Environmental Chemistry Exam 2

Prokaryote 

lacks a distinct nucleus and other organelles

Eukaryote

cell or organism with a clearly defined nucleus

Producers

Photosynthetic bacteria and algae

• organisms that produce food for themselves and other organisms. They use energy and simple inorganic molecules to make organic compounds.

Reducers

fungi, protozoa, and most bacteria

• break down organic matter, (as part of decomposition) convert organic matter back into inorganic nutrients for producers to reuse

Chemical processes in water

• Oxidation & Reduction

• Organic matter rxns

Who are the primary producers of organic matter (biomass) in water?

Algae!

Chemoheterotrophs

Use organic sources for both energy and carbon.

Chemoheterotrophs organisms?

All fungi and protozoans, most bacteria

Chemoautotrophs

Use CO2 for biomass and oxidize substances such as H2, NH4+, and S for energy

Chemoautotrophs organisms?

bacteria

Photoheterotrophs

use photoenergy, but are dependent on organic matter for a carbon source

Photoheterotrophs organisms?

few specialized bacteria

Photoautotrophs

use light energy to convert CO2 to biomass by photosynthesis

Photoautotrophs organisms?

algae, and photosynthetic bacteria (cyanobacteria)

Algae 

microscopic organisms that subsist on inorganic nutrients using solar energy and producing biomass from carbon dioxide by photosynthesis

o   CO₂ + H₂O + hν  ⇌ {CH₂O} + O₂

Red tide

a discoloration of seawater caused by a bloom of toxic red dinoflagellates

• causes fish kills 

• toxic - paralyzes nervous system 

Carbon from CO2 or HCO3- : Sulfur from SO4 2- : Nitrogen from NO3-, Trace Elements (iron may be limiting)

Nutrient requirements for algae

In the absence of light

Algae consumes organic matter like other non-photosynthetic organisms

lowers pH

When algae photosynthesize, they take up CO₂ from the water.
CO₂ in water normally forms carbonic acid (H₂CO₃), which ?? pH

increases pH

When algae are not photosynthesizing—for example at night—they switch to respiration, just like animals or fungi. During respiration, algae:

• Release CO₂ into the water

• CO₂ forms carbonic acid

• Carbonic acid releases H⁺ ions

• ?? pH

fungi

nonphotosynthetic eukaryotic organism

•  Most important function in environment is breakdown of plant cellulose with cellulase enzyme

•       Key role in producing humic substance from plant matter

protozoa

microscopic animals composed of single eukaryotic cells

•       Some have chloroplasts and are photosynthetic

•       Form mineral deposits (limestone)

•       Degrade biomass, especially in sewage treatment

•       “Graze” on bacterial cells involved in biodegradation

Bacteria

single-celled prokaryotic microorganisms

•       Large surface/volume ratio makes them very effective biochemical catalysts

•       Autotrophic “ “ get energy from chemicals or light to make all required biochemicals.

•       Heterotrophic “ " get energy from metabolizing organic matter

aerobic bacteria

require O2

anaerobic bacteria

use various substances as electron acceptors, such as nitrate, sulfate, ferric iron, carbon dioxide, or other organic compounds.

Substrate concentration

causes a linear increase in enzyme activity and growth. After some point, the system is saturated and no additional activity or growth will occur.

• Nutrients are an example

Role of biodegradation of organic matter

•       Breaks down organic pollutants (pesticides, petroleum waste, other organic matter)

• Helps detoxify and recycle materials back into the ecosystem

Pesticides

herbicides, fungicides and insecticides

Hydrolysis

Addition of water → molecule splits into 2 products

Role: Major first step in microbial degradation of many pollutants

Example: Malathion (insecticide) → relatively harmless after “ “

Reductions

Gain of electrons or hydrogen

·  Example: Aldehydes → converted to alcohols 

Dehalogenation

Removal of halogen atoms (e.g., Cl) from molecules

·  Role: Important for detoxifying halogenated pollutants

Dealkylation

Removal of –CH₃ (methyl group) from N, S, or O atoms

·  Role: Changes molecular structure → can make compounds less toxic or easier to degrade

• Essential for DNA, RNA, and proteins

• Needed for chlorophyll

• Key nutrient for growth and reproduction in all organism 

Why is nitrogen important

Nitrogen

Limiting nutrient in many systems

excessive amounts of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen

Eutrophication

Denitrification

microbial transformation of nitrogen that increases atmospheric N2

Nitrogen fixation

microbial transformation of nitrogen that decreases atmospheric N2

Ammonia

NH₃

Ammonium

NH₄⁺

Nitrate

NO₃^-

Nitrite

NO₂^-

Reduction

Is nitrogen fixation reduction or oxidation?

