Dataset Identification:
Resource Abstract:
- description: Organochlorine, trace element, and petroleum hydrocarbon contaminants were examined in sediment and biota from
the Lower Rio Grande Valley, Texas. The study was designed to monitor organochlorine contaminants and provide baseline information
on trace elements and petroleum hydrocarbons. The detection of 15 different organochlorine insecticides in a variety of environmental
compartments is indicative of the widespread agricultural development in the valley and of the persistence of the pesticides.
DDE and toxaphene residues, in particular, were elevated compared to national baseline data. This continues a trend which
has been documented in previous studies. The maximum levels of DDE and toxaphene in fish are much lower than the levels found
by White et al. (1983) in a study conducted 8 to 10 years prior to this study. The data indicates that DDE levels are gradually
declining. The geometric mean in fish was below the 1.0 ppm level recommended for the protection of aquatic life. Several
fish samples still exceeded this level, though. The levels of DDE in spiny softshell turtles, which are highly piscivorous,
exceeded the 1.0 ppm levels. The biological significance of these residues in turtles is unknown. The DDE levels in fish are
sufficient to cause some degree of eggshell thinning in fish-eating birds, but are not expected to cause bird population declines.
Toxaphene was detected in fish at levels that have been associated with reduced growth, reduced fecundity and abnormal bone
growth. Examining several years of data from station 16 of the National Contaminants Biomonitoring Program indicated that
toxaphene residues have not declined like those of DDE. This may be due to the cancellation of toxaphene by EPA which allowed
for the use of existing stocks through 1986. Four locations had some of the highest DDE and toxaphene residues in turtles
and fish: 1) Llano Grande on the Arroyo Colorado, 2) Laguna Atascosa and Cayo Atascosa before it flows into Laguna Atascosa,
3) the Rio Grande above Anzalduas Dam, and 4) the Resaca de los Cuates. Three of these four locations are bodies of water
that have been impounded. Trace elements were generally low in biota, but some fish samples had elevated chromium and copper
levels. Three fish samples exceeded the tissue level of 4.0 ppm dry weight which is considered to be an indication of chromium
contamination, and six fish samples exceeded the national baseline 85th percentile for copper. Aliphatic hydrocarbons (alkanes)
were found above detection most frequently in spiny softshell turtles, fish, blue crabs, and cotton rats. The highest alkane
residues were detected in fish. Both petroleum hydrocarbon and biogenic sources contributed to the concentrations found in
this study. The data indicates that biogenic sources were the major contributors of aliphatic hydrocarbons. PAHs were found
in five sediment samples. Two samples containing several PAHs. The sample with the highest levels was from the Turning Basin
of the Brownsville Ship Channel. The second highest level sample was from an oxbow within the city limits of Brownsville.
The levels of PAHs in sediment are comparable to areas that are considered slightly to moderately contaminated.; abstract:
Organochlorine, trace element, and petroleum hydrocarbon contaminants were examined in sediment and biota from the Lower Rio
Grande Valley, Texas. The study was designed to monitor organochlorine contaminants and provide baseline information on trace
elements and petroleum hydrocarbons. The detection of 15 different organochlorine insecticides in a variety of environmental
compartments is indicative of the widespread agricultural development in the valley and of the persistence of the pesticides.
DDE and toxaphene residues, in particular, were elevated compared to national baseline data. This continues a trend which
has been documented in previous studies. The maximum levels of DDE and toxaphene in fish are much lower than the levels found
by White et al. (1983) in a study conducted 8 to 10 years prior to this study. The data indicates that DDE levels are gradually
declining. The geometric mean in fish was below the 1.0 ppm level recommended for the protection of aquatic life. Several
fish samples still exceeded this level, though. The levels of DDE in spiny softshell turtles, which are highly piscivorous,
exceeded the 1.0 ppm levels. The biological significance of these residues in turtles is unknown. The DDE levels in fish are
sufficient to cause some degree of eggshell thinning in fish-eating birds, but are not expected to cause bird population declines.
Toxaphene was detected in fish at levels that have been associated with reduced growth, reduced fecundity and abnormal bone
growth. Examining several years of data from station 16 of the National Contaminants Biomonitoring Program indicated that
toxaphene residues have not declined like those of DDE. This may be due to the cancellation of toxaphene by EPA which allowed
for the use of existing stocks through 1986. Four locations had some of the highest DDE and toxaphene residues in turtles
and fish: 1) Llano Grande on the Arroyo Colorado, 2) Laguna Atascosa and Cayo Atascosa before it flows into Laguna Atascosa,
3) the Rio Grande above Anzalduas Dam, and 4) the Resaca de los Cuates. Three of these four locations are bodies of water
that have been impounded. Trace elements were generally low in biota, but some fish samples had elevated chromium and copper
levels. Three fish samples exceeded the tissue level of 4.0 ppm dry weight which is considered to be an indication of chromium
contamination, and six fish samples exceeded the national baseline 85th percentile for copper. Aliphatic hydrocarbons (alkanes)
were found above detection most frequently in spiny softshell turtles, fish, blue crabs, and cotton rats. The highest alkane
residues were detected in fish. Both petroleum hydrocarbon and biogenic sources contributed to the concentrations found in
this study. The data indicates that biogenic sources were the major contributors of aliphatic hydrocarbons. PAHs were found
in five sediment samples. Two samples containing several PAHs. The sample with the highest levels was from the Turning Basin
of the Brownsville Ship Channel. The second highest level sample was from an oxbow within the city limits of Brownsville.
The levels of PAHs in sediment are comparable to areas that are considered slightly to moderately contaminated.
Citation
- Title Organochlorine, Trace Element, and Petroleum Hydrocarbon Contaminants Investigation of the Lower Rio Grande Valley, Texas,
1985-1986.
-
- creation Date
2018-05-21T02:20:27.122190
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Metadata data stamp:
2018-08-06T23:06:47Z
Resource Maintenance Information
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- notes: This metadata record was generated by an xslt transformation from a dc metadata record; Transform by Stephen M. Richard, based
on a transform by Damian Ulbricht. Run on 2018-08-06T23:06:47Z
Metadata contact
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pointOfContact
- organisation Name
CINERGI Metadata catalog
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- Contact information
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- Address
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- electronic Mail Address cinergi@sdsc.edu
Metadata language
eng
Metadata character set encoding:
utf8
Metadata standard for this record:
ISO 19139 Geographic Information - Metadata - Implementation Specification
standard version:
2007
Metadata record identifier:
urn:dciso:metadataabout:072e8156-5978-42ae-bcbd-aeecf95cd906
Metadata record format is ISO19139 XML (MD_Metadata)