The distribution and speciation of mercury in the California current: Implications for mercury transport via fog to land

Coale, Kenneth H.; Heim, Wesley A.; Negrey, J.; Weiss-Penzias, P. S.; Fernandez, D.M.; Olson, A.; Chiswell, H.; Byington, A.; Bonnema, A.; Martenuk, S.; Newman, Audrey; Beebe, C.; Till, Claire P.

doi:10.1016/j.dsr2.2018.05.012

Cited by 22 publications

(42 citation statements)

References 38 publications

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“…As the advective marine fogs that comprised our sample set typically form under dark conditions, the Hg species entrained within them would be less susceptible to photoreduction processes and the corresponding shifts in odd-MIF signatures after entrainment within the cloud, suggesting most of this photoreduction process occurred in the marine environment prior to aerosol incorporation within the air masses. 3 Coastal California fogwater exhibits even-MIF signatures generally consistent with previous observations of precipitation samples, with positive Δ 200 Hg and negative Δ 204 Hg signatures [Δ 200 Hg = −0.16‰ to 0.24‰, average of 0.08 ± 0.10‰ (1SD); Δ 204 Hg = −0.31‰ to 0.32‰, average of −0.07 ± 0.19‰ (1SD)] (Figure S1). However, one sample (FRF_2014_1) exhibited even-MIF values (Δ 200 Hg = −0.16‰, and Δ 204 Hg = 0.32‰) that were greater than values typically observed in measurements of total gaseous Hg (TGM) but exhibited positive odd-MIF signatures that are inconsistent with previous observations of TGM.…”

Section: Resultssupporting

confidence: 87%

Isotopic Composition of Hg in Fogwaters of Coastal California

Washburn

Motta

Bergquist

et al. 2020

Environ. Sci. Technol. Lett.

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We present the first measurements of the isotopic composition of mercury (Hg) in fogwater, measured in samples collected across coastal California. Coastal California fogwater samples exhibit a relatively narrow range of Hg isotopic compositions {δ202Hg = −0.60‰ to 0.38‰, average of −0.10 ± 0.33‰ [one standard deviation (1SD)]; Δ199Hg = 0.04–0.75‰, average of 0.28 ± 0.17‰ (1SD); Δ200Hg = −0.16‰ to 0.24‰, average of 0.08 ± 0.10‰ (1SD)}. The isotopic composition of fogwater samples did not exhibit any spatial trends, either with distance from the Pacific Ocean coastline or with the latitude of sampling locations. The Hg isotopic composition of coastal California fogwater samples is not significantly different from that of precipitation collected across coastal California and the North Pacific, suggesting that marine-derived atmospheric Hg has a relatively homogeneous isotopic composition across the North Pacific. Fogwater samples exhibit a Δ199Hg/Δ201Hg slope of 1.03 consistent with Hg(II) photoreduction, highlighting the importance of photoreduction mechanisms in controlling the odd-MIF isotopic composition of atmospheric Hg wet deposition. Overall, the need for an improved understanding of the processes that control atmospheric Hg deposition is revealed by this data set, as such knowledge will be required to more accurately model global atmospheric Hg cycling.

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Section: Resultssupporting

confidence: 87%

Isotopic Composition of Hg in Fogwaters of Coastal California

Washburn

Motta

Bergquist

et al. 2020

Environ. Sci. Technol. Lett.

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“… Hemispheric mercury gradients in different Pacific Ocean reservoirs. The boxplots illustrate the hemispheric gradient of ( A ) atmospheric Hg 0 model estimates (nanograms ⋅ meters −3 ) extracted at tuna sampling locations (see Materials and Methods ), ( B ) observed total Hg concentrations (picomolar) in seawater ( 12 , 34 , 38 , 53 , 54 , 56 ), ( C ) observed MeHg concentrations at peak (picomolar) in seawater ( 12 , 34 , 53 – 57 ), ( D ) standardized total Hg concentrations (micrograms ⋅ grams −1 , dw) in skipjack tuna (this study), and ( E ) observed total Hg concentrations (nanograms ⋅ grams −1 , dw) in marine sediments ( 2 , 73 – 78 ). ** indicates significant differences between the northern and southern hemispheres (Kruskal–Wallis test; P < 0.01).…”

Section: Resultsmentioning

confidence: 99%

“…Measured Seawater Methylmercury Concentrations in the Pacific Ocean. Seawater MeHg data from the Pacific Ocean were compiled from the literature from both filtered and unfiltered samples (12,34,38,(53)(54)(55)(56)(57). In particular, we used the maximum total Hg and MeHg concentrations observed in the water column (picomolar) and the depth of maximum MeHg concentrations (meters).…”

Section: Methodsmentioning

confidence: 99%

Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs

Médieu

Point

Itai

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Pacific Ocean tuna is among the most-consumed seafood products but contains relatively high levels of the neurotoxin methylmercury. Limited observations suggest tuna mercury levels vary in space and time, yet the drivers are not well understood. Here, we map mercury concentrations in skipjack tuna across the Pacific Ocean and build generalized additive models to quantify the anthropogenic, ecological, and biogeochemical drivers. Skipjack mercury levels display a fivefold spatial gradient, with maximum concentrations in the northwest near Asia, intermediate values in the east, and the lowest levels in the west, southwest, and central Pacific. Large spatial differences can be explained by the depth of the seawater methylmercury peak near low-oxygen zones, leading to enhanced tuna mercury concentrations in regions where oxygen depletion is shallow. Despite this natural biogeochemical control, the mercury hotspot in tuna caught near Asia is explained by elevated atmospheric mercury concentrations and/or mercury river inputs to the coastal shelf. While we cannot ignore the legacy mercury contribution from other regions to the Pacific Ocean (e.g., North America and Europe), our results suggest that recent anthropogenic mercury release, which is currently largest in Asia, contributes directly to present-day human mercury exposure.

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“…On the central coast of California, USA, coastal marine fog varies seasonally, partially overlapping in time with coastal upwelling in the California Current. Upwelling brings elevated concentrations of methylated Hg compounds to the surface waters from deeper, low-oxygen waters and/or sediments (where anaerobic microbes are active), whereby sea-air exchange of methylated Hg compounds can be source of gaseous dimethylmercury (DMHg) and/or gaseous and particulate MMHg to the atmosphere 24,25 . Dimethyl Hg in the atmosphere is unstable and will break down into MMHg in the gas phase 26 or the aqueous phase at low pH 27 , followed by rapid adsorption onto aerosols and cloud droplets in the marine boundary layer 28 .…”

Section: Introductionmentioning

confidence: 99%

Marine fog inputs appear to increase methylmercury bioaccumulation in a coastal terrestrial food web

Weiss-Penzias

Bank

Clifford

et al. 2019

Sci Rep

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Coastal marine atmospheric fog has recently been implicated as a potential source of ocean-derived monomethylmercury (MMHg) to coastal terrestrial ecosystems through the process of sea-to-land advection of foggy air masses followed by wet deposition. This study examined whether pumas (Puma concolor) in coastal central California, USA, and their associated food web, have elevated concentrations of MMHg, which could be indicative of their habitat being in a region that is regularly inundated with marine fog. We found that adult puma fur and fur-normalized whiskers in our marine fog-influenced study region had a mean (±SE) total Hg (THg) (a convenient surrogate for MMHg) concentration of 1544 ± 151 ng g−1 (N = 94), which was three times higher (P < 0.01) than mean THg in comparable samples from inland areas of California (492 ± 119 ng g−1, N = 18). Pumas in California eat primarily black-tailed and/or mule deer (Odocoileus hemionus), and THg in deer fur from the two regions was also significantly different (coastal 28.1 ± 2.9, N = 55, vs. inland 15.5 ± 1.5 ng g−1, N = 40). We suggest that atmospheric deposition of MMHg through fog may be contributing to this pattern, as we also observed significantly higher MMHg concentrations in lace lichen (Ramalina menziesii), a deer food and a bioindicator of atmospheric deposition, at sites with the highest fog frequencies. At these ocean-facing sites, deer samples had significantly higher THg concentrations compared to those from more inland bay-facing sites. Our results suggest that fog-borne MMHg, while likely a small fraction of Hg in all atmospheric deposition, may contribute, disproportionately, to the bioaccumulation of Hg to levels that approach toxicological thresholds in at least one apex predator. As global mercury levels increase, coastal food webs may be at risk to the toxicological effects of increased methylmercury burdens.

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The distribution and speciation of mercury in the California current: Implications for mercury transport via fog to land

Cited by 22 publications

References 38 publications

Isotopic Composition of Hg in Fogwaters of Coastal California

Isotopic Composition of Hg in Fogwaters of Coastal California

Evidence that Pacific tuna mercury levels are driven by marine methylmercury production and anthropogenic inputs

Marine fog inputs appear to increase methylmercury bioaccumulation in a coastal terrestrial food web

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