A-Level Environmental Science: Topic 2 - Atmosphere and Hydrological Cycle

Flashcards covering the A-Level Environmental Science Topic 2 syllabus, including the hydrosphere, water cycle, human impacts, aquifers, reservoirs, and water treatment processes.

What consists of the hydrosphere and what are the three forms of water it contains?

The hydrosphere is one of the main reservoirs on the Earth and contains all of water in solid, liquid, and gas forms (e.g., lakes, rivers, ice, snow, and water vapour).

What is the chemical formula for water and how is it structured?

The chemical formula is $H_2O$, consisting of two hydrogen atoms joined to one oxygen atom.

How do water molecules bond together and what determines the state of water?

Water molecules join via hydrogen bonds, which are weak individually but strong in numbers; the number of these bonds determines if water is in a solid, liquid, or gas state.

At what temperatures does water change state?

Water boils and evaporates at $100^{\circ}\text{C}$ or higher and freezes into ice at $0^{\circ}\text{C}$ or lower.

Why is water described as dipolar and what is the environmental significance of this?

Water is dipolar because oxygen carries a slight negative charge while hydrogen carries a slight positive charge ($\delta -$ and $\delta +$), making it a universal solvent that dissolves charged compounds like salt ($NaCl$).

What is the significance of water's high specific heat capacity?

It requires a large amount of energy to change the water temperature even by $1^{\circ}\text{C}$, creating a stable habitat in lakes and rivers and a stable internal environment for organisms.

How does the density of ice compare to liquid water and why is this important?

Ice is less dense than liquid water, allowing it to float; this acts as an insulator, preventing whole water bodies from freezing and allowing wildlife to survive under the surface.

Define Transpiration.

The process where water evaporates from the leaves of plants to become water vapour in the atmosphere.

What is the meaning of 'dynamic equilibrium' in the context of natural cycles?

A state of balance where processes cancel each other out; all natural cycles exist in this state until unbalanced by human activity.

What is the equation for calculating the residence time of water in a reservoir?

$\text{Residence Time} = \frac{\text{Volume in reservoir}}{\text{Mean transfer rate}}$

What provides the energy to drive the hydrological cycle and how is it converted?

The sun provides solar energy (heat) for evaporation; this is converted to gravitational potential energy in clouds and then to kinetic energy as water falls.

Distinguish between Infiltration and Percolation.

Infiltration is water soaking into the soil from the surface, while percolation is water moving downwards through the rocks below the soil.

How does deforestation impact the hydrological cycle?

It reduces transpiration (lowering downwind rainfall), reduces interception (increasing rain hitting the ground), and increases soil erosion and surface runoff.

How do agricultural practices like using heavy machinery affect the water cycle?

Ploughs and tractors compact the soil, making it less permeable, which decreases infiltration and increases surface runoff.

What is the 'positive feedback mechanism' associated with snow and ice melt in climate change?

As snow and ice melt, more UV radiation is absorbed by the Earth's surface (rather than being reflected), leading to further warming and more melting.

Which industry accounts for approximately $70\%$ of global water demand?

Agriculture, primarily due to the high water requirements for irrigation.

What are the primary reasons for the increasing global demand for water?

Rising populations, increased affluence leading to higher per capita use, increased need for irrigation, and the industrialisation of Low-Income Countries (LICs).

What is a waterborne bacterial disease that spreads faster when clean water is scarce?

Cholera.

Define the terms 'porous' and 'permeable' in relation to aquifers.

Porous means the rock contains air spaces (pores) to hold water; permeable means the air spaces are interconnected so water can flow through easily.

Which rock types are suitable for forming aquifers?

Chalk, limestone, and sandstone (clay is unsuitable as it is impermeable).

What is salt water incursion?

A risk when over-exploiting aquifers where salt water from the ocean flows into a freshwater aquifer, potentially leading to the osmotic dehydration of crops.

What are the advantages and disadvantages of using GRACE satellites for monitoring aquifers?

Advantages: Covers large/dangerous areas quickly. Disadvantages: No physical samples or exact depth data; gravity readings can be affected by other environmental objects.

What topographic features are ideal for a reservoir?

An area with a large volume but a small surface area to minimize evaporation.

What are the environmental impacts of the sedimentation process in reservoirs?

Sedimentation causes organic matter and pollutants to sink, trapping nutrients and reducing the fertility of riverbanks downstream.

How do reservoirs create microclimates?

The large body of water buffers temperature changes due to high specific heat capacity, increases wind velocity due to low friction, and increases humidity and cloud cover through evaporation.

What is the purpose of a 'Salmon cannon'?

A device created to transport migratory species over dams so they can continue their route without injury.

What is 'grey water' and how can it be used to conserve water?

Grey water is used water that is still fairly clean (e.g., shower water) and can be recycled for tasks like watering plants or flushing toilets.

Identify the two main techniques used for desalination.

1. Distillation (heating water to evaporate it, leaving salt behind). 2. Reverse osmosis (forcing water through a partially permeable membrane at high pressure).

In water treatment, what is the purpose of adding 'flocculants'?

Flocculants neutralise the electrostatic charges on clay particles, allowing them to coagulate (clump) and sink during sedimentation.

What are three agents used to sterilise water by killing pathogens?

Ozone (oxidising agent), Chlorine (attacks cell membranes), and UV (increases genetic mutations in bacteria).