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GEOSTATS: environmental distribution question

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  • Neil Higgins
    Following on from the recent discussions on the list I have some questions on the distributional properties of pollutants. The answers will help me and may
    Message 1 of 1 , Nov 3, 1998
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      Following on from the recent discussions on the list I have some questions on
      the distributional properties of pollutants. The answers will help me and may
      possibly help to summarise some of the current discussions.

      Environmental pollutants such as heavy metals or radionuclides are often
      found to have approximately lognormal distributions (frequency of
      occurrence v. sample concentration).

      These pollutants may also show spatial correlation (e.g. a relationship
      between concentrations measured at locations 'close' to each other).

      1) Do you get a reasonable representation of the underlying distribution (eg
      lognormal) only when when random sampling at greater than the spatial
      correlation range?

      2) Is there a method of estimating the underlying distribution of pollutant (eg
      lognormal) when the sample values available are spatially correlated ?

      3) If the underlying distribution is assumed to be known (eg lognormal)
      does this place any constraints on the form of the spatial correlation?

      4) If the lognormal distribution is the result of a large number of random
      processes acting multiplicitvely (from the central limit theorem) what is the
      interpretation to put on other environmental distributions such as the weibull?

      5) There may be many different scales of spatial correlation. How will
      these combine to affect the distribution?


      Neil Higgins
      e-mail: Neil.Higgins@...
      Direct Line 44-1235 822764
      Fax 44-1235 833891
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