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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Nakamoto and Hassler (1992) reported bioconcentration factors for the carcass and gonads of the sampled female fish. Values were 68.4 (37.6-98.8) and 6.4 (4.2-11.5), respectively. The BCF for the carcass of male fish is 74.4 (54.0-92.7).

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Aquatic bioaccumulation

A limited amount of information on Ba-bioaccumulation in available in open literature. This section of the report gives an overview of data that was compiles for different trophic levels

 

Algae

Cellular Ba-levels in algal cells have been measured in the past by several investigators, and in many cases relatively high Ba-levels were reported (Granshram et al, 2003; Fisher et al, 1991). Sternberg et al (2005), however, demonstrated in experiments with the diatomThalassiosira weiss flogiithat “cellular” barium increased proportionally with particulate Fe as Fe was added to the test medium. They concluded that the main part of the cellular/particulate Ba is not truly intracellular, but adsorbed on precipitated Fe-hydroxides associated with the cell surface. Havlik et al (1980) came to a similar conclusion when the investigated the uptake of radium and barium to three different algal speciesScenedesmus obliquus,Chlorella kessleriandAnkistrodesmus falcatus. The main conclusions of their work were that, after 15 days of exposure, the Ba-uptake by algae was 30-60% of the added amount of Ba (concentration levels of 4.0, 0.48 and 0.04 μg/L), and relative cumulation increased with decreasing exposure levels (thus indicating an inverse relationship between BCF and exposure concentration). Secondly, they reported that barium was primarily bound to the cell membrane or some other non-extractable algal component, and did not enter the building organic components of the protoplasm.

Stary et al (1984) determined accumulation factors of different radionuclides – including Ba – to the algaeScenedesmus obliquus, and found a maximum bioaccumulation factor F of 4467 (log F: 3;65). Based on the findings that maximum bioaccumulation was obtained within an hour and that the majority of elements accumulated in algae can be transferred into a solution, the authors concluded that the accumulation of the element is a physicochemical process (adsorption).

Fish

A limited amount of barium that is taken up by animals will bioaccumulate in the edible parts of the fish. According to the WHO (1990), approximately 91% of Ba found in the body is found in the bones; this uptake into the bone appears to be rapid and Ba is primarily deposited in areas of active bone growth. According to Reeves (1986), uptake of Ba by bones is 1.5 to 5 times higher than that of Ca or Sr. The remainder of Ba is found in the soft tissues (aorta, brain, heart, kidneys, spleen, pancreas, and lungs (WHO, 1990).

Nakamoto and Hassler (1992) investigated whether elements (incl. barium) accumulated in bluegills (Lepomis macochirus) affected growth and fecundity. Ba-concentrations (filtered fraction) in water samples from the Merced River and Salt Slough were 34 μg/L (range: 27-44 μg/L) and 65 μg/L (range: 56-67 μg/L), respectively, and were measured by Argon ICP-AES (detection limit: 1 μg/L).

For the male and female bluegills that were caught in the Merced River, the tissue concentration levels of Ba in carcasses were 12.9 μg/g dw (range: 9.4-16.1 μg/g dw) and 11.9 μg/g dw (range: 6.5-17.2 μg/g dw), respectively. The average internal concentration in the gonads of the bluegills from this area was more than one order of magnitude lower, i.e., 0.8 μg/g dw (range: 0.6-1.5 μg/g dw).

Similar observations were made for the fish caught at Salt Slough. Carcass concentrations levels were 18.2 μg/g dw (range: 6.3-13.6 μg/g dw) and 7.0 μg/g dw (range: 5.7-9.4 μg/g dw) for male and female organisms, respectively. Here too, gonad levels were more than one order of magnitude lower (0.4 μg/g dw; range: 0.2-0.7 μg/g dw).

Reported bioconcentration factors for the carcass and gonads of the sampled female fish were 68.4 (37.6-98.8) and 6.4 (4.2-11.5), respectively. The BCF for the carcass of male fish was 74.4 (54.0-92.7). Comparable BCF-values for the carcass were determined for different other metals (Cr, Cu, Mg, Mn, V); BCFs for these metals were less than a factor of 2 lower or higher than the Ba-BCF. For the gonads, however, the Ba-BCF was the lowest of all metals that were considered in this study.

Ba-concentration levels in the muscle tissue of another fish, the bluefin tunaThunnus thunnuswere approximately two orders of magnitude lower than the Ba-concentration in the bluegill carcasses. A Ba tissue concentration of 0.03 μg/g dry wt (range: 0.01-0.08 μg/g) was reported by Hellou et al (1992). This large difference, however, is most likely related to the fact that barium is mainly accumulated in the bones, whereas the edible part of the fish (i.e., the muscle) often show metal concentration levels that can be several orders of magnitude lower than bones or some other soft tissues (e.g., brain, heart, kidneys).

