and distribution.
Dissolved oxygen (DO) refers to the amount of oxygen gas (O2) dissolved in water. It is a critical parameter for assessing the health and quality of aquatic environments, as it directly affects the survival and growth of aquatic organisms, including fish, invertebrates, and algae. Dissolved oxygen is essential for aerobic respiration, the process by which organisms use oxygen to metabolize organic matter and produce energy.
Importance of Dissolved Oxygen:
1. Aquatic Life Support: Dissolved oxygen is necessary for the survival of fish, invertebrates, and other aquatic organisms. Insufficient oxygen levels can lead to fish kills and impairments in aquatic ecosystems.
2. Biological Processes: Oxygen is required for the decomposition of organic matter by aerobic bacteria. Adequate dissolved oxygen levels are essential for maintaining healthy nutrient cycling and water quality in aquatic environments.
3. Water Quality Indicators: Dissolved oxygen serves as an indicator of water quality and ecosystem health. Low DO levels can indicate pollution, eutrophication, or other stressors affecting aquatic habitats.
Factors Affecting Dissolved Oxygen:
1. Temperature: Warm water holds less oxygen than cold water. As water temperature increases, the solubility of oxygen decreases, leading to lower dissolved oxygen levels.
2. Photosynthesis: Photosynthetic organisms such as algae and aquatic plants produce oxygen during daylight hours through photosynthesis, increasing dissolved oxygen levels in water.
3. Aeration: Wave action, waterfalls, and aeration devices can increase oxygen transfer from the atmosphere to water, enhancing dissolved oxygen levels.
4. Organic Matter Decomposition: Decomposition of organic matter by bacteria consumes oxygen, leading to lower dissolved oxygen levels in water bodies with high organic loads.
Dissolved Oxygen Testing:
Dissolved oxygen can be measured using various methods, including:
1. Winkler Method: The Winkler method is a classic titration-based technique for measuring dissolved oxygen in water. It involves adding reagents to a water sample to fix and react with dissolved oxygen, forming a precipitate. The titration of the precipitate with a standardized solution allows for the determination of dissolved oxygen concentration.
2. Electronic Dissolved Oxygen Meters: Electronic meters utilize oxygen-sensitive electrodes to measure dissolved oxygen concentrations directly in water samples. These meters provide rapid and accurate measurements, making them suitable for field and laboratory use.
3. Chemical Sensors: Chemical sensors, such as colorimetric sensors or optical probes, utilize chemical reactions or optical properties to detect dissolved oxygen levels in water. These sensors offer real-time monitoring capabilities and can be deployed in continuous monitoring systems.
Interpretation of Dissolved Oxygen Levels:
- Saturated (> 100%): Water is supersaturated with oxygen, usually due to aeration or photosynthesis.
- Optimal (6-10 mg/L): Suitable for most aquatic organisms, indicating healthy water quality.
- Marginal (4-6 mg/L):May limit the growth and activity of sensitive organisms.
- Stressful (< 4 mg/L):Oxygen stress can occur, leading to reduced growth, reproduction, and survival of aquatic organisms.
- Anoxic (0 mg/L):Complete absence of dissolved oxygen, resulting in severe habitat degradation and fish kills.
In summary, dissolved oxygen is a vital parameter for assessing water quality and supporting aquatic life in natural and engineered water systems. Monitoring dissolved oxygen levels and understanding the factors influencing oxygen dynamics are essential for effective management and conservation of aquatic habitats.
Chemical Oxygen Demand (COD) :
Chemical Oxygen Demand (COD) is a measure of the amount of oxygen required to chemically oxidize organic and inorganic compounds in water. It is a key parameter used to assess the pollution level and organic content in water bodies, wastewater, and industrial effluents. COD is expressed in milligrams of oxygen per liter of water (mg/L).
Importance of Chemical Oxygen Demand:
1. Water Quality Assessment: COD serves as an indicator of the organic pollution level in water bodies. High COD values indicate elevated levels of organic compounds, which can degrade water quality and impair aquatic ecosystems.
2. Wastewater Treatment: COD is used to monitor the efficiency of wastewater treatment processes. By measuring the COD of influent and effluent wastewater, treatment plant operators can assess treatment performance and determine the extent of organic removal.
3. Environmental Monitoring: COD analysis is essential for regulatory compliance and environmental monitoring programs. Regulatory agencies use COD data to establish discharge limits, enforce pollution control regulations, and assess the impact of human activities on water quality.
Measurement of Chemical Oxygen Demand:
The determination of COD involves oxidizing organic and inorganic compounds in water with a strong oxidizing agent, typically potassium dichromate (K2Cr2O7) in an acidic medium. The oxidation reaction is typically carried out using the following steps:
1. Sample Digestion: The water sample is mixed with a known volume of potassium dichromate solution and sulfuric acid (H2SO4). The mixture is heated to high temperature (usually around 150-170°C) in a reflux condenser for a specified digestion period (usually 2 hours). During this process, organic compounds in the sample are oxidized to carbon dioxide (CO2) and water (H2O).
2. Titration: After digestion, the remaining unreacted potassium dichromate is titrated with a standardized solution of ferrous ammonium sulfate (Fe(NH4)2(SO4)2) until the color changes from orange to green. The amount of ferrous ammonium sulfate consumed in the titration is proportional to the amount of unreacted potassium dichromate and, therefore, the COD of the sample.
3. Calculation: The COD of the sample is calculated using the volume and concentration of the ferrous ammonium sulfate solution used in the titration, taking into account any dilutions made during sample preparation.
Interpretation of Chemical Oxygen Demand:
- Low COD (< 10 mg/L): Indicates low levels of organic pollution and high water quality.
- Moderate COD (10-50 mg/L):Suggests moderate organic pollution, which may require treatment to maintain water quality.
- High COD (> 50 mg/L):Indicates high levels of organic pollution, which can degrade water quality and require significant treatment for remediation.
Control and Management of Chemical Oxygen Demand:
1. Source Control: Implementing pollution prevention measures to reduce the discharge of organic pollutants into water bodies and wastewater treatment systems.
2. Wastewater Treatment: Upgrading and optimizing wastewater treatment processes to effectively remove organic compounds and reduce COD levels in effluent discharges.
3. Environmental Protection: Implementing land-use practices and conservation measures to protect aquatic ecosystems and prevent excessive organic loading in water bodies.
4. Regulatory Compliance: Establishing and enforcing water quality standards and discharge limits for COD to protect human health and the environment.
In summary, Chemical Oxygen Demand is a critical parameter used for assessing organic pollution levels in water bodies, monitoring wastewater treatment performance, and protecting aquatic ecosystems. By measuring and managing COD, stakeholders can ensure the sustainable use and protection of water resources.