Difference between revisions of "POPs in Baltic herring"
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# Find a parametric probability density function that matches the histogram best. | # Find a parametric probability density function that matches the histogram best. | ||
| − | As a result a set of parametric distributions was obtained that characterize the uncertainty in the average concentration in various fish species. | + | As a result a set of parametric distributions was obtained that characterize the uncertainty in the average dioxin concentration in various fish species. |
The parameters of these distributions are summarized below in results part. | The parameters of these distributions are summarized below in results part. | ||
| Line 48: | Line 48: | ||
|- | |- | ||
| Baltic Herring | | Baltic Herring | ||
| − | | Normal( | + | | Normal(5.4241,0.7324) |
|- | |- | ||
| Vendace(inland) | | Vendace(inland) | ||
| − | | | + | | Gamma(0.0487,18.4404) |
|- | |- | ||
| Vendace(sea) | | Vendace(sea) | ||
| − | | Normal(0. | + | | Normal(0.6021,0.1047) |
|- | |- | ||
| Whitefish(inland) | | Whitefish(inland) | ||
| − | | | + | | Gamma(0.1454,5.7237) |
|- | |- | ||
| Whitefish(sea) | | Whitefish(sea) | ||
| − | | Lognormal( | + | | Lognormal(1.0124,0.1845) |
|- | |- | ||
| Pike(inland) | | Pike(inland) | ||
| − | | Gamma(0. | + | | Gamma(0.1125,3.8263) |
|- | |- | ||
| Pike(sea) | | Pike(sea) | ||
| − | | Normal( | + | | Normal(0.9033,0.1425) |
|- | |- | ||
| Perch(inland) | | Perch(inland) | ||
| − | | | + | | Normal(0.2492,0.0518) |
|- | |- | ||
| Perch(sea) | | Perch(sea) | ||
| − | | | + | | Gamma(0.08,28.908) |
|- | |- | ||
| Atlantic Salmon | | Atlantic Salmon | ||
| − | | Normal( | + | | Normal(10.303,1.8453) |
|- | |- | ||
| Pike-perch(inland) | | Pike-perch(inland) | ||
| − | | | + | | Beta(9.2899,12.4403) |
|- | |- | ||
| Pike-perch(sea) | | Pike-perch(sea) | ||
| − | | Normal(1. | + | | Normal(1.298,0.2839) |
|} | |} | ||
Revision as of 13:49, 26 May 2009
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Contents
Scope
Concentrations of PCDD/Fs in fish describes average concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans furans (PCDD/Fs) in fish. Concentrations of sea and freshwater fish species are studied separately.
Definition
Data
Probability distributions of average concentrations of PCDD/Fs (dioxins) in various fish species were extracted from [1] where concentrations of 17 PCDD/F congeners found in different marine and freshwater fish species were collected. Average dioxin concentration was estimated by the arithmetic mean. Because of small number of measurements per species the non-parametric bootstrap procedure was used to create the probability distribution of the arithmetic mean. For fish species with n concentration measurements the procedure employed can be summarized as follows:
- Draw m samples of size n with replacement from the original sample. These samples are called bootstrap samples.
- Calculate the sample mean for each of the bootstrap samples.
- Make the density histogram of bootstrap means.
- Find a parametric probability density function that matches the histogram best.
As a result a set of parametric distributions was obtained that characterize the uncertainty in the average dioxin concentration in various fish species. The parameters of these distributions are summarized below in results part.
The number of bootstrap replicates m was chosen to be n^n or 2000 (if the numerical evaluation of all n^n samples was impossible).
Causality
Unit
pg/g fw WHO-TEQ
Formula
Result
Distributions used: Normal(mean,standard deviation) Beta(alfa,beta) Gamma(alfa,beta) Lognormal(mu,sigma)
| Fish species | Distribution(parameters) |
| Baltic Herring | Normal(5.4241,0.7324) |
| Vendace(inland) | Gamma(0.0487,18.4404) |
| Vendace(sea) | Normal(0.6021,0.1047) |
| Whitefish(inland) | Gamma(0.1454,5.7237) |
| Whitefish(sea) | Lognormal(1.0124,0.1845) |
| Pike(inland) | Gamma(0.1125,3.8263) |
| Pike(sea) | Normal(0.9033,0.1425) |
| Perch(inland) | Normal(0.2492,0.0518) |
| Perch(sea) | Gamma(0.08,28.908) |
| Atlantic Salmon | Normal(10.303,1.8453) |
| Pike-perch(inland) | Beta(9.2899,12.4403) |
| Pike-perch(sea) | Normal(1.298,0.2839) |