Some other authors reported Ba-levels in field-collected fish, but measured levels were only relevant for the whole-body concentration, i.e., no analysis on specific organs or tissues were conducted. Ba-levels in juvenile striped bass from the San Joaquin Valley and San Francisco area (California) ranged from 0.51 to 98 μg/g, with a geometric mean of 4.37 μg/L (n= 55, representing 22 locations) (Saiki and Palawski, 1990). This mean value is in line with the range of 4.4-12 μg/g as reported by Radtke et al (1988) for adult common carp from the Lower Colorado River Valley. Schroeder et al (1988) found similar concentrations in a mixture of common carp, mosquito fish and yellow bullheads, i.e., a range of 5.1-16 μg/g. Neither of these studies provided measured Ba-levels in the water column.

Samples of sediment and fish (slenderhead darterPercina phoxocephala, common carpCyprinus carpioand smallmouth buffaloIctiobus bubalus) were collected in 1991-1992 from the Neosho River drainage, and Ba-content was determined (Allen et al, 2001). Ba-levels in the sediment were situated between 105 and 224 mg/kg dw. Concentrations in the fish were 15-33 mg/kg dw, 9-20 mg/Kg dw and 11-22 mg/kg dw forP. phoxocephala,C. carpioandI. bubalus, respectively. The latter fish concentrations are comparable to those previously reported in this section.

Hinck et al (2008) collected bass (n=1003) and carp (n=1605) form 96 sites on major US rivers and determined metal content in whole body composite samples. Measured concentration levels, however, were expressed as wet weight and not as dry weight which makes is more difficult to compare these data with the previously reported Ba-concentration levels. Median Ba-levels in female and male bass were 0.65 and 0.61 μg/g wet weight, respectively. Significant higher median Ba-levels were found in female and male carp, i.e., 2.16 and 2.35 μg/g wet weight, respectively. 

Different concentrations of Ba, Cd, Cu, Mn, Pb, Se, V, and Zn in carp and bass may reflect differences in diet, foraging behaviour, metabolic processes, and anatomy. Bass feed primarily on fish, whereas carp forage for aquatic insects and plants in sediments. The higher trophic status of bass compared to carp typically results in bass having greater concentrations of bioaccumulative contaminants. As levels in bass, however, were lower than those in carp, barium should not be considered as a potential bioacculumative compound.

Other aquatic organisms

One of the objectives of the investigation that was conducted by Guthrie et al. (1979) was to determine the relative bioaccumulation of ten selected metals (incl. Ba) by the marine organisms comprising limited microcosms in two Texas bays. Organisms that were analysed for their Ba-content were the oysterCrassostrea virginica, the barnacleBalanus aburneus, the clamRangia cuneata, the blue crabCallinectes sapidusand the polychaeteNereissp.

Ba-concentration level in the sediment was 131.0 μg/g ww. Concentrations in organisms were 40.45, 1.50, 3.51, 1.45 and 4.70 μg/g ww for the barnacle, crab, oyster, clam and polychaete, respectively. A concentration was also given for the water fraction, but no information is provided on fraction (total/dissolved) or units.

Moreover, as no dry weight concentration levels were reported, it was not possible to determine relevant bioaccumulation factors through uptake via water and sediment.

Assuming a 80% water content in the organism, all but one dry weight concentration ranged from 7.3 to 23.5 μg/g dw (data for barnacle not included; 202.3 μg/g). Taking into account that bivalves are known to be metal bioaccumulators, these body concentrations are more or less in line with the concentration levels that were found previously for fish.

Zebra mussels below to those organisms that are known to bioconcentrate contaminants, and potential accumulation of barium was investigated by Roper et al (1996). Concentration levels of Ba in the water column and in the sediment layer (reported as dry weight, dw) were below detection limit and 38.6-99.6 mg/kg, respectively (Roper et al, 1996). When exposed to these sediments for a 34 day period, the baseline Ba-levels ofD. polymorpha(2.40 ± 1.62 mg/kg dw) significantly increased to 7.0 ± 1.62 mg/kg dw. Ba-levels in mussels from a reference site were 1.25 mg/kg dw. These data indicate a certain degree of accumulation via the food (sediment particles), but due to the lack of data on water column concentration and the different uptake routes (water and sediment) that were considered simultaneously, it is not possible to determine a BCF for this species.

As mentioned before, samples of sediment were collected in 1991-1992 from the Neosho River drainage, and Ba-content was determined (Allen et al, 2001). However, mussel samples were also taken (the monkeyfaceQuadrula metanervaand pimplebackQuadrula pustulosa) and analysed. Ba-levels in the sediment were situated between 105 and 224 mg/kg dw. Concentration levels inQ. metanervaandQ. pustulosawere 166-429 mg/K dw and 126-296 mg/kg dw, respectively. These values were significantly higher compared to the data that were generated for fish in this study (see above).

Finally, internal concentrations of barium in the egg yolks of the marine vertebrateCaretta caretta(loggerhead sea turtle) were reported by Stoneburner et al. (1980) (In: Meyers-Schöne and Walton, 1994), and were situated between 2.09 and 6.87 μg/g wet weight. As no external concentrations or dry weight values were reported, it was not possible to derive an indicative BCF with this data. Moreover, it is not clear to what extent concentration levels in yolk are relevant for overall body concentrations. Indeed, for several other metals (e.g., copper, zinc, lead), the concentrations in yolk were significantly higher compared to other fractions of the body.