Fish and Wildlife Surveillance

T. M. Poston

Contaminants in fish and wildlife species that inhabit the Columbia River and Hanford Site are monitored for several reasons. Wildlife have access to areas of the Site containing radioactive contamination, and fish can be exposed to contamination in spring water entering the river along the shoreline. Fish and some wildlife species exposed to Hanford effluents might be harvested and may potentially contribute to the dose people receive. In addition, detection of radionuclides in fish and wildlife may indicate that wildlife are entering restricted contaminated areas (for example, burrowing in burial grounds) or that radioactive material is moving out of these restricted areas (for example, through blowing dust). Consequently, samples are collected at various locations annually, generally during the hunting or fishing season, for selected species (Figure 5.5.1).

Many of the operating facilities residing near nuclear facilities are buffered by natural areas, such as the ALE Reserve. These buffer zones isolate nonnomadic species on the Hanford Site (for example, rabbits) from contact with the public. Therefore, these species are not hunted. More detailed rationale for selection of specific species sampled in 1994 can be found in DOE (1991b).

When radionuclides are found in fish or wildlife, it is important to determine what fraction of those radionuclides originated at Hanford. Therefore, samples of fish and wildlife collected from distant locations unaffected by Hanford effluents (background locations) are analyzed, and results are compared to results from Hanford samples to identify any differences. Routine background sampling is conducted roughly every 5 years at locations believed to be unaffected by Hanford releases. Background data may also be collected during special studies or sampling efforts. In 1994, background concentrations were measured in carp from Vantage, pheasants from the Yakima Valley, and deer from offsite.

For each species of fish or wildlife, radionuclides are selected for analysis based on the potential for the contaminant to be found at the sampling site and the potential to accumulate in fish or wildlife (Table 5.5.1). Cesium-137 and strontium-90 have been the most frequently measured radionuclides in fish and wildlife.

Strontium is chemically similar to calcium; consequently, it accumulates in hard tissues high in calcium such as bone, antlers, and egg shells. It has a long biological half-life in hard tissue and may profile the lifetime exposure of an organism to strontium-90. However, strontium-90 in wildlife samples generally does not contribute much to human dose because it does not accumulate in edible portions of fish and wildlife. Spring water in the 100-N Area is the primary source of strontium-90 from Hanford to the Columbia River; however, the current contribution, relative to historical fallout from atmospheric weapons testing, is small (Jaquish 1993).

Cesium is particularly important because it is chemically similar to potassium and accumulates in the muscle tissue of fish and wildlife. It is more likely, therefore, to contribute to the dose received by hunters and fishers from the consumption of game and fish. It has a relatively short biological half-life and is an indicator of more recent exposure to radioactive materials. Cesium-137 is also a major constituent of historical fallout.

Fish and wildlife samples were analyzed by gamma scan to detect a number of gamma emitters (see Appendix F). However, gamma scan results for most radionuclides are not discussed below because concentrations were too low to measure or because measured concentrations were considered artifacts of low background counts. Low background counts occur at random intervals during sample counting and can produce occasional spurious results.

Other specific radiochemical analyses were performed on fish and wildlife samples to measure plutonium-238, plutonium-239,240, technetium-99, uranium-234, uranium-235, and uranium-238. These radionuclides provide an indication of contaminant levels in edible portions of fish and wildlife and are useful when estimating doses to consumers. These radionuclides are important because:

Technetium-99 is known to enter the Columbia River in shoreline seeps and springs and has a long half-life. In addition, its potential to accumulate in fish is not well-known.
Isotopes of uranium enter the Columbia River in springs near the 300 Area and have been reported at slightly elevated concentrations in soil and vegetation near the 300 Area.
Isotopes of plutonium accumulate in liver and may ultimately be deposited in bone. Liver tissue was analyzed in selected wildlife to monitor potential exposure to terrestrial contamination.

Fish Sampling

Bass, carp, and whitefish were collected from the Hanford Reach in the summer and winter of 1994. Fish are very mobile and the length of time they reside at any given sampling location is unknown. This mobility may explain why analytical results in fish are generally variable. A report on trends of radionuclide concentrations in fish was prepared in 1994 and provides detailed analysis of cesium-137 and strontium-90 in fish samples collected from 1982 through 1992 (Poston 1994). Results from all 1994 samples are listed by Bisping (1995).

Bass

Sample Collection and Analysis

Bass are sampled on alternating even years (Bisping 1994). Five bass were collected from the 100-F Slough in May 1994. The 100-F slough is located downstream of 100-N Springs and represents the largest backwater area suitable for the collection of adequate numbers of bass in the Hanford Reach. Bass were collected in May when they congregate in the sloughs to spawn, which is a behavioral characteristic that facilitates sample collection.

Muscle (fillet) samples and offal (referred to as carcass samples in past reports) samples were collected for analysis of gamma emitters and strontium-90.

