Environmental Management and Atmospheric Air

UNIVERSITY OF MINES AND TECHNOLOGY (UMAT)

  • Location: TARKWA, GHANA

  • Department: Environmental and Safety Engineering Department

  • Motto: Knowledge, Truth, and Excellence

  • Instructor: MR. TEI MESHACK

COURSE INFORMATION

  • Course Title: Environmental Management

  • Course Code: CE/IS 365

COURSE CONTENT

  1. The Atmospheric Air and Mine Environment

  2. Air Parameters

  3. Gases

  4. Dust/Particulate Matter

  5. Detection of Gases and Particulates Matter

  6. Air Pollution

  7. Heat in the Work Environment/Thermal Stress

  8. Water Quality and Pollution

  9. Instruments Used in Water Quality Analysis

  10. Environmental Impact Assessment

COURSE OBJECTIVES

  • Objective 1: To provide students with the concepts of the mining environment, environmental pollution, and management.

  • Objective 2: To help students gain a better understanding of pollutants released into the environment by mining activities.

  • Objective 3: To discuss how these pollutants affect the environment.

  • Objective 4: To learn how pollutants are measured and managed.

MODE OF DELIVERY

  • Lectures: Face-to-face and online (Zoom)

  • Tutorials, group works, and assignments

  • Practical sessions in the Environmental Monitoring Laboratory at UMaT

MODE OF ASSESSMENT

  • Quizzes, laboratory sessions, and individual/group assignments: 30%

  • Attendance and active participation in class: 10%

  • Final examination: 60%

REFERENCE MATERIALS

  1. Tapas, K. (2020), Industrial Environmental Management: Engineering, Science, and Policy, Wiley Publication, 1st Edition, 576 pp.

  2. Jorgensen, N. and Sven, E. (2020), Environmental Management of Marine Ecosystems, CRC Press, 1st Edition, 384 pp.

  3. Manuele, F. (2020), Advanced Safety Management, Wiley Publication, 3rd Edition, 560 pp.

  4. Mick, W. (2019), An Operations Guide to Safety and Environmental Management Systems (SEMS), Gulf Professional Publishing, 1st Edition, 190 pp.

CHAPTER 1: ATMOSPHERIC AIR AND MINE ENVIRONMENT

ATMOSPHERIC AIR

  • Definition: The atmosphere is the layer of gases surrounding the Earth, held by gravity. It protects life on Earth by:

    • Absorbing ultraviolet solar radiation.

    • Warming the surface through the greenhouse effect.

    • Reducing temperature extremes (diurnal temperature variations).

  • Atmospheric air is defined as the air prevailing under atmospheric conditions such as pressure and temperature, which vary with location and wind patterns.

  • Composition: Atmospheric air is a mixture of gases in variable proportions and contains water vapor (average ~1% at sea level).

AIR COMPOSITION

Table 0.1: Proportion of Gases in Atmospheric Air

Gas

Proportion (% by Volume)

Proportion (% by Weight)

Nitrogen

78.09

75.55

Oxygen

20.95

23.13

Carbon Dioxide

0.04

0.05

Argon & Others

0.93

1.27

  • Other trace constituents include:

    • Helium (He), Neon (Ne), Krypton (Kr), Xenon (Xe),

    • Sulfur Dioxide (SO2), Nitrogen Dioxide (NO2), Methane (CH4), Nitrous Oxide (N2O), Ammonia (NH3), Ozone (O3), Carbon Monoxide (CO)

AIR PROPERTIES

  • Characteristics of atmospheric air can be determined through physical and chemical properties such as:

    • Density

    • Pressure

    • Temperature

DENSITY

Specific Weight (𝛾 or w)

  • Specific weight of air is defined as the weight (W) of a unit volume (v) of air: W = mg ext{Specific Weight (𝛾)} = rac{W}{v} = rac{mg}{v} ext{ [N/m³]}

    • Variables:

    • m = mass of the air

    • g = local gravitational acceleration

Mass Density (ρ)

  • Mass density is defined as the mass (m) per unit volume (v) of air:

    ho = rac{m}{v} = rac{w}{g} imes rac{1}{v} = rac{𝛾}{g} ext{ [kg/m³]}

Specific Gravity (Sg or S)

  • Refers to the ratio of the density of a gas to that of air:
    Sg_{ ext{dry air}} = 1

Specific Volume (Vp or v)

  • The volume of air per unit mass of dry air:
    Vp = rac{v}{m} = rac{1}{
    ho} ext{ [m³/kg]}

PRESSURE (P)

  • Defined as the force exerted perpendicular to the surface of an object per unit area:
    P = rac{F}{A} ext{ [N/m²] or [Pa]}

  • Types of Pressure:

    • Absolute Pressure (P)

    • Gauge Pressure (Pressure Difference)

Atmospheric Pressure

  • Also known as Barometric pressure, measured with a barometer.

