Understanding Ocean Dead Zones

Dead Zones

• Dead zones, also known as biological deserts or hypoxic zones, are ocean areas with very low oxygen concentration.
• These zones typically occur between 200-800 meters below the surface, within the saltwater layer.
• Dead zones emerge when excess chemical nutrients spur algae growth, leading to algal blooms.
• Hypoxic zones can naturally occur because of the upwelling of excess nutrients.
• Human activity can either create or enhance dead zones.
• Dead zones are detrimental to animal life; life either dies or migrates from the zone.

How Dead Zones Form

• Fertilizers, sewage, and nutrients from farming flow down rivers into the sea.
• These nutrients stimulate massive growth of algae blooms.
• Plankton and algae die, sink, decompose, and use up oxygen.
• This causes the area to become starved of oxygen, causing fish to avoid the area.

Bioremediation

• Bioremediation uses microorganisms, like bacteria and fungi, to degrade environmental contaminants into less toxic forms.
• Microorganisms can be designed for bioremediation using genetic engineering.

In Situ Bioremediation

• In situ bioremediation occurs at the site of contamination.
• Bioventing supplies nutrients through wells to contaminated soil to stimulate the growth of bacteria.
• Biosparging involves injecting air under pressure below the water table to increase groundwater oxygen concentrations and enhance the biological degradation of contaminants by bacteria.
• Bioaugmentation imports microorganisms to a contaminated site to enhance degradation.

Ex Situ Bioremediation

• Ex situ bioremediation involves removing the contaminated material for treatment elsewhere.
• Land farming involves excavating contaminated soil, spreading it over a prepared bed, and periodically tilling it until pollutants are degraded.
• The goal is to stimulate indigenous biodegradative microorganisms and facilitate their aerobic degradation of contaminants.
• Bioreactors process contaminated solid material (soil, sediment, sludge) or water through an engineered containment system.
• Composting is nature's recycling of decomposed organic materials into soil.

Air Pollution

• Air pollution refers to undesirable changes in the physical and chemical constituents of the air due to human activities.

Air Pollutants: Source

• Primary pollutants are directly emitted into the atmosphere, for example: CO, SO₂, NOX, and PM.
• Secondary pollutants result from reactions with atmospheric pollutants, for example: Ozone and PAN.

Air Pollutants: Mode of Release

• Indoor releases come from cooking, smoking, or air conditioning, like CO, CO₂, or VOCs.
• Outdoor releases come from industrial processes or transportation, like PM, CO, and VOCs.

Air Pollutants: Chemical Composition

• Particulate matter can be solid or liquid aerosols, like PM2.5 and PM10.
• Gaseous pollutants are miscible with air in vapor form, like SOX, Ozone, NOX, and CO.

Air Pollutants: Persistence

• Primary pollutants persist in the form in which they are added to the environment. -Examples are DDT and plastic.
• Secondary pollutants are formed by an interaction among primary pollutants.
• An example is peroxyacetyl nitrate (PAN), formed by the interaction of nitrogen oxides and hydrocarbons.

Air Pollutants: Existence in Nature

• Quantitative pollutants occur in nature and become pollutants when concentrations exceed a threshold.
• Examples are carbon dioxide and nitrogen oxide.
• Qualitative pollutants don't occur in nature and are man-made.
• Examples are fungicides, herbicides, and DDT.

Air Pollutants: Biodegradability

• Biodegradable pollutants are waste products degraded by natural microbial action, for example, sewage.
• Non-biodegradable pollutants don't decompose naturally or decompose slowly, like plastics or polythene bags.

Air Pollutants: Origin

• Natural pollutants are released during processes like volcanic eruptions or forest fires.
• Anthropogenic pollutants are released during human activities.
• This includes CO₂ emissions from burning fossil fuels.

