Water, sediment, and biota from two streams on the Savannah River Site were sampled to study mercury (Hg) biogeochemistry. Total and methyl- Hg (MHg) concentrations were measured for all samples, ...speciation models were used to explore Hg speciation in the water, and Diffusive gradients in thin films (DGT) were applied to indicate the vertical profiles of labile Hg (DGT-Hg). Trophic position (δ15N) was estimated for biota and used to establish MHg biomagnification model. The speciation model indicated Hg methylation in the water occurred on settling particles and the most bioavailable Hg species to bacteria were complexes of inorganic Hg and labile organic ligands. Correspondingly, dissolved organic carbon concentrations were positively related to MHg concentrations in the water. In the sediment, the sharp increase of DGT-Hg around the sediment water interface underscores the importance of this interface, which determines the differences in the accumulation and generation of labile Hg among different waterbodies. The positive correlation between sediment MHg and sulfate concentrations suggested possible methylation reaction by dissimilatory sulfate reducing bacteria in the sediment. The food web magnification factors of MHg were 9.6 (95% CI: 4.0–23.4) and 4.4 (95% CI: 2.5–7.7) for the two streams established with trophic data of biofilm, invertebrates, and fish. Meanwhile, DGT-Hg concentrations in the water were positively correlated to biofilm Hg concentrations, which can be combined with the MHg biomagnification model to generate a modified biomagnification model that estimate MHg bioaccumulation with only labile Hg concentrations in the water. With this approach, Hg accumulation in abiotic and biotic environmental compartments was connected and the different bioaccumulation patterns of Hg in different waterbodies were explained with both geochemical and biological factors.
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•Mercury (Hg) methylation in the water occurred on settling particles.•Complexes of Hg(II) and labile organic ligands were most bioavailable to SRB.•Labile and bioavailable Hg was mostly generated in the sediment water interface (SWI).•The SWI determines the differences in Hg accumulation among different waterbodies.•Concentrations of biofilm-Hg and DGT-Hg in the water were positively correlated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The aquatic cooling canal system associated with a nuclear reactor built in the early 1950s received accidental releases of radiocesium (137Cs) from the reactor between 1954 and 1964, resulting in ...the dispersion of ~8.2 × 1012 Bq of 137Cs into the associated canals and ponds. The primary purpose of this study was to document concentrations of 137Cs in littoral zone fish currently occupying components of the cooling canal system, 3 canals and 2 impoundments, to determine how concentrations varied among these various components. Secondarily, we examined for potential influence of weirs within the canal system on concentrations in fish as well as the potential relationship between fish species and body size and on 137Cs concentrations in fish. We collected samples of sediment, biofilm, and fish from each component of the R-Reactor cooling system and compared 137Cs among sites and species in individual sites. Concentrations of 137Cs in sediments, biofilms and mosquitofish varied significantly among sampling areas with higher concentrations in RCAN1, a canal segment that was the closest to the reactor and received reactor effluent for a longer period than other components. Comparisons among other components of the cooling system, and species comparisons relative to presumed trophic positions and fish length were not consistent. However, littoral zone fish in the cooling canal system continue to bioaccumulate 137Cs >50 years after the original releases of contamination.
•Fish in the shallow canals and ponds of a reactor cooling system were assayed for legacy 137Cs > 50 years post-release.•All fish monitored within the cooling system had measurable levels of 137Cs.•Fish in the canal closest to the reactor, which received reactor effluent for a longer period, had the highest 137Cs levels.•There was no support for biomagnification or size effects for 137Cs accumulation, likely due to a narrow range of fish sizes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Although biomagnification of radiocesium (137Cs) has been reported in food webs, most previous research has been limited to select trophic linkages. Few studies have included a comprehensive survey ...of fauna associated with aquatic, semi-aquatic, and terrestrial habitats within a single study framework. The objectives of this study were to advance our understanding of the dynamics of 137Cs accumulation within food webs by quantifying 137Cs activity across a wide range of biota found within a contaminated canal, as well as test the hypothesis that life-stage and body size influence 137Cs bioaccumulation in select herpetofauna. With extensive sampling across multiple taxa collected from a contaminated canal system and associated floodplain on the Savannah River Site, we assessed 137Cs activity and stable nitrogen isotopes for both aquatic organisms that were restricted to the contaminated effluent canal, and semi-aquatic organisms able to move freely between the contaminated canal and the adjacent uncontaminated terrestrial habitat. We found 137Cs activity to be highly variable among species, with evidence for and against biomagnification in semi-aquatic and aquatic organisms, respectively. Furthermore, 137Cs activity decreased with life stage and body size in bullfrogs (Lithobates catesbeianus), despite post-metamorphic bullfrogs having a more carnivorous diet compared to tadpoles, while cottonmouths (Agkistrodon piscivorus) retained similar 137Cs activity regardless of their age and size. Although evidence of biomagnification has been observed in some contaminated systems, results of our study suggest the extent to which 137Cs biomagnifies within food webs is context-dependent and likely influenced by a suite of biotic and abiotic factors. Further, our data indicate sampling of a broad suite of species and environmental attributes are needed to elucidate the fate and dynamics of anthropogenic pollutants within contaminated ecosystems.
