5.4 Recommended Uncertainty Handling at This Point in Model Development
103
Table 5.7 (continued)
Main parameter
A: Strength of knowledge (function where it is used)
B: Belief that the value may deviate from the average assumption
(Natural variation of parameter)
C: Sensitivity of function to parameter (sensitivity index)
KOW
A Strong (EqP accepted methodology)
B Moderate
C 1.8% low
Comments/recommendations: Value calculated based on typical
components with affinity to organic carbon in sediment. Use as
implemented, can be changed, but has low impact on result
Plet (SSD-curve used) A Strong
B High to low depending on species sensitivity
C High
Comments/recommendations: Conservativity implemented by the
curve being conservatively extrapolated from the LD5-value from a
large and quality-assessed set of data (Nilsen et al. 2006). SSD curves
are accepted methodology and inherent safety factor used and can be
increased for sensitive species
THCsed (used as input
from OSCAR)
A Strong knowledge of place in ERA Acute function
B Is calculated by the OD model. SD is low within calculations in
same model, may vary a lot between inputs from different models
C High (proportional)
Comments/recommendations: THCsed calculations in OSCAR do
currently not take into consideration the grain size or TOC-content of
the substrate (these factors are used by ERA Acute to modify the
exposure in the initial calculations. No conservativity is included, but
the other factors are chosen conservatively. The calculations in
sediment in OSCAR are undergoing improvements, e.g. by possible
inclusion of marine snow
THC (WC)
A Strong knowledge of place in SSD-curve
B High uncertainty and the THC concentration is a time-averaged
concentration
C High (proportional)
Comments/recommendations: The concentration is calculated as a
time-averaged THC-value. This is a weakness in the approach. Use of
dynamic time-steps output options (e.g. proposed in the ERA Acute
Dynamic Risk Assessment incl. MIZ-proposal) could improve this.
Conservativity is applied as we currently do not have available from
OSCAR the THC-conc. in the lower WC, and therefore use the upper
layers as for compartment WC. This is conservative
N
A High strength of knowledge
B Moderate
C High (proportional)
Comments/recommendations: Use quality data on presence or
habitat area/fractions. Sampling of benthic species may lead to
uncertainties, use data that are based on accepted sampling methods
by accredited data sources
103
Table 5.7 (continued)
Main parameter
A: Strength of knowledge (function where it is used)
B: Belief that the value may deviate from the average assumption
(Natural variation of parameter)
C: Sensitivity of function to parameter (sensitivity index)
KOW
A Strong (EqP accepted methodology)
B Moderate
C 1.8% low
Comments/recommendations: Value calculated based on typical
components with affinity to organic carbon in sediment. Use as
implemented, can be changed, but has low impact on result
Plet (SSD-curve used) A Strong
B High to low depending on species sensitivity
C High
Comments/recommendations: Conservativity implemented by the
curve being conservatively extrapolated from the LD5-value from a
large and quality-assessed set of data (Nilsen et al. 2006). SSD curves
are accepted methodology and inherent safety factor used and can be
increased for sensitive species
THCsed (used as input
from OSCAR)
A Strong knowledge of place in ERA Acute function
B Is calculated by the OD model. SD is low within calculations in
same model, may vary a lot between inputs from different models
C High (proportional)
Comments/recommendations: THCsed calculations in OSCAR do
currently not take into consideration the grain size or TOC-content of
the substrate (these factors are used by ERA Acute to modify the
exposure in the initial calculations. No conservativity is included, but
the other factors are chosen conservatively. The calculations in
sediment in OSCAR are undergoing improvements, e.g. by possible
inclusion of marine snow
THC (WC)
A Strong knowledge of place in SSD-curve
B High uncertainty and the THC concentration is a time-averaged
concentration
C High (proportional)
Comments/recommendations: The concentration is calculated as a
time-averaged THC-value. This is a weakness in the approach. Use of
dynamic time-steps output options (e.g. proposed in the ERA Acute
Dynamic Risk Assessment incl. MIZ-proposal) could improve this.
Conservativity is applied as we currently do not have available from
OSCAR the THC-conc. in the lower WC, and therefore use the upper
layers as for compartment WC. This is conservative
N
A High strength of knowledge
B Moderate
C High (proportional)
Comments/recommendations: Use quality data on presence or
habitat area/fractions. Sampling of benthic species may lead to
uncertainties, use data that are based on accepted sampling methods
by accredited data sources