Water Chemistry, Environmental Pollutants, and Polymer Identification

Comprehensive review flashcards covering water chemistry parameters, lake stratification, persistent organic pollutants (POPs), environmental heavy metals, and plastic polymer classification and laboratory testing.

What is water hardness, and which minerals are primarily responsible for causing it?

Water hardness refers to the amount of dissolved minerals in water and is mainly caused by calcium and magnesium.

What gives fresh water a natural buffering capacity that prevents its $pH$ from dropping due to acid rain?

Dissolved bicarbonate and carbonate ions, which neutralize incoming acids and maintain a stable $pH$.

Why is chlorine routinely added to municipal drinking water?

To kill harmful bacteria, viruses, and other disease-causing microorganisms.

What is eutrophication, and what are the two primary nutrients responsible for it?

Eutrophication is the process where excessive nutrients enter a water body, triggering rapid algae growth; the two main driving nutrients are nitrogen and phosphorus.

What are two major nonpoint and point sources of the nutrients that lead to eutrophication?

Fertilizer runoff from agricultural farms and lawns, as well as discharge from sewage and animal waste.

Why does eutrophication make survival difficult for fish and other aquatic organisms?

Excessive algae eventually die and undergo bacterial decomposition, a process that consumes dissolved oxygen and depletes oxygen levels in the water.

What are the three thermal layers of a stratified lake and their distinguishing temperature characteristics?

The epilimnion is the warm upper layer, the metalimnion is the middle layer where temperature declines sharply, and the hypolimnion is the cold bottom layer.

What physical mechanism causes lakes to form distinct thermal layers (epilimnion, metalimnion, and hypolimnion)?

Solar radiation heats the surface water while deeper water remains cold, generating distinct layers of differing temperatures and densities.

In which thermal layer of a lake does photosynthesis primarily occur, and why?

In the epilimnion, because sunlight penetrates sufficiently into this upper layer to drive photosynthetic activity.

Which thermal layer of a stratified lake exhibits the lowest dissolved oxygen concentration, and why?

The hypolimnion, because it receives minimal sunlight for photosynthesis while organic matter decomposition steadily consumes oxygen.

How does an increase in water temperature influence the solubility of dissolved oxygen?

As water temperature increases, oxygen solubility decreases, meaning warmer water holds less dissolved oxygen.

What is the distinction between point source pollution and nonpoint source pollution?

Point source pollution originates from a single, identifiable outlet (such as an industrial pipe), whereas nonpoint source pollution originates from broad, diffuse areas (such as fertilizer runoff).

What are persistent organic pollutants (POPs)?

Toxic chemical compounds that remain in the environment for extended periods without breaking down.

What specific chemical property makes persistent organic pollutants (POPs) resistant to degradation?

They contain unusually strong chemical bonds that resist breakdown via normal chemical reactions.

What specific physical property contributes to the environmental persistence of POPs?

They exhibit low water solubility, preventing them from easily dissolving or being washed away by water.

What is biomagnification?

The progressive increase in the concentration of a toxic chemical in organism tissues at successively higher trophic levels of a food chain.

What was the original intended purpose of the synthetic insecticide DDT?

It was utilized as an insecticide to control mosquito populations and other insect vectors, especially to prevent malaria transmission.

What are endocrine disruptors, and by what mechanisms do they interfere with biological systems?

Chemicals that interfere with normal endocrine signaling by mimicking endogenous hormones, blocking hormone receptors, or altering hormone synthesis and metabolism.

What are three documented adverse physiological effects of endocrine disruptors on wildlife?

Reproductive failure or infertility, abnormal developmental patterns, and behavioral alterations.

What is the primary industrial source of environmental dioxin contamination?

Industrial processes, particularly waste incineration and thermal combustion of chlorine-containing materials.

Of the original "dirty dozen" chemicals targeted by the Stockholm Convention, 10 were intentionally manufactured. What was the origin of the remaining two?

They are unintentionally produced as hazardous byproducts of combustion and chemical synthesis (specifically dioxins and furans).

What federal legislation governing drinking water safety was enacted in 1974, and what does it mandate?

The Safe Drinking Water Act, which mandates that public water supplies comply with federal drinking water standards through regular monitoring and testing.

Why are young children significantly more vulnerable to lead poisoning than adults?

Because children's brains and central nervous systems are actively developing, lead exposure can cause irreversible damage to cognitive function, behavior, and physical development.

What are the two major emission sources of mercury into the atmosphere?

Coal-fired power generation plants, along with industrial manufacturing processes and waste incinerators.

How does inorganic elemental mercury convert into a bioaccumulative form in aquatic ecosystems, and what is its chemical formula?

Aquatic bacteria convert inorganic mercury into methylmercury ($\text{CH}_3\text{Hg}^+$), which is readily absorbed by organisms and bioaccumulates up the aquatic food chain.

How are the terms monomer and polymer defined?

A monomer is a small molecular building block capable of bonding with others; a polymer is a large macromolecule composed of numerous repeating monomer units linked in a chain.

What are three biological polymers and their corresponding monomer subunits?

Proteins (composed of chains of amino acids), starches (composed of chains of glucose molecules), and DNA (composed of repeating A, C, G, and T nucleotide units).

What dimensional criteria differentiate microplastics from nanoplastics?

Microplastics are particles smaller than $5\,\text{mm}$, whereas nanoplastics are sub-micron particles, typically smaller than $1\,\mu\text{m}$.

Which common polymer emits a distinctive green flame during a copper wire flame test, and why?

Polyvinyl chloride (PVC), because chlorine atoms present within the polymer produce a green flame emission.

What are the resin identification codes (1 through 6) and corresponding common applications for standard plastics?

Code 1: PET/PETE (water bottles); Code 2: HDPE (milk jugs); Code 3: PVC (plumbing pipes); Code 4: LDPE (plastic bags); Code 5: PP (food containers); Code 6: PS (foam cups).

What are the densities of the three reference liquids used in the plastics flotation separation scheme?

Water has a density of $1.0\,\text{g/mL}$, $45.5\%$ isopropanol has a density of $0.916\,\text{g/mL}$, and corn oil has a density of $0.93\,\text{g/mL}$.

In qualitative polymer identification tests, which plastic softens in boiling water and which dissolves or softens in acetone?

PETE lacks thermal stability and softens when immersed in boiling water for $30\,\text{seconds}$; Polystyrene (PS) is chemically attacked by acetone, turning soft and sticky.

In spectrophotometric phosphate quantification, at what analytical wavelength is absorbance read, and what reagents generate the blue chromophore?

Absorbance is measured at $650\,\text{nm}$ following the sequential addition of ammonium molybdate reagent (AMS, containing concentrated sulfuric acid) and stannous chloride.