Computing Impacts to Receptors

The impact to a receptor (e.g., a farmer) from being exposed to contaminants via a particular pathway (e.g., by ingesting contaminated water) is typically computed by multiplying contaminant concentrations in an environmental medium (e.g., water, soil, blood) to which the receptor is exposed by user-defined impact conversion factors.

Impacts are quantified either as an incremental cancer risk per individual per unit time, a radiation dose per unit time, or a Hazard Index (the concentration in a medium divided by a reference concentration).

The total impact to a receptor is computed as the sum of the impacts associated with each pathway through which the receptor is exposed to the contaminant (e.g., drinking water from a well, breathing dust in the atmosphere, ingesting soil).

Impact conversion factors are species- and receptor-specific and have dimensions of impact per unit concentration.

Within GoldSim, you usually compute an impact by using a Receptor element to carry out a term-by-term multiplication of the species concentration vectors from media in pathways by vectors of impact conversion factors. The result would be an impact vector. It is a vector because it contains an item for each species.

You can carry out a term-by-term multiplication of two vectors using the multiplication (*) operator:

Impact = Concentration_Vector * Impact_Conversion_Factor_Vector

Typically, the impact to a receptor will be a sum of several term-by-term vector multiplications, since the receptor is likely to interact with multiple contaminated media (e.g., water in a well, soil, dust).

Note: Once you have an impact vector, you could compute a total impact (summed over all species) by using the Sumv function. The Sumv function sums the components of a vector (producing a scalar)