(4) Multi-tier database management system. The HERA model consists of three
tiers of databases: The first tier is the default database, which contains characteristic parameters of pollutants such as basic physical and chemical properties and toxicological information, and exposure parameters of the model,
such as receptor exposure, air characteristics, soil and groundwater characteristics, building characteristics, crop absorption and off-site migration. Default as
they are, the parameter values cannot be modified by users. The second tier is
the basic database that provides physical and chemical parameters of pollutants.
The basic database is located in the parameter management module of the user
interface, and subject to adjustment by users, such as parameter values and
pollutant information. The third tier is a shared database where pollutant
characteristic parameters and exposure parameters are derived from the basic
database and the default database respectively and their values can be modified
by users. During model calculations, the parameter values in the shared database are called (Fig. 4.4).
(5) Statistical analysis of pollutant data. The HERA model can perform statistical
analysis of pollutant data according to the CL: AIRE and CIEH Statistical
Guidance, including eliminating outliers and calculating sample mean, standard
deviation, and lower and upper confidence limits for pollutant means (Fig. 4.5).
Fig. 4.4 Parameter management interface
4.1 Health Risk Assessment of Typical Groundwater Contamination Sites
79
tiers of databases: The first tier is the default database, which contains characteristic parameters of pollutants such as basic physical and chemical properties and toxicological information, and exposure parameters of the model,
such as receptor exposure, air characteristics, soil and groundwater characteristics, building characteristics, crop absorption and off-site migration. Default as
they are, the parameter values cannot be modified by users. The second tier is
the basic database that provides physical and chemical parameters of pollutants.
The basic database is located in the parameter management module of the user
interface, and subject to adjustment by users, such as parameter values and
pollutant information. The third tier is a shared database where pollutant
characteristic parameters and exposure parameters are derived from the basic
database and the default database respectively and their values can be modified
by users. During model calculations, the parameter values in the shared database are called (Fig. 4.4).
(5) Statistical analysis of pollutant data. The HERA model can perform statistical
analysis of pollutant data according to the CL: AIRE and CIEH Statistical
Guidance, including eliminating outliers and calculating sample mean, standard
deviation, and lower and upper confidence limits for pollutant means (Fig. 4.5).
Fig. 4.4 Parameter management interface
4.1 Health Risk Assessment of Typical Groundwater Contamination Sites
79