Sources of Air Pollution: Natural Sources

• Ash from burning volcanoes
• Dust from storms
• Forest fires
• Pollen grains from flowers in air

Sources of Air Pollution: Human Sources

• Power stations using coal or crude oil release CO₂ into the air.
• Furnaces using coal, cattle dung cakes, firewood, and kerosene.
• Steam engines used in railways and motor vehicles.
• Motor and internal combustion engines that run on petrol, diesel, and kerosene.
• Vegetable oils, kerosene, and coal as household fuels.
• Sewers and domestic drains emanating foul gases.
• Pesticide residues in the air.
• Emissions from agriculture, waste treatment, and biomass burning.

Particulate Pollutants

• These are matter suspended in the air, such as dust and soot.
• Major sources are industries, vehicles, construction activities, oil refineries, railway yards, and marketplaces.
• PM10 stands for inhalable particles with diameters generally 10 micrometers and smaller.
• They come from dust stirred up from construction sites, pollen, or emissions from vehicles and industrial processes.
• PM2.5 stands for fine inhalable particles with diameters generally 2.5 micrometers and smaller.
• These particles are often the result of combustion processes like burning fossil fuels and vehicle emissions.
• PM2.5 particles can penetrate deep into our lungs and enter the bloodstream.

Fly Ash

• This is an end product of combustion during power generation in coal-based thermal power plants.
• It consists of silica, alumina, oxides of iron, calcium, magnesium, and heavy metals.
• It is used in manufacturing Portland cement, bricks/blocks/tiles, road embankments, and low-lying area development.

Fluorides

• Sources include aluminum, steel, electrochemical plants, blast furnaces, brick kilns, coal combustion, tile, and glass etching factories.
• Volcanoes also release fluorides which form gaseous as well as particulate pollutants.
• Fluoride particles settle on vegetation, burn tips of leaves, and cause fluorosis in cattle that eat the vegetation.

Water Pollutants and Their Sources

• Pathogens come from sewage, human and animal wastes, and runoff and can cause depletion of dissolved oxygen.
• Organic pollutants include oil, grease, pesticides, plastics, and detergents.
• Inorganic pollutants include fertilizers, phosphates, and nitrates.
• Radioactive materials come from natural sources, uranium mining, and hospitals using radioisotopes.
• Acids and alkalies come from mine drainage and industrial wastes.
• Heat comes from cooling water for industrial and nuclear plants.
• Sediments come from natural erosion and agricultural runoff.

Water Pollution: Control Measures

• Primary treatment involves sedimentation, coagulation, and filtration.
• Secondary treatment involves softening and aeration.
• Tertiary treatment involves disinfection.

Primary Treatment

• Sedimentation allows polluted water to settle so that silt and clay settle to the bottom.
• Coagulation combines fine particles and colloidal suspensions into larger particles.
• This involves adding coagulants like potash alum.
• Filtration filters suspended particles, flocculants, bacteria, and other organisms.
• The collected impurities are called sludge, which can be used as fertilizer.

Secondary Treatment

• This removes undesirable calcium and magnesium ions from hard waters.
• Soft water is exposed to air to add oxygen, encouraging bacterial decomposition of organic matter.
• Aeration reduces carbon dioxide and sulfide.

Tertiary Treatment

• Chlorine is commonly used for disinfection.
• Other methods of disinfection include UV radiation, ozone gas treatment, or reverse osmosis.

Oil Spill Clean-Up

• Skimmers physically separate and retrieve oil from water.
• Sorbents absorb oil from the surface, e.g., volcanic ash.
• Chemical surfactants associate oil into smaller particles to accelerate dispersion.
• Biological agents speed up natural biodegradation.

Convention on Civil Liability for Bunker Oil Pollution Damage

• In 2015, India ratified the International Convention on Civil Liability for Bunker Oil Pollution Damage.
• Aims to ensure adequate and prompt compensation for damage oil spills.
• Administered by the International Maritime Organization (IMO).