•       3{CH₂O} + 2N₂ + 3H₂O + 4H⁺ ⇌ 3CO₂ + 4NH₄⁺

Oxidation

Is nitrification reduction or oxidation?

•       2O₂ + NH₄⁺ ⇌ NO₃^- + 2H⁺ + H₂O

Reduction

Is denitrification reduction or oxidation?

•       4NO₃^- + 5{CH₂O} + 4H⁺ ⇌ 2N₂(g) + 5CO₂ + 7H₂O

Reduction

Is nitrate reduction reduction or oxidation?

•       2NO3- + {CH2O} ⇌ 2NO2- + H2O + CO2

Nitrogen Fixation

few aquatic microbes can fix N. This process is relatively small in aquatic systems. Most N is derived by the degradation of organic matter.

Nitrate Reduction

not assimilated into a biological cell. Purpose is to gain energy. Bacteria under ANAEROBIC conditions. Nitrogen is released.

Denitrification

microbial process where bacteria convert nitrates (NO3) and nitrites NO2 into nitrogen gas, which is then released into the atmosphere. This occurs under anaerobic (oxygen-depleted) conditions

Nitrification

bacteria converts ammonia into nitrites, and then further oxidize the nitrites into nitrates

Ammonification

the process where organic nitrogen (Norg) from dead plants, animals, or waste is converted into ammonium (NH₄⁺) by microbes.

Immobilization

-       NH₄⁺ goes into biomass → nitrogen is trapped. (converted to organic nitrogen compounds by soil microorganisms)

1.        Provides a nutrient source (orthophosphate, PO₄^3-)

2.        Deactivates toxic organophosphate compounds/insecticides

•       Microbial transformations of phosphorothionate and phosphorodithioate ester insecticides (hydrolysis)

Microbial Transformations of Phosphorus

Microbial reduction of sulfate

•       Some bacteria (Thiobacillus thioxidans) oxidize sulfide to sulfuric acid

•       Organosulfur compounds include a variety of sulfur-containing functional groups that are converted to sulfide and eventually sulfate by biodegradation

cometabolism

Dehalogenation reactions carried out by?

cometabolism

simultaneous degradation of two compounds, in which degradation of the second compound depends on the first

Dehalorespiration

reactions in which some anoxic bacteria dechlorinate chlorinated hydrocarbons by replacing Cl by H

•  CH₂O + H₂O + 2Cl-R ⇌ CO₂ + 2H⁺ + 2Cl^- + 2H-R

Organohalide compounds

serve as sole carbon sources, sole energy sources, or electron acceptors for anoxic bacteria

Microbial Transformations of Metals

Bacteria that get energy by catalyzing oxidation of iron(II) to iron(III)

•       Low energy yield → small biomass produces large Fe(OH)3 deposits

Acid Mine Waters

Pyrite (FeS2) exposed by mining → oxidized by bacteria → produces sulfuric acid + Fe(III)

Microbial Transitions of Selenium

Trace nutrient for animals, but toxic in excess

• Dimethyl selenide, is a volatile “ “ compound emitted to the atmosphere by bacterial action

metals/metalloids

Microbes catalyze redox transformations of “?” for energy or detoxification.

contaminant

• Any substance present where it doesn’t belong

• Doesn’t necessarily cause harm

• Can be natural or synthetic

YES, when present in excess (ex: nitrogen or phosphorus, excess sediment in rivers, arsenic in groundwater)

Can naturally occurring substances be pollutants?