TEMPERATURE (T)

  • Temperature is measured with a thermometer and can be represented in degrees Celsius (ºC) or degrees Fahrenheit (ºF).

  • Absolute Temperature Conversion:

    • Kelvin: K = t_{[ºC]} + 273 (0 K = -273 ºC)

    • Rankine: R = t_{[ºF]} + 459 (0 R = -459 ºF)

  • Temperature Conversion Between Degrees:

    • From Fahrenheit to Celsius: T{[ºC]} = rac{5}{9}(T{[ºF]} - 32)

    • From Celsius to Fahrenheit: T{[ºF]} = rac{9}{5}T{[ºC]} + 32

Dry Bulb Temperature (DBT)

  • DBT is the temperature measured by a thermometer exposed to the air but shielded from direct radiation and moisture.

  • It reflects the true thermodynamic temperature.

  • It indicates the amount of heat in the air, directly proportional to mean kinetic energy of air molecules.

Wet Bulb Temperature (tw)

  • tw is defined as the temperature a parcel of air would have if cooled to saturation (100% relative humidity) by evaporating water into it.

  • Determined by both DBT and moisture (humidity). - At 100% relative humidity, tw = DBT.

Wet Bulb Globe Temperature (WBGT)

  • WBGT estimates the apparent temperature considering temperature, humidity, wind speed, and solar radiation effects.

  • Used by industrial hygienists, athletes, and military for exposure levels to high temperatures.

  • Formula: WBGT = 0.7T{w} + 0.2T{g} + 0.1T_{d}

    • Where:

      • tw = Natural wet-bulb temperature (indicative of humidity)

      • Tg = Globe thermometer temperature

      • Td = Dry-bulb temperature

  • Temperatures can be in either Celsius or Fahrenheit.

Example Calculation: WBGT

  • Given:

    • Wet bulb temperature, tw = 29 ºC

    • Globe temperature, Tg = 36 ºC

    • Dry bulb temperature, Td = 33 ºC

    • Calculation:
      WBGT = 0.7(29) + 0.2(36) + 0.1(33) = 20.3 + 7.2 + 3.3 = 30.8 ºC

  • Interpretation: Since WBGT = 30.8°C and action level is 30°C, action required includes work-rest cycles, hydration, and shade breaks.

Dew Point Temperature (tdp)

  • Defined as the temperature at which condensation of water vapor occurs, indicating saturation temperature.

  • When cooled further, airborne water vapor condenses to form liquid water (dew).

HUMIDITY

Absolute Humidity

  • The absolute humidity is expressed in grams of water vapor per cubic meter of air (g/m³).

Relative Humidity (𝞿)

  • The ratio of mass of water vapor to total mass of moist air or vapour pressures of air. 𝞿 = rac{P{v}}{P{sat}} imes 100 [ extrm{%}] OR 𝞿 = rac{w}{W} imes 100 [ extrm{%}]

    • Where:

    • w = weight of water vapor

    • W = weight of water vapor at saturation

  • At 100% relative humidity, air is fully saturated with water vapor.

Specific Humidity (x or w)

  • Defined as the weight of water vapor per unit weight of dry air:
    X = 0.622 imes rac{𝞿
    hov}{ρ - ρv} = 0.622 imes rac{Pv}{P - Pv} ext{ [kg/kg]}

Degree of Saturation (µ)

  • The ratio between specific humidity at a given condition and that at saturated conditions. µ = rac{x}{xi} = rac{𝞿 imes (P - Pv{s})}{(P - Pv)} [ extrm{%}]

    • Where:

    • P = atmospheric pressure

    • Pv = water vapor pressure

    • Pvs = saturation vapor pressure

ENTHALPY (I or H)

  • Defined as the total heat content of air, measured in [kJ/kg] or [Kcal/kg].

  • It is the sum of the enthalpies of dry air and water vapor.

ENTROPY (S)

  • Defined as the ratio of heat added to air to the absolute temperature at which it is added, measured in [J/kg K] or [kJ/kg ºC].

VISCOSITY

Types of Viscosity

  1. Absolute or Dynamic Viscosity (µ)

    • Property of air opposing resistance to flow due to friction and drag.

    • Measured in kg/m².

  2. Kinematic Viscosity (ν)

    • The ratio between absolute viscosity and mass density of air:
      v = rac{µ}{ρ} ext{ and } ρ = 𝛾 g ext{ so } v = rac{µ}{𝛾 g} [m²/s]

MINE ATMOSPHERE

  • Defined as the air surrounding a mine comprising a mixture of natural atmospheric air and gases, dust, and fumes produced at mine sites.