Results

Cesium-137 was detected in all five fillet samples collected in 1994. The mean concentration was

(see Appendix A, Table A.11). When last sampled in 1992, the mean concentration was

. The 1994 concentrations of cesium-137 represent normal fluctuations close to the MDC of 0.02 pCi/g. Strontium-90 was not detected in any of the five fillet samples analyzed (MDC = 0.005 pCi/g).

The mean concentration of strontium-90 in bass offal was (see Appendix A, Table A.11). These results were lower than the mean concentration observed in bass offal samples collected from 1989-1993 (). There has been a general reduction in strontium-90 concentrations measured in bass offal since 1986 (Poston 1994); however, the changes in the last 5 years have been small because concentrations are very close to background levels (Figure 5.5.2).

Carp

Sample Collection and Analysis

Five carp were collected from the Columbia River between the 100-N and 100-D Areas because of the proximity of the N Springs and its release of strontium-90 to the river. Five carp were also collected near the 300 Area because of the potential releases of gamma emitting radionuclides, strontium-90, and uranium from ground-water springs along the river shoreline at the 300 Area and upstream. Additionally, carp were collected at Vantage in July 1994 to evaluate background concentrations. Muscle tissues and offal samples were analyzed.

Results

The only manmade radionuclides found in Columbia River carp were strontium-90 in offal and cesium-137 in muscle samples.

Muscle. Strontium-90 was not detected in carp muscle samples from Vantage, the 100 Areas, or the 300 Area (MDC = 0.005 pCi/g). Cesium-137 also was not routinely detected in muscle samples (see Appendix A, Table A.11); however, there were several instances of cesium-137 detected at the MDC of 0.02 pCi/g (Bisping 1995). Concentrations of both radionuclides in carp muscle are hovering at the MDC, and there is no indication of accumulation of cesium-137 above background levels in carp muscle.

Offal. Concentrations of strontium-90 in carp offal were higher in samples collected at Vantage than in samples collected at either the 100-N to 100-D Areas or the 300 Area (see Appendix A, Table A.11). The maximum observed concentration of strontium-90, , was found in an offal sample collected from the 300 Area. Concentrations of strontium-90 in offal samples from Vantage generally exceeded concentrations reported in Hanford Reach carp offal samples collected in 1994; however, the range in concentrations at each sampling area is similar.

Whitefish

Sample Collection and Analysis

Whitefish were collected because historically they have been the Columbia River sport fish that accumulated the highest radionuclide concentrations. Whitefish are currently collected from the Columbia River along the 100-N to 100-D Area shoreline and along the 300 Area shoreline. Background samples were collected in 1991 from the Kettle River, which enters the Columbia River upstream from Grande Coulee Dam. Ten whitefish samples were collected between the 100-N and 100-D Areas in August 1994, and seven whitefish samples were collected from the 300 Area in September and December 1994.

Results

Muscle. Strontium-90 was measured in one of the ten muscle samples collected between the 100-N and 100-D Areas in 1994 [

(Bisping 1995)], but was not measured in the nine muscle samples collected and analyzed from the 300 Area (MDC is 0.005 pCi/g).

Cesium-137 was measured in half of the muscle samples collected between the 100-N and 100-D Areas and in none of the samples from the 300 Area (see Appendix A, Table A.11). Concentrations over the past 6 years have remained near the minimum detectable concentration (0.02 pCi/g).

No other manmade radionuclides were detected in 1994 whitefish muscle samples (Bisping 1995).

Offal. Mean and maximum concentrations of strontium-90 in whitefish offal were higher in 1994 than for the previous 5 years. Strontium-90 was found in all offal samples analyzed (see Appendix A, Table A.11). Mean concentrations of strontium-90 in whitefish offal sampled from the Kettle River in 1991 were approximately three times those reported in 300 Area whitefish offal samples and equivalent to those found in 100 Areas whitefish offal samples in 1994. The higher background concentrations may indicate exposure to elevated levels of fallout radioactivity in that area. The Kettle River drainage generally receives more precipitation, hence potentially more fallout, than does the Hanford Site.

Clam Sampling

Asiatic clams were collected along the Columbia River shoreline downstream of the 300 Area in the summer of 1994. The soft tissues were analyzed for gamma emitters, strontium-90, uranium-234,-235, and -238. The shells were analyzed for strontium-90 only.

Results

Concentrations of radionuclides in Asiatic clams were similar to results reported in the past (Table 5.5.2 and Woodruff et al. 1992). Concentrations of cesium-137 and strontium-90 in soft tissues collect in 1990 from the 300 Area were also very close to the limits of detection (0.005 and 0.02 pCi/g, respectively). The concentration of strontium-90 in clam shell is consistent with levels reported in other hard tissues from Site wildlife (fish offal, wildlife bone, and antler samples).

Figure 5.5.1

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