Agriculture Reference
In-Depth Information
Figure 5.6
Spheres or layers of
influence in a system. The system
consists of interdependencies
among each layer.
Adapted from: B. R. Allenby and T. E.
Graedel,
Industrial Ecology
, Prentice
Hall, Upper Saddle River, NJ, 1995.
Social structure
(
e.g., “car” mentality: dispersed communities,
business, large parking facilities)
Infrastructure technologies
•Built (e.g., roadways)
•Supply (e.g., fuel)
•Maintenance (e.g., repair)
System
•Manufacture
•Use
•Recycle
Individual
subsystem
(e.g.,
automobile
painting)
10
−
2
, and volatile chemicals are at or above 4. The values
are limitless because they are a ratio of concentration in air and water.
10
−
4
and 4
4
×
×
Solubility
: the potential of the chemical to enter water. Very soluble chemi-
cals are on the order of 10,000 ppm and nonsoluble entities have a solubility
of less than 0.1 ppm.
Bioconcentration
: the tendency/potential of the chemical to be taken up by
biological entities (algae, fish, animals, humans, etc.). A low potential is
defined as 250 (unitless) or less, while a high potential is found at 1000 or
above.
Atmospheric oxidation
(half-life, days): helps to define the fate of the chemical
once it enters the atmosphere. A short half-life is desirable, as the chemical
will have little time to cause adverse effects. A rapid half-life would be on
the order of 2 hours or less. A slow half-life is between 1 and 10 days; longer
than 10 days is a persistent chemical.
Biodegradation
: the ability of the environment to break down the chemical.
A short biodegradation time is ideal so that the chemical does not persist.
There are two sectors of biodegradation; one is dimensionless and one has
units of time. A biodegradation factor on the order of hours is very quick,
whereas a factor on the order of years is long.
Search WWH ::
Custom Search