Sources of Heavy Metal Ions in Water

• Copper comes from fertilizers, tanning, and photovoltaic cells.
• Zinc comes from soldering, cosmetics, and pigments.
• Silver comes from refining copper, gold, nickel, zinc, jewelry, and electroplating industries.
• Chromium comes from the leather industry, tanning, and chrome plating industries.
• Arsenic comes from wooden electricity poles treated with arsenic-based preservatives, pesticides, fertilizers, and oxidation of pyrite.
• Mercury comes from the combustion of coal, and municipal solid waste incineration.
• Cadmium comes from paints, pigments, electroplated parts, batteries, plastics, and photovoltaic cells.
• Lead comes from PVC pipes, recycled PVC, lead paints, jewelry, and lead batteries.

Agricultural Sources of Pollution

• Fertilizers contain nitrogen, phosphorus, and potassium.
• Pesticides containing chlorinated hydrocarbons, organophosphates, metallic salts, carbonates, and derivatives of acetic acid.
• Animal excreta.
• Excess nitrate in drinking water reacts with hemoglobin to form nonfunctional methemoglobin and impairs oxygen transport causing Methemoglobinemia.
• High levels of nitrates may form carcinogens, accelerating eutrophication.

Thermal Pollution

• Occurs from thermal power plants and nuclear plants releasing hot water.
• This decreases dissolved oxygen in water.

Marine Pollution

• Includes coastal city sewage, garbage disposal, and navigational discharge of oil.

Oil Spills

• Refers to the uncontrolled release of crude oil, gasoline, fuel, or other oil into the atmosphere or water.
• Major environmental problems from intensified petroleum exploration and production.
• Harmful to aquatic life.
• Prevents sunlight from penetrating the surface and reduces the level of dissolved oxygen.
• Oil toxicity results in health issues.
• Methods to clean include oil booms.

Sources of Water Pollution: Community Waste Water

• Includes discharges from houses, commercial, and industrial businesses that connect to public sewage.
• Consists of human waste, food residue, and cleaning agents.

Sources of Water Pollution: Industrial Waste

• Discharges several inorganic and organic pollutants.
• Type of Industry: Mining.
• Inorganic Pollutants: chlorides, metals, ferrous sulphate, hydrogen sulphide, ferric hydroxide, and suspended solids.
• Organic Pollutant: none specified.
• Type of Industry: Iron and Steel.
• Inorganic Pollutants: Suspended solids, iron cyanide, thiocyanate, sulfides, oxides of copper, chromium, cadmium, and mercury.
• Organic Pollutant: oil, phenol, and neptha.
• Type of Industry: Chemical Plants.
• Inorganic Pollutants: acids and alkalies, chlorides, sulfates, nitrates of metals, phosphorus, fluorine, silica and suspended particles.
• Organic Pollutants: aromatic compounds solvents, organic acids, nitro compound dyes, etc.
• Type of Industry: Pharmaceutical.
• Inorganic Pollutants: not specified.
• Organic Pollutants: proteins, carbohydrates, organic solvent intermediate products, drugs and antibiotics.
• Type of Industry: Soap and Detergent.
• Inorganic Pollutants: tertiary ammonium compounds alkalies.
• Organic Pollutants: flats and fatty acids, glycerol, polyphosphates, sulphonated hydrocarbons.
• Type of Industry: Food Processing.
• Inorganic Pollutants: not specified.
• Organic Pollutant: highly putrescible organic matter and pathogens.
• Type of Industry: Paper and Pulp.
• Inorganic Pollutants: sulphides and bleaching liquors.
• Organic Pollutants: cellulose fibres, bark, woods sugars organic acids.

Environmental Pollution

• Is any undesirable alteration in the physical, chemical, or biological attributes of air, land, water or soil.
• Types of Pollution - Air pollution, noise pollution, water pollution, soil pollution, radioactive pollution, light pollution or nitrogen pollution.

Water Pollution

• Water pollution is the presence of undesirable substances or pollutants in water, such as organic, inorganic, biological, radiological and heat, which degrades water quality so that it becomes unfit for use.
• Types of Sources of water pollution, can either be from point sources or non-point sources.
  • Point sources come from a single, identifiable source.
  • Non-point sources come from diffuse sources, like urban and agricultural runoff.
• Natural sources of water pollution = soil erosion and the leaching of minerals from the rocks, due to natural solubility or being triggered by acid rain.