•137Cs accumulation is highly variable among species.•137Cs biomagnification is not ubiquitous, but instead system dependent.•Ontogenetic shifts in diet with life stage can influence 137Cs accumulation.•Bullfrogs decrease 137Cs activity with shift in life stage and increased body size.•Cottonmouths retain similar 137Cs activity regardless of age and size.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The global decline of amphibians is a major conservation issue. Many stressors are recognized for this decline including exposure to environmental contaminants. Mercury (Hg) is an environmental ...contaminant that bioaccumulates in wildlife and can cause a variety of negative impacts across taxa, including amphibians.
Amphiuma
and
Siren
spp. can comprise a large portion of biomass within their respective ecosystems, and thus, likely serve as important predators or prey in wetland communities. However, due to their cryptic nature, little is known about their ecology, diet, and accumulation potential. We sought to validate a nonlethal sampling method to quantify total mercury (THg) in two enigmatic species of aquatic salamanders: the two-toed amphiuma (
Amphiuma means
) and the lesser siren (
Siren intermedia
). We examined relationships between THg content in lethal (whole-body) and nonlethal (tail clip) samples. Tail clips were statistically significant predictors of whole-body THg (all
p
< 0.001), explaining 84–89% of variation in whole-body THg. Average whole-body THg (mg/kg) did not significantly differ between the two species (
p
= 0.97), and overall, they had similar whole-body THg content (
S. intermedia
= 0.330 ± 0.04,
n
= 18;
A. means
= 0.333 ± 0.07,
n
= 11). To our knowledge, these data represent the first reported Hg burdens in
A. means
and
S. intermedia
.
Plants are an important mode of transfer of contaminants from sediments into food webs. In aquatic ecosystems, contaminant uptake by macrophytes can vary by path of nutrient uptake (roots vs. ...absorption from water column). Carnivorous plants likely have additional exposure through consumption of small aquatic organisms. This study expanded on previous research suggesting that bladderworts (Genus
Utricularia
) accumulate radiocesium (
137
Cs) and examined for (1) a potential association between sediment and plant concentrations and (2) differences in
137
Cs accumulation among rooted and free floating
Utricularia
species. A strong correlation was found between average
137
Cs concentrations in all
Utricularia
species (combined) and sediments (
r
s
= 0.9,
p
= 0.0374). Among three bladderwort species at common sites,
Utricularia floridana
, the only rooted species, had higher mean
137
Cs concentrations than
Utricularia purpurea
, and
U. purpurea
had a greater mean
137
Cs concentration than
Utricularia inflata
.
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•The metal-removing constructed wetland functioned well from 2008 to 2017.•Metal (Cu, Zn) concentrations in the effluent were lower than the discharge limit.•The average metal removal ...efficiency was 64% for Cu and 70% for Zn.•Metal toxicity was reduced after wastewater being treated by the wetland.•The wetland performed with a three-stage (plateau, trough, recovery) pattern.
The H-02 wetland was constructed on the Savannah River Site (SC, USA) in 2007 to remove Cu and Zn from process and storm runoff water. Water samples were routinely collected from 2008 to 2017 in the primary discharge pipes, influent, effluent, and receiving stream. Water quality parameters were measured in situ, total and dissolved metal (Cu and Zn) concentrations were determined, and metal speciation was calculated with the Biotic Ligand Model. Generally, the H-02 wetland system functioned well during the reporting period. Alkaline waters in the pipe became neutral after running through the wetland. Total metal concentrations in the effluent were lower than the regulatory discharge limit with a removal efficiency of 63.8% (95% CI: 60.8–66.8%) for Cu and 70.5% (95% CI: 67.0–73.9%) for Zn. Reduced metal toxicity was inferred from the observed lower concentrations of free Cu2+ and Zn2+ in the effluent than that in the influent and pipe. As suggested by the higher percentage of Cu-organic matter complexes than Zn-organic matter complexes, Cu had a higher affinity for natural organic ligands than Zn. A three-stage performance pattern of a metal-removing constructed wetland was hypothesized, which includes the plateau stage, the trough stage, and the recovery stage. Further studies were needed to test this hypothesis, monitor the treatment efficiency, improve operation strategies, and ensure the long-term sustainability of H-02 wetland system.
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Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
The global decline of amphibians is a major conservation issue. Many stressors are recognized for this decline including exposure to environmental contaminants. Mercury (Hg) is an environmental ...contaminant that bioaccumulates in wildlife and can cause a variety of negative impacts across taxa, including amphibians. Amphiuma and Siren spp. can comprise a large portion of biomass within their respective ecosystems, and thus, likely serve as important predators or prey in wetland communities. However, due to their cryptic nature, little is known about their ecology, diet, and accumulation potential. Here, we sought to validate a non-lethal sampling method to quantify total mercury (THg) in two enigmatic species of aquatic salamanders: the two-toed amphiuma (Amphiuma means) and the lesser siren (Siren intermedia). We examined relationships between THg content in lethal (whole-body) and non-lethal (tail clip) samples. Tail clips were significant predictors of whole body THg (all p < 0.001), explaining 84-89% of variation in whole body THg. Average whole-body THg (mg/kg did not significantly differ between the two species (p = 0.97), and overall, they had similar whole body THg content (LESI = 0.330 ± 0.04, n = 18; AMME = 0.333 ± 0.07, n = 11). To our knowledge, these data represent the first reported Hg burdens in A. means and S. intermedia.
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