Site-specific risk assessment and management of point and diffuse sources - Environmental Deterioration and Contamination: Problems and their Management - page 327

is applied usually to point sources allowing for the prediction of pollutant emission
and risk at the local scale focusing on every individual pollution source.
Risk management of point source pollution takes the following aspects into
account:

- Prevention, restriction and remediation are equally applicable;

- Management of both the emitting technology and the emissions is possible;

- Local environmental quality criteria are equally applicable to production, usage

and emission of contaminating substances;

- Assessment of potential or real discharges and further transport of contaminants

can easily be done using traditional transport models;

- “In-pipe'' (preceding emission) and “end-of-pipe'' (emission) management

approaches, as well as the remediation of contaminated environment can be
applied;

- If there are plans to remediate a contaminated environment, the target concentra-

tion should be calculated in the compliance point;

- The result of the risk reduction measure can be confirmed immediately or soon

after application;

- The “polluter pays'' principle can be applied on an individual basis.

Management of point sources comprises the following steps and activities:

- Identification of the sources;

- Identification of the contaminant(s) and its/their fate properties (volatility, water

solubility, partition between phases, biodegradability, etc.) and adverse effects;

- Characterization of the site;

- Drawing of the conceptual risk model of the site at risk;

- Estimation of the emitted quantity or, alternatively, the concentration in the source

and of the volume/mass of the source;

- When the point source is no longer active, one can get a clear picture from mea-

sured concentration values by placing them spatially and in terms of time into a
retrospective model;

- Selection and designation of the compliance point (e.g. a water extraction well or

a residential area next to the source), specifying its distance from the source and
selection of the contaminant transport pathway. The compliance point(s) is (are)
one or more points or locations downstream of the source where the environmental
quality should fulfill default or site-specific criteria;

- Characterization of the environment the contaminants are transported through:

groundwater flow, soil type, permeability, sorption capacity, etc.;

- Fate and transport modeling, considering the interaction between the contaminant

and the environment in order to lower/attenuate the risk posed by the contaminant
along the transport pathway, e.g., in the groundwater by sorption onto soil solid
phase, or limitation by degradation;

- Calculation of the probable environmental concentration in the compliance point

at a certain date according to the transport and fate model. Alternatively, if the
pollution has already reached the target point, the environmental concentration
can also be measured;