Site-specific risk assessment and management of point and diffuse sources - Environmental Deterioration and Contamination: Problems and their Management - page 313

Site-specific risk assessment and
management of point and diffuse
sources
K. Gruiz, E. Vaszita & A. Clement
Department of Applied Biotechnology and Food Science,
Budapest University of Technology and Economics, Budapest, Hungary
ABSTRACT
In this chapter, the characteristics of point and diffuse pollution sources and the typical
contaminants are defined and described. The differences in the management of point
and diffuse contamination and the necessary tools are introduced. The investigation
is focused on diffuse pollution in general and specifically on diffuse pollution which
results from agriculture and mining.
1 INTRODUCTION
Environmental pollution from point and diffuse sources can be managed by a similar
approach but using different engineering tools. The first step is the identification of the
hazard and determination of whether it is due to contaminating chemical substance,
physical or biological agents. After identifying the contaminant and its source, the
transport can be modeled, provided that the medium and the environmental condi-
tions are known. The concentration of the contaminant at a given time and location
can be estimated using information on the fate and transport of the contaminants, the
velocity of their spread at a particular site, a watershed, a region or at global scale.
Comparison of the predicted environmental concentration ( PEC ) to the no-risk tar-
get concentration is the basis of risk quantification and of risk reduction measures.
The risk characterization ratio ( RCR , the ratio of the estimated to the targeted no-
risk concentration) is proportional to the probability of damage and determines the
urgency and scale of the necessary risk mitigation or reduction. The result of the trans-
port modeling i.e. the rate of spread and the size of the affected area, together with
socioeconomic characteristics (population density, land uses, land sensitivity, etc.), is
proportional to the size of the probable damage. Probability and the size of the possible
damage together can characterize environmental risk.
While the basic management approach of point and diffuse source pollution is sim-
ilar, the practical tools are very different. In terms of risk assessment point sources can
be spatially identified and delineated, if necessary removed, but diffuse sources can-
not. Diffuse pollution from many point sources or from diffusely distributed secondary
sources can be handled either as point or diffuse sources depending on the nature, dis-
persion rate and age of the pollution. Transport modeling of point sources is limited
to a relatively small area, supported by precise assessment data and relatively easy
validation possibilities. Watershed-scale or global scale transport modeling requires