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Environmental Science Quiz

17 Questions 11 min

This Environmental Science Quiz checks your ability to interpret ecosystem energy flow, biogeochemical cycles, climate forcing, and pollution control decisions. Expect unit work with mg/L, µg/L, ppm, and pH, plus mass balance and loading calculations. It supports environmental technicians, sustainability coordinators, and environmental science students preparing for field and lab work.

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Part 1 — Questions

Answer each question on paper. Do not turn the page until you are ready to check your work.

In most ecosystems, producers capture energy (often sunlight) and convert it into chemical energy that supports the rest of the food web.

True
False

You are checking a lab report for a freshwater stream. Which approximation is usually acceptable for dilute freshwater concentrations?

1 µg/L ≈ 1 ppm
1 mg/L ≈ 10 ppm
1 mg/L ≈ 1 ppb
1 mg/L ≈ 1 ppm

Stratospheric ozone is the main gas responsible for the greenhouse effect because it traps infrared radiation near Earth’s surface.

True
False

A flow meter reports 0.80 m³/s and you need the same value in L/s for a load calculation. What is the correct conversion?

80 L/s
8000 L/s
0.80 L/s
800 L/s

A pond has about 10,000 kJ/day of energy stored in algae production. Using the typical ecological efficiency rule of thumb, about how much energy is available to the next trophic level (herbivores) as new biomass?

1000 kJ/day
9000 kJ/day
10,000 kJ/day
5000 kJ/day

A stream below a discharge shows very high BOD. What is the most likely immediate ecological consequence?

Higher salinity because BOD is a salt measure
Lower pH because oxygen turns into acid
Higher dissolved oxygen because microbes are active
Lower dissolved oxygen because microbes consume oxygen

Which situation is most clearly a point source of water pollution?

Dust settling into a lake over the summer
Treated effluent released from a single outfall pipe
Fertilizer washed off fields during a storm
Oil droplets carried by street runoff across many blocks

Because ppm and mg/L are both “parts” units, 1 ppm of a gas in air can be treated as 1 mg/L without additional information.

True
False

A stream’s pH changes from 7.0 upstream to 6.0 downstream after an industrial spill. About how much does hydrogen ion activity increase?

5×
10×
100×
2×

10.

A drop in pH from 8 to 6 corresponds to a 100-fold increase in hydrogen ion activity.

True
False

11.

You have 100 mL of a 200 mg/L solution and dilute it to a final volume of 1.0 L. Assuming perfect mixing, what is the final concentration?

2 mg/L
20 mg/L
200 mg/L
50 mg/L

12.

A lab report shows 250 µg/L of dissolved copper in a creek. What is this in mg/L?

2.5 mg/L
0.00025 mg/L
0.025 mg/L
0.25 mg/L

13.

A lake shows rapid algae growth each summer, and a nutrient bioassay finds that adding phosphorus alone produces the biggest productivity jump. Which nutrient is acting as the limiting nutrient in this test?

Phosphorus
Carbon
Potassium
Nitrogen

14.

A wildlife survey shows a deer population rising quickly, then leveling off as food becomes scarce and disease increases. Which population model best matches this pattern?

Logistic growth
Random walk
Linear growth
Exponential growth

15.

A plant’s effluent contains a mix of low-level dissolved organic compounds causing taste and odor issues. Which treatment is most directly aimed at removing many dissolved organics from water?

Activated carbon adsorption
Chlorination only
Screening
Sedimentation

16.

Two monitoring stations report the following. Station 1, 1 mg/L nitrate at 5 m³/s. Station 2, 4 mg/L nitrate at 0.5 m³/s. Which station delivers the higher nitrate mass per second to downstream waters?

Station 1
Not enough information
Station 2
They are equal

17.

A constructed wetland cell is intentionally kept low in dissolved oxygen to remove nitrogen from inflowing water. Which microbial process is most responsible for permanent nitrogen removal as a gas?

Denitrification
Nitrification
Nitrogen fixation
Ammonification

18.

An air-quality sensor reports 50 ppm of a gas and you need a mass concentration (like mg/m³). Which statement is most accurate?

ppm in air is always the same as mg/L
You must know molecular weight and temperature and pressure (or assume standard conditions)
ppm can be converted to mg/m³ by multiplying by 1000
ppm can be converted to mg/m³ using only the flow rate

Part 2 — Answer key

Compare your answers after you have finished Part 1.

