SPATIAL DISTRIBUTION OF TRACE METALS IN URBAN SOILS

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SPATIAL DISTRIBUTION OF TRACE METALS IN URBAN
SOILS Howard Mielke Christopher Gonzales Kelley
Smith Xavier University of Louisiana
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BACKGROUND

• Soils reflect human activities through time.
• Trace metal content of soil is determined by past
  and present human activities
• The two biggest contributors of lead (Pb) to the
  environment are leaded paint and gasoline and
  soils serve as a repository for this metal.
• Older, larger cities usually have more Pb in soil
  than older, smaller cities. Studies of New
  Orleans, Boston, Baltimore, Minneapolis, St.
  Paul, and London, England, show that inner city
  areas have more lead pollution than outlying
  areas.
• Other metals such as Zn, Cd, Ni, and Cr seem to
  have similar spatial distributions in the soil of
  New Orleans.
• Lead is a toxic metal at relatively low
  concentrations. This is especially true for
  children under the age of five.
• Among other things, Pb has been associated with
  learning disabilities in children and its thought
  to play an important role in developing
  hypertension

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The two most important contributors of lead to
the environment are leaded paint and gasoline.
Leaded paint use peaked in the 1920s and
gradually fell off until its ban in 1978. At its
zenith in the 1970s and before its use was
restricted in 1986, leaded gasoline spewed up to
250,000 tons of lead per year into the
environment.
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OUR PROJECT

• The spatial and temporal characterization of the
  trace metals in soil (e.g. Pb in the City of New
  Orleans)
• The use of this information in primary prevention
  of exposure to metals
• This is an ongoing project which started in 1989
  for New Orleans
• Data sources
• -1990 US Census data at the tract level (TIGER
  files)
• -Soil metal concentration quantified by ICP-AES
• -Pediatric blood Pb data from the New Orleans
  Dept. of Health

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METHODOLOGY

• Sampling area New Orleans Metropolitan Area
  (NOMA), stratified by US 1990 Census tracts (286)
• Soil samples from residential areas in each tract
  (15 samples per tract 9 street side, 3 open
  spaces and 2 house drip line)
• Median soil Pb for each census tract is assigned
  to the corresponding centroid
• Interpolation using various methods including
  kriging to produce a continuous surface stored as
  a raster layer
• The raster layer is integrated with census tract
  demographic data, for analysis and graphic
  representation

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WHY USE GIS?

• Permits spatial integration of information
• Permits quick access to the information
• Allows characterization and identification of
  problem areas
• Can be used as a tool for modeling, primary
  prevention and decision-making
• The outputs of GIS are very useful for education
  and raising public awareness

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