  • Changes in the mine atmosphere include:

    • Composition change

    • Temperature change

    • Humidity change

  • Compared to surface atmospheric air, mine air generally contains less O2 and more N2 and CO2 due to oxidation and CO2 release from rocks.

  • Normal mine atmospheres contain:

    • O2: No less than 20%

    • CO2: Not more than 0.5-1.0%

Gaseous Impurities in Mine Atmospheres

  • Poisonous vapours include:

    • Carbon monoxide

    • Nitrogen oxides

    • Hydrogen sulfide

    • Sulfur dioxide

    • Aldehydes

    • Radioactive decay products

Specific Gaseous Components

Carbon Monoxide

  • Formed during blasting, fires, and equipment exhausts.

  • Maximum permissible before health risks: 20 mg/m³.

Nitrogen Oxides (NOx)

  • Present in blasting and diesel exhausts.

  • Maximum permissible concentration: 5 mg/m³.

    • Note: Investigate examples of NOx species.

Hydrogen Sulfide

  • Produced during decay of organic matter and as a result of certain mining processes.

  • Maximum permissible concentration: 10 mg/m³.

Sulfur Dioxide

  • Occurs from blasting rocks containing sulfur and combustion processes.

  • Maximum permissible concentration: 10 mg/m³.

Aldehydes

  • Present in diesel exhausts with maximum limits of:

    • Acrolein: 0.7 mg/m³

    • Formaldehyde: 0.5 mg/m³

Radioactive Decay Products

  • Radon gas is released in uranium mines; max permissible is 1.10⁻¹¹ curie per liter.

    • Other hazardous vapours include mercury vapours, gasoline vapours, heavy hydrocarbons, ammonia, and oil gas.

Explosive Gases in Mine Atmospheres

  • May include:

    • Methane: Main source in coal mines with max explosive limit of 0.5–2.0% v/v.

    • Hydrogen: Found primarily in potassium mines with a limit of 0.5% v/v.

  • Other explosive and toxic gases include gasoline vapours, carbon monoxide, and hydrogen sulfide, with limits as per health regulations.

Ventilation in Mine Atmospheres

  • The primary method to maintain purity in the mine atmosphere is ventilation.

    • During cold weather, incoming air to shafts is heated.

    • Artificially cooled air is employed to reduce temperatures in the mine atmosphere.

Example Mine Air Monitoring

Problem Statement:

  • Following blasting at a Tarkwa gold mine, monitoring indicated NOx concentration of 7.5 mg/m³ (N₂O₅ equivalent).

  • Permissible limit is 5 mg/m³. #### Solution Steps:

  1. Calculate reduction required: 7.5 − 5.0 = 2.5 mg/m³.

  2. Calculate percentage reduction: rac{2.5}{7.5} imes 100 = 33.3 ext{%}.

  3. Control Measures:

    • Increase auxiliary ventilation airflow.

    • Extend post-blast waiting time and limit diesel equipment usage in the area.

COURSE CONTENT 1. The Atmospheric Air and Mine Environment

  1. Air Parameters

  2. Gases

  3. Dust/Particulate Matter

  4. Detection of Gases and Particulates Matter

  5. Air Pollution

  6. Heat in the Work Environment/Thermal Stress

  7. Water Quality and Pollution

  8. Instruments Used in Water Quality Analysis

  9. Environmental Impact Assessment

Detailed Outline:

  1. The Atmospheric Air and Mine Environment

    • Overview of how mining operations impact the atmosphere.

    • Study of atmospheric circulation patterns and their influence on air quality in mining areas.

  2. Air Parameters

    • Analysis of critical parameters: humidity, temperature, pressure, and their effects on air quality.

    • Importance of understanding parameters for environmental monitoring in mining.

  3. Gases

    • Identification and study of key gases emitted during mining operations and their effects on health and environment.

  4. Dust/Particulate Matter

    • Sources and types of dust generated in mines, including PM10 and PM2.5.

    • Health impacts of particulate matter exposure.

  5. Detection of Gases and Particulate Matter

    • Monitoring technologies and techniques for detecting harmful gases and dust in the mining environment.

  6. Air Pollution

    • Overview of air pollution sources: industrial, vehicular, and natural.

    • Legislation and regulations governing air quality in mining.

  7. Heat in the Work Environment/Thermal Stress

    • Impacts of heat stress on workers in mining environments.

    • Strategies for heat management and mitigation in mine settings.

  8. Water Quality and Pollution

    • Examination of the effects of mining on water sources.

    • Discussions on contaminated runoff and its impact on local ecosystems.

  9. Instruments Used in Water Quality Analysis

    • Detailed look at techniques such as spectrophotometry, titrimetric methods, and chromatography used for analyzing water quality.

  10. Environmental Impact Assessment

    • Comprehensive framework for conducting an EIA in mining projects.

    • Importance of stakeholder engagement and mitigation planning in the assessment process.