Description

A contaminant study was initiated at Tijuana Slough National Wildlife Refuge in 1987, as a result of concern for pollution from a variety of potential sources. To assess the impacts of contaminants on the refuge and particularly the endangered lightfooted clapper rail, a variety of biota was collected in sample locations throughout the Tijuana River Valley. A brief summary of analytical results is given in both a narrative form below and graphictabular form attached. Results from 1987 indicated that 5 organochlorine chlorine pesticides were present in biota. DDT and its metabolites DDE were found in all samples with concentrations as high as 1.03 parts per millions ppm. This, however, is below concentration levels known to cause eggshell thinning in birds. Polycyclic aromatic hydrocarbons PAHs were only present in a few samples, and found at low levels. PCBs were not detected in any samples. 1988 results indicated a decrease in the presence of DDT 58 of samples. The maximum concentration was below any biologically significant threshold. PCBs were present but at low levels. This may have been due to an increase in the sensitivity of the analysis. PAHs were only found in a few biological samples, however, not at significant levels. A sediment sample from the storm drain off of 3rd Street in Imperial Beach did have a considerate number of PAHs including a carcinogen, Benzo a pyrene at 0.23 ppm. A significant finding from the 1988 data showed Aliphatic hydrocarbons Petroleum to be accumulating in Ghost shrimp and a clapper rail egg. Concentrations in the rail egg for NC5, NC6, NC19, and NC20 were comparable to eggs laid by a female mallard fed 2.5 oil. It is not known what the effect of this contamination is at this time. There are several possible sources of petroleum pollution in the Tijuana River Valley. Length and duration of oil exposure to biota can be determined by ratios of pristane to NC17 and phytane to NC18. High ratios 2 indicate a long term chronic expose and low ratios a short exposure acute. Ghost shrimp exhibited a high ratio, the rail egg a low ratio. Further information will be needed to assess oil exposure of biota. Sampling strategy for 1989 was based on analytical results from the previous two years. The major concern was presence of OCs particularly DDT and metabolites and Aliphatic hydrocarbons in biota. Sampling was conducted to ascertain aerial deposition, or point sources both from Mexico and U.S., within the Tijuana River watershed. Sampling was also conducted to determine the extent of OC contamination. The scope of work was expanded in 1989 to include a baseline contaminate study at the Sweetwater Marsh NWR. Seven stations were established throughout the refuge to assess if any contaminant problems exist. Because of the volume information generated trace metal analytical data are currently being analyzed using a Statgraphics computer program. Preliminary screening indicates no significant problems but addition analysis is needed for confirmation. Study design for 1990 will be based on results from 1989. Sampling in Tijuana River and Sweetwater NWR will be conducted in the spring and summer of 1990. A formal report on contaminant issues within Tijuana River or Sweetwater NWR will be written after receipt of 1990 data, expected in spring of 1991. If necessary, any significant contaminant issues will be reported sooner.

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