In most ecosystems, producers capture energy (often sunlight) and convert it into chemical energy that supports the rest of the food web.
True
You are checking a lab report for a freshwater stream. Which approximation is usually acceptable for dilute freshwater concentrations?
1 mg/L ≈ 1 ppm
Stratospheric ozone is the main gas responsible for the greenhouse effect because it traps infrared radiation near Earth’s surface.
False
A flow meter reports 0.80 m³/s and you need the same value in L/s for a load calculation. What is the correct conversion?
800 L/s
A pond has about 10,000 kJ/day of energy stored in algae production. Using the typical ecological efficiency rule of thumb, about how much energy is available to the next trophic level (herbivores) as new biomass?
1000 kJ/day
A stream below a discharge shows very high BOD. What is the most likely immediate ecological consequence?
Lower dissolved oxygen because microbes consume oxygen
Which situation is most clearly a point source of water pollution?
Treated effluent released from a single outfall pipe
Because ppm and mg/L are both “parts” units, 1 ppm of a gas in air can be treated as 1 mg/L without additional information.
False
A stream’s pH changes from 7.0 upstream to 6.0 downstream after an industrial spill. About how much does hydrogen ion activity increase?
10×
A drop in pH from 8 to 6 corresponds to a 100-fold increase in hydrogen ion activity.
True
You have 100 mL of a 200 mg/L solution and dilute it to a final volume of 1.0 L. Assuming perfect mixing, what is the final concentration?
20 mg/L
A lab report shows 250 µg/L of dissolved copper in a creek. What is this in mg/L?
0.00025 mg/L
A lake shows rapid algae growth each summer, and a nutrient bioassay finds that adding phosphorus alone produces the biggest productivity jump. Which nutrient is acting as the limiting nutrient in this test?
Phosphorus
A wildlife survey shows a deer population rising quickly, then leveling off as food becomes scarce and disease increases. Which population model best matches this pattern?
Logistic growth
A plant’s effluent contains a mix of low-level dissolved organic compounds causing taste and odor issues. Which treatment is most directly aimed at removing many dissolved organics from water?
Activated carbon adsorption
Two monitoring stations report the following. Station 1, 1 mg/L nitrate at 5 m³/s. Station 2, 4 mg/L nitrate at 0.5 m³/s. Which station delivers the higher nitrate mass per second to downstream waters?
Station 1
A constructed wetland cell is intentionally kept low in dissolved oxygen to remove nitrogen from inflowing water. Which microbial process is most responsible for permanent nitrogen removal as a gas?
Denitrification
An air-quality sensor reports 50 ppm of a gas and you need a mass concentration (like mg/m³). Which statement is most accurate?
You must know molecular weight and temperature and pressure (or assume standard conditions)

1In most ecosystems, producers capture energy (often sunlight) and convert it into chemical energy that supports the rest of the food web.

True / False

2You are checking a lab report for a freshwater stream. Which approximation is usually acceptable for dilute freshwater concentrations?

3Stratospheric ozone is the main gas responsible for the greenhouse effect because it traps infrared radiation near Earth’s surface.

True / False

4A flow meter reports 0.80 m³/s and you need the same value in L/s for a load calculation. What is the correct conversion?

5A pond has about 10,000 kJ/day of energy stored in algae production. Using the typical ecological efficiency rule of thumb, about how much energy is available to the next trophic level (herbivores) as new biomass?

6A stream below a discharge shows very high BOD. What is the most likely immediate ecological consequence?

7Which situation is most clearly a point source of water pollution?

8Because ppm and mg/L are both “parts” units, 1 ppm of a gas in air can be treated as 1 mg/L without additional information.

True / False

9A stream’s pH changes from 7.0 upstream to 6.0 downstream after an industrial spill. About how much does hydrogen ion activity increase?

10A drop in pH from 8 to 6 corresponds to a 100-fold increase in hydrogen ion activity.

True / False

11You have 100 mL of a 200 mg/L solution and dilute it to a final volume of 1.0 L. Assuming perfect mixing, what is the final concentration?