Pollutant

• A contaminant that causes harm to organisms, ecosystems, or humans

• Always considered harmful at certain levels

Herbicides

indicate agricultural runoff in water supply

Fecal coliform bacteria

indicate sewage sources in water supply

Biomarkers of water pollution

• Organisms indicate this

• May accumulate pollutants that appear in analysis

o   May show effects from pollutant exposure

o   Fish lipid tissue accumulates persistent organic pollutants

trace elements, heavy metals, inorganics, pesticides, detergents, etc

5 classes of pollutants??

Arsenic

most significant metalloid water pollutant

cadmium, MERCURY, and lead

most harmful heavy metals

Mercury

• trace component of many minerals 

• Causes neurological damage, irritability, paralysis, blindness, insanity, chromosome breakage and birth defects. Sometimes avoids detection because it seems like common behavioral problems.

Minamata Disease

• Hg waste from a chemical plant drained into the bay, affecting hundreds

• Seafood concentrations were 5 to 20 ppm

• presented as a neurological condition caused by severe poisoning from methylmercury

It is mobilized by bacterial methylation, by anaerobic bacteria

How does mercury become a water pollutant

Methylation

the process of adding a methyl group (CH3) to a molecule

cyanide, ammonia, hydrogen sulfide, nitrite ion, sulfite

Example of an inorganic

Acid

•       One of the most common is mine water (H₂SO₄)

•       Potential industrial sources of pollution

Alkalinity

•       Can be worsened by irrigation practices

• “ " can increase due to aggregation of strip mining materials transported in to surface waters with runoff

Salinity

•       Salts such as NaCl and Na₂SO₄

•       Increased in municipal water systems

•       Increased by irrigation (adds salts to soils)

•       accumulation on soils can make them barren, destroying crop productivity and economies.

Dissolved oxygen

•       Depleted by oxidation of NH₄⁺, Fe²⁺, SO₃^2-, and especially  biodegradation of biomass, {CH₂O}

Sewage

Contains many pollutants including pathogenic microorganisms, detergents, salts, solids

Soaps

produce insoluble salts with divalent metal ions, predominantly calcium, which removes them from water, but reduces their effectiveness as cleaning agents in hard water

Detergents

•       Synthetic “ " lower water surface tension and enable its cleaning action

•       Do not form precipitates with hardness ions

•       Amphiphilic structure with ionic “head” and hydrocarbon “tail”

•       concentrate at interfaces of water with air, solids (dirt), and immiscible greases and oils

•       Poorly biodegradable ABS (alkyl benzene sulfonate) surfactants formerly used

Naturally Occurring Chlorinated and Brominated Compounds

•       Produced mostly by marine organisms

•       Chemical defense agents

Bioconcentration

build-up of a chemical in an organism from water only

Bioconcentration factor (BCF)

Substance concentration in organism / 

Substance concentration in water

chemical is hydrophobic/lipophilic → stored in fat tissue

BCF > 1

Bioaccumulation

build-up of a chemical in an organism from multiple sources, including food and water

Bioaccumulation factor (BAF)

considers pollutant concentration in food as well as water

Biomagnification

Increase in pollutant concentration as it moves up the food chain

•       Usually occurs with hydrophobic/lipophilic chemicals

•       Stored in fat tissue → resistant to biodegradation

Hydrophobic organics

readily stored in fat tissues, making them resistant to biodegradation… essentially stored where they stick. Prefer fat over water

insecticide, fungicide, bactericide, herbicide, etc

Know 3-4 pesticide types

Herbicides

most common water pollutant  due to widespread application directly onto soil… and solubility in water

Emerging contaminants

relatively new substances entering the environment, which may have unknown effects

Precautionary principle

the burden of proof that something is not a hazard falls on those introducing the new substance

Perfluorinated compounds PFAS

synthetic chemicals resistant to heat, water, and oil/grease

Stain resistant clothing, firefighting foam, paints, photography and film processing, non-stick cookware, fast food packaging, etc

Sources of PFAS

Eutrophication effects

·      Water quality degradation → turbidity, odors, toxins (from harmful algae)

·      Loss of biodiversity → oxygen depletion kills sensitive species

·      Altered food webs → some species dominate (algae)

·      Sedimentation → lake shallowing, wetland alteration

·      Economic impacts → fisheries collapse, recreational losses

60%

% of water in our body

purification for domestic use, treatment for specialized industrial applications, treatment of wastewater for return and reuse

Three major categories of water treatment