ENV100Y5 Lecture 11: Biogeochemical Cycles 1 - Module 2 Session 12
Module 2: May 22-June 1
Date: Monday, May 21
SESSION 12: SYSTEMS AND CYCLES (III)
Readings: Chapter 3
Cont’d from Module 1, Session 10:
Systems and cycles consist of interconnected reservoirs
● Reservoirs (or “pools”) - a place where material resides for a period of time in a system
or cycle - can be defined by:
○ Physical boundaries (like a “holding tank”)
■ The ocean - reservoir and a system
■ An organism - ex. Fish is a ”
■ A magma chamber under a volcano
○ Contents ( a “mass” of material)
■ Ozone in the stratosphere
■ Fish in the ocean
■ Mercury in ocean fish
● Consider a pasture system with a pesticide in several reservoirs:
○ Grass, mouse, snake, hawk
○ We can also talk about the “pesticide reservoir” in that ecosystem
Cycles can be portrayed visually, graphically, or mathematically
● Cycle is a system in which material, or energy, moves from one reservoir to another
cyclically
● When we construct a portrayal of the characteristics and functioning of a cycle or any
other environmental process, it’s called a model.
● Models of natural cycles and other processes can be:
○ Physical models - ex. Terrarium; land, water, atmosphere, plants
○ Landscape drawings
○ Box models - systematic, scientific
○ Mathematical models - quantitative, computer-based
Simple landscape drawing of the hydrologic cycle
- Atmosphere, water evaporating, sun coming down.
- Shown as a landscape drawing.
Simple box model of the hydrologic cycle
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ATMOSPHE
LA
OCE
Ri
ATMOSPHE
LA
OCE
Ri
14%
Evapo
22%
Precip
78%
Precip
86%
Evapo
- Three-reservoir model are boxes, process where by the materials are moving from one
reservoir to another are portrayed as arrows; rivers is a transfer process from land to ocean
- A fourth reservoir may be biomass - water resides in a biomass reservoir - and surface body
waters and groundwater, rivers
- What are process whereby materials moving from one to another? Evaporation & precipitation
- When looking at these cycles, you need to have them balanced. Both sides need to move
because we live in a closed system. The water moving around from land to atmosphere and
ocean to atmosphere, ultimately those all have to add up.
LAND
Cycles can be portrayed quantitatively using models
● Box models typically give quantitative information about…
○ Reservoirs (= boxes)
○ Contents (= number in the boxes) - mass/volume of material, ex. 1 kg
○ Transfer processes (= arrows) - ex. Evaporation and precipitation
○ Fluxes (= numbers on the arrows) - amount of material moving per unit of time
from one unit to another (moving along arrow)
● Box models are the first step in developing mathematical and computer models
○ Each process, flux, etc. is described by a mathematical equation
A Simple 2-reservoir example: the Sodium cycle
- Sodium moving from land to ocean and back together
- Sodium transfer from rocks, component of minerals; rock has to be weathered and river carries
sodium to the ocean
- Sea spray, waves breaking, and salty water molecules go into air - salt moves from ocean to
land; ocean into land by formation of evaporite rocks - seawater evaporated
● Not interested in details of processes, but think of everything from a system’s
perspective; ex. Rain is falling - atmosphere box, land box, and a precipitation arrow
The content of a reservoir is a function of both concentration and overall size
● Content (or burden) of a reservoir is the total mass of a substance in the reservoir
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Document Summary
Reservoirs (or pools ) - a place where material resides for a period of time in a system or cycle - can be defined by: The ocean - reservoir and a system. Consider a pasture system with a pesticide in several reservoirs: We can also talk about the pesticide reservoir in that ecosystem. Cycles can be portrayed visually, graphically, or mathematically. Cycle is a system in which material, or energy, moves from one reservoir to another cyclically. When we construct a portrayal of the characteristics and functioning of a cycle or any other environmental process, it"s called a model. Models of natural cycles and other processes can be: Three-reservoir model are boxes, process where by the materials are moving from one reservoir to another are portrayed as arrows; rivers is a transfer process from land to ocean. A fourth reservoir may be biomass - water resides in a biomass reservoir - and surface body waters and groundwater, rivers.
