Identifying and Evaluating Impacts - Mining and the Environment: From Ore to Metal - page 411

is dei ned as the stressor that eventually results in a change in the receiving environment.
A receptor is the environmental component changed by the cause. An effect (or impact)
is the change in environmental conditions traceable to a cause. An exposure pathway is
dei ned as the physical, chemical, or biological course a stressor takes from the source to
the receptors of interest (e.g. organisms or human). The pathway links the cause with the
effect.
An appreciation of the Source-Pathway-Receptor (SPR) concept is helpful in identify-
ing and evaluating environmental impacts and risks. The SPR concept is illustrated in
Figure 9.4 using the bioaccumulation of trace metals in the marine environment as an exam-
ple (MSN 2005). Tailings discharged to the Java Sea are the source of impacts, and trace
metals are the cause. Both seawater and sediments are primary pathways, with benthos
and phyto-plankton being primary receptors. Following various pathways, trace metals
will move up the food chain, eventually reaching humans, the ultimate receptor in the
shown SPR model. Figure 9.4 demonstrates that Source-Pathway-Receptor models excel
in illustrating linkages between complex pathways of cause and effect, and in illustrating
where data are (and are not) available. If the exposure pathway is incomplete, the stressor
does not reach the receptor, and cannot cause an effect, or an environmental impact.
As illustrated in Figure 9.4 , Source-Pathway-Receptor concepts attempt to explain how
a stressor could impact an environmental component. They are conceptual models used to
communicate hypotheses and assumptions about how and why effects are occurring. SPR
models also indicate where different stressors may interact and where additional data col-
lection may provide useful information. SPR models vary largely in complexity, depend-
ing on the mechanisms and ecological processes involved.
Specialist advice based on experience with similar ecological habitats is necessary when
developing conceptual models, especially when complex pathways and ecological process

Specialist advice based on
experience with similar ecological
habitats is necessary when
developing conceptual models.

Primary
source

Primary
pathways

Primary
receptors

Secondary receptors

Current
dispersion

Ingestio n Ingestio n

Uptake

Sea water
column

Zoo/phyto
plankton

Fish Humans

Uptake

Tailings

Leaching

Uptake
Ingestion

Ingestion

Sediments Benthos

Burial/
Dilation FIGURE 9.4

The Source-Pathway-Receptor Model Illustrated Using
Bioaccumulation of Trace Metals in Marine Habitats

Source-Pathway-Receptor model excel in illustrating link-
ages between complex pathways of cause and effect, and in
illustrating where data are (and are not) available.
Source:
MSN 2005