12A lab report shows 250 µg/L of dissolved copper in a creek. What is this in mg/L?

13A lake shows rapid algae growth each summer, and a nutrient bioassay finds that adding phosphorus alone produces the biggest productivity jump. Which nutrient is acting as the limiting nutrient in this test?

14A wildlife survey shows a deer population rising quickly, then leveling off as food becomes scarce and disease increases. Which population model best matches this pattern?

15A plant’s effluent contains a mix of low-level dissolved organic compounds causing taste and odor issues. Which treatment is most directly aimed at removing many dissolved organics from water?

16Two monitoring stations report the following. Station 1, 1 mg/L nitrate at 5 m³/s. Station 2, 4 mg/L nitrate at 0.5 m³/s. Which station delivers the higher nitrate mass per second to downstream waters?

17A constructed wetland cell is intentionally kept low in dissolved oxygen to remove nitrogen from inflowing water. Which microbial process is most responsible for permanent nitrogen removal as a gas?

18An air-quality sensor reports 50 ppm of a gas and you need a mass concentration (like mg/m³). Which statement is most accurate?

Environmental Science Quiz Pitfalls: Units, Loads, pH, and Food-Web Logic

1) Treating ppm, mg/L, and µg/L as interchangeable

What goes wrong: People convert without checking the medium and end up off by 1000×. Water problems often allow the shortcut 1 mg/L ≈ 1 ppm only for dilute freshwater. Air ppm is usually a mixing ratio and does not convert the same way.

Fix: Write the unit path first (for example, µg/L → mg/L by dividing by 1000). State the medium (freshwater, seawater, air) before using any approximation.

2) Confusing concentration with mass loading

What goes wrong: A “low” concentration can still create a large total impact if flow is high, so the wrong control gets chosen.

Fix: Use Load = C × Q and keep units consistent (mg/L with L/s, or kg/day with m³/day). Decide whether the prompt asks for water quality (concentration) or total input (load).

3) Misreading pH as linear

What goes wrong: A 1 unit change in pH gets treated as small, leading to wrong conclusions about acidity stress and buffering.

Fix: pH is logarithmic. A 1 unit drop means 10× higher hydrogen ion activity, and a 2 unit drop means 100×.

4) Breaking ecosystem and cycle reasoning

What goes wrong: Decomposers get labeled as producers, omnivores get locked into one trophic level, or “nutrient cycling” gets mistaken for one-way energy flow.

Fix: Producers fix carbon, decomposers recycle nutrients, and energy transfer between trophic levels is inefficient (often summarized as about 10% passing upward).

5) Mixing up bioaccumulation and biomagnification

Fix: Bioaccumulation is build-up within one organism over time. Biomagnification is increasing concentration across trophic levels in a food web.

6) Picking controls that do not match the source type

Fix: Point sources often fit end-of-pipe treatment. Nonpoint runoff often needs source reduction, land management, and erosion and nutrient controls upstream.

Environmental Science Quick Sheet: Units, Mixing, Cycles, and Control Selection (Printable)

Print note: You can print this page or save it as a PDF using your browser’s print dialog for offline review.

Units and fast conversions

Water concentration: 1 mg/L = 1000 µg/L. For dilute freshwater, 1 mg/L ≈ 1 ppm and 1 µg/L ≈ 1 ppb are common approximations.
Volume flow: 1 m³ = 1000 L. Convert m³/s to L/s by multiplying by 1000.
Temperature intervals: Δ°C = ΔK.

Core formulas (show units on every line)

Simple dilution (same solute): C₁V₁ = C₂V₂
Two-stream mixing: C_mix = (C₁Q₁ + C₂Q₂) / (Q₁ + Q₂)
Mass loading: Load = C × Q (example units: mg/L × L/s = mg/s)
Daily load conversion: mg/s → kg/day: multiply by 86,400 and divide by 1,000,000
pH: pH = −log₁₀[H⁺]. A 1 unit pH drop means 10× higher [H⁺].

Ecosystems and biogeochemical cycles

Energy flow: Energy is lost as heat at each trophic transfer, so biomass typically decreases up the food chain.
Limiting nutrient: Productivity is constrained by the nutrient in shortest effective supply. Many freshwater systems are often phosphorus-limited unless the prompt specifies otherwise.
Carbon vs nutrients: Carbon moves through the atmosphere, biosphere, hydrosphere, and lithosphere. Nitrogen and phosphorus have key “bottlenecks” in biology, soils, and waters.

Pollution control matching

Point source: permits, process changes, and treatment (for example, nitrification and denitrification for nitrogen, precipitation for some metals).
Nonpoint runoff: source reduction (fertilizer timing and rate), infiltration, riparian buffers, erosion control, and stormwater retention.
Fate and transport cues: high solubility suggests dissolved-phase transport, hydrophobic organics often sorb to sediment and can biomagnify.

Worked Environmental Science Example: Mixing, Loading, and a Control Decision

Scenario: A tributary (Stream A) with nitrate-N at 2.0 mg/L flows into a river (Stream B) at 0.20 mg/L. Stream A has Q = 0.50 m³/s and Stream B has Q = 1.50 m³/s. Estimate the downstream mixed concentration and the total nitrate load, then decide which source matters more.

Convert flows to consistent units.
0.50 m³/s = 500 L/s. 1.50 m³/s = 1500 L/s.
Compute mixed concentration using flow-weighted mixing.
C_mix = (2.0 mg/L × 500 L/s + 0.20 mg/L × 1500 L/s) ÷ (500 + 1500) L/s
= (1000 + 300) mg/s ÷ 2000 L/s = 0.65 mg/L.
Compute each source’s mass loading.
Load_A = 2.0 mg/L × 500 L/s = 1000 mg/s = 1.0 g/s.
Load_B = 0.20 mg/L × 1500 L/s = 300 mg/s = 0.30 g/s.
Total load = 1300 mg/s = 1.3 g/s.
Convert total load to kg/day (if asked).
1.3 g/s × 86,400 s/day = 112,320 g/day = 112 kg/day.
Interpretation for mitigation.
Even though Stream B has the higher flow, Stream A contributes most of the load (1.0 g/s out of 1.3 g/s). If Stream A is a point discharge, treatment or process changes upstream can reduce most of the downstream nitrate load. If it is agricultural runoff, source reduction and field-scale controls fit better than end-of-pipe treatment.

Environmental Science Quiz FAQ: Units, pH, Cycles, and Pollution Controls

When is 1 mg/L equal to 1 ppm, and when is it not?

For dilute freshwater, 1 mg/L is often treated as approximately 1 ppm because 1 liter of water has a mass close to 1 kilogram. The approximation breaks down for higher salinity, higher concentrations, and for air pollutants where ppm is typically a mixing ratio, not a mass-per-volume unit.

Why do some questions insist on load (mg/day) instead of concentration (mg/L)?

Concentration answers “how strong is it right here.” Load answers “how much mass enters the system per time.” Many ecological impacts and regulatory limits depend on total input, especially where high flow can deliver large mass even at modest concentrations. Use Load = C × Q and keep units consistent.

How should I reason about pH changes without a calculator?

Use powers of ten. A 1 unit pH drop means 10× higher hydrogen ion activity. A 2 unit drop means 100× higher. Many quiz items only need the factor change or a comparison of relative acidity, not an exact [H+] value.

What is the fastest way to avoid errors in two-stream mixing problems?

Write Q and C for each stream in a two-row table, then compute C_mix from (C₁Q₁ + C₂Q₂) ÷ (Q₁ + Q₂). Check that your numerator has mass per time units before dividing. If you see mg/L multiplied by m³/s, convert m³ to L first.

How do I tell bioaccumulation from biomagnification in food-web questions?

Bioaccumulation is within one organism over time, often tied to uptake exceeding elimination. Biomagnification is across trophic levels, where predators end up with higher tissue concentrations than their prey. Hydrophobic, persistent chemicals stored in fat are common biomagnification candidates.

What is a common trap in climate forcing questions?

Mixing up forcing, feedback, and variability. Radiative forcing is an imposed change to Earth’s energy balance, such as increased greenhouse gas concentrations. Feedbacks are system responses that amplify or dampen the initial change, such as ice-albedo feedback. Prompts often test sign logic (warming vs cooling) and direction